FISHING BOATS OF THE WORLD : 3
Fishing Boats
of the World: 3
Edited by
JAN-OLOF TRAUNG
Published by
Fishing News (Books) Limited
Ludgate House, 1 10 Fleet Street,
London, EC4, England
FAQ 1967
The copyright in this book is vested in the Food and
Agriculture Organization of the United Nations, for
which Fishing News (Books) Ltd. acts as publisher. The
book may not be reproduced, in whole or in part, by
any method or process, without written permission
from the copyright holder. Applications for such per-
mission, with an outline of the purpose and extent of
the reproduction desired, should be addressed to: The
Director, Publications Division, Food and Agriculture
Organization of the United Nations, Via delle Tcrmc di
CaracalJa, Rome, Italy.
The views expressed in this book are those
of the contributors
Editorial Team
Associate Editor: N Fujinami
Technical: A Antunes Secretarial: A Debenham
D Fraser M Kokkinou
J Fyson H Roper
0 Gulbrandsen S Simpson
P Gurtner A Wood
H Lundberg
Style: C de Freitas
M Laing
Made and Printed in Great Britain
by The Whitefriars Press Ltd., London and Tonbridge
Contents
Page
No.
Part I — Techno-Socio-
Economic Boat
Problems
The Influence of Social and Economic Factors on
Technological Development in the Fishing
Sector R Hamlisch 33
Factors Influencing Development ... 35
Technological Change ..... 45
Promoting Fisheries Expansion in Developing
Countries ....... 49
Technical Survey of Traditional Small Fishing
Vessels N Yukoyama,
TTsuchiya, T Kohayashi, Y Kanayama
Resistance and Propulsive Characteristics.
Rolling and Stability .....
Construction ......
Examples of Actual Boats .
Methode de Projet des Nouveaux Types de Navires
de Peche . . . . E R (nwroult
Dimensions cl Caractcristiqucs Principalcs
Verification cl C'hoix Final ....
Page
No,
98
99
103
105
107
112
113
114
Topographical Factors in Fishing Boat Design
A Chidhamharum 52
Geographical and Physical Influences . . 52
Influence of Fisheries and Distance to Grounds 54
Influence of Seasonal Fisheries . . . 55
Availability of Boatbuilding Material . 55
Influence of Harbour Development . 56
Tcchno-Socio-Economic Problems Involved in the
Mechanization of Small Fishing Craft
Alsushi Takugi ami Yutaka Hirasawa 57
Mechanization of Small Fishing Craft . . 57
Locationing of Vessels and Communication . 58
Detection of Fish 59
Mechanization, Increased Catch and Resulting
Restriction on Fishing Vessels . . . 60
Lack of Labour and New Stage of Mechanization 66
Discussion ....... 69
Indigenous Craft Development . . .69
A Statistical Anal \ sis of FAQ Resistance Data for
Fishing Craft . . . /) ./ Doust.
JG Ha vex. TTsuchiya 123
Treatment of Input Data .... 123
I he Hull Form Parameters . . . .125
The Regression Equation for Resistance
( riterion CW|fi . . . . . .130
Fstimation of Performance for Particular Hull
Forms 132
Some H fleets on Resistance Criterion of Indivi-
dual Parameters. . . . . .134
New Possibilities for Improvement in the Design of
Fishing Vessels . . . JO Traitng*
DJ Domt.JG Hayes 139
Selection of Main Dimensions for Four Typical
Fishing Vessels ' .139
Optimization of Regression Equations . .140
Derivation of Particular Form Parameters . 143
Design of Forms . . . . . .143
Model Tests 14X
Stability 151
Investigation of Existing Boats . . 158
Part II — Performance
Measurements on Two Inshore Fishing Vessels
M Hatftelct 85
The Vessels 87
Instrumentation 87
Trials Procedure 90
Trials Results 92
Discussion and Observations .... 95
Direct Indicating Warp Loadmeters . . 97
Future Action 97
A Free Surface Tank as an Anti-Rolling Device for
Fishing Vessels . . J J van den Koscli
Rolling Motion According to Simplified Theory
Rectangular Tank Data .....
Example of Application
Model Experiments
Suggestions .......
Catamarans as Commercial Fishing Vessels
I- rank R Mac Lear
Advantages
History
159
159
162
164
166
169
170
170
171
[5]
Page
No.
Catamarans as Commercial Fishing Vessels— continued
Structure 171
Comfort and Motion 171
Report of Various Existing Catamarans . . 171
Summary . . . . . . .173
Discussion
Value of Full-Scale Measurement
Survey of Traditional Japanese Boats
Evaluation of Existing Designs
Computer Design of Boats
Stability and Sen Behaviour .
Catamarans and Other Unorthodox
figurations
Hydrofoil Craft and Hovercraft
The Russian Popoffkas .
Con-
175
175
176
179
179
182
190
194
195
Page
No.
Aluminium and its Use in Fishing Boats
C WLeveau 229
Weight— Strength 231
Corrosion 235
Painting 236
Costs 237
Aluminium Applications to Hull . . . 238
Aluminium Fishing Boat Applications Other than
Hull 243
Summary 245
All-Plastic Fishing Vessels . . Mitsuo Takehana 246
Special Features of Small Boats . . . 247
Need for FRP Construction . . . .247
Problems in FRP Construction . . .249
Examples 249
Future Development ..... 253
Part HI— Materials
Boatyard Facilities . . . .7 F Fyson
Design Considerations
General Building Procedures ....
Yard Layout ......
Wood-Working Machinery for Boatbuilding
Management and Planning ....
Factors in the Establishment of a Boatyard
Training of Personnel .....
Wood for Fishing Vessels . . Gunnar Pcdcrsen
Structural Factors in Fishing Boat Function
Structural Factors in Fishing Boat Form .
Specific Gravity and Strength/Stiffness Pro-
perties .......
Mechanical Properties (Structural) .
Physical Properties .....
Protection from Biological Deterioration .
Joints ........
Structural Members .....
Comparison of Strength Properties of Straight
and Curved Members
Strength Properties of Complete Structures .
Wood in Combination with Other Materials
Tentative Design Proposals ....
A 110- ft Fihreglass Reinforced Plastic Trawler
Ralph J Delia Rocca 255
256
257
Comparison of Hull Construction Materials
Craft Applications. ....
201
201
201
204
208
208
211
211
212
214
214
215
216
220
222
224
225
226
226
227
227
Materials and Moulding Methods . . . 257
Hull Construction 260
Hull Structural Designs 261
Comparison of Trawler Characteristics . . 264
Conclusions ....... 268
Comparison Between Plastic and Conventional
Boatbuilding Materials . D Verweij 270
Types of FRP 270
Principle of Comparison of Mechanical Charac-
teristics . . . . . . .271
Comparison of FRP with Steel and Light Alloy
as Regards Strength and Rigidity. . . 272
Comparison of FRP with Wood as Regards
Strength and Rigidity 272
FRP Sandwich Construction . . . .273
Influence of Weight 274
Impact 274
Fatigue 274
Corrosion Resistance 275
Durability and Maintenance .... 275
Thermal Insulation 275
Costs 275
Repairs ....... 276
Range of Length of Vessels .... 276
Building Possibilities of FRP Boats . . .276
[6]
Discussion
Boat Yard Facilities
Wood in Fishing Vessels
Fungi Attack and Decay
Aluminium and its Use in Fishing Boats
Plastic Fishing Boats
Use of Concrete ....
Comparison of Materials
Page
No.
277
277
280
288
300
306
314
315
Fire Extinguishing System ....
Auxiliary Machinery .....
Engine Controls and Instrumentation
Hydraulic Deck Machinery Frank C Vibrans, Jr.
and Kurt Brut finger
Types of Fishing Vessels ....
Power for Deck Machinery ....
Hydraulic Transmission .....
Hydraulics for Small Fishing Boats .
Page
No.
353
353
354
355
355
356
356
361
Part IV — Engineering
Technical Experiences of Mechanization of Indi-
genous Small Craft . . ER A varan 319
Main Type of Indigenous Fishing Craft . . 320
Installation of Inboard Engines . . . 320
Troubles Commonly Encountered . . . 322
Aids to Mechanization ..... 323
Outboard Engines in Coastal Fishing
E Est lander and A / ^jinami 327
Inboard Installation .... 327
Outboard Installation ..... 330
A Comparison of Outboard and Inboard
Installation .... .330
Economic Calculations ..... 332
Recommendations 332
The Location and Shape of Engine Wells in Dugout
Canoes . . . Thomas C Gillmer
and Oy vind G Mr and sen 334
Description of Models and Apparatus . . 335
Model Test Procedures 337
Experimental Results and Discussion . . 337
Refrigeration Facilities in Small Fishing Boats
Seigoro Chigusa 369
Types of Storage ...... 369
Storing Capacity by Type of Storage . . 370
Day's C;»ich, Si/c of Compartment and Capacity
of Refrigerator 370
Storing Temperature and Operating Period . 370
Special Care for Refrigerators Used for Both
Methods 371
Capacity of Refrigerator and Insulation . .371
Holds Alternatively Used for Fish then Fuel Oil 372
Arrangement in Engine Room . . . 372
Refrigerants . . . . . . .373
Automation System ..... 374
Specifications of Refrigerating Plants . . 375
Discussion 379
Mechanizing Indigenous Craft . . . 379
Outboard and Inboard Engines . . . 386
Problems with Inboard Engines . . .391
Two Engines Tried ..... 407
Hydraulic Deck Machinery .... 410
Fish Keeping on Small Craft . . .415
Engine Types and Machinery Installations
Curt Bor gens jam 345
Installed Power 345
General Requirements of Fishing Vessel Engines 346
Hot Bulb Engines 347
Diesel 347
Petrol Engines 348
Engine Bearers ...... 348
Reverse Gear 349
Reduction Gear 349
Shaft Line 349
Exhaust. System 350
Lubrication System 350
Cooling System 351
Fuel System and Tank Installation . . .352
Part V — Design of Small Boats
Developable Hull Surfaces . Ullmann Kilgore 425
Fundamental Principles ..... 425
Graphical Application of Fundamental Theorems 427
Application of Fundamentals in Construction . 430
Dugout Canoes and other Indigenous Small Craft
A J Thomas 432
Historical Background of Indigenous Small Craft 432
Disadvantages of Indigenous Small Craft . . 432
Advantages of Indigenous Small Craft . . 433
Examples of Improvements in Indigenous Small
Craft 434
7]
Page
No.
Fishing Boats for Developing Fisheries P Gunner 436
Presentation of Boat Designs .... 436
Performance . . . . . . .441
Stability 474
Weight— Cost Data 474
The Place of Boat Design in Fisheries Develop-
ment 477
Arctic Fishing Vessels and their Development
K K Rasmussen 480
Boat Development in Greenland . . . 480
Stability 489
Construction Characteristics . . . 490
Spare Parts 490
Ice Protection 490
Heating and Insulation in Accommodation . 491
Loans and Subsidies . . . . .491
Centralized Planning of Fishing Boat Develop-
ment 491
The Department Naval Architect . . .491
Start of Boat Development . . . .491
Development under Way . . . .491
Decisive Factors in Development . . . 492
Reports on Modifications .... 492
Standardization 492
The Advantages and Uses of High-Speed Fishing
Craft .... J Brandlmayr 494
Advantages ....... 494
Hull Form and Power ..... 494
Performance Data ...... 495
Construction Methods 497
Power Choice 498
Economics 499
Discussion 501
Improvements of Canoes .... 501
Need for Training Fishermen . . . . 513
Beach Landing 513
Newly Designed Small Boats . . . .521
Arctic Fishing Vessels 524
High-Speed Fishing Craft .... 525
Developable Surfaces 527
General 531
Part VI— Developments
Page
No.
Recent US Combination Fishing Vessels
Luther H Mount and Edward A Schaefers 535
Atlantic (New England) Coast Combination
Vessels 536
Gulf of Mexico Combination Vessels . . 542
Reservoir Combination Fishing Vessels . . 544
Pacific Coast Combination Vessels . . . 546
Specific Design Studies Desirable . . . 547
Recent Developments in Japanese Tuna Longliners
J kazama 550
Change of Ship Design .
Fish Hold and Refrigeration .
Propulsive Machinery
Methods to Reduce Manual Labour
Development of Japanese Stern Trawlers
Tatsuo Shimizu
Type and Size of Vessel .....
Type of Engines for Propulsion
Trawl Winch ......
Notes on General Equipment ....
300 GT Trawler
Japanese Factory Trawlers ....
Examination of Future Developments
Small Stern Trawlers. . . . W M Reid
Vessels of 25 to 49 GT without Ramp or Drum
Trawlers Fitted with Drum ....
Trawl Winches ......
Small Stern Trawlers with Ramp
Future Trends
New Trends in Stern Fishing
Design Requirements
Small Boat Designs
Fishing Equipment
Multi-Purpose Design Principles
Recent Developments .
Jan F Minnee
550
553
554
556
558
558
559
560
560
560
561
561
562
563
564
566
567
571
572
572
572
573
574
575
Discussion .....
Developments for Better Operation .
Tuna Catching ....
Japanese Stern Trawlers
Small Canadian Stern Trawlers
Combination Fishing Vessels .
Specialized Bor.iis ....
Size Restrictions ....
Page
No.
583
583
586
592
594
619
622
626
Future Developments
Submarines .
Airlift Pumps
Propulsion .
Computers .
New Boat Types .
References
Page
No.
628
631
633
633
634
635
641
[9]
List of Contributors
Page
No.
ADAM, Paul 190
Head of Fisheries Division, Agriculture Directorate, Organization
for Economic Cooperation and Development (OECD), 2 rue
Andre-Pascal, Paris 16e.
AKASAKA, Shinobu 395
President, Akasaka Ironworks Co. Ltd., No. 10, 1-Chomc, Ciinza.
Higashi, Chuo-Ku, Tokyo.
ALLI-N, Robert F . . . .301, 528, 617
Vice-President Sales, Marine Construction and Design Co.,
2300 West Commodore Way, Seattle, Wash., USA.
ANDI-KSSON, Roland 286
Master Shipwright, Ingebiick, Hisings Karra, Sweden.
ANDO, Ka/umasa 418, 586
Vice Director, Ship Building Department, Narasaki Shipbuilding
Co. Ltd., 135 Tsukiji-Machi, Muroran-shi, Hokkaido, Japan.
BARUARSON, Hjalmar R . 290,297,617,630
Naval Architect, State Director •... Shipping, PC) Box 4S4,
Reykjavik, Iceland.
BARTIIOUX, Georges 622
Direction de Travaux, Sccictariat General de la Marine Mar-
chande, 3 Place de Fontenoy, Paris 7e.
BLAUDOUX, Claude .
590
Ingenieur Constructions Navales, Ateliers ct Chant iers de la
Manche, rue Charles Bloud, Dieppe (SM), France
BHNIORD, Professor Fi . 528
Department of Naval Architecture and Marine Engineering,
University of Michigan, Ann Arbor, Mich., USA.
BIRKHOFF, Conrad .... 606,618,635
Dipl.lng., Laufgraben 37, 2000 Hamburg 13, Germany.
BJUKE, Carl G 81
Civil Engineer, Terrasgatan 13, Goteborg C, Sweden.
BLOUNT, L F . 535, 585
President, Blount Marine Corp., 461 Water Street, Warren,
RI, USA.
BONNASSIKS, Georges 632
Secretaire General, Confederation des Cooperatives Maritimes
Franchises, Caisse Central dc Credit Cooperatif, 24 av. Flochc,
Paris 8e
BORGF-NSTAM, Captain (Ling) C . . 345, 389, 409,
526, 633
Skeppsbyggnadsavdelningcn. Kungl.Marinforvaltningen, Stock-
holm 80, Sweden.
BRANDLMAYR, John 494, 527
Naval Architect, John Brandlmayr Ltd., 1089 West Broadway,
Vancouver 9, BC, Canada.
Page
No.
BRHHKVHLDT, G 401
Naval Architect, PO Box 2642, Auckland, Cl, New Zealand
BRUITING! R, K
355
Construction Supervisor, W. C. Nickum and Sons Co., Naval
Architects and Marine Engineers. 71 Columbia Street, Seattle,
Wash., USA.
BRUO-, Georg 406
Chief Fngineer, AB Seflle Motorvcrksiad. Settle, Sweden.
BRVNI-R, AM 400, 403, 405
Staff Fngineer, Marine Sales, Industrial Division, Caterpillar
Tractor Co., Peoria, 111., USA.
CAI.DIK, .ID 181
Naval Architect 2.^ Barr C'rcscent, Largs, Ayr., UK.
CAMPION, J E .
394,
Marine Supervisor, Herring Industry Board, 1 Glcntinlas Street,
Edinburgh 3, UK.
CARDOSO, Captain J F . 80, 180, 286, 593, 628, 635
Naval t.nginccr. Ministry of Marine, Rua 9 de Abril 40, S. Pedro
do Lsloril, Portugal.
CARIY, J L
513
Engineer, Fisheries Section, National Mortgage and Agency
Company of New Zealand Ltd., 57 Vogcl Street, Dunedin, CI
New Zealand.
CHAPI.LLK, Howard I
74, 190, 285
Naval Architect, Curator of Transportation, US National
Museum, Smithsonian Institution, Washington DC, USA.
CHIDMAMBARAM, K. . . . . . .52
Deputy Fisheries Development Adviser, Government of India.
Ministry of Food and Agriculture (Department of Food), New
Delhi, India.
CHIGUSA, S
369, 422
Director, Nissin Kogyo Co. Ltd., Asahi Building, 3. 3-Chomc,
Nakanoshima, Kita-Ku, Osaka, Japan.
J'o, D W
379, 511
Boatbuilding Foreman, Grade I, Ministry of Agriculture,
Fisheries Office, PO Box 226, Mwan/a, Tan/ania.
CHRISTENSEN, Hans . 524
Naval Architect, Royal Greenland Trade Department, Copen-
hagen, Denmark.
CHRIS TI-NSI-N, John 595
Naval Architect, Morgonbrisvugcn 2 1 , Uddcvalla, Sweden.
COI.VIN, THOMAS L . . 79. 279, 304, 310, 410, 528
Naval Architect, Fiddlers Green, Miles PO, Mathews Country,
Va., USA.
[11
Page
No.
176, 177, 180, 188, 594 FOSTER, J F
CORI.I-.JT, Dr. E C B .
Managing Director, Burncss, Corlctl and Partners Ltd., Naval
Architects and Marine Consultants, Worting House, Basingstoke,
Hants., UK.
CORMACK, Neil W 624
Master Shipwright, 17 Warwick Street, l.args Bay, SA, Australia.
DANIELSF.N, Birgir 72, 524, 639
Civil Engineer, Findus International SA, Case Posialc 22, Chatel-
St. -Denis, Fribourg, Switzerland.
DEU.A ROCCA, R J
255, 311
Assistant Head, Hull Design Development Section, Gibbs and
Cox Inc., 21 West Street, New York 6, NY.
DEVARA, VS 278,397,521
Superintendent, Government Fisheries Boatyard, Kakinada 2,
Andhra Pradesh, India.
Di: WIT, J G 77, 620, 627
Head, Technical Fisheries Research Department, Fisheries
Directorate, Havenkadc 19, Ijmuiden, Netherlands.
DICKSON, W 175, 595, 633
Gear Technologist, Gear Technology Section, Department of
Fisheries, FAQ, Rome, Italy.
DOUST, Dr. D J 78, 123, 139, 179, 181, 523, 590, 592, 634
Principal Scientific Officer, Ship Division, National Physical
Laboratory, Faggs Road, Fcltharn, Middx., UK now Vice
President and Technical Director, Commercial Marine
Services, Ltd., Naval Architects, 637 Craig Street West, Montreal
3, PQ, Canada.
Du CAN>:, Commander Peter
187
Deputy Chairman, Vosper Ltd., Hamilton Road, Paulsgrovc.
Portsmouth, UK.
DtJGON, J A
415
Managing Director, A. W. Smallwood Ltd., 76/84 Pomeroy Street,
New Cross, London, SHI 4.
EDDIF., Gordon C 79, 592, 634
Technical Director, While Fish Authority, Lincoln's Inn
Chambers, 2/3 Cursitor Street, London, F.C4.
ESTLANDER, Erik 327
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAQ, Rome, Italy.
FALKEMO, Professor C 1 80
Chairman, Department of Naval Architecture, Chalmers
Technical University, Goteborg S, Sweden.
FERRER, G G
380
Acting Chief, Technological Services Division, Philippine
Fisheries Commission, Manila, Philippines.
FIELD, S B
185
Engineer, John J. McMullen Associates, Consulting Naval
Architects and Marine Engineers, 1 7 Battery Place, New York 4,
NY.
Page
No.
186
Naval Architect, White Fish Authority, Industrial Development
Unit, St. Andrew's Dock, Hull, Yorks., UK.
FOUSSAT, Paul . . . 176, 185, 305, 530
Gerant, Consortium Francais de Construction Navale, BP 9,
Le Vesinet (Seine et Oisc), France.
ERASER, David J 389, 522
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAO, Rome, Italy on loan from: Ship Division, National Physical
Laboratory, Faggs Road, Feltham, Middx., UK.
FRI-CHET, Jean 79,511,584
Chief, Fishing Operations Branch, Industrial Development,
Service, Department of Fisheries of Canada, Ottawa 8, Ont
Canada.
FUJINAMI, Norio .... 327,391,422
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAO, Rome, Italy.
FYSON, John F .... 201, 280, 316
Boatbuilding Superintendent, Fishing Vessel Section, Department
of Fisheries, FAO, Rome, Italy.
GIANESI, Dolt. Ing. Gino .
Consulting Engineer, Via Cusani 10, Milan, Italy.
416
GILLMER, Professor Thomas C . . . 334, 526
Department of Marine Engineering, US Naval Academy,
Annapolis, Md., USA.
GLL-IJEN, Pierre Fils
Constructeur Naval, Audierne (Finistere), France.
619
GNANADOSS, Professor DAS. . . 74, 379
Associate Professor (Gear Technology), Central Institute of
Fisheries Education, 87-A Broach Street, Bombay 9, India.
GOODRICH, G F 186
Senior Scientific Officer, Ship Division, National Physical
Laboratory, Faggs Road, Feltham, Middx., UK.
GRIGORE, Commander Julius Jr.
193
Assistant Chief, Industrial Division, Panama Canal Company,
Box 5046, Christobal, Canal Zone.
GRONNINGSAETEK, Captain Arne.
Flyveien 13, Oslo 3, Norway.
185, 394
GUKROULT, E R . 1 12, 1 16, 179, 185, 422, 594, 619
Architecte Naval, 47 rue Maubeuge, Paris 9e.
GUICHHNL-Y, F 586
Ingenieur, Ateliers et Chantiers de la Manche, Dieppe (Seine
Maritime), France.
GULBRANDSEN, 0yvind . . . 334, 386, 518
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAO, Rome, Italy.
GURTNER, Peter . . . 388, 436, 524, 532
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAO, Rome, Italy.
12]
Page
No.
HAAVALDSEN, R 287
Toxicologist, Institute of Occupational Health, Gyclasrei 81,
Oslo 3, Norway.
ITAZAWA, Toshio
Page
No.
405
Managing Director, Kamome Propeller Co. Ltd., No. 690 Kamiy-
abe-Cho, Totsuka-Ku, Yokohama, Japan.
HAMLIN, Cyrus.
190, 305, 315 Izui, Yasukichi
411
Naval Architect, President, Ocean Research Corporation, 18,
Dane Street, Kennebunk, Me., USA.
HAMLISCH, R .
33, 81
Chief, Economic Analysis and Planning Section, Department of
Fisheries, FAO, Rome, Italy.
HAREIDE, Modolv 194, 293
Director, Norwegian Maritime Directorate, Postboks 8123, Oslo,
Norway.
HARRISON, J S M
419
Regional Representative, Industrial Development Service,
Department of Fisheries of Canada, Vancouver, BC, Canada.
HARVKY, R A .
75, 524
Director, Vessel Construction and Inspection, Department of
Fisheries, Government of Newfoundland and Labrador, St.
John's, Newfoundland, Canada.
HATFII LO, M
85, 176, 405, 410, 593
Senior Mechanical F.ngiiuc,, White I ish Authority, Industrial
Development Unit, St. Andrew's Dock, Hull, \ orks., UK.
HAYIS, J G 123, 139, 197
Principal Scientific Ofhcei, Mathematics Division, National
Physical J .aboratory, Teddington. Middx., IK.
UFA ni, R G . . . . 279, 307, 389, 502, 512
Chief, Fishing Craft Section, Department of Game and Fisheries,
PO Box 1, Chilanga, Zambia.
HlLDHWANin, Or. A G U .
77, 620
Fishery F.conomist, Head, Fisheries Department, Agricultural
Economics Research Institute, Conradkade 175, The Hague,
Netherlands.
HIKES, William S
297
Director, Fishing Vessel Construction, Department of Fisheries,
PO Box 2223, Halifax, Nova Scotia, Canada.
HlRASAWA, Y 57
TcchnicalJOfficial of Planning Section, Fisheries Agency, Ministry
of Agriculture and Forestry, Government of Japan, 2-1 Kusumi-
gaseki, Chiyoda-Ku, Tokyo.
HOEKSTRA, K 626
Fisheries Board Representative, Dumlaan 3, Urk, Netherlands.
HOGSGAARD, J 74, 379, 406, 630
Chief Engineer, Ihmdested Motorfabrik, Hundested, Denmark.
Ho v ART, P 583, 598, 619
Director, Proefstation voor Zeevisserij, Ministerie van Landbouw,
Stadhuis, Ostende, Belgium.
IN'T Vl-LD, A 293
Technical Leader, Rana Skipsbyggeri A/S, Hemnesberget,
Norway.
President, I/ui Ironworks Co. Ltd., Muroto-Machi, Kochi-Ken,
Japan.
JACKSON, Roy I 21, 80
Assistant Director-General (Fisheries), FAO, Rome, Italy.
JAMI.S, TL 314
Naval Architect. Windboats Ltd., Wroxham, Norwich, Norfolk,
UK.
JIMINI;/ m. Lucio. Captain Alberto . . 75, 80, 18J
Mitiistciio dc Marina, I ima, Peru.
Jinn, Rolf 596
Assistant Chief, Branch of Exploratory Fishing, Division of
Industrial Rcsea< xh. Bureau of Commercial Fisheries, Fish and
Wildlife Service, Washington 25 DC, USA.
KAN AY AM A, Y
98
Naval \rch«'ect. Fishing Boat Laboratory, Fisheries Agency,
Kachidoki, 5-5-1, Chuo-Ku, Tokyo.
KAZAMA, A
550
Director, Miho Shipyard Co. Ltd., Miho, Shimizu City, Shi/uoka
Pref., Japan.
lii.GORi, Ullmann . 177, 179, 181, 297, 303, 308,
400, 425, 530, 585
Nnval Architect, Marine Lngineenng and Science Company,
1111 South University Avenue, Ann Arbor, Mich., USA.
K.OBAYASIII, T. .
98
Naval Architect, Fishing Boat Laboratory, Fisheries Agency,
Kachidoki, 5-5-1. Chuo-Ku, Tokyo.
KOJIMA, Scitaro
79, 521
Chief, Fishing Boat Section, Production Division, Fisheries,
Agency, Ministry of Agriculture and Forestry, 2-1 Kasumigaseki
Chiyoda-Ku, Tokyo.
Kooi'MAN, John F 308
Naval Architect, Nutting Road, Grolon, Mass., USA.
KRISIINSSON, G L 593
President, Commercial Marine Services Ltd., Naval Architects,
637 Craig Street West, Montreal 3, PQ, Canada.
K VARAN, L-inar . . . . 76, 319, 390
Marine Engineer, Fishing Vessel Section, Department of Fisheries,
FAO, Rome now Manager, FAO/SF Deep-Sea Fishing Develop-
ment Project, PO Box 1K64, Manila, Philippines.
LEATHAKU, Dr. J F .... 175,179,303
Technical Director, Richard Dunston (Hessle), Ltd., Haven
Shipyard, Hessle, Yorks., UK.
LLL;, E C B . 79, 178, 278, 301, 307, 310, 511, 526,
530, 585
Naval Architect, Ministry of Defence (DG Ships), Foxhill, Bath,
Som., UK.
[13]
Page
No.
LENIER, Cdt. Robert .... 183,633
Pr6sident, Commission de la Marine Marchande du Syndicat des
Industries Electriques et Radioelectriques Franchises, Residence
de Becon, 4 et 6 rue Madiraa, Courbevoie (Seine), France.
LERCH, D W
410
Chief Engineer, Marine Construction and Design Co., 2300 West
Commodore Way, Seattle, Wash., USA.
LEVEAU, Carl W
229, 305
Marine Industry Manager, Kaiser Aluminum and Chemical Sales
Inc., 300 Lakeside Drive, Oakland, Calif., USA.
LINDBLOM, J 286, 305
Technical Director, O/Y l.aivateollisuus AB, Turku 15, Finland.
LlNDGREN, O 398
Engineer, AB Scania-Vabis, Sodertalje, Sweden.
LOEVINSOHN, W 395
Vice President, Deutz Diesel (Canada) Ltd., 90 Montec de Liesse,
Montreal 9, PQ, Canada.
LYON DEAN, Dr. W J
380, 584
Member, White Fish Authority, Lincoln's Inn Chambers, 2/3
Cursitor Street, I -ondon, EC4.
MACLI:AR, Frank 170, 193, 195, 302, 310, 407, 525
Naval Architect and Marine Engineer, Messrs. MacLear and
Harris, Consulting Naval Architects, 1 1 Fast 44th Street, New
York, NY.
MARGF.TTS, A R 385, 629, 632
Head, Fishing Gear Research Station, Ministry of Agriculture,
Fisheries and Food (Fisheries Laboratory), Lowestoft, Sufi'., UK.
MdNNES, A
306
Ship Surveyor, Lloyd's Register of Shipping, 71 Fenchurch Street,
London, EC3.
McKENZii;, DJ 531
Chief Surveyor of Ships, Marine Department, PO Box 2395,
Wellington, New Zealand.
MCKJNLEY, WS
PO Box 331, Del Mar, California, USA.
MCNEELY, R L
515
187,278, 305,310,380,411,
421, 526, 529, 583
Chief, Gear Research Unit, Exploratory Fishing and dear
Research Base, Bureau of Commercial Fisheries, Fish and Wildlife
Service, 2725 Montlake Boulevard, Seattle 2, Wash., USA.
MELCHERT, H .
192
Naval Architect, Maierform SA, 29/31 rue du Rhone, Geneva,
Switzerland.
MENDIS, E J H P
380
Marine Engineering Assistant, Department of Fisheries, PO Box
531, Colombo 3, Ceylon.
MICHELSEN, Professor F C
527
Department of Naval Architecture and Marine Engineering,
University of Michigan, Mich., USA.
MlNNEE, J F
Page
No.
. 572, 585,616,618,620
Naval Architect, Managing Director, N V Raadgevend Ingcnieurs-
bureau Propulsion, Leiden, Netherlands.
MONI ALVO-SACCO, Ing. Raul .... 400
Manager P1CSA Shipbuilding Av. Argentina 1650, Callao, Peru.
NADEINSKI, V 182
Head of Ship Construct ion Section, Inter-Governmental Maritime
Consultative Organization (1MCO), 22 Berners Street, London,
Wl.
NAKAJIMA, Shinichiro 410
Managing Director, Nippon Suisan Kaikai Mfr. Assoc., 4-5
Nihonbashi-Muromachi, Chuo-Ku, Tokyo.
NICKUM, George C 23, 187, 302, 303, 385, 388, 422,
628
President, W. C. Nickum and Sons Co., Naval Architects and
Marine Engineers, 71 Columbia Street, Seattle, Wash., USA.
NOEL, H S 391,406
Editor, World Fishing, The Tower, 229-243 Shepherd's Bush
Road, London, W6.
NONWI-ILLR, Professor T .
. 187
Department of Aeronautics and Fluid Mechanics, Glasgow
University, Glasgow, UK,
NORRBIN, NilsH 188, 522
Naval Architect, Chief of Division, Statens Skeppsprovning-
sanstait, Box 2400], Goteborg 24, Sweden.
O'CONNOR, J M
80, 277, 380
Advisory Services Manager, Irish Sea Fisheries Board, PO Box
275A, Dublin 4, Ireland.
OIM:RO, N 635
Fisheries Officer, Fisheries Department, Ministry of Natural
Resources and Wildlife, PO Box 30027, Nairobi, Kenya.
OGURI, Masaya 392
Chief, Diesel Engine Designing Section, Second Engineering
Department, Mitsubishi Heavy Industries Ltd., Nagoya
Machinery Works, 1 , 1-Chome, Daiko-Cho, Higashi-Ku, Nagoya,
Japan.
OHLSSON, Curt S
583
Naval Architect, Stiftelsen lor Skeppsbyggnadsteknisk Forskning,
Box 853, Goteborg 8, Sweden.
OKAMOTO, Tadatake
603
Director, Shipbuilding Division, Niigata Engineering Co. Ltd.,
No. 27-7, 2-Chome, Taito, Taito-Ku, Tokyo.
CXMhALLAIN, S
76, 391
inspector and Engineer, Fisheries Division, Department of
Agriculture and Fisheries, 3 Cathal Brugha Street, Dublin 1,
Ireland.
ORCHARD, Derek 525, 532
Fisheries Officer, Cooperative Development and Fisheries Depart-
ment, Li Po Chun Chambers, llth floor, Connaught Road C,
Hong Kong.
14]
Page
No.
PAULLING, Professor JR. . . 316, 530
Associate Professor of Naval Architecture, College of Engineering,
University of California, Berkeley 4, Calif., USA.
PAZ-ANDRADE, A 624, 639
Secretario, Jndustrias Pesqueras, Policarpo Sanz 22, Vigo, Spain.
PEDERSEN, Gunnar
211,288,291,292,293,
299, 302, 627, 631
Naval Architect, Lecturer in Naval Architecture, Helsingor
Teknikum, Helsingur, Denmark.
PETFRSFN, J 303
Naval Architect, Klintevej 2, Hojbjcrg, Denmark.
PLOSSO, J 385
Senior Fisheries Officer, Fisheries Division, Ministry of Agricul-
ture, Port of Spain, Trinidad and Tobago.
POTTER, S 280
President, Potter and McArthur Inc., Naval Architects and
Marine Engineers, 200 Summer Street, Boston, Mass., USA.
POWELL, Ronald
505
Fisheries Office, Rarotonga, Cool Islands now Fisheries Officer,
South Pacific Commission, PO Bo1-' 0, Noumea, New Caledonia.
PROHASKA, Professor l;r. C W
180
Director General, Hydro-og Aerodynamisk Laboratorium
Hjortekacrsvej W, LynpK Denmark
PROSS, Thomas 614, 628
Project Manager, Fishboat Program, Office of Ship Construction,
Maritime Administration, US Department of Commerce,
Washington DC, USA.
RANKFN, Commander M B F
415
President, Coprima-Ranken SA, Zurbano 56, 3 , Madrid 10,
Spain.
RASMUSSEN, K ... 277, 288, 480, 525
Naval Architect, Hans Rostgardsvej 5, Humleback, Denmark.
RAWLINCJS, R .
394, 521, 584
Marine Applications Engineer, Ruston and Ilornsby Ltd.,
Lincoln, Lines., UK.
RL-BOLLO, Dr. Felix .
183, 299, 308, 392
Ingeniero Inspector de Buques, Inspeccion de Buqucs Mercantes
de Vizcaya, Comandancia Militar de Marina, Bilbao, Spain.
RKID, W M . . . 277, 316, 562, 584, 617, 633
Naval Architect, Boatland Marina, Ft. Cardero Street, Vancouver
5, BC, Canada.
RFTVIG, L 293, 525
Chief Inspector of Ships, Government Ships Inspection Service,
Snorresgade J9, Copenhagen, Denmark.
RINMAN, Captain Thorsten .... 26
Editor, Swedish Shipping Gazette, Avenjen 1, Goteborg, Sweden.
ROBERTS, Captain Dennis A ... 583, 584
Director, Ross Trawlers Ltd., Fish Docks, Grimsby, Lines., UK.
Page
No.
SAINSBURY, John
175, 532
Senior Lecturer, Department of Naval Architecture and Ship-
building, College of Fisheries. Navigation, Marine Engineering
and Electronics, St. John's, Newfoundland, Canada.
SANTARFLLI, M
612
Cierente, Neot6cnica s.r.l., Calle Bolivar 391, Piso 4 , Oficina 3,
Buenos Aires, Argentina.
SAPRF. P B 379, 421, 522
Refrigeration Engineer, Directorate of Fisheries, Ahmedabad 16,
Gujarat, India
SCHAFFFRS, FA 535, 586
Chief, Branch of Exploratory Fishing, Bureau of Commercial
Fisheries, Fish and Wildlife Service, Washington 25, DC, USA.
SELMAN, George
1 76, 386, 396, 585
Naval Architect, Highlands, Stinchcombc Hill, Dursley, Glos.,
UK.
SHIMIZI .-, T 558, 616
Manager of Shipping Dept., Taiyo Fishery Co. Ltd., New
Marunouchi Bldg., 4, 1-Chomc, Marunouchi, Chiyoda-Ku,
Tokyo,
SINCLAIR, J F . . . . 293. 392, 522, 526
Chief Marine Surveyor, White Fish Authority, Lincoln's Inn
Chanbers, 2/3 Cursitor Street, London, FC4.
SMKITLM, J L 596
Naval Architect, Burness, Corlett and Partners Ltd., Naval
Architects and Marine Consultants, Worting House, Basingstoke,
Hants., UK.
SiONFMAN, J
69, 388, 501
Senior Fisheries Officer, Fisheries Department, PO Box 4,
Entebbe, Uganda.
STRANDF, Kolbjern 401
Technical Consultant, Norwegian Maritime Directorate, Oslo,
Norway.
SUTHERLAND, A . . . 290,297,393,513
Senior Technical OHiccr, White Fish Authority, Committee for
Scotland and Northern Ireland. 5 Forres Street, Edinburgh 3, UK.
SuniFRLAND, Captain Robert T Jr.
195,637
Consulting Engineer, PO Box 2466 Noble Station, Bridgeport 8,
Conn., USA.
SWINFIFLD, A N
278
Naval Architect, 61 New Street, Balgowlah, Sydney, NSW,
Australia.
TAKAGI, Professor A 57, 82, 521, 629, 633
Department of Naval Architecture, Faculty of Technology,
University of Tokyo, Bunkyo-Ku, Tokyo.
TAKLHANA, Professor Mitsuo . 190, 246, 302, 311, 526
Associate Professor, Department of Naval Architecture, Univer-
sity of Tokyo, Bunkyo-Ku, Tokyo.
THIBERGF, F 287
Ingenieur, Bureau Veritas, 31 rue Henri Rochefort, Paris 17e
[15
Page
No.
THOMAS, A J 432, 520
Director of Fisheries (Ret.), 4 Halcot Crescent, Kingston 8,
Jamaica now FAQ/ UNDP Fisheries Development Adviser, c/o
Ministry of Agriculture, Cape St. Mary, Gambia.
THOMSON, G
400
Senior Ship Surveyor, Marine Safety Branch, Board of Trade,
St. Christopher House, Southwark Street, London, SF.1.
TITO, J M
388
Sales Manager, Outboard Marine Belgium SA, 72 Pathoekeweg,
Bruges, Belgium.
TOULLEC, Jean . 302, 303, 530, 620
President, Directcur General, Chanticrs et Ateliers de la Perriere,
Lorient (Morbihan), France.
TOWNS, L D 514
President, North East Coast Boat Builders, 49 Simonburn
Avenue, Newcastle upon Tyne 4, UK.
TOWNSEND, H S
401, 523
Vice President— Research and Technical, United States Salvage
Association Inc., 99 John Street, New York, NY.
TRAUNG, Jan-Olof . 139, 182, 293, 385, 388, 391,
405, 512, 583, 584, 632
Chief, Fishing Vessel Section, Department of Fisheries, FAO,
Rome, Italy.
TROUP, K D
303, 531
Editor, Ship and Boat Builder International, The Tower, 229-243
Shepherd's Bush Road, London, W6.
TSUCHIYA, T
98, 123
Naval Architect, Fishing Vessel Section, Department of Fisheries,
FAO, Rome, on loan from: Fishing Boat Laboratory, Fisheries
Agency, Kachidoki 5-5-1, Chuo-Ku, Tokyo.
TYRRI-LL, J 181,392,522
Naval Architect, Director, John Tyrrell and Sons Ltd., Arklow,
Co. Wick., Ireland.
ULLEVALSETKR, Reidar Otto 283
Consultant, Norges Lanbrukshtfgskolc, Boks 35, Vollebckk.
Norway.
VAN DEN BOSCH, J J 159, 181, 189, 524
Naval Architect, Shipbuilding Laboratory, Technische Hoge-
school, Delft, Netherlands.
VAN DONKELAAR, Pieter 390
Chief Engineer, Outboard Marine Belgium SA, 73 Pathoekeweg,
Bruges, Belgium.
Page
No.
VI-RHOEST, J J L 598
Ingcnieur Civil des Constructions Navales, Station de Recherche
pour la Peche Maritime, Hotel de Ville, Oslende, Belgium.
VFRWI:IJ, D . 270, 277, 287, 302, 308, 310, 313,
316, 397, 529
Technical Director, Plastics Engineering Co. Ltd., KTB, PO Box
160, Amersfoort, Netherlands, now Joint Managing Director,
Holland Shipbuilding Assn. Ltd., Prins llendrikkade 149,
Amsterdam, Netherlands,
VIBRANS, F C Jr. . . . 355, 390, 391, 415
Chief Mechanical Engineer, W. C. Nickum and Sons Co., Naval
Architects and Marine Engineers, 71 Columbia Street, Seattle,
Wash., USA.
VON BRANDT, Professor Dr. A
179, 512, 629
Director, Institut fur Fangtechnik, Bundesforschungsanstalt fur
Fischerei, Palmaille 9, 2 Hamburg 50, Germany.
WANZF.R, A W
407
Chief Engineer, Murray and Tregurtha Inc., 2 Hancock Street,
Quincy, Mass., USA.
WATASE, Zenzaburo
388
Chief, Outboard Motor Division, Yamaha Motor Co. Ltd.,
PO Box Hamamatsu No. 1, 250 Nakazawa-cho, Hamamatsu,
Japan.
WATERMAN, J J
421
Industrial Liaison Officer, Torry Research Station, Ministry of
Technology, PO Box 31, Aberdeen, UK.
WHITTEMOKF:, Bruce O 300, 619
Chief Naval Architect, Marine Construction and Design Co.,
2300 West Commodore Way, Seattle, Wash., USA.
WILLIAMS, Ake 1 79
Chief Naval Architect, Statens Skeppsprovninsanstalt, Box 24001 ,
Goteborg 24, Sweden.
WINTFR, Rogers 622
Naval Architect, 911 W. College Drive, Perry, Fla., USA.
YOKOI, Dr.Eng. Motoaki .
380
Managing Director, Yanmar Diesel Engine Co. Ltd., 62 Chaya-
Machi, Kita-Ku, Osaka, Japan.
YOKOYAMA, Dr. N
98, 178, 183
Chief, Fishing Boat Laboratory, Fisheries Agency, Kachidoki-
5-5-1, Chuo-Ku, Tokyo.
ZIMMHR, Hans
Naval Architect, BMV, Bergen, Norway.
512, 524
16]
Preface
AL of us arc keenly interested in the improvement, in every significant way, of the design and
eilicicncy of small fishing vessels. Why, however, should FAG call such a meeting as the Third
FAO Technical Meeting on Fishing Boats and why should so many, more than 300 men and
women from 40 nations and from all quarters of the earth spend time and money in attending?
The Preamble of the Constitution of the Food and Agriculture Organization commits the Member
Nations to take separate and collective actions to promote the common welfare for the purpose of:
• raising levels of nutrition and standards of living of the peoples under their respective
jurisdictions;
• securing improvements in the efficiency of the production and distribution of all food and
agricultural products;
• bettering the condition of rural populations:
• and thus contributing toward an expanding world economy.
These simple phrases make our duty clear. Technical information and experience data will help in
our continuing and urgent duty to give technical assistance to the developing nations of the world.
To such nations the seas and their resources arc particularly important because they supply vital
animal protein and because they are readily and easily accessible to all.
But FAO in any given field can only muster a very few experts. In addition to bringing together
all of our own professional staff in this field, we had to augment their efforts with the services of other
experts kindly loaned to us by other co-operating organizations.
Under these circumstances, we in FAO can act only as promotors and catalysers, as stimulators of
action and a clearing house for information. The participants themselves represented by far the
greatest potential for improving the design of iishing vessels. The meeting has brought forward
experience and knowledge about new materials, new power plants, new instruments, new methods of
designing hulls and equipment which will help all of us take a long step forward in the never-ending
process of improving the tools through which we all improve our standard of living.
Through the years much attention has been given to the improvement of the design of small fishing
vessels, but much remains to be done. In spite of the present emphasis on the large and highly-
integrated distant water factory-type fishing vessels, 80 per cent of the world's catch offish comes from
grounds on or near the continental shelves. Such fishing grounds arc readily and economically fished
by small vessels based on adjacent shores. It cannot be said that there is necessarily any advantage in
having to sail half-way around the world to reach a iishing ground and half-way back again to deliver
the catch. This fact alone contributes greatly to the importance of the small fishing vessels.
We do not believe that we shall ever have a single set of standard designs for iishing vessels. The
needs of the fisheries in different parts of the world arc much too varied to make such standardization
sensible. All designs, however, must be subject to continuous study and improvement in order that
those living from the sea may progress as steadily as those living on the land.
To the Third FAO Technical Meeting on Fishing Boats came both Government delegates and
independent naval architects, boatbuilders, etc., from many parts of the world. There was free and
open discussion. In this volume there is a definite quantitative record as far as discussion presented to
our one-week technical FAO meeting is concerned. The discussion and ideas are recorded and reported
as they were made — even if condensations have had to be made.
The resulting book is not meant to be a text book of naval architecture. It, like its companions,
Fishing Boats of the World and Fishing Boats of the World: 2, deals with that part of fishing boat design
which is missing from text books on naval architecture, and it is so edited and presented that everyone
[21]
concerned with designing and building more efficient and proiitable fishing boats will find its illustra-
tions and information of practical and economic value.
It has sometimes been the practice to limit the efficiency of individual fishing vessels in order to
reduce the effectiveness of a fishing fleet and thus achieve conservation targets — for those this book is
not intended. In fact, we must always remember that conservation and efficiency are not incompatible.
We must not stifle technological progress in the name of conservation. Of course, the finite limits of
size of all stocks offish make it mandatory, sooner or later, that total fishing effort must be restricted.
However, within these limits, it is equally mandatory that the efficiency of each fishing unit should be
as high as possible. It is easier to restrict fishermen when fleets consist of efficient and profitable units
than it is when the fleets are so large and inefficient that the very economic survival of the individual
fisherman is at stake. Under such circumstances, it becomes politically most difficult to restrict the
operations of any individual.
FAO was established 20 years ago with high purposes. These purposes are more important now
and the problems hampering their achievement are more difficult, as world population increasingly
outstrips the growth of food supplies. World fishing in recent years continues to be the only major
source of food whose rate of gain in production is outstripping the rate of population growth. Although
many national and international organizations carry out excellent fundamental work in fisheries
research, conservation and development, we in FAO constitute the only truly international and world-
accessible body in the field of fisheries. The most recent General Conference of FAO Member Nations,
held in late 1965, decided to ensure that FAO in future years has the status of being the leading inter-
governmental body in encouraging rational harvesting of food from the oceans and inland waters.
It established a high-level Committee on Fisheries selected on a world-wide basis to enable us to
serve world fishery interests more capably and effectively in the future and to raise the Fisheries Division
to Department status. We now hope to be able to offer more assistance to nations in carrying out
their difficult tasks of increasing their harvests from the world ocean. At the same time we must help
to meet the common and inescapable requirements of realistic, rational fishing and conservation of
oceanic fish stocks. As we work towards these ends, we must always remember the special problems
of the imbalance of food distribution which confront the developing nations as they strive to raise their
standards of living and in particular their standards of adequate and proper nutrition.
Many of the nations most in need of more protein have abundant fish resources within a few miles
of their own shores. What we learned and what we planned at the Boat meeting will, one day, result
in more and better small fishing vessels. Those in turn can help fight hunger our greatest problem
in the years to come.
ROY I. JAC KSON
Assistant Director-General (Fisheries)
Food and Agriculture Organization
Rome,
March, 1967.
22
Note from the Chairman
IT has only been a little over ten years since the publication of Fishing Boats of the World which
followed the first KAO World Fishing Boat Congress. Most of us can remember the impact of that
volume on technologists engaged in the operation or construction of fishing vessels. Almost over-
night it became the bible of the industry and the indispensable reference work which was consulted
first in the design stages of not only fishing vessels but small vessels oi all kinds and types.
When its companion volume Fishing ttoafs of the World: 2 appeared in 1960 reporting the papers
and discussions that took place at the Second FAO World Fishing Boat Congress it took its place
alongside the first volume as a major work of reference essential to all technical libraries concerned
with the fishing and small vessel industry. It was no surprise, therefore, when over three hundred
delegates from forty nations came from all corners of I he world to attend the Third FAO
World Fishing Boal Congress in Goteborg. Knowledge of the results of the two previous Congresses,
and memories of the F-irst Co- ».Trcss, had not prepared me, however, completely for what was to take
place at this Congress.
There were Our areas in which the Congress delighted me, and which I think deserve some
comment.
The first area was the friendliness and courtesy to others shown by all of the delegates. In spite of
the barriers of language and different customs there was true communication between the delegates.
Everyone there had a common purpose which was to learn as much as they could about fishing vessels in
areas other than their own and to pass on to anyone who wanted it any information they had which
might be helpful to the other man.
It was communication at an international level at its very best, and the spirit was perhaps best
illustrated by two young, able and educated delegates one from Pakistan, and the other from India.
One evening at a reception J saw these two gentlemen come in arm in arm. With the Pakistan-Indian
conflict over Kashmir hitting all the headlines of the world's presses, I said: "It doesn't appear to
me that you arc particularly disturbed or bothered about the actions of your respective countries'*.
One of them replied: "Governments make war; not individuals".
The second thing that really amazed me was the quality of the comments, in spite of the fact that
we had to cut and to limit the amount of time each individual could take. 1 opened the meeting and
attempted to point up the need for brief and succint statements by telling the story of a native of the
State of Vermont in my country. Vermont has long had a reputation, perhaps because of its northern
location, rocky and forbidding terrain, and harsh winters, of breeding people who are extremely
independent and very taciturn- particularly in conversation with strangers.
A group of lady tourists were travelling by car around Vermont one summer when they came to a
small village which consisted primarily of a cross roads, a few scattered homes, a general store and
post oflice on the corner. The ladies stopped their car, got out, and walked up on the porch of the
country store exclaiming "How quaint!", "How charming!", etc. One of them spied an elderly man
in overalls, wearing a straw hat, sitting in a chair on the corner of the porch whittling on a piece of
wood with a knife. She went over to the old man and said: "Oh, you must be a native". "Tell me,
have you lived here all your life?" He replied: "Not yet!"
While we didn't always get comments as brief and succint as that, we did get a large number of
excellent comments and discussions condensed into very brief periods. In each day's session, which
consisted of a three-hour meeting in the morning and three hours in the afternoon, we averaged
throughout the conference over sixty speakers a day. Time after time the Chair had to cut off speakers
who obviously had much more to say. One of the great values of this publication is that here there is
room so that all of the pertinent comments of each man can be published,
[23]
The third area which was particularly evident to the man sitting in my chair was the efficient and
skilful organization work that had been done by the FAO Secretariat. The months of preparation and
the long hours put in by these gentlemen from FAO both before and during the meeting paid off.
Only by their efforts was it possible to compress the summarization of technical papers and the
comments of the delegates into five and one-half days of technical sessions.
The fourth and final area deserving specific mention was the quality of the work done by the Vice
Chairmen/Rapporteurs. As Chairman, 1 owe these gentlemen a message of praise and thanks for their
dedicated work in preparing the summary for the individual sessions and for their masterly conduct of
these meetings. These men had been in close contact with the FAO Secretariat long before the meeting
and received concurrently copies of the papers and the written contributions to the discussion. Of neces-
sity they had to read and digest alt of this to be able to prepare the 20 or 30 minute summary of the
papers and discussion presented by people who could not attend. These summaries were all master-
pieces, and only by virtue of their quality was it possible to keep the discussion on the subject at all
times. It is unfortunate that, because these summaries only covered what was in the papers or written
discussions, it is not practical to publish them in these proceedings. It should be remembered, however,
by everyone reading the very full discussion herein that this was the result of the extremely able leader-
ship of the Vice Chairmen/Rapporteurs.
In this book we now have the printed record of the Third FAO Fishing Boat Congress. I am confident
that like its predecessors it will find an honoured position in the technical literature of the world.
G. C. NICKUM
Chairman
[24]
A. C. Hardy Memorial Lecture
Cecil Hardy
Chairman of the first World Fishing
Boat Congress held in Paris 1953 and
duplicated in Miami in November of
the same year, was Commander A. C.
Hardy. He was chosen again to be
Chairman of the Second Fishing lioal
Congress held in Rome 1959.
On both occasions he made a pro-
found impression on delegates by his
Diplomatic handling of the Congresses,
his charm of manner and intense
interest and enthusiasm for the im-
provement of fishing vessels.
THE
A.C.HAROY
MEMORIAL.
After a brief illness he died in 1961. His death
was a definite loss to the fishing interests of the
world because he was an outstanding enthusiast for
the advancement of fishing activities in all areas as
a major factor for the more efficient feeding of the
world's growing populations.
Apart from his individual enthusiasm for the
industry he brought high technical qualifications to
the advancement of the industry. As a naval architect
he was keenly interested in the better application of
technical skills and scientific knowledge in the
design of fishing craft.
In addition to acting as Chairman of the first two
Congresses he made important technical contribu-
tions to both meetings and those arc on record in the
books Fishing Boats of the World: 1 and 2 covering
proceedings of those Congresses.
Because of the services rendered by Commander
Hardy in the initiation and successful conduct of
those Congresses on fishing boats, a general desire
was felt to perpetuate his memory by inaugurating a
lecture on a subject of definite interest and value to
the fishing industry, this to be given by a maritime
journalist familiar with the problems so dear to the
heart of Commander Hardy.
It was decided to ask Captain T. Rinman to
deliver this lecture. He was chosen for three reasons;
first he is of Swedish nationality and the third
Boats Congress was held in Gothenburg with the
Swedish Government as hosts; secondly he is a
maritime journalist working for the journal Swedish
Shipping Gazette (Svensk Sjofarts Tidning); thirdly,
he had been closely associated with Commander
Hardy as an apprentice in his London office studying
naval architecture.
As a memento of the occasion and a permanent
tribute, a gold medal — pictured above was presen-
ted to Captain Rinman. The donors were two
personal friends of the late Commander Hardy,
Arthur J. Heighway, Fishing News (Books) Ltd. and
Henri Kummerman of MacGregor-Comarain. In
presenting the medal to Captain Rinman, Mr.
Heighway recorded his appreciation of and admira-
tion for the work done for fishing by Cecil Hardy, as
he was popularly known to his friends.
25
While still in the engine-room, 1 would like to say
something about rationalization and/or automation of
the working procedures here. Fishermen have always
been receptive to ideas that could help them to do more
work with less manpower. The activity seen in the Mer-
chant Navy during the 1960's to mechanize or automate
various functions in the engine-room and at the same
time ensure operational reliability have already shown
good results. During the next ten years, a revolution is
likely to take place in the operation of a modern com-
mercial ship.
Perhaps to the fishing industry it docs not seem a very
important development that the crew of a mammoth
tanker may be reduced by 70 per cent or even be elimi-
nated, while the ship's 20,000 hp engines run unmanned
in an engine-room which may be locked up for 16 hours
a day. Of course this is of no immediate practical impor-
tance to a fisherman in a medium-sized boat. But what I
am trying to say is that even these highly technical
developments in the largest ships may provide hints or
clues of possible developments which will someday be
practical in the smaller fishing boats. Many items out of
the wide range of fairly inexpensive monitors and
supervisory instruments designed to suit the needs of the
Merchant Navy could probably be used in the fishing
industry for various purposes.
Hydrodynamic research and a scientific approach to
ship design have led to important improvements. The
encouragement given by FAQ in this respect is par-
ticularly welcome. Since World War II, entirely new
fishing boat hulls have been evolved in some parts of
the world. In this. Great Britain is well ahead and employs
computers and modern research methods. The Swedes,
on the other hand, use 100ft trawlers with underwater
bodies suited for 250 to 450 hp and 7 to 9 knots, but
they put 800 to 1,200 hp engines in them to gain another
3 to 5 knots. The same result could probably have been
achieved with a 600 hp engine and a new underwater
body which is just as seakindly and seaworthy as the
old one.
Extensive research has given us faster cargo ships
without increasing main engine power. We have got the
bulbous bow, new rudders and new underwater lines in
the Merchant Navy. We have got cheaper and more
suitable hull designs.
The merchant ships of today are more efficient and
less expensive than their predecessors. This means higher
earning capacity. It seems rather odd that, with few
exceptions, similar progress has not been made in fishing
boat design. This is obviously a field where FAO has an
important mission to fulfil.
There are other examples where the shipping industry
and the fishing industry have similar problems and these
examples are not always of a technical character. The
change toward bigger ships and the increasingly keen
competition has created in many parts of the world a
need to introduce changes of business organization. New
tax laws and the ever increasing need for capital arc
factors that if they do not dictate the type of business,
they at least favour certain types of companies.
In conclusion, during the past dozen years more has
been done in the shipping industry in some shipping
nations than ever before to improve technical functions
and earning capacity. I have touched on some general
tendencies. More specifically, I feel that the fishing
industry would also benefit from a close study of all the
numerous items which cost between five and five hundred
pounds which arc used in engine-rooms and on deck
aboard merchant vessels of different types.
Finally, 1 should like to stress the fact that, although I
believe my general observations are relevant, in varying
degree, to conditions in many parts of the world, specific
examples mentioned mainly refer to the situation in this
country (Sweden).
[28]
ADVERTISEMENT SECTION
A the end of this volume appears an advertisement section. This is included
because it is appreciated that practical, commercial information should he
readily available for all interested parties concerning iishing vessels, fishing
gear and equipment that can be procured from various sources for the betterment of
fishing practices.
A Jisl of advertisers arranged in major categories is as follows:
Ship & Boat Builders:
Astilleros Unidos del Pacitico, S.A.
Blount Marine Corporation
Chantiers et Ateliers de la Pcrricre
Cochrane & Sons Ltd.
Korneuburg, Shipyard A.G.
Marine Construction & Design Co.
Miho Shipyard Co. Ltd.
Miller, James N. <£ Sons
Prout, G. & Sons Ltd.
Rickmers Yv crft
Soicfamc de Ango! \ S.A.R.L
Tyrrell, John <£ Son*- Ltd.
W\k, ham, W & Co. Ltd.
Marine Engines, Gear Boxes & Sterngear:
Anglo Belgian Cy.
Cun is, W. R. Ltd.
Hundcstcd Motorfabrik, A/S
Jonkopings Motorfabrik, A.B.
Lister Blackstone Marine Ltd.
Mirrlees National Ltd.
Modern Wheel Drive Ltd.
Moteurs Buudouin
Motoren-Werkc Mannheim A.G.
Nyqvist & Holm A.B. (NOHAB)
Outboard Marine (Hvinrude)
Outboard Marine (Johnson)
Rolls-Royce Ltd.
Strojcxport, (SKODA Marine Engines)
Wichmann Molorfabrikk A/S
Zahnriiderfabrik Rcnk A.G.
Electronic, Navigation, Bridge Controls & Fish Finding Equipment :
Atlas-Elektronik Bremen (Fried. Krupp)
Bendix International Operations
Bloctube Controls Ltd.
Brown, S.G. Ltd.
Decca Navigator Co. Ltd., The
Hoppe Hans
Kelvin Hughes (a Division of Smiths Industries Ltd.)
Koden Electronics Co. Ltd.
Nuova San Giorgio S.p.a.
Simonsen Radio A/S
Taiyo Musen Co. Ltd.
[29]
Winches:
Brusselle, A., S.p.r.l., Ateliers de, Construction
Hydraulik Brattvaag, A/S
Norskov Laursen, Maskinfabrik
Nuova San Giorgio S.p.a.
Fishing Gear:
Apeldoornsc Nettenfabriek von Zeppelin & Co. N.V.
Arctic Norsenet Ltd.
Bcon Societe Anonyme des Ateliers, Le
I.C.I. Fibres Ltd.
Marine Construction & Design Co.
Marinovich Trawl Co.
Mcwes & von Eitzen, J.H.
Morishita Fishing Net Mfg. Co. Ltd.
Mustad, O. & Son
Nippon Gyomo Sengu Kaisha Ltd., The
Nuova San Giorgio S.p.a.
Refrigeration :
Frick-Barbieri, S.p.A.
"Samin", (Soc.P.Az. Macchinari impianti Frigoriferi Industrial])
Fish Pumps:
Hidrostal S.A.
Marine Construction & Design Co.
Aluminium Fish Boxes:
Bernt Iversen & S0n, A/S
Nordisk Aluminiumindustri, A/S
Liquid Fuel Heaters:
Larsen, Hans L.
Naval Architects:
Blount Marine Corporation
Kristinsson, G. E. & Dr. David J. Doust
Miscellaneous :
Fisheries Dept. FAQ
Fishing News (Books) Ltd.
Fishing News International
[30]
PART I
TECHNO-SOCIO-ECONOMIC BOAT PROBLEMS
The Influence of Social and Economic Factors on Technological Tec hno-Socio- Economic Problems Involved in the Mechani/a-
Developmcnt in the Fishing Sector . . R Hamlisch tion of Small Fishing Craft . . Atsmhi Takagi and
Yutuka Hirasawu
Topographical Factors in Fishing Boat Design Discussion
A Chidhaniharam
The Influence of Social and Economic
Factors on Technological Development
in the Fishing Sector
by R. Hamlisch
Influence des facleurs sociaux et economiqucs sur le devcloppement
tcehnologiquc de la peche
La question sc pose pour les dcssinuteurs cl construclcurs de
bateaux de peche de savoir quel concours ils scront appcles a
apporlcr a Kavenir. L'aulcur repond a cette question en analysant la
demande de bailments ncuts on pcrfectionnes. laquelle depend ellc-
memo des perspectives du marc. lie pour les produits de la peche.
Apres avoir dccrit, en cilant quclques examples, les circonstances
ayanl entrainc une expansion des pechos en divers points du globe,
I'uulcur etudie certains factcurs luimains de production: attitude
vis-a-vis du travail a hord. preferences en inatiere d'eqmpcment,
decisions relatives aux investisscments. ainsi que {'influence des
institutions et des pouvoirs publics sur le developpement tcehnolo-
gique.
Vient cnsuite un expose detaillc des conditions qi'l favori.sent ou
retardent revolution technologique di secieur halieiit:quc. La
derniere partie de la communication CluJie prhcipalernent IVncou-
ragemcnt de ('expansion de^ peches et la cadence d ". pi ogres techno-
logique hali'.'iitique dans les pays en voie de dcvcioppement.
La influencia de los fact ores economico-snciales sofore el desarrollo
tecnologico en el sector pesquero
Los arquiicctos y consiructores navales dedicados a las embar-
caciones pesqueras se mteresan en las futuras necesidades para sus
semcios. I I autor expone esas necesidades en funcion de la dc-
manda de cmbarcacion is nue\as v pcrfeccionadas, la dial deperule
a su \e/ de las perspect \as del mercado de produclos pesqueros.
Partiendo dc alpum ejcmplos, describe las circunstancias que
ban conduci<l«> a la i pansion dc la pesca en varias paries del
mundo y pa:»a despue*- cxponer los f adores de ,,insumo luimano",
en relacion con la actiiud adoptada ante cl trabajo a bordo, con
las preferencias por detcrminado equipo, las decisiones sobre
inversion y los efecios de la accion de las instituciones y el Lstado
sobre el desarrollo tecnologico.
Sigue LIU examen mas dctallado de la condiciones favorables o
r^tardatanas para la evolucion tecnologica del sector pcsquero. La
u I uma seccion del trabajo se extiende en consideracioncs sobre el
fomento di- la expansion de la pesca y el ritmo del progreso tecno-
logico en las pesquerias de los paises en desarrollo.
Ihc "market" for fishing boat architects and builders
TECHNOLOGICAL aspects, understandably, have
occupied the foreground in the fishing boat
congresses and other meetings concerned with
fishing craft and gear organ i/cd under FAO auspices.
Economic considerations came up in documentation or
discussions usually only in context with construction
costs, although one paper submitted to the First Fishing
Boat Congress in J953 also included a discussion of
other factors aflecting fishing vessel design (Beevcr, 1955).
The purpose of this paper is to look at factors other
than those relating to technology and nature (i.e.,
fishery resources, oceanography, climate, etc.) through
a wider lens. The fishing boat builder and architect have
an interest in these factors, since they play an important
part in determining future needs for their services.
The young man who is considering a career as fishing
boat architect or builder wants to know something
about the market for specialists in the profession since
his earning capacity will depend not only on his pro-
fessional competence but on supply and demand condi-
tions in this market.
On the supply side, the number of competitors the
prospective naval architect or boat builder has in his
field will be limited by the availability of training facili-
ties. More specifically, the number of naval architects
and boat builders available for work on fishing boat
design and construction will fluctuate with the oscilla-
tions in the market for fishing versus other craft.
The demand for boat builders and architects is a
function of the demand for new and improved fishing
craft and thus, ultimately, of the market for fishery
products.
Dissemination of technological knowledge
Scientists and technologists often tend to discount the
importance of demand factors. They feel that increased
catches could be marketed without difficulty, as long as
promotional activities are not altogether neglected. The
real problem, in their estimation, is to produce enough
fish to feed the rapidly expanding population of the
world; the biggest obstacle is human ignorance and
slowness of dissemination of technical knowledge. Lack
of money and neglect of extension work is admitted to
play a part (Traung, 1960).
Is this thesis valid? In 1946, some leading atomic
scientists estimated that it would take the USSR a
minimum of ten to fifteen years (after coming into
possession of atomic secrets) to "solve technological and
organizational problems'* before it would be able to
explode its first bomb. Other examples along this line
could be cited. Scientific and technical news spread
rapidly nowadays (thanks to the existence of a good
technical press and the continuous expansion of mass-
communication media) and the laboratory and engineer-
33
ing people arc perhaps the world's most closely-knit
group. Even administrators are not as unaware of
technological development — nor as callous in considering
the needs of progress — as they are made out to be by
the more impatient members of the fraternity of scientists
and technologists.
The danger of equating animal protein food requirements
with effective demand for fishery products
It is a fallacy to believe that a worsening world
food situation will translate itself automatically into
increased effective demand for food or for fish, in par-
ticular. If nutritional needs were the only guiding
criteria for fisheries development, many a developing
country with only a small stretch of sea coast could be
expected to emulate the USSR's and Japan's example in
outfitting large scale factory ship operations to roam the
oceans for fish. There is nothing so very secret about the
technical aspects of these operations, and any country is
free to participate in the exploitation of common property
ocean resources. Some developing countries have shown
considerable skill in obtaining finances from foreign
sources for (not always strictly economic) large-scale
development, and others might be similarly successful
if sufficient motivation for developing fisheries existed.
Political boundaries, then, and differences between
countries in regard to needs as well as resources available
for production of fishery and other food products,
make it impossible to project world markets on the basis
of anticipated nutritional needs, calculated from popula-
tion growth rates.
Extent and direction of development reflect specific
local, physical and economic conditions. This holds also
for the adoption of techniques. Similar fishing techniques
are often being used, one observer notes, in areas which,
until recently, lacked much contact in fishing matters,
but where conditions otherwise resembled each other
(Morgan, 1956).
A few examples of how major development has come about
Fishing and hunting are man's oldest occupations. As
cultivation of agricultural land expanded, fishing
survived mainly in areas where short summers, scarcity
or poor quality of soil, and absence of communications to
internal markets, gave it a comparative advantage over
farming. Fisheries in these areas remained at the sub-
sistence level until international trade opportunities
enabled the fishermen of such countries as Norway,
Iceland, Newfoundland, Alaska, and British Columbia
to export their surplus fish (Morgan, 1956).
The advances made by some countries in fishery
development in recent decades can, for the most part, be
traced to specific factors in domestic or foreign markets
or to changes in physical and financial resources available
for fisheries operations. Similar explanations can be
found for the decline of fisheries elsewhere.
Development in other sectors of the economy, under
some circumstances, has stimulated development of
fisheries and, under other circumstances, has made
people leave the industry. The decline in the fishery of
one country may contribute to the growth of a fishery
in another country.
The fisheries of a country may go through cycles with
marked ups and downs. Newfoundland's fisheries were
its pre-eminent industry until the turn of the century
when the economy began to diversify. The depression of
the 1930's had a disastrous effect on fish prices. The
industry was able to recover its one-time leading position
during the Second World War but suffered a severe set-
back when Newfoundland united with Canada in 1949 and
the United Kingdom market was lost. A moderate
increase in the number of fishermen after 1956 was
interpreted by some as a sign of reviving prosperity
but, according to others, merely reflected a general lack
of employment opportunities in the economy of the
Province. The difficulties of the fisheries of Newfound-
land have been blamed on developments in the foreign
markets for its cod production and on the expansion of
fishing operations of competing countries. In addition,
technical retardation due to lack of financial backing and
managerial enterprise are cited as causes (Copes, 1961).
Market factors played an important role in the sensa-
tional rise of Peruvian fisheries. Also, the lifting of
government restrictions on the fishing of the anchoveta
resources (protected until a few years ago for the sake
of the guano industry) made it possible to supply fish
meal to a rapidly growing feed compounding industry
in North America and Western Europe.
South Africa was able to carve out for herself a good
share of the fish meal market, among other reasons,
because it had acquired a large part of the equipment
utilized until the J95(Vs in the Pacific Coast pilchard
industry, after the disappearance of the fish off the coast
of California.
On occasion, development of a new type of fishery is at
the expense of another, traditional, fishery which cannot
compete on even terms, be it in respect of economic
returns to the entrepreneur or in terms of attractions to
the labour force. The introduction of deep sea cutters in
Poland, thus, led to a geographic concentration of the
sea fishery "industry. The younger fishermen left the
coastal fishing villages for work on the cutters where their
earning prospects were considerably better (Ropclewski,
1962).
The countries with centrally planned economies
favour fisheries over livestock development in their
food production industries because a given quantity of
annual protein can be produced from a smaller bundle of
inputs. Market demand is being given growing considera-
tion but the governments still reserve themselves the right
to fix price relationships in accordance with overall
policy criteria. The countries with centrally planned
economies, therefore, may want to push development of
large scale fishing to the point where marginal input
productivity in fisheries is reduced to the level of marginal
input productivity in agriculture.
In the non-socialist countries, price competition from
meat and other animal protein products places limits on
private investment. Development in the fishing sector of
the economy, consequently, is not likely to be carried as
far as in the centrally planned economies, even when
public subsidies are provided by government (FAO/UN,
1965).
Developments in other sectors of the economy, which
34]
characteristically have promoted fisheries expansion, are
those related to the creation of new industries or markets.
South-east Alaska and northern British Columbia
benefited substantially as the result of the first great gold
rush. The fishermen were no longer exclusively dependent
on the canned salmon market; fresh and lightly salted
products could be sold and new fisheries, such as those
for halibut and herring, could be established (Bartz, 1942).
Sales of dried fish for the rations of miners in the Congo
Coppcrbelt provided much of the impetus to fishery
development in the African lakes. More recently, the
discovery of rich iron ore resources in Mauritania, and
the construction of an ore port at Port Etienne, have
had a part in stimulating interest in the establishment of a
fishing port as an adjunct.
Growth in other sectors of industry will be detrimental
to fisheries if it (a) creates alternative economic oppor-
tunities which are more attractive, or (b) threatens the
resource and/or land base for fishing operations. Good
road communications, and a consequent development
of the tourist trade, for instance, were blamed for having
almost killed oil fisheries in many of the coastal cities of
Oregon which at one time were exclusively dependent on
the industry (Bartz, 1942). Industrial pollution and new
uses of water for other than fishery purposes have been,
for a long time already, among the greatest problems of
inland fisheries. Lately, the same problems have been
given growing attention also by marine biologists, as the
result of oil-shore oil and of atomic industn development.
Fisheries expansion has been indirectly siimulatcd by
decline in another sector of ihc economy. This has been
the case, for instance, in Chile, where the slump in the
nitrate industry led to increased interest in the exploita-
tion of fishery development possibilities.
FACTORS INFLUENCING DKVELOPMENT
Classification of factors
Classification of factors influencing development and
technological progress has been attempted on various
occasions (Netherlands Economic Institute, 1958; Traung
(Ed.), 1960; Morgan, 1956). Most sources distinguish
between "natural" and "human" influences, the former
encompassing factors related to fishery resources,
distances to grounds, climatic and nautical conditions,
land features, etc.; the latter including market, labour,
entrepreneurial, capital, technical, economic, institu-
tional, and political factors. There is agreement that (1)
the factors are often interdependent, e.g., the labour
market influences technical change and vice-versa, and
that (2) the separation between natural and human
factors is to a large extent an artificial one. Provided
motivation is strong enough, natural obstacles can be
overcome. If market forces are sufficiently powerful,
fishing centres are likely to come into being, notwith-
standing unfavourable coastal conditions (Morgan,
1956). Similarly, the reaction to a worsening of fishing
conditions may be a change to other fishing grounds,
construction of sturdier craft, etc. If humanity is starving,
farming the sea may become an economic necessity and
may provide the answer to increasing depletion of marin
food resources.
Discussion of "natural" factors does not come within
the scope of this paper. In the following, the "human"
factor will be considered both in terms of individual and
collective behaviour, i.e., from the individual consumer
or producer standpoint, and from the standpoint of the
institutions man has created in the interest of organizing
and controlling economic life. A distinction will be made
between sociological, cultural, psychological, and eco-
nomic elements motivating human action.
Demand factors
A wealth of literature on market research, including a
certain amount of information on the general aspects of
the demand for fishery products, is available. Here we
want to point out only that the cultural, economic, and
psychological factors influencing demand must be
carefully investigated by the development planner and
technologist. Income and price elasticities of demand
express the response of the market to changes in type,
quantity, and quality, of products offered for sale, and
thus indirectly have an impact on type, number, cost, and
utilization of craft and other equipment employed in Iisher-
ies. Traditional pielerenccs for species and forms of pre-
paration of fishery products, relative preferences (together
with relative prices) of fishery versus substitute food pro-
ducts, religious attitudes, consumption taboos, similarly,
have an impact on demand and, consequently also, on
technology of production and distribution. All of these
elements must be studied in relation to population trends,
including changes in age, sex, and family composition, to
gain a true understanding of market and technological
development possibilities.
"Human" input factors
Sociological factors influencing production: Social and
economic status of fishermen affects development and
technology in a variety of ways, for example in respect
to availability of labour, recruitment prospects for the
future, attitude toward work, productivity of labour, etc.
In developing countries in all parts of the world,
fishermen have the dubious distinction of ranking at the
lower end of the social scale. An investigation of the
causes of this phenomenon and of its impact on the
labour market, development possibilities, and techno-
logical change in fisheries, could form the subject of a
fascinating separate study. Poverty and economic
inferiority with respect to other groups, as in India
(Morgan, 1956), does not necessarily provide the
explanation. The income of the Bo/os and Somonos
fishing the Delta of the Niger River is substantially
higher than that of the farmers and cattle rangers in the
area, yet they continue in a state of social inferiority,
although economic improvement in recent years appears
to have narrowed the gap that separates them from other
tribal groups. The position of the Bozos is explained by
the fact that they were pressed into quasi-scrfdom by
invading tribes who, because of the economic services
the Bozos rendered as fishermen, did not destroy them.
The Somonos, in contrast, are a lower caste of the
Bambara people and take other, more lucrative, employ-
ment if the opportunity presents itself (Charbonnier
and Cheminault, 1964).
35]
Different ethnographic origin is an important factor in
social discrimination. This is true whether the fishermen,
as in the case of the Bozos, have been subjected by
invaders or whether they themselves are the foreign
element in an area, as in Hong Kong, where they are
reported to differ from the rest of the population also
in customs and education (Szczcpanik (Ed.), 1960.)
In some cultures where, as in Burma for instance,
strong religious feelings against the killing of animals
exist, fishermen are despised because they take lives and
are considered to be unscrupulous (Mead (Ed.) 1953).
In Central Africa, fishing in Lake Chad is in some areas
considered an occupation to be looked down on;
conditions are so hazardous that no-one else wants to
engage in fishing (La peche au Tchad, 1965). On the
other hand, willingness to accept hardships and risks
spurned by old-time settlers accounts for the fact that
new fisheries are often pioneered by immigrants. Develop-
ment of fisheries on the Pacific Coast of North America
has been credited, in a large part, to this circumstance
(Bartz, 1942).
Many cultures traditionally despise manual labour.
The warrior races of Africa find the discipline of in-
dustrial labour degrading (Mead (Ed.), 1953). In Korea,
fisheries under the Yi Dynasty remained inactive
because of the feudal tendency of despising fishermen
and others engaged in manual labour (Korean Fisheries,
1962).
Cultural factors influencing producer attitudes: The
individual's response to personal experience is determined
in large part by the culture within which he lives. "Pain
may appear as an injury, or an insult, or a challenge;
one may learn lo respond to rewards or punishments, or
merely react with terror to unusual situations; to prefer
death to dishonour or dishonour to inconvenience"
(Mead (Ed.), 1953).
The most serious mistakes made by technical experts
on their first contacts with producers in developing coun-
tries, result from their assumption that goal direction and
reaction to stimuli are the same as those of producers
in the countries from which they come. Desire for material
possessions and economic independence, and other
traits of the "homo economicus" are not always present,
or not present in the same degree, as in developed
countries (Spiccr (Ed.), 1952). The fact that people do
not have the same incentive to improve their standard of
living affects their readiness to take on employment or to
work on a steady basis. Fishermen may work solely to
catch enough fish to feed the family. Money may be
saved only to be "blown" on an elaborate ceremonial.
If the producer has enough food or money for his im-
mediate needs, he does not see why he has to return to
his job (Mead (Ed.), 1953).
In some parts of India (and elsewhere in the Far East),
where such ambitions for improvement as may exist tend
to be thwarted by the quasi-serfdom position toward the
middleman, fishermen are reported to "simply not care
for more than three meals a day" (Szczepanik (Ed.),
1960). Fishermen in Madagascar are said to lack ambi-
tion. As long as this attitude toward work prevails,
investment in fisheries must of necessity remain at a
modest scale and introduction of new methods is not
justified (Couvert, 1963).
In many parts of the world man adheres to the belief
that his actions have no causal effect upon his future. A
corollary of this fatalistic attitude is that man tries to
adapt himself to what he finds rather than tries to change
anything in his environment (Mead (Ed.), 1953). The
feeling that "nothing can be done about it" or that "all is
in the hands of God" reflects itself in curious ways. The
faith he possesses, or the superstitions he adheres to,
may make the fisherman accept hardships or dangers
others would be inclined to shun. It may, in other cultures
or other circumstances, deprive him of the incentive to
extricate himself from danger. In some parts of Africa, a
fisherman who is attacked by a crocodile will make no
special effort to escape, nor will he be helped by his
colleagues. Even in Western countries, fishermen often
will not learn how to swim, or will not keep life-saving
appliances aboard, if they believe, as is sometimes the
case, that it is written in the stars whether they are
destined to drown or not.
In Hong Kong, most of the fishermen believe that
their gods or goddesses will protect them, bring them
good fortune and lead them to the best fishing grounds.
Instead of purchasing vessel insurance policies, they are
reported to prefer "buying and burning incense to
honour the gods and to worship the ancestors, and paper
clothes to placate the evil spirits . . . (they believe that)
they would meet disaster if they displayed any sign of
lack of confidence in the protecting or destructive
supernatural powers" (Szczepanik (Ed.), 1960).
Belief may influence peoples' attitude toward life at
sea, the mode by which they choose to make a living.
Orthodox Hindus may suffer loss of caste if they leave
inshore or "green" waters for the darker waters of the
deeper seas. This kind of outlook is thought to have had
the effect, in past centuries, of retarding the evolution of
Indian fisheries (Morgan, 1956).
In his study on the fish trade in the Northern Cameroon,
Couty (1964) cites several authors who have written on
the influence of religion and philosophy of life on
entrcpreneurship in developing countries. According to
one of these sources, the fatalistic element in the Moham-
medan religion, not to speak of specific commandments
of the Koran, such as the prohibition against the charging
of interest on loan, had held back the development of a
dynamic business spirit among professors of this faith.
Another authority is quoted explaining the low rate of
capital formation in developing countries in terms of the
business people's reliance on rapid gains from purchase
and sale of merchandise and their reluctance to
make long term investments for productive purposes.
Couty believes that stagnation in fisheries and over-
crowding in the trade sectors in Tropical Africa can,
in some measure at least, be accounted for by the
above factors.
Some cultures, such as the Burmese one, disparage the
accumulation of capital. This, plus the tendency to
spend much money for religious purposes, and the tenet
that a Buddhist cannot make a valid will, prevent the
creation of capital needed for industrial enterprises of
major scope (Mead (Ed.), 1953).
[36]
The natural conservatism of fishermen and other
primary producers is often only a reflection of the value
which traditional life holds for them. This comes to the
fore when attempts are made to introduce change without
the assistance -or worse yet, against the will — of those
in traditional authority. In many parts of Africa, thus,
obedience to someone without traditional authority
appears extremely difficult to enforce (Mead (Hd.), 1953).
The head of the family, as among the Bozos and Somonos
in the Niger Delta, attends to the needs of individual
members and watches out, to the best of his ability, for
the interests of the group. He pays the taxes, buys and
distributes requisites and consumption goods, sells the
catches, and gives guarantees to suppliers on loans for
purchases of nets and sees to the repayment of these
debts (Charbonnier and Cheminault, 1964).
Traditional authority sometimes has its source, as in
the case of the Bozos, in long-inherited beliefs relating,
for instance, to the establishment of fishing rights. In the
Bozo cult, the river is thought to be the home of water
spirits whose favours must be courted to ensure un-
troubled exploitation of the waters and a successful
fishery. The Bozo tradition has it that their people have
concluded an alliance with the water spirits. This auth-
orizes them to live off the product of the fishery, provided
they respect certain taboos and offer regular sacrifices.
The fishery masters in the various fishing /ones all take
their authority from the first family head who had
occupied a hitherto unfished zone and Hd concluded
an alliance with the local water spirit (Dago!, 1949).
Religion and traditional ruithority can be formidable
obstacles to efforts to institute improvements. In some
cultures, the violation of a taboo is among the worst of
crimes, and the person in traditional authority decides
what constitutes a violation and what not. Conversely,
there is no easier way to succeed than by winning the
co-operation of the family head, fishery master, or other
local chieftain in the implementation of a project.
Working conditions, equipment preferences, and wage
levels and the availability of labour: To compete success-
fully in the labour market an industry must aim "to
improve safety, increase comfort, lessen human exertion,
and pay better wages" (Soublin in Traung (Md.K 1960).
Technological improvement helps meeting these objec-
tives. On the other hand, there arc elements in the
nature of the fisherman's profession which have a basic,
essentially adverse, influence on labour supply. The work
of the fisherman is hard and fatiguing. Hours of work or
days off, as a rule, arc not regulated. The fisherman has
virtually no family life; he has limited opportunity to
participate in community or political life. Accidents on
board arc frequent.
Irregularity and uncertainty of earnings, inadequate
social security coverage of the profession, etc., are
among the economic disincentives to entry into the
fishing labour market. This labour market also reflects
abundance or scarcity of alternative employment
opportunities in the local area and density of population,
in general. Distance of fishermen's settlements from
x>rt may mean additional travel and loss of already
imited leisure time. It also limits opportunities for the
fishermen's sons to get to know life at the port and to
acquire a liking for the fishing profession. This may be
of importance for future recruitment, where a large
portion of the young fishermen comes from traditional
fishing families (Vanneste and Hovart. 1959).
Because of this, the attitude of parent fishermen on
the professional choice of their sons must be studied.
Ceylonese fishermen, at least those at a higher level of
literacy, are discouraging their sons from choosing
fishing as an occupation, warning them of the hazards
inherent in the work, and the consequent vicious circle of
low incomes, constant indebtedness, and physical and
economic distress for the families. The children appear to
heed the parents' advice, and are deciding against
following the profession of their fathers also because of
its low social status (Dc Silva, 1964).
In many instances, mobility out of fisheries is restricted
by lack of education and of knowledge of alternative
oppon unities as well as by the basic conservatism of
fishermen. Many fishermen show extraordinary tenacity
before they stop trying to wrest a living from depicted or
unprofitable fisheries (Beever, 1955). As development
progresses, and new opportunities arise, both in fisheries
— as the result of industrialization of fishing operations
and concentration of fishing centres-- and in other
sectors, marginal producers may stubbornly continue to
seek employment where they have always lived, in small
scale operations (such as inshore shell-fishing, for which
the disadvantage of their ports is not so great) or by
developing additional sources of income, e.g. from
tourism (Morgan, 1956).
Willingness to make sacrifices, in regard to working
conditions and wages, differs substantially between
fishermen of different countries, and areas within
countries according to alternative economic opportunities.
In the Greek Islands, there is a centuries-old pattern of
men going to sea as fishermen and staying away from
their homes for many months. This parallels charac-
teristic emigration patterns, where the men wait until
they have saved up enough money in the new country to
have their families follow them (Mead (Ed.), 1953). In
the United States, differing economic opportunities in
various sectors are probably reflected by the lower
average age of fishermen making trips of shorter duration
than of those having to stay at sea for longer periods
(Alverson in Traung (lid.), I960).
The question of the availability of crews for trips of
extended duration plays a prominent part in all plans
for large scale factory ship operations. In the United
Kingdom, it was thought that, while it might not be
difficult to find crews for two or three factory ships
staying at sea for three months or longer, plans for a
large expansion might very well be defeated by the
inelasticity of the domestic labour supply for operations
of this type (Report of the Committee . . . , 1961).
Reluctance to take a berth on a boat making trips of
several months' duration may, to some extent, be over-
come by the lure of high earnings and by making life
on board more palatable, e.g. through "labour easing",
increasing crew comfort, improving leisure time utiliza-
tion.
In this connection, characteristic likes and dislikes of
37 J
crews in regard to arrangements on board require study.
At the Second Fishing Boat Congress a plea was made for
providing better shelter to make life easier on board and
to increase efficiency, since the crews tired less and worked
better in sheltered space than when wet and cold (Krist-
jonsson in Traung (Ed.), 1960). Dislike of living forward,
doubts about the safety of working on wide exposed aft
decks, were other "crew factors" of influence on layout
on board mentioned at the Congress (Tyrrell in Traung
(Ed.), 1960).
Other labour availability factors:
Tradition, climate, and other factors, however, have a
bearing on fishermen's attitudes toward craft and gear,
and generalizations are of little value in this sphere. At
the First Fishing Boat Congress, for example, fishermen
in the Bombay area were reported to be prejudiced
against fishing from decks and as preferring open decks
(Setna, 1955). Also, the extent to which demands for
increased safety and comfort can be met is determined by
economic considerations. Fishing vessels that are 100
per cent safe, thus, are difficult to design because of the
commercial requirements of the owners. Especially on
small vessels, increased safety has to be attained by
improved seamanship (Tsuchiya in Traung (Ed.), 1960).
Technological compromises arc necessary, where im-
provement in some sphere is possible only at the expense
of sacrifice in another: more shelter while working, thus,
may mean poorer quality of sleeping accommodation,
with the quarters located in the foreship rather than aft
(De Wit in Traung (Ed.), 1960).
In some developing countries, the fishing boat is not
only a workshop but also the home of the fisherman. In
Hong Kong, about 95 per cent of the fishing households
are living on boats owned by them and only 5 per cent
in rented houses or partly in rented houses and partly
on boats (Szczepanik (Ed.), 1960). Patterns of this type
must not be ignored by the promoters of technological
development.
Where different tribes or racial groups fish side by
side, peculiar craft and gear preferences arc often
observed. In Malaysia, the Malay fishermen use long and
narrow boats with a shallow keel especially designed for
speed and day fishing, whereas the Chinese rely on heavier
and deeper boats that can stay out at sea for several days
or weeks. Economic reasons and deep-rooted traditional
beliefs are cited as reasons for these preferences (IPFC/
FAO, 1961).
The Bozos and Somonos in the Niger Delta each have
pronounced gear preferences which are related to the
fishing places they frequent, the Bozos traditionally
fishing in marshy areas, the Somonos in the main bed
of the river (Charbonnier and Cheminault, 1964).
Pronounced equipment preferences are often explained
by prestige factors, vanity of the owners, and similar
elements. A bigger boat than necessary is often operated
to impress others. Many fishermen want higher powered
engines than are normally recommended by naval
architects and marine engineers. Reaching the fishing
grounds early and bringing the catch to the market
before the other fishermen may at times raise earnings
more than fuel costs but, in other instances, excessive
powering may merely be explainable in terms of psycho-
logical factors (Proskie and Nutku in Traung (Ed.),
1960). Distrust of mechanical power, equally, may lead
to a pattern of operations not justifiable in economic
terms. Not so long ago, some Maltese fishermen were
reported to have had two or more engines installed on
their boats for fear of engine failure at sea. With in-
creased experience in repair and maintenance this
practice was expected to disappear (Burdon, 1956).
Labour quality factors: Labour quality, as reflected by
physical strength and skills, may have an important
bearing on minimum size of crew for certain vessels
and on the type of equipment that can be installed on
board. Wide variations between regions and groups of
fishermen exist. Training is expensive. Economically
speaking, skill represents capital invested in labour.
Fisheries requiring a high level of skill, consequently,
tend to be capital-intensive. If skills are low, installations
on board have to be simple (Netherlands Economic
Institute, 1958). The better quality skippers and crews arc
said to seek employment on the better and newer boats.
As fishing fleets arc modernized in increasing measure,
the advantage the newer boats derive, as a result of this
tendency, diminishes (Report of the Committee
1961).
Managerial quality has an even larger impact than
labour quality on possibilities of realizing development
opportunities. In many developing countries, entre-
preneurial talent is at a premium. Skipper-ownership of
vessels may stimulate better management. This may
partially account for reluctance on the part of the
processors to integrate backward into fishing (Nether-
lands Economic Institute, 1958).
Economic considerations influencing entrepreneurial de-
cisions: The influence of cultural and psychological
factors on development and technology declines, and
that of economic factors increases, as high levels of
organization are attained. The economic objective of the
individual firm is attained by maximizing profits, i.e. by
maximizing the difference between total earnings and
total costs.
Profits arc affected by the following four variables:
physical inputs, prices of inputs, physical outputs, and
prices of outputs. Where fishing is carried out predomi-
nantly by many small producers, the individual entre-
preneurs must accept input and output prices more or
less as given. Strategic buying of inputs can result in some
cost savings. Unless opportunities to preserve and store
catches on board and on land exist, however, an in-
ventory policy to take advantage of peaks in product
prices is not possible.
For vertically integrated fishery companies, the situa-
tion is different in this respect since they are in a position
to pursue a strategic inventory policy. Also, since
they are interested in the overall profit from operations,
they are prepared to carry along departments which do
not make any or, in some instances, even lose money,
provided that these departments support, in the long
run, other, profit-making, activities. Some of the trawling
companies in the United Kingdom, for example, which
38
have interests in related businesses appear to make
rather substantial profits on the processing, whole-
saling and retailing of fish. These companies are believed
to derive sufficient advantage in continuing ownership
and maintenance of their own fleets, to compensate for
the losses sustained by the fishing vessels alone (Report
of the Committee . . . , 1961).
The large integrated company also has other ad-
vantages in the market such as, for instance, the pos-
sibility of obtaining a higher price for products sold
under its own brand.
Disregarding the specific situation of the large inte-
grated enterprise, let us see how the independent fishing
enterprise tries to attain its twin objectives of increasing
value of output for a given cost of inputs and of reducing
cost of inputs for a given value of output.
The first objective calls for orienting production and
disposal policies toward reaping maximum bcneiits from
market opportunities. This means, first of all, that the
entrepreneur has to use the equipment and crews he has
available for operations in such a manner as to bring
the most valuable species (he can take) to the best-paying
markets (he can reach), in such quantities, and in such
relative proportions, as to maximize receipts. His
success, aside from resource factors, depends on the skill
with which he manages his inputs (entrepieneurial
skill, the choice he makes of "xhniques within the
limits of the range pernvtted by the equipment at his
disposal). It also hinges on the knowleJg-/ he has of
market conditions at the different landings .it which his
vessels are in a position to Lull.
Reducing input costs for a given product value presents
different problems. The entrepreneur looks for the best
possible bargain he can obtain as regards cost and
quality of inputs. He also seeks to minimize the quantity
of each input required for producing a given level of
output. Finally, he tries to adjust input ratios so as to
save on scarce and more costly items within the scope
set by conditions of a technical nature (in fishing, this
scope may often be rather small, since resource, occano-
graphic, and other conditions may make a certain type
of fishing unit mandatory). If, for example, the capital-
labour cost ratio is low, labour is relatively more ex-
pensive and the emphasis will be on labour saving; if
high, there will be an effort to save capital (Netherlands
Economic Institute, 1958).
Labour inputs:
Total labour force in the area, alternative employment
possibilities, wage levels, skill levels, availability and cost
of labour-saving capital, general economic conditions
and conditions in the fishing industry, as well as expecta-
tions regarding future trends in these variables, all
influence entrepreneurial decisions on labour inputs.
These decisions are among the most important the entre-
preneur has to make, since labour costs are, as a rule,
the biggest cost item in fish production. The need to
save on labour cost may, in turn, have technological
implications and, among other things, may influence
fishing vessel design.
Where labour is plentiful and cheap, installation of
costly labour-saving devices would tend to reduce the
profits of the enterprise, unless the excess of the expense
on equipment over the saving in labour costs is more
than compensated by receipts from increased production.
Labour intensive operations appear uneconomic
where the resource situation militates against their
employment. In Japan, labour-intensive beach seining
operations are still common in the fishing household
sector of the industry; in heavily fished areas where the
density of reasonably-sized fish in inshore waters is low,
it has been pointed out, the technique may become un-
economic (Morgan, 1956).
Reduced crew needs have been cited among the ad-
vantages of small stern-trawlers in a study recently
carried out at Aberdeen. Another advantage cited in
favour of these craft is that, because of their light
tonnage, they do not require certified skippers to take
them to sea (Fish Trades Ga/ctte, 1965). Aside from
technical considerations, craft and equipment that require
smaller crews are favoured in situations where the labour
supply factor has become critical.
More highly skilled and trained staff -such as certified
skippers - arc, of course, harder to find and demand
higher compensation, increasing the economic problems
of the enterprise if earnings do not increase at least
proportionately. Employment of sub-standard quality
labour also has unfavourable consequences on economic
results. In a report on the economy of the Province,
progress in the Newfoundland industry was considered
not just a matter of technological improvement but also
of raising productivity within the scope of existing
equipment. The backwardness of operations was blamed,
in large measure, on human inefficiency (Copes, 1961).
In many countries of the world, fishing labour is
increasingly in short supply. This is true even in Japan,
where crew problems, because of the scarcity of alter-
native employment opportunities for the large supply of
fishing labour until not so long ago, were virtually non-
existent. Recently it was reported that some of the larger
boats were unable to leave port because of inability to
hire crews. Even small boats, it is said, arc beginning to
find it indispensable to mechanize to avoid crcwing dif-
ficulties (1PFC/FAO, 1964). Rising wage costs often
reflect growing crew shortages and, similarly, encourage
the introduction of labour-saving devices.
Labour scarcity may have an impact on capital costs
also in another direction: the premium to induce labour
to accept employment on boats may have to be paid in
terms of costlier installations on board, to meet a demand
for increased crew comforts. The shortage of crews for
longliners, which has developed in recent years in Hong
Kong, thus, has produced a situation, where crews are
reluctant to hire out on vessels which do not possess
power-handled gear (IPFC/FAO, 1963).
Capital inputs:
Within the framework imposed by existing natural,
technological, and political conditions, the entrepreneur
tries to save on capital input costs by buying the minimum
necessary quantities of serviceable equipment at the most
advantageous prices. Cost comparisons between other-
wise equally satisfactory items must be made on the basis
of total cost over the service life of the items rather than
39
on the basis of original outlay only. This requires the
capitalizing of expected operating costs which must be
added to original investment. Assessing the relative
advantages of aluminium versus steel funnels under
existing price conditions in his country, one expert found
some years ago that, while the initial investment was
higher for aluminium funnels, the latter were
substantially less expensive in the long run because of
their longer service life and lower maintenance costs
(Goldsworthy, 1955).
Every major investment requires a careful cost analysis
to ensure that payment calculations will not be far off
the mark. To assess economic results of freezing fish at
sea, thus, it has been suggested that the following be
considered in addition to the costs associated with the
handling of iced fish:
• factors affecting vessel costs
• extra personnel required to operate freezing
equipment
• additional cost of vessel due to freezing equipment
and additional space required for storing frozen
fish
• repairs and maintenance of freezing equipment
• insurance for freezing equipment
• depreciation of freezing equipment
• fuel for operation of freezer
• additional equipment and labour required for un-
loading the frozen fish (Slavin, 1960)
A proposed change from one material to another,
e.g. from wood to plastic, must be studied from the stand-
point of its potential effect on marine insurance pre-
miums (MacCallum in Traung (Ed.), 1960). In the
introduction of electro-fishing, savings in gear costs must
be measured against increased power and fuel costs
(Morgan, 1956).
Initial cost must be considered in relation to existing
level of purchasing power and financing opportunities.
Running costs should largely be defrayed from earnings.
In introducing better thermally insulated fishholds in
Hong Kong, a craft technician in 1963 was reported to
have made recommendations providing the greatest
possible increase in thermal efficiency at the lowest cost
compatible with conditions in the fishery, which were
characterized by the low economic resources of the
fisherfolk. The conservative attitude of the fishermen in
the Crown Colony also was said to account for the fact
that few of them were prepared to pay even a small
premium for better material and more advanced work-
manship (IPFC/FAO, 1964). Desire for a quick turnover
constitutes another reason for unwillingness to make a
bigger initial investment. Malaysian boat owners are
reluctant on this account to pay more for better engines.
Engines for new craft are mostly improvised units of
industrial types which are modified by local foundries
(IPFC/FAO, 1964).
Lack of materials and facilities for manufacture of
boats and other equipment in a country may be a serious
handicap to fisheries development. Shortages of boat
lumber, engine parts, sail canvas, nets, manila rope,
fuel and lubricating oils are among the major problems
of the industry in the Republic of Korea (IPFC/FAO,
1961). Where foreign exchange is scarce, or where severe
import restrictions are imposed, such difficulties are
exacerbated. The cost of imported equipment may not
only come higher because of the initial outlay which
may have to cover additional expenses for import
duties, customs clearance, transport, etc., but also
because of the frequent necessity to carry larger stocks
of spares to prevent disruptions in operations due to
long delivery periods (Netherlands Economic Institute,
1958).
Compared with other countries in the Indo-Pacific
Region engines are cheaper in countries where no or very
low import duties are imposed, e.g. in Hong Kong and
Singapore. In general, it was found that choice of an
engine did not depend so much on its performance — the
primary considerations being availability, price, previous
experience with any particular engine and the country's
import-export trade relations. Availability of spare
parts, and repair and maintenance services was secondary
in the selection of engines, particularly in the countries
where mechanization of fishing craft was of recent
introduction and where aid-giving agencies supplied
such engines.
Prices paid for boats and other equipment depend,
to a large extent, on competition in the markets for
capital inputs and on cost savings that can be effected
in the boatyards and other manufacturing facilities. In
Hong Kong, prices of diesel engines and spare parts as
well as fuel and lubricating oils are considered reasonable
because these markets are highly competitive (1PFC
Inter-Session Report). Cost reductions in the boatyards
are sought, for instance, through use of cheaper wood
(India), elimination of timber waste (Thailand), use of
power tools to reduce labour (Malaysia). Improved
techniques may help to realize additional immediate cost
savings, or to raise quality of the final product and, thus,
lengthen service life and lower costs in the long run
(Hong Kong, Japan).
Standardization in boat design and construction and
layout on board arc among the most important con-
tributions the technologist can make toward the cost
reduction objective. Economies effected in this manner
may be shared by the yards with the buyer who may
have to pay less on acquisition, and may benefit also as
the result of savings in labour cost through increased
efficiency of operations. One expert estimates that the
cost of each of two identical vessels may be only 90 per
cent of the cost of a single boat. If the number of repeti-
tions reaches eight or ten, the unit cost should level out at
about 80 per cent of the single contract cost (Benford and
Kossa, 1960).
Labour efficiency is enhanced through standardization
on board, in particular where there is a high turnover of
crews, as on trawlers in the United States. If all gear and
machinery are in the same places on different vessels,
changing berth presents no problem of adjustment to
work on another vessel (Ringhaver, 1960). Even without
standardization, use of mass production methods, by
itself already, has a cost-lowering impact.
External economies deriving from the size of the fleet
in a port also may result in cost savings to the boat
owner.
[40]
A large fleet makes it economic to store supplies and
spare parts in quantity and, thus, reduce costs per unit.
Large operations also carry with themselves a momentum
for further development, attracting new related industries
and stimulating erection of necessary shore facilities
(Netherlands Economic Institute, 1958).
Running, repair, and maintenance costs, similar to
capital equipment costs, are related to availability and
price of fuel, spare parts, and other supplies; experience
and skill of labour; shore facilities, etc. Availability may
have played an important part in locating certain
industries. According to one source, the advent of steam
power for fishing vessels tended to favour the develop-
ment, in the United Kingdom, of ports near coalfields.
The higher price of coal fuel in the southern English
fishing ports was an important factor retarding the
conversion of operations to power (Morgan, 1956).
Another source refers to the influence of regional
differences in relative prices of coal, oil, and petrol
on the complexion of the industry in some countries. Jn
1952, thus, the relative prices of fuels in Germany were
such that the operation of steam trawlers (coal) was
cheaper than that of dicsel-trawlers. The same was true
for the United Kingdom. In the Netherlands and
France, the reverse was true (Netherlands Economic
Institute, 1958).
Fuel costs may be so high that sails arc still the cheapest
method of propulsion. In some areas of North America
costs and scarcity of spare parts and fu. ! made some
experts think, not so long ago, that the improvement of
sails would do more to l.^vei costs than motorization
(Chapellc, 1955).
Before leaving the subject of fixed capital and working
capital costs, a word must be said about capital con-
sumption and money capital costs. The latter are
represented by the prevailing rate of interest at which the
entrepreneur can borrow or which he must consider in
assessing alternative employment opportunities of his
money capital. Capital consumption costs must be
considered as given, where governments stipulate de-
preciation methods, rates and periods. In the economic
sense, capital consumption is affected by the care, or
lack of care, exercised in handling equipment and by the
rate of obsolescence (the pace of technological progress
in the industry).
Entrepreneurship and financing opportunities:
Again and again, slow progress in fisheries is blamed on
poor financing opportunities or lack of entrcprcneurship.
The backwardness of the bulk of Japanese fisheries before
the last war was attributed to a shortage of capital
rather than to lack of enterprise or technical know-how
(Morgan, 1956). As a rule, the three phenomena,
backwardness, lack of entrepreneurship, and inability to
obtain financing, are closely inter-dependent. It may be
just because fisheries are poorly developed that they find
it difficult to obtain financing at reasonable cost and/or
to attract imaginative entrepreneurs. The bigger, more
highly developed ports find it much easier than the small
ones to meet capital and manpower needs. They have a
higher degree of organization, a greater reputation, and a
greater industrial and social capital on which to base new
enterprises (Morgan, 1956). In the United States, the
favourable post-war profit history of shrimp trawlers has
been cited as a major reason for the ease — compared to
other fishing craft — of borrowing funds for their pur-
chase from financial institutions (Chapelle, 1955).
The risk element, which, because of the vagaries of
nature, is perhaps greater in fisheries than in many
other industries, adds to the problems of securing
adequate financial help and management talent. To some,
though, the gambling opportunity is an attraction
rather than a deterrent. Side by side with marginal
elements one finds, therefore, some of the most courage-
ous investors in fisheries (Beever, 1955). In a large part
of the world, however, the most important limiting
factor is on the management side. Provision of financing,
donations of capital equipment, etc., may be of no avail,
and may now and then even hasten the ruin of operations
which have been carried on so far on a scale proportioned
to existing management potentialities. Typical results
that can be expected when financing is expanded beyond
existing absorption capacity are described in a report on a
loan programme instituted a few years ago in a country in
Central Africa:
"In a good many cases the acquisition of a loan
and the opportunity to increase the scale of opera-
tions has led not to the expansion of a business but
to its collapse. . . .
". . too often the case of failure is mismanagement.
In general the lesson is still to be learned that the
keys to success are personal attention to the detail
of fishing operations by the owner of the business;
the setting aside, in periods of affluence, of money
to provide for the eventual replacement of worn
pear; and contentment with modest profits on
individual sales so long as those sales arc quick and
repeated" (Report of the Department . . . , 1962).
Success in the fishing sector is closely linked to sound
planning and management in the secondary and tertiary
sectors. If facilities, entrepreneurship, organi/ation, and
financing in processing and distribution is inadequate,
fishing is bound to suffer, since markets are insufficiently
exploited. Similarly, if the fishermen are not aware of
existing limitations in the economic disposal of their
catches, their investments may turn out to be "mis-
investments", i.e. capacity installed may be too large
or of the wrong type (Netherlands Economic Institute,
1958).
Institutional factors:
With the progressive development of fisheries, indepen-
dent, owner-skippered operations decline in relative
importance. Only big companies have the necessary
capital for the larger, and more expensively equipped
ships and the ancillary organization that are likely to
be needed for deep sea fishing operations, for instance
with mother ships and attendant catching and carrying
vessels (Report of the Committee .... 1961).
As the scale of operations increases, there is a tendency
not only toward integration at the company level but
also institutional arrangements relating to the activities
41
of groups of operators or all fishermen become more
frequent. Such arrangements are arrived at by agreement
among the operators themselves or under the aegis of
public bodies.
By its nature, one observer writes, fishing must be
carried on by small groups of men, and personal relation-
ships cannot be submerged to the extent that they are in
most modern industries. Notwithstanding his strong
sense of belonging to a group, however, the fisherman's
individualistic character has made him very much slower
to acknowledge this by entering into formal organization
(Morgan, 1956).
The problems of promoting co-operative activities are
quite different in developing countries from what they
are in developed countries. In the latter, co-operation
refers usually to a group created to satisfy the needs of
the individual members at some future time. In the
developing countries, co-operative units, in contrast,
derive their origin in the past. "Here an individual is
born into a family, a village, a church group and when
he acts for the welfare of the unit he is often merely
filling his prescribed role. The co-operation is incidental"
(Mead (Ed.), 1953). This difference in the roots of co-
operative endeavour accounts for the conservatism and
resistance to change often characteristic of commercial
patterns in the less developed areas of the world.
Lack of immediately apparent evidence of the economic
benefits resulting from co-operative membership has been
considered the main obstacle to a faster spread of the
movement, among other countries, in Hong Kong
(Szczepanik (Ed.), 1960). Elsewhere, co-operative
organization has contributed toward creating the means
for the acquisition and operation of improved facilities,
has enabled fishermen to present their case more effec-
tively before public authorities, and has strengthened
their bargaining position vis-a-vis the trade sector
(Netherlands Economic Institute, 1958).
Financing for development is facilitated by establish-
ment of co-operatives, not only because of the opportunity
it affords of pooling the resources of the members but
also by the circumstance that public bodies often prefer
to channel their aid to fishermen via co-operatives. The
opportunity to obtain such financing through co-
operative membership frequently constitutes a strong
incentive for joining such organizations. Conversely,
where distribution of loans through co-operative channels
is abandoned, fishermen's societies have at times col-
lapsed (Szczepanik (Ed.), 1960).
Organization at the distribution end, too, has very
often been of great influence on development in the fishing
sector. Financial dependence on the middleman in the
Far East, on the mammy in West Africa, has restricted
the fisherman's freedom in the purchase of necessary
requisites for his operations. The stranglehold the trader
has over the fisherman results in low prices being
offered for the lattcr's fish, exorbitant prices demanded
for goods purchased, and heavy cost of financing, the
trader functioning as money-lender as well as supplier of
requisites and purchaser of products (Szczepanik (Ed.),
1960). In the Thana District in India, the middlemen
were said to be reluctant to supply capital for develop-
ment and were ready to advance loans for short-term
working capital only. They also shunned the additional
risks that would have been attendant to an expansion of
markets farther inland and pursued a price policy which
robbed the fishermen of all incentive to increase output.
The responsibility for slow development was, therefore,
put directly at their doorstep (Szczepanik (Ed.), 1960).
Sometimes it is not so much the peculiar form of
organization on the marketing side which discourages
investment, or reduces incentive to economize or increase
output, but characteristic institutional arrangements
relating to hours, wages, or unemployment compensa-
tion in fishing. Attempts to regulate hours of work on
board have created severe economic problems in Guinea,
and so has a system of compensation based on fixed
monthly salaries in Uruguay, because there was no
incentive to increase catches. The traditional system of
compensating crews on a share basis is only gradually
being modified as a result of increased industrialization of
operations and a lessening of entrepreneurial risks. In
the more advanced fishing countries, the way toward a
fixed wage system with production bonuses may be via
introduction, in lay agreements, of a guaranteed
minimum.
Extension of unemployment insurance to fishermen,
to lessen the uncertainty connected with the exercise of
their profession, may have an adverse influence on
productivity. In Newfoundland, unemployment benefits
may add just enough to family income to lessen the
urge to work harder. "Unemployment insurance may
thus become a subsidy on indolence. This is particularly
evident in the difficulties that are experienced in getting
fishermen to work in the winter season. New boats have
been introduced that can prosecute the fishery in the
winter. But fish companies have experienced difficulty in
obtaining and maintaining crews on their trawlers. It
has also been observed that operators of longliners on
the North-east Coast will prefer to remain idle and
collect unemployment insurance, rather than continue to
fish on the South Coast during winter." Protection of the
fisherman and his family from the consequence of a
disastrous failure of the fishery, it was thought, could
best be achieved in the Province by a scheme of catch
failure insurance (Copes, 1961).
Not only output but cost structure, too, may be
adversely affected by provisions relating to the admini-
stration of unemployment indemnity schemes. Under
Belgian legislation, fishermen may do maintenance
work on board only, in order not to forfeit their entitle-
ment to the payment of indemnities. For shore main-
tenance work, the boat owners, therefore, must employ
special crews. In the marginal coastal fishery, the owners'
earnings are too low to enable them to incur this addi-
tional expense (Vanneste and Hovart, 1959).
Government and the development of fisheries:
Government policy affects fisheries and other industrial
enterprises by allocating, transferring, and controlling
the use of the means necessary to attain an increase in
output or a reduction in inputs. It achieves its purpose
either by direct legislative intervention or, indirectly, by
activities designed to encourage or discourage private
initiative.
42
An understanding of possible alternative goals of
public policy is necessary for evaluation of specific action.
The goals of maximizing (or increasing) economic
progress in the country, maximizing total economic
welfare, maximizing the total welfare of individuals in a
given industry, maximizing income or maximizing net
income in an industry, are not identical and withoiu
conflict. While government policies are seldom as well
defined as to allow a clear identification of these aims, and
while several aims may be pursued simultaneously, an
industry may seriously delude itself if it expects public
issues resolved solely in terms of its parochial interests.
In highly developed countries, economic progress will
lead to a transfer of resources from primary industry
to other sectors. This may have as consequences the
lowering of total fishing income as well as a redistribu-
tion of that income within the industry, and eventually
the exit of marginal producers. Governments may
decide to accelerate rather than retard this process
while simultaneously trying to alleviate the attendant
hardship.
Welfare considerations make it mandatory to bring
policies for economic progress in line with capacity of
other sectors to absorb marginal elements. The pleas of
an industry that is destined to decline within the natural
course of economic evolution, on the oihcr hand, should
not, in the national interest, alw, ys be answered with
increased financial suppor*.
There may be a need to aim for a buirr economic
performance by redressing the balance between various
elements in the industry. The resource situation in
inshore fisheries, as in Newfoundland, may make for
action in this direction even more acute. As long as
limited catches had to be shared by the same large
number of men, incomes were thought to have to remain
low and new techniques and equipment were considered
of no avail. Only by transferring men from the inshore
fisheries to deep-sea fisheries, where the much higher
production of the average fisherman could keep several
plant workers busy, could one hope for an economic
improvement (Copes, 1961).
In the centrally planned economies, government
controls all investment and operations, with central and
local bodies participating in varying proportions (in
different countries, and in one country over a period
of time) in decision-making (Swiecicki, 1960).
In Western countries, governments have, in some
instances, hesitated to assume too drastic a role in
shaping the course of future development (e.g., by
discriminating for or against certain classes of vessels in
its support policies). In the U.K., for instance, the need
for flexibility in policies is considered paramount. A
comprehensive enquiry on the industry carried out a few
years ago, thus, argued in the following terms: "Tastes at
home and markets abroad change, new processes open
up new demands, technical advances in vessel and gear
design reveal new possibilities, new competitors appear,
fish stocks themselves advance and recede with sometimes
startling speed. It is particularly important to preserve
flexibility in a subsidized industry, for there is always
some danger that a subsidized industry will become
ossified, and that economic change will be met by
pressure for modification — usually by way of increase-
in the subsidy. We do not think that anyone can predict
in detail what will be the best size and shape for the fleet
in even five years* time; and we do not therefore support
the idea of a balanced fleet cut to a pattern imposed from
above" (Report of the Committee . . . , 1961).
Generalizations on fisheries policies in developing
countries are as difficult to make as on policies in de-
veloped countries. The general tendency is to give
attention, where prospects for substantial foreign
exchange earnings from the establishment of an export-
oriented industry do not exist, to social and welfare aspects
as well as to economic aspects. In the Indo-Pacific Region,
for instance, increased attention is being devoted to the
welfare implications of progressive modernization in
the fishing sector and one of the recurrent recommenda-
tions of the Indo-Pacific Fisheries Council has been a
proposal for the conduct of a comprehensive study on
this subject.
Another tendency sometimes encountered in develop-
ing countries is to do too much and too fast, both in
relation to availability of inputs and to market capacity
within the foreseeable future. The scope of the Ghanaian
long-range trawling programme has been commented
upon on this score; the rationale of government policies
is not questioned, in view of population growth trends
and the economic necessity to develop import-substitut-
ing industries (Crutchfield and Zei, 1964). Elsewhere,
overly ambitious programmes may merely reflect a desire
to make a spectacular showing, to win political support
at home, to impress neighbouring countries, etc.
In implementing policies, governments may use one
instrument, e.g. finance, to achieve a variety of objectives.
Conversely, the attainment of one objective, e.g.
improvement of productivity in the fishing sector, often
is sought by various means.
Financial assistance may be rendered in different
ways. In the centrally planned economics, the govern-
ments allot non-repayable investment funds to individual
enterprises and, as a rule, also exercise a decisive in-
fluence on the character and technical features of the
investments (Swiecicki, 1960).
Elsewhere, grant assistance usually covers only a part
of total investment costs, with additional help sometimes
being provided in the form of loans at low interest rates.
Direct and indirect subsidies to meet costs of operations,
tax concessions, exemption from payment of customs
duties on imported requisites, provision of guarantees to
encourage loans by private lenders, are among other
forms of iinancial assistance to entrepreneurs in the
fishing sector (Beevcr and Rudd, 1960, and Holliman,
1962).
Provision of financial help may aim to ensure the
economic survival of the fishing fleet, in general, or may
have a more specific objective such as technological im-
provement, redress of the economic balance between
different classes of operators, etc. Among the means of
achieving these objectives are establishment of eligibility
criteria and intentional discrimination in the considera-
tion of loan applications. In the United Kingdom, until
recently, only vessels under 140 ft (43 m) in length were
eligible for grants and subsidies. This was thought to
43
have had a decisive influence on the building of a high
proportion of trawlers just within this limit (Report of
the Committee . . . . , 1961). Recommendations made
some years ago for the establishment of a Fisheries
Loan Fund in Malta envisaged preferential treatment of
applications from fishermen whose sons were to be
employed on the vessels, since this was felt to encourage
younger fishermen to stay in the industry and thus avoid
dependence on hired crews. The loan system also was
to be used to raise productivity in the fishery by extending
the fishing season. No loan was to be considered, unless
the applicant intended to work in the winter fisheries
(Burdon, 1956).
Encouraging co-operation:
To ensure more effective use of public funds in the
economic sense, and to attain the social objectives of
assistance, governments — in some developing countries
at least — seek to promote co-operative organizations
through which such assistance is channelled. Formation
of co-operatives may be stimulated through extension
activities, favoured treatment under taxation laws in the
allocation of financial assistance, granting of various
concessions in connection with employment practices,
etc. When, for instance, a few years ago, possibilities were
studied of establishing a mixed fishermen settlement with
Chilean and Mediterranean fishermen (to introduce
changes in the social and economic structure of the
fishing population in Northern Chile), the only form
under which organization of such a settlement appeared
to be feasible was a co-operative. Only co-operatives were
exempt from the provision of the country's Labour
Code under which no more than a small fraction of the
staff of any association could be foreigners. Chilean
co-operatives also enjoyed certain tax concessions
{Molteno, 1962).
Other development assistance given by government:
In most countries, governments take a major part in
•carrying out scientific and technical research for the
benefit of fisheries. The modest size of individual fishery
firms in these countries makes dependence on public
assistance in this sphere a matter of necessity.
In addition to providing services that tend to promote
the interests of the industry, the government uses its
legal power to protect consumers, producers, and the
resource. The consumer is protected against harmful
market practices affecting the price or quality of product
offered for sale. The entrepreneur may receive protection
against unfair — or too much— competition. Although
ordinarily associated with resource conservation objec-
tives, a fishing licence system may be operated to safe-
guard the economic interests of the fishermen or a group
of fishermen. In Japan, for instance, the maintenance of
catch quantities or profit margins per boat and the
protection of inshore fishermen against the competition
of trawler operators were among the declared aims of
licensing policies after the last war (Asia Kyokai, 1957).
Legal restrictions, fishing licence and import regulations,
may be enforced to discriminate in favour of domestic
and against foreign entrepreneurs, crews, boat builders,
and suppliers of requisites.
Sometimes the basic intent of protective regulation
may have become obscured as the result of changes in the
complexion of the industry since the time the laws were
instituted. Alaskan regulations limiting fishing boat
length are said to be based partially on resource conserva-
tion aims, partially on the desire to protect local fisher-
men. Chapman (1965) recently blamed antiquated State
laws in the USA for preventing the rational expansion of
sea fisheries off the Pacific Coast in the ways demanded
by modern economic conditions and national interest.
The regulations he referred to included licence refusals
for fish meal and oil operations, prohibition against
carrying trawls on vessels fishing in certain waters
(which made it impossible to fish sizeable hake resources),
against electronic fishfinders to locate — and against gill
nets to catch (on the high seas) — salmon, against trawls
to catch halibut, etc. Restrictions of this sort (in addition
to regulations limiting size or type of vessel), which
reduce technical efficiency, require re-examination to
determine whether they still serve the purposes for which
they were originally instituted, as well as whether they
have not become altogether obsolete in the light of
changed policy objectives (FAO/UN, 1962).
Welfare and safety regulations enforced for the benefit of
crews have a substantial impact on technology and the
economics of fishing operations. Laws fixing the minimum
size of crews may make it impossible to operate vessels
of a more economic size and may impose a degree of
labour-intensivcncss that impairs profitability. The
development of a fishery may be seriously hampered
where the law makes large units the only possibility,
while the finances and skills required for such operations
are not available (Netherlands Economic Institute,
1958).
In Poland, welfare policies aim at the attainment, on
fishing boats, of standards comparable to those usually
met in the merchant marine. In the Indo-Pacific Region,
in contrast, rigid enforcement of legislation applicable to
other classes of vessels has been held as seriously ham-
pering fisheries development. Such action reportedly has
resulted in impracticably high standards for the certifica-
tion of fishermen, coxswains and engineers; for safety
requirements related to number and type of life-saving
appliances to be carried on board fishing vessels; and for
harbour entry and clearance procedures (1PFC/FAO,
1958).
The character, amount, and costs of permits, licences,
and sundry "red tape" provisions controlling investment,
operation, landing and disposal of catches in some
Latin American countries are said greatly to handicap
entrepreneurial incentives and hold back development
of fisheries (various FAO technical assistance reports).
Private enterprise sometimes may be even more
severely affected, where government enterprise enjoys
exclusive privileges and franchises. Monopoly position, in
some instances, has been accompanied by technical
stagnation which could not continue under the spur of
competition.
Technological and economic difficulties have arisen
also through legal changes with international implica-
tions. These changes relate to fishing limits and agree-
ments on sharing of fishing grounds and catch quotas
44
negotiated between countries under international fishing
conventions. Extension of fishing limits by a number of
nations in recent years has frequently been named as a
cause for the reorientation of structures of, and policies
in regard to, fishing fleets of other countries which had
traditionally fished the waters now forbidden to them
(Report of the Committee. . . , 1961). Changes in the
salmon fishery of Japan imposed under renegotia-
tion of agreements with the USSR were reported to have
led to an influx of salmon fishermen into the tuna
fisheries and this, in turn, was said to have prompted
design of a new tuna longliner able to carry more
fish than previous types of the same size (LPFC/FAO,
1961).
Political factors, finally, also play a role in the avail-
ability, type, and amount of foreign assistance a country
may be able to obtain for the development of a fishing
industry as well as in regard to opportunities for im-
proving economic results of operations through exports
to hard currency countries.
TECHNOLOGICAL CHANGE
The rate of technological change influences obsolescence
and, consequently, the need for replacement of equipment
and the demand for equipment designers and Guilders.
Some attention, therefore, mus4 be paid to condi-
tions tending to promote or hold b:ick technological
change in the fishing secior. First, the qu< -.tions of what
are the means of bringing about, and what u»e the aims
of, technological change niu.i be answered.
Technological improvement in the fishing sector is
effected through changes in (a) craft and equipment used
on board, (b) methods of production (utilization of
equipment), and (c) organization of production.
The aim of technological improvement is development
of a new production function so that a greater quantity
of fish can be produced from a given total input of
resources (output-increasing innovation) or a given
quantity of fish can be produced from a smaller input
(factor-saving innovation).
Considerations affecting public sponsorship of techno-
logical change
For the economy as a whole, innovations arc all output-
increasing in the aggregate, since they free resources for
output expansion in other industries (even though the
innovation may result from a smaller resource input made
by the individual firm). In this sense, all innovations
stand to extend economic progress regardless of the
industry to which they apply, provided, of course,
opportunities exist of using the "Treed resources" in other
industries (Heady, 1949). In the long run, such oppor-
tunities will arise with progressive development; in the
short run, however, they may not be present. The latter
accounts for the frequently encountered opposition to
mechanization of fishing operations in developing
countries, because it displaces labour which is cheap,
abundant, and has no alternative employment oppor-
tunities in the immediate future. The situation is con-
trasted to that in developed countries where mechaniza-
tion in primary industries actually became a necessity
because of the labour needs of other industries (Sten-
strom, 1963 and 1964).
Public support for some innovations may not be
forthcoming because of market considerations. If the
aim of government policy is maximization of the total net
income of the fishing industry, innovations which increase
total output and decrease total cost, and which are related
to products characterized by inelastic demand, are likely
to be sponsored only if the decrease in total revenue (as
the result of the lower prices the market will pay for the
larger output produced) is smaller than the decrease in
total cost (and where net revenue, consequently, is
larger).
Government reluctance to lend strong support to
modernization programmes in certain sectors of the
fishery industry has at times, in some developed countries,
had its roots in uncertainty of whether the benefits ex-
pected from rationalization would be nullified by failure
of the market to absorb larger quantities at prevailing
prices.
In developing countries, the market obstacles may not
be related ;u much to price factors as to lack of processing,
transport and stoiagc means that would permit distribu-
tion of increased output over a larger area. Speaking of
experience in the Tndo-Paciiic Region in connection with
fishing boat mechanization, one expert a few years ago
counselled caution in introducing highly advanced
techniques on grounds that there was not always a
guaranteed market for the larger output that would
icsult from mechanization. For the same reason, the
possibility of using indigenous materials for nets and
ropes was to be given careful examination before a
decision to introduce synthetic fibres was taken (IPI;C/
FAQ, 1957). More recently, conditions in this respect, at
least, appear to have changed, even in comparatively
remote areas such as New Guinea. According to reports
on the Island, fishermen are increasingly being persuaded
to buy outboard motors on their own accord due to
"fairly satisfactory fish prices and the purchasing power
of the urban centres" (IPFC/FAO, 1963).
As compared with the special case of output-increasing
and cost-decreasing innovations under conditions of
inelastic demand, net revenue always increases if the
innovations relate to commodities the demand for which
is elastic or inelastic, as long as in the latter case the
innovations have output-constant and cost-decreasing
effects.
If government policy is primarily concerned about
maximizing total income (rather than total net income)
in the fishing sector, research might be directed primarily
towards increasing price elasticity in the market by
developing new product uses and not so much toward
promotion of technical innovations.
Welfare considerations, finally, may require govern-
ment attention to the likely impact of innovations on the
distribution of total income between interest groups or
between individual firms in the industry. New techniques
may transfer income between groups regardless of
whether total net income of the industry is increased or
decreased. The transfer may be of an intra-industry
nature (when the techniques for one commodity or
geographic region are improved beyond what applies for a
45
competing commodity or region). Also, the first few firms
which adopt an innovation will have greater incomes than
their competitors. This is true even if the innovation is an
output-increasing technique relating to a commodity
the demand for which is inelastic, since, in a competitive
market such as the one for the sale of fish on landing,
small changes in supply have a small effect on prices.
In the special case discussed above, where output-
increasing innovations under conditions of inelastic
demand may lead to a decrease in net revenue for pro-
ducers, there is the possibility of another type of income
transfer. The loss in the fisheries sector may be translated
into a real gain for the consuming economy, which,
under certain circumstances, may be a more important
public policy objective than assistance to a specific
sector of the economy (Heady, 1949).
Public policy considerations in regard to the introduc-
tion of technological improvements have been discussed,
both because in an industry where small enterprise is
still prevalent government has to play a key role in
research, and because the industry needs to know the
amount of public support it may be able to expect in
launching a rationalization programme.
Economic factors relating to technological changes at the
individual firm level
The individual firm will institute technological improve-
ments if they promise to increase its profits (or decrease
its losses), at least in the short run. Readiness to risk
capital on new inventions, new methods, etc., depends to
some degree on the general state of the economy and, to
some degree also, on trends in the output and input
markets of concern to the enterprise. In a rising economy,
producers are of an optimistic frame of mind and
willing to risk their capital on untried ventures. Yet,
where competitive pressure is absent and profits may
come easily even with continued use of traditional
methods, the incentive to innovate may not exist. As far
as conditions in the fishery industry itself arc concerned,
the generalization has been made that the optimum
degree of mechanization, which varies from fishery to
fishery, becomes higher as wage-rates increase, range
of operation extends, and capital becomes more easily
available (Morgan, 1956).
The larger items of new equipment and the more
radical new methods are, as a rule, first introduced in
developed countries, and there, by the larger firms with
the capital and skilled manpower resources to undertake
major investment. Generally speaking, types of equip-
ment that assure a high catch per day are of the high-
priced type. Their use presupposes considerable skills,
and wages are correspondingly high; in compensation,
they often permit a saving of labour that is not possible
with less advanced types of equipment (Netherlands
Economic Institute, 1958). Against possible savings in
total labour costs through reduced crew size must be set
the increased equipment, running and maintenance
costs connected with the installation and operation of
more complex machinery. Capital-intensive operations,
therefore, often require a large turnover to make them
worthwhile (Morgan, 1956).
If he has the choice of applying his capital for the
purchase of innovations that will have a direct effect on
output (e.g., fish-finding equipment) or for equipment
that tends to have a more indirect effect on factor cost
(e.g., crew safety devices), the entrepreneur will generally
give preference to the former. This accounts for public
intervention through promulgation of regulations on
safety requirements. Where the labour factor, however,
becomes critical, the effort may be both in the direction of
accelerated mechanization and of accommodating in-
sistent demand for increased crew comforts and safety.
The tendency to substitute, where specific inputs are in
short supply or excessively high-priced, is not limited to
the labour factor. Depletion of good shipbuilding timber
(coupled with the declining number of skilled shipwrights)
encouraged the introduction of the steel gillnetter in the
fisheries in the Great Lakes area (Calvin, I960). An un-
favourable price relationship between machinery pur-
chasing prices and catch prices is one of the most com-
monly given explanations for the slow pace of mecha-
nization. The disincentive effect of this ratio is felt the
more acutely, the lower the ability of the fisherman to
buy the engine or other equipment. Existing cost-
price relationships are also given as reason for the
limited possibilities of introducing the more costly
methods of preserving fish at sea: the overall profit-
ability of operations would compare unfavourably with
results from more traditional methods (Proskie in
Traung(Ed.), 1960).
Capital-intensive operations are handicapped also
by lack of mechanical skills and low standards of
maintenance which discourage investment in machinery.
Improvement of labour productivity, techniques, and
modernization of equipment, are considered the most
effective means of enabling the Newfoundland industry
to exploit its locational advantages to offset the ad-
vantages presently enjoyed by its foreign competitors
in terms of low wage and capital costs. Indirectly, the
locational clement had, in the past, worked against,
rather than for, the interests of the fishing industry,
because of relative difficulties of obtaining financing for
modernization of the small scale operations of New-
foundland fishermen against the much greater capital
outlays that were necessary from the start to support the
large operations based on distant ports of the European
nations exploiting the same fishing grounds (Copes, 1 961 ).
Introducing technological improvement
A study of the appropriate ways of introducing change
is a key element in any programme of promoting techno-
logical improvement. Too many generously endowed
modernization efforts have misfired because the likeli-
hood of resistance to change was either under-estimated
or altogether ignored in planning.
Much has been written about cultural and psycho-
logical factors accounting for such resistance. What has
been said above with regard to development, in general,
applies. In addition, there are elements which have a more
specific bearing on acceptance or resistance to technolo-
gical change.
Change is resisted, it is said, because it threatens basic
securities or does away with long-inherited traditions.
Resistance is that much stronger, the less well the
;46]
proposed changes are understood. Acceptance comes forth
more readily if persuasion rather than force is used
(Spicer (Ed.), 1952).
Basic securities are involved when the introduction of
new craft or equipment threatens to deprive crews of
their maintenance. The case of the opposition en-
countered by one of the major trawler firms in the
United Kingdom when it commissioned a vessel which
made substantial crew savings possible is fresh in mind
(Ross Group's Valiant). Industrialization of fishing
operations may mean loss of social status, loss of a skill
monopoly, or simply loss of freedom of action to the
independent h'sherman.
Great stress is placed on the essentially conservative
nature of the fisherman which makes him hold on to
uneconomic techniques and out-moded equipment,
even when he is not entirely unaware that they are
responsible for the miserable conditions in which he
lives. The poorer fishermen in Ceylon view any innovation
with suspicion and even hostility. They will seldom even
consider any deviation from the fishing methods their
forefathers had used for generations: "the introduction of
a more effective type of fishing gear or craft into a par-
ticular area is deemed to be destructive tampering with
the fishing in that area and the innovators run the risk of
bodily harm and damage to the innovation'" (i)c Silva,
1964). In Vietnam, too, the majority of the fishermen
are described as conservative and poor and unwilling to
abandon traditional equipment and metho ' (FPFC/h AO,
1964).
Aside from poverty, ^ 'graphic isolation, age and
lack of education, arc listed most frequently as the
underlying causes of the conservative attitude of fisher-
men. The resigned attitude of the older fishermen is
given some of the blame for the stagnation of coastal
fisheries in Belgium (Vanneste and Hovart, 1959). Geo-
graphic isolation and the static life in the small outports
of Newfoundland is said to be the reason that oppor-
tunities for improving facilities and techniques are not
grasped by the fishermen who "lack the necessary
initiative, knowledge, and imagination" (Copes, 1961).
Psychological elements play a role not only in con-
nection with the introduction of technological improve-
ment. They also constitute a limiting factor in the
extent to which such improvement can be carried out in
practice. The degree of centralization that goes with it is
thought to place a limit on automation in fishing boats.
Centralization of responsibilities tends to increase the
anxiety and strain on the skipper. One expert, conse-
quently, recommends that the equipment on the bridge
be restricted to what is absolutely necessary (Kddic in
Traung(Ed.), 1960).
Sociologists recommend that, where resistance to
change is related to the "innovators" and the methods
they use rather than to the specific character of the
innovation, the following questions, among others, be
investigated with care:
• Have the new facilities and/or methods been
introduced through the existing social organiza-
tion or have social organizations been set up
which conflict with those previously in existence?
• How are the innovators' purposes and ways of
behaviour regarded ?
• Has the maximum possible participation been
encouraged and allowed to develop?
• Have the cultural linkages been discovered and
utilized in introduction, i.e., has an effort been
made to relate the new element to some familiar
pattern? (Spicer, 1952)
The answers to these questions may reveal the mistakes
that have been made in introducing technological
change and may suggest ways of avoiding their repetition
in the future.
There is always a nucleus of leaders in a community
who may be prepared to do new things, to acquire an
engine, etc. If some members of this group can be
persuaded to adopt the new technique or buy the
equipment, the battle is half won. Where authority
is firmly vested with tribal chiefs, as in the earlier cited
examples of Tropical Africa, progress will be much faster
if the eo-nperation of the chiefs is enlisted and innova-
tions are introduced with their specific sanction. Where
fishermen's co-operatives are strong, as in Japan, the
facilities of the societies may be used with advantage. In
Japan, thus, the changeover to nylon nets by small
fishermen has been, to a large extent, accomplished
through the co-operative movement (Digby, 1961).
Co-operatives may find it easier than other agencies to
persuade small producers k> accept new ways of doing
things. Confidence exists, or at least should exist, between
the member and his co-operative. He docs not feel that
something is being forced on him by high pressure
salesmanship or recommended to him by someone with
theoretical rather than practical training.
Demonstration and encouragement of imitation are
the best means of ensuring participation of the com-
munity. "Seeing is believing", especially in cultures
where there is little understanding of abstract ends or
speculative results. If the benefits to be desired from the
institution of change are slow to materialize, it often
behoves to attach some form of satisfaction to the adop-
tion of new practices. This may take the form of praise,
privilege, or material reward. The pleasure which flows
from exercising a new skill also may have some influence
in arousing interest in new techniques (Mead (Ld.),
1953). Once the superiority of new techniques has been
practically demonstrated in a number of instances, a
certain momentum is created for its adoption among the
rest of the fishing population. This was observed, for
instance, in connection with the rapid expansion of
mechanized operations in Hong Kong, Malaya, and
Sarawak after the British colonial administration had
started to motorize fishing boats in these countries shortly
after the last war (Production of Fish . . . , 1954).
Frequently, however, it is necessary to start what has
been called a "revolution of rising expectations" to have
the fishermen copy the new techniques which have been
demonstrated to them. They must be persuaded that
they will be able to attain, by their own effort, a higher
standard of living. To this end, they often must be
taught to appreciate material rewards which have spurred
47
on the workers of successful industrial societies (Copes,
1961).
While it is not always possible to link new ways to the
past, care must nevertheless be exercised to avoid too
radical a departure from the familiar and to adapt the
pace at which change is introduced to the capacity of the
fisherman to absorb instruction. "Revolutionary changes
of craft and techniques may alarm and repel . . . (and)
too many changes all at once usually confuse the fisher-
man" (Beever, 1955).
Education is the key to progress in the long run. Even
where, as in Hong Kong, the fishermen have, through
motorization of their craft, made a great leap forward in
recent years, there is a need for continuous education on
proper engine installation, propeller selection, and main-
tenance practices (IPFC/FAO, 1964).
Training needs arc great also for the skippers, officers
and crews of the more industrialized operations, especially
as more complicated devices are being installed on
board. On the other hand, automation may reduce skill
requirements to a certain degree or for certain occupa-
tions. Also, some of the specialized operations on board
the larger vessels may be more closely related to occu-
pational specialities of land-based personnel. This may
have an impact on recruitment and the need for
specialized training.
Facilities for the training of government personnel
responsible for development and promulgation of new
technologies also must not be neglected, especially in
developing countries, where the fisheries administration
must be prepared to accept a pioneering responsibility
in this field.
Aside from taking an active part in the promotion of
technological improvement, governmentcan perform a use-
ful service by assembling and disseminating information on
inventions. A programme along these lines, it has been sug-
gested, might include preparation of forecasts for the uses of
specific inventions, assessment of their probable social
effects, proposals for speeding the removal of lags in
adjustment to inventions, as well as organization of train-
ing programmes and financial support facilities. Finally,
where serious barriers exist to mobility of fishermen,
whose skills have become obsolete, or who have lost
their livelihood as the result of technological progress,
governments will want to assume the responsibility for
facilitating transfer to other locations or occupations,
through underwriting the cost of transfer, retraining,
improving employment services, etc.
The impact of technological change on society and
on the complexion of fishing industries
Empirical research on the effects of technological
change is indispensable for the formulation of policies of
rationalization and modernization of industry.
Technical change may not consist merely in the modi-
fication of a branch of knowledge but in a changed
pattern of life and of the social structure as a whole. A
change in techniques may lead to shifts in the balanced
division of labour, may disrupt the pattern of relation-
ship between man and wife, father and son, may mean a
break with sustaining tradition which gives security
(Mead (Ed.), 1953).
Where desires and aspirations have limits, mechaniza-
tion may mean that the producer may work less. In
developing countries, the replacement of subsistence by
"cash crop" operations may, in the short run, result in a
lowering of nutritional levels, since the fishermen may be
tempted to concentrate on the cash crop, e.g., catching
shrimp for export. In countries like Burma and Thailand,
where more than one pound of polished rice per capita is
consumed daily, the vegetables, herbs, and fish products
which accompany the rice in the rural areas are believed
to make up for the nutritional deficiencies of a rice diet.
In Lower Burma, however, where a cash crop economy
flourishes, malnutrition is reported (Mead (Ed.), 1953).
At times, the impact on nutrition of increased pro-
ductivity is quite the opposite of that described above.
In Hong Kong, mechanization of fishing operations was
reported to have increased home consumption of fish by
the fishermen. The consumption of fish per head of
fishing population in "mechanized households" was
estimated to be about 20 per cent higher than the
consumption in "unmechanized households" (Szcze-
panik (Ed.), 1960). Advocates of a shift in development
efforts in the Colony towards deep-sea fishing in inter-
national waters envisaged a radical transformation in the
social structure of Hong Kong's fishing population in
addition to far-reaching technological changes and needs
for finding new methods of financing that such changes
would imply (Szczcpanik (Ed.), 1960).
Changes in the structure of fishery industries can also
be expected as the result of technological advances.
Again taking Hong Kong as example, mechanization of
fishing vessels was found to have led initially to a decrease
in processing operations. Before mechanization, a large
portion of catches was salted. Mechanization made it
possible to sell the bulk of the fish fresh. Expectations
were that, processing operations would be on the upsurge
again only when landings would exceed market absorption
capacity for fresh fish, (Szczepanik (Ed.), 1960).
Technical advances tend to increase the size of capital
requirements in fishing and break-even catch values.
They will account for vessels becoming obsolescent with-
in a shorter time and building costs becoming higher. As
the capital-labour ratio in fishing rises, the entrepreneur
expects the increased catch to result in a higher value per
unit of capital employed (Netherlands Economic
Institute, 1958).
With the change in the size of the average production
unit, changes take place in the pattern of the firm.
Growth in the size of craft employed will encourage
organization of larger fishery enterprises and may lead
to the gradual proletarianization of the fishermen
themselves (Morgan, 1956), which may encounter
resistance.
The increased financial burdens on the entrepreneur
may bring about changes in employment patterns.
The cost of the installation of engines, it has been ob-
served in the Thana District in India, produces a ten-
dency to employ more relatives who can be better relied
upon in sharing commitments and who are also more
favoured in sharing the benefits of mechanization. As a
result, mechanized teams employ comparatively more
relatives than sailing teams (Szczcpanik (Ed.), 1960).
[48]
Among other employment effects observed has been
the aggravation of recruitment problems. In Hong Kong,
motorization of fishing craft and the addition of simple
mechanical deck working gear in certain boat types —
such as power windlasses (with clutch operated warping
ends) in the pair trawlers, and capstans in the shrimp
beam trawlers — has made the better fishermen mo-e
selective in their choice of employment. For example,
skipper-owners of large longliners — these vessels require
a big crew complement to man the pairs of small fishing
sampans operated from the mother boat, and to hand-
haul the lines — now find it almost impossible to recruit
adequate numbers of men; many of the boats registered
as large longliners have accordingly been converted
into pair trawlers. The position is that the fishermen
prefer the better paid employment, and less arduous
work, either on shore or on the other more modern
classes of boats (IPFC/FAO, 1964). This development
has led to boats fishing farther afield, using labour-saving
deck machinery and synthetic fibre fishing gear, and
fishing throughout the year and working longer hours
than previously (IPFC/FAO, 1964).
The effect of mechanization on number of fishermen
employed and earnings has been commented upon in
many instances. Evaluations in terms of net welfare effect
arc, however, lacking and it is precisely at this objective
that recommendations for the assessment of mechaniza-
tion programmes made in recent years by such bodies as
the Indo-Pacific Fisheries Council have •timed.
There seems to be some evidence thai increased
industrialization of ope, :t: ions lends to affect remunera-
tion systems, with greater emphasis being placed on the
basic wage and less on settlement by share (Report of the
Committee . . . , 1961). On Pakistani trawlers, captains
and mates are paid monthly salaries (IPFC/FAO, 1963).
With mechanization, the number of crew members per
boat seems to have been reduced and the earnings of the
fishermen working on the mechanized boats increased.
This, at least, is the experience reported from India
(IPFC/FAO, 1963). Early experience with mechanization
in the country seemed to indicate thai capital invested in
non-mechanized craft provided employment for over
four limes as many fishermen as when invested in
mechanized craft (IPFC/FAO, 1958).
A 30 per cent increase in the real per capita gross in-
come of the fishing population in Hong Kong over the
1946/47-1958/59 period was crediled mainly to the
increase in catches brought about by mechanization,
which raised fishermen's earnings in spite of falling prices
(Szczepanik (Ed.), 1960).
Sharp increases in fishermen's earnings as the resull of
mechanization have been noted also in Pakistan. Over
a 3-4 year period, the mid-point of which was approxi-
mately in 1960, fishermen's earnings in the country
were reported as having almost doubled (IPFC/FAO,
1963).
The advantage mechanized fishing households in
Hong Kong held over unmcchanized households was
attributed also to disposal procedures and distribution
channel factors. The mechanized households were able
to sell through less expensive and more remunerative
channels, and were not as much at the mercy of middle-
men in their marketing operations as the unmechanized
households (Szczepanik (Ed.), 1960).
PROMOTING FISHERIES EXPANSION IN
DEVELOPING COUNTRIES
A basic issue in the formulation of policies for fisheries
expansion in developing countries is the determination
of the pace at which development should proceed. The
choice often is put in terms of a gradual improvement of
indigenous craft and methods and a more rapid growth
to be achieved with modern equipment fishing outside
the narrow coastal zones frequented by the traditional
fishery. A third possibility, of course, is parallel develop-
ment on both fronts.
Before more closely examining Ihese choices, ii may
be worth while to list some of the factors most frequently
cited, in discussions of development potential of specific
countries, as impeding or encouraging the growth of the
industry.
Factors affecting realization of development potential
On the market Mde, low purchasing power, consumer
prejudices, lack of market information (on the part
of consumers and marketing agents), lack or in-
adequacy of transporl and storage facilities, and restraints
of trade exercised by marketing agents, are among the
most prominent obstacles to expansion.
Conversely, among the strongesl inccnlives for rapid
development have been the discovery and exploitation of
export possibilities. Mexico and other Central American
countries as well as some countries in the Asia and Far
Fasl Region were able to starl profitable development
in the post-war years as the result of a flourishing
demand for shrimp and other luxury-type crustacean
products in Ihe Unilcd Slates and in other developed
countries. Menlion has already been made of Peru's and
Chile's fishmcal exports which account for the tremen-
dous expansion of the industries of these countries in
recent years. Morocco's fisheries development has
benefited, among other things, from the country's
nearness to European markels.
Klsewhere, fisheries development often offers the best
opportunity to diversify "one cash crop" economies. In
the Caribbean, for instance, the continuance of the
position of Ihc islands as a major world producing area
of sugar cane, it has been poinled out, may depend
on expansion of foodstuff supplies such as fish — which
do not compete for land wilh Ihc sugar cane (Morgan,
1956). In some countries, there has always been u strong
and stable demand for fish which is likely to increase with
increasing population pressure and unchanged poor
prospects of raising the productivity of limited and low
quality agricultural resources.
Sometimes failure to exploit fully the demand potential
is blamed on scarcity of resources in tradilionally fished
waters. More often, though, failure to expand can be
explained in terms of the "human" factors described
earlier, which accounts for stagnation.
Fisheries off the coast of Somalia are still at a low
level of development, although the waters are relatively
well stocked with fish. Development has been retarded
49
by the fact that the Somali are neither substantial
consumers of fish nor have been traditionally fisher-
men (Production of Fish . . . , 1954). The inhabitants
of the many small islands in the mid-Pacific are good
fishermen but have, for the most part, retained the
simplicity and small-scale character of operations that is
found in small communities in rather sparsely settled
areas (Morgan, 1956). Small scale operations elsewhere,
e.g., in India and other densely populated countries of
the Indo-Pacific region, still predominate, largely be-
cause of lack of capital and entrepreneurial talent. In the
Philippines, lack of qualified naval architects, technically
trained boatbuilders and marine engineers arc believed
to be among the principal factors retarding development
of deep-sea fishing (Rasalan et al in Traung (Ed.),
1960). Lack of co-ordinated planning and of foreign ex-
change for the importation of engines have contributed
to slowing development of mechanization in some
countries in the Far East (1PFC/FAO, 1958). In the least
developed areas, e.g., in New Guinea, the absence of a
drive toward economic improvement is still cited as a
factor in restricting progress. Living requirements are
limited, and the fisherman appears content that he can
attend to his immediate needs with the modest income he
derives from his occupation (IPFC/FAO, 1963). At times,
the lack of incentive to expand and/or improve operations
manifests itself also among the merchants who dispose
of the catches. This reluctance to increase turnover tends
to impose its own limitations on the fishing effort (Beever,
1955).
In Tropical Africa, where development in some coun-
tries has merely begun, all the above obstacles are en-
countered, with those relating to human motivation often
being the most conspicuous. In Madagascar, for ex-
ample, the following have been given as explanations
for the failure of industrial fishing ventures: insufficient
financing, inadequate fisheries experience of the pro-
moters, dispersion of limited resources over too broad a
range of activities, difficulties in finding suitable transport
and adequate market outlets and, above all, unsatis-
factory catch results because of the low productivity of
the fishermen (after receiving their pay, the fishermen
often did not return to work until they had spent their
money) (Couvert, 1963).
Considerations relating to scale and pace of development
Much has been written in defence of a cautious approach
to expansion and against doing too much in too short a
time and thereby risking wastage of a substantial part
of the limited resources available for development.
Mechanization, as seen in its wider aspect, is not an
end in itself. Mechanization is a means to produce more,
better and cheaper. Tn developing countries, where the
real costs of production are high and the prices the
producer can obtain for his products are low, the
technological improvements to be supported should
above all have a potential for increasing yields; less
emphasis need be given to labour-saving devices (Sten-
strom, 1963).
A slower pace makes it easier to adjust necessary
changes in economic and social structure to prevailing
conditions, customs and habits (Stenstrom, 1963). Too
ambitious steps forward in adopting new techniques
may place an unduly heavy burden on a developing
country's capital resources. Also, additional costs such
as those connected with expenses of storage, under-
utilized or idle vessel capacity, shorter depreciation
periods as a result of more rapid obsolescence, must be
reckoned with. If simpler methods are employed, the
equipment tends to be less costly, and less foreign
exchange may be needed. Thus, capital and foreign
exchange which tend to be in short supply in most
developing countries can be applied for other purposes
(Netherlands Economic Institute, 1958). The danger of
having all one's eggs in one basket is particularly real in
the more primitive fisheries where there is so little past
experience to assist in measuring the financial risk.
Heavy concentration of capital as, for example, in
costly deep-sea vessels, may not only prove com-
mercially unjustifiable, but may divert capital from more
essential, more immediate uses — such as the purchase of
small engines or better fishing equipment (Beever, 1955).
The argument for proceeding gradually, by first
improving and motorizing existing craft, in line with
opportunities arising under integrated development
planning, was well summarized at the Second Fishing
Boat Congress in Rome. Speaking on planning craft for
the developing countries, one participant expressed the
view that "development of improved fishing boats should
have a close relationship to the economic developments
in a fishing area. The utmost caution should be exercised
so that the fishing boat owner is not over-capitalized in an
effort to get the most developed boat. Thus, to some
extent at least, the development of the fishing boat of a
given area must be slightly behind that of the improve-
ment in other factors— the retail and wholesale market,
distribution, fish handling and storage, fish supply and
possibilities for exploitation. . . . These matters can and
must be explored . . . before any extensive development
can take place in the production of improved boats,
particularly where mechanization is concerned" (Chapellc
in Traung (Ed.), 1960).
The "gradual approach" was strongly criticized in a
paper submitted to the FAO Meeting on Business
Decisions in Fishery Industries in 1964. Motorization of
pirogues, West African experience had shown, according
to the authors, had proven economical only in cases
where hydrological conditions had made it impossible
to reach the grounds most suitable for handlining
operations. Traditional craft always would permit only
very limited development and, in some cases, the cost
of the engines could not even be amortized through
increased catches. It was a mistake on the part of
governments and technical assistance agencies to place
emphasis on motorization programmes instead of on
establishment of modern installations and methods
permitting large scale development. The latter would, of
course, require organization of enterprises with partici-
pation of developed countries contributing a major
share of the capital and the skilled manpower, and letting
the fish enter their markets as long as outlets in the
developing countries remained inadequate (Moal and
Lacour, 1964).
[50]
A survey mission recently carried out in connection
with plans to organize a UN Special Fund project in
Ghana concluded that there was scope for both
approaches, gradual improvement of the inshore canoe
fishery and larger scale trawling development (Crutchfield
and Zei, 1964). Natural conditions tended to place
economic limitations on what could be done at certair
locations. Market outlets, foreign exchange reserves.
availability of foreign capital and access to foreign
markets, had an influence on how far prospects for
large scale development could be realized. Last, but not
least, how far governments were prepared to go to
satisfy income, nutritional, employment, political and
economic independence, and other aims was a matter
of basic policy considerations and no one formula to
cover all combinations of aims could ever be devised.
51
Topographical Factors
in Fishing Boat Design
by K. Chidhambaram
Facteurs topogr&phiques intervcnant dans le dessin des bateaux de
peche
Les dessinateurs de bateaux dc peche doivent tcnir compte dc divers
61ements relevant dc la geographic, du climat, du littoral, du type de
peche, de I'dloignement des terrains de peche, dcs vents, des vagues,
des variations des marees, des saisons, des courants et des instal-
lations portuaires, factcurs qui varient tous d'unc region a 1'autre.
La communication etudie les divers types de bateaux de pcche et
leur evolution en fonction de ccs facteurs pour ce qui est de 1'inde,
oil Ton distingue six zones geographiqucs distinctes.
Factores topograficos en el diseno de las embarcaciones pesqueras
Los proycctistas de embarcaciones pesqueras deben tener en
cuenta factores talcs como la geografia, clima, linea de la costa,
tipo de pcsca, distancia a los caladcros, vientos, olas, variaciones
de la marea, estaciones, corrientes e instalaciones portu arias,
elementos todos ellos que varian entre las distintas rcgiones.
Respecto a la India, que cuenta con seis claras zonas gcograficas,
se describen los tipos de embarcaciones y su evolucion de acuerdo
con est os factores.
THE fishing boats of the world of all types, shapes
and sizes, represent the largest single collective
investment in the world's fishing industry. Upon
their efficiency of design and operation depend the econ-
omy of millions and the livelihood of a large number of
fishermen. Globally, designers attempt to produce the
ideal fishing boat. Opinion varies considerably as to what
constitutes the ideal vessel.
It is evident that the geographical location of a country,
and even the region within that country for which a new
type of mechanized fishing vessel is to be developed, will
have a considerable influence on the design. The broad
geographical or climatic classification of the country, such
as tropical, sub-tropical or temperate, will decide a
number of important features of the boat, such as general
arrangement, accommodation, ventilation and material
Tropical and sub-tropical countries generally border
oceans, where the warmer salt water encourages electro-
lytic corrosion of ferrous metal surfaces and devastating
attacks on timber surfaces by marine borers and fouling
organisms.
Geographical influences of wind and weather mater-
ially influence boat design. Countries with specific mon-
soon or other rain and storm seasons in the Indo-Pacific
region should carefully examine the nature of fisheries
that would be profitable during those seasons before
designing boats for fishing in or through such seasons
(fig 1).
Modern fishing vessels need not differ from village to
village as traditional designs do. By considering regional
features the extent of that region must be determined.
India, for example, may be divided into six distinct zones:
• Gujarat and Maharashtra States West Coast
• Mysore and Kerala West Coast
• Madras East Coast
• Andhra Pradesh East Coast
• Orissa and West Bengal States East Coast
• Andamans, Nicobar and Laccadives islands
Geography and hydrography of these areas have an im-
portant bearing on such characteristics as maximum draft.
Prevailing wind and sea conditions, wavelength, ocean
waves and tidal variations also influence design (Gurtner,
1963). Many places either have no natural shelter or
harbour, construction is too expensive, or water and
current prevent such construction. In these places fish arc
landed on the beach. Large and efficient beach-landing
boats have been designed. These beach fisheries often
assumed great economic importance.
Naval architects should consider the type of fisheries,
nature of fishing grounds, geography and other factors of
the coastline, communications, location, local conditions,
tidal variations and tidal currents. He must understand
also clearly those factors relating to fish abundance, and
availability of suitable boatbuilding materials and should
know the capabilities of boatyards and timber types
available in each region.
The evolution of different boat types in different Indian
coastal regions shows these boats have been developed
through trial and error and experience. Modifications
based on regional conditions have resulted in efficient
operation in these particular areas. These work well
because their ultimate design has taken all the above
natural conditions into account. In addition, their design
has been influenced by distance to the fishing grounds and
whether fish caught on distant grounds were to be fresh,
salted or cured fish,
Geographical and physical influences
Along shelterless surf-beaten coasts, craft had to be
developed which could be rigged and manoeuvred in
surf. For such areas in India's east coast the commonly-
used craft is the catamaran (fig 2), operating from open
beaches. Between Colachel and Cape Comorin, the coast
is particularly exposed and surf-battered throughout the
year without any landing place suitable for dugout canoes.
Some types of catamarans are operated over 100 miles off
52]
INDIA
PAKISTAN
FHASEROANJ
" -jSt'1 j HAJ_DlA *'
Kh.bjhe^jj* x PARADC'EP
VERS
/ fchu"
S AS SOON DOCK^fh&
BMF<:A
,Bf
RATNAolr-('
^EVAJANDA
V.JAV5JRG
MALVAN^
MURMAGAO""— J^G
KARWAR
CANNANORE
BEYPORE
^(MALABAFO \R
COCHIN
NEENDAKARA
MAJOR PORTS *nK«f »'SMiNi i-u"M • "
fQH DtEf' SFA TRAA.M«'i «"A'< »l
"Lb WITHIN TMI P0'«' **t *
^OM (\xX / l
COLACHEL\ LEEPURA^y/
^ /. (ienfral map of Indian fishing ports
north-east of Cape Comorin. The same types are used on
the surf beaches of Andhra and Orissa. Catamarans and
other simple craft have evolved from these conditions
along most of India's east coast. Catamarans in certain
regions can be fitted with outboard motors.
On surf-beaten coasts with sheltered bays, where wind
conditions are favourable and grounds are a little further
offshore, craft must be fast and able to negotiate swells
and rough seas. The Tuticorin types (fig 3) of canoe are
examples. Outrigger fishing canoes on this coast are
similar to those of Ceylon. Carvel-built boats, Rame-
swaram and Pamban machwas, are heavily-built boats
with low draft for landing on coral beaches. In river-
mouths and sheltered basins, larger boats have evolved.
Dugout canoes (Jig 4) are the common craft where
seas are not very rough most of the year and where fish
are abundant in shallow inshore waters. Dugouts fish
from open beaches with boat-seines and gillnets. The
evolution of the dugout is directly linked with geograph-
ical, wave and beach conditions and the availability of
large quantities of good timber along the Kerala and
Mysore coasts.
From Bombay to Ratnagiri the coast is generally rocky
and has harbours, sheltered bays and creeks. Fishing
[53
Fig 2. Catamaran commonly used on the east coast of India in
Orissa, Andhra Pradesh and Madras States where coasts are
surf-beaten and are without shelter
Fig 3. Tuticorin vallam used on the south coast of India in
Madras State where coasts are surf-beaten but shelter exists
Fig 4. Dugout canoe used mainly on the south- west coast of
India, in Kerala and Mysore States where seas are not so rough
and timber is available
grounds are distant. Here, the satpati type (fig 5) has
developed, and is considered one of the best fishing boat
types.
Along the Bombay coast, shoal water and sandy bottom
extend far out to sea. There is not a single sheltered
fishing harbour. The estuaries are silting fast and fish re-
sources are limited. Here, types similar to machwas are
used but they arc essentially different from the Arab types
of the north-west coast (fig 6).
Fig 5, Satpati type used along Bombay coast in Maharashtra
where rock v shelter exists
Fig 6. Karanja type used along Bombay coast in Maharashtra
where shoal water and sandy bottom extend far out to sea
In regions of great tidal variation and where large mud
flats or coral beds are exposed, the vessels are of shallow
draft, but large enough to negotiate tidal currents. Mach-
wa and Bedi boats of Gujarat and the Dhonies of Rame-
swaram are examples evolved in such conditions. The
north-west coast is arid, physically and climatically
closely approximating the Arabian coast. The predomi-
nant boat designs are characteristic of Arab influence
caused by trade contacts (fig 7).
Effect of distance and fishery
Design is influenced by distance to the fishing grounds
and whether the fishery is bottom, surface or pelagic. On
the Indian west coast, abundant shoaling fishes occur
near the coast at surface and in midwater. Here, boat
54
range is limited to inshore areas and speed and hold cap-
acity are restricted. Dugout canoes can be manoeuvred
easily here and they fish for sardine, mackerel, prawn and
other species inshore. Similar craft operate gill nets along
the Saurashtra coast for Pomfrets, Hilsa and other species.
Recently these craft have been fitted with outboard
motors to enable them to extend their range for catching
good quality fish.
. " ^"jRraHHHBBp^r- "*•«.*•&..* ^oammtf
Fig 7. Kutch type used on the arid coasts of the north-west of
India in Cujerat Slate
The fishing grounds on the sc»ith-east coast arc a little
further offshore. The design must reflect the speed with
which the boats should reach and return \'\ om the grounds
to marketing. The Tutieorin canoe and Kulia Phonic of
Ceylon are examples.
A larger boat is used on the north-west coast. The
grounds are distant from the home ports. Fishermen
follow the migration of fish in different seasons, some-
times going 300 to 400 miles (555 to 740 km) along the
coast. Moreover, iishing for Bombay Puck away from
the coast and in areas with strong currents, these craft
must be large and seaworthy with draft shallow enough to
enter tidal creeks and basins.
Fish-hold capacity need not be large where iish are
caught close inshore and can be landed fresh. In areas
where grounds are distant and in the opeti sea or where
fish must be processed at sea, boats must have adequate
space for cleaning, salting and storing dried fish and fish
products.
Pig N. Improved trawler designed hy an FAO naval architect
Fishing boat mechani/ation for India was studied.
Some factors considered were costs of marine diesel
engines and/or outboard motors, the economic return
from such boats and facilities available for landing catch,
servicing and maintenance. Catamarans sho\\ some
potential for outboard meehani/ation in selected centres
where grounds arc a little beyond the present non-mech-
anized range, where the quality of fish is good and the
price high. This may prove effective in Cape Comorin
areas.
On the south-west eoast, efforts were made to determine
the utility of an inboard or outboard engine on dugout
canoes. The engine power was not required for reaching
the fishing ground but for fishing operations. The out-
board was not powerful enough and the dugout had not
sufficient space to install an inboard engine of sufficient
power lor this purpose. But outboard motori/ution of
dugout canoes on the Saurashtra coast was effective and
economical, because Iishing grounds are rich and Iish
quality high, reali/ing good prices.
Larger craft on the north-west coast were suitable for
mechani/Mtion without much alteration, as they fished in
distant waters and subsequently used the power for sea
bottom fishing.
On the soulh-wesl and east coasts, the indigenous
boats could not be mechani/ed and so new designs had to
be developed. The Rameswaram or Pamban type machwa
was one type considered for mechani/ation. Allowing for
fishing conditions and types of gear, the designs had to be
de\ eloped to cover from 22 to 40 ft ((>.7 to 1 2.2 m). Gradu-
ally, the operational range had to be extended and the si/e
increased.
Influence of seasonal fisheries
Most of the non-mechani/ed indigenous craft have a limi-
ted range due to small si/e and lack of power. The cata-
marans, dugouts and the Tutieorin canoes normally
operate within 50 to 60 miles (c)0 to 1 10 km) from port.
They may operate from selected ports, following move-
ments of the fish.
In certain parts of the south Kerala coast, catamarans
during the pre-monsoon season cannot operate from the
open beach. They are transported to Vi/hinjom, which
has a sheltered bay and a protected shore. These cata-
marans operate from this base for some time even though
fishing is not possible from the open beaches outside.
In areas where boats follow seasonal fish migrations
and where boats arc big enough for proper fish handling,
the fishermen move with the fish for hundreds of miles.
Mechani/ed craft fishing for Para and Bombay Puck ofl
the Saurashtra coast move from the Bulsar area to Jaflra-
bad for Bombay Puck and to the Gulf of Kutch for Para
fishing, about 600 miles ( I , I(K) km) from their home ports.
Large-scale movement of fishing boats following the fish
is possible, because of the si/e and types of boats and the
similarity of coastal conditions, tide and current. But these
movements are restricted to the coast and not to deep-sea
fishing.
Availability of boatbuilding material
When developing the fishing craft in different regions one
of the primary considerations besides the geographical.
55
physical and fishing conditions, is the availability of
suitable timber for boatbuilding in large quantities in the
vicinity. Dugout canoes were developed on the Malabar
coast, where ample timber is available. As coastal traffic
developed, these boats found their way to most of the
countries bordering the Arabian Sea. With the increasing
cost and the difficulty of obtaining timber in quantity and
the effort made in developing new designs, the use of the
dugout in other parts of the country has been declining
gradually. Catamarans are found in areas where soft wood
is available locally or nearby. The availability of good
quality teak in the north-west forests resulted in the large
north-west coast vessels.
For non-mechanized boats, the traditional method of
preserving the timber from borers was to apply fish oil
and, to some extent, lime. When boats were mechanized
and had to remain in water for a longer time, they needed
copper and aluminium alloy sheeting. In areas of consider-
able tidal variation and complete exposure at low tide,
there was no need for copper sheeting. Protective meas-
ures are still restricted to periodical application of lime
and wood resins, as in the case of the large north-
western boats.
Influence of harbour development
As fishing becomes more intense, the need arises for
harbours with berthing, landing distribution and servi-
cing facilities to replace beach landings.
Harbours can be developed only in certain places.
These will be determined by their distance from fishing
grounds, their natural shelter, communication facilities
and other factors. With harbours, the sizes and designs of
fishing boats could be increased and improved for large-
scale fishing. Such facilities normally lead to the develop-
ment of standardized fishing boats for working different
types of fisheries and in various grounds. Such standard-
ization also leads to economic and efficient operation.
Some of the local factors relating to shore and tidal con-
ditions do not greatly influence designs of large fishing
boats operating from harbours.
CONCLUSION
Physical and geographical conditions, coastline, nature
of the fishery, distance to grounds and species of fish are
all factors that have influenced indigenous boat designs.
A correlation between particular designs and physical
coastline or regional features has been carried out for
India. Overlapping was not significant. The prevalent
indigenous designs of fishing craft are the same today in
these regions as a hundred years ago. Each has its own
boat types; its own characteristics of weather, climate and
coast formation.
On the north-western coast, where the physical and
climatic conditions are similar to the Arabian coast, Arab
boat designs are characteristic. In the Bombay sector,
these boats are mixed, but Indian in type. In the indented
coastal region south of Bombay to Mangalore, the Arab
influence is replaced by indigenous and Polynesian types.
This is reversed partially on the Malabar coast, where the
dugout designs predominate. East of Cape Comorin,
Polynesian and indigenous boat types have held their own
successfully against foreign influence. The indigenous
designs of catamarans and canoes are well marked and
characteristic.
Many boats in India, especially those from the north-
west coast, are well developed from the modern naval
architectural point of view. They could still be improved
by sharpening the stern posts, modifying the distribution
of displacement, mechanical propulsion, rigging for
handling improved types of fishing gear, providing insula-
ted fish holds and by improving the general arrangement
to increase the working efficiency of the crew. These boats,
with slight modifications, could be mechanized. The
Pamban-type machwa form the basis for development of
designs for small mechanized boats on the south-west and
north-east coasts. New designs developed in India with
FAO assistance took these factors into consideration
(fig 8).
A small number of American launches have been de-
veloped by trial and error, to meet the demands of local
conditions, which are so rigid that boats must be efficient
to survive. There is, already, a very high level of design,
but it can be effectively improved if it is done with a work-
ing knowledge of the local physical and economic factors.
Some of the North American types of boats such as the
Gaspc boat, Cape Island boat and Sharpe launch, have
been developed according to beach conditions and/or
types of fishery (Chapelle, 1955).
In different parts of the world, boats are modified
gradually through experience gained in their ability to
work different types of gears in different regions. Fisher-
men who are not boatbuilders and have no knowledge
of naval architecture are reluctant to change designs with-
out being sure of results.
There are still too many unknown factors in Indian
fisheries to predict effectively the future development of
different boat types. Development will be directed grad-
ually on the basis of experience gained here and elsewhere
and on the operation of newly-introduced boats rather
than by suddenly introducing complicated and expensive
types of fishing craft.
56]
Techno-Socio-Economic Problems Involved
in the Mechanization of Small Fishing Craft
by At sushi Takagi and Yutaka Hirasawa
Problvmes techno-socio-cconomiqucs de la mccanisation dcs pet its
bateaux de pcche
La flottille dc pcche japonaisc, composec il y a 60 ans d'cnviron
420000 bateaux non motorises, comptc actucllcmcnl a pen pres
200 (XK) bateaux a motcur. La molorisution dc la flottille nc
constitue qu'un aspect de la modernisation, puisque meme les
bateaux de petite taille disposeni egalement aujourd'luii de materiel
electroniquc tel que radios ct deieeteurs de poisson. Le Ciouverne-
ment juponuis a impose de severes limitations tant a la taille dcs
bailments qu'a 1 "effect if total et au tonnage des bateaux pratiquant
certaines peches. C'ette rcglementation affccte par exemple \<x
flottcs travaillant le thon, Je suumon v.rt la inuie. It- maquereau, ainsi
que les baleiniers et les chuluiicrs. I.es restrictions apportees a la
taille des batimcnts out incite les architectes navals a sVfTbrccr
d'augmenter au maximum la capacite des cales a poisson. La
penurie de muin-d'ocuvrc pour la pecht, causee par IVssor rapide
d'autres industries, devra etre compensee pai une mecani.>ation plus
poussee.
Prohlemas tecno-socio-ceonoinicos de la niecani/.acion de pequeAas
embareaciones pcsqucras
l.n 60 anos la flota pesquera japi nesa ha pusuJo de unas
420 (HK) embareaciones sin motor s 200 (KH) unidades rnotori-
las cmhaicii lies mcnores no solo cstan
ahora dotadas dc inoli ', sino tambii .le equipo elcctromco, como
radio \ locali/adoics d bancos de p- do. I I ( iohicrno japones ha
impucsto npurosas Imitaciones al tamano dc los barcos y al
niimero total y tonclaj dc los dcdicados a una pesca determinada.
Por c.iempio, las 11 .lei atun, el salmon y la trucha, la caballu, la
ballena del ai astrc, estan eslnctamente reglamenladas. Las
restnccioncs iinpuesias al tamaho do los barcos han ohligado a los
arquitectos navaies :; hacer eiionnes csfuer/os para elevar al
maximo la capacid:(d dc las bodegas. I I rapido desarrollo dc las
demas industrias na reducido la mano de obra pescadora. Para
contrarrestar csta pcrdida en bra/os habra que mecani/ar mas las
opcracioncs.
MKCHANIZATlOx' of the Japanese fishing
fleet began with trawlers and whalers around
1900. Before mechanization, 420,000 Japanese
rowing or sailing vessels produced 1,000,000 tons of
fish annually. Fishing methods were primitive. The
catch was not enough to supply necessary animal
protein to the nation and mechanization started as a
Government policy. A few firms were established to
operate trawlers and whalers as mechani/ed fleet units,
and these types of vessels were successfully mechanized
under this system. Coastal craft were mechanized,
individually. Mechanization gave fishermen access to
better, but more distant, fishing grounds and the size of
vessels increased. An increased number of crew for
larger vessels could easily be found, because the popula-
tion of fishermen increased as a part of the explosive
increase of national population, caused by the rise of
living standards through industrialization of the country.
Nowadays, the fishing industry faces problems of
conservation of fish resources, exploration of new
markets, and acquisition of necessary labour, as well as
maintenance of a reasonable profit. These complex
problems lead to a conclusion that fishing operations
should be restricted to a limited number of the most
efficient boats.
MECHANIZATION OF SMALL FISHING CRAFT
The progress of mechanization in the past ten years is
shown in fig 1 . The steady progress reflects the fact that
there was a limit on the speed of mechanization. This
limit was set by the size offish resources and the market,
500,
oo i
100;
*«^ ••**
** •"*
r /
total r
• runbtr of pow«r»d boat*
numbw of powarvd boot*
undtor fW« torn
W W w ** in; i*' m M tm tm ** m m.- w ** mm. mt ** tmmmi *u *\
/iff J. Mechaniztiiion t»f Japanese fishing biuii.\
and if mechanization progressed beyond the limit, the
whole fishing fleet might have faced bankruptcy. In some
cases, however, mechanization of fishing vessels was
done simply to retain the crew, as crews tend to move to
better boats. This indicates that the problems arc not
only economic but social.
TABU 1
Mechanization
of fishing boats
under 5 C;T
Year
Below 1 CiT
/ .* r;y
.? 5 ar
Total
<}) 1953
(2) 1958
(3) 1963
23,412
31,695
43,840
67,798
85,320
99,858
15,031
19,054
23,986
106,241
136,069
167,684
Ratio (2)/(I)
Ratio (3)/(l)
1.38
1.87
1.26
1.47
1.26
1.60
1.28
1.58
Note: About 10,000 fishing craft equipped with outboard engines
are excluded from the above table.
57
TABLE 2
Change of type of engines in powered fishing boats under 5 GT
79.5.?
1958
1963
Ratio
(/)
(2)
(3)
(2)1(1)
(3)1(1)
0-0.9 GT
D
364
4,291
20,296
11.78
55.75
H
8,065
807
384
0.10
0.05
E
21,967
26,597
23,160
1.21
1.05
1 .0 2.9 GT
D
5,450
26,031
70,551
4.77
12.97
H
13,219
12,113
4,768
0.91
0.36
r
49,129
47,176
24,539
0.96
0.49
3.CM.9 GT
D
2,251
5,930
16,910
2.63
7.56
H
9,295
10,571
6,047
1.14
0.65
t
3,485
2,553
1,027
0.73
0.29
Note: D - diesel engine; H hot bulb engine; E - electric ignition
engine
Most of the vessels over 5 GT in Japan have already
been mechanized with diesel inboard engines. Therefore
the non-powered vessels in fig 1 are vessels under this
size and the number of such non-powered craft is still
half the total number of the whole fleet. The progress of
mechanization therefore, is best observed when fishing
craft under 5 GT only are discussed (table 1 ).
Types of engines produced in Japan are diesel, hot
bulb and electric ignition engines. Electric ignition
engines are most popular among small vessels under
5 GT, followed by hot bulb engines and diesel engines.
In these ten years, diesel engines increased for all sizes of
vessels, 0 to 0.9 tons, 1.0 to 2.9 tons and 3.0 to 4.9 tons.
The hot bulb engine increased only for the range 3.0 to
4.9 tons, and electric ignition engines for the ranges 1.0
to 2.9 and 3.0 to 4.9 tons (table 2). Table 3 shows the
average size of a family fishing unit, while table 4 gives
the average balance sheets for these units. Table 4 shows
that fishermen with non-powered vessels earn much less
than fishermen with powered vessels.
The percentage of earning from fishing is also less for
fishermen with non-powered vessels and therefore they
must have other incomes from other businesses. It is also
indicated that the larger boats earn more. However, the
heavy initial investment for powered vessels, especially
for larger vessels, should not be overlooked, and their
mechanization is often not justified.
Investment in equipment needs control to avoid over-
investment, as with other industries. The tremendous
number of family-owned vessels, however, makes such
control difficult.
LOCATIONING OF VESSELS AND
COMMUNICATION
Before radios were installed in fishing vessels, distant-
water fishing was extremely risky. Now, distress calls can
be made, medical advice for sick men obtained and bad
TABI L 3
Average size of a family fishing unit
with
with powered boats
non-powered boats
under 3 GT
3 5 GT
1961
1962
1963
1961
1962
1963
1963
family members on board
1.0
0.8
1.0
1.6
1.6
1.5
1.8
Total family members
5.2
5.0
4.9
6.1
6.0
5.8
6.3
Fishing boats
non-powered No.
1.1
1.1
1,2
0.3
0.3
0.3
0.3
GT
0.8
0.8
0.8
0.2
0.2
0.2
0.2
powered No.
—
1.0
1.1
1.1
1.1
GT
—
-
• -
1.5
1.7
1.6
3.7
TABLE 4
Balance sheet for average si/.e of a family fishing unit
Initial investment
Total annual earning
By fishing income (a)
running cost (b)
earning (a) (b)
Annual fish catch (ton)
Labour for fishing per
year (man-hours)
1961
165
(462)
374
(1,046)
159
(447)
46
(128)
113
(319)
2.59
867
with
non-powered boats £ ( $ )
1962 1963
180 197
(506) (554)
369
(1,032)
244
(683)
81
(228)
163
(445)
6.08
865
533
(1,490)
267
(747)
88
(247)
179
(500)
5.05
1,394
1961
510
(1,420)
441
(1,233)
533
(1,489)
250
(700)
283
(789)
7.36
2,132
with powered bouts £ (%)
under 3 GT
1962 1963
620 645
(1,700)
637
(1,780)
652
(1,830)
316
(886)
336
(944)
7.63
2,754
(1,800)
633
(1,770)
703
(1,969)
322
(902)
381
(1,067)
7.63
3,610
3 5 GT
1963
1,370
(3,825)
874
(2,445)
1,595
(4,470)
966
(2,705)
629
(1,765>
20.27
6,517
58
weather avoided by using the radio. The radio gives
information about fishing conditions on various fishing
.grounds, sea water temperature and even market prices
of fish in different fish landing places.
Japan has an exclusive radio network for fishermen.
Such a system was first established in 1921 and special
frequencies allocated for fishing vessels. Radio shore
stations were opened in fishing ports. In 1933 radio
equipment became compulsory for all fishing boats over
100 GT. By 1942, 1,300 fishing boats had radios. After
the war, radio telephones were installed on small off-
shore fishing boats. Later VHF (very high frequency)
radio telephones were installed aboard smaller boats
operating in the coastal area. Table 5 shows the number
On the other hand, boats operating in coastal and
pelagic fisheries are equipped with radio telephones with
MW/SW bands of 10 wa't to 1 kW capacity, depending
on the distance between shore and fishing grounds.
Operators of this type of telephone have to complete a
vocational training course of at least 40 days. Telegraph
operators of lower grade have to have a 6-month training
course. These two types of operators should have a
licence.
Navigation equipment, such as direction finder, radar,
loran and facsimile are installed aboard ocean-going
boats. Radio buoys arc also popular. More than 9,000
of such buoys are now in use to locate killed whales,
longlincs and drift nets. These radio buoys are also put
aboard inllatable life rafts.
TAULI 5
Fishing boats with radios
Rreakilwn 196*1
GT
1961
Wb4
Telegraph
Telephone
0 4
656
987
1,154
1,561
0
I,5M
5 9
563
842
1,049
1,322
1
L321
10 19
2,791
2,931
2,8(X)
2,687
13
2,674
20-49
3,499
3.779
4,(K)4
3,873
526
3,347
50-99
3,267
1,522
3,467
3,427
1,707
1 ,720
100 499
905
927
1,071
1,276
1,217
59
5(K) and
177
250
157
237
237
0
over
Total 11,858 13,238 13,702 14. ''K.I 3,701
10,682
of radios installed in fishing boats from 19ol to 1964. As
VHP radio telephones become popular there will be a
continuous increase in the number of fishing boats under
10 GT equipped with radios. The VHF telephone has a
27-megacycle band and an output of 1 to 10 watts. Now
about 3,900 vessels are equipped with such VHF radio
telephone sets.
Some of the boats in table 5 have VHF telephones as an
auxiliary to a larger capacity radio for pelagic fisheries.
One disadvantage of VHF is thai it cannot cover a large
area. There are 217 shore stations used exclusively for
fishing vessels, 108 of which serve those boats with
VHF radios. The licence to operate VHF radios aboard
fishing boats, and licence to operate VHF telephone sets
is obtained by attending a vocational training course of
about one week.
DETECTION OF FISH
Fish finders are used extensivel} on board fishing boats
regardless of si/e. and were originally simple echo
sounders to measure depth. Later on they were used
on skipjack pole-and-line vessels to detect reefs where
fish schools were found. From about 1947, fish finders
were installed on purse-seiners to locate fish schools. Fish
finders became very popular after the Fishing Boats
Research Laboratory made a sytcmatic analysis of
Ircqucncies from 14 to 200 kc/s and made several models
tr cover shallow waters to deep seas. With visual
information on hand, the fishing activity has become
extremely efficient. Table 6 shows the numbers of fishing
vessels with fish finders. Some vessels have two or more
units.
TAIII I 6
Fishing boats with fish tinders
0 5
5 9
10 20
20 50
50 100
100 2(K)
200 500
500 and over
Total
1,729
971
2,W
2,267
1,838
311
269
60
9,8.17
2,652
1,249
2,6.12
3,04S
2.165
309
441
110
12,803
Claxs
3GT
5 GT
15 GT
30 GT
Hull
420
(1,175)
725
(2.030)
2,400
(6,720)
5,500
(15,400)
TAIII.I-. 7
Comparison of boatbuilding costs with electronic equipment
ilngine
440
(1,230)
640
( 1 ,790)
1,500
(4.200)
4,200
(11,750)
250
Rtulit
(1)
580
1,625)
2(K)
(560)
7(K)
(1,960)
costs £ i
Hsh
'(2)"
150
(420)
150
(420)
150
(420)
3(K)
(840)
(1)
1.010
(2.8.10)
1,515
(4.250)
4,5(H)
11,330
(31,250)
(2)
(3)
0.15
0.10
0.80
0.09
59
TABLE 8 — continued
(2) tuna longline fishing boats
(a) L 12,350 13,250
ft:< (350-375 nrj)
Period and no.
of vessels involved
GT/LBD ft3
nr1
1930-1940
(1)
0.00730
0.258
1941-1950
(0)
1951-1954
(14)
0.00755
0.267
795.5 795*
(33)
0.00750
0.265
1959-1963
(13)
0.00768
0.271
hp'LBD ft:'
m:i
0.0154
0.546
—
0.0201
0.711
0.0232
0.818
0.0265
0.936
NC/LBD ft-1
m'1
0.00139
0.049
0.00181
0.064
0.00181
0.064
0.00181
0.064
hp'GT
2.11
2.67
3.09
3.45
1 H/LBD
0.244
—
0.286
0.266
0,259
FO-LBD
0.071
0.103
0.101
0.094
INK)
3.43
-
2.79
2.62
2.75
K) hp ft-'
nv'
4.5V
0.130
—
5.08
0.144
4.38
0.124
3.53
0.100
A, LBD ft:<
m:'
0.00860
0.304
-
0.00930
0.328
0.0102
0.358
0.0104
0.367
Ad/LBD ft'
nr1
0.0138
0.487
-
0.0172
0.607
0.0179
0.630
0.0175
0.619
(b) L- 13,250 14,200
ft:' (375-400 m3)
Period and no.
of vessels involved
1930 1940
(0}
1941-1950
(4}
1951 1954
(7)
1955-1958
(25)
1959-1963
(4)
GT/LBD ft3
m:i
—
().(X)725
0.256
0.00731
0.258
0.00722
0.255
0.00737
0.260
hp/I.BD ftr'
nr1
—
0.0176
0.622
0.0192
0.677
0.0228
0.807
0.0256
0.903
NC/LBD ft:i
m:i
—
0.00221
0.078
(UK) 162
0.057
0.00167
0.059
0.00170
0.060
hp/GT
2.43
2.63
3.16
3.46
FH/LBD
—
0.268
0.265
0.275
0.254
IO/LBD
-
0.075
0.083
0.104
0.085
FH/FO
—
3.56
3.19
2.65
2.99
FO/hp ft3
my
__
4.27
0.121
4.30
0.122
4.52
0.128
3.22
0.094
Ai/LBD ft:'
m3
—
0.0102
0.358
0.00910
0.321
0.00950
0.335
0.0102
0.360
Art/LBD ft3
m:'
—
0.0178
0.628
0.0161
0.566
0.0172
0.606
0.0172
0.607
39-GT type wooden skipjack and tuna boats
These types of vessels appeared in 1957 when the
Government regulation excluded tuna boats under
40 GT from the licence restriction. One reason why
vessels excluded from the fishing licence system were built
in number was due to the system of transferring the
licence from one individual to another. Because of the
limited number of fishing licences, a fisherman who
wished to add a vessel to his own fleet had to purchase
the licence for such a vessel from another fisherman.
The price of the licence therefore once became £360
($1,000) per GT. This made the initial cost of licensed
vessels almost double that of vessels out of the licence
system. Another reason was the fact that such a small
vessel as 39 GT could still find fishing grounds for
fairly profitable operation.
Fifteen hundred such vessels have been built over a
short period. Lack of safety was a great difficulty in this
type of vessel. The Pacific around Japan can be rough in
winter and this type of boat figured prominently in
many disasters. The story of 39-GT tuna boats may be
summarized as follows. A fisherman found this size of
62]
TABLE 9
Change of particulars of 95-GT type wooden skipjack and tuna
boats
(1) skipjack/ tuna pole-and-
(a) LBD 12,350 13,250
•line fishing boats
ft •' (350-375 m-')
Period and no,
of vessels involved
1930 1940
(5)
IV4I 1950
(3)
IV5I IV 54
CD
(15)
(ft)
LBD ft'
m'
1 2.950
367
1 2.950
367
12.980
368
12.880
365
12,910
366
GT
98.85
93.96
98.36
98»1
98.93
NC
47.4
60.0
55.8
49.2
49.6
hp
1^7
207
267
29<>
338
FH fVJ
nr'
3,035
86
3.035
86
3.035
86
2.860
81
3.110
88
FO ft'
ma
670
19
742
21
8X2
25
847
24
812
23
A,
119
108
12>
130
132
Art
210
206
214
209
225
(b) LBD 13,250 -14,150
ft'1 (375 4(X) nr')
Period and no.
of vessels involved
1930-1940
(12)
1941 1950
(12)
IV5I IV54
19^^ I9W
\5)
(4)
LBD ft3
13,540
384
13,590
385
13.450
381
13,470
382
13,510
383
GT
98.01
98.22
99.18
99.36
99.42
NC
56
51
52
47
48
hp
200
231
268
322
343
FH ft3
m3
3,140
89
3,250
92
3,070
87
3,140
89
3,280
93
FO ft3
m3
812
23
742
21
812
23
883
25
883
25
A,
116
117
128
138
142
Ad
213
214
215
236
232
63;
TABLE 9 — continued
(2) tuna longline fishing vessels
(a) LBD -12,350 13,250ft3
(350-375 m3)
Period and no.
1930-1940
1941 1950
1951-1954
7955-7955
1959-1963
of vessels involved
(/)
(0)
(14)
(33}
(13)
LBD ft*
12,970
—
12,970
12,870
13,000
m3
367
367
364
368
C,T
94.71
—
97.91
96.57
99.96
NC
18
—
23
23
24
lip
200
261
298
345
FH ft3
3,140
3,710
3,430
3,360
m:l
89
105
97
95
FO ft3
917
_
1,340
1,305
1,235
ma
26
38
37
35
A!
111
121
130
135
A,
178
• ~
223
230
228
(b) LBD- 13,250-14,150 ft'
(375 400 m3)
Period and no.
1930-1940
7947 1950
1951-1954
1955-1958
7959 796.?
of vessels involved
(0)
(4)
(7)
(25)
(4)
LBD ft3
13,630
13,650
12,980
13,480
m:l
386
387
368
382
GT
....
98.81
99.69
98.52
99.50
NC
—
25
21
23
23
hp
—
240
262
312
345
FH ft:i
3,640
3,600
3,740
3,430
m3
103
102
106
97
FO ft3
1,023
1,160
1,420
1,165
msl
29
32
40
33
A!
—
138
124
129
137
Ad
,-.._
242
218
239
232
[64]
TABLE 10
Change in design parameters of 39-GT type wooden skipjack and
tuna boats
(1)
tuna/skipjack pole-and-line fishing boats
Year ami no. of
vessels involved
7957 1958
79.59
U)
I960
1961
(10)
796:
(9)
79ft.<
(4)
1964
GT/LBD ft:J
m:*
—
0.00638
0.226
0.00633
0.224
0.00630
0.223
0.00638
0.226
0.00641
0.227
hp/LBD ft:'
m3
—
0.0245
0.86S
0.0276
0.975
0.0283
1 .053
0.0337
1.192
0.390
1.382
NC/LBD ft;1
-
0.(X)6()5
0.214
-
0.00574
0.203
().(K)586
0.207
().(H)506
0.179
0.00515
0.182
hp/GT
_ _
3.84
4.32
4.71
5.27
6.07
I;H/l.BD
-----
0.286
0.25<
0.267
0.270
0.278
FO/LBD
0.038
0.050
0.051
0.05t»
0.059
FH FO
7.53
5.07
5.(H)
4.82
4.68
FO/hp ft'
m1
--
1.518
0.043
1.835
0.052
1 .6^5
0.048
1 .625
0.046
1.518
0.043
ArLBD ft;)
nr'
0.010
0.354
0.0110
0.39)
o.oi i:
0.397
0.0115
0.407
0.0112
0.396
A../LBD ft3
PIT*
.....
0.0175
0618
0.0193
0.683
0.0168
0.598
0.0171
0.603
0.0192
0.678
(2) 1(
Wl,nc,s
Year and //<>. of
vessels involved
(9) (Li)
UV)
(64)
7967
(ft.?)
IV6?
(//)
1964
(15}
GT/LBD ft'
O.OOittto 000662
0.241 0.234
0.00667
0.236
().(K)633
0.224
0.00622
0.220
0.00630
0.223
0.00627
0.222
0.00627
0.222
hp'I.BD fl:i
ru'
0.01 SO 0.0213
0.637 0.755
0.0254
0.898
0.0250
0.884
0.0266
0.942
0.0280
0.991
0.0312
1.102
0.0334
1.180
NCLBD ft1
0.00294 0.00297
0.104 0.105
0.00294
0.104
0.00280
0.099
0.00280
0.099
().(H)283
0.100
0.00280
0.099
0.00269
0.095
hp/GT
2.67 3.50
3.78
3.95
4.29
4.46
4.95
5.32
\ H/l BD
0.274 0.293
0.278
0.258
0.246
0.256
0.217
0.223
FO LBD
0.059 0.077
0.080
0.080
0.075
0.076
0.068
0.079
FH FO
4.64 3.69
3.48
3.21
3.27
3.35
3.20
2.83
l-O/hp ft:<
mri
0.00257 0.00266
0.091 0.094
0.00252
0.089
0.00257
0.091
0.00226
0.080
0.00215
0.076
0.00175
0.062
0.00190
0.067
A, /LBD fln
().(K)992 0.00966
0.351 0.342
0.01 II
0.392
0.0109
0.385
0.0108
0.384
0.0110
0.389
0.0115
0.409
0.0117
0.417
Art/LBD ft;'
0.0163 0.0176
0.588 0.623
0.0188
0.664
0.0185
0.654
0.0182
0.645
0.0186
0.659
0.0185
0.655
0.0188
0.666
boat could be profitable and many others followed his
idea but incorporated a lot of additional requirements
in design. The first fisherman could not compete with
others, as the design of his boat became out of date,
and thus he was forced to follow the new trend. The
majority of these vessels were extremely unsafe because
of the fishermen's demands for maximum hold space.
Table JO shows how the design of these boats has been
changed.
GT/LBD: This parameter has not changed in the past
seven years, indicating that the principal dimensions of
this type of boat have remained constant.
hp/LBD, hp/GT, FO/LBD, FII/LBD: These para-
meters have conspicuously increased, indicating that
fishermen wanted to increase engine output. Increase of
horsepower means increased fuel oil tank capacity.
Need for better refrigeration and insulation systems for
extended fishing trips also decreased hold capacity.
In spite of the fact that the fuel oil tank capacity was
increased, the amount of I'uel oil was often not sufficient
65;
and a system of carrying fuel oil in a huge plastic bag
in the lish hold was devised. This led to unsafe vessels
due to movement of liquid in the Jish hold.
A/LBD: The light weight of the boats increased by
15 per cent in seven years. The weight of the departure
condition also increased by 10 per cent over seven years.
Influence of restriction on the design of vessels in the past
Mechanization of fishing craft for better productivity is a
common slogan all over the world. Once mechanization
starts, the productivity of fishing operations will certainly
increase, and soon boat size will be enlarged. The
problem of either market or natural resources, or even
both of them at the same time, will then have to be faced
gradually. The Government then starts to establish
regulations, first to limit the number of vessels and then
the size of individual vessels.
Fishermen try to survive under such restrictions and
this leads to unreasonable design of fishing vessels and
results in loss of fishermen's lives. This is especially true
when the industry is supported by cheap labour based
on a dense population, as automation of fishing opera-
tions does not contribute to the economy of fishing
operations. Under such circumstances, better productivity
simply means increase of production. This has long been
the specific feature of mechanization of fishing craft in
Japan.
LACK OF LABOUR AND NEW STAGE OF
MECHANIZATION
Decrease of fishing population
In the past ten years, the Japanese economy has developed
rapidly. The rate of increase of industrial production
has been more than 10 per cent every year. The rate is
estimated at about 8 per cent for the coming five years,
according to the economic plan made in 1964. This
indicates that demand for labour has been large and it
will remain large in future.
The fishing population has been greatly absorbed into
TABLE 11
Change of particulars of 39-GT type wooden skipjack and tuna vessels
(1) tuna/skipjack and polc-and-line fishing boats
Year and no. of 1957
vessels involved
1958 1959
(3)
I960 1961
(W)
1962
(9)
1963
(4)
1964
(*)
LBD
ft:<
m3
6,220
176
— 6,250
177
6,280
178
6,220
176
6,140
174
GT
-
39.87
39.70
39.73
39.80
39.51
NC
—
— 38
— 36
37
32
32
hp
153
172
187
210
240
FH
ft3 —
m:i
1,770
50
— 1,590
45
1,695
48
1,695
48
1,695
48
FO
ft3 —
iri1
— 233
6.6
— 315
8.9
318
9.0
350
9.9
364
10.3
Ai
—
— 62
— 70
71
72
69
Ad
---
109
121
106
106
118
Year and no. of
vessels involved
LBD
GT
NC
hp
FH
FO
ft:i
nv<
ft8
ft3
m9
1957
(9)
5,780
164
39.66
17
106
1,590
45
340
9.6
58
97
1958
(13)
5,970
169
39.64
18
139
1,695
48
460
13.0
58
105
7959
(20)
5,900
167
39.41
19
150
1,620
46
470
13.3
65
111
(2) longliners
1960
(64)
6,270
178
39.70
18
157
1,620
46
500
14.1
68
116
7967
(62)
6,350
180
39.73
18
170
1,550
44
480
13.5
69
116
1962
(26)
6,350
180
39.86
18
178
1,550
44
480
13.5
70
118
J963
(12)
6,320
179
39.78
18
197
1,380
39
430
12.1
73
117
7964
US)
6,320
179
39.65
17
211
1,410
40
500
14.1
75
119
[66;
4
3
1- (mean value)
HIE coastal fishery
• pelagic fishery
_, HiillHB.
1956-61
year
Fig 2. Annual percentage decrease in fishermen
TAULL 12
Trends of fisheries labour
1961
1962
1963
1964
Coastal fishery*
Pelagic fishery t
Total: }
509,<MX)
214,000
723,000
491, (KM)
2()8,(XK)
699,000
469,(XX)
198,(XX)
667,000
44(>,fXX)
180,(XX)
626,'XX)
* fishery with under 10-ton fishing boats
t fishery with boats of 10 tons and over
j includes those who are engaged in fisheries more than 30 days a
year or those who earn more than half of their annual income from
fisheries.
other industries. Statistics show this clearly, as in table
12, which indicates that the increase in the fishing
population is larger for pelagic than for coastal iisherics.
This decrease was slower from 1956 to 1961 than from
1961 to 1964, as shown in fig 2. This indicates that the
decrease will be more accelerated in the future. Change
in decrease of pelagic fishermen between these two
periods is especially remarkable. The workers in the
pelagic fisheries are employees of vessel owners and
have the easiest possibility of changing jobs. However,
coastal fisheries are operated mainly by family labour
and these workers cannot change jobs as easily as
pelagic fishermen.
Decrease in the number of fishing enterprises
Decrease of labour in fisheries resulted in decrease in the
number of enterprises, as shown in table 13. The rate of
decrease is remarkable in the pelagic fisheries.
This decrease in the number of enterprises is analysed in
respect of size of fishing vessels, and it is clear from fig 2
that there is a decrease in the number of enterprises
operated with non-powered craft. Such a decrease in the
pelagic fisheries happened because of the decrease of
enterprises operated with small fishing vessels under
200 GT, as shown in fig 3. This figure also shows that
in spite of the decrease in the total number of enterprises
both in coastal and pelagic fisheries, coastal enterprises
with small power craft and pelagic enterprises with large
vessels over 200 GT have increased.
TABU: 13
Number of enterprises
1961
1962
1963
1964
Coastal fishery
Pelagic fishery
Total:
225,200
9,6<X)
234,800
222,100
9,300
231,400
218,200
8,8(X)
227,000
212,900
8,400
221,300
coastal fishery
88%
pelagic fishery 2
440
boot
Hg 3. I'ariation in coastal ami pelagic fisheries
Kconomy of coastal fishermen
As already mentioned, the decrease in the number of
fishermen has been larger in pelagic than coastal fisheries
because the employees of the latter fishery can easily find
other employment. On the other hand, coastal fisheries
arc based on family labour which cannot find access to
other jobs. Table M shows thai the decrease of labour
in coastal fisheries has also been mainly in employees.
The decrease of labour has been counterbalanced by an
increase of fixed capital investment, i.e. mechanization.
The table shows that the productive index has increased
under these conditions (fig 4).
prunrj dollar
270 -750
I GO
108
'08
'07
500
300f
..-.-_ ;;,---' B
A value added per man
B fixed capital per man
i I. :
1956 59 60 61 62 63 64
year
I ig 4. Economic efficiency t»f coastal fishermen
Economy of pelagic fishermen
Table 15 shows that a decrease of labour has been
counterbalanced by fixed capital investment. Fig 5
indicates that this was carried out more in large enter-
prises with vessels over 100 GT, than those operating
smaller boats.
pound dotlor
288 800'
180 500;
108 30C|
36' lOOt
100 ton ond over
. B
I01on~99ton . . , :B
1956 59 60 61 62 63 64
yeor
B fixed capital per man
A value adder) per man
I IK 5. Lconomic efficiency oj pelagic fishermen
[67]
c 2
and a system of carrying fuel oil in a huge plastic bag
in the fish hold was devised. This led to unsafe vessels
due to movement of liquid in the iish hold.
A/LBD: The light weight of the boats increased by
15 per cent in seven years. The weight of the departure
condition also increased by 10 per cent over seven years.
Influence of restriction on the design of vessels in the past
Mechanization of fishing craft for better productivity is a
common slogan all over the world. Once mechanization
starts, the productivity of fishing operations will certainly
increase, and soon boat size will be enlarged. The
problem of either market or natural resources, or even
both of them at the same time, will then have to be faced
gradually. The Government then starts to establish
regulations, first to limit the number of vessels and then
the size of individual vessels.
Fishermen try to survive under such restrictions and
this leads to unreasonable design of fishing vessels and
results in loss of fishermen's lives. This is especially true
when the industry is supported by cheap labour based
on a dense population, as automation of fishing opera-
tions does not contribute to the economy of fishing
operations. Under such circumstances, better productivity
simply means increase of production. This has long been
the specific feature of mechanization of fishing craft in
Japan.
LACK OF LABOUR AND NEW STAGE OF
MECHANIZATION
Decrease of fishing population
In the past ten years, the Japanese economy has developed
rapidly. The rate of increase of industrial production
has been more than 10 per cent every year. The rate is
estimated at about 8 per cent for the coming five years,
according to the economic plan made in 1964. This
indicates that demand for labour has been large and it
will remain large in future.
The fishing population has been greatly absorbed into
TABLE 11
Change of particulars of 39-GT type wooden skipjack and tuna vessels
(1) tuna/skipjack and polc-and-line fishing boats
Year ami no. of
vessels involved
7957 1958 1959
W
1960 1961
(10)
1962
(9)
1963
(4)
1964
(8)
LED ft3
m3
— — 6,220
176
— 6,250
177
6,280
178
6,220
176
6,140
174
GT
— — 39.87
39.70
39.73
39.80
39.51
NC
— — 38
— 36
37
32
32
hp
— — 153
— 172
187
210
240
FH ft*
m3
1,770
50
— 1,590
45
1,695
48
1,695
48
1,695
48
FO ft*
mn
— — 233
6.6
— 315
8.9
318
9.0
350
9.9
364
10.3
Ax
— — 62
— 70
71
72
69
Ac,
— 109
— 121
106
106
118
Year ami no. of
vessels involved
LBD ft3
nv'
GT
NC
hp
FH
FO
ft3
m3
ft3
ms
7957
(9)
5,780
164
39.66
17
106
1,590
45
340
9.6
58
97
1958
(13)
5,970
169
39.64
18
139
1,695
48
460
13.0
58
105
7959
(20)
5,900
167
39.41
19
150
1,620
46
470
13.3
65
111
(2) longlincrs
7960
(64)
6,270
178
39.70
18
157
1,620
46
500
14.1
68
116
7967
(62)
6,350
180
39.73
18
170
1,550
44
480
13.5
69
116
7962
(26)
6,350
180
39.86
18
178
1,550
44
480
13.5
70
118
796.?
(12)
6,320
179
39.78
18
197
1,380
39
430
12.1
73
117
1964
(75)
6,320
179
39.65
17
211
1,410
40
500
14.1
75
119
[66]
6 _
: (mean value)
\M coastal fishery
• pelagic fishery
3u
2 .
1 -
88%
1956-61
1961-64
year
Fig 2. Annual percentage decrease in fishermen
TABLE 12
Trends of fisheries labour
1961
1962
1963
1964
Coastal fishery*
509,000
491,000
469,000
446,000
Pelagic fishery t
214,000
208,(HH)
198,000
1 80,000
Total: t
723,000
699,000
667,000
626,000
* fishery with under 10-ton fishing boats
t fishery with boats of 10 tons and over
t includes those who are engaged in fisheries more than 30 days a
year or those who earn more than half of their annual income from
fisheries.
other industries. Statistics show this clearly, as in table
12, which indicates that the uccrease in the fishing
population is larger for pelagic than for coastal fisheries.
This decrease was slower from 1956 to 1961 than from
1961 to 1964, as shown in fig 2. This indicates that the
decrease will be more accelerated in the future. Change
in decrease of pelagic fishermen between these two
periods is especially remarkable. The workers in the
pelagic fisheries arc employees of vessel owners and
have the easiest possibility of changing jobs. However,
coastal fisheries are operated mainly by family labour
and these workers cannot change jobs as easily as
pelagic fishermen.
Decrease in the number of fishing enterprises
Decrease of labour in fisheries resulted in decrease in the
number of enterprises, as shown in table 13. The rate of
decrease is remarkable in the pelagic fisheries.
This decrease in the number of enterprises is analysed in
respect of size of fishing vessels, and it is clear from fig 2
that there is a decrease in the number of enterprises
operated with non-powered craft. Such a decrease in the
pelagic fisheries happened because of the decrease of
enterprises operated with small fishing vessels under
200 GT, as shown in fig 3. This figure also shows that
in spite of the decrease in the total number of enterprises
both in coastal and pelagic fisheries, coastal enterprises
with small power craft and pelagic enterprises with large
vessels over 200 GT have increased.
TABLL 13
Number of enterprises
1961
1962
1963
1964
Coastal fishery
225,200
222,100
218,200
212,900
Pelagic fishery
9,600
9,300
8,800
8,400
Total :
234,800
231,400
227,000
221,300
coastal fishery
1956,
1963
pelogic fishery °
3/l953 I
>/1958 KX^I
-trif
ton
10-29
30-99
L
powtrtd boat
2OO and ov«r
.?. Variation in coastal and pelagic fisheries
Economy of coastal fishermen
As already mentioned, the decrease in the number of
fishermen has been larger in pelagic than coastal fisheries
because the employees of the latter fishery can easily find
other employment. On the other hand, coastal fisheries
are based on family labour which cannot find access to
other jobs. Table 14 shows that the decrease of labour
in coastal fisheries has also been mainly in employees.
The decrease of labour has been counterbalanced by an
increase of fixed capital investment, i.e. mechanization.
The table shows that the productive index has increased
under these conditions (fig 4).
pound dollar
270, -750
i , .._-•—-._ _ ..._ ' |0.9
-;::---._. 108
]0.7
- " B/A
180
108
500
A .-"
300h
A value added per man
B fixed capital per man
1936 59 60 61 62 63 64
year
Hg 4. Economic efficiency of coastal fishermen
Economy of pelagic fishermen
Table 15 shows that a decrease of labour has been
counterbalanced by fixed capital investment. Fig 5
indicates that this was carried out more in large enter-
prises with vessels over 100 GT, than those operating
smaller boats.
pound dollar
288- 800| .- B
180 500'
JOB' 30CJ-
i
36' I OOJ
lOOton and over
62 63 64
iOton~99ton .
fr \ ^
1958 59 60 61
yeor
B fixed copital per man
A - volue added per man
Fig 5. Economic efficiency of pelagic fishermen
[67]
c 2
TABLt 14
Economy of an average family fishing unit in coastal fishery
1958
1961
1964
(1)
Persons engaged
2.2
2.0
1.9
(2)
Employees (non family member)
included in the above figures
0.7
0.6
0.5
(3)
Working hours on board per
person
1,834
1,741
1,788
(4)
Fixed capital investment
£
249
271
372
(S)
(697)
(758)
(1,040)
(5)
Earning
£
282
329
490
($)
(788)
(920)
(1,370)
(6)
Productive index (5)/(4)
1.132
1.214
1.317
(7)
Faming per person
£
128
136
196
($)
(359)
(380)
(548)
Note: Earning -(income) (cost of fuel oil, ice and bait)
- profit -I wage } interest i depreciation
pound dollor
vokitaddtd
720 2000
' I /
\ BO: aoof A
fixed QSMt
SoTlOOO 2000 5000 4000
180 360 720 1 080 I44O
5000 dollor
1800 pound
Fig 6. Relation of fixed a.\.\cf and value atlclecl per person
Future of fishing industries
From tables 14 and 15, it is found that (1) productive
index is larger when the scale of enterprise is smaller;
however, (2) absolute value of per capita earnings is
greater in large enterprises. Jf the wage amount could be
reduced, there is more possibility of making a large
profit in large-scale enterprises. Fig 6 shows the relation
between fixed capital investment per person and value
added per person.
Tables 14 and 15 also showr that in a specific size of
enterprise, it is possible to increase per capita earnings
without decreasing productive index. This is most true
when either mechanization of fishing vessels enables the
number of crew to be decreased, or when increased
production is possible.
Effort should be applied to both decreasing the crew
and increasing production. Jn Japan the attention of
fishermen has been concentrated in the past on how to
increase production. However, they are now forced to
pay more attention to how to decrease the number of
crew. Such a change in fishing operations has happened
in Japan not because of the intention of fishermen, but
because of the shortage of labour.
Anything which could save labour should be adopted;
for example, remote control systems governing engines
and propellers, synthetic fibre fishing nets and plastic
hulls which save labour on maintenance. It is also
important to organize co-operatives so that small-scale
operations can be changed into large-scale enterprises.
The importance of mechanization to save labour is
further shown by the results of the Fisheries Census in
1953 and 1963. Fig 7 shows that a large number of
young people were engaged in fisheries in 1953 but the
age pattern of fishermen has changed drastically in
1963.
The future of the Japanese fishing industry depends
entirely on whether mechanization can overcome the
shortage of labour.
C=D -1953
C3- 1963
I5H9 20-2930-^9404950-59 6O- and Over
age
Pig 7. Age distribution of fishermen
OL
1958
1 . Persons engaged
10-99GT 14.7
over 100 GT 32.5
2. Fixed capital investment
10 99 GT £ 4,611
(I) (12,890)
over 100 GT £ 53,253
(!) (149,100)
3. Earning
10-99 GT £ 3,976
($) (11,130)
over 100 GT £ 30,567
($) (85,300)
4. Productive Index (3/2)
10-99 GT 0.862
over 100 GT 0.573
5. Earning per person
10-99 GT £ 270
($) (757)
over 100 GT £ 940
($) (2,630)
TABLE 15
Economy of an average pelagic fishing enterprise
7959 7960 7967
14.4
31.1
5,791
(16,210)
58,727
(164,400)
4,176
(11,700)
35,998
(100,600)
0.720
0.613
290
(812)
1,155
(3,230)
14.4
29.2
6,223
(17,410)
53,941
(150,700)
4,660
(13,040)
42,687
(119,300)
0.750
0.791
324
(907)
1,460
(4,100)
13.8
30.0
6,389
( 1 7,890)
57,167
(159,900)
5,525
(15,460)
42,867
(119,900)
0.865
0.752
400
(U20)
1,430
(4,000)
13.0
29.1
6,175
(17,300)
65,547
(183,700)
5,978
(16,740)
46,886
(131,400)
0.968
0.715
460
(1,288)
1,610
(4,520)
1963
13.0
27.6
6,822
(19,090)
73,757
(206,500)
6,338
(17,740)
50,512
(141.400)
0,929
0.684
488
(1,366)
1,830
(5,125)
1964
12.5
27.7
7,293
(21,000)
79,856
(223,500)
6,405
(17,930)
49,335
(138,200)
0.879
0.618
513
(1,435)
1,780
(5,000)
[681
How technical, social
and economic conditions influence the
design of fishing craft
INDIGENOUS CRAFT DEVELOPMENT
Stoneman (Uganda): Uganda is a small Fast African nation
about the size of France, where the fishing industry has been
of importance since before contact with Europeans in about
1860. Fishing takes place on 13,000 square miles (33,000 km2)
of freshwater lakes, rivers and swamps and has always been
of considerable importance.
Before the European influence fishing was by means of
baskets, traps and spears. Seine arid gill nets were introduced
in about 1925, but little major development took place in the
industry until 1949. In this year when the total annual pro-
duction was about 10,000 tons of fish per year a Fisheries
Department was established as a technical branch of the
Game Department and a definite effort was made to increase
production. At that time fishing was undertaken by few
specialized tribes of Ugandans, markets were aLo specialized
and localized and there were man\ taboos against eating
fish by non-fishing tribes. Ti insporl of fish catches from the
lakes was difficult and localized markets restricted fishing
effort to areas within close reach of the landings.
The pattern of the industry was obviously that of a very
primitive under-developed industry.
Fishing boats and canoes in use varied very little from 1860
until 1949. Types were the primitive dug-out canoes up to
40 ft (12-2 m) long by 4 ft (1-2 rn) beam, hollowed from logs
Fig /. Primitive dug-out canoes used on Lake Victoria
(fig 1) and the "Sesse" canoes of Lake Victoria (fig 2) which
were of African origin but owed much to the Arab influence
from the East African Coast. The "Sesse" canoe is made of
four planks sewn with palm fibres in a hard-chine con-
figuration on a rudimentary dug-out keel member. At one
time these canoes were 70 to 80 ft (21 to 24 m) long war-
canoes used by the Ugandan Tribes in their inter-tribal
warfare but since 1910, they have become purely fishing boats,
now 28 ft (8-5 m) long, open fishing craft.
Seaworthy but shortlived
They were propelled only by paddles or poles, in very few
cases sails being used on Lake Victoria. The costs of these
canoes in 1949 were: dug-out canoes between £20 to £50
($60 to $140), "Sesse" canoes £40 ($110). They were rarely
paid for in cash, the builders being housed and fed by the
canoe owner during the construction. These canoes had many
disadvantages and were unsuited to anything more than the
purely local fishing which was then the pattern. The dug-outs
were long-lived, but unstable, dangerous in rough water and
of small carrying capacity. The "Sesse" canoes, while sea-
worthy, and effective craft were very short lived, the poor
h'g 2, Scssc canoes of Lake Victoria
timber and sewn construction that were used restricting their
life to about three years. Many of the East African lakes are
large, subjected to severe storms and bad weather and many
of the best fishing grounds lie well off shore. Some 4,000 to
5,000 of these boats were in use in 1949.
Unlike the position in many other tropical countries, the
Ugandan fishermen have always been completely independent,
own their own canoes, and fish in their own right, never being
tied to an on-shore moneylender as often happens elsewhere.
However, their economy was based very little on cash, the
crews working for a fish salary and the catch often being
bartered for food by the canoe owner. Boats worked inter-
mittently and canoe owners would stop fishing to take part
in other activities such as cotton harvesting etc. Catch per
boat in these days was of the order of 10 tons per year, then
valued at some £40 ($1 10) per ton on the lake side.
The typical pattern of fishing activity was for the canoe
owner and crew to work for one to two months building up
a stock of salt or dried fish, which would then be sold or
traded for food, after which the owner and crew would stop
fishing until economic necessity forced them back on to the
lake. This meant that canoe owners were not eligible for
normal commercial credit as they could offer no security or
regular income.
After the formation of a Fisheries Department in 1949 a
great deal of work was done to develop the fishing industry,
improved types of gear were introduced, communications to
the lake-shore and markets were improved, new markets were
set up and generally production increased considerably.
Search for improvement
The need for improved boats was obvious to the Depart-
ment and as a first step three or four different types of fishing
boats were imported from overseas. In order not to try and
advance too fast beyond the fishermen's ability to learn,
imports were restricted to open boats up to 30 ft (9*1 m) long.
These were powered with simple inboard engines. Boats from
Scotland, Denmark and Hong Kong were imported by the
69]
Department and demonstrated to fishermen. However, while
successful fishing boats, these failed to suit conditions in
Uganda, partly due to very high costs and to the lack of
familiarity of Ugandan fishermen with motor driven craft. It
had not been appreciated also that all fishing boats to be
used in Uganda would have to be beached for maintenance
and repair, as there were no slips or dry docks available to
the fishing industry. It also appeared very rapidly that boats
designed and built in Europe were most susceptible to wood
slightly different type of modified "Sesse" canoe known as
the "Nyanza" canoe, also a hard chine "Scsse" type, again
Fig 3. Kabalega boats an improved Scsse canoe
rot in Ugandan conditions and, in fact, most of the imported
boats were useless from this cause within twelve months.
In 1954 it was realized that a new approach was needed.
By this time a number of outboard motors had been used in
Uganda on traditional "Sesse" canoes and had proved
popular with fishermen and most efficient in the field. While
delicate and difficult to maintain the outboards could readily
be taken to a major town for repair and overhaul and, in
fact, many fishermen found it convenient to own two out-
boards, one on the boat working, one away in the repair shop
Fig 4. Kabalega boats under power on Lake Victoria
being overhauled. Despite other faults the outboards cer-
tainly appeared to be the immediate answer in Ugandan
conditions. It was, therefore, decided to encourage outboard
driven fishing craft and to attempt to make these boats in
Uganda from local materials. In this way a suitable boat
could be evolved and costs could be kept to the minimum.
A training scheme for boat builders was started in Uganda,
training being given by expatriate experts whose first task was
to evolve a prototype boat suited to Ugandan conditions. This
was to be a 20 to 30 ft (6 to 9 m) open wooden boat, outboard
driven. As a first step a modified "Sesse" canoe was designed
and built in mahogany timber and copper fastened through-
out, in accordance with good European practice, on sawn
frames. This type of boat known as the "Kabalega" boat
proved extremely successful (fig 3 and 4). It was later
modified to a round bilge clinker built craft, still outboard
driven. In 1956 a commercial boat building firm designed a
Fig 5. Nyariza canoe -being also a modified Sesse canoe
built in accordance with good European practice (fig 5). Both
of these types of craft proved to be easily built by Ugandan
boat builders and successful in Ugandan conditions. Prices
were higher than for locally built craft, the "Kabalega" boat
costing £170 ($475) and the "Nyanza" canoe £100 ($280).
Both types of boat were properly finished with paint and
preservative and had a life under good conditions exceeding
10 years.
Having evolved a suitable type of boat it was necessary to
get it adopted by the industry and at first there was a good
deal of resistance by fishermen to these boats. They had noted
and remembered the unsatisfactory, very expensive, imported
craft and were distrustful of another innovation. They also
found it difficult to raise even the fairly small amount of
capital needed for these two new improved boats. Even where
individual fishermen could raise the money required they
could not visualize the advantage from the new boats being
great enough to justify the extra expenditure over the
traditional type.
Financial aid
As this question of finance appeared a major stumbling
block the Fisheries Department adopted an Agricultural
Credit Scheme which had been designed to assist progressive
farmers, and made it applicable to the fishing industry. The
Government sponsored Uganda Credit and Savings Bank
made loans to progressive farmers and traders and this
scheme was extended to cover progressive fishermen. On the
recommendation of a Fisheries official suitable fishermen were
eligible for a 100 per cent loan from the Credit and Savings
Bank, secured by nothing more than the boat and engine which
this loan would buy. This was a much more favourable type
of contract than any available from commercial banking
institutions, even if a fisherman could secure these.
On this basis the first two boats to be built were sold to
fishermen. These first two boats succeeded even better than
had been hoped by the Fisheries Department and very
rapidly made large profits for the first two owners. The
example was taken by the rest of the fishing community, and
some 60 boats were sold in the first eighteen months of the
scheme. New powered boats proved much more effective
fishing vessels than old type canoes and were also used as
fish carriers, ferries and so forth.
Encouraged by this start many more loans were approved
and granted and building of the improved boats continued
apace. However, unfortunately, shortly after the scheme got
into full swing the developments in Congo caused a slump in
[70]
one of the major markets for Uganda fish and, at the same
time, a trade recession within Uganda caused a fall off in
internal markets. This resulted in a considerable number of
loan defaulters both amongst farmers, traders and fishermen.
The Credit and Savings Bank had thus to suspend entirely its
loans scheme and fishermen once more found that it was
impossible to obtain finance for buying new canoes.
Despite this development, however, the loan scheme had
done very valuable work and had demonstrated to lishcrmen
throughout Uganda the necessity of better boats for cilicient
exploitation of the fishery, and the advantages of the improved
boats were now widely recognized by fishermen. A disturbing
factor had appeared, however, in the boatbuilding programme
in that many of the improved canoes were not being main-
tained and were failing and deteriorating long before they
should have done. This was partly due to poor maintenance
by the canoe owners in trying to treat their new boat as they
had their old dug-out canoe (i.e. providing no maintenance
whatsoever) and also partly due to poor construction by boat
builders who cashed in on the wave of rapid building of
boats, and used cheaper inferior materials and hurried con-
struction methods. This last problem could be and was met
by a considerable drive by the Fisheries Department to
ensure good standards of construction, and by education of
fishermen to demand suitable timbers and construction
methods in boats they bought. Finance, however, was still
the major problem due to the failure of Ugandan fishermen
to save or invest their money during good months to build
new boats when the old was worn out, and there was still a
back -log of conservative reluctance to spend more than the
limit of £50 ($140) or so for the traditional old type of
canoe.
Canoe subsidy scheme
To attempt to get away from the drawbacks of the loan
scheme the Fisheries Department produced a new Fishing
Canoe Subsidy Scheme. This again was an adaptation of an
Agricultural Credit Scheme intended to subsidize tractors
and so forth for farmers. Details of the Canoe Subsidy Scheme
were based on similar schemes in UK, Canada etc. The
scheme, which is in operation at the moment, permits the
Department to give an outright subsidy of 33 per cent of the
cost of new fishing boats which have been built in approved
yards to approved standards. Strict control is exercised by the
Fisheries Department on the applicants for this scheme and
on the builders who are allowed to build to it. The amounts
involved so far have been small— £1,000 ($2,800) in the first
full year of the scheme, £2,000 ($5,600) in the second year
which is 1964/5. Considerably larger sums have been
estimated for in future years and the scheme will be applicable
to much larger vessels than those at the moment under
consideration. The scheme so far has been extremely success-
ful and provided a considerable stimulus to both the fishing
and boatbuilding industries.
From experience in Uganda it would appear that this is an
extremely useful way of financing the improvement of
fishing vessels in a small and very primitive fishing industry.
As has been said it was planned to produce the new fishing
boats required within Uganda and it was obvious that in the
end a fair volume of craft would be required. Traditional
craft were and are made by local canoe builders, untrained
men, and at one time the Fisheries Department attempted to
convert these native craftsmen to the construction of new
canoes. However, there was a great deal of reactionary, con-
servative objection to new boats by traditional builders, and
this attempt had to be abandoned.
The prototype boats and the early production models were
made in the Government training establishments concurrently
with the training programme and at one time the sale of
canoes to industry helped to finance the training schools.
Eventually the schools began to produce about 10 trained
boat builders per annum of which only 50 per cent were
eventually absorbed into the boat building industry for
various reasons.
All competent boatbuildcrs, these men had no training at
all in business methods or organization, and there was no
existing industry to which they could be apprenticed. lor
these reasons the Fisheries Department attempted to set up
groups of these men as independent, small scale, boatbuilders
in various centres, each year's off-take of boatbuilders being
Fig 6. Modern boatbuilding in Uganda
established in a different region. A typical firm would consist
of four trained boatbuilders in partnership who were assisted
to obtain loan capital up to approximately £500 ($1,400) by
the Department. The Department also provided a boat-
building yard, a simple open sided shed 60 by 30ft (18 by
9m) and housing for the boatbuilders. Departmental staff
assisted with the ordering of supplies and materials, book-
keeping, sales and so forth. As would be expected such
embryo firms needed two to three years very careful "nurs-
ing" by the Department before they could be considered
independent and to date the failure rate is very high (33 per
cent). The better firms have become firmly established
independent entities, and have repaid all their loans and
built up considerable stocks of materials and bank balances.
JFiff 7. Self-financed boatbuilding in Uganda
Some five of these small firms are now established throughout
Uganda and the better ones operate their own, self-financed
hire purchase schemes to fishermen (fig 6 and 7).
Production of boats from such yards is now running at
about 10 per month of which 60 per cent arc subsidized
[71
vessels. Training continues and it is fairly clear that within
a relatively short time Uganda will be in a position to con-
struct all the improved type boats that will be used by the
fishing industry.
Experience gained in Uganda may well be of value in
other countries faced with a similar problem.
The major factors involved in bringing about this replace-
ment in Uganda have been :
• Government assisted finance by means of loans and
subsidies to fishermen for the purchase of new fishing
boats
• The design of prototype craft suited to local conditions
using local materials and keeping costs to a minimum
• Training and setting up local boatbuilders to produce
these craft, again with the aid of Government finance
It should bs recognized that certain conditions in Uganda
were and are very favourable to this type of development and
these should not be overlooked when a similar scheme is
considered in another territory. Such conditions were:
• The independent nature of fishermen, and the tradition
of self ownership and use of fishing craft
• The high level of employment and ability among
fishermen enabling them to make good use of improved
craft
• The very much greater power of improved craft
ensuring great demand for them once this had been
demonstrated
The success of the scheme can be judged by the number of
improved boats now in use, approximately 400, coupled with
the considerable year by year increase in fish production now
(1965 figure) running at 72,000 tons per annum valued at
£2.8 ($8) million.
North Atlantic problems
Danielsen (Switzerland): The following figures pertaining to
the North Atlantic provide an illustration of the importance
of the organizational problems of fishing boat operations:
• Labour costs on board: 35 50 per cent of turn-over
• Raw material cost : 60 70 per cent of factory cost
• Labour costs on shore: 10 1 5 per cent of factory cost
These figures speak for themselves and emphasize the fact
that in the heavily increasing competition on the market, no
pains must be spared in making the raw material supply, and
thus the fishing boat operations, more effective.
The problems of manning the fishing fleet in the North
Atlantic area have grown bigger every year, in spite of the
fact that conditions on board have improved considerably.
In some places traditions have been preserved and the
crew seems to have identified itself with its job and stayed
aboard the same vessel year after year. Group feelings seem
to have been very strong. This emphasizes the important role
the skipper plays. An important factor may be that trips have
been to distant waters (from the Western coast of Norway,
to Greenland and to Newfoundland) and it may be that men,
being together for such a long time — sharing what is good and
what is bad get a feeling of confidence in each other and in
their skipper.
The conditions for the crew have improved over the last
40 years. One needs only to consider:
• The accommodation now and before World War II,
where 30 men were sleeping in the same room, where
they had their meals and where all their meals were
prepared
• The working hours before were up to the skipper to
decide upon. It was not unusual to work 20 hours a
day during all the fishing time. Today, the working
hours are in most cases limited to 12 hours a day
• The payment before was very poor compared with
what other people were paid for their work. A fisher-
man was, in many cases, paid somewhere between 10
and 20 per cent of the payment given to salaried
people (school teachers for instance). Today, the
difference is very much less and in some cases fisher-
men are even better paid than school teachers
Altogether a considerable change for the better has taken
place as regards fishermen, but in spite of this manning
problems have grown bigger and bigger and there are many
examples oj where it was not possible to man the boats at all. In
some areas in the North Atlantic, the "turnover" of fishermen
during the last 15 years has increased up to 500 per cent. In
many cases the boats have been under-manned or they have
been out with a major part of the crew below the minimum
quality level.
What is the reason for this development? The answer can
be found in the following:
• The standard of living has, as a whole, increased con-
siderably and there has been an evening out of the
living standards between the most developed parts of
a country and the "under-developed" parts of the
same country (from this latter part the fishermen have
normally come). There has been an increasing need for
office clerks, construction workers, shop assistants,
etc., and normally people have preferred this kind of
work to being a fisherman
• Communications have improved. Shipping lines and
motorways have been established. It has been easy for
people to come from one place to another, and further
travelling costs have been low compared with pre-war
costs
• Education systems have been built up. All young
people, independent of social status, have had the same
possibilities as regards education. The scope of young
people has increased and they have been looking for
a job giving them the highest possible satisfaction and
status in the society
• Technology has changed. Fish-handling is now being
carried out partly on board the ship and partly on
shore and the tendency has been towards more and
more refined products. The need for factory workers
has increased and this part of the business has taken
many good fishermen
Modern boats have been designed and equipped with
modern tools. But because of the changes in the environments,
more should have been done as regards the training and
education in order to make the job interesting and con-
structive for the crew.
Objectives in making the social design can be defined as
follows:
• To obtain a more efficient crew
• To obtain a more stable crew
• To reduce the manning on board the boats
Work flow
In some countries a fresh-fish trawler is operated with
12 to 14 people (I skipper, 1 mate, 2 engineers, 1 cook, 7-9
fishermen). The corresponding figure for other countries may
be 22 men (1 skipper, 1 mate, 2 trawler bosses, 2 engineers, 1
cook, 1 mess and 14 fishermen). Why such a difference? In
many cases the working methods and manning have been
determined by the feelings, intuition, etc., and have been put
down in the agreements between the fishermen's union and
72]
the trawler owners. If time and method studies had been done,
considerable inefficiency would in many cases have been
revealed. This does not at all mean that it is not a hard and
stressing life for the crew on board, but a better planning and
a better synchronization of the jobs would, without doubt,
have given considerable results.
Authority
The authority system on board has to be designed so that
everybody feels he belongs to the vessel and feels he contributes
to the objectives. The atmosphere is to be so that the people
feel that they also have a say, that they also are important and
that they themselves are equally responsible for the planning
and performance of their job. The skipper must feel respon-
sibility for the full utilization of the potentialities of his crew.
Evaluation
If people arc given the opportunity to check (or better,
review) their performance, they will feel challenged to improve
it and to improve their standards. Goals must not be forced
on people, as this will create a resistance or a position of
self-defence, but the crew is to be given the opportunity to
influence or participate in goal setting as this will increase
their responsibility feeling and thus their performance.
In evaluating the individuals one has to take into con-
sideration:
Quality of work done
Quantity of work done
How the crew member is atte( ding his work?
Is he independent in his work?
How is he performing his job?
For how many jobs is he fit ?
Is he careful with the equipment, tools, etc.?
Is he interested in his work?
Evaluation is normally a sensitive problem, but people
usually like it, if it is done in the right way. Therefore there
will be an incentive in the evaluation.
Remuneration
The salary system has to be so designed that the crew feels
challenged to do a good job. In most countries today, working
hours on board are limited to 12 to 14 hours a day. For these
working hours and for staying away from family and home
about 320 days a year, the fisherman receives in many cases
a salary that is not very much better than he would have
obtained working 7 A hours a day in the factory which he is
supplying with raw material. This seems to be a typical
"output approach".
Rewarded in accordance with the possibilities people have
on shore, a fisherman's salary should be:
• Basic salary (corresponding to payment
for ?i hours work per day ashore) -100 per cent
• Overtime payment 75 per cent
• Allowance for dirty and hard work — 10 per cent
• Deprivation allowance — 15 per cent
Total 200 per cent
In some countries, fishermen really have an income that is
about 200 per cent of the income possibilities on shore, but
in other countries this is not so. For these countries, an
adjustment in payment would result in an increase in the
price of the raw material. The remuneration system must be
redesigned, aiming at evening out this difference, and this
must be done in such a way that the fishing boat operators
receive a compensation in an increased efficiency.
In addition to:
• A fixed minimum salary normally determined by law
and/or agreements between fishermen and boat owners
• A linear or progressive quantity bonus, and
• A progressive quality bonus,
there has to be some kind of a qualification allowance, giving
an extra reward to those who are doing a better job than
others.
If the crew is not satisfied with the financial reward, this
will undermine and erode the responsibility that the crew has
to take in order to reach peak performance. The attitude of
the crew towards the salary question must not be to gain as
much as possible without feeling any responsibility for
quantity and quality of work done.
Communication
People must be told how they arc expected to reach the
objectives that have been stated. As fishermen arc away a
great deal of their time, special efforts must be made to create
mutual confidence between the crew and other parts of the
organization. Information about future activities, company's
results etc, give security and congenial feelings, and con-
fusion can thus be avoided.
The crcvv and the other parts of the organization must
exchange ideas and trace their view points against the right
objectives, the result of which will be optimum quality,
quantity, etc. The enterprise needs ideas and support from all
employees, also fishermen.
Identification
Lvcrybody has heard about people who went to sea at the
«ige of 14 and stayed with the same skipper until they bought
their own boat, after which they chose their own crew
members, who subsequently stayed with them for years until
they again went aboard their own boat.
Why has a change taken place? Has the increase in the
standard of living and technical progress been a threat to the
development of fishing? A social class must be maintained
with which the fishing people can identify themselves. This
class must be recognized and the members of this class must
be offered attractive conditions, so they feel proud of their
class and feel challenged to belong to it.
The first impression which people get when joining an
organization is very often the impression which will stay in
their minds for ever and will be decisive for their career in the
organization. Therefore, the enlisting procedure is of greatest
importance and has to be organized as follows:
• Introduce a newcomer to his skipper and the other
members of the crew
• Give him information about:
a. How the rules for work on board are and
eventually instructions for work;
b. breaks;
c. how he has to behave when the boat is in port;
d. when and how his salary will be paid;
c. questions in connection with agreements, etc
• Take him through all departments that he will be
concerned with ashore. Show him all facilities of
importance for him, such as cloak-rooms, wash-rooms,
canteen, etc
• Give him the personnel handbook rules, etc
• Give him the opportunity and encourage him to meet
crew members from other boats in order to exchange
view points
• Give him a description of the organization. Informa-
tion about the company's fringe benefits, etc
Frequent contact with the newcomer and frankness is
necessary for overcoming misunderstandings.
73
The conditions must be created so that the crew's personal
goals can be identified with the company's goals. The crew
must understand that their contribution to the company's
objectives is maximized when their work is done in such a way
that maximum output for the company as a whole is reached.
Perpetuation
The job of a fisherman has become less and less attractive.
Fishermen are mostly coming from small places where the
standard of living is low and where they have not had other
possibilities for income other than fishing. Fishermen stay
away from their homes for a long period, after which they
are in port for a few hours, or maybe a couple of days. This
problem could be minimized by having a spare watch so that
the crew could be given the opportunity to stay ashore a part
of the year.
Many young people come on board a fishing vessel, are
given the worst jobs and nobody tells them how the gear
works. This will give them an immediate unpleasant feeling
and a feeling of not belonging to the vessel on which they have
to stay. This could be improved by employing young people
as apprentices and by giving them a training period of two to
four years, after which they could be certified. The apprentice
should be given the opportunity to move from boat to boat
and of trying different working methods in order to get an
all-round background for his future profession.
Certifying the crew might be in contradiction with the
theories for "technical revolution". Many will say that the
crew members should be looked upon as if they belonged to
an "assembly line" and should in a few days be trained in
making certain movements, etc. Perhaps the skipper does not
need to know anything about fishing, ice and stream con-
ditions, etc, the vessel could be directed from a computer in
an office ashore. Just before leaving the port the skipper
could be given some punch cards that he has to put into an
auto-pilot and then he need not worry about what is hap-
pening, everything being done automatically.
Up to now, however, the success of a fishing vessel has
been much dependent on the crew and especially the skipper,
but as much as possible ought to be done to eliminate the
importance of certain qualified crew members. Even if it
will not be possible to get as far as using punch cards in
connection with an auto-pilot, fishing boats ought to be
mechanized so that the fewest possible people arc needed
aboard.
There must be good facilities for the people on board with
all the necessary modern equipment. Living quarters aboard
must be kept clean. Facilities must be arranged ashore so that
the crew has access to newspapers, telephones, canteen, etc.
Facilities have to be arranged for cleaning of personal
clothes, bed linen, etc.
In the future one must not only be concerned with technical
changes but also with psychological changes for both fisher-
men and administrators. People have to be trained and
educated. Objectives have to be clearly stated. All details and
information for reaching goals must be known. They must
identify themselves with their work, their company, the
remuneration system, quality standards, quantity standards,
etc.
How to proceed? The following three points seem of major
importance:
• Time and method studies in order to establish an
efficient work flow
• Social architects have to study conditions on board,
to get an idea how conditions can be improved, how
much people can tolerate, how the crew could be
better utilized, etc
• Social architects have to help crew and administrators
to realize the need for changes and to help them over-
come all obstacles in accepting them
The responsibility of the social architect is the following:
• To make the crew familiar with the ship, each other,
changed methods, quality and quantity standards, etc
• To enable the crew to identify itself with the ship,
skipper, group, company, etc
• To enable the crew to feel responsible for the tools
they are dealing with and feel responsible for the
results they will obtain
• To give them the feeling that this is their company,
their ship, their work, "the best ship in the world"
etc
• To create one group out of crew and administrators
and to give this group the feeling that they are all "in
the same boat" with the same objectives
Much work in the past has been spent on improving fishing
vessels, methods of handling gear, mechanization, etc. But
the right balance between technical standards and social
standards on board has not been achieved. The results of
further technical improvements will be lacking if the social
design is not improved correspondingly.
Chapelle (USA): The naval architect engaged in a project of
aid in the expansion of an underdeveloped fishery has a dual
role, teacher and taught; teacher in boat building and design,
taught in economic and social areas.
The economic factor is perhaps the more effective limitation.
A lack of capital may be said to be the universal problem.
The success of the naval architect will depend upon his
utilizing these limitations to the utmost. The effects of the
economic factor will be most marked in the introduction of
new building techniques, new gear and new materials.
The social aspects he will meet and understand as he goes,
but the economic factor is the one that requires his prime
attention.
Local Problems
H0gsgaard (Denmark) : In Greenland there is a similar problem
to those llamlisch described. Jn earlier times, seal and whale
fishing was the only fishing practised and hunters living in
small settlements had to be persuaded to change from
hunting to fishing.
In Scandinavia, the first engine was introduced to fishing
boats in 1900 and in 1904 there was an exhibition at
Marstrand, near Goteborg of both boats, engines and fishing
gear. Thus long experience in Scandinavia could be applied
to mechanization in Greenland. Two-stroke low compression
oil engines were used and at first the open boats and then
later the small cutters were mechanized. One of the most
difficult problems was that the fishermen in kayaks were used
to fishing close to the shore and had no experience of deeper
sea fishing. Therefore, the fishermen had to be educated to
go off-shore. In the Faroes, excellent fishermen with con-
siderable experience of deep-sea fishing were available. There-
fore, skippers from the Faroes were used on Greenland boats
with a Greenland crew in such a way as to train the Greenland
fishermen in off-shore fishing.
Experience in India
Gnanadoss (India): While complimenting Hamlisch on his
masterful presentation of two very important aspects that
affect the development of fishing, particularly in developing
countries, Gnanadoss liked to make a few observations —
mainly with reference to the impact these factors have had in
fishery development in India.
[74]
Improvement of marine fisheries by the mechanization and
modernization of the fishing fleet and methods present more
of sociological and economic problems than technological
ones. For instance, one of the maritime states in India, the
State of Madras, has a coastline of about 600 miles (1 ,000 km)
with about 300 fishing villages spread out along the coast.
The entire coast is mainly surf-beaten and harbour or berthing
facilities for mechanized fishing vessels exist in only about
five or six places. The fishermen all along this coast operate
from catamarans or rafts made of logs of wood, and from
small sailing canoes, which together number about 20,000.
These have limited efficiency and have not been found to be
quite suitable for mechanization.
Well, then, how could the lot of these fishermen be
improved? A logical answer is to provide them with with
mechanized fishing boats with modern fishing gear. Even
assuming that this impossible task of replacing all the
indigenous craft with modern fishing vessels is achieved, it
would be possible to berth these boats only in a few centralized
harbours. The bigger question is then-could the fishermen
be induced to leave their home and move to a distant fishing
harbour. This is really a human and sociological problem. In
many cases, the fishermen refuse to improve their lot, rather
than to leave their homes.
One of the likely solutions for this problem was to introduce
a craft, which he could operate right from his beach -namely
the beach or surf- bout. But the surf- boat, apart from its
technical limitations on efficiency and safety, was also an
expensive craft, well beyond the scope of tiic catamaran
fisherman. Furthermore, if the surf-ioats were to ultimately
replace all the indigenous craft operating from the beaches,
it would have involved such a phenomenal investment on a
venture, whose ultimate success was not very definite. There-
fore, in this case, the problem assumes a techno-economic
character.
Yet another state in India, the State of Gujerat, has a.
predominantly non-fish eating population, although the seas
off" the State arc foremost among the richest fishing grounds
of India. In developing the fisheries of this area, the main
problem has not been one of lack of technological knowledge.
In fact this area has one of the finest types of indigenous
boats which have been mechani/ed by just installing an
engine in the existing craft. The problem is that of finding
import markets for the fish outside the State, because of
social and religious prejudices in the area where the fish arc
landed.
Consumer preferences based on culture and traditions is
another factor which has greatly influenced the development
of fisheries in certain areas. The Stale of Bengal is a classic
example, where the people would pay any price for a fresh-
water iish like Rohn or Catla, but at the same time would be
very reluctant to buy a top quality marine fish at com-
paratively low price. This has naturally resulted in a highly
developed inland fishery in that area and a comparatively
less developed marine fishery, in spite of good marine
resources.
It will be appropriate here to make some observations on the
role the Government is playing to overcome some of the
factors that affect the development which has been commented
on by Hamlisch.
The fishermen in India today receive good assistance from
the Government through Fishermen Cooperatives both
financially and in terms of supply of fishing boats, fishing
gear and technical knowhow. The financial assistance is
mainly intended to enable the fisherman to pay off and get
himself released from the clutches of the middleman and join
the cooperatives to enjoy the other benefits.
Liberal subsidies allowed by the Government for supply of
mechanized fishing boats and modern fishing gear have made
it economically feasible for the fisherman to possess this
otherwise costly equipment and thereby improve his economic
and social status.
Mechanization of fishing is closely integrated with training
of technical personnel and plans for construction of fishing
harbours and facilities for proper handling, storage, pro-
cessing and marketing of the commodity.
Newfoundland practice
Harvey (Canada) : In Newfoundland a large inshore fishery is
undertaken, which has a duration of from five to eight months.
Cod netting, gill netting, longlining, Danish seining are
carried out. The boats in use are of wood construction and
from 36 to 60ft (11 to 18m) in length. Most of the boat-
building material is being cut by the fishermen on the island.
The type of propulsion fitted consists of diescl engines of
different reduction gear ratios or direct drive, with horse
power ranging from 35 to 180.
The boats are designed and laid out with the accommo-
dation and wheclhouse forward, with engine under the
wheelhousc and fish hold aft, or the engine, whcelhouse aft,
with cargo hold and accommodation space forward. The most
successful of these boats are the 45 to 50ft (13.7 to 15.3 m)
trap boat— longlinei .
The boats arc built under Government inspection, the
Department of Provincial Fisheries maintaining a staff of
wood inspectors and engineers who besides carrying out
inspection duties, instruct the fishermen builder in the con-
struction. This consists of supplying a set of full size lines.
Assistance is given by the Government (provincial) who pay
a bounty of $160 (£57) per GT.
Federal government subsidy of from 25 per cent to 35 per
cent of the approved costs is also available to the fisherman
if he qualifies. These vessels cost approximately 1850 to
$1,000 (£300 to £360) per GT which would make a 20 GT
boat cost about $18,000 (£6,500) completed.
Government payments would be $7,700 (£2,750) leaving a
balance of $10,300 (£3,750) in which the fisherman reduces
the amount by a down payment of 10 per cent or to a lower
figure by supplying the timber which he cuts for himself and
sometimes free labour. A loan for the remainder of the
amount can be repaid over a period of several years.
The most costly part of the venture is the engine and other
equipment. It is important that these costs be kept low so
that the fisherman is able to obtain a boat.
Evolution in Peru
Jimenez (Peru): The experience of Peru in developing its
fishing industry during the last decade should be of interest
to all those who study the evolution of fisheries in developing
countries. In ten years, Peru has gone from a yearly catch of
120,000 tons employing primitive methods and boats of less
than 36 ft (12 m) to a catch of nearly 9 million tons employing
about 2,500 modern purse-seiners of an average of 65 ft
(20m). As Hamlisch points out, this has been possible by
developing fishing of anchovy for the manufacture of fish
meal, a product in high demand for cattle and poultry feeding.
In order to accomplish this, it was necessary to create practi-
cally from scratch nearly 20,000 fishermen and 2,(K)() ship-
yard workers, which implied a number of socio-economic
developments.
As regards ship construction, two things were done:
a. The limited number of shipwrights in existence was
spread out, each experienced carpenter becoming the
foreman of an independent yard in which new car-
penters were trained ; and
b. A steel boat construction industry was created by
[75]
recruiting labour from the existing metal-working
trades.
People were easily attracted to the new industry by the
higher rates of pay offered. Quality naturally suffered initially
due to the large influx of unskilled workmen, but this was
overcome in a few years by the experience acquired and the
gradual disappearance of wood construction, where the more
serious problems of lack of skilled workmanship occurred. In
1963, 500 boats of 60 to 65 ft (18 to 20 m) in length were built.
At present, with the industry stabilized, about 150 boats per
year of 65 to 100 ft (20 to 30 m) length are built to the rules
of classification societies and some boats are even exported
to neighbouring countries. The workers (about 2,000), are
mostly paid in proportion to their productivity, and they earn
well above the average for industrial workers in the area. A
final contribution to the solution of the ship construction
problem was the standardization of designs. Most of the
shipyards have built over 100 boats of a single design, and
this has allowed appreciable savings.
As regards the crews for the fishing vessels, a system of
payment was developed based on the amount of fish caught.
The owner provides the boat, with fishing gear, fuel and
food. The crew goes out fishing and the skipper receives a
fixed amount per ton, which he distributes among the crew
in accordance with agreements among them. The skipper
averages a high income, which has allowed several of them
to become owners of their own boats; the rest of the crew
also receive a higher income than they would obtain in other
activities. As a result, there is no problem in hiring the
required crew members, nor in obtaining their acceptance of
any technical development that increases the catch.
In addition to a good income, the Peruvian fisherman
enjoys very favourable working conditions due to the
proximity of the fishing areas. Weather is good; storms are
unknown. The boat returns to port every night. Echo sounders,
asdics, fish pumps and power blocks are in increasing use,
thus decreasing the physical effort required of the fisherman.
Besides, each fisherman enjoys a one-month, paid, yearly
vacation and a compensation upon ceasing his fishing
activities, paid from a fund financed by the shipowners, as
well as medical assistance and hospital service paid from
another fund jointly financed by the shipowners and fisher-
men in the proportion of three to two.
Hamlisch also pointed out that "cash-crop" fishing may
have a negative effect on the nutritional level of the population.
This has not happened in Peru because people have not
developed the habit of eating fish and the price of fish is
relatively high, resulting in a very limited demand. On the
contrary, indirectly, fish meal has allowed the production
and import of other foodstuffs to increase, as it is at present
the main source of foreign exchange. However, this situation
is not fully satisfactory. A fishing nation like Peru should not
permit a lack of proteins in its diet, and this must be improved.
Two things are being done:
a. Trying to lower the price of fresh fish, introducing
modern techniques in those fisheries and simul-
taneously carrying out an educational campaign on
the advantages of eating fish; and
b. Supporting research in the adaptation of anchovy fish
meal to human consumption.
Neither of these solutions will give results overnight, but
in time they will allow the nutrition to be improved.
Independent Fishermen
O'Meallain (Ireland): The following remarks concern the
independent fisherman, as understood in Europe for example,
the fisherman who is self-employed either as owner or part-
owner of a fishing boat or as a crew member on a share basis.
There is a tendency to discount him on purely short-term
economic grounds and the arguments seem cogent enough;
but this need not always be so.
At the moment he is under severe pressure on two sides.
Competing against him are large vessels carrying fish a
quarter way around the globe. Even though the economics
of large vessel operation may often be unsound, and in spite
of the fact that, as Hamlisch says, "Skipper ownership of
vessels may stimulate better management", the weight of the
large-scale enterprise and the very fact of uneconomic
operation could drive the independent fisherman out of
business, the end result being general depression in fishing.
The second course of pressure is the rapidly rising costs of
boats, gear, equipment and maintenance, without a corres-
ponding increase in the unit price of the fish. At the Scantlings
Meeting in Copenhagen in 1964, Tyrrell drew attention to the
seriousness of the question of building costs and suggested
determined efforts rather towards means of reducing building
costs than towards refinement of design. One cannot deny or
decry the technical advances that have been made and are
being attempted, but they must be clearly measured in
economic terms.
Hamlisch, in his comprehensive review, seems to write-
down, more than is justified, the economic importance of the
independent fisherman and perhaps to oversimplify the
position. There arc examples in many countries, notably in
Sweden, of the prosperity of large bodies of independent
fishermen. Nevertheless, the pressure of increasing costs is
there and this combined with the other pressure mentioned,
may drive him to the wall unless appropriate measures are
taken. In the long run, the independent fisherman is the basis
of the industry. If he disappears, only a fully socialized under-
taking can replace him.
A large part of the increase in costs may originate with the
fishermen themselves. It is believed, for example, that the
smaller vessels such as are being considered here arc often
grossly overpowered, even for the hull shapes involved. This
cannot be put down to lack of sophistication on the part of
fishermen, because it is precisely among the most progressive
that the demand for increased power is found. It is urgent
that the facts be determined, and that the fishermen be per-
suaded of their validity. This is altogether independent of
economics in power that could result from improved hull
shapes. It is also important that authoritative advice be
available to fishermen as to materials and equipment, some-
what on the lines of that given by building centres.
Most important of all, but most difficult is advice as to the
boat. Apart from technical considerations, a great deal will
depend on what a man can afford. Where substantial state
assistance is available, the question might reduce to a technical
one.
Apart from ships engaged in the pursuit of ocean species,
the maximum tonnage and horse power need not exceed those
necessary to enable the vessel to fish effectively and econo-
mically the extent of waters to which it has access by virtue
of its nationality, because the extension of fishery limits is
likely to render the operation of distant water trawlers less
profitable than at present. Whether such reduction in profit-
ability can be accepted over a long period is questionable.
Eventually, the greater part of fishing activity, apart from
that for ocean species, may be confined to relatively small
highly efficient vessels with small crews and owned by the
skipper or by the skipper and crew jointly. Trade in fish may
eventually replace fishing in waters off coasts other than one's
Own.
Mechanization
K varan (FAO): Mechanization of existing craft versus con-
76]
struction of new craft is a problem which is met in many
fields of development other than fisheries. In "Economic
Philosophy" (page 114-15, Pelican Edition, 1964) Robinson
(1964) has this to say:
"There is another topic, in connection with problems
of underdevelopment, that has been much discussed in
terms of theoretical analysis; that is the choice of
technique when a variety of methods are available for
the same product. The field is clouded by two opposite
prejudices. One is the snob appeal of the latest, most
highly automatic equipment and the other the senti-
mental appeal of the village handicraftsman."
She then proceeds to propose two simple guide lines, first
that no equipment be scrapped or methods of production be
rejected so long as better use elsewhere cannot be found for
the labour and materials used in them and second, that no
technique be chosen because it provides employment. The
continuation of the analysis might have been made with
fisheries mechanization specifically in mind:
"There remains cases of genuine doubt where a less
capital using technique, with lower output per head,
promises more output per unit of investment, or a
quicker return on investment, than another which is
more mechanized and requires less labour. It has been
argued that in such a case the correct policy is to
choose the technique that yields the highest rate of
surplus, so as to make the greatest contribution to
further accumulation. At first sight this seems very
reasonable, since development is the whole object of
the operation. But when we look closer, it is not so
obvious. The surplus which a technique yields is the
excess of net product over the value of the wages of
the workers who operate it. A higher surplus means a
faster rate of rise in output and employment, starting
from a smaller beginning. The more capital-saving
technique yields more output and pays more wages. It
is for that very reason that it oilers a smaller surplus.
"There is a choice between some jam today and more
jam the day after tomorrow. This problem cannot be
resolved by any kind of calculation based on 'dis-
counting the future" for the individuals concerned in
the loss or gain arc different. When the more
mechanized, higher-surplus, technique is chosen, the
Joss falls on those who would have been employed if
the other choice had been made. The benefit from their
sacrifice will come later and they may not survive to
see it. The choice must be taken somehow or another,
but the principles of Welfare Economics do not help
to settle it."
In making the above assessment Miss Robinson makes the
basic assumption that output per unit of investment can be
predicted in advance. In new fishing ventures this is true only
within wide limits, a fact which favours solutions using low
capitalization.
Analysing the figures
DC Wit (Netherlands): In Takagi's and Hirasawa's paper it
is stated that fishermen with non-powered boats earn much
less than those with powered vessels. A glance at table 4
however, reveals that a non-powered boat in 1961 had an
annual production of 2.59 tons of fish from 867 man hours
for a crew of one (table 3).
This means a production of 6.6 Ib (3 kg) per man hour and
secondly, an average working week of 16.6 hours, per man
hour.
When using the corresponding figures for the powered
boats of 3-5 GT in 1963 it is found that the production per
man hour is almost the same, i.e. 6.8 Ib (3.1 kg) per hour but
that the working week increased from 16.6 to 76.4 hours.
Even in the case of powered boats of under 3 CiT, the working
hours have increased and the production per man hour
decreased from 7.7 Ib (3.5 kg) to 4.6 Ib (2.1 kg) per man hour
in 1961 and 1963 respectively. If mechanization leads to
excessive working hours and reduction in production pet
man hour, fisheries are losing the battle they have to fight
with land leisure, industry and comfort ashore. This is not
only true in Japan, but in many other countries all over the
world.
Economic studies
Hildebrandt (Netherlands): Hamlisch and his colleagues have
given most interesting papers about thetcchno-socio-economic
problems.
Hamlisch stressed the fisheries of the developing countries.
Of course!
Fish is the cheapest protein and in those countries there is
a big shortage of protein food. It is therefore that especially
for developing countries the fishing industry is a good business.
Techniques are therefore of the greatest importance. In the
highly developed countries, however, very good fishing
vessels atv built, but the profitability is such, that the govern-
ments have to subsidize the fishing industry. This is an
important question for the vessel builders too.
There are two problems:
One is the marketing of fish in developed countries. In
these countries there is a very keen competition with other
protein. To get a higher value for fish it is necessary to do
market research in order to find out how to stimulate the
market But getting higher earnings is not enough, there must
also be lower costs.
The Hutch fishermen arc still building bigger ships. Here in
Go'teborg a fisherman said that he had a fishing vessel with a
motor of 800 hp but that his colleagues want to build cutters
with 1,000 hp. Several different answers are given.
For instance:
• If my neighbour builds a new vessel, I want a bigger
one. Rivalry among fishermen
• Because the biologists tell us that there is a declining
stock of fish
• More modern equipment requires ever more space on
board. Therefore, we need bigger ships
• And lastly, to earn more
What is true:
• Which were the main factors determining the profit-
ability of fishing vessels during recent years?
• This can determine the economically optimal fishing
vessel for a certain fishing ground and a certain method
of fishing. That may be a question of linear program-
ming
• The results of these micro-economic studies may
possibly give an answer to the question: are the
fishing grounds exploited in an economically rational
way?
Hildebrandt gave some preliminary results of his study of
the first question: What determined the building of a fishing
vessel in recent years?
The only way of studying this is empirical. Over the period
1955 till 1965 Hildebrandt worked with 24 variables and
about 200 observations of costs and earnings and technical
data of the same type of fishing vessel of different size and
different motor capacity on the same fishing ground during
the same period of time and the same method of trawling
herrings on the North Sea.
Then there is the question of the method of research.
[77]
Variables
Squared factor loadings — Percentages
Total
1
II
III
IV
V VI
VII VIII
(1) Abundance estimate
7
48 I
41 +
—
4_
—
100
(2) Trend
821
10-
8-
—
— —
— —
100
(3) Value added pd, pm
14-
__.
9 -
42+
5 +
19 +
89
(4) Investment ship
8 +
—
4-
66 1 18 [
96
(5) Net profit pd, pm
21-
10 -
33 +
•7 i.
15 +
86
(6) hp pm
7+
—
3-
3-
86 \- —
99
(7) GTpm
—
.._
—
3 +
— —
28+ 65 +
96
(8) Number of days absent
—
7 —
— 88 +
95
(9) Total quantity pd, pm
—
—
26 +
40 I
44 —
284
98
(10) Total value pd, pm
12
. —
6 -
46+
3 +
274 —
94
(11) Fuelpd
18-
8 1
3 +
—
324-
61
(12) Maintenance motor
28 I
. —
3 -
. —
„,..
27- —
58
( 1 3) Price of fresh herring
30-
—
53-
,. -
83
(14) Price of salt herring
—
—
87 -
— -
12+
— —
99
pd = per day; pm — per month.
In economics one has nearly always to do with many
variables which are nearly all intercorrclated. This gives
difficulties for the regression analysis. That is why for the past
couple of years Hildebrandt has been using the factor analysis
method, which takes into account the inter-correlations.
The preliminary results are found on the table of squared
factor loadings of 14 following variables:
(1) Abundance estimate of herring, which were received
from biologists
(2) Trend, the variable of time
(3) Value added per day absent per member of the crew
(4) Investment in the ship
(5) Net profit per day absent per member of the crew
(6) Horse power of the motor per man
(7) Gross tonnage per man
(8) Number of days absent
(9) Total quantity landed per day absent per man
(10) Total value landed per day absent per man
(11) Fuel per day
(12) Maintenance of motor
(13) Price of fresh herring
(14) Price of salt herring
The aim is also to learn what determines the profitability
of a fishing vessel. But what is the profitability of a fishing
vessel ?
The crew has no fixed remuneration, but gets a share of the
value of the fish landed. It is therefore that net profit is no
ideal measure for the profitability of the fishing vessel. A
better measure is the value added per member of the crew.
The value added is the sum of the shares, the net profit and
the calculated interest on the invested amount. It is the con-
tribution of the fishing industry to the national income.
For the analysis of this contribution he had chosen 14
variables. Of these variables a correlation-matrix has been
made. This correlation matrix has been divided into two
triangles: the root and the transposed root.
All this work is done by computer, otherwise it requires too
much time and labour.
The rank of the correlation matrix determines the number
of dimensions of the space in which one works. The direction
of the axes is not determined, but one can choose a number
of orthogonal axes as basis of this space. By means of
rotation of the orthogonal axes, the best plausible orthogonal
axes can be found. The result gives the table of squared
loadings. The square loadings in each column (the percentage
of variance) gives a measure of relation between the variables.
The plus or minus signs indicate in which direction the
variable varies. Each column represents a factor or aspect
interwoven with the variables represented in that column.
These aspects are orthogonal and as such independent of
each other.
What the table reveals
A point in the column means that in that column the
variable is not related with the other variables of that aspect.
The total of the percentages of the squared loadings for any
one variable tells how far the variable has been explained,
and has a maximum of 100.
What can be learnt from this table of squared loadings?
The first column gives the relation of distinguishing variables
with time — the trend. In the years 1955 till 1965 only 7 per
cent of the abundance estimate varied with 82 per cent of
the trend, but in opposite direction. This means that the
stock of herring was slightly declining.
In column III 9 per cent of the value added, 53 per cent of
the price of fresh and 87 per cent of the price of salt herring
varied with 41 per cent of the abundance estimate, but in
opposite direction. It also varies with 26 per cent of total
landings in the same direction, but with 6 per cent of total
value in the opposite direction.
This all means that better herring catches give higher
landings, but lower prices for fresh herring and especially
for salt herring, and also a lower total value of the landings
and a somewhat lower value added per member of the
crew.
The fourth column shows that at constant abundance
estimate and constant prices 42 per cent of the value added
varies at the same time with 40 per cent of total landings and
46 per cent of total value. More important is that independent
of this fourth column the seventh column shows that under
the same conditions 19 per cent of the value added varies
with 66 per cent of the investment, 28 per cent of the total
landings and 27 per cent of the total value. All in the same
direction. This means that higher investments give better
results. During the last ten years fishermen have built bigger
vessels in an effort to earn more. This meant replacing labour
by capital investments. It is a question of large scale produc-
tion. An optimal ship is often seen as static, but in reality it
changes with time. It is dynamic.
As Hamlisch shows: for developing countries technology
is most important. For the highly developed countries the
economic side of the question is very important too.
Of course it is not only a question of economics but also of
biology and technology. At any point therefore the biologist,
the technician and the economist have to co-operate.
Assessing complex factors
Doust (UK): Owners often have great difficulty in taking
decisions in fishing enterprises because of the complex situation
caused by the interrelation of both the technical and economic
factors. A few of these factors follow :
(a) Primary vessel characteristics, such as form, dimen-
sions, power, capacity, etc
[78]
<b) Secondary vessel characteristics involving stability,
seaworthiness, catchability
(c) Fishing grounds
(d) Port of landing
(e) Economic outgoing factors
(f ) Economic income factors
It is estimated that such decisions should be based on
approximately 58 variables, and each of these six sections
would require its own particular specialist. Hamlisch warns
us of the difliculties but gives nothing numerical, and it is
•essential to do so if we are to solve these problems. This can
be done by building up econometric models to ascertain in
which areas the main effort is required. From the economic
point of view, we can at present only take steps after a
situation has occurred, and a more econometric approach is
required before the introduction of a sound investment
policy. For such an approach the whole function of the
vessel must be presented numerically. As far as the present
state of knowledge in each section permits it is essential to
utilize the computer, so that the effects of change on profit-
ability and economic cfliciency in any one variable can be
estimated. For example, we could investigate the situation
where the catching rate is decreasing and the appropriate
changes could be made in the working model to derive the
adjustment of the optimum vessel size, or we could investigate
the relationship between skipper and size of vessel. For
instance, a top skipper obviously needs a different vessel to
the average. Another procedure could be to vary the skippers
by vessel rotation in order to obtain the best group profit.
The influence of shipbuilding costs on the best choice of
vessel for different grounds maintenance osts and engine
requirements for various speeds are typical factors which
require to be solved. As the capital investment costs of con-
struction steadily rise, it is logical that the invester will
require a greater economic and technical assurance that the
investment is sound. Only by utilizing the specialist services
of teams drawn from all the various branches of fisheries can
this be achieved.
Avoiding catch failure
Kojima (Japan): Hamlisch said that a scheme of catch-failure
insurance is important.
Kojima agreed with this opinion. Japanese fishermen have
established a mutual benefit society to insure catch-failure by
a mutual relief system. This society is licensed by national law,
and the Japanese Government disbursed £250,000 ($700,000)
as a portion of fund money for this society.
Fishing operations at sea are fatiguing, and accommodation
aboard some Japanese fishing vessels is considered poor, but
a policy is being promoted to improve conditions. An example
of the way in which this policy works is that an important
fishery may not be licensed to an owner who does not provide
certain standards of accommodation.
Thirdly, Kojima agreed with Hamlisch's opinion that the
fishing of one country may contribute to the growth of the
fishing in another country.
Kojima pointed out that although the fishing industry will
always employ cheap labour, that type of labour requires
machinery to make it viable, and therefore such devices must
be economic to buy and use if they are to have a place in
fishing.
Fourthly, Kojima mentioned the fondness of the Japanese
for fresh raw fish, which necessitates the use of special vessels
for bringing live fish from the grounds to market. These boats
have tanks below deck through which fresh scawater is
constantly circulated by pumps. By this method, live fish
have been carried 650 nautical miles (1,200 km) over a period
of three days.
Frechet (Canada): The fishermen need aboard the fishing
vessels certain essential facilities to make life pleasant. A
recreational area and pleasing surroundings are required in
this day and age to prevent fishermen from going to other
industries ashore where they can enjoy life in common with
their fellow citizens; a pleasing place on the pier is also
necessary, where they may discuss matters of common
interest and enjoy some relaxation. Naval architects must
always keep in mind that aboard fishing vessels, besides the
sleeping urea and the manoeuvring area, there is need for
space where fishermen may assemble and really live like
human beings.
Safety at sea
Lee (UK): Hamlisch is to be congratulated on the excellence
of his well-documented paper. Comment may seem superfluous
and he would mention only one item, namely the fatalism of
the fisherman in the face of death. Very considerable progress
has been made in recent years in the design of life-saving
equipment and in survival techniques generally. The chances
of human survival following disaster at sea are greater than
ever before and there is a welcome sign that seafarers, in
Western countries at least, arc taking full advantage of the
equipment now available to them. It is worthy of note also
that schoolchildren are receiving more and more instruction
in swimming, thus preparing them psychologically for
emergency at sea. The general attitude to survival is, there-
fore, likely to become very different from that which Hamlisch
describes as applying today.
Colvin (USA): Hamlisch has made an excellent contribution,
and Colvin was in agreement with his statements. He thought
it would be only fair to say that Hamlisch has put forth a
basic philosophy as it applies to the fishing industry through-
out the world. It is singular to note that in almost every
instance where the superstitions or customs of one country
retard the progress of the fishing industry, in some of the
other countries, especially one's own country, one can see
similar traits and characteristics among the individuals in a
collective group of fishermen.
The dissemination of information regarding the fishing
industry has always been left to the few. If it were not for the
FAG and for the papers put forth at the Technical Meetings,
there would be very little, if any, information available to
anyone aspiring to enter the fishing boat building or to
specialize as a naval architect in the design of fishing boats.
Capital expenditure
Eddie (UK): Nearly everything in Hamlisch's paper is true;
there is only one quarrel that Eddie had: The same old
argument is presented that technical progress must mean
higher capital expenditure. This is not inevitably so in terms
of weight of fish caught per unit expenditure as is evident in
the UK and Eddie suspected in other more recently developed
industries like the Russian, but the general effect, to Eddie's
mind is unnecessarily depressing. Perhaps it would have been
better to have attributed Hamlisch's paper to a development
engineer: they always suspect economists of being opposed
to technical innovations because these produce discon-
tinuities in the economic curves.
Be that as it may, the question is asked whether there is a
career for young people in fisheries development, and the
disturbing feature is that this question is not directly
answered but a negative answer is implied. This impression
needs counterbalancing especially since its origin was FAO.
Introducing technological changes may be more difficult
in fisheries than in other fields because the results are not so
predictable, but Eddie agreed with Chapelle that it is pro-
[79]
bably as difficult to introduce changes in developed countries
with a well-established industry as it is in the developing
countries. Developed countries have tabus and shortage of
capital, conservative fishermen and fish merchants and, of
course, the civil servants! The process of introducing an
innovation is never as orderly as they would like it to be
and never democratic — but the engineer can usually find an
individual who is in a position to give an innovation a trial.
Previous contributors have shown that there is every reason
for hope. Hamlisch's paper omits to mention two very
fundamental economic facts: the sea covers 7/10 of the
world's surface and receives as much sunshine per ma as
does the land. Perhaps because there was a length limit on
the papers, Hamlisch did not add another section on similar
lines to Jackson's introductory note in order to answer the
question he posed. Eddie suggested that the editor of the
proceedings print Hamlisch's paper immediately following
Jackson's introductory note, so that it will acquire therefrom
some of the hope and purpose that Jackson expressed so
well. (Editor: It is printed as first paper.)
Co-ordinate the techniques
Cardoso (Portugal): In coastal and middle distant waters
already intensely fished by old traditional methods, the
application of a more technological approach, the mechaniza-
tion and the rationalization of operations obtain immediately
a better productivity for each new ship.
This in turn initiates a rapid process of reconstruction and
renewal in the fishing fleet. Old ships, old gear and old
methods are discarded to meet the new competition. From
experience this may bring about the following chain of
events:
1. An enormous and quickly applied increase in the
fishing effort over a well-defined and naturally limited
stock.
2. A gradual falling off of the productivity of every vessel
fishing that stock.
3. Emergency regulations, often without a scientific
basis, are introduced, limiting the number and size of
vessels and sometimes the fishing areas and/or the
unloading ports.
It is not difficult to visualize that, in many instances, these
same regulations, added to the fact that fishing boats have to
go farther and faster in order to be profitable, strike at the
very heart of the process of technological progress and do not
help in achieving better designs.
Many a little "monster" is bound to be born, and in a way
technology defeated itself.
The point therefore is that all the techno-socio-economic
factors discussed have to be taken into account in a much
wider concept.
The technologist, the economist and the naval architect can
never correctly solve their problems before the oceano-
graphist and biologist have solved theirs. In many instances,
it is feared that naval architects may be a little too eager to
present the fishermen with the best boats to fish what is really
not known. Cardoso moved, therefore, that FAO should urge
every member nation to apply every possible effort to further
the study of oceanography and biology of the seas of the
world.
Jackson (FAO): In Cardoso's comment he suggested that
designers should wait for biologists and oceanologists to
provide information for the designers. However, one cannot
wait for the biologists for several reasons. Firstly, the sea
covers two-thirds of the earth surface and secondly a principal
tool of the biologist is the fisheries itself — therefore both must
develop together.
Jackson agreed with Hamlisch on two main points. For
developing countries :
1 . Transmission of technical information is not necessarily
followed by action. This is true and it is not enough
to publish the transactions of a meeting and simply
send it to the developing countries.
2. Lack of development results in hunger, but hunger
does not necessarily produce development.
The purposes of a meeting are also to promote national and
regional development and aid fishermen and the fishing
industry to compete in their own nations and regions.
Development is a difficult art and a slow one. It is not an
easy and orderly process. There are occasional opportunities
for giant steps and there the developments, promoted by
meetings such as this, are extremely useful. For example in
Ghana the step has been made from the canoe directly to the
operation of 50 factory stern trawlers without the intervening
steps.
Similarly, Rumania has leaped ahead from small coastal
vessels to the operation of 3,500 ton integrated factory stern
trawlers.
Jimenez (Peru): Commented on Jackson's words in saying
that the proceedings of previous fishing boat congresses have
been most helpful in developments in Peru.
Cardoso (Portugal): In reply to Jackson, Cardoso clarified
that he did not suggest that naval architects can wait for the
biologists and oceanologists.
As Jackson said, development must be simultaneous.
Speaking from experience, Cardoso merely pointed out that
the biologists' lack of knowledge is indeed hindering naval
architects' progress and many times even defeating the
purpose.
Consequently, Cardoso still maintained that it is of the
utmost importance that every effort be taken urgently for the
biologists to hurry up and provide, may be not all informa-
tion, but as much as possible.
Marketing and education
O'Connor (Ireland): Congratulated Eddie on his comments
on fisheries development work. He felt that the challenge
presented to young people in this sphere is a considerable
one and would form the basis of a very worthwhile career.
Cardoso called for expanded biological and occanographic
work and with this he agreed, but would look for a much
more commercial attitude from these people.
Two of the greatest problems facing expansion of fisheries
in any country are marketing and education. If these two
problems can be overcome, then fishermen will want better
boats, more young men will enter the industry and fishermen
will have a better income. The "revolution of rising expecta-
tions" referred to by Hamlisch, can be most easily brought
about by the provision of markets for all the fish the fisherman
can possibly catch.
On the question of education, O'Connor felt that part of
this problem concerns the education of the general public
to the acceptance of the important place the fisherman
occupies in the realm of food provision which is one of the
most important spheres of activity in the world today. If
one can build up in the fisherman also an improved morale,
so that he will live up to the new public impression of him
and his colleagues, then the demand coming from the catching
side will force naval architects and designers to provide the
standards of comfort and work ease which will match the
conditions the fisherman is accustomed to ashore.
Recruitment and training of new entrants to the industry
is looked after in Ireland through a state-financed scheme of
801
training new entrants and prospective skippers established
about five years ago. This scheme involves inspected com-
mercial fishing boats, navigational, boatmanship and manual
skill training in the naval service and in local vocational
schools. It has been successful as is proved by the fact that
some of the original trainees have now, after live short years
reached the stage where they can skipper boats of 56 to 65 ft
(17 to 20m) providing a net skipper income of upwards of
£2,000 ($5,800) per annum from reasonable effort.
The "resigned attitude of older fishermen" referred to by
Hamlisch can normally not be changed, but the effort should
be made to ensure that the younger members of the fraternity
grow up with a progressive outlook by proper educational
programmes and study tours to other countries, and also by
the expansion of a well-informed trade press.
FAO concept approved
Bjuke (Sweden): He was happy for FAQ's initiative of taking
up the social, economic and geographic factors for discussion.
Consideration to all these factors has to be taken for a
successful development of the fishery. Il is of no use to
introduce modern fishing boats in developing countries as
long as there arc no crews educated to navigate them, no
proper harbours for the boats, and no built-up organization
for processing and marketing of fish. The development of all
these matters has to be run parallel. A close co-ordination and
co-operation of the advisers for the various fields of the
fishery, therefore, is of the utmost importance.
Before the selection of a fishing centre L)r development,
there arc many factors to be care /j My studied. Physical and
geographical conditions of the site, fishing tradition and
distance to fishing grounds are not the om> decisive factors.
The site also should have resources to meet future growth in
fishing activity and should provide ample room for the
various ancillary operations and industries which are
associated with a thriving fishing centre, attractive residential
environments not to be neglected. Furthermore, the site
should have a convenient location with regard to the potential
market and should afford expedient facilities to dispatch
fresh fish to regions far off the coast. The vicinity of the
harbour to an airport would be an advantage, as in the future
the dispatch of fresh fish to distant places may be an ordinary
event.
Naval architects as well as harbour designers must con-
sider a proceeding development of types of boats all the way
from beach-landing catamarans to advanced vessels for large-
scale fishing. As to decide adequate depth of water in the
harbour basins, for instance, the draft of the vessels considered
has to be discussed together.
It would take too long time to state all details of desirable
co-operation. However, he was sure that FAG will push forward
strongly the question of consideration to be taken to all
factors concerning the development of fishing vessels as
well as the fishery as a whole.
Authors* replies
Hamlisch (FAO): Eddie had chidcd him for an alleged bias
against technological innovation and an unduly pessimistic
view on the potential contribution of fisheries to world food
supplies. Hamlisch pleaded "not guilty" on both counts.
He did not think Eddie really wanted to question the
validity of the observation that technical progress tends to
increase the size of capital investment in fishing (this, after
all, is a characteristic feature of progressive industrialization).
The difference in the cost of a modern, fully equipped long
distance trawler and a traditional craft fishing in coastal
waters is a very substantial one. The entrepreneur is aware of
the greater "capital efficiency" of the larger, more expensive,
craft and has modernized, and will continue to modernize,
where the anticipated increase in net economic returns seems
to warrant this. In his paper, Hamlisch was merely implying
that the increase in the financial burden and in the break-
even catch value compel the entrepreneur to do his investment
planning more carefully. He hoped technological advances
will be promoted by governments and industry, wherever
physical, economic, and social conditions appear favourable
for the adoption.
Hamlisch's attitude of caution, which Eddie felt inclined to
interpret as pessimism, derives from the economist's obliga-
tion to insist on a balanced approach in development work.
The physical scientists want to give priority to searching the
oceans for more fish, the technologists to improving catching
equipment and methods, the chemists to development of
better products. The economists introduce the questions
Hamlisch touched on in his paper: is the market ready and
equipped to absorb the additional quantities of fish; is the
producer able to operate the improved equipment; is the
institutional structure flexible enough to adjust to the changed
mode of operation; is the investor prepared to make the
plunge? The economists' priorities shift with the discovery of
new lags; they argue that any sector lagging behind should
be first brought up to the same level as the other sectors
before radical advances are made on a new front.
There arc those who believe that the Fisheries Revolution
is just around the corner, that fisheries development should
have an over-riding priority, since the world will, before long,
badly need the harvest of the seas to feed itself. Hamlisch was
the last to argue that this may not be the ease in the long run.
He was much more doubtful about the situation in the near
futiuc. There is a highly respected school of thought that
urges us to concentrate on the short time span, considering
the difficulty of imagining, not to speak of predicting, what
revolutionary scientific and technological developments may
take place in various sectors of the economy over the next
few decades.*
As several writers (Hamlisch and Taylor, 1962) have noted,
per capita consumption of edible fish has remained stable or
even has been on the decline in recent years in some of the
richer, developed countries. The trend cannot be blamed only
on the condition of fish stocks and on the lack of technical
know-how. Hamlisch suspected that the phenomenon is due
in large measure to a merchandizing failure. He thought the
trend is not irreversible if imaginative promotional techniques
are applied.
In developing countries, technical progress has not always
automatically brought along the expected nutritional and
income effects. One could think of several conspicuous
examples of moth-balled or underutilized or excess fleet and
plant capacity, where failure of systematic planning or lack
of balance in the growth of the different sectors of the
industry has been responsible for substantial economic-
waste.
Final note of caution
It may be argued that major development requires an
initial spurt— involving a certain measure of gamble -on
* Professor Gunnar Myrdal, the distinguished Swedish economist,
stated this point of view most effectively in his 1965 MeDougall
Memorial Lecture at the opening of the 1965 FAO Conference:
"... I feel much less concerned about how things will look at the
turn of the next century. In the long run much will happen: we will
perhaps have entirely new techniques to produce the food; the
entire world situation will be different in all sorts of ways; forecasts
are bound to be proven wrong: perhaps we may feel optimistic
that things will in some way take a radically new turn as we have
often seen happening before. It is the years to come in this decade
and the next about which 1 am worried. In the short run our
forecasts are more reliable. . . . **
[81]
some front. The question must be raised to what extent
developing countries can afford to put on risk a large share
of the limited financial and managerial resources at their
disposal. The decision as to whether, and if so on what
scale, a developing country should launch major fishing
ventures to substitute fishery imports can only be made on
consideration of overall economic and political objectives of
the government. It is wrong to think in terms of global
priorities, both with respect to fisheries within general
economic development, and with regard to emphasis to be
given to the different aspects of fisheries development. Even
within a given region or country, priorities will change with
time. Where yesterday the crucial problem may have been
in the technological sphere, today it may be the resource
condition, and tomorrow the marketing situation.
On Eddie's comment on Hamlisch's failure to give a general
reply to the young man who weighs the pros and cons of
becoming a naval architect or boat builder: the young man
will have to answer this question himself, in the light of the
peculiar characteristics of the "market" for these professions
in his country. All Hamlisch set out to and could do in his
note was to discuss the "demand*' considerations that would
bear on the decision.
Hamlisch fully shared Doust's desire to find a quantitative
expression for the various factors on which investment
policies should be based. Fortunately, there are able
researchers (such as Doust himself) already at work on these
problems. FAO does not have the facilities nor the man-
power to undertake such research. FAO is very keen, however,
on assembling and eventually disseminating information on
research progress in this field and to make a contribution,
in this manner, to the expansion of knowledge.
One word of caution: the large number of assumptions,
many of which are based on very inadequate empirical data,
docs not yet permit the use of some of the econometric
models for forecasts of a desired degree of reliability. For
some time to come, therefore, the models will remain in the
category of "direction finders". Within the frame of these
models it should, however, become possible to make timely
adjustments of forecasts, when additional data become
available.
Takagi (Japan): In answer to de Wit, Takagi added that
non-powered boats operate only in the best season and
therefore give the maximum results of earning per man-
hour. On the other hand, powered boats operate throughout
the year and give lower results. Therefore, fishermen want to
have high-speed powered boats for fishing all the year.
Mechanization of non-powered boats is to improve the
productivity and total fish catch if there is an abundance of
fish. In Japan, however, there are too many powered boats
on limited fishing areas and their catches are small. Takagi
hoped that mechanization in developing countries will not
lead to the same situation.
[82]
PART II
PERFORMANCE
Measurements on Two Inshore Fishing Vessels 717. Hat fie Id New Possibilities for Improvement in the Design of Fishing
Vessels . . J. O. Traung, /). J. Doust and J. G. Hayes
Technical Survey of Traditional Small Fishing Vessels
N. Yokoyama, T. Tsuchiya, T. Kobayashi and Y. Kanayama A Free Surface 'lank as an Anti-Rolling Device for Fishing
Vessels . . . . . J. J. van den Bosch
Methode de Projet des Nouveaux Types de Na vires de Peche
E. R. Giwroult Catamarans as Commercial Fishing Vessels
Frank R. Mac Lear
A Statistical Analysis of FAO Resistance Data for Fishing
Craft . . D. J. Doust, J. G. Hayes and T. Tsuchiya Discussion
Measurements on Two Inshore
Fishing Vessels
by M. Hatfield
Essais dc deux bailments de peche coticrc
L'Industrial Development Unit dc la White Fish Authority a
soumis a unc seric complete dc mesures (charges, vitcsscs ct puis-
sances) deux bailments eeossais de peche coticrc commercial de
70 pieds (21 m): le senneur Opportune II ct Ic Roscbloom,
recemmcnt converti pour le chalutage. Les cssais en mcr. d'unc
duree dc cinq jours pour chacun des bateaux, ont porte tant sur la
marchc librc que sur Failure dc pcchc. Ccttc etude visait a obtenir
des renseignerncnts dc base sur le dcssin des bailments a 1'intention
dc plusieurs programmes ct etudes de developpement ayant pour
objct 1'amelioration de ce type de bateau des points de vue tech-
nique ct economique.
Mediciones en dos embarcaciones de pcsca de bajura
La 'Industrial Development Unit' de la 'White Fish Authority'
ha rcalizado una amplia seric dc mcdiciones de cargas, vclocidadcs
y potcncias en dos embarcaciones comcrciales escocesas de pcsca
dc hajura de 70 pies (21 m), una de las cuales, la Opportune //, es
un barco de redes de cerco, y la otra, el Rosehlooni, se ha convert ido
rccicntcmente en arrastrero. Las mcdiciones abarcaban la marcha
librc y las condiciones pesqueras duranlc las pruebas en el mar que
duraron cinco dias en cada caso. LI objcto de estas investigacioncs
era ohtencr la information del diseno basico para cierto numcro dc
proycctos y cstudios de desarrollo encaminados a mejorar este tipo
de embarcacion, lanto desde el punto dc vista tccnico como del
economico.
THH inshore fishing lleet numbers some 1,500
vessels, between 50 and 80 ft (15 to 24 m) in
overall length, operating from ports all around the
British coast. These vessels spend the '-hole or part of
the year fishing for demersal species, the majority using
seine nets. Their design and their machinery has been a
long evolutionary process, and although they generally
operate effectively with a high level of productivity,
opportunities of invest'gating possible alternative equip-
ments and designs have been neglected due, partly, to a
lack of systematic development. It was fell therefore that
designers and operators may be able to profit from basic
investigations into their performance, with particular
icference to power requirements at the propeller and
winch.
The urgency of this work has been emphasi/cd by a
recent trend for numbers of this class of vessel to convert
from seine netting to trawling, which is regarded by
some as a more profitable method. The power require-
ments for trawling, for a 70 ft (21 m) vessel, were even
more debatable than those for a distant-water trawler.
Two sets of performance trials were performed, one
Fig J. MTV Opportune II
F851
Fig 2 , MFV Rosebloom
Building date
Skipper
Hull dimensions and materials
Loa
Breadth
Lpp
GT
TABU. 1 . Seine netter, Opportune II
December 1956 Builders
G. Murray Register
Engine details
69 ft 9 in (21. 25m)
20 ft 4 in ( 6.20 m)
66 ft 8 in (20.32 m)
51.9
Hull of wooden construction with aluminium superstructure
Winch details
6-specd seine winch, belt drive from engine-driven layshuft.
Winch builders Sutherlands, Lossiemoulh
Fishing gear details
Warps: 2}- in (64 mm) manila seine rope in 125 fm (228.6 m)
coils 15 fm (27.4 m) bridles
Footropc: 1.75 in (45 mm) combination wire protected by "Grass
Rope" and weighted by lead rings
Herd and Mackenzie
Buckie, BanfTshire
BCK 60
Gardner 8L3 8 cyl oil engine rating 150 hp at 900 rpm
Drive to propeller through 3:1 reduction gearbox. Winch
layshafl drive through 2:1 reduction gearbox
Propeller details (fixed pitch)
Diameter
Pitch ratio
Blade area ratio
52 in (132(.)mm)
O.S75
0.47
Net: 520S polythene Gourock trawl net 520 f>] in (159 mm)
mesh around mouth. Headline 90 ft (27.4 m). Hurt rope
110ft (33.5m)
Floats: 7 small floats on each wing, 4 large floats on headline
Building date (seine netter)
(converted to trawler)
Skipper
Register
TABLE 2. Trawler, Rosebloom
1959 Builders (seine netter)
mid- 1963
T. Ross (converted to trawler)
1NS.94
Hull dimensions and materials
Loa 73 ft (22.25 m)
Breadth 20 ft 4 in (6.20 m)
Lpp 68 ft 7 in (20.90 m)
Hull of wooden construction with aluminium superstructure
W inch details
Twin-barrel winch with band brakes and friction clutches, carrying
400 fm (725 m) 1 A in (38 mm) GSWR warp, belt drive from
engine-driven layshaft. Winch builders Andre. Hensen and
S0nncr
Fishing gear details
Nets: "A" 1.65 in (42mm) mesh around mouth, 4.5 in (114mm)
mesh in bosom. 2.75 in (70 mm) mesh in belly and codend.
Headline 80 ft (24.38 m), groundrope 100 ft (30.48 m) 10 Standard
aluminium floats on headline, 3 in (76 mm) rubbers on ground-
rope and legs, groundrope heavily chained. Sweeps 15 fm
(27.43 m). Spreaders 40 fm (73.15 m) *'B" mesh sizes as for
light net "A". Headline 90 ft (27.4 m). Groundrope 110 ft
(33.5 m). 15 aluminium floats on headline
Herd and Mackenzie
Buckie, Banfl shire
H. Meet wood
Lossiemouth,
Morayshire
Engine details (after conversion)
Caterpillar 6 cyl oil engine rating 325 hp at 1,800 rpm
Drive to propeller through 4.5:1 reduction gearbox. Winch
layshaft drive through 4:1 reduction gearbox
Propeller details
Diameter
Pitch ratio
Blade area ratio
53 in (1346 mm)
0.811
0.47
Warps: 425 fm (777 m). 1.5 in (38 mm) GSWR warp
Trawl doors:
Doors "A" 4x3 ft (1.22x0.91 m) 6 in. (152 mm). Weight
3 cwt (150 kg) approx.
Doors "B" 6x3 ft 6 in (1.83x0.91 m) 6 in (152 mm).
Gear normally rigged with heavy net and light doors
[86]
on a typical, fairly modern, 70 ft (21 m) seine net vessel,
the other on a similar vessel converted for trawling.
Particular reference is made to the measurement of
warp load. Not only was this an essential measurement
for the purposes of the investigations but also the
equipment used was the prototype of a warp loadmetcr
system for use in commercial fishing.
THE VESSELS
Except for engine power and fishing gear, the vessels are
very similar in design. The details are given in tables 1
and 2. The trials were carried out at a time of year when
fishing is usually good and the vessels in continuous
operation.
INSTRUMENTATION
Trials instrumentation
The measured quantities arc listed in table 3. All instru-
ments, with the exception of those for wind speed and
direction, had electrical outputs which were fed through
simple electrical balance and smoothing circuits, without
amplification into an 18-channel ultra-violet galvano-
meter recorder. All signals were thus recorded continu-
ously and simultaneously, and since the galvanometers
have a high frequency response, the effects of ship
motion could be studied.
The instruments for the parameters shown in table 3
Fig 3. Instrumented portion of a special intermediate shaft
Fig 4. Intermediate shaft undergoing thrust calibration
Parameter
Propeller shaft torque
Propeller shaft thrust
Propeller shaft revolutions
Winch layshaft torque
Winch layshaft revolutions
Warp load (port and starboard)
Warp speed (port and starboard)
Pitch
Roll
Vertical acceleration "|
Longitudinal acceleration >
Lateral acceleration J
Ship speed
Wind speed
Wind direction
TABU-. 3. Measurement of parameters
Method of measurement
Strain gauges bonded to special hollow intermediate shaft. Supply and signal to gauge
bridges by silver slip rings and silver/graphite brushes. Shaft calibrated in torsion and
compression testing machines
Magnet and reed switch
Strain gauges bonded to shaft. Calibrated in torsion testing machine
Magnet and reed switch
Strain gauges on link supporting pulleys (see fig 9 and 11)
Seine netter: magnet and reed switch on coil drive
Trawler: magnet and reed switch on fair-lead pulley visually checked against warp marks
A 2-axis gyroscope in the accommodation space
A 3-axis accclcrometer, mounted below the winch
A Walker "Trident" log. Calibrated on measured mile trials
An R. W. Munro anemometer
Burgee
[8?;
were calibrated before the beginning of the trials. The
rigs used in the calibration of the intermediate shafts for
thrust and torque are shown in fig 4 and 5 respectively.
With the exception of one or two commercially available
items, the equipment up to the recorder input was de-
signed, made and installed by the staff of the Industrial
Development Unit.
Fig 5, Intermediate shaft undergoing torque calibration
The recording equipment aboard the Rosebloom is
shown in fig 6 and a typical section of trace record from
the galvanometer recorder appears in fig 7.
Warp loadmeters
It was hoped that these meters would prove to be as
useful as similar instruments fitted to distant-water stern
Fig 6. Recording equipment
I sec timing marks •
^rations
Fig 7. Section of recorder film during trials
[88]
Fishing on port »de
Instrunwittd iwtvel
fairkwd pulleys (A)
Fishing on stqrboord side
Fig 8. Layout of warps on seine nctter
trawlers, in giving warning of fasteners, indicating
whether the gear is fishing properly, assisting the skipper
in setting his power in conditions of strong tide, etc.
The basic test procedure was similar for both vessels.
Jt consists of measuring the reaction load on a pulley
which is positioned to cause a known change of direction
in the warp run. Provided the angle of wrap of the warp
round the pulley remains constant then the load on the
pulley is directly proportional to the tension in the warp,
whether it is moving or stationary.
Fig 9. Warp loadmeter on seine netter
The pulleys referred to were mounted on specially
designed brackets which were fitted with electrical
resistance strain gauges to measure the load. For the
trials, the signals from these gauges were fed into the
recorder as described above. For the prototype com-
mercial system, however, the signals were fed into
dial indicators commercially available in Great Britain.
These indicators, which arc fed with the raw 24-volt ship's
supply, consist of a voltage stabilizing unit, a DC
amplifier, and a millivoltmeter, giving a pointer readout of
load on a 3-in (76 mm) diameter scale. Fig 8 and 10
show the warp layouts and installation details on the
two vessels.
(a) Seine net vessel, fig 9: The forward fairlead pulleys
(A on fig 8) were selected as the only suitable location
for a meter because fishing is carried out from either the
port or starboard side and they are the only pulleys
continuously in operation. On the standard Scottish
seine net vessel these pulleys are mounted on a simple
carriage which is slid athwartships by one pulley dia-
meter when changing from port to starboard fishing.
Measurement of load on this existing arrangement was
discarded in favour of mounting the pulleys on a specially
designed swivel arm of the same radius. This arm was
fitted with the strain gauges. Since it is free to swivel, it
performs the same function with regard to warp align-
ment as did the sliding carriage.
Fig //• Warp loadmeter on I 'raw ier
Fig 12. Calibration of warp loadmeter on trawler
Fig 10. Layout of warps on trawler
Fig 12a. Warp load indicators in wheelhouse of trawler
89
(b) Trawler, fig 11: The winch shaft lies fore and aft,
and the fairleads on the starboard bulwark, over which
the warps pass at 90l angles, are ideally situated for the
measurement of load, using specially designed strain
gauged brackets.
On both vessels calibration of the warp loadmeters was
carried out in situ by fixing a warp over the pulleys in the
configuration which occurs in normal use and applying
known loads by a turnbucklc and spring balance (fig 12).
TRIALS PROCEDURE
Free running — measured mile trials
The measured mile at Kilmuir, near Inverness, is sheltered
by hills and at the time of both trials the sea was flat calm
with negligible wind. Particulars are:
Position: approx 57° 35' N, 4° 13' W
Course: 025, 300 yds (275 m) offshore
Length: 6,093 ft (1,852 m)
Depth: 4 to 8 fm (8 to 16 m)
The procedure was to select an engine speed for each
run and allow about 5 min for engine conditions to
stabilize. The ship was then steadied on course about a
half to three-quarters of a mile (1 km) from the first
post and the recorder started. The time taken to cover
the measured distance was taken by stopwatch, and the
recorder trace record was marked at each post. The ship
was run for about three-quarters of a mile (1 km) past
the second post before switching off the recorder.
Wind speed and direction were read. In the trials of the
Opportune II the ship's speed log was seen to be reading
high by about \2\ per cent. The records taken on the
mile were used to provide a correction for the subsequent
trials. In the case of the Rosebloom the log was corrected
during the first few runs on the mile. The powers ranged
from full power down to about 15 per cent of maximum.
Tn the case of the Rosebloom one pair of runs was
included with the trawl down, primarily to check the
log at very low speed.
Free running performance —open sea
Throughout the subsequent trials in commercial fishing
conditions an attempt was made to ascertain, wherever
possible, the effect of weather, sea state, deep water etc.,
on the calm water measured mile performance. Usually
this was done by taking a complete set of readings at
regular intervals on journeys to and from the fishing
grounds. In the case of the Opportune //an additional set
of readings was taken at reduced powers on one occasion
when maximum ship's speed had been reduced by bad
weather.
Fishing trials
Selection of grounds: For most of the skippers operating
in this area the selection of grounds is based largely on
experience of the likelihood of obtaining marketable
fish, taking into account knowledge of weather, time of
year, time of month, location of most profitable markets
and so on. The choice of the actual spot at which to
shoot the gear is governed partly by the fish finder, if
this is being used, but is very much influenced by the
location of hard ground and snags. This applies par-
ticularly to the seine net operation using very light gear.
Tn recent years many of the more successful skippers
have been fishing increasingly close to wrecks and hard
ground, locating these features with great accuracy
using the Decca Navigator and continuously building up
fishing charts on that system. Mutual exchange of in-
formation on this aspect is common between skippers.
Fishing methods during trials:
(a) Seine net fishing: The direction and speed of the
operation, the length of warp and the selection of port
or starboard fishing depend largely on wind and tide
direction relative to the ship and the type of gear used.
Bottom topography is also important in some cases. In
some situations, it is considered advisable to tow against
the tide but with it in others. The warp length paid out
varies considerably over the range of conditions and is
not necessarily a function of depth. The skipper of the
Opportune II has used from four to 15 coils (500 to
1,875 fm or 900 to 3,500 m) per side in a recent six-
month period.
The fishing cycle is as follows: Having decided from
which side of the vessel the tow is to be taken, the warp
on the opposite side is paid away from a dhan buoy at
about 20° from the desired line of tow, in the opposite
direction ("shooting the first leg"). When about 80 per
cent of this warp is paid out, the vessel turns sharply to
cross the line of tow at right angles. At the end of the
first warp, the net is paid out followed by 20 per cent of
the second warp ("shooting the second leg"). The vessel
then turns again to return to the buoy and pays out the
remainder of the second warp up to the dhan buoy
("shooting the third leg"). The two free ends are then
passed over the various fairleads, winch and coiler and
fishing commences.
On the Opportune II it is the usual practice to start
fishing with a short tow of about 5 to 10 min. The winch
is then started in first gear which is usually maintained
until the net starts to close although second and third
gear may be cnaged in certain tide conditions. When the
net starts to close and lift, fourth, fifth and sometimes
sixth gear are used to reduce non-profitable handling
time.
During the entire operation the vessel moves very
slowly through the water but the ground speed, of
course, depends on the tide conditions. If a snag or
fastener is encountered during this operation, the action
taken depends on some sort of assessment of the type of
snag and the likelihood of loss of gear against loss of
catch so that
• if the snag appears to be a "soft" one, e.g. the
rope or trawl digging into mud, the skipper would
continue forward, possibly at increased power, to
try to pull the net free. Or,
• if the gear appeared to be caught fast he would
stop hauling and retrace his path over the net in an
effort to save the net at the expense of the fish
already caught
The provision of an instrument to assist in making the
right decision in this situation is one of the main reasons;
[90]
for development of a warp loadmeter for this type of
vessel. The first seine net warp loadmeters, were built
by the Marine Laboratory in Aberdeen and used on
FRY Mara but to speed commercial application the idea
was handed over to the WFA industrial development
unit. (Dickson and Mowat, 1963.)
(b) Trawling: The general method of trawling on the
Rosebloom is virtually identical to side trawling on
larger vessels. Long spreading wires are used (40 fin or
73 m) which are wound directly on to the winch barrels
when hauling, after the sweep wires. The length of warp
paid out relative to the depth varies much more than is
the case on distant-water trawlers. Jt is general practice to
use as much warp as experience has shown can be towed
over a particular ground, up to 425 fm (850 m) carried
on the winch. Warp length to depth ratios of up to 10 : 1
are not uncommon. The crew can turn round the fishing
gear from knocking-out to squaring-up in about 30 min
even with 425 fm (850 m) of warp and 40 fm (73 m)
spreading wires and since fairly long tows arc usual (4
hours in normal fishing) there is a high ratio of fishing to
handling time.
Trials procedure: Both skippers were requested to carry
out normal fishing operations until sufficient records were
taken, the only interference with normal procedure
being to request a variety of depths and bottoms and
some deliberate fasteners or sna^s. Sometimes an entire
operation was recorded, but at other times the recorder
was run intermittently, although for several minutes at a
time. A code of event marks was used to indicate
signicant events on the trace record and visual readings
of wind and weather were taken regularly.
On the Opportune II the bulk of the fishing trials was
-done at about 58° 28' N, 2° W and 58" 45' N, 1.5° W
;" 150 •
734567B9
Ships Lpppd - Knot s
lig JJ. l-'rfn'-running power-xpeed characteristic. A Opportune 11
B Rosebloom
on 4th and 5th May 1965, with additional work in the
Moray Firth on 3rd and late 5th May. Table 4 gives
the lishing records list.
The skipper took the Rosebloom through the Pentland
Firth, fishing on two grounds. Stormy Bank (58° 55' N,
4° W) and The Noup (59° 23' N, 3° 35' W). In addition to
TAIJLL 4. List of hauls — seine netter, Opportune II
Ref.
A//I
Date
May
Time
start
Depth
Coils
per
Bottom
Approx.
catch
Remarks
/Vc7.
1965
shoot
fm
m
side
stones
kK
H.l
3
0400
18/22
33/40
10
Sand
20
125
H.2
3
0615
58/60
106/110
10
Mud
30
190
H.3
3
0925
50
90
11
Sand/mud
Broke port warp
H.4
3
1020
55
100
11
Hard
40
225
Several deliberate snags
H.5
3
1340
45/60
80/110
11
Sand/mud
20
125
H.6
4
1645
50
90
11
Mud
150
950
H.7
4
1750
55
KM)
11
Mud
350
2,220
H.8
4
1950
55
100
11
Mud
200
1,270
H.9
5
0400
110/80
200/145
10
Hard
Snag steamed back
H.10
5
0600
JOO
180
10
Hard
„_
Snag pulled clear
H.ll
5
1750
20
36
8
Chain in place of net
to
catch snag
TAULL 5. List of hauls trawler, Rosebloom
Ref.
No,
H.I
H.2
H.3
H.4
H.5
H.6
H.7
H.8
H.9
Date
July
1965
JO
11
11
11
11
12
12
12
12
Time
start
shoot
1530
0600
09(K)
1530
2050
0135
0630
1030
1300
fm
5
60
60
86/98
85/95
90
100
100
100
Depth
9
110
110
160/180
155/175
165
180
180
180
Warp
length
300
250
425
425
425
425
425
550
460
780
780
780
780
780
Hot torn
Sand/stones
Sand
Sand
Mud
Mud
Mud
Mud
Mud
240
160
240
320
240
160
160
Appro\
catch
kg
Net
Doors
A
A
,525
A
A
—
A
A
,025
B
A
,525
B
A
2,030
B
A
,525
B
A
,015
B
B
,015
A
B
[91]
numerous records of normal fishing operations, the
effect of towing at various propeller revolutions was
investigated systematically on tow H7 of table 5 which
lists the various records taken.
where T (Ib) : measured thrust
V (ft/sec) : ship's speed
N : propeller rpm
Q (ft/lb) : shaft torque.
TRIALS RESULTS
Analysis work is still in hand on some of the trace
records taken during the trials, particularly on the
Rosebloom work. The results given here and the observa-
tions on them refer only to the data analysed to date.
Further information will be published by the While Fish
Authority in Technical Memoranda.
Free running — measured mile trials results
The curves of propeller shaft power against ship speed
for both vessels arc shown in fig 13. Both sets of tests were
run under conditions of flat calm and the plotted points
are each the mean of two runs, one in each direction.
The other relevant parameters including propeller thrust
(Pt) are plotted against propeller rpm in fig 14 and 15
for the Opportune IJ and Rosebloom, respectively.
Also on fig 14 and 15 an apparent propulsive efficiency
(7?) has been plotted. Since there is no model or full-scale
data from which to obtain thrust deduction fractions or
wake fractions, it is not possible to produce either the
propeller or propulsive efficiencies as usually defined.
The apparent propulsive efficiency, therefore, has been
obtained by dividing the thrust horsepower
TV
33,000
by the propeller shaft power
2rrNQ
33,000
X
2*° 760 2(0 )00 320 340 360 380 400
•Shaft rpm
Fig 15. Rosebloom : Free-running power characteristic
Free running — open sea trials results
As mentioned earlier, a set of readings was taken ai
varying powers on Opportune 77, in weather Beaufori
Number 5 wind force and with a sea state producing
angles of pitch and roll up to the order of [3 and _L 10
respectively. The power versus speed curve for thai
condition is shown (fig 16) and the other relevant
parameters arc plotted against propeller rpm (fig 17).
,„, ! . ., , ,
f1«0 110 200 220 240 260 280 300 920
Shall r p n.
Fig 14. Opportune II: Free-running power characteristic
a 80
OJ
5 6 7 ft 9
ShlptSpMd Knot*
Fig 16. Opportune II : Power! speed characteristic in open waters.
Beaufort Number 5. Pitch Angles up to -J- 3". Roll angles up to ± 70"
[92
Co)
120" 2400
4/1 10(H ~ 2200
3 I
I or I
1 u I I
10 1 £ 2000Uy> "Cm
«4:r !
,*
»!
60 &
'1800
17. Opportune II: tree-running power characteristic in open
water. Pitch angles up to i- .? . Roll angles up to . ! M
The other open sea tests consisted of taking a set of
readings at nominal full power setting in as wide a
variety of weathers as possible. Because of the erratic
nature of the ship motion it is difficult, however, to settle
on a reliable criterion when quoting angles of pitch and
roll for any given condition. On these particular records
it was observed that the second largest amplitude usually
recurred frequently on any given occasion and this value
has, therefore, been quoted throughout this paper. When
time permits, a more detailed analysis will be carried out.
Also, engine rpm was not set precisely at the same
value on each occasion so that to reduce scatter from
that cause all powers and thrusts have been corrected
to the nominal maximum 313 rpm. The results of these
particular tests are listed in table 6. Kach of the tabulated
values is the average value over a long record except
for the ship motion figures.
Fishing trials results
Seine net vessel: Fig 18 and 19 give the results of the
analysis of one complete cycle. No. HI, in which,
during the haul, all six gear ratios were used in the winch
drive although this would not necessarily occur in
practice. Fig 19 gives the information relating to the
winch and the warps and fig 18 gives the ship and pro-
TAHI i 6 Effect of ship motion.
Opportune II free running
Ship pitch angle
Prop torque
,
Prop thrust
Ship speed
Thrust
•_: degree
Ib/Ji
kg/m
Ib kg
knots
hp
0
2,520
349
i50
3.250 1,470
8.3
81.5
1
2,520
349
150
3,250 1 ,470
8.3
81.5
1.5
2,470
342
148
3,550
,620
8.1
89.6
2.5
2,520
349
150
3.600
,640
8.2
90.0
3
2,570
355
154
3,620
,650
8.06
99.6
4.5
2,600
360
155
3,700
,700
7.85
90.0
7.5
2,620
362
156
3,700
,700
7.8
89.6
250T
20-
VT>
E 200
Q.
15
-
0.
0
±>
lOOi
£ 150
10
80
0.
* 60
100-
5:
| 40
1 15i
<o
S© :
75
20J
S 1-0:
£ :
50
40
*-'!
2 5
30-
or 0^
;
CL
0^
i 20-
,« 100
2 10-
t
o.
UJ
0J
o 50
i
{©:
* n .
©
Sequence of Events
Hg 18. Opportune II: Fishing cycle, Haul HI Ship Data
[93]
TABLE 7. SHP and warp powers related to catch, Opportune II
Rtf. *ssr D"*
stones kg fm m
Hauling
in gear
SHP
warp u
Port
cwt kg
ma
Starboard
cwt kg
Total warp
power hp
H.9 — 100 185
1
5.8
12.1
615
8.0
410
5.45
47.3
9.6
490
9.4
480
5.45
2
47.3
9.6
490
9.4
480
7.0
47.3
10.6
540
9.4
480
7.35
5
26.8
4.55
230
6.1
310
10.2
26.8
6.6
335
3.3
165
10.1
H.I 20 125 20 36
1
45
9.2
465
8.7
440
4.95
47.1
8.67
440
8.5
430
4.85
2
48
8.98
455
8.7
440
5.9
3
45.5
8.28
420
8.15
415
7.71
4
40
8.05
410
8.25
420
15.3
5
32
7.53
380
7.11
360
15
6
15.25
4.4
225
5.1
260
10.75
H.6 150 950 50 90
1
53.2
10.6
540
10.3
525
6.0
2
53.7
11.1
565
10.3
525
7.5
53.7
9.6
490
9.5
485
6.65
5
26.4
9.1
460
8.5
430
16.85
29.0
9.6
490
8.0
410
17.5
H.7 350 2,220 55 100
1
54.2
9,6
490
10.3
525
7.75
53
9.6
490
10.3
525
7.75
2
53
9.6
490
10.3
525
6.82
51.4
9.1
460
9.5
485
6.4
5
36.4
9.6
490
9.8
500
20.1
35.4
9.6
490
9.0
455
19.7
peller parameters. Although the trace record was ana-
lysed at 30-sec intervals the results have been averaged
over several minutes for plotting, except where sudden
changes occur. Warp horsepower (fig 19) is the total
output winch power obtained from the product of the
two warp loads and their linear speed. The winch
efficiency is this warp power divided by the input power
to the winch.
300
Table 7 summarizes some of the hauling characteristics
on four hauls on which both size of catch and depth
varied considerably. Some typical effects of ship motion
are shown in table 8, in which the pitch and roll values
are given.
Figures 20 and 21 show the time history of catching a
snag. In the first case, fig 20, the first action taken was to
de-clutch the winch, then when the warp tension was
Fig 19. Opportune II: Fishing cycle, Haul HI. Fishing gear data
[94]
TABLE 8. Haul H6— effect of ship motion on loads during haul, Opportune 77
P't / R 11 ^°rt Warjy tension Winch shaft torque Propeller shaft torque Propeller thrust
Condition ^. ^ _j_. ^ Mean Oscil ± Mean Oscil ± Mean Oscil ± Mean Oscil ±
cwt kg cwt kg Ib/ft kg/m Ib/ft
kg/m Ih/ft kg/m Ib/ft kg/m Ib kg Ib kg
Start haul 1st gear 4 11 11 560 1 50
1,500 207 240 P 33.2 2,540 ,150 420 P 190
End haul 1st gear 2 11 10 510 .75 38
1,460 202 150 P 20.7 2,540 ,150 250 P 115
Hauling 2nd gear 2 17 9.5485 .75 38 17524.2 22
3.04 1,460 202 180 P 24.9 2,540 ,150 340 P 115
Hauling 5th gear 2 10 9 455 2 100 51070.5 1 50 P 20.7
Towing, net surfacing 4 2 4 205 1 R 50
1,250173 1 50 P 20.7 2,540 ,1501 TOP 75
Towing, net surfacing 4 8 10 510 10 R 510
1,250173 150 P 20.7 2,540 ,150 170 P 75
20 -
1 5
...-*. \ WorpLooda
j Warp Load*
___.•<' ,^' \ Cwt
j Cwt
10 -
i " _ _ . ,/ Sld \ -•' ~~"t 10
----- ' " ~ \
\ "" i
0
1 5
"v-:::--"':; '
250 | /''" *" 35°°
-._.
J /' lToZ.ro W.nchTorqu. m™
..-^"'" ~"-. . - _. Prop, Thru*!
\ ; " " -
\ / - __.._ Ib
200 -j "" Ib f*tl
X j " " —
Winch J500
150
dt-eluteh.d
•" ~ 2000
3000 -
j _ •- _ Prop Torque
Prop Thru»l
/ "*• --. .. lb •«•
\ / -••- — •
- - "i ib
.^--' 1 1500
/
2500 -
__^--"' *
~"" 250T Prop R»v».
200
----.. P»r Mm
1500 -
• — ~~ "J Prop Sho«l 150
Torqu* Ib
— ...
1000 -
2
Ship'* 5p»»d
Engmt
Knol»
• .
™" 1
1 ° "1 V
\^ Ship* Sp»»d ,
~~"--^ Knot* 0
20 40 60 SO 100 120 140
Fig 20. Opportune II. Haul 119 response to snag. Skipper de-
clutches winch, then reverses engine
seen to remain high the engine was reversed and the
ship turned towards the net in order to free it. In the
second case, fig 21, the skipper decided to tow on, at
slightly reduced power until the ropes pulled clear, as
can be seen from the rapid reduction in load.
Fishing trials— trawler: The performance characteristics
of this vessel, when towing Trawl B in 100 fm (180 m)
arc shown in fig 22. The power versus speed curve for
this condition is shown in fig 23. Figures 24 and 25
show a typical fishing sequence.
DISCUSSION AND OBSERVATIONS
On free running trials
The speed power curves for both vessels show the
characteristically steep slope near maximum speed and
indicate that marked fuel economy could be achieved by
reducing cruising power whenever possible. For example,
continuous operation of the Opportune II at } knot less
than her maximum would reduce the fuel consumption
when running free by about 20 per cent. Undoubtedly
there is a psychological aspect in desiring maximum
Tim* - sec
Fig 21. Opportune II. Haul till (towing) response to snag. Skipper
reduces power slightly , continues towing
100,
370
PfOp»l!»( r|
Fig 22 Rosebloom. Fishing trials 12th July. 1965. Towing power
characteristic. Haul H7
95
speed and there must be occasions when the last J knot
will be a considerable advantage but a detailed study of
the pattern of fishing over a year should show if and
when this expensive speed is justified. This applies even
more to the Rosebloom, with a more powerful engine for
trawling, where the highest J knot costs 24 per cent of the
fuel consumption.
Both propellers appear to be slightly mismatched with
respect to the engines installed. On the Opportune II the
propeller pitch is slightly low in that the engine does not
develop its full rated power until its revolutions are 4 per
cent above the nominal maximum. On the Kosebloom,
the propeller pitch is slightly coarse since the engine is
on limits 11 percent below the maximum nominal rpm
at about 92 per cent maximum rated power. Again a
detailed study will indicate the economic significance of
these findings.
haul, in first and second gears, but when the net begins
to close and higher gears are engaged the power is
significantly higher with the larger catch, and the warp
loads do not decrease as they do when the catch is small.
20 hp was recorded with a catch of 5,000 Ib (2,300 kg)
and this could presumably be higher with much larger
catches which are not unknown. This table also shows
that the depth has little effect on warp loads and power
requirements during the haul.
These and the other records show that the mean loads
are little affected by variations in the type of bottom,
sand, mud, stones etc.
9
: 35
? «•
o
a
S
«- 1S
.. 400
(bJl
E
^ 100
150
130
(<*:>
r
0 2 * 6 • 0 10 A 00 2
hm* Hr Mm
10 20 30 40 SO
Ships Speed - Knots
Fig 23. Rosebloom. Haul H7 towing power- speed characteristic
Table 6 shows the effect, on full power performance, of
the various weather conditions encountered during the
course of the trials. Even in quite moderate weather
conditions, there is a speed loss of 0.5 knot, about 6 per
cent compared with the measured mile conditions. There
is an associated increase in thrust developed by about
16 per cent. These figures will vary considerably in
different combinations of wind force and direction, sea
state etc., and at this stage these results can only be
regarded as typical of the orders of magnitude involved.
On fishing trials results
Seine net vessel: The powers, efficiencies etc. quoted
(fig 18 and 19) may be regarded as typical for this class of
vessel. Worth noting is the very low apparent propulsive
efficiency during the tow, of the order of 0.15.
The results given in Table 7 show that size of catch has
little or no effect upon the warp loads for most of the
Shooting K
MomWorp.] __
-— — 1 Start of
__LHa^_
Hff 24. Rose bloom. Haul H2 Ship data
The weather throughout the trials varied from Beau-
fort No. 2 to 5 with ship motions up to :J_101' pitch and
4 20 roll. The fishing records show no significant
change in mean load or power due to weather alone.
However the oscillatory loads are affected by ship
motions and the results for record H6, summarized in
table 8, are typical. These results show that, as the net
is hauled in, the fluctuating load in the warps increases,
becoming increasingly affected by ship roll as the warps
shorten, and fluctuating warp tension can equal the mean
value (i.e. 0.5 tonsj_0.5 tons).
The records shown in fig 20 and 21 are typical of a
number of records taken when a snag was encountered.
These records and the skipper's reaction at the time show
that a snag is first noticed by the skipper primarily as a
difference in the appearance and feel of the warps. The
time between actually catching a snag and it becoming
apparent to the skipper was generally of the order of
30 sec, by which time the load in the snagged warp
[96]
can have risen three or four times the value previous to
the snag developing. One of the potential benefits of a
visual warp loadmeter is to give a much more rapid
warning of snags, particularly to less experienced skippers
than that of the Opportune II. Figures 20 and 21 also
illustrate the skipper's dilemma when faced with a snag.
To steam back (fig 20) may lead to 21 to 3 hr loss of
fishing time while to proceed (fig 21 f may cause con-
siderable gear damage, even complete loss. The visual
loadmeter should assist considerably in making the
correct decision in this situation.
(PJ.
(D)
"
" ©
6
(flD)
*-
(.B)
*
4
c
fc
3
£
. l\
J
(A) ,
30-
25
20
1
Fig 25. Roscbloom. Haul U2 lushing gear data
On trawler trials: The analysis of the various hauls,
taken in a variety of conditions, is still in hand. Some
comments can be made, however, on the set of readings
taken at various propeller rpm at 100 fm (180 m). In
these trials, which are summarized in fig 22 and 23, the
maximum shaft power developed was 273 hp at 365
rpm, probably because with this particular propeller
and this trawl the engine was on torque limits at that
power and speed. It is however doubtful if more power
could be of any advantage in these conditions, since even
with the 3.7 knots, 273 hp, 365 rpm, the skipper felt
that there was a tendency for this gear to lift which
tends to be confirmed by a reduction in warp tension
(fig 22).
Using this particular trawl, the benefits of having
installed the larger engine are seen in fig 23 where the
increase from 150 hp to 250 hp gives towing speed
increase from 2.J to 3J knots. The remaining 75 hp is not
usable when towing this gear in 100 fm (180 m) for the
reasons given above, but further study of the remaining
fishing records is necessary before this conclusion can be
applied generally.
Figures 24 and 25 show the powers, speeds, etc.
associated with shooting and hauling, and may be taken
as typical values but further analysis is in hand to show
the range of values involved.
D1RKCT INDICATING WARP LOADMETERS
During both sets of trials the warp load signals were
fed into the recorder for most of the time and only
switched to the dial instruments on a few occasions.
Both installations were left for assessment by the skippers
over a long period of commercial fishing. To date, it has
only been possible to obtain a progress report from the
Opportune II. The skipper reported favourably on the
system and, in particular, uses the meters (a) to deter-
mine whether or not to low the gear clear of a snag,
using 1.5 tons as a maximum safe load and, (b) to set
towing power and speed in a tideway. On coming to a
new ground the loadmcters are studied carefully to
obtain the usual 0.4 to 0.5 tons per side, until the skipper
is familiar with the run of the tide. The system is covered
by UK Provisional Patent Application.
FUTURE ACTION
The information summarized in this paper will be used
as basic data for a programme of design and development
work on the types of inshore vessel concerned. In
particular the following items are in hand or under
consideration:
(1) Development of a hydrostatic drive for seine net
winches. A drive of this type, not geared to the
propeller shaft, could show operational advantages
and the information obtained in these trials has
allowed an accurate specification to be drawn up
for load, power and characteristics.
(2) Design work on optimum propulsion machinery
characteristics for these vessels. With an accurate
knowledge of the requirements, it is possible to
make a comparative assessment of various types of
propellers, including CP propellers, to try to achieve
an optimum in terms of capital and running costs.
(3) Techno-economic studies in general, of which
item (2) is a major part.
(4) Consideration of possible improvement in hull
form.
Acknowledgment
Acknowledgment for their co-operation and help is due to the
following persons: Skipper G. Murray of Opportune //, Skipper
T. Ross of Roscbloom and their crews, and Skipper J. Patterson of
M.F. V. Altair.
[97]
Technical Survey of Traditional
Small Fishing Vessels
by N. Yokoyama, T. Tsuchiya, T. Kobayashi
and Y. Kanayama
Etude technique des pctits bateaux de peche traditionnels
Etude technique detaillee dcs petits bateaux dc peche japonais
utilises sur tout le littoral, s'attachant particulterement a leur
bonne tenue a la mer et a la simplicity de leur construction. L'emploi
de sections polygonalcs et dc bouchains vifs, outre qu'il simplific la
construction et reduit les travaux d'entreticn a tcrre, augmente
parfois aussi le rcndement des operations de peche.
An&lisis tecnico de las pequenas embarcaciones pesqueras tradi-
cionales
Son t6cnicamcnte estudiadas en stis detalles las pequenas embarca-
ciones que mas se vcn en todas las costas japoncsas, espccialmente
en lo que se refiere a sus favorables condiciones marineras y
sencilla construccion. Sus secciones poligonalcs y la robustez de su
doble arista no solo simplifican la construccion y reducen la
manutencion en tierra, sino que a veces favoreccn las opcraciones
dc la pesca.
MODEL resistance and structural testing of
traditional Japanese small fishing vessels were
presented at the Second FAO World Fishing
Boat Congress; now, investigations are introduced con-
cerning the sea-keeping performance in waves and
methods of construction. In the distant past the empirical
design provided safety and easy maintenance which was
essential to the fishermen, and they could reach the coast
of China crossing 500 miles of the East China Sea. Their
practicability is proved because, even today, nearly
400,000 fishing vessels smaller than 20 GT are, without
exception, of the Japanese traditional type (fig 1). Low
building and maintenance costs are advantages of this
type of fishing vessel, and therefore such a design may be
a good guide to those intending to set up small coastal
fisheries with limited capital in developing countries.
Fig L Traditional type Japanese fishing vessel
Beach landing can be easily performed with assistance
of housewives from neighbouring families even for craft
up to 50 ft (1 5.3 m). Boats of 30 ft (9.2 m) may be handled
alone by the aged or a married couple. Nowadays,
outboard motors or small diesel engines are utilized and
also the beach landing winch, formerly manually
operated, has been mechanized by drum and small motor.
The device for lifting the propeller and rudder and the
wide flat bottom of the keel keep the boat stable whilst
being slid on either sandy or pebble beaches. Wooden
slats are sometimes used as a slipway for heavier boats
larger than 30 ft (9.2 m) on soft sandy beaches (fig 2).
Fig 2. Stern detail of Japanese fishing vessel
Although the angular shape of the hull might appear
to give bad sea-keeping properties the empirical design
methods have reasonably avoided the dangerous reso-
nant conditions better than the conventional round-
bilge type when subjected to tests in waves. The longi-
tudinal distribution of section shape and area controls
the value of the longitudinal GM and the inertia co-
efficient, including the entrained water mass, and gives a
;98]
moderate longitudinal motion with the encountering
wave, even in the worst synchronized conditions at low
speeds. The angular shape of the hull and the deep
rudder tend to damp the motion in waves, and is one
of the most important factors in producing favourable
seakindliness.
The same is true of the safety margin in the syn-
chronous rolling conditions, and it is possible to main-
tain an ample righting potential in specific weather
conditions by good design. The hard chine tends to
damp the roll in resonant conditions and, because of
the small transverse GM, there is little possibility of
resonance in short-crested waves just off-shore.
The reserve of buoyancy should be obtained by
providing sufficient freeboard to overcome the worst
conditions.
The long and narrow rudder compensates for the low
lateral resistance of the shallow keel, thus reducing the
tendency to transverse drift in cross seas and wind.
According to statistics, a large proportion of sea
casualties arc caused by incorrect steering and misuse
of engines. The safety margin should be high for all
circumstances and engine reliability is very important.
The various properties of good ship performance
mentioned above can be obtained comparatively easily
for round-bilge European vessels. But special care and
sound experience arc required to obtain these properties
and approach the ideal of good performance ior the
traditional Japanese type of boat.
In the design, certain longitudinal and transverse
members are deleted. This saves labour during construc-
tion but, as all loads must be carried by the shell plating,
good techniques arc required for constructing the hull
skin. Many types of soft wood may be used, according
to availability; and with good maintenance, especially
of the seams of shell plates and bottom knees, an average
boat's life should exceed 20 years.
The price obviously varies according to cost of
materials and labour. Recently, the local labour cost
variation has become small, but material costs vary
immensely depending on the type and quality of the
wood, and it has become difficult to obtain timber of
large dimensions with natural curvature. The hull prices,
from statistical data of 1963, Ministry of Agriculture
and Forestry, are shown in table 1.
The total number of fishing boats less than 20 GT in
1963 was 391,545, of which only 179,409 were mecha-
nized. The mean tonnage of the unpowered boat was
0.81 GT and that of the powered 1.79 GT. The mean
engine power was 7.88 hp. The general trend between
1953 and 1963 may be seen from fig 3, which shows an
03.-io3rll.3
XIO ''
.16 ' 06
1953 54 55 56 57 58 59 60 61 62 63
• Number of unpowered boots
• Gross tonnoge of unpowered boat!
Number of powered boots
Gross tonnage of powered boats
-f •••— 0 Horse power of engines
Fig .?. Statistical data of Japanese falling boats under 20 GT
increase in powered vessels of 64 per cent and a decrease
in unpowered of 32 per cent.
RESISTANCE AND PROPULSIVE
CHARACTERISTICS
Resistance characteristics
The Japanese traditional chine boat can be designed
to give the same resistance characteristics in calm water
as European round-bilged vessels. Some test results of
thiee Japanese and three European boats are compared
in fig 4; the frictional resistance was derived from the
Schoenherr line. The small Japanese traditional boat
M-7, 26 ft (7.9 m) for general fishing, has excellent
results up to Fronde Number, Fn = 0.40 (6.4 knots),
whereas the M-8, 36 ft (1 1.0 m) pole-fishing boat is good
up to Fn = 0.35 (6.3 knots)
M-57, 52 ft (15.9 m) purse seiner (fig 2) has a higher
resistance over its entire speed range, even below
Fn = 0.30 (6.8 knots). The fish hold occupies a large part
of the boat and the low and flat bottom is necessary for
daily launching at surf side.
M-ll, 72 ft (22.0 m) trawler, and M-13, 61 ft (18.7 m)
purse seiner, have a round and full hull form and their
practical speed should be lower than Fn = 0.30 (about
8 knots). M-61, 47 ft (14.35 m) trawler, has fine lines
(Cp = 0.582) and shows an excellent performance over all
the speed range.
TABLE 1 . Cost of hull of traditional Japanese fishing vessels
3 GT 5 GT 10 GT
Quality of Materials £ ($) £ ($) £ ($)
High 480 (1 ,340) 875 (2,450) 1 ,750 (4,900)
Low 275 (770) 500(1,400) 1,150(3,220)
20 GT
£ ($)
4,100(11,500)
2,500 (7,000)
Note: Hard wood Quercus glandulifera, zelkova, camphor
Medium —Cherry, Japanese cedar
Soft wood — Pine, Japanese Judas
GT 0.55 LBD in metric unit (19.4 LBD in ft unit)
The hull price includes the complete vessel and gear, except for the electrical equipment.
[99]
0.020
0.4 o£ ot 10 12 1.4
Fig 4. Comparison of residual resistance coefficient between Japanese and European types
should be decided considering chine and sectional area
curve. For small boats the hydrodynamic flow velocity
is so high that the flow along the hull may separate from
the angular edge and the effect of volume may become
much higher than the eddy-making resistance caused by
the polygonal section-shape.
-0.1
07 O8 09™ LO I.I 1.2 13
Fiff 5. M-7 self propulsion test results
Generally the trim and draft affect the resistance of the
chine form, especially in the lower speed range, Fn = 0.25,
whereas at higher speeds above Fn = 0.30 the longitudinal
volume distribution has more effect on the resistance
of both types, chine form and round bottom form, than
the sectional shape. This may be proved by the results of
M-57 (chine, Cp = 0.7 1 0) and M- 1 3 (rounded, Cp ** 0.68 1 ).
In the initial design stage, therefore, the trim of the draft
10 v
0.1
0.2
1.0
CX4 VA/5C
\2 V//T
Fig 6. M-57 variation of wake fraction and thrust deduction
coefficient due to propeller position
r inn
8
for jibSm ship
6 ! (knols)
V tor 81m ship
12 V//T
06 08 1.0
Fff* 7 . Comparison of pitching amplitude between Japanese ami European type*
Calm water propulsive characteristics
In spite of the good resistance characteristics, the dis-
advantage of the Japanese boat lies in the low propulsive
characteristics. These are difficult to improve because
stern construction is not easy to simplify further than the
existing transom. The propulsive factors of M-7, 26 ft
(7.9 m) are given for tests with a 2-m model (fig 5). The
wake fraction, wt is quite small and disadvantageous^
decreased from 0.1 to 0 or negative depending on the
increase in speed, Fn = 0.2 to 0.4. On the other hand the
relative rotative efficiency, f/, , of the propeller rises from
0.7 to 0.8 with the speed but is much lower when com-
pared with ordinary ships. The thrust deduction factor, t,
is rather small, possibly because of the suction effect at
the submerged transom but in the higher range from
Fn = 0.25 to 0.4, it rises up to the normal value of 0.2.
The hull efficiency results from w, and t, and so remains
in the order of 0.8 and the resultant propulsive coefficient
i/i,= Pe/Pd is between 0.3 to 0.4 depending on the speed.
Effect of propeller position
Since the stream flow line cannot follow around the an-
gular square stern, and the flat bottom gives low w value,
the Japanese traditional boats must have an excessive
thrust deduction.
When a propeller is put parallel to the flow, separated
from the transom edge, and its centre immersed at
least to its radius, the hull efficiency should become
100 per cent, but in practice the loss due to an increase
of the thrust deduction fraction t will always exceed the
small gain of wt. This presumption was made quanti-
tatively evident in tests in fair conditions, namely, with
the propellers raked at 7", 12 and 17 to the standard WL,
plus less immersion at 12 of rake, as illustrated in fig 6.
The result shows that L-12 deep immersion has the best
hull efficiency above 9 knots followed by L-12, L-17, L-7
respectively, where L-12 may be aflectcd by the influence
of the rake. The negative wake has been derived from the
potential flow along the hull surface and the deep im-
mersion of propeller gives a hull efficiency over 90 percent.
T« / le
Fig #. Comparison of pitching amplitude between Japanese
and European types
[101]
but a deeper draft at the stern is not advantageous
both to t and wt.
The propeller lift is a typical device of the Japanese
traditional boat, and the fishermen often use it when they
navigate in shallow water, run over fish nets, or land their
boat on a beach. A test was planned to clarify the effect
of the propeller position, relative to the stern profile, on
the factors of wt and t. There are optimum values for
the rake and the distance from the hull in the test, but in
practice the fishermen operate the elevator quite freely
according to the water depth.
Longitudinal motion in waves
Essential factors for the longitudinal motion arc natural
period of free pitching, length of maximum synchronous
wave, and damping characteristics at resonance. A boat
of long free period encounters the significant synchronous
wave in the low speed range, which will seldom happen.
M-7, 6.5 ft (1.98 m) chine model, had an experimental
natural period of 0.945 sec, and M-61, 5 ft (1.52 m)
rounded model corresponding to the 6.5 ft (1.98 m)
model, of 0.804 sec. Generally the strong damping of the
35-
30
o
Fig 9. Comparison of bow acceleration between Japanese
and European types
j:375x 1/275 _,__
I 125x1/225,. /
0875x1/17.5' -
20!
15 i
IOJ
234
Fig JO. Increase in still water SHP due to waves
6 7
V (knots)
motions makes the measurement of the period so
difficult that its accuracy might not be fully reliable.
Assuming Kyy = L/4, the free period is represented by
2 TcKy/v'gGM, where Ky includes the added mass of
water and depends on the form and speed, the value
GMj depends on the form of water plane and the height
of G. M-7 has a fine fore body and wide transom stern,
and the BM! for the model is 6.1 1 ft (1.85 m). M-61 is a
normal boat having BM,=7.61 ft (2.18 m). The added
mass of water will increase more for M-7 than for M-61
when the flow separates from the chine and transom at
high speed. These characteristics cause the difference in
the free period.
The wave length having maximum synchronous force
on the ship's motion is decided by the pitching force
distribution along the surface, which mainly depends on
the volume distribution. M-7 is excited by rather a short
wave, since the buoyancy is increased at the stern, and
the resonant speed for a short wave is low. The test with
M-7 and M-61 were not conducted at the maximum
synchronous conditions, but it can be seen from the
result (fig 7) that the resonant speed for M-7 is about
Fn =•().! and that of M-61 above Fn^0.25. Since the
usual running speed is around Fn-0.3, M-7 will be the
more comfortable in waves.
When a boat meets the synchronous condition, the
motion depends upon the danif 'ng effect of the hull form.
At a first glance, the flat chine form seems to have a
longer synchronous motion in the maximum exciting
condition, but the result in fig 8 is contrary to expecta-
tions, although further study should be made on this
subject, as well as the relationship between dynamical
exciting and damping.
M-7 has so fine a fore body and so full a stern that the
resultant motion of pitching and heaving may bring the
virtual centre of pitching rather aft. The combined effect
of acceleration of pitching and heaving at the bow is
smaller for M-7 than M-61 (fig 9). Such a result comes
from the phase difference between them, where the
heave of M-7 is in advance of its pitch, but on the other
hand the pitch of M-61 is only a little in advance of its
heave.
Power increase in waves
To maintain the same speed in waves as in calm water,
the power should be increased and the more violent the
motion the more power is required. Self-propulsion in
rough water tests were run with M-7 (fig 10) but the
M-61 model was too small to fit the dynamometer and
so the model was towed in the same waves. Table 2 is the
ratio of the increase of SHP to that of EHP, assuming
propulsive coefficients arc the same for both models.
The trend is similar to that of the pitching amplitude, and
M-7 is a little better than M-61 above Fn = 0.26.
TABU 2. ASHP/SHP of M-7// KHP/EHP of M-61
Wave F//-0.26 0.30 0.34 0.38
0.875 L 0.902 0.675 0.773 1.300
1.125L
1.3751.
0.986
0.880
0.705
0.735
0.697
0.772
0.925
0.870
ROLLING AND STABILITY
Rolling
It is very important to design fishing boats which do not
roll excessively during the iishing operation. In order to
damp the rolling, bilge keels are usually fitted to the
hull but most small Japanese fishing boats have hard
chines at the bilge instead. The effect of the chines
should be clarified by using Bertin's extinction co-
efficient N, for roll damping which is used in the example
below.
10x10"
I 2 345678 910 20
(J> (deg)
/*//,' //. N value* oj houts huviiiK typical hull form
Mark
A
B
C
D
E
F
TABLF 3. Principal dimensions of boats A to F (fig 11)
Lpp
ft
26.2
29.5
80.01
68.50
95.20
78.20
(m)
8.00
9.00
24.42
20.88
29.00
23.80
ft
6.77
6.56
18.05
14.40
17.70
17.65
(m)
2.06
2.00
5.50
4.40
5.40
5.39
ft
2.82
2.95
8.10
7.05
8.86
8.50
D
(m)
0.86
0.90
2,47
2.15
2.70
2.59
Length of hilge
keel
none
none
none
none
about jj Lpp (steel)
about V Lpp (wood)
Length of chine
through Lpp
about | Lpp
about i Lpp
none
none
none
103
(1) N coefficient: The values of extinction coefficient
measured for many actual boats operating under load
conditions are shown in fig 1 1 . Their principal dimensions
are shown in table 3. The lines plan of "A" marked in
fig 11 are shown in fig 23. Fig 1 1 shows clearly that the N
value of A is the largest, with the exception of E. This
indicates that the damping action of the hull form having
hard chines throughout its length is greater than those
having partial or no chines. The damping action of A is
rather comparable with that of E which has sharp-edged
bilge keels made of steel. The actual effect of these N
values is shown as follows:
(2) Comparison with round-bottom boats: When a
boat rolls synchronously on a regular beam swell having
the maximum wave slope vm (degree), the maximum
rolling angle is calculated by:
0m ^ ^ Kyvm/2N (degree) (1)
where y is effective wave slope coeflicient.
2, 3 A 5,6 7 8 9 10
HR 12. Relation of synchronous rolling angle <^m, maximum
wave slope rln ami extinction coefficient N
If y value is assumed 0.70, $m values are calculated by
(1) and shown in fig 12 as the function of vm and N. If
vm = 5.0" is assumed, the synchronous rolling angle of
boat A which has hard chine throughout its length is 0m
(boat A)416.5 in fig 12 by using its N0 J0.5. 4-0.020*
in fig 9. In the same waves, the synchronous rolling angle
of boat D which is round-bottom hull form without
bilge keel </>m (boal D)>30' is found by using its
N0. so- ===0.006 (assumed). The reason for comparing
A with D is that most of the Japanese wooden round-
bottom boats do not have large effective bilge keels
* 4- approximately equal to.
because of the fear that the watertightness of the shell
plank around such a keel might easily be broken by
accidents.
TABLE 4. Comparison of boats A and D
Boat
Maximum
circular velocity
Maximum circular
acceleration
A
D
2.0 ft/sec
>3.6 ft/sec
(61 cm/sec)
(>1 10 cm/sec)
4.2 fl/secu
> 7.6 ft/sec2
(128 cm/sec2)
(:> 230 cm/sec8)
Note: 1 . wave period, Tw: 3.0 sec (— Ts when synchronized)
wave length, A: 46 ft (14 m)
maximum wave slope, vm: 5.0
maximum wave height, Hw: 1.3 ft (39 cm)
HW/A: 1/36
2, Limit value of unbearable acceleration
by Kempf 1.97 ft/sec2 ( 60 cm/sec")
Inoue 3.93 ft/secu (120 cm/sec2)
Kawashima 6.55 ft/sec2 (200 cm/sec")
3. Maximum circular velocity at the deck edge
4 2 ^»'** j, (where 0mttx- radian)
Maximum circular acceleration at the deck edge
v 0 ^mux ITJ (where ^II1IIX- radian)
Under such rolling conditions, the circular maximum
velocity and acceleration at the deck edge of each boat
is shown in table 4. (Assuming the breadth B = 2.0 m and
free rolling period Ts-~3.0 sec). The difference in the
results are thought to be significant from the fishing
efficiency viewpoint in rough seas. In Japan, some pole-
fishing boats are designed empirically to make them as
close to the permissible lower limit of stability with lower
KG/D value and hard chined hull form. This is reason-
able because they have longer rolling period, T0 smaller
effective wave slope coefficient, y, and higher extinction
coefficient, N, and so have a tendency to roll more slowly
and to smaller angles.
In Japan, there is a small number of round-bottom
wooden fishing boats having wooden bilge keels, but
their N values arc much smaller than those that have
sharp-edged bilge keels made of steel (tig 11). This is
because the keel depth is rather small and the edge not
usually sharpened. On the other hand, the sharp-
edged chines of vee-shapcd boats are thought to be
quite effective to damp the rolling.
(3) Fishing platform: Most of the Japanese small
fishing boats have fishing platforms outside of both
deck edges, as shown in fig 22, 23 and 24. These parts_are
actually not watertight and therefore do not affect GZ
curves in a rough sea. They are known, however,
empirically to be quite useful in damping rolling,
although systematical analysis of this has not been
performed.
Stability
There is no basic criterion to judge the stability of small
fishing boats in rough seas and therefore, in order to
compare it, the theory of C value (Yamagata, 1959) now
being used in Japan for passenger ships has been used
for the small fishing boats.
[104]
Dw h««hng moment lew carried by steady wind
/''iff 13. I. \planatory diagram ofC coefficient
(1) Wind and waves: When boat A heels by (/>,, degrees
to the Ice side under steady beam wind, the boat rolls
around </>0, and rolls to the maximum rolling angle 0,
(fig 13) on the weather side under synehronous rolling.
If a gust blows suddenly from the same direction, the
boat rolls much further to the heeling angle </>., on the
lee side, where area K'GT =arca K'C'A as shown. The
heeling moment lever of the gust around Japan is nearly
1.5 times of the steady wind. Therefore, if area K'G'F -
a and K'C'A=b are measured on the diagram, and
b/a> 1, the boat is considered to be safe.
14, Comparison of (jZ curves of I'ee- uiul round-bottom
boat
If the stability of a vee-shaped boat is compared with
that of a round-bottom boat having the same GZ curve,
the former is safer, as N value of the vee-shaped boat is
larger, and therefore </>,„ of the former is smaller.
(2) Strong wind or deck water: It is evident that the
boat having a larger GZ maximum value is safer when
the boat receives only a constant heeling moment caused
by, say, a strong wind or deck water. GZ curves are
compared between vee-shaped and round-bottom boats
of equal displacement (tig 14). In this comparison the
lattcr's bilge is amended into round form from the
former's lines drawing by using a radius— B, 4, and GM
and freeboard are accordingly modified. The comparison
indicates that the vee-shaped boat is less dangerous than
the round-bottom boat under steady heeling moment.
CONSTRUCTION
The construction methods employed in the building of
traditional Japanese boats are of great interest because
they are simple and cheap.
Building procedure
( 1 ) Keel plank: At first, the wide keel plank is set on the
keel block (lig 15). Sometimes it is built with two timbers,
depending on the size of the boat, one fore and another
aft.
(2) Aft keel (fig 15): The aft keel is fixed to the main
keel by a scarf joint with a wooden wedge and no nails
(lig 16)- The wedge is necessary for watertightness. If a
keel consists of timber, it is bent a little upward at this
point.
(3) Stem and transom (fig 17, 18): The stem is attached
to the fore end of the main keel mainly by a scarf joint
with a wooden wedge and no nails. The transom is
fitted to the aft end of the aft keel with nails.
(4) Bottom planks (fig 15): Built up and shaped bottom
planks which are developed on the ground, are lixed to the
keel plank, stem and transom by nails simultaneously and
symmetrically in order not to twist the hull. Then the
15. Keel and shell expansion
F105]
rise of floor is settled at several fixed positions and upper
edges of the bottom plank are smoothed symmetrically.
(5) Floor timber (fig 19): Built up and shaped floor
timbers are fixed in set positions to the bottom planks by
nails. Jf a transverse bulkhead is necessary, it is built up,
usually on the floor timber.
(6) Side planks (fig 15 and 19): Shaped side planks on
both sides are fixed to the bottom planks, stem and tran-
som, from midships towards both ends. Simultaneously
the distance of their upper edge is fixed by temporary
small tying timbers. The aft ends of shell planks arc
extended a little, then cut. The aft edge is covered by
small planks.
(7) Side frames (fig 19): Side frames, or sometimes
bilge brackets only, are fixed to shell planks at essential
points. Side frames are unnecessary near transverse
bulkheads.
Fig 16. Keel join f
Fig 17. Stem joint
Fig 18. Transom joint
.Pggk plonk
. ; \ —
Beam
FU /__..".
Side planJL
rn_ -Flflfir fjrnber 1
'::~~~
Bottom plo
plonk
i i
Fig 79. Two sections
_R_uddej thwart (plqn)
'-^^r-— ----Bottom olOTik
^_Af_te.r keel
Fig 20. Ruclc/er thwart ami "chirr
Toori- Kugi
Nui- Kugi
Fig 21. Japanese nails
(8) Beam and deck plank (fig 19): Beams are fixed
through side planks at their upper edge. The deck planks
are fixed to the beams or top of the transverse bulkheads.
(9) Rudder thwart (fig 20): A rudder thwart is fixed
on the upper side of the side planks just aft of the transom.
On the beam extended through the side planks, deck
planks are generally secured to increase the deck area,
and small bulwarks are constructed at both edges of the
deck beam.
Scantlings
There is an empirical scantling rule for Japanese wooden
boats which is based mainly on the keel length but it is
not suitable for use in other countries without con-
sidering the strength, rigidity, specific gravity, etc., of the
timber used.
Nail
The Japanese wooden boat is assembled by a special nail,
as shown in fig 21. The grain of the timber should be
considered when they are used. Round section bolts or
tacks are not generally used.
F1061
i. m rjri^c-jt^icr y :* -Is _ » - ~jr~*^ : m
LU_ :j ;.,-,>
^0& -^L^-T^LT*-- "* '" - '
1 t)
Fig 22, 20 GT mackerel boat
General description
As mentioned above, the Japanese wooden boal is built
on basic simple sectional shapes by utilizing the flexi-
bility of soft-wood planks, and therefore it does not
require skilled techniques in the design and building.
The construction is believed to have been developed
because of the abundance of large soft-wood planks in
Japan. Now there is a shortage and most of the bottom or
side planks arc made of built-up wide planks connected
side by side by nails. There are thousands of small
fishing boats of this construction in Japan, which seems
to prove that the construction is strong enough.
Modernized construction
Most of the small wooden boats over 30 ft (9.2 m) in
length arc now built by modernized Japanese construc-
tion (fig 22). They have complete frames in the engine
room and cant frames in the fore part. Some of their
propeller shafts cannot be lifted, and consequently the
construction method of the stern is similar to the
European.
The reason why larger wooden fishing boats are not
built by traditional Japanese construction methods has
been discussed, but there is no fixed opinion.
EXAMPLES OF ACTUAL BOATS
Group fishing boats
To raise the efficiency of fishing in some areas, the
group-fishing system has been introduced, consisting
of a 10- to 20-GT mothcrship and about ten 2- to 3-GT
small boats. The mothership guides the catcher boats
to the fishing grounds and, after fishing, gathers and
transports the catch to a suitable market (fig 23 and 24,
table 5). These boats have their base ports on islands
scattered in western Japan and can go to the fishing
grounds in one or two days. They arc built in small
shipyards by traditional and rather simple methods,
without any calculations, but the fishermen claim they
are very seaworthy even in rough seas of 32 to 38 ft/sec
(10 to 12 m/sec) wind velocity and about 7.6 ft (2.5 m)
maximum wave height and can also operate under
conditions of 26 to 32 ft/sec (8 to 10 m/scc) wind velocity
and about 3.7 ft (1.2 m) maximum wave height.
The mothership shown in fig 24 was designed by the
Fishing Boat Laboratory, the main objective being to
give it enough seaworthiness and stability.
Small mackerel pole-fishing boats
Drawings and principal dimensions of a typical Japanese
traditional boat are shown in fig 22 and in table 6. GM
[107]
Section at 4 ord. Section at 6 ord.
0.5
1.0
1.5 m
J
0 2
Fig 23. 24 ft pole fishing boat
[ 108]
4 ft
[109]
C E
Q
QLD0
— i --i-
.i
It
r 1101
TABLE 5. Principal dimensions and operating condition of group fishing boats
Small catcher boat
Mothership
GT
2.8
19.9
Lpp
ft Cm)
26.20
(8.00)
52.50
(16.00)
B
ft (m)
6.75
(2.06)
11.15
(3.40)
D
ft (m)
2.82
(0.86)
5.25
(1.60)
hp of main engine
17
120
Fish-hold capacity
ft3 (m3)
105.8
(3.0)
777
(22.0)
Number of crew
2
7
Operating condition
Displacement
ton
6.5
50.4
GM
ft (m)
0.85
(0.26)
1.41
(0.43)
Freeboard
ft (m)
0.99
(0.30)
1.05
(0.32)
GZmax
(deg)
32
35
ft (m)
0.46
(0.14)
0.82
(0.25)
C coefficient
1.6
2.0
Wind velocity
(m/scc)
39.40
(12)
62.30
(19)
Note: C coefficients ( — b/a) are calculated for the weather condition of steady wind velocity of
62.30 ft/sec (19 m/scc) or 39.40 ft/sec (12 m/scc).
value of these boats is rather small and results in a longer
rolling period and high fishing efficiency. The main
reasons for this are their vee-shapcd hull form, low KG,
narrow breadth and little exposed profile area on the
water line. The fish pond is built with Japanese traditional
type construction, the remainder by combined construc-
tion.
TABLE 6. Data of veo-shape mackerel pole-tishing boat
19.50
5S.70 (16.95) x 1 1.52 (3.52) ,-, 5.45 (1 .66)
GT
LxBxD ft (m)
hp of main engine 7!*
Fish-hold
capacity ft3 (m3) 797 (22.6)
Full load condition
Displacement ton 56.9
GM ft (m) 0.79(0.24)
Freeboard ft (m) 1.18(0.36)
KG/D 0.75
Coastal purse seiner Sakai-Maru (M-57)
The lines drawing of a coastal purse seiner is shown in
lig 25. It has a nearly square midship section and a
very wide flat keel, which makes it very convenient to
land or launch on a wide shallow beach. This hull form
can easily float at a small draft and also has enough
stability in shallow waves or water. The boat is launched
on the latticed wood (iig 1) by winding an anchored
wire with its own winch driven by its main engine
(about 60 hp), temporarily cooled by water in a drum
on the deck. On returning with a displacement of nearly
40 tons, it is wound up by a shore winch. The square
body is, therefore, indispensable to such operations and
some increase in resistance must be accepted (fig 4).
Nomenclature
lpp = length between perpendicular of a model
N = Berlin's extinction coefficient for roll damping
force
Tm = mean draft
$0 = angle of initial keel
0, = maximum rolling angle by synchronous wave
0a = maximum rolling angle by synchronous wave and
gust
0m = maximum rolling angle
yp = resultant propulsive coefficient ~ Pe/Pd
tin
Methode de Projet des Nouveaux
Types de Navires de Peche
by E. R. Gueroult
Lex chiffres auxquels on a fait reference dans cette communication sont incorpore dans la traduction
anglaise qui suit.
EN principc 1'Armateur (burn it a PArchitectc Naval
Ics elements de son projet, les dimensions princi-
palcs, les volumes dc cale, le rayon d'action, la
puissance, d'aprcs des resultats de bateaux precedents
prudemment extrapoles.
L'Architecte n'a pas a connaitre les donnees d'exploita-
tion et il se contente de traduire et d'inclure de manierc
ordonnee dans un ensemble, les demandes de I'Armaleur.
C'etait la marchc suivie dans Ic passe, et c'cst encore
parfois Ic cas. De moins en moins frequemment pour
les raisons suivantes:
• le nombrc de types nouveau de bateaux croit
constamment
• Tcxperience acquise avec les nouveaux types est
recente ct les fluctuations du marchc du poisson
imprevisiblcs
• pour chaquc type de bateau ou genre de pechc,
Ic nombre des paramelres est trcs eleve, D. J.
Doust n'en denombre pas moins de 58. L'analyse
de ces elements depasse les possibilites dc reso-
lution de la plupart
• le nombre important de facteurs irrationnels fait
considcrcr une etude systematique commc sans
objet et nous prive le plus souvcnt de la coopera-
tion des Armateurs
Cependant, les tres nombreux travaux deja existants
sur Tcconomie de 1'industrie de la peche ct la determina-
tion du navire optimum, prouvent 1'actualite du
probleme.
Le decalage general entre le technique ct Teconomique
existe egalement pour cettc industrie, il faut done essayer
de le r£duire.
Des etudes tellcs que celles de Doust et de Bogucki
qui traitcnt de tous les aspects du probleme pris dans
son entier, viscnt a fournir reformation qu'un ordinateur
electronique pourra transformer en resultat, suivant les
regies rigides de la logiquc arithmetique, plus rigoureuses
que celles de la pensee humaine.
11 est cependant necessaire, pour que les resultats soient
corrects, qu'un premier travail de degrossissage soit fait,
qui tienne compte des facteurs irrationnels en rcduisant
le plus possible le nombre des parametres et en les
simplifiant.
Cette premiere phase du travail est en realite la plus
importante car le rcstc en decoulc ct Ton ne pourra plus
compter que sur la verification a posteriori des resultats
obtenus, verification pour laquelle les machines clce-
troniques sont irrcmplagables.
La relation entrc Ic tonnage du navire et le genre et
le lieu dc peche, constituc la base dc depart qui doit
rcposer autant sur les facteurs economiqucs que sur
tons ceux que Ton ne pent mettrc en equation, tcls que:
variation de richesse des lieux de peche, rendemcnt du
travail humain, influence du climat, qualite de la detec-
tion, habiletc des capitaincs, politique dc prestige,
limitcs imposccs par les regies d'administration ou
syndicalcs, concurrence commerciale, etc.
Les calculs dc verification du rendement cconornique
montrent que la marge d'erreur possible sur le tonnage
est trcs faible.
L'Armatcur sail en general quelle peche il vcut
pratiquer, qucllcs sont ses possibilites financicres. II
doit etre renseignc rapidement sur cc qu'il pent attcndre
et c'cst a ce stade dc depart que la cooperation est la
plus fructucuse.
Fn plus des nations pour lesqucllcs la peche est une
vieillc industrie et qui en connaissent Ics donnees, il y a
celles, de plus en plus nombrcuses, qui vculcnt par
nccessite participcr a Texploitation des ressources dc la
mer ct qui ont besoin d'etre guidees. P.n fait, 1'ccart
entre les premieres et les sccondes n'est pas si grand
qu'il parait; on pcut considerer du point de vue dc la
composition des flottcs que tous les pays sont "en voic
de developpement". C'est done avant tout une methode
d'investigation qui est necessaire, qui puisse etrc appli-
qucc, avec les corrcctifs appropries, aux difTerents cas
particulars.
En regard de la complexite du probleme tel qifil se pose
actuellement, nous disposons de moyens rcccnts d'analyse
fournis par Ics statistiques de plus en plus nombrcuses,
bien exploiters par les specialistes de cette discipline, en
plus des travaux deja anciens de la recherche en con-
struction navale qui ont etc amplifies pendant Ics der-
nieres annces, en particulier pour la propulsion, la tenuc
a la mer, la securite.
Nous sommes beaucoup mieux armes que nous nc
Tetions a Tepoquc du dernier congres dc la FAO il y
a six ans.
L'objet principal de ce memoirc est de presenter une
112]
methode, dc souligner les objcctifs des futures rccherchcs
et de provoquer leur discussion. Nous nous sommes
eftbrccs de tirer parti des travaux parallclcs de nos
collegues et de notre proprc travail quotidien.
Pour dcfinir les possibilites d'applicalion des renscigne-
ments que nous donnons, admettons que la pcche soil
envisagee dans tout r ocean Atlantiquc Nord ct Sud.
Les dilTercnts graphiques donncs dans ce memoire n'ont
qif unc valeur d'exemplc pour certains types de navires
et malgre la presentation dcstiriee au projet, ne doivcnt
pas etre tcnus pour solution en valeur ahsolue d'un
problcme generalise.
Nous pensons qifil taut ctcndre la notion de projet a
celle de prevision basec sur les tendances que revelent
les statistiques, en particulier economiques.
Pour PArmateur qui pcnse en valeurs reel les et le
projeteur en quantites non dimcnsionnellcs, le dialogue
sera facilitc si Ton traitc line dimension a la Ibis et si Ton
ecarte les ibrmules a nombrcux lermes et les diagrainmes
ela bores.
DIMENSIONS ET CARACTERISTIQUES
PRINCIPALES
Volume de calc
Le volume dc calc est la donnee la plus imporlanle a
connaitre pour PArchitccte et doit etre reliee a LI fact cur
Ic plus important pour I'Arrnatcur, cclui qui enlraine sa
decision, la duree du voyage.
Quand il a tcnu compte dc Pt-loignemenl des lieux dc
peche, des moyenncs dc capture, du temps maximum dc
conservation s'il s'agit de poisson frais, du nombrc dc
voyages par an possibles pour assurer le repos de
Pequipage et Pentreticn du navirc, du temps limitc par
voyage que Ton peut demander a Pequipage, des rota-
tions necessaircs pour la vente, des possibilites de soutage
et d'approvisionnemcnt, il arrive a uric durcc d'abscncc
qui est dcterminante.
C'est avec intention que nous avons donnc unc simple
courbc reliant la duree au volume de cale (iig 1 ) a
Pcxclusion dc loute formule comprcnant Ic rayon
d'action, la vitcssc, Ic dcplaccmcnt, les moyennes de
capture, la densite d'arrimage.
II est evident que cette courbe qui est applicable dans
la partie basse aux navires de peche traiche avec une
duree d'une douzaine de jours, plus Ic voyage aller, et
dans la partie haute aux navires de peche congelee
pechant dans r Atlantiquc, doit etre completec par des
valeurs correspondant a d'autrcs pcches et d'autres
champs d'action.
Des courbes difierentes pour la pcchc salee, les
congelateurs avec ou sans filctage et traitement des
sous-produits, les thoniers ou navires qui conservent le
poisson dans Peau froide, doivent ctrc ctablies.
Nous voyons dans cettc relation de duree a volume
Pobjectif principal des recherches pour les annees a
venir.
Deplaccment
En nous basant sur un travail de normalisation des
navires dc peche entre 20 ct 90 metres, navires a deux
ponts et grand volume de cale a partir dc 40 metres,
peche par Parricrc, nous donnons la relation entrc
volume dc cale et dcplaccmcnt (Iig 2). Ces navires, par
les volumes, les proportions, le prix et les possibilites dc
production, n'ont plus grand chose de commit n avec
les chalutiers a un pont de peche par le cote tcls qu'ils
ont etc constants dans les derniercs 20 annees.
Pour le poisson congele, la surface ncccssaire au
traitement du poisson, la puissance auxiliaire de congela-
tion el la faiblc densite d'arrimage, la conception des
grands navires s'est trouvee completement modificc. II
ne semblc pas que la nccessitc des volumes dc calc
importants soil apparue dans les clcrnicrcs realisations.
Le rapport de volume de calc a dcplaccmcnt nc pcut sc
dcduirc que dc naxircs executes ou d'ctudes ires poussces
puisqu'il rccou vre Pcqualion des poids proprc ct dc
chargement.
Longueur
Lc prochain ct trcs imporlant pas dans Pclaboration
ilu projet est la determination dc la longueur en partant
du dcplaccmcnt.
Nous disposons pour ccl:» cPunc grande richessc dc
rcsultats d'ess»us dans les bassins dc carcncs ct depuis
l%3, avec Ic travail dc I). J. Doust, dc rcnscigncmcnts
ires surs ct faciles a uliliser pour tons les chalutiers de
moyen tonnage.
Pour les tonnages supcricurs des gros congelateurs el
navires usincs, les rcsultats cPcssais dc carcncs pour les
cart'o, rapidcs ou pelils paqucbots sont cgalcmcnt Ires
nombrcux.
La fig 3 donnc, avec unc representation non dimcn-
sionncllc, les resistances dc carcnc en fonction dc la
vitcsse relative et dc la finesse I./V* pour des carcncs de-
crial uticrs.
A Paidc dc ces courbes, la longueur, la vitesse et la
puissance pcuvcnl etre calculces en premiere approxi-
mation ct vcrificcs cnsuitc avec Ic travail original de
IX J. Doust (1%3), (apres determination des autrcs
dimensions), dans lequcl Pinflucncc scparcc dc 6 para-
metres importants de la geometric du navirc est fournic
ct aisemcnt cstimcc.
On pourra trcs rapidcment, pour plusieurs valeurs
dc finesse ct dc vitcssc, calculcr les puissances correspon-
danles et choisir les combinaisons les plus favorablcs.
La simplification vouluc dans la presentation de ces
relations ne dispense pas PArchitcctc d'excrccr scs
talents et connaissances en resistances des carcncs.
Largeur
Apres la longueur, le dernier slade du dimensionne-
mcnt consiste a fixer les dimensions transvcrsales. La
aussi, une grande quantite de recherches systematiques,
de statistiqucs, d'obscrvations a la mcr sont a notrc
porlee pour nous aider.
La largeur, Ic tirant d'eau et Ic franc-bord sont en
general choisis ou verifies par les calculs classiques pour
donncr unc stabilitc initiale sufTisante en charge.
Les nouvelles proportions pour salisfaire aux con-
ditions dc volume, de securitc ct dc tcnue a la mcr,
obligcnt a verifier la slabilite inclinee en charge et la
stabilitc initiale a legc.
La quasi impossibility; de degager un critere simple dc
113
stabilite, ct les regies Internationales de franc-bord pour
navires de charge inapplicables aux navires de peche,
ont etc jusqu'ici cause d'incertitude ou d'crreur. Les
reglements d'Administration tcls que les russes ou les
japonais, qui portent sur une verification apres realisation
ou etude completee, ne sont d'aucune aide pour le projet
et risqueraient d'avoir comme les regies de jauge, une
influence peu souhaitable sur 1'evolution du navire de
pcche.
C'est done des 1'avant projet que 1'Architecte doit
introduire les caracteristiques qui donneronl la stabilite
et les qualites nautiques requises.
Nous avons prepare la fig 4 pour la determination de
la largeur et du franc-bord pour une valeur associee du
bras de levier a 30° d'inclinaison.
La presentation en partie non dimensionnelle en
partant du deplacement, est celle qui convient le mieux
aux calculs initiaux. L'examen de ce graphique ne
manquera pas de soulever quelques commentaires.
(a) Nous avons indique les longueurs plutot que
des L/V* pour faciliter la lecture et illustrer le point
suivant.
fb) L'ecartement entre les droites de longueur est
irrcgulier et nous 1'avons maintenu tel volontaire-
ment. Si Ton prend comme base dc calcul une forme
que Ton fait varier systematiquement cntre les limites
de deplacement, on obtient un ecartemcnt regulier.
Si Ton prend comme reference des navires executes
tres semblables mais qui ne sont pas entre eux dans un
rapport exact de similitude, il n'cst plus possible dc les
mettre en courbcs ct la dispersion risque d'etre embarras-
sante pour le non spccialiste.
Nous attirons Tattention sur la necessite de comparer
les rcsultats de navires executes qui presentent des
variantes de formes et des differences dc hauteur de
centre de gravite.
Ce graphique doit etre etabli pour chaque type de
navire de peche differant radicalement du chalutier dc
moyen tonnage.
Franc-bord
En plus des valeurs relatives de F/V*, nous donnons une
courbe de franc-bord theorique en valeurs absolues qui
satisfait a la condition de stabilite inclinee suffisante et
qui peut £tre utile pour les navires a un pont (rig 5).
Pour les navires & deux ponts avcc coque intacte, il
est sans doute souhaitable de se departir de la r&gle de
franc-bord des navires dc charge a pont shelter et dans
ce cas le franc-bord indique peut egalement etre utile.
Nous avons represente une droite comme valeur
approchee, en fait c'est une courbe, surtout pour les
faibles longueurs.
Bras de levier de redressement
Les valeurs de GZ/V* seront sans doute trouvees
^levees par rapport aux bras de levier admis jusqu'a
present.
Les recentes etudes sur la stabilite inclinee sur vague
montrent que, lorsque la crete de la vague est au milieu du
navire, le bras de levier de redressement peut §tre reduit
de moitie, condition qui peut etre dangereuse par mer de
1'arriere.
De plus, une marge est utile pour tenir compte de
rimprecision des calculs dc bras de levier et de centre
de gravite.
En aucun cas GZ/V* ne devra etre considere comme
critfcre de stabilite. La grandeur du bras de levier de
redressement a 30° d'inclinaison n'a pas un grand
interet prise isolcmcnt, elle relie le franc-bord ct la
largeur dans la condition en pleine charge. Elle est
cependant facile & calculer pour un volume de deplace-
ment donne.
Centre de gravite
La fig 6 donne des valeurs moyennes de centre de
gravite a legc et en charge. Pour les navires a deux ponts
on doit tenir compte du relevemcnt du centre de gravite
avcc le temps, a mesure que les installations de traitement
de poisson prendront de Timportance. L'augmentation
de la hauteur du centre dc gravite avec le temps est bien
connue et nous en avions deja parlc au cours du Congres
de 1953.
Stabilite initiale
Pour verifier, des le projet, la stabilite initiale dans
plusieurs cas de chargement nous donnons la fig 7,
egalement non dimensionnelle. Elle est bas£e sur des
formes de chalutier dc 0,52 de S et fournit des valeurs
plutot elcvees de KM pour les bateaux uctucls.
Une verification de la stabilite a lege du navire
s'impose pour tous les navires a deux ponts, pour le
scjour au port, entre les periodes d'armemcnt pendant
lesquellcs la stabilite doit etre assuree sans lestage. La
necessite de couvrir les variations dc tirant d'euu assez
grandes entre les deux conditions legc ct en charge, nous
a conduit a des echellcs beaucoup plus ctcnducs de
B/V* que dans la fig 4 qui est tracee pour la seule
condition en charge.
Tirant d'eau
Le tirant d'eau se deduira de 1'cquation des poids et dc
la finesse admise pour la meilleure resistance de carene,
ct le creux du tirant d'cau et du franc-bord.
Puissance et vitesse
On pourra, arrive t\ ce point, calculer la puissance avec
suflisamment d'elements pour obtenir une precision
satisfaisante.
La puissance et la vitesse ont une importance telle
dans le calcul de rentabilite, qu'elles justifient un effort
special au cours du projet.
II est par exemple important de montrer tres tot a
1'Armateur les consequences d'une vitesse choisie a
priori tr&s elevee, et le gain que donne une vitesse
economique.
A defaut d'une documentation personnelle suffisante,
on trouvera dans les travaux de Doust les coefficients
propulsifs et les valeurs pratiques des corrections a
apporter pour Tetat de la mer.
VERIFICATION ET CHO1X FINAL
II est maintenant possible d'entreprendre le calcul de
verification de Teconomie du navire. Le prix du navire
[1141
est essentiel et doit etrc fourni a 1'Armateur, les autres
elements de depenses et recettes sont & tirer de sa compta-
bilite et des cours commerciaux publics.
Ce calcul pour unc serie de navires repondant a un
meme programme ou a des programmes voisins, fait
ressortir le tonnage et la vitesse optimum.
On pourra en cours d'etude verifier que la vitesse de
route ne depasse pas les limites raisonnablcs pour
I'economie d'exploitation, en appliquant la regie des
cargos dc ligne, par exemple: depenses de com-
bustible = ^ depenses totales. 11 n'y a pas de voic
royale pour cette derniere partic de 1'etude qui doit
entrainer la decision. II faut effectuer, pour chaquc
hypothese choisic, le calcul d'exploitation dans son
cntier. Le travail materiel pent etre facilite par un
programme ou modele economique destine a un ordina-
teur clectronique; le travail de L. K. Kupras (FAQ,
Rome 1964) est un bon exemple.
L'emploi des machines calculatriccs n'est toutefois
pas indispensable en premiere approximation.
Pour illustrer le choix du tonnage optimum, nous
donnons avec la fig 8 quelques excmples groupcs sur
unc base dc longueur, dimension la plus cvidente pour
TArmateur.
Ce groupement n'cst fait que pour cviter de multiplier
les graphiques, il ne faudrait pas cepcndant tirer une
conclusion quclconque de la valcur relative des types de
pcche. Ces travaux ont etc conduits pour different* pays
a differentcs epoques et se rapportent a des cas particu-
liers qui n"ont aucun lien entre eux.
CONCLUSION
Le projet doit etrc execute rapidcment sans negliger
aucun des aspects qui ont une influence sensible sur
Teconomic d'exploitation.
Au debut du projet, revaluation de la durcc d*absence
est faite par 1'Armateur.
Le volume necessairc en function dc la duree du
voyage engage la responsabilite partagce de TArmatcur
et de TArchitecte.
Les dimensions principals sont fixces par TArchitcctc,
leur influence sur Pcconomie du navirc devrait etre
examinee conjointement.
La decision finale motivce est prise par TArmateur.
Les travaux d'analyse devraicnt porter dans Ics pro-
chaines annees sur:
• la durce d 'absence
• la verification du rendement d'exploitation
1. 'importance de ccs travaux ne pcut etre sous-cstimec
et demande une cooperation, si possible cntre pays
voisins.
An point de croisement des etudes techniques et
economiques on s'elforcera de maintenir Tequilibrc cntre
la rigueur mathcmatique des moyens mecaniques d 'inves-
tigation et les cheminements de la pensee humainc.
115]
An Approach to the Design of
New Types of Fishing Vessels
by E. R. Gueroult
Le projet des nouveaux types de navires de pechc
L'autcur presente un schema de base, fond* sur une combinaison
de r&ultats analys6s statistiquement ct de 1'experience pratique.
Les plans doivent ctre etablis par titapes, en utilisant les para-
mitres approprids. Le projeteur, partant des factcurs 6conomiques,
commenccra par determiner le volume de cale, pour aborder
ensuite successivement depiacement, longueur, franc-bord, bras de
levier de redressement, centre de gravite, stabilite, tirant d'eau,
puissance, pour conclure par une nouvclle etude de la rentabilite,
afin de controler la validite du projet. En operanl ainsi pour une
serie de navires pouvant remplir les conditions voulues, on pourra
determiner le type optimal.
Mctodo para el diseno de nuevos tipos de embarcaciones dc pesca
Sc expone un modelo de disefio fundamental, basado en una
combinaci6n de resultados estadisticos analizados y de experiencia
luimana. HI disefio debe hacerse siguiendo el m6todo de la maxima
prudencia, mediante parametros de diseno pcrtinentes. Partiendo
de una consideration de los factores economicos para dccidir la
capacidad de la bodega, la cadena del diseno se ocupa sucesiva-
mente del desplazamiento, eslora, manga, obra muerta, brazo dc
palanca de adrizamiento, centre de gravedad, estabilidad, calado y,
por ultimo, se hacc un reanalisis de los beneficios economicos
previstos para comprobar el procedimiento del diseno. Eslo se
realizaria para una serie de disenos quc se podrian ajustar a las
necesidadcs economicas, obteniendo de este modo las mayores
ventajas de los disenos considerados.
THE owner generally supplies the naval architect
with the basic elements for the design of a ship:
principal dimensions, hold capacity, range of
operation, power etc., carefully extrapolated from
previous vessels.
In this case the architect requires no operational data
about the vessel; he merely interprets the wishes of the
owner and incorporates them into the design as a whole
in a carefully ordered manner.
This was the usual procedure in the past and although
still followed in certain cases, it is becoming less and less
frequent for the following reasons :
• The number of new types of craft is constantly
increasing
• Experience acquired with these new types of craft
is only recent and it is impossible to anticipate
fluctuations in the market for fish
• The number of parameters for each type of boat or
method of fishing is very high; Doust (1964) gave
not less than 58, and on analysing these one would
find that most of them could not possibly be
solved
• The number of irrational factors involved makes a
systematic study of the problem seem pointless and
very often leads to lack of co-operation on the part
of the owner.
However, the very considerable volume of work
already carried out on the economy of the fishing
industry and the determination of an optimum fishing
vessel prove that the problem is a topical one.
In this industry, too, it is difficult to equate the
technical with the economic aspect and efforts must be
made to bridge the gap between them.
Mathematical Logic
Doust (1964) and Bogucki (1964) in their studies dealing
with all aspects of the problem as a whole, aim to feed
information in to a computer and obtain results based on
strict mathematical logic rather than on the more fallible
workings of the human mind.
Nevertheless, if results are to be correct, one must
sketch out a rough programme which takes the irra-
tional factors into account, reducing the number of
parameters and simplifying them as far as possible.
This first phase of the work is in fact the most im-
portant one, since it provides a basis for all the rest, and
one can only rely on verification a posteriori of the results
obtained, for which electronic computers are indis-
pensable.
The relation between the tonnage of a vessel and the
type and place of fishing constitutes a basis for departure
which depends as much on economic factors as on all
other data which might be brought into play, such as:
variation in the potential of fishing grounds, human
output, climatic influences, quality of detection, skill of
the captain, prestige policies, restrictions imposed by
administrative or union rules, competition etc. . . .
Calculations of the economic returns of a fishing
vessel show that the possible margin of error on tonnage
is very small.
The owner generally knows what kind of fishing he
intends to practise and he knows his financial position.
He must be told what to expect at an early stage and it is
during this initial stage that co-operation can be the most
rewarding.
In addition to those nations for which fishing is an old-
established industry and which have all the facts at their
disposal, an increasing number of countries are finding it
[116]
necessary to exploit the resources of the sea and are in
need of guidance. The gap between the two groups is not
so great as would appear; as far as composition of the
fishing fleet is concerned they can all be considered as
"developing" nations. What one needs above all, then, is
a method of calculation that could be applied, with the
necessary corrections, to individual cases.
Modern Methods
To help sort out the complex problem one has new
methods of analysis furnished by an ever-increasing
amount of statistical data, fully exploited by specialists
in this field, plus all the research work on shipbuilding
done in the past and extended in recent years, particularly
with information on propulsion, stability and safety.
Naval architects are thus far better equipped than they
were at the last FAQ Boat Congress six years ago.
sion at a time and dispenses with long-winded formulae
and elaborate diagrams.
PRINCIPAL DIMENSIONS AND
CHARACTERISTICS
Hold capacity
The most important item of information for the architect
is the hold capacity; this must be related to the major
factor for the owner —the one which prompts his decision
— namely the duration of the voyage.
Taking into account the distance of the fishing
grounds from the home port, the average haul, the
maximum keeping time, if the owner is marketing fresh
fish, the number of trips which can be made in one
year allowing for the crew to rest and for ship's main-
tenance, the maximum length of time the crew can be
h'ig 1. Relation between hold capacity ami duration of a fishing trip
The main purpose of this paper is to present an ap-
proach, to underline the objectives that should be sought
after in future research work and to invite discussion on
these. Naval architects have tried to make use of results
of parallel work by their colleagues and of the fruits of
their own day-to-day labours.
To define the possibilities of application of the data
given here, it is assumed that the owner envisages
fishing in the whole of the Atlantic, both North and
South. The various graphs included in this paper only
show examples for certain types of vessel, and although
intended for design purposes, they must not be considered
as absolute values to be applied in solving general
problems.
The concept of design should be extended to signify an
expectation of economic returns based on statistical data
and market trends.
For the owner who thinks in terms of real values and
the designer who thinks in non-dimensional quantities,
this talk will be made easier if one deals with one dimen-
expectcd to remain at sea, the necessary sales rotations,
supplies and storage possibilities, the owner arrives at a
period of absence that is determinant.
A simple curve has been drawn up here relating the
duration of the journey to the hold capacity (fig 1 ),
deliberately avoiding any formula involving radius of
action, speed, displacement, average hauls, and stowage
density.
The lower part of the curve is applicable to fresh-fish
vessels away for some twelve days, plus the outward
trip, and the upper part refers to refrigerated ships
fishing in the Atlantic; the curve must of course be
completed by other values for different types of fishing
and other fields of action.
Different curves must be drawn up for vessels pre-
paring salted fish, refrigerated ships filleting or storing
whole fish and processing plant for by-products, tuna
fishing vessels or boats which preserve the fish in cold
water.
This ratio between the duration of voyage and hold
117
3000 —
Fig 2. Ratio of hold capacity (inside insulation) and displacement of fishing vessels
capacity should be the main target for research work in two-deckers with a large hold capacity, of 130 ft (40 m)
years to come. and over, where fishing is done over the stern. These
vessels, by their volume, proportions, price and pro-
Displacement duction potential, no longer have very much in common
Fig 2 gives the ratio between hold capacity inside with the single-decked, side-fishing trawlers built during
insulation and displacement based on known designs of the last twenty years,
fishing craft of between 65 and 300 ft (20 and 90 m) and For frozen fish, the old concept of large boats has been
Fig 3. Relation between resistance and speed of trawlers (in the resistance coefficient, Rc, L is in metres, R in
kilograms, V in knots and A in m'A)
[118]
completely modified to allow for the necessary space for
processing the fish, auxiliary power for freezing and the
small stowage density. It does not appear that the need
for large capacity holds has been sufficiently taken into
account in the latest examples of these vessels.
The ratio of hold capacity to displacement can only be
calculated from vessels already built or after detailed and
thorough studies, since it involves the light ship weight
and the dead weight.
Length
The next major step in design is to determine the length
of the ship from the displacement.
There is a great wealth of figures available from model
tests, and since 1963 Doust's work has provided accurate,
easy to use information applicable to all medium-
tonnage trawlers.
For larger tonnage vessels, such as big refrigerated
factory ships, there are also available results of numerous
model tests on fast cargo boats, and small passenger
vessels.
Fig 3 shows a non-dimensional representation of
resistance of trawler hulls in terms of the relative speed
and the coefficient of fineness I./V^.
With the help of these curves, the length, speed and
power can be roughly calculated and then (once the
other dimensions have been determined) checked against
Doust's (1963) work, where the indmdual influence of
six important parameters in the geometry of the vessel
is given and can be easily assessed.
The corresponding power can very quickly be calcu-
lated for several values of fineness and speed and the
most favourable combinations chosen.
These ratios have intentionally been presented in a
simplified form but the naval architect will still have to
use his talents and know-how as far as resistance is
concerned.
Breadth
After the length, the last dimension to be determined is
the beam; here again there is a great deal of systematic
research information, statistics, and results of observa-
tions at sea, to help us.
The breadth, draught and freeboard are generally
chosen and checked by means of traditional methods of
calculation to give sufficient initial stability when the
vessel is loaded.
To meet the requirements of volume, safely and stab-
ility, with the new proportions, statical stability in the
loaded condition and initial stability in the light condition
must be checked.
Hitherto there has always been some measure of un-
certainty and error because of the near-impossibility of
laying down a simple standard for stability and because
international freeboard rules governing cargo boats are
not applicable to fishing vessels.
Government rules such as are applied by the Russians
and the Japanese, prescribing verification after the ship
has been built or the design completed, are of little help
in designing, and like the tonnage regulations, are liable
to have an undesirable effect on the development of
fishing craft.
Consequently, the architect must incorporate into the
preliminary design the necessary features to give the
vessel the required stability and seaworthiness.
Fig 4 relates breadth and freeboard for a given value
of the righting lever at 30 degree heel.
This partly non-dimensional representation, worked
out on the basis of displacement, is the most suitable
method of making the initial calculations; the graph will
no doubt give rise to some comment.
(a) to facilitate reading the graph and to illustrate
the following point, lengths are shown rather than
values of L/V-X
(b) the spacing between the lines of length is irregular
OJJ 0*4 O.t5 O.M 0.07 OM O.it 1.00 1,01 I.Ot 1.03 144 1.0S I Of 1.07 l.Ot
Fig 4. Relation between freeboard and breadth for a given value of righting lever at 30 degrees heel
[119]
but it has been purposely left so. Instead, as the
basis for calculation, a form that can be made to
vary systematically between the limits of displace-
ment is taken, in order to obtain regular spacing.
F faired values of L/V1/^ are shown.
If consideration is given to ships built on similar lines,
but which do not have an exact ratio of similarity to
each other, it is no longer possible to draw up curves for
them; the values would be so scattered that non-
specialists would become highly confused.
Stress should be placed on the need to compare results
of vessels with varying forms and differing heights of
centres of gravity.
A similar graph must be drawn for every type of fishing
vessel that is radically different from the medium-
tonnage trawler.
Freeboard
In addition to the relative values of F/V^, a theoretical
freeboard curve in absolute values is shown which will
Under no circumstances should GZ/V^ be considered
as a criterion for stability.
Centre of gravity
Fig 6 shows average values for the centre of gravity in
light and loaded conditions. For two-deckers, it must be
borne in mind that the centre of gravity will gradually
rise as more fish processing plant is installed. This
alteration in the centre of gravity is a well-known
phenomenon.
Initial stability
Fig 7, also non-dimensional, enables the initial stability
under different loading conditions to be verified at
design stage. It is based on trawler forms of 0.52 block
coefficient and gives conservative KM values for present-
day boats.
All two-deckers must be checked for stability in the
light condition for the time spent in port between fishing
trips when stability must be maintained without ballast.
Fig 5. Relation between length and freeboard which gives positive stability
give a positive moment of statical stability and could be
useful for single-decked vessels (fig 5).
For two-deckers with intact hull, it is undoubtedly
wise to deviate from the freeboard rules governing cargo
boats with shelter decks and in this case the freeboard
shown may prove useful.
A straight line is shown as an approximate value; but
this is in fact a curve, especially for the smaller lengths.
Righting lever
The values of GZ/V^» will no doubt be found somewhat
high as compared with the normally accepted values of
the righting lever.
Recent studies on statical stability of ships in waves
show that when the crest of the wave is in the centre of
the ship, the ship's righting lever may be reduced by
half, which could be dangerous in a following sea.
Moreover, it is useful to have a margin to allow for
lack of accuracy in calculation of the righting lever and
the centre of gravity.
Draught
The draught will be calculated from the equation of
weights and the fineness coefficient giving the best
resistance; the moulded depth is to be calculated from
the draught and freeboard.
Power and speed
At this stage, there are sufficient factors to allow a
reasonably accurate calculation of the power. Power and
speed are so important in calculating the profitability of
a vessel that they justify a special effort throughout the
design stage.
For instance, at a very early stage the owner must be
shown the consequences of choosing a very high speed
a priori as contrasted with the advantages of choosing an
economic speed.
Doust's (1963) work gives coefficients of propulsion
and the practical values of corrections to be made
according to conditions at sea.
0 50
- Average values of centre of gravity in light ami loaded conditions
T/W3
Fig 7. KM estimations based on L, B and T
[121]
for vessels of smaller length, tested at NPL, had shown
the importance of afterbody shape in certain cases,
particularly the penalties in performance incurred with
high values of buttock slope. Before specifying the
parameters used to define afterbody shape we note that
as length between perpendiculars, commonly used in
large vessels, became a rather meaningless dimension of
length for the smaller vessels being considered, it was
decided to use the FAO definition of absolute length on
the floating waterline. This definition of length therefore
includes that portion of the vessel incorporating the
stern and avoids making separate distinctions between
cruiser, transom and unorthodox sterns, although
obviously artificial overhangs were faired out and an
"equivalent" length determined. To cater for differences
in afterbody shape then, two additional angles were
evaluated for each design, viz., the maximum angle of
run of any waterline up to and including the designed
floating waterline (iar") and the maximum buttock
slope (<XBS)-
The maximum angle of run is measured at a section
5 per cent of the waterline length forward of the after
end, whilst the maximum slope of the buttock line drawn
at 25 per cent of the full beam is measured relative to the
floating waterline. Although trim as such was not
considered to be an important variable, its influence
generally being reflected in a change of the remaining
form parameters, it was decided to investigate its effect
for these vessels as quite large variations in trim were
apparent in the data. Trim is defined as the change in
moulded draft at the forward and after ends of the
floating waterline, expressed as a fraction of the length
of the floating waterline. The following nine parameters
of the hull shape and dimensions were therefore used
to specify each vessel and evaluated up to the floating
waterline:
vz.,
See nomenclature.
As in the earlier NPL analyses, the resistance per-
formance criterion first proposed by Telfer (1933) was
used, viz., CR = R-L/AV2 and values of this criterion were
derived from the measured data for each model at
discrete values of speed-length ratio. The values of
speed-length ratio at which the data were scanned run
from K/V^ = 0.70 to K/>/L= 1.20, at intervals of F/\/L =
0.05, making eleven values in all. We therefore aim to
express the resistance criterion, CR, as a function of the
nine hull shape and dimension parameters, i.e.,
(1)
in which Vy will be estimated independently for each
speed-length ratio considered. In order to make valid
comparisons of performance and subsequent estimates
of ship resistance, all the model data were standardized
to a basic model length of 16 ft (4.877 m) using the 1957
1TTC formulation given by:
R
/- 2- 0-075 [log Jt,-
(2)
Originally it had been considered that the analysis might
be made retaining the Froude frictional coefficients,
since the bulk of the FAO data sheets had been calculated
on this basis. Subsequent re-examination however,
showed that it was necessary to refer back to the basic
model resistance-speed data in many cases, to achieve the
required accuracy of resistance evaluation. It was
therefore decided to use the basic model data throughout,
applying a relatively small correction to the model
results given by equation (2), in order to derive the
equivalent resistance of a model having a waterline
length of 16 ft (4.9 m). For subsequent extrapolation to
full size, the 1TTC or any alternative formulation can
therefore be applied.
The resistance data for these vessels is derived from
several sources, and inter-tank differences therefore
had to be eliminated as far as possible, so that the real
effects on resistance of parametric changes in hull shape
and dimensions could be estimated. The following
effects were considered likely to be present, and included
in the measured resistance data for each tank, and there-
fore should be quantitatively isolated, as far as possible,
from the real effects being studied.
• Blockage effects on resistance due to changes in
model size and tank dimensions
• Shallow water effects on resistance due to draft
of the models in relation to tank depths
• Differences in measured resistance due to stimu-
lated and unstimulated boundary-layer Hows
• Differences in measured resistance due to model
surface finish and different materials
• Differences in measured resistance due to dyna-
mometer accuracy
• Effects on resistance of appendages fitted to some
models
• Differences in measured resistance due to thermal
gradients in the tank water
• Personal errors of observers recording the re-
sistance and speed data
Blockage effects: The effects of tank blockage on
the measured resistances of the models included in the
analysis have been estimated using the type of correc-
tion proposed by Hughes (1961). This correction takes
the form of a speed correction 6rm which when added
to the speed of the model in the tank rm, gives the speed
of advance of the model in water of infinite breadth and
depth, having the same resistance as the model in the
tank. This correction is given by:
V,,,
gh
say.
(3)
Since the change in the model speed of advance <5rm is
proportional to the slope of the resistance-speed curve,
we have defined the slope of the (CR— K/vL) curve as
/? at any point, in which case the change in CR due to a
corresponding change in Vj\jL is given by:
where 0 is an auxiliary function to be determined from
the subsequent analysis. Since Hughes' work suggests that
[124]
<!> may be a simple linear function, we have included
blockage terms in our expression for ('„„ up to the
second order, without much risk of losing any important
effects, viz.,
It should be noted, therefore, that the appropriate
values of ar and ar+ j will be determined by the subsequent
statistical analysis, and it is only necessary to compute
the appropriate values of "B^ and "//" at each speed-
length ratio being considered. This procedure not only
reduces the magnitude of the already considerable
analysis involved, but also avoids the use of the rather
ill-defined values of ar, #,.+ , which would have to be
applied in the range of speed-length ratio with which we
are concerned for these vessels.
Shallow water effects: The exact solution, giving the
correction to model speed due to the influence of shallow
water on the resistance characteristics of a model being
towed at speed /•„, in a tank is given by Schuster (1955/56)
as:
/
-cothf
\< «'-.
qh
''
(6)
and this solution for (drm/vn,)h when // - -• gives zero
as one would expect. Hughes (1961) has given good
approximate values of the function [<>rm!rm]h for various
values of (r*/gh), so that the correction of each model
results to allow for these shallow wafer effects can be
readily obtained. Fortunately, this speed correction was
found by Tsuchiya to be negligibly small for the FAO
data and can therefore be ignored.
Turbulence stimulation of boundary-layer flow: In
the previous NPL analyses for the large deep-sea trawlers,
a correction allowing for laminar flow was applied to
measured resistance values of models tested without
fully-developed turbulent flow conditions. Jn this
manner, the whole of the data was standardized to
turbulent flow conditions, prior to subsequent analysis.
Such corrections were relatively small and only for a
few cases was the magnitude of the corrections up to
3 per cent of the measured resistance. In this case, for
the FAO data, not only are there considerably more
models involved, but the effects of turbulence stimulation
are less well defined, as these vessels are rather outside
the range of form parameters usually covered by studies
of boundary-layer flow conditions. It was therefore
decided to determine the effect of boundary-layer flow
stimulation statistically, by including a term in the regres-
sion equation for CK to estimate this effect. Since
approximately half of the data were applicable to turbulent
flow conditions and the other half unstimulated flow
conditions, there was sufficient coverage of the data
to make a first-order estimate of this effect at each
speed-length ratio considered.
Effects on resistance of hull appendages: A study of
the data showed that approximately 60 per cent of the
models were tested with wooden keel pieces, which could
be expected to produce an increase in resistance relative
to naked models built to the moulded lines and, excluding
the keel as an appendage. It was therefore necessary to
allow for the differences in measured resistance, relative
to a naked model, and an appropriate term was added
to the regression equation for fKii to estimate the
influence of the wooden keel piece independently, at
each speed-length ratio.
Effects of other factors on resistance: The effects on
resistance measurement of model surface finish, materials
used in their manufacture, dynamometry, thermal
gradients and possible local currents induced in the
tank water and errors of the personnel conducting the
experiments cannot be quantitatively assessed without
independent examination, and must be regarded in our
analysis as random errors. The question arises as to the
possible magnitude of their combined effects, in relation
to the order of accuracy required in making realistic
estimates of ship performance. An error of + I per cent in
speed estimation for the ship, considered to be sufficiently
realistic for most practical requirements, allows a
permissible variation in resistance estimation of between
± 5 per cent and -f 7 per cent in most cases with which we
will be concerned for fishing vessels (resistance varies
betwcci. i speed)1 and (speed)7). Our aim therefore is to
formulate an equation for CKtn in terms of the nine hull
parameters and the auxiliary functions expressing the
effects of blockage, wooden keels and turbulent flow
stimulation, such that the residual errors given by the
differences between measured and estimated values for
each model are of the order of 5-7 per cent or better,
in each case.
THE HULL FORM PARAMETERS
Prior to the commencement of the computational work,
it was necessary to study the dependency of the data
values of each form parameter on those of all the others.
In the ideal situation, each parameter will vary over
its full range for the whole range of values of each of the
other parameters and a rectangular distribution of data
points will be revealed by plotting each pair of parameters
on the usual Cartesian co-ordinates. Tig 1 36 show the
distributions of data points for all the models used in
this analysis, which are mainly derived from I European or
American tanks, and comprise a total of 308 designs. A
larger amount of data is available from Japanese and
other sources, but, since these cover an even wider range
of parameter values, it was decided to make a separate
study of these data at a later stage when further ex-
perience of the use of the results of this first analysis has
been obtained. For the present data it was found that all
Fvrni parameter
TAHI
/. \ tie me
.1 1
values
RaiW within which
iiuk'peiulem-e of
parameters is
applicahlc
L n
2.X to
5.X
3.1 lo
4.3
BT
1.5 to
4.0
2.0 to
3.2
Cm
0.44 lo
0.88
0.5 to
0.8
<r
0.48 to
0.73
0.55 to
0.65
l.c.h"lt( aft)
12.0 to
3.5
6.0 to
1.0
A a(.
6 to
40
1 5 to
34
i a/
22 to
80
30 to
60
«n.s-
10 to
57
16 to
34
trim ( i by stern)
0.04 to
• 0.13
- 0.04 to
-I 0.13
125
B/T
• 'V
• ••' .
...«>• i
• •. • • •«
• f • '/ • s '
. •
.*•'•"
• • •
\ V -.'t
,
.... _ _._|
1
I"""
L/B
j
fc /. Relation between B/TandL/B of models analysed in the
computer study
Fig 2. Relation between Cm and LIB of models analysed in the
computer study
Fig 3. Relation between Cp and LIB of models analysed in the
computer study
Fig 4. Relation between L/B and l.c.h.( %) of models analysed
in the computer study
10 20
I I 4 ol« (d««) I
._ I 2 _j
40 60
Fig 5. Relation between L/B and l(Xe(deff.) of models analysed
in the computer study
! L/B
...
__.
1
•
' ' . .
'
.
• .- : : . . A:
" !•'... *
* -•.. ..- '.
l!: '; S • -:' '"
• ' .': '
i
o(BS (deg)
20 30 40 SO 60
4 i
I I
' .."»-•. : • : *. ••"
40 so 60 70
Fig. 6. Relation between LIB and J a, (deg.) of models analysed
in the computer study
Fig 7. Relation between L/B and aBs(deg.) of models analysed Fig 8. Relation between L/B and trim of models analysed in
in the computer study the computer study
[126]
B/T
Cp
v
'"
t .'• '•.
v . .
L , •• "
•
1
.'• '
'•
1
i
B/T
Fig 9. Relation between BIT and Cm of models analysed in the
computer study
Fig 10. Relation between Cr and H/T of models analysed in the
computer study
. Relation between B/Tand l.c.b.( "„) of models analysed
in the computer study
Uc(deg) '
/•>>: 7,?. Relation between fill and Mdcg.) of models analysed
in the computer study
l alt (deg)
80 30 40 50 «0 70 80
Fig /.?. Relation between BIT and Mdeg.) of models analysed
in the computer study
40 10
Fig 14. Relation between B/Tand<XnS(dcff.) of models analysed
in the computer study
D/T i
75. Relation between B/T and trim of models analysed in
the computer study
Fig 16. Relation between CpandCm of models analysed in the
computer study
[127;
LCBW i
/•iff 17. Relation between Cm and l.c.b.( °0) of models analysed
in the computer study
20 30
Fig 18. Relation between Cm and \aLf(deg.) of models analysed
in the computer study
I dr(deg)
Fig 19. Relation between Cm and k<xT(deg.) of models analysed
in the computer study
20 JO
Fig 20. Relation between Cm and a nx(deg.) of models analysed
in the computer study
Toft-Tfwd_ltK]:
/•'iff 21. Relation between Cm and trim of models analysed in
the computer study
rig 22. Relation between Cr and /.rA(°n) of models analysed
in the computer study
• (dag)
Fig 23. Relation between Cv and \a.e(deg.) of models analysed
in the computer study
Cp
[ 128
Fig 24. Relation between CP and far(dcg.) of models analysed
in the computer study
Cp
BS (deg)
Fig 25. Relation between Cp and «ns(dcf>.) of models analysed
in the computer study
: Cp
I I
Fig 26. Relation between C,, and trim of models analysed in
the computer study
(deg)
\ ±<*r
' (
21' 15
Fig 27. Relation between \cnc(dcg.} and I.e. />.("„) oj models
analysed in the computer study
of MS (dog)
Fig 29. Relation between xDS(dcg.) and l.c.b.( °l() of models
analysed in the computer study
Lde(d«g)
?0 30
! ! ' ^dr(^
SO 60 70 80
Fig 2.8. Relation between \<jt,(dcfr.) and l.c.h.i ",,) of models
analysed in the computer study
i .
1"
Fig 30. Relation between trim and Lc.b.( "„) of models analysed
in the computer study
' ±ait . ' |
2 (deg) I : j
• " j o(BS(d«g),
ID ZO 3D 40 50 60
Fig 31. Relation between Mdeg.) and £ar(</<*p.) of models Fig 32. Relation between \*<(deg.) and »^(deg.) of models
analysed in the computer study analysed in the computer study
[129] E
"'•JV:V-' •".?"• ••'.-"
Fig 33. Relation between \oir(deR.) and trim of models analysed
in the computer study
rfBS
(deg)
I
..u .1
Hg 34. Relation between <y.its(deR .) and £0rrU/cv?.) of models
analysed in the computer study
I rtr
2 (deg)
Fig 3.5. Relation between ^onr(tleg.) and trim of models analysed
in the computer study
pairs of form parameters are reasonably independent of
each other, that is, a substantially rectangular distribu-
tion of data points is available for quite a wide range of
each parameter. The extreme values of each form
parameter, together with the ranges within which reason-
able independence of parameters is applicable are given
in table 1.
The main departure from a rectangular distribution is
in the plot of Cp against •£«£, in which there is an absence
of data for high values of Cp with small values of |o£.
By referring to fig 1-36, it can be seen that outside the
rectangular distribution of data points, there exists a
considerable number of vessels, often having form
parameters occurring in small groups. The importance of
these forms in making performance estimates for new
designs is referred to in the concluding remarks.
THE REGRESSION EQUATION FOR
RESISTANCE CRITERION €RH
Having established that the parameters used to define
each vessel were reasonably independent over a wide
range of parameter values, it is now required to formulate
equation (1) in such a manner that it conforms as closely
as possible to the known or likely behaviour of each
design parameter, and provides a satisfactory approxi-
mation to the data. Fortunately, some guidance was given
by the earlier NPL analysis in formulating the regression
equation for larger fishing vessels. The equation derived
in that analysis was of polynomial type, that is, it con-
sisted of a sum of individual terms, 30 in number, each
Fig 36. Relation between aIIN(deK.) and trim of models analysed
in the computer study
of which was a constant multiple of a power of a para-
meter or of a product of such powers. In this equation,
the parameters were cross-linked in pairs, though by no
means all possible pairs were cross-linked. Where a pair
of parameters, say X{ and X2< were cross-linked, the
following 9 terms appeared in the equation:
X2
Y2
A 2
Array type (i)
This array contains all the possible cross-products of
positive (or zero) powers of X\ and X2 when the power
of each parameter is limited to a maximum of 2. It may
be described as a square array of degree 2. Physically, the
inclusion of this array in the equation allows for each of
the two parameters to have an optimum value within its
practical range, an optimum, if it exists, which is allowed
to vary both in position and in sharpness with the value
of the other parameter. Only six parameters (L/B9 B/T,
Cm, Cr, l.c.b. and lo£) were included in this earlier
analysis and the pairs of parameters which were cross-
linked in the equation, in the way described (with one
minor variation which is not relevant to the present
discussion), were:
(CP,B/T),
and
(L/B.K).
[130]
The only other term in the equation was a simple linear
term in Cm.
The parameters 4«; and a,^ were introduced in the
subsequent NPL analysis of passenger-cargo vessels
1964 in order to take into account the shape of the after-
body. Each of them was cross-linked with Cr in the
regression equation for these vessels — the total number
of terms then being 44.
These 44 terms, together with live additional ones,
formed the starting point for building up the regression
equation for the present analysis. These extra live terms
were: a simple linear term for trim, the two terms
(#,/?) and (B{n)2- sec Section on Blockage Effects, a term
to take into account the first-order effect on resistance
of a wooden keel, and a term to take into account the
first-order effect on resistance of omitting turbulence
stimulators. In these early stages also, an attempt was
made to take into account the variation of this latter
effect with changes in Cr by including an appropriate
term in the regression equation, but the results obtained
were unsatisfactory and the attempt was abandoned.
With regard to trim, it may be repeated in passing that
the effect of varying the trim of any particular hull form
will be largely taken into account by the consequent
modification of the other parameters, such us /.r A, and
that the pure effect of trim, i.e. with all other parameters
fixed, is likely to be small. This was confirmed by the
analysis.
It was, of course, clear that this in.tiul equation of 4C>
terms would need considerable expansion before a
satisfactory lit to the data could be achieved: the ranges
of the parameters in the FAQ data are substantially
wider than in the NPL data and so terms that were
negligible in the latter case could become effective in the
former case. Nevertheless, it was helpful to have a
nucleus of terms, known to be important, round which
to build. Fortunately, the much larger number of models
available in the FAO data (over 300), made it possible
to contemplate such a major expansion. On the other
hand, the total number of possible combinations of 8 or 9
parameters up to, say, degree 4, is also very large, and so
it was still necessary to be very selective in deciding which
terms to add to the initial equation.
The general procedure adopted was to add to the
equation, a few at a time, new terms which were con-
sidered likely to be effective, to fit the extended equation
to the data, and then to assess the effectiveness of the new
terms by considering the improvement in the closeness
of fit. The purpose of the fitting procedure is to determine
the best values of the constant multiples occurring in the
equation, the best values, that is, in the sense that they
minimize the sum of squares of the differences between
the data values of CR and the values calculated from the
equation. (These differences are the "residuals".) Thus
the fitting procedure was carried out using the usual least-
squares criterion. With equations of the size we arc
considering, a great deal of computation is involved
and this was carried out on the ACE computer at NPL.
The improvement in the closeness of fit was assessed by
consideration of the residuals: if the addition of the new
terms to the equation resulted in a satisfactory reduction
in the sum of squares of the residuals, the new terms were
accepted as part of the final equation, otherwise they
were rejected.
In considering ways of expanding the regression
equation, there were three main directions we could
contemplate:
• Pairs of parameters could be cross-linked which
were not already cross-linked
• Products containing more than two parameters
could be introduced
• Pairs of parameters which were already cross-
linked could be taken to a higher power, e.g., the
square array of type (i) could be increased from
degree 2 to degree 3
Each of these three ways had to be considered. In the
first category, the parameter which stood out as re-
quiring further attention was the maximum area co-
efficient C,,r In the original NPL analysis, this parameter
was found to be relatively unimportant, but in the
present data Cm varies between 0.44 and 0.88, a very
wide range which represents very substantial differences
in the charactci of the hull forms. Consequently Cm
was introduced into the equation cross-linked with
both L B and #/7, and this was found to be beneficial.
In the second category, four major parameters, LIB,
Bj1\ Cp and Ja;., were considered and the four triple
products obtained by multiplying these parameters
together three at a time were introduced into the equation.
The result was unsatisfactory and so it was decided to
consider only terms containing not more than two
parameters.
At about this stage in the analysis, it was decided that,
instead of the basic square array of type (i), which limits
the power of each parameter separately, it would be more
logical to use an array which placed a limit on the com-
bined powers of the two parameters concerned. Conse-
quently, the regression equation was modified so that,
for each cross-linked pair of parameters, e.g.. A', and A'2,
the equation contained the following 10 terms: -
v2 v*
A I A |
1 A',
ATI A i A 2 A | A 2
X\ A', A';;
X
Array type (ii)
This array contains all the possible cross-products of
positive (or zero) powers of A', and X2 when the sum
of the powers of the two parameters is limited to a maxi-
mum of 3. It may therefore be described as a triangular
array of degree 3. In effect, it removes the term X\X\
from the square array of degree 2 and adds the two
terms A'-; and A^. Physically, as before, this array allows
for each of the two parameters to have an optimum
value which varies both in position and in sharpness
with the value of the other parameter, and at the same
time allows for some departure from the purely quadratic
form of the previous array.
At this point the equation was still some way from
giving a satisfactory Jit to the data, and so we undertook
an extensive investigation into possible additional terms
in categories above. As a result of this, the following
131]
new pairs of parameters, cross-linked to degree 3 were
added to the equation:
Also, the fourth degree terms of the following pairs of
parameters, already cross-linked to degree 3, were added
to the equation so that these pairs became cross-linked
to degree 4:
WT.CJ, (L/B.K), (C,,L/B).
The fourth degree terms of the following pairs were
similary tested, but rejected as unnecessary :
(L/£,CJ, (Cp,B/T), (C,,/.c.6.).
(C^K), (C,,K). (Cj.ci,).
These pairs were therefore kept in the equation cross-
linked to degree 3. Finally, three terms in the block
coefficient Cfl = (CpxCJ were tested but rejected,
namely: Cfl, C| and C^.
At this stage, the standard error (root mean square) of
the residuals for the data at V/\/L=l.Q was down to 0.74
corresponding to a basic scatter about the fitted expres-
sion of approximately ±3£ per cent of the average CR
value. Consequently, the equation was accepted as
satisfactory. The final form of the regression equation
contains 86 terms and is given in full in the Appendix.
All the above work of building up the regression equa-
tion was carried out on the data for V/\/L=l.Q. Once
the final form of equation was settled, it wasfitted to the
data for each of the other values of V/\/L for which
there was a sufficient number of models to yield a
satisfactory result, namely F/\/L=0.85 and then at
intervals of 0.05 up to 1.20. There was an insufficient
number of models at V/\/L=Q.7, 0.75 and 0.80.
During the work of building up the equation for
F/V^^l.O, a check was kept on models which per-
sistently gave high residuals. These could be genuine
departures from the regression equation, since a number
of larger residuals must be expected simply because of
random variations, but it was also possible that there was
some extraneous reason why the equation could not be
expected to fit a particular model, possibly because it
contained some unusual feature which was not taken into
account, and in this case its inclusion in the fitting
process might unnecessarily distort the fit. Consequently,
all the models with persistently high residuals were
referred back to FAO for investigation into the detailed
records, and where there was a satisfactory reason to
explain a poor result, the model was rejected from the
analysis. The rejected models included, for example,
cases where the bar keel had been carried up to the water-
line forward, and had not been tapered off, cases where
the running trim differed abnormally from the static trim,
so that the parameters used were not applicable to
running conditions, and cases which squatted an ab-
normal amount. There were also six models with bulbous
bows, which, as in the previous NPL work, were not
fitted satisfactorily by the equation. Then, of course,
there were the definite human errors which are bound to
occur in a collection of data of this magnitude. These
were picked out by their gross inconsistency with other
data, either with the same model at other speeds or with
other models having almost identical parameters. In all
32 models were rejected for one such reason or another.
The total number of models remaining after rejecting
these 32 is given for each value of V/\/L in table 2,
together with the root-mean-square of residuals.
TABLE 2
VI VI 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20
Number of models 184 222 245 249 245 240 229 196
Standard error 0.55 0.64 0.68 0.74 0.75 0.83 0.94 1.05
(root mean square)
of residuals of
ESTIMATION OF PERFORMANCE FOR
PARTICULAR HULL FORMS
Having determined the regression equations for C_KJI at a
series of_valucs of speed-length ratio from F/VL-0.85
to K/\/£=1.20, an auxiliary computer program was
prepared to evaluate resistance performance for any
required combination of hull form parameters. This
program was written for the KDF 9 Computer in Mathe-
matics Division, NPL, and requires as input data the
regression coefficients a{} a1 a2 . . . tfgs together with the
numerical specification of parameters [A^ X2 X% . . . X$]
and the individual terms such as X^X29 X^ X\X^ etc.,
of which the regression equation is composed. The pro-
gram can be used if required to evaluate other re-
gression equations of this type up to the ninth power in
13 variables, including the constant term 0().
In addition to evaluating the values of CKni for each
speed-length ratio, the program also determines the
values of CR at any required ship length (L) together with
the corresponding values of EHP using the ITTC formula-
tion, i.e.,
CKtr =(
-0.212847 —
-(
log 1. 2834 r.
3) 1
(7)
where S~ wetted hull surface area (ft2)
L= Length on waterline (ft)
A = ship displacement (moulded) in tons
(35 ft3/ton)
K=ship speed (knots)
and
EHP (using ITTC formulation) = C*ff"*'K • 09
32 !>. I Lt
To illustrate the use of the computer program and the
types of CRu curves which are obtained for particular
combinations of parameters, estimates of performance
have been made for seven forms covering a fair range of
each parameter, and are plotted against V/y/L in fig 37
to 43. In the case of Model Nos 40 and 48 (fig 37 and 38),
[132]
20
-i- L - r'
.275 ^60 325 ]5r~ wvgn
F/£ J7. A/o^>/ No. 40
L/B JB/T 1 Cm 1 Cp
3-6ZJ3-OO 072110596
""
250 31 01 16 s+O-0465
A
.275 .300
Fig 5-y. Model No. 48
Ifa
14
Fig 39. Model No. 199
O MEASURES
x CALCULATED
0-85 0-9
vos vic_
325
.275 300
Ffc 40. A/<wfr/ M. ;»J
estimates have been made for the case where no turbu-
lence stimulators were fitted, corresponding to the
actual test conditions for these models. Although the
measured results are less stable than those obtained with
turbulence stimulators fitted to the model, it can be seen
0 MEASURED
X CALCULATED
6-9 0'95 " VO VQ5 V1O MS 1-20 V/VC
275 300 3>5 IsST* VAflC
Fig 41. Model No. 193
C-ft5 0-9 0'9S i-C 1 05 1 1C 1 15 1-2C V/VL
Fig 42. Model No. 2021
v/^gc
that the estimates obtained using the regression equation
are in good agreement. It should also be noted that each
estimate of CR}h is independently derived and that even
so the general character of the resistance curve in terms
of speed-length ratio is reasonably well simulated.
Models 199 and 203 (figs 39 and 40), both having turbu-
lence stimulators fitted, again show good general agree-
ment between the measured and calculatedj-esistance-
specd curves, although the "hump" at y/\JL= 1.00 has
been somewhat suppressed in the case of Model 203.
Model 193 (fig 41) shows the largest dillerences between
the measured and calculated results, although the two
curves agree at K/>/L=1.00. There is some evidence to
suggest that the measured results below J-'/V/- = 1 .00,
which show a rising characteristic as speed reduces,
may be suspect due to over-stimulation, and the estimated
curve of Cjjlfi is certainly more in keeping with practical
experience. Models 2021 and 2004 (fig 42 and 43) are
derived from a separate Tank and are again reasonably
well fitted by the regression equation.
[133]
SOME EFFECTS ON RESISTANCE CRITERION
OF INDIVIDUAL PARAMETERS
The effects on resistance criterion CRi6 due to changes in
individual hull form parameters are rather complex and
vary both with speed-length ratio and the values of the
other parameters. In order to give some guidance to
designers of the smaller fishing vessels, fig 44 to 51 have
been prepared to show several effects of individual
parameters on resistance criterion for central values of
the remainder at I '/\ L= 1 .10. It was therefore considered
a basic form having the following hull form parameters
and discrete changes were made in each parameter.
The hull form parameters of the basic form are:
-2.0, la, -25.0, 4a;=45.0, 0^ = 25.0, trim = -fO.05].
(a) L 8 ratio The effect of length-beam ratio has been
studied between 3.1 to 4.2 at various values
of prismatic coefficient between Cr = 0.55
to C'p = 0.65, for fixed values of the re-
maining parameters of the basic form.
c* :t
EJ
v- -
V/V/L - MO
F/# 44. The effects of variations in L//i ratio from the standard
value of .f. 75 for various prismatic coefficients
Fig 44 shows that reduction in L/B ratio
down to a value of approximately 3.40 is
generally beneficial for all prismatic co-
efficients. Below values of C/; = 0.59 how-
ever there appears to be some penalty in
resistance criterion for L/B ratios less than
3.40.
(b) BIT ratio The effect of beam-draft ratio for fixed
values of the remaining parameters has
been studied for B/T ratios between 2.0
and 3.2 and for Cp values between 0.55 to
0.65. Fig 45 shows that increase in B/T ratio
always results in a penalty in resistance
criterion for all values of prismatic co-
efficient. With the exception of Cp = 0.65,
which is on the edge of the rectangular
range of data points included in the analysis,
the penalty change in resistance criterion
due to changes in B/T ratio is generally the
same for all prismatic coefficient*.
/•/# 4.5. 77i«? effects of variations in R/T ratio from the standard
value of 2.75 for various prismatic coefficients
(OCm
The effects of variations in maximum area
coefficient Cm have been calculated over
the range C,,,==0.50 to Cm^0.80. This large
range covers a wide variety of hull forms
from the yacht-shaped hulls with tine
midship sections up to the fuller-sectioned
and generally larger fishing vessels around
100 ft in length. As can be seen from fig 46
(d)C,
50 c-ss c^; c 65 " "r-"£ .:•"•« ~ oso
Cm
V/^L - MO
rt. 77?r effects of variations in maximum section area
coefficient from the standard value of Cm 0.65
there is a penalty in resistance criterion as
Cm is reduced and this penalty is the same
for all values of prismatic coefficient
within the range Cr = 0.55 to Cr = 0.65.
The slope of the CRlti-Cm curve, however,
is rather less for values of Cm in the region
of C,,, = 0.75 to C,,, = 0.80, suggesting that
for these fuller sections the benefits of
further increase in maximum section area
are not so great.
The effects on resistance criterion of
changes in prismatic coefficient from the
standard value of Cp=0.61 have been
calculated for fixed values of the remaining
parameters of the basic form. It can be
seen from fig 47 that a prismatic coefficient
of 0.61 is about the worst value for the basic
form and that both higher and lower
values are advantageous.
[134]
375 275 C-b5i
r5 O 45 ; 25-Ct-COS
C,XEC
BASIC
/Vtf 47. 7//r effects of variations in prismatic coefficient from
the standard value of C,, O.fi I
(e) /.
,T
The effects on resistance criterion of
changes in position of the longitudinal
centre of buoyancy can be seen in fig 48 for
values of prismatic coefficient between
Cr=-0.55 to Cr- 0.65. It can be seen that
there is generally a benefit in locating the
position of the l.c.h. up to 6.0 per cent aft
of amidships, although for Cr values in
excess of 0.63 the optimum position
appears to be at or near amidships.
49. The effects of variations in half-angle
the floating waleiline frtnn the stantlanl value
or various prismatic coefficients
35
\f entrance of
of Aorj. ?5
importance in relation to the remaining
form parameters (see fig 50). Tor the
ranges of hull form parameters with which
we are concerned in our analysis, therefore,
it is generally permissible in design work to
allow the run angles of the form to increase
if required to make the buttock angles less
steep.
t
,-4-, ^^..4
Cp O
Cr O
* f-v* oft^
L *• i 1 o
/•7^ 4«V. The effects of variations in position of longitudinal
rentrc of huoyancy from the standard value of - 2.0 per cent
for various prismatic coefficients
(f ) ia(. The effects on resistance criterion of changes
in the half-angle of entrance of the load
waterline are very marked as can be seen
in fig 49. Generally speaking, the advantages
of adopting a low value of Ao£ are apparent
at all values of prismatic coeflicient,
although for Cp values of 0.55 and 0.57 it
appears that almost equally good per-
formance can be obtained for values of
±o£ between 30" and 35' as for values of
ic£ between 15 and 20 . Both of these
ranges of $3.',, arc better than the standard
value of 25° for the basic form.
(g) i«r The effects on resistance criterion of
variations in half-angle of run from the
standard value of X = 45 f°r various
prismatic coefficients, are of secondary
I &--:_:-— — _^7" " -J". :_~
/-/X7 5^. 7'/w effects of variations in half-angle of run from
the standard value of Aar 45 for various prismatic coeffi-
cients
(h) y.lts The effects on resistance criterion of
variations in buttock slope are generally
significant for all values of prismatic
coefficient and show a benefit in CRn> as
buttock slope is reduced down to 15° (the
lower limit of the data). These effects can
be seen in fig 51.
(i) trim The effect on resistance criterion of changes
in trim from the design value of : 0.05 are
not significant.
It is emphasized that the independent changes in
LfB, BIT, Cm and Cn discussed above will all affect
displacement. In practice, if changes are investigated
which keep length and displacement constant, a change in
[135]
ft ASIC
FOAM
3-75 2-75 0*5
FIXED
0-61
LCB%
-Z-0 25-0
45-0
FIXED
25-0
TRIM
+0-05
25 r
2U
L. -.-> __ J£^-* *"
t
KEY :-
A
Cp 0-55
15
10
STANDARD
VALUE '
i i J
D
I
Cp 0-59
Cp 0-61
Cp 0-63
Cp 0-65
1 1
5 20 25 30
V/VT MO
35
Fig .57. The effects of variations in buttock slope from
the standard value of <x.'JBS — 25 ' for various prismatic
coefficients
any one of these four parameters will necessitate ap-
propriate changes in one or more of the other three,
and the several resulting effects on CR will counteract or
reinforce one another, thus modifying the above con-
clusions in particular cases.
CONCLUSION
Similar trends showing the influence of hull form para-
meters at all speed-length ratios between K/v^-0.85 to
K/vL=1.20 can be derived from the computer pro-
gram. As we have demonstrated however, the effects
on resistance criterion arc quite complex. Estimates for
individual vessels and suggestions for improvement in
performance should therefore be made using the com-
puter program as a design tool.
This analysis covers a wide range of hull form para-
meters and fishing vessel types. As more data sheets for
new vessels are included in the FAO store of information
however, it should be possible to extend the coverage of
the present analysis even further. The process is therefore
seen as one of continuous appraisal, modification and
improvement in the design of fishing vessels.
The expressions in the regression equations derived
from this analysis can be explored in order to seek
combinations of hull form parameters which will give
improved performance. This exploration can be carried
out either by some form of systematic evaluation of the
expressions or by using one of the methods of mathe-
matical optimization which are currently available. Four
different sets of hull form parameters have been derived
by these methods and forms having these parameters
have been designed by FAO and Chalmers Technical
University, Goteborg, and models have been tested at NPL
and Chalmers. This work is presented on page 1 39.
As already noted, there are a considerable number of
vessels included in the present analysis having hull form
parameters outside the ranges given in table 1. For new
vessels which have hull form parameters in these regions
of existing data, satisfactory estimates of performance can
usually be made using the regression equation given in
the Appendix.
Acknowledgments
This paper is published by permission of the Controller of Her
Britannic Majesty's Stationery Office. The work described has been
carried out as part of the research programme of the National
Physical Laboratory, and this paper is published by permission of
the Acting Director of the Laboratory.
The authors also wish to acknowledge the following sources of
data presented to FAO:
Hydraulic Laboratory, Division of Mechanical Engineering,
National Research Council, Ottawa, Canada
Bass in cTEssais de Carenes, Paris
Institut fur Schiffsbau, Berlin-Karlshorst
Hamburgische Schiflfbau Versuchsanstalt, Hamburg, Germany
Vcrsuchsanslalt fur Wasserbau und Schiffsbau, Berlin
Vasca Nazionale per le Experience di Architeltura Navale, Rome
Fishing Boat Laboratory, Fisheries Agency, Tokyo
Ned. Schcepsbouwkundig Proefstation, Wageningen, The Nether-
lands
Skipsmodelltanken, Norges Tekniske Hogskolc, Trondheim,
Norway
Canal de Experiencias Hidrodinamicas, Madrid, Spain
Kungl. Tekniska Hogskolan, Stockholm, Sweden
Swedish State Shipbuilding Experimental Tank, Goteborg,
Sweden
William Denny Bros. Ltd. (Experimental Tank), Dumbarton,
Scotland, UK.
National Physical Laboratory, Teddington, Middlesex, UK.
Davidson Tank, Stevens Institute of Technology, Hoboken,
New Jersey, USA
The Naval Tank, Department of Naval Architecture and Marine
Engineering, University of Michigan, Ann Arbor, USA
David W. Taylor Model Basin, Navy Department, Washington,
DC, USA
Webb Towing Tank, Webb Institute of Naval Architecture,
Glen Cove, Long Island, New York
Most of the results published by FAO (Traung, 1955, 1959), are
derived from the foregoing research establishments. In addition,
the authors wish to acknowledge that some of the data are derived
from tank tests carried out independently by FAO, also by Mr.
Traung with the aid of grants from the Mrs. Martina Lundgrens
Foundation for Maritime Research at the Swedish State Ship-
building Experimental Tank, from the Sea Fisheries Association
of the Swedish West Coast and from the Icelandic Legation in
Stockholm. The considerable amount of programming and
numerical work entailed in the derivation of the regression equa-
tions described was carried out by Mrs. G. Peters, and the
computer program subsequently described to evaluate the regression
equations was written by Mr. G. T. Anthony, both of Mathematics
Division, NPL.
NOMENCLATURE
length on the floating waterline. Obvious
long stems, etc., are faired out and the
appropriate length determined. In some
cases L is determined from drawings, as
length between perpendiculars is sometimes
the only length given in reports
B beam, maximum, usually at the midlength
of dimension /„, measured at the floating
waterline WL
Taft draft at the aft end of L to an elongation
of the centre bottom line of a steel hull
(excluding a possible bar keel) or to the
elongated rabbet line of a straight keel of a
wood hull
T draft moulded at £L
Tfwt draft at the fore end of L to an elongation
of the centre bottom line of a steel hull
(excluding a possible bar keel) or to the
elongated rabbet line of a straight keel of a
wood hull
[136]
V
v
v
LIB
BjT
maximum immersed section area (the area
of the vertical transverse underwater section
of the model which has the greatest section
area)
volume of displacement of the model up to
the floating waterline (ft3)
metric displacement volume of the under-
water body of the vessel, including keel
and appendages to waterline WL in (m)3
displacement of ship in salt water, floating
at waterline WL, based on 35 ft3 of salt
water per ton, corresponding to a specific
gravity of 1.026 in long tons of 2,240 Ib
0,016kg)
wetted area of the underwater body of the
model to waterline WL. This includes the
wetted surface of all appendages in the
appendage list at the top of the FAQ data
sheets, excluding struts and open shafts
ship speed in knots
ship speed in ft/sec
coefficient of kinematic viscosity; assumed
to be 1.2285xK)-5 for model at 59'T in
fresh water and 1.316x10— s for ship at
59°F(15°C) in salt water
Reynolds number = (?'/,/ v)
Froude number
speed-length ratio
maximum area coefficient evaluated to
waterline WL(Cm = AJBT)
prismatic coefficient based on the maximum
section area and the moulded displacement
including stern (Cp = 35&/L.Am)
block coefficient: the volume of the under-
water body of the ship divided by the
volume of a rectangular block having
dimensions L, #, T as the ship
length-beam ratio
beam-draft ratio
position of the longitudinal centre of
R
RL
buoyancy in relation to the midlength of the
dimension L, expressed as a percentage of
the length L
-f indicates the position forward of \L
and
— indicates the position aft of it
the angle which the waterline WL makes
with the centreline of the model at the
stem. Normally this is the average angle for
the first i.ln of the length L, but when
measuring, care is taken to disregard
excessive rounding or hollowing near the
stem.
the maximum angle of run up to end in-
cluding the designed floating waterline WL.
This angle is measured at a section 5 per
cent of the waterline length forward of the
after end of L, except where this section cuts
the dcadwood, when the maximum water-
line slope at the intersection with the
forward end of the deadwood is taken,
the maximum buttock slope of the \ beam
buttock measured relative to the floating
waterline WL. This angle is evaluated
exclusive of the slope of the stern contour
in the case of vessels with transom sterns
ship resistance in Ib
—-—. resistance criterion proposed by Teller
"AK2
Rf
vm
/
h
g
resistance criterion when /.= 16 ft (4.9 m)
three-dimensional frictional resistance com-
ponent given by ITTC Formulation
relative density or specific gravity
model speed of advance in ft/sec
length of model in ft corresponding to ship
length L
breadth of model in ft corresponding to
ship breadth B or breadth of water in
tank (Formula 3)
depth of water in Tank (ft)
acceleration due to gravity (ft/sec2)
137
APPENDIX
Final Regression Equation
«3*3 + a4AT4 + tf5X5 + <**** + ^7*7 + tf 8
+ a ,8* + a i
X 2
* X5 + «53 Xl X5 4- «54 JV4 *?
4 ^6 + ^5b ^4 ^6 +^57 ^4 ^fo
^5K J^T4 A^7 -f « 5,, A- A'7 -h « oo X* X2
-«66
^6 + ^68 %2 X6
+ a70X3 X
X2 Ar
X $ X #-+- a$o X $ X #-\- ci#i A 5 A8
where X, = L/B
= <*»<>
= trim
O, if there is no wooden keel
.. _
( l "~ \ , if there is a wooden keel
__ JO, if turbulence stimulators are fitlecl
( 2 ~~ \1 , if turbulence stimulators are not fitted
c/0, «j,^2,. . ,,c/85 are constants determined by the least-squares fitting, a different
set for each value of Vf\/L.
[138]
New Possibilities for Improvement in the
Design of Fishing Vessels
/. O. Traung, D. J. Doust, J. G. Hayes
Nonvelles possibility d "amelioration du dcssin des bateaux
11 a 6te decide, pour controlcr le programme FAO/NPL (National
Physical Laboratory) pour le calcul sur ordinatcur de la resistance
des balcaux de peche, de construirc ct de soumcttrc a dcs essais dcs
modeles de 4 bateaux de peche, mesurant 40, 55, 70 et 85 picds
(12,2, 16,8, 21,4 el 26 m) a la flottaison. Aprcs une etude du deplace-
tncnt, de la largeur et du tirani d'eau des batiinents decetic categoric,
il a etc decide de proecdcr aux essais de ces 4 bateaux avoc dcs
rapports longueur/deplacement de 4, 4,25, 4,5 et 4,75 respective-
men t.
La communication decrit le procede d'optimisation ainsi que le
travail de dcssin proprement dit. Les lignes de coque ont etc concucs
eu egard a Ferhcacite propulsive el a la tonne a la mcr. Les resultais
des essais ties modeles de 40 (12,2 m), 55 (16,8 m), 7() (21,4 m)
et 85 pieds (26 m) soul compares aux predictions fournies par
1'ordinatcur. On montre comment les resultats peuveni oire
appliques pour di versos longueurs a la flottaison, a..tremcnt dii a
des navires do deplacements et de largeurs difiorenis.
Ftant donne que la hauteur du Centre de firavite depend dcs
materiaux de construction utilises, des machines, dcs superstruc-
tures, etc., il est rccommande de n 'employe1 -.p'avec discernemcnl
les lignes proposers. La stabilite des 4 na\iies a cgalcnienl fait
Tobjet d'une etude sur oidinateur, dont la cointnunication presentc
certaines conclusions d'ordre general.
Nuevas posihilidadcs de funeionamiento del diseNo de las emlmrca-
ciones de pesea
Con objelo de comprobar el programs do calculadoras 1-AO/NPL
para estimar la resistencia do las emharcaciones de pesca, se
deeidio disenar y probar modclos do cuatro barcos pesqueros de
40, 55. 70 y K5 pies (12,2, 16,8. 21,4 y 26 m) en la linea de flotation.
Se hi/o un estudio del desplazamiento, manga y calado de las
cmhareaciones de pesca do esta scrie y se deeidio probarlas con
valores do despla/amicnto do oslora de 4, 4,25, 4,5 y 4,75 respect i-
vamente.
Se describe t-1 prncodimiento de optimization asi como la
composition real de los pianos de formas. Los pianos se desarro-
llaron considor.inJn la dicacia do la propulsion y lascoiuiicionesdel
oleajc. Los rcsultudos modelo cle los barcos do 40, 55, 70 y 85 pies
se comparan con las prcdiccionos do las calculadoras. Sc mucstra
como sc pueden emplear lt>s rosultados para las dilerentes longitudes
de la linea de agua, es decir, tamahos de barcos do despla/amicnto
y manias <!iferenles.
Como la altnra del ccntro de gravedad dcpondora de las clases del
material tie construccion, maquinaria, superestructuras, etc., se
advierio el peligro do usar sin discnminacion alguna los pianos
propucstos. 1'ainbicMi sc pucdo invcstigar la estahilidad de los 4
barcoh con aynda de una calculadora y sc dan algunas conclusiones
genorales de esta investigation.
FISHING boat hull shape must vary greatly due to
different local conditions, iishing methods, con-
struction material, engine weights, distance to the
fishing grounds and other factors.
It is obviously impossible to design a few standard
hulls which arc suitable for all conditions.
FAQ has in the past collected and published results of
model tests and full-scale trials in an attempt to indicate
the trend in the factors which influence resistance,
powering and sea-keeping qualities.
With the recently completed statistical analysis of
fishing vessel resistance data (Doust, Hayes, Tsuchiya,
page 123), it will be possible when time and funds permit
to draw important conclusions on how to find optimum
hull shape when designing new fishing boat types.
The statistical analysis is also intended to be used for
estimating the performance of an existing design so
it can be investigated whether there is room for
improvement.
In order to test the validity of the analysis it was
agreed to design and lest four models of varying sizes
and it was also considered desirable if these could be
made as good hydrodynamically as possible to indicate
ways in which small and medium sized fishing boats
could be improved.
SKLKCTION OF MAIN DIMENSIONS FOR
FOUR TYPICAL FISHING VESSELS
1 1 is an unfortunate fact that very few performance
figures exist for small and medium si/ed Iishing vessels.
Even for those built to professionally made drawings,
there seems to be no time or interest after the com-
pletion of the vessel to determine precisely displacement,
stability, loading conditions and power requirements.
Although FAO has collected whatever information was
available over the years, its data are scanty and incom-
plete in this respect.
In fig 1 displacement against length has been plotted
for a number of fishing vessels from 30 to 100 ft (9 to
30 m). The displacement represents the completed vessel
ready to go to sea but without water, fuel, ice and
fishing gear (lightship condition).
It was found that while there is considerable spread
between figures, the displacement curves conform
generally as the cube of the length, which confirms an
old impression that, when dealing with small Iishing
vessels, one could use the length-displacement ratio
(dyti = /v/V*) as a guide to the estimation of displacement
from length.
Fig 1 shows curves of length displacement ratios 4*
139
400
(tons)
20
40
60
80
Fig J. Displacement of completed fishing vessels ready to go to sea but without water, fuel, ice and fishing gear (light ship condition) plotted
against length. Curves for equal length/displacement ratio are alao drawn
4.25, 4.5 and 4.75 and generally the assumption might
be permitted that a ratio 4.5 represents the light con-
dition of most vessels and a ratio 4 a displacement about
43 per cent higher which could be considered as repre-
senting the loaded condition. However, construction
practices vary in various countries, as do the weight and
size of marine engines.
It is well known, the length-displacement ratio has a
large effect on ships' resistance. It was, therefore, found
to be practical to make the four models represent vessels
40, 55, 70 and 85ft (12.2, 16.8, 2 1.4 and 25 -9m) in length
and the displacement-length ratios 4, 4.25, 4.5 and 4.75
respectively. In this way the results could be expanded,
so that eventually, for any length between 40 and 85 ft
the resistance could be determined for boats having
length-displacement ratios between 4 and 4.75.
Simultaneously, the relationships between beam and
length and draft and beam were plotted, and it was
found that for the fishing vessels in question, the beam
varied from L/£=3 at 30 ft (9 m) to L/B=4 at 100 ft
(30 m). There was a variation of about ± 10 per cent
in the beams. The B\T varied approximately between
2.5 and 3 for investigated types. The L/B ratio of 3 to 4
is somewhat more restricted than is modern practice,
which is normally about 10 per cent higher.
OPTIMIZATION OF REGRESSION EQUATIONS
Doust, Hayes and Tsuchiya (page 124) have described the
derivation of regression equations of the form
, BIT, Cm, Cp, l.c.b.% l«;, ty, aB°s, trim],*
which enables the resistance performance of a particular
vessel to be estimated from its parameter values at each
of a series of speed-length ratios. With these equations,
* For nomenclature see page 136.
[140]
it is also possible to explore the effects of varying these
hull form parameters, with a view to minimizing CRl6
and so deducing new combinations of parameters giving
improved performance. These changes may be performed
for an existing design of current interest, restricted only
by basic design specifications or may provide the most
advantageous solution where alternatives exist. As in
previous work (Doust, 1962; Hayes, 1964), the case
is considered when ship speed, length and displacement
are specified,* i.e. [V, I, A] are given.
Hence we know V\\}L and ^ =
-
(35A)*
But
C..C.
so that the variations of these four parameters must be
restricted to satisfy this equality. Thus, for example, if
LIB, BIT and Cp are fixed, the value of Cm follows. The
variations must definitely also be restricted to the
parameter ranges of the original data used to derive the
regression equations.
Three ways were considered for exploring the effects of
changes in the values of the form parameters.
Evaluation over a mesh
This is the most direct method and consists of selecting,
say, five values of each parameter covering the range,
evaluating CR for all possible combinations of these sets
of live values, and examining the results to find a mini-
mum CR. This process, however, involves a very large
number of evaluations. Nearly 400,000 evaluations
would be needed if all the parameters were allowed to
vary in the above manner subject to it> being constant,
and, even if variations in \vLr and trim are ignored,
because the effects of these are negligible, over 15,000
evaluations would be required. In practice, therefore, it
would usually only be reasonable to take all possible
combinations for the most important parameters and
to vary the remainder singly about some arbitrary
standard. This might not always be satisfactory since
significant effects might be overlooked.
Systematic tabulation
The situation can be considerably improved, however,
by taking into account the precise form of the regression
equations and noting which pairs of parameters are
interrelated and which arc not. In fact, by this means,
from a few thousand evaluations, tables can be compiled
which allow all the parameters to be correctly taken into
account and which arc valid for all values of <&. As it
happens, the task is appreciably simplified in the case
of V/jL=l.l, since the terms relating l.c.h. (/0 and $<£
are small enough to be neglected initially. Thus, in this
case, it can be observed from the equations that the
effect of changing ^a* depends only on L/B, B/T and Cp,
so that ia° can be optimized for particular combinations
of these parameters independently of the others. Simi-
larly, the best values of l.c.h. % and a^ can be found for
particular combinations of the same three parameters,
* From the stability point of view also beam could be specified.
[HI]
independently of the rest. The effect of iC which
depends only on Cp, can be considered independently of
all parameters except Cp.
The general procedure is illustrated in table 1. Five
values are taken for L/B and five for B/T covering the
appropriate ranges, giving 25 possible combinations of
these two parameters. For each of these combinations, a
set of tables is drawn up, a particular example of which
is shown in table 1. For this purpose, the effects of £a°
and trim, which are small, were neglected though in
fact they add only a little to the complication. Initially
table l(a) is surveyed and for each value of Cp the best
value of CK and the corresponding value of Ja^ is
selected. Thus, for Cp = .575, i^ = 15 and the first
approximation to be best CR value, for this Cr, is 15.71.
This latter value corresponds to the arbitrary standard
values of the parameters not so far considered, which
will now be dealt with. Table l(b) shows the amount to
be added to CR when particular values of l.c.h. % and
a/^ are selected. In the column for ("^ = .575, the maxi-
mum reduction possible (greatest negative value) is
— 0.67, corresponding to an l.c.h. of —4 per cent and
a/is °f 20 degrees. The second approximation to the best
CR value is therefore 15.71 -0.67=: 15.04.
It now remains only to consider the effect of Cw; it
has been observed earlier, when L/B, B/T and Cp are
fixed with <M constant, the value of Cm follows. Table l(c)
gives the values of Cm corresponding to different values
of Cp and (M. Assuming 4.5 to be the value of $p of
current interest, it is found that for a Cp value of .575
that Cw = .758. By interpolation in table l(d) for this
value of Cm the appropriate addition to CR is obtained
and it is -| 0.1, giving a final value of 15.04 | 0.1 = 15.14
for CR. This corresponds to the following parameter
values:
L/B B/T Cm C, /.r.6.% K K «« trim
3.7 2.9 .758 .575 -4.0 15 45 20 0.03
This is the best set of values given these particular
values for L/B, B/T and C,,. A similar set can be selected
from table 1 for each value of Cr, and the best of these
gives the best set for these values of L/B and B/T. The
whole process is repeated for all the other combinations
of values of these two parameters and the best one of
these gives the final optimum.
Mathematical optimization
The problem of optimizing mathematical functions has
received a great deal of attention from numerical
analysts in recent years, and many methods, of varying
degrees of effectiveness, are now available (e.g. Fletcher
and Powell, 1963). Essentially, these methods start at an
arbitrary, or otherwise predetermined point (combination
of parameter values) and by computing function values
and sometimes derivatives in the neighbourhood of this
point, obtain a direction in which to proceed to a more
advantageous region. This process is repeated until no
further improvement is possible by small steps in any
direction.
This process has the advantage over the earlier one
in that an optimum can be more accurately pin-pointed
than is possible with the tabular values of the systematic
I
r— " •
"V
">-
'.J-
• --" T-:
I
lig 3. 40ft (12.2 m) optimized fishing vessel.
The lines were designed hv FAO and the
model tested by KPL
/if? 4. 55 ft ( 16.8 m) optimized fishing vessel.
The lines were designed by IAO and the
model tested bv NPL,
[145]
—it,
[146]
-*>'-•.«..
Fiff 5. 7Qft (21.4 m) optimized fishing vessel.
The lines were designed and the model tested
by NPL
/>> 5. *5// (26 m) optimized fishing vessel.
The lines were designed and the model tested
by Chalmers Technical University
9* ' 9V4 10
[147]
which required adjustment to accommodate the fine
angle of entrance and the longitudinal centre of buoyancy.
In doing this, great care was taken to ensure that the
sectional area curve was not too steep in the after body
as experience has already shown this requirement for
larger fishing vessels, although a somewhat steeper
curve had to be accepted. Care was also exercised in
avoiding too hard a shoulder on the waterline. Fig 7
shows the area curve for the 40-footer.
0! 2,54 & f, f B •)
Fig 7. Displacement curve for the 40-ft vessel
The stern aperture for all vessels is made so large
that it can accommodate a 300 rpm propeller able to
produce a maximum speed of about 1.2 Froude number
and produce full thrust at 100 per cent rpm while towing.
The power required for such towing is higher than
that required for steaming and is estimated at 60, 120,
350 and 500 hp respectively for the four designs.
MODEL TESTS
Models of the 40-, 55- and 70-footers were made to
scale— 1:6, 1:8 and 1:12 respectively — and tested
by the Ship Division of the National Physical Laboratory
in their No. 1 tank, whereas the model of the 85-footer
was made to scale 1 :7 and tested by the open-air model
testing facility of Chalmers Technical University,
Gothenburg, Sweden.
Fig 8 to 1 1 show the wave profile for various V/^/L for
the 40-, 55-, 70- and 85-ft models.
Table 3 gives the measured CR{6 values for the models.
The models were equipped with turbulence stimulating
studs and as the results include any parasitic drag,
results are also given for CRl6 with estimated resistance
for the turbulence stimulators subtracted. Fig 12 to 16
show these CRtt values compared with the original
data included in the statistical analysis, which were
plotted according to the second author's recommen-
dations.
In order to be able to compare individual designs with
best current practice, fig 17 has been prepared from the
FAO data sheets, such as fig 12 to 16. The FAO data
are derived from many hydrodynamic laboratories and
differing degrees of turbulence stimulation were appli-
cable to many of the models and it was necessary to
standardize all the measured results to constant physical
conditions before true comparisons of performance
could be made. It was decided, therefore, to standardize
all the FAO data to infinite depth and breadth of water
and to correct all model results to the fully turbulent
condition, using the appropriate values of Bl n and the
regression coefficients given by the equation in Appen-
dix 1 of Doust, Hayes and Tsuchiya (page 138).
A plotting of CRl6 against A16 was made for each of
the four speed-length ratios 0.90, 1.00, 1.10 and 1.20,
correcting each model result to infinite water, with
turbulence stimulators fitted, as already indicated. The
minimum envelope of CaJO-Ai6 was determined for
each of these speed-length ratios, whilst on the same
diagram were shown the CKJ8 values at speed-length
ratio =0.90 and 1.20 given by the 1957 ITTC formulation
for a value of ® = 6.0. It was of great interest to note that
for the best current design values, the amount of viscous
to total resistance at a representative design speed of,
say, speed-length ratio = 1.10 is approximately 53 per
cent for all values of @ between 3.75 and 5.00. As in the
earlier NPL analyses (Doust, 1962; Hayes, 1964) it can
be seen that forms having low values of <8) have generally
less resistance per ton of displacement (® = 3.75 to
4.0).
With the aid of such diagrams it is now possible to
derive the minimum CR|6 values over the practical range
of speed-length ratio 0.90 to 1.20 for infinite water and
with fully turbulent boundary layer flow, given by best
current practice. These values may be compared with
either measured or estimated values of CRl6 for new
designs and decisions taken regarding their quality of
performance. It should be noted, however, that in
general a hull form having good performance values at
one value of speed-length ratio will not necessarily
maintain all this advantage at other values of speed-
length ratio.
Fig 17 shows the results of the four models already
tested compared at V/^L—l.i for infinite water.
TABLE 3
Model test results expressed in
yjVZ
40 ft; ($
J) =4.0
55 ft; <S
$ - 4.25
70ft;(j
f) -4.5
85 ft; $
t - 4.75
1
2
1
2
1
2
1
2
0.85
13,23
12.43
14.35
13.55
12.30
11.50
14.08
13.28
0.90
13.55
12.35
14.55
13.35
12.94
11.74
14.17
12.97
0.95
13.84
12.48
14.96
13.60
13.51
12.15
14.64
13.28
1.00
14.08
12.69
15.17
13.78
14.29
12.90
15.18
13.79
1.05
14.10
12.61
15.58
14.09
14.91
13.42
15.72
14.23
1.10
14.73
13,16
15.97
14.40
15.51
13.94
16.28
14.71
1.15
16.51
14.86
17.17
15.52
16.77
15.12
16.71
15.06
1.20
19.66
19.08
19.96
19.38
18.98
18.40
18.00
17.42
Column 1 Cnie measured on model fitted with turbulence studs.
Column 2 Measured Cme corrected with estimated subtraction for condition without turbulence studs.
All results exclude keel.
[148]
V/VL = 7.0
y/VL - 1,1
- 1.2
Fig 8. Wave profile at various speeds for the 40-footer
y/VL - LO
y/vi - 7.7
• 7.2
Fig 10. Wave profile at various speeds for the 70-footer
y/VL - LO
y/VL - 7.0
= 7.7
y/VL = 7.2
Wave profile at various speeds for the 55-footer
7.7
y/VL - 7.2
77. Wave profile at various speeds for the 85-footer
[149]
Cw-» V//L - 0.90
*o
Gn-ie , V//C • 100 i !
30
1
:• . . j
%1 i '
'
'••"»• . T • • . ;
20
; '" :i- . •• i ''!,•'. i ' :
. , ^. . ^
• ''•]'," , •,,.'. ' ' •;.»;..;
''• •••-' * ,••.'•»
•V >•' -'^M-.- ••• •••/ ' ... j\ ••
"»'# ' .1 , . '"A, •' L
• ••''•• J ' . '
• . * , ' '''"., .'.''•'*' '
* ' . '' ' i
10
1 [ ll 1 |--.>
. ,. i ' M '
1 "
; -|
i i !•
* liMllmMrtftMMMIlMWMMMMMolMi
j ' j ! A.
.— -^,-~-M«^— , ^ ^
a ~ Oi 10 10 , 2U 25
M MM ^
4TS 410 42i 40
°
0
5- ^ ±. j .1L j _U .. zs .
* i « %
72. Resistance curves of the four optimized vessels compared Fig 13. Resistance curves of the four optimized vessels compared
with input data with input data
Cft-16
25 30
A-_j
«.". 4O
Fig 14. Resistance curves of the four optimized vessels compared Fig. 7.5. Resistance curves of the four optimized vessels compared
with input data with input data
8, S £ S
25 SO
Hg 16. Resistance curves of the four optimized vessels compared
with input data
[150]
30 r
25
20
15
10
5 -
K2V
1-5
4
i-i
>
. 2
4>
u
DATA
0-4
06
0-6
1-0 ® 1-ft 1-4 (M)
4-75 4-50 A 4'25
40
Fig 17. Results for the 40, .5.5, 70 and 85-f<wters at LI speed length ratio compared with existing data
Table 4 gives computer calculated EHP for the four
models.
If time and funds permit, it is hoped that these models
can be tested also at other displacements and possible
trims to complete the data of model tests for the statistical
analysis, and to cover the range of operational conditions
when fishing.
TABLF 4
Computer calculated EHP
K/VI
40ft;
55ft;
70ft;
85ft;
« = 4.00
qvi) - 4.25
<M> - 4.50
<M> - 4.75
.85
3.5
8.8
" 20.1
36.0
.90
5.0
11.4
24.0
42.0
.95
5.3
13.4
28.6
52.2
.00
5.7
15.8
34.7
64.9
.05
6.0
18.6
40.5
72.5
.10
6.2
21.1
48.6
82.7
.15
6.6
23.1
56.6
100.3
.20
11.6
27.1
72.0
139.6
These results are based on ITTC friction formulation and infinite
water.
STABILITY
The stability of the 40-, 55- and 70-ft designs was inves-
tigated by the Danish Ship Research Institute (DSR1),
Lyngby, Denmark. The computation was performed
on their advanced computer G1ER. The stability of
the 85-ft design was investigated by Chalmers Technical
University, Gothenburg, Sweden, on a Facit EDB com-
puter using the program of the Swedish Shipbuilders
Computing Centre, Gothenburg, Sweden.
Each type was investigated with freeboards of five
different heights in order to study the influence of free-
board on stability. The variations were made in 10 per
cent of D increments against the normal height.
Space does not permit giving the hydrostatic curves
and the five isocline stability curve diagrams for each
model. The isocline stability curves were presented for
the case GA/-0. Thus they were showing the residuary
stability levers Af05 for inclinations 5, 10, 15, 20, 30,
45, 60, 75 and 89.9°. The values were given for a range
of drafts so that, while the following stability evaluations
were mainly made for the same displacement at which
the models had been tested, other displacements can
also easily be investigated.
The GZ values are thus calculated
GZ= A/oS+GA/o x sin </;.
Fig 18 illustrates this further. When in the proceeding
investigation each of the models will be expanded or
reduced in length to be comparable with the other
models, GM is then not enlarged or reduced. Only the
factor A/o 5 is enlarged or reduced in proportion to the
length.
The vertical position of the centre of gravity of a
fishing vessel is sometimes expressed as the ratio KG/D.
Fig 18. Sketch showing how the righting lever GZ is made up of a
fixed value depending on GM0 and one factor^ M0S, following the
form and size of the ship
[151]
It mostly varies between 0.7 and 0.8, the higher value
often representative of the light condition and the lower
the loaded condition.
If the freeboard could be increased without increasing
the displacement, the metacentre would remain at the
same height and the centre of gravity would then even-
tually become so high that a negative GM would result.
In practice, of course, it is not possible to increase
freeboard without making an increase in displacement.
Requirements to fulfil Rahola at design displacement
The stability investigation was originally started in
order to find out the optimum freeboard, assuming a
constant KG/D of 0.7 and 0.8 but with the variations
selected it was unfortunately not possible to determine
such an optimum. A more careful analysis made it
obvious that the KG/D constant approach was impracti-
cal and misleading.
Table 5 shows the results of the stability calculation
used as a yardstick only, and for the 40-ft boat in ques-
tion it was found that the minimum permissible GM
according to Rahola increases from 1.2 ft for the 40-ft
version to 1 .35 ft for this form expanded to 85 ft. However,
also the ratio KG/D increases, in this case from .654
to .731; thus, in spite of the larger GM, the centre of
gravity can be comparatively higher for the longer
versions. The centre of gravity of a vessel of the 40-ft
type should not be higher than indicated in table 5
(Rahola minimum) without careful consideration of
specific working conditions.
Table 6 shows the influence of varying freeboards on
the 40-ft vessel. As draft is constant, the deck enters the
water at inclinations from 9.2° to 32.7°, depending on
whether the freeboard is .94 ft or 3.74 ft, representing a
variation of ±20%Z>.
TABLE 6
Results of stability analyses of 40-ft (12.2-m) hull (® - 4.00)
with different freeboards
ror me <tu-u vessel, inis nun was expanded 10 22, /u
and 85 ft and the table gives the resulting drafts, beams
and displacement.
Freeboard
variation -20%/> -10%/>
D 5.60 6.30
D
7.00
+ 10%/> + 20%/>
7.70 8.40
T 4.66 4.66
4.66
4.66
4.66
TABLE 5
freeboard ,94 1.64
2.34
3.04
3.74
Results of stability analyses of 40-ft (12.2-m) hull (® - 4.00)
expanded to 55, 70 and 85 ft
V to deck 9.2° 15.7°
KM 5.77 5.77
21.8°
5.77
27.6°
5.77
32.7°
5.77
L 40 55 70 85
KG/D = .7
B(L/B-3.43) 11.66 16.05 20.45 24.80
KG 3.92 4.41
4.90
5.39
5.88
D 7.00 9.62 12.25 14.90
GM 1.85 1.36
.87
.38
-.11
T(B/T=-2.5) 4.66 6.42 8.18 9.92
KG-T -.74 -.25
.26
.73
1.22
freeboard 2.34 3.20 4.07 4.98
A (L/V* - 4) tons 28.6 74.3 154 275
KlS 5.77 7.94 10.10 12.25
patGZmax 30° 32°
<oatGZ = 0 77.5" 75.2°
35°
72.6U
37.5°
72°
45fl
67.7ft
Rahola minimum
Constant ~GM (= 1.9 ft)
minGM 2.05 1.40
1.20
1.00
1.00
KG 3.87 6.04 8.20 10.35
KG 3.72 4.37
4.57
4.77
4.77
K5/D .553 .628 .670 .695
K5/D .665 .695
.654
.613
.562
KG-T -.79 -.38 .02 .43
KG-T -.94 -.29
-.09
.11
.11
Tr(=Binm)sec 3.6 4.9 6.2 7.6
T, sec 3,4 4.1
4.5
4.9
4.9
TrV(g/B) 5.6 6.8
7.4
8.1
8.1
Rahola minimum
minGM 1.20 1.25 1.30 1.35
All linear measurements in ft
KG 4.57 6.69 8.80 10.90
KG/D .654 .695 .718 .731
KG-T .09 .27 .62 .98
TABLE
7
Trscc 4.5 6.0 7.6 9,0
Results of stability analyses of 55-ft (16.8-m)
hull (® -
4.25.)
TrV(g/B) 7.4 8.5 9.6 10.2
reduced to 40 ft and expanded to 70 and 85 ft
All linear measurements in ft
L 40
B (L/B - 3.7) 10.81
55
14.86
70
18.92
85
22.95
D 6.37
8.75
11.13
13.52
A first investigation was to obtain the GM with which
the hulls were to have a period of roll corresponding
T(B/T = 2.6) 4.16
freeboard 2.21
A (L/V* = 4.25) tons 23.6
5.72
3.03
61.9
7.27
3.86
126
8.83
4.69
226
to their beams in metres, which is an experience rule for
KM 5.35
7,36
9.37
11.37
agreeable rolling. Simplifying the problem and using the
same inertia factor of w = 0.38 (Weiss reference), the
required GM is 1.9 ft for all beams.
If the GM is maintained constant and as the height of
Constant GM (— 1 .9 ft)
KG 3.45
KG/D .542
KG-T - .71
5.46
.623
- .26
7.47
.670
.20
9.47
.700
.64
the metacentre above keel varies linearly, the increase in
Tr (= B in m) sec 3.3
4.5
5.8
7JO
the height of the centre of gravity is relatively greater.
Thus the ratio KG/D being .553 for the hull being 40 ft
Rahola minimum
min GM 1.20
1.20
1.30
1.30
long increases to .695 for its 85-ft version. Therefore, a
KG 4.15
6.16
8.07
10.07
longer boat of the same form as the shorter can have the
KG/D .652
.704
.725
.744
centre of gravity comparatively higher and still have
KG-T -.01
.44
.80
1.24
comfortable rolling motions.
Tf sec 4.1
5.7
7.0
8.5
It was then investigated what minimum GM would be
Wfe/B) 5.0
8.4
9.1
10.1
required to fulfil Rahola's stability criterion, which was
All linear measurements in ft
[152]
The minimum permissible GM for the vessel with
varying freeboards varies from 2.05 ft to 1 ft to satisfy
the Rahola criterion, and the KGJD ratio is highest at
the — 10%Z) version indicating that this freeboard might
be the optimum. However, it must be noted that
KG/D =.7 for this vessel and length is too high to fulfil
Rahola.
TABLE 8
Results of stability analyses of 55-ft (16.8-m) hull I
with different freeboards
4.25)
Freeboard
variation
-20%D
— 10%/>
D
-I 10%/)
j 20%/>
D
7.00
7.88
8.75
9.62
10.50
T
5.72
5.72
5.72
5.72
5.72
freeboard
1.28
2.16
3.03
3.90
4.78
<p to deck
9.8°
16.2°
22.4°
27.7°
32.8°
KM
7.36
7.36
7.36
7.36
7.36
KG/D - .7
KG
4.90
5.42
6.13
6.74
7.36
GM
2.46
1.94
1.23
.62
0
KG-T
-.82
-.30
.41
1.02
1.64
(p at GZ max
32.5°
35°
38"
42.5°
45°
V at GZ - 0
83.5°
81°
79°
78.5°
72.5°
Rahola minimum
min GM
2.30
1.70
1.20
1.00
.90
KG
5.06
5.66
6.16
6.36
6.46
KG/D
.723
.718
.704
.662
.615
KG-T
.66
-.06
.44
.64
.74
TrSec
4.1
4.8
5.7
6.3
6.6
TrV(g/B)
6.1
7.1
8.4
9.3
9.8
Table 9 for the 70-footer shows again that the longer
the vessel, the higher is the permissible centre of gravity.
In this case quite high GASs are required to fulfil Rahola's
criterion but, because the metacentre is comparatively
high, the centre of gravity is still higher than for the
40- and 55-footers.
Table 10 shows that for 70 ft length, a KG/D = .7 well
fulfils Rahola's criterion; again the longer vessel permits
a larger KG/D value. The maximum KG/D for the
70-footer is at — 20 %Z), the lowest freeboard inves-
tigated.
TABU- 10
Results of stability analyses of 70-ft (21.3-m) hull <
with different freeboards
- 4.50)
All linear measurements in ft
Table 7 for the 55-footer shows a similar trend as that
for the 40-footcr. Table 8, showing the influence of the
height of freeboard, diflers somewhat from table 6 for
the 40-footer, the "best" KG/D values for minimum
Rahola arc, in this case, for the -20%D version. For
freeboards equal to -20%Z> to D the KG/D =.7 con-
Freeboard
variation
•-20/o/}
10 %[)
D
-{ 10 %D
-i-20%D
D
8.00
9.00
10.00
11.00
12.00
T
6.52
6.52
6.52
6.52
6.52
freeboard
1.48
2.48
3.48
4.48
5.48
(p to deck
8.9°
14.7°
20.2°
25.3°
30. r
KM
10.28
10.28
10.28
10.28
10.28
~KG/D .7
KG
5.60
6.30
7.00
7.70
8.40
GM
4.68
3.98
3.28
2.58
1.88
KG-T
-.92
- .22
.48
1.18
1.88
q> at GZ max
32°
32.5°
36°
37"
46°
9»atGZ-0 ;
.90°
90
-90°
-90°
>90°
Rahola minimum
min GM
3.40
2.70
1.90
1.60
1.20
KG
6.88
7.58
8.38
8.68
9.08
KG/D
.861
.843
.838
.790
.757
KG-T
.36
1.06
1.86
2.16
2.56
Tr sec
4.3
4.9
5.8
6.3
7,3
WCg/B)
5.6
6.4
7.5
8.2
9.5
All linear measurements in ft
TABLE 11
Results of stability analyses of 85-ft (25.9-m) hull ( M
reduced to 40, 55 and 70 ft
4.75)
length seems to permit a higher KG.
TAHI c 0
L
B (L/B - 4.02)
D
T (B/T - 2.94)
40
9.95
5.31
3.39
55 70
13.70 17.40
7.30 9.28
4.66 5.93
85
21.20
11.28
7.33
Results
of stability analyses of 70-ft (21.3-m) hull OK- -
reduced to 40 and 55 ft and expanded to 85 ft
-. 4.50)
freeboard
A (L/V* - 4.75) tons
KM
1.92
17.1
5.05
2.64 3.35
44.3 91.5
6.95 8.83
3.95
163.2
10.72
L
B (L/B -=
D
3.7)
40
10.81
5.72
55
14.86
7.86
70
18.9}
10.00
85
22.95
12.13
Constant GM (-- 1.9ft)
KG
3.15
5.05
6.93
8.82
T (B/T =
2.9)
3.72
5.12
6.52
7.93
KG/D
.593
.692
.747
.782
freeboard
2.00
2.74
3.48
4.20
KG-T
- .24
.39
1.00
1.49
A (L/?* -
4.50) tons
19.8
51.7
106.6
190.0
Tr (— B in m) sec
3.0
4.2
5.3
6.5
KM
5.87
8.08
10.28
12.48
Rahola minimum
Constant GA7(= 1.9 ft)
min GM
1.20
1.30
1.40
1.50
KG
3.97
6.18
8.38
10.58
KG
3.85
5.65
7.43
9.22
K5/D
.694
.787
.838
.872
KG/D
.725
,774
.801
.817
KG-T
.25
1.06
1.86
2.65
KG-T
.46
.99
.150
1.89
Tr (=* B in m) sec
3.3
4.5
5.8
7.0
Tr sec
3.8
5.1
6.2
7.3
D L I • TrA/(g/B)
6.9
7.8
8.4
9.0
Kaftoia minimum
min GM
1.60
1.90
1.90
2.20
All linear measurements
in ft
KG
4.27
6.18
8.38
10.28
KG/D
.746
.765
.838
.847
KG-T
.55
1.06
1.86
2.35
Table 11 and 12 for the 85-footer show
similar
trends
Tf sec
3.6
4.5
5.8
6.5
as in previous cases.
TVvXg/B)
6.2
6.6
7.5
7.7
If the 55-, 70- and
85-ft hulls
are all reduced to
40ft,
All linear measurements
in ft
tables 13, 14 and 15
, one still
finds that
at lower free-
153]
TABLE 12
Results of stability analyses of 85-ft (25.9-m) hull (® = 4.75)
with different freeboards
TABLE 13
Results of stability analyses of 55-ft hull (M - 4.25) reduced
to 40 ft with different freeboards
Freeboard
variation
D
-20%D
9.02
10.15
D
11.28
12.41
•i 20%/>
13.54
T
7,33
7.33
7.33
7.33
7.33
freeboard
1.69
2.82
3.95
5.08
6.21
<p to deck
9.1°
14.9°
20.4°
25.6°
30,3°
KM
10.72
10.72
10.72
10.72
10.72
KG/D - .7
KG
6.32
7.11
7.89
8.68
9.48
GM
4.40
3.61
2.83
2.04
1.24
KG-T_
-1.01
-.22
.56
1.35
2.15
g> at GZ max
36"
37.5'
4r
44°
49.5°
patGZ=^0
>90fl
: 90°
-90'
90°
>90°
Rahola minimum
min GM
2.90
2.10
1.50
1.00
.90
K5
7.82
8.62
9.22
9.72
9.82
KG/D
.867
.848
.817
.783
.724
KG-T
.49
1.29
1.89
2.39
2.49
Tf sec
5.2
6.2
7.3
8.9
9.4
TrV(g/B)
6.4
7.6
9.0
10.9
11.5
All linear measurements in ft
boards more GM is required to satisfy Rahola. Fig 19
shows the freeboard and the centres of gravity for the
models compared at the 40 ft length. This figure is then
for boats of the same length but with different displace-
ments.
The freeboards have different heights because, as was
stated earlier, while they arc inter-related, the freeboard/
length ratio was not kept the same. In fig 20 the values
from fig J9 have been re-plotted so that the height of
the centre of gravity for each model could be compared
at the same freeboard. The trend is the same as in the
previous figure and generally it can be said that the centre
D-20*
D-10%
0*10%
0*20%
Fig 19. Comparison of freeboards \ permitted height of the centre of
gravity and required GM for the four optimized -models at various
heights of freeboard and all reduced to a length of 40 ft
Freeboard
variation
D
5.09
5.13
D
6.37
7.00
7.64
T
4.16
4.16
4.16
4.16
4.16
freeboard
.93
1.57
2.21
2.84
3.48
<p to deck
KM
9.8°
5.35
16.2°
5.35
22.4°
5.35
27.7°
5.35
32.8°
5.35
Rahola minimum
min GM
1.90
1.40
1.20
1.00
1.00
KG
3.45
3.95
4.15
4.35
4.35
KG/D
.677
.689
.652
.622
.569
KiG-T
- .71
-.21
-.01
.19
.19
Tr sec
3.3
3.8
4.1
4.6
4.6
T,V(g/B)
5.7
6.6
7.1
7.9
7.9
All linear measurements in ft
TABLU 14
Results of stability analyses of 70-ft hull ( M =- 4.50) reduced
to 40 ft with different freeboards
Freeboard
variation ~20%/> - 10%J> D 10%D f20%D
D 4.57 5,14 5.72 6.28 6.86
T 3.72 3.72 3.72 3.72 3.72
freeboard .85 1.42 2.00 2.56 3.14
<p to deck 8.9° 14.7' 20.3f> 25.3" 30.2"
KM 5.87 5.87 5.87 5.87 5.87
Rahola minimum
minGM 2.40 2.00 1.60 1.30 1.20
KG 3,47 3.87 4.27 4.57 4.67
KG/D .760 .752 .746 .727 .681
KG-T -.25 .15 .55 .85 .95
Trsec 2.9 3.2 3.6 4.0 4.2
Trx/(g/B) 5.0 5.5 6.2 6.9 7.2
All lir
4
ft
3
2
1
0
iear measurements in ft
/
/
•
/
/ LWL
*
^lS)-4.75
:==^
tf^^
®^
£^TOO
/
t
'/
Fraiboord
Fig 20, Comparison of the permitted height of the centre of gravity
in relation to the waterline of the four optimized models all reduced
to 40 ft and compared at the same freeboard. Due to the fact that
LIB was not varied concurrently, there is a different trend in the ®
values
[154]
TABLE 15
Results of stability analyses of 85-ft hull (M - 4.75) reduced
to 40 ft with different freeboards
Freeboard
variation
20 %/>
- 10%/)
D
1 10 "-£/}
•1 20°£/j
D
4.25
4.78
5.31
5.84
6.37
T
3.39
3.39
3.39
3.39
3.39
freeboard
.86
1.39
1.92
2.45
2.98
(p to deck
KM
9.8°
5.05
15.6°
5.05
21. 1°
5.05
26.2°
5.05
30.9°
5.05
Rahola minimum
min GM
1.90
1.60
1.20
1.10
1.10
KG
3.15
3.45
3.85
3.95
3.95
KG/D
.741
.721
.725
.677
.621
KG-T
.24
.06
.46
.56
.56
Tf sec
3.0
3.3
3.8
4.0
4.0
Tf\/(B/B)
5.4
6.0
6.9
7.2
7.2
All linear measurements in ft
of gravity in the smaller displacement boats can be
higher. This must be due to the fact that the height of
the mctacentre depends largely on the moment of
inertia of the water plane divided by the displacement
(//V) and to a smaller extent to the vertical distribution
of displacement. The curve for ^ = 4.50 does not fall
between the curves for 4.75 and 4.25 where it perhaps
could have been expected. However, this can be explained
by the fact that L/B, according to table 2, has not been
varied in proportion to length but was simply selected
as the one giving the lowest resistance during the com-
puter optimization process. Thus the beam for the
models having i>t=4.25 and 4.50 are the same and as
the displacement for the 4.50 version is the smallest, the
resulting height of the metacentrc will be higher.
It was earlier found from table 9 and 10 that the
70-footer required comparatively large GM to fulfil the
Rahola criterion. This seems to be due to a somewhat
particular relationship between water plane area and
displacement. For a long time it has been known that
deep and narrow ships have an entirely different type
of GZ curve from wide and shallow ones and this
seems to be an example of this.
Had L/B as well as B/T been varied equally for the
models, the curves for highest permissible G in fig 19
would probably have fallen more concurrently.
The evaluation shows now how much the stability
range seems to be influenced by the choice of main
dimensions and should constitute a warning not to
generalize from one case to another.
Rolling motions in relation to minimum stability
It has been suggested by Mockel (I960), Traung (1955;
1960) and Gurtner (p. 429) from interviews with fisher-
men and personal observations that the most agreeable
period of roll is in relation to the beam of the vessel.
Values of 1 .0 to 1 . 1 B (B in metres) have been mentioned as
suitable periods of roll (in sec). Kempf (1940) proposed a
non-dimensional roll number = Tr^/g/B, now known as
Kempfs roll number. He interviewed operators of
vessels of various types and sizes to obtain their opinions
on most pleasant rolling motions and he suggested that
the roll number should be between 8 and 14. The Kempf
roll number, in fact, contains the roll accelerations which
are determined by comparing the period of roll with the
square root of the beam of the vessel.
The suggestion to use B as a yardstick can have practi-
cal advantages because, in this way, one can use the
period of roll as a measure of GM and simply specify, if
one considers GM alone as a suitable stability criterion, a
maximum permissible period of roll in relation to beam.
As a matter of fact here, too, it has often been stated
that the period of roll of 1.0 to LIB in metres always
ensures a safe ship if the freeboard is reasonable.
The Kempf roll number definitely permits better
comparison between vessels of widely differing sizes but
it seems to be difficult to specify a certain number
above which the stability of a vessel would be critical.
10
/
40 tt
55 tt
70 tt
85 tt
16
20
24ft
Hg 21. Maximum permissible periods of roll for the models all
reduced to 40 ft plotted against their beams at normal depth. These
values are compared with curves showing Kempf' s recommendations
for stiff and tender ships and with other curves showing periods of
roll being 1-0 to I -I B. Obviously smaller ships have to be stiff er than
Kempf found agreeable .
Fig 21 shows, for the investigated vessels, plots of the
different lengths and length displacement ratios at
normal depth compared with the above-mentioned
values of the rolling period. Table 5, 7, 9 and 11 also
show the Kempf roll numbers for each specific case.
The general conclusion is that for boats with a beam
of less than about 20 ft the suggestion to use beam in
metres as a criterion for agreeable rolling periods in sec,
produces boats which, according to Kempf, are too stiff.
On the other hand, a longer period of roll would not be
possible if the boats should fulfil Rahola.
Fig 21 shows that for the 40-, 55- and 85-footers
(®=4, 4.25 and 4.75) a permissible period of roll to
fulfil Rahola is about L2B in metres. Thus, in this case,
if one stipulates that the boats shall have a period of roll
of maximum LIB, one is certain that they will fulfil
[155]
Rahola. However, the plots for the 70-footer (®=4.50)
show that it requires a shorter period of roll so it is
really impossible to generalize and say that a period of
roll of I. IB would be safe.
Fig 21 compares boats of normal depth and thus
normal freeboard. For higher freeboards, up to a certain
point, GM could be less because the higher freeboard
produces better stability levers and a longer stability
range. Fig 22 demonstrates this. In this case the ratio
period of roll/beam has been plotted in relation to the
ratio freeboard/beam.
ttc/m
0.1
Fig 22. Maximum permissible Tf IB-ratios for different freehoard/B-
ratios compared with Tr — 1.0 to 1.1 B. All hulls reduced to 40 ft
length
The periods of roll express the minimum GM required
to fulfil Rahola and indicate that the ideal freeboard
from the minimum GM point of view would be about .3if.
However, as fishermen feel unsafe at periods of roll
longer than I .IB in metres, it might be difficult to
utilize the improved stability characteristics associated
with an unusually high freeboard, this will also make
operation of fishing gear more difficult.
The whole problem of optimum freeboard from the
point of view of stability, roll behaviour and economy of
construction can therefore not yet be determined after
this investigation. So far the stability has been discussed
for the designed waterline and the next investigation was
to consider how much the hulls can be loaded before
the stability becomes insufficient.
Influence of loading
Even if a vessel has satisfactory stability at the designed
waterline, it must naturally be investigated that it also
has satisfactory stability when light or loaded. Normally
it is more difficult to obtain sufficient stability at the
loaded condition than the light but this is not always so.
The following investigations are only concerned with
heavier loading than at the designed displacement.
Furthermore, it is important to know whether during
loading the centre of gravity rises or not. In fishing vessels
with normal storage of fuel (not bottom tanks) the centre
of gravity doesn't usually rise unduly and for simplicity's
sake the vessels have been investigated assuming the
centre of gravity to be in the same position as before.
Table 16 to 19 summarize the calculations for the
40-, 55-, 70- and 85-footers. Because the height of
metacentre varies with loading there will be a change in
GM and this naturally affects stability levers and stability
range. The MQ S curves also vary with the draft. Table 16
TABLE 16
Influence of loading on dynamic level of 40-ft hull <
(normal D)
=-4.00)
T
4.66
5.00
5.50
6.00
freeboard
2.34
2.00
1.50
1.00
KM
5.77
5.81
5.89
6.00
GM
1.90
1.94
2.02
2.13
KG
3.87
3.87
3.87
3.87
KG-T
-.79
-1.13
-1.63
-2.13
(p at GZ max
45°
46°
45,5°
45.5°
<P at GZ =* 0
>90°
>90°
>90°
>90°
e at (p = 40°
.467
.461
.439
.362
All linear measurements in ft
e^= dynamic lever (Rahola minimum .262 ft)
TABLL 17
Influence of loading on dynamic lever of 55-ft hull «gD
(normal D)
4.25)
T
5.72
6,50
freeboard
3.03
2.25
KM
7.36
7.42
GM
1.90
1.96
KG
5.46
5.46
KG-T
-.26
-1.04
q> at GZ max
41°
42.5'
<p at GZ — 0
>90°
>90
e at <p — 40°
.466
.448
All linear measurements in ft
e— dynamic lever (Rahola minimum .262 ft)
TABLE 18
Influence of loading on dynamic level of 70-ft hull (®
(normal D)
4.50)
T
6.52
7.52
8.52
9.00
freeboard
3.48
2.48
1.48
1.00
KM
10.28
10.05
10.03
10.06
GM
1.90
1.67
1.65
1.68
KG
8.38
8.38
8.38
8.38
KO-T
1.86
.86
-.14
-.62
<p at GZ max
32°
25.5°
20°
15.5°
y at GZ - 0
58°
50°
42.5°
36.5°
e at GZ max
.271
*
*
*
All linear measurements in ft
* Non-sufficient according to Rahola
e— dynamic lever (Rahola minimum .262 ft)
to 19 assume a "starting" GM of 1.9 ft, which was the
one selected to provide a period of roll equal to the
beam in metres. This GM has varying degrees of built-in
safety factors. Minimum GM according to Rahola, is
1.2, 1.2, 1.9 and 1.5 ft for the 40-, 55-, 70- and 85-footers
respectively. From this it is obvious that it should be
possible to decrease stability by loading of the 40- and
[156]
TABLE 19
Influence of loading on dynamic lever on 85-ft hull (®
(normal D)
• 4.75)
T
7.33
8.00
9.00
9.50
freeboard
3.95
3.28
2.28
1.78
KSi
10.72
10.68
10.75
10.83
c?M
1.90
1.86
1.93
2.01
KG
8.82
8.82
8.82
8.82
KG-T
1.49
.82
-.18
-.68
g> at GZ max
36°
34.5°
30°
28°
q> at GZ =- 0
70°
68°
63°
60.5°
e at GZ max
.377
.338
.247*
.216*
All linear measurements in ft
* Non-sufficient according to Rahola
e— dynamic lever (Rahola minimum .262 ft)
TABLE 21
Influence of loading on dynamic lever for 70-ft hull (®
reduced to 40 ft
'4.50)
T
3.72
4.30
4.87
5.14
freeboard
2.00
1.42
.85
.58
KM
5.87
5.75
5.73
5.75
GM
1.90
1.78
1.76
1.78
KG
3.97
3.97
3.97
3.97
KG-T_
.25
-.33
-.90
-1.17
<P at GZ max
36°
34°
32°
3r
V at GZ == 0
>90°
85°
>90°
>90°
e at GZ max
.342
.286
.223*
.188*
All linear measurements in ft
* Non-sufficient according to Rahola
e— dynamic lever (Rahola minimum .262 ft)
TABLE 20
Influence of loading on dynamic lever on 55-ft hull (@ = 4.25)
reduced to 40 ft
TABLE 22
Influence of loading on dynamic lever for 85-ft hull i
reduced to 40 ft
4.75)
T
4.16
4.73
T
3.39
3.70
4.16
4.39
freeboard
2.21
1.64
freeboard
1.92
1.61
1.15
0.92
KM
5.35
5.40
KM
5.05
5.02
5.06
5.10
GM
1.90
1.95
GM
1.90
1.87
1.91
1.95
KG
3.45
3.45
KG
3.15
3.15
3.L5
3.15
KG-T
-.71
-1.28
KG-T_
-.24
-.55
-1.01
-1.24
<p at GZ max
47.5°
46°
<p at GZ max
45°
44°
45°
45°
V at GZ « 0
>90°
>90°
<p at GZ =* 0
>90"
>90°
:-90°
>90°
e at y = 40°
.459
.448
e at v -T 40'
.446
.436
.414
.398
All linear measurements in ft
e— dynamic lever (Rahola minimum .262 ft)
All linear measurements in ft
c— dynamic lever (Rahola minimum .262 ft)
20
10
\
0.4
0.6
08
10
18
+12
+ 4
14
16
18
20
22
24
4.65 445443 431 427
Fig 23. Computed resistance values for some typical fishing vessels compared with the minimum line for the FAO data at JJ Froude number
55-footers more than the 70- and 85-footers. Table 16
to 19 also show that the 40-footer can be loaded down
to 1 ft freeboard but that the 70-footer cannot be loaded
at all without increasing the GM at the designed waterline.
If the 55-, 70- and 85-footers are reduced to 40 ft the
resulting GM will be according to table 20, 21 and 22,
which indicate that the same form of hull which, in its
original size, had a rather restricted range of stability
now has improved stability levers. Except the 70 ft
type, table 21, which seems to be a special case, the
[157]
TABLE 23
Computer analysed results for some existing fishing vessels
File
No.
Cmm,ry
LJt
Ship
A
tons
*
LIB
BIT
Cm
CP
l.c.b.%
i..»
!*•
<*•
trim
CRU at
P/VL-I.I
4
1?
Australia
Sweden
57.50
86.0
69.60
171.8
4.27
4.31
3.36
3.57
2.73
2.55
0.667
0.641
0.580
0.629
-2.14
-0.605
21°
28"
36°
38.5°
20.5°
22°
0.041
0.040
17.8
18.9
13
18
19
21
Sweden
Senegal (FAO)
India (FAO)
Thailand (FAO)
102.75
39.37
45.0
47.93
234.6
19.65
30.10
31.20
4.65
4.45
4.43
4.65
4.28
3.20
3.41
3.88
2.44
3.24
3.10
3.14
0.672
0.670
0.700
0.790
0.661
0.552
0.595
0.578
-1.01
-1.50
-1.19
• 3.17
29"
26"
25*
20"
45"
40*
55°
53°
26.5°
16°
17°
12'
0.048
0.043
0.038
0.042
27.1
21.6
19
17.2
55 and 85-ft types will be stable within the whole
depth range investigated when reduced to 40 ft.
The investigations show that when the same type of
hull form is changed in size, completely different stability
conditions prevail and this may well be the reason why
boats can become utterly different when changed in size
without any alteration in the form shape.
To have sufficient stability the centre of gravity must
be kept below the values given.
INVESTIGATION OF EXISTING BOATS
Time did not, unfortunately, permit a comprehensive
evaluation of a number of existing designs in an attempt
to ascertain how much these designs could be improved.
Table 23 shows parameters of some typical designs in
FAO's files and their C?16 values for K/\/Z=l.l are
shown in fig 23. This fig is similar to fig 17.
Boats 12 and 13 represent modern Swedish steel
trawlers and are specially interesting because model 13
is a simple elongation, with a parallel middle body, of
model 12. By elongating the vessel some of the para-
meters are changed and the result is rather surprising.
Fig 23 shows that the short boat has about 35 per cent
larger resistance than the minimum line for vessels
investigated for the statistical analysis. Thirty-five per
cent increase in resistance means roughly 35 per cent
increase in fuel consumption. There should really be a
saving for the elongated vessel rather than an increase in
power requirement.
1158]
A Free Surface Tank as an Anti-rolling
Device for Fishing Vessels
by J. J. van den Bosch
Utilisation (Tune citerne 6 carene liquide comme amortisseur de
roulis & bord des bateaux de peche
L'auteur passe en revue divers sysltanes d'amortissement du roulis
pour voir s'ils satisfont aux besoins des bateaux de peche. Le choix
se porte sur une citerne constitute par un paral!616pipede rectangle,
dans lequel Ttaergie est fournie par un simple effet de "mascaret".
Des equations mathdmatiques th6oriques de mouvement sont
formulas pour un batiment roulant librement dans un fluide, et
Ton etudic Tinfluencc de divers parametres sur le mouvement.
L'6quation est ensuite modifiec pour tenir comptc de 1'installation a
bord du batiment d'une citerne simple & carene liquide. La section
qui suit est consacree aux donnees relatives a un reservoir paralldle-
pipedique et a 1'cflfet des paramdtres du reservoir sur le roulis.
L'auteur deer it une citerne concue pour un batiment particulier,
pour trois conditions de deplacement, et construit des courbes
thtariques qui sont comparees avec les res ul tats de quatre series
d'cssais sur modele. II dtudie les variations par rapport aux resultats
th6oriques, et termine en presentant di verses suggestions.
El tanquc de balance con superficies libres como estabilizador para
barcos de pesca
Se estudian y comparan varios tipos de estabilizadores, en orden a
los requisites de uno adecuado para los barcos de pesca. Se elige un
simple tanque rectangular, de forma de caja, que aprovecha la
energia de la ola de marea. Se desarrollan ecuaciones te6rico-
matem£ticas dc movimiento de una cmbarcacidn que se balancea
libremente en un liquido, cstudiandosc el efecto de los di versos
parametros sobre el movimiento. La ccuaci6n se modifica despues
para instalar en la embarcacion un simple tanque con superficies
libres. La secci6n siguiente trata dc los datos dc un tanque rec-
tangular y la infiuencia dc sus parametros en el movimiento de
balanceo.
Se expone un ejemplo de disefto de tanque para un tipo deter-
minado de emharcacion, con tres condiciones de desplazamicnto, y
se presentan cubiertas teoricamente calculadas, comparAndolas con
cuatro series de ensayos de modelos. Se discutcn las variaciones
de los resultados teoricos y se haccn, por ultimo, algunas suge-
rencias.
THERE is no doubt that many fishing vessels
would benefit from the installation of some means
of roll damping to ease deck working conditions
and increase effective fishing time. The major types of
roll damping devices now in use are:
• Active fins
• Passive tanks based on the U-tube principle
• Active tanks based on the IMubc principle
• Passive free-surface tanks
This paper deals with the application of the passive
free-surface tank in its simplest form.
Bilge keels are excluded from this discussion because
other roll damping devices arc considered as supple-
mentary rather than as an alternative to bilge keels.
This is discussed more fully at the end of the paper.
A fishing vessel's damping system should be:
• Effective even at low or zero speeds
• Efficient for many conditions
• Inexpensive to install and maintain
• Trouble-free in normal use
Active fins are not effective at low speed. Initial costs
are relatively high.
Passive tanks based on the U-tube principle are often
rather sensitive to differences in the natural roll period
of the ship, and if designed to cover a wider frequency
range the overall efficiency falls.
Activated U-tanks are efficient over a wide range of
conditions. They seem good for large boats, but are
complicated and may be too costly for small boats.
Although passive free-surface tanks are less efficient
than activated U-tanks, they are simple to install and
perform satisfactorily in most conditions.
ROLLING MOTION ACCORDING TO
SIMPLIFIED THEORY
Rolling without tank in operation
The equation of motion. In recent years the theoretical
approach to ship motions has been improved, and
frequently a simplified mathematical model is used, such
as the damped linear mass-spring system (Vossers, 1960).
For the calculation of the influence of the tank on the
ship's rolling motion this same method is used only
considering the rolling motion. The equation of motion
is given by the expression :
Irf + Nd + Rrf** K
If the exciting moment A' varies sinusoidally with time,
the resulting motion would also be sinusoidal and of the
same frequency. The moment, however, will always be
in advance of the motion. The phase angle between the
moment and the motion varies from zero, for very low
frequencies, to 180", for high frequencies. If the moment
is expressed by:
and the motion by:
(p = <[>a sin cof
The solution of the above equation is expressed by:
K«
and:
tang
[159]
Often the amplitude is written in the form of a magni-
fication factor, that is, the ratio of the motion amplitude
at a certain frequency to the static angle of heel under
influence of a heeling moment of the same magnitude.
At the natural or resonance frequency:
the phase angle becomes 90° and the magnification factor
can become very large if the damping is relatively small.
A criterion of damping is the non-dimensional damping
coefficient:
N
At resonance the magnification factor amounts to:
The influence of the separate coefficients
Using the above expressions a qualitative analysis of the
influence of the separate coefficients can be made:
• An increase of /^ is accompanied by a decrease of
the natural frequency. At the same time the
magnification factor increases because of the in-
fluence of 7^ on v^
• An increase of R^ results in a shift of a>0 towards
a larger value and also in an increase of the
magnification factor at resonance
• An increase of N+ results in smaller amplitudes
over the entire frequency range
These tendencies are illustrated in fig 1 Starting from
an amplitude characteristic with v^=0.1 (a probable
value for rolling) and o^=l, the effect is shown of a
doubling of one of the coefficients while the other two
remain unaltered.
Influence of the tank on rolling motion
Fundamental behaviour of the tank
When a tank, partially filled with a liquid, say water,
is forced to oscillate about a fixed axis, the water move-
ment creates a moment acting about the same axis.
When the motion of the tank is sinusoidal the moment
appears to be mainly sinusoidal of the same frequency
as the motion, with a phase lag ranging from zero to
180° depending on the frequency. The natural frequency
of the system is defined as the frequency at which the
phase angle equals 90°.
The moment can be resolved in a component which
is in phase with the motion and the quadrature com-
ponent which has a phase lag of 90° with the motion.
Expressed mathematically:
the motion is:
$ = (f>a sin wt
and the moment :
M = Mflsin(o>f + e,)
= M a sin <Dt cos e, -f Ma cos tot sin et
The first term is the in-phase term and the second is the
term with a 90° phase difference. In fig 2 the amplitude
and the phase angle are shown as functions of the fre-
quency, and in fig 3 the corresponding components are
given. Both figures serve only as examples to illustrate
the tendencies.
Fig 1. Influence of coefficients of equation of motion
0) sic"1 —
Fig 2. Amplitude and phase of tank moment
[160]
MaSINEt
Mgcoset
0) sec'
Fig 3. Components of tank moment
The equation of motion with the tank in operation
Consider the tank moment as an external moment
acting on the ship on a fore and aft axis through the
centre of gravity of the ship. The equation of motion is:
'* <£ + N+ 0 + Rf <f> = Ka sin (cot + eA
With </>
(*.->
(j)a sin cot this expression becomes:
y2 — pcose, } sin cot +
4- [N^co — . ;-' sine r) cos cot = -' --si
V;fl / Va
The reduced in-phase component (MJ<l)a) cos r.t can
be considered as a reduction of /?0-/o>2. The reduced
quadrature component (A/fl/</O sin er can be considered
as an augmentation of the damping when sin c, is
negative, i.e. throughout the entire frequency range con-
sidered.
Influence on amplitude characteristic
Utilizing the above, the influence of the components of
the tank moment (fig 3) can easily be combined with the
curves in fig 1. Assuming that the natural frequencies of
the tank and the ship differ little, it follows:
• From fig 3 it appears that the in-phase component
of the tank moment is positive for frequencies
below the natural frequency of the tank. For this
range the amplitude characteristic of the ship,
including the tank, tends to the curve on the left
in fig 1. The positive value of (MJ<l>a) cos ef has
the effect that the vessel seems to have a longer
natural period. (Reduction of /fy or augmentation
of/,.)
• The quadrature component can be considerable
if compared to the ship's own damping and
because of this the reduction of the amplitude in
the range around the combined natural frequency
can be very large
• For the range beyond the natural frequency of the
tank the vessel obtains the character of a stiffer
ship due to the negative in-phase component
15 r
°'5 U sec'1'0-
Fig 4, Schematic presentation of tank influence
Fig 4 shows a tentative curve of the amplitude versus
frequency for the ship-plus-tank system. Notable is the
occurrence of the two secondary peaks in the curve. This
is a principal feature of a system with two degrees of
Fig 5
[161]
freedom, which are here the rolling of the ship, and the
motion of the tank water. The flatter the phase charac-
teristic of the tank, the wider the frequency range which
is covered by the quadrature component, and the more
these two secondary peaks are smoothed.
If the natural frequency of the tank is higher than the
natural roll frequency of the ship, the secondary peak in
the lower range is more accentuated, while the other one
can disappear completely.
RECTANGULAR TANK DATA
General
The free surface tank owes its damping characteristics
to the development of a bore, a typical shallow water
wave. Fig 5 shows two photographs of this phenomenon
in two consecutive stages. It is evident that with every
roll work is done in raising the tank water, thus reducing
the energy of motion. The theoretical natural frequency
for small amplitudes can be derived as follows:
The velocity of propagation of this type of wave is :
c =
The distance travelled in one period is twice the breadth
of the tank so the natural period is:
2b
and the natural frequency is:
2n n f—
°>t = ^ « T V0/1
T, b
A series of tests shows that an increase of the amplitude
of the motion induces the actual natural frequency to
increase.
to
u>vy5 ,
fig 6. Non-dimensional amplitude and phase of tank moment for 5/6=0
[162]
15
aon
05 TO U»VJ7g ^ 1*
Fig 7. Non-dimensional amplitude and phase of tank moment for Sib —0.20
The data shown in fig 6, 7, 8 and 9 arc results of
experiments with a model tank excited by an oscillating
mechanism. While the tank performed a swinging
motion the moment about the axis of rotation was
measured. In fig 6 and 7 the phase and the reduced
moment amplitude are shown versus the reduced fre-
quency a>^/b/g and in fig 8 and 9 the sine and cosine
components are given. The amplitude is made non-
dimensional by dividing by ptgb3 1.
Influence of parameters
There are six parameters which control the tank moment:
• The motion amplitude (f>a
If (f>a increases the moment amplitude does not
increase at the same rate and so the tank is less
effective when the motions are large
[163]
The influence of the frequency of the motion a) is
evident from fig 6, 7, 8 and 9
The tank breadth h
The moment amplitude varies with the third
power of the tank breadth provided that the ratio
of the water depth and the breadth is kept con-
stant ; (the breadth is measured across the ship)
The tank length /
The moment is directly proportional to the tank
length (measured in fore and aft direction)
The water depth //
As is shown, the natural tank frequency depends
on the breadth and the water depth. In addition
to this influence on the phase relation, the depth
of the water influences the total weight and there-
fore the moment
The height of position s
The vertical height of the position of the tank is
F2
S/b»-O.2O
~" ~T
S/bs-0.20
Non-dimensional components of tank moment for S/b=0 Fig 9 Non-dimensional components of tank moment for S/b 0.20
measured from the axis of rotation to the tank
bottom. A negative value means that the tank
bottom is situated below the axis of rotation
A comparison of fig 6 and 7 or 8 and 9 indicates
that a more highly situated tank produces a larger
stabilizing moment
Considerations for application
• The presented data can be used for ships with
.' values ranging from 0.03 to 0.18
B
• The static reduction of GMt due to the free sur-
face of the tank must be acceptable. The loss of
static stability can demand a restriction of the
tank dimensions. The reduction of GA/t should
not be taken into account while the ship's own
natural period is being calculated
% A roll damping tank should, if possible, extend
over the full breadth of the vessel because of the
large influence of the breadth on the moment
amplitude
• The tank should be situated as high as possible
• From experience it is known that the minimum
depth of the tank should be approximately three
times the water depth in the tank. This influences
the position of the tank in height. As a preliminary
estimation for the tank depth the value Dt = 2 GMt
can be used
• The data which are shown in fig 6, 7, 8 and 9 are
results of measurements with 0fl=0.10 radians or
about 6°. The calculation of the influence of the
tank on the rolling motion is based on the assumed
linearity of the system. When the results are
interpreted, it has to be borne in mind that this
assumption is not strictly true
• The diversity of conditions under which a vessel
has to fulfil its task makes it very difficult to
suggest an optimal design for the anti-rolling tank,
and for that reason a compromise has to be found.
EXAMPLE OF APPLICATION
Ship and tank data
As an example the design of an anti-rolling tank for a
small trawler is discussed. The GMt/B values of this
[164]
ship are fairly high in order to comply with Rahola's
stability criteria. Such a vessel, operating on the North
Sea or in comparable areas, often meets conditions which
may cause it to roll heavily.
The main dimensions are :
Ux10
91. 87 ft (28.00m)
Lpp = 78.42 ft (23.90m)
B =20.28 ft (6.18m)
D =11.36 ft (3.46m)
From a variety of possibilities three tentative loading
conditions were selected for further investigation. The
conditions are summarized in table 1 .
TABLE 1 : Considered loading conditions
Condition
A
B
C
Quantity
Leaving
port
During
fishing
A verage
of other
conditions
A tons (ton)
161.4(164)
184.1 (187)
172.2(175)
GMt ft (m)
2.75 (0.84)
1.87 (0.57)
2.36 (0.72)
GMl . .
0.136
0.092
0.117
B
J^-0-4 B ft (m)
8.11 (2.46)
8.11 (2.46)
8.11 (2.46)
7> sec
5.39
6.55
5.83
<i>4 sec*1
1.165
0.960
1.079
v+ .
0.07
0.07
0.07
KG ft (m)
9.12 (2.78)
9.97 (3.04)
9.55 (2.91)
5/6 .
-0.125
-0.175
- 0.150
The "fishing condition" (B in the table) was rather
extreme. For the calculation of GMt it was assumed that
the consumption of fuel and stores was about 22 tons,
that the fish hold contained about 15 tons catch and that
a new catch weighing about 30 tons lay on deck.
The values of GMt for the conditions A and C satisfied
the criteria of Rahola, also if the reduction of GMt due
to the free surface in the tank was accounted for.
The position of the tank was chosen approximately
amidships taking up part of the bunker space between
the engine room and the fish hold. It extended over the
full breadth of the vessel, so b = B= 20.28 ft (6.18 m). The
length of the tank was restricted to 4.40 ft (1.34 m) in
accordance with the mentioned GMt values and the
criteria of Rahola. The values of s/b in table 1 show
rounded-off values following from an assumed height of
the tank 6.56 ft (2.00 m) above the base line.
Determination of water depth and discussion of the tank
effect
The choice of depth of water in the tank is governed by
the requirements of easy operation. It is important that
the captain of a small fishing vessel is not burdened by
such matters as adjusting the water level in the tank to
the momentary GMt value. Once it is filled to its pre-
scribed level in port it should be unnecessary to give it
any attention, except in emergencies.
In fig 10 the curves of p,a sin e, and na cos et are given
for the vertical tank position s/b= -0.150. These curves
were obtained by interpolation from the diagrams in the
figures. Although the ratio s/b varies slightly for the
three loading conditions, the mean value was sufficient
- 0.1x10
-2
0 0.25 0.5 rg- 0.75 ^ 10
Hg JO. Components of tank moment
ITH TANK EMPTY
WITH TANK IN
OPERATION
,h/b=OD6
(J sec'
1.5
2.0
Fig 11. Results of calculation
to determine the desired water depth for all conditions.
The appropriate quantities for these conditions are listed
in table 2.
• The reduced frequency w+Vb/g corresponding to
the natural frequency of the ship with an empty
tank
[165]
15
10
CONDITION! c
ITHJ^IK EMPTY
TANK. IN
OPRATION
Fig J2. Results of calculation
0.5 10 , 15
O sec'1
Fig 13. Results of calculation
2.0
• The water depth ratio (h/h)th which was derived
from the consideration that the theoretical
natural frequency of the tank and the ship should
be equal
• The water depth (h/b)0 which was derived from
fig 10 giving the largest sine component of the
moment at the stated reduced frequency
Evidently, as table 2 shows, the water depth for which
the largest damping effect at a given frequency was
obtained, was somewhat larger than the theoretical
value. To comply with the demand for simplicity, one
value of h/b must be chosen. In order to make a correct
choice, the effect of the tank on the amplitude charac-
teristic was calculated for all three loading conditions,
for their respective s/b ratios and for two water depths,
namely /?/£=0.06 and /?/£=0.08. The tank was assumed
to be filled with fresh water.
TABLE 2 : Reduced natural frequencies of the ship and water-depth
ratios under consideration
Condition
A
B
C
Item
-4 • •
0.925
0.762
0.856
(h/b)tn
0.087
0.059
0.074
(Mb). . .
0.094
0.070
0.082
The actual calculation is omitted from the paper. The
results are shown in fig 11, 12 and 13. Fig 11 represents
condition A. It was evident that with both depths the
tank gave considerable damping. Although the peak
amplitudes of both curves were approximately equal, the
largest water depth was to be preferred because, with the
peak occurring at a lower value of <o, the accelerations
of the vessel will be less. In fig 12 the results of the
calculation are shown for condition B. In this condition
the vessel was less stiff. The natural frequency of the
ship was considerably lower than that of the tank for
/7/£ = 0.08, which accounted for a marked peak in the
lower frequency range. Although the curve for /j//>~0.08
was certainly an improvement in comparison with the
original characteristic, the amplitude characteristic for
h/b =0.06 was better. For the third condition fig 13 shows
a result which was somewhere between the other two
conditions as was to be anticipated.
The main conclusion from these figures was that, in
spite of the different water depths in the tank and the
different loading conditions, the calculated amplitude
characteristics were all very similar and all show a rather
large improvement over the amplitude characteristics of
the ship without the tank operating. A sound choice was
h/b= 007, which gave a water depth of h= 0.07x20.28
= 1-42 ft (0.433 m). The total amount of water was
LxftxA=126.71 ft3 (3.586 m3). This was about 2 per
cent of the average displacement.
MODEL EXPERIMENTS
Purpose and performance
The large number of simplifications which had been
introduced in the course of the calculation procedure
required checking.
[166]
The tests were carried out with a 1 : 15 scale ship
model in which a roll oscillator and a recording gyro-
scope had been installed. In this model a tank was
installed with dimensions according to those mentioned
previously. Next, the model was ballasted and trimmed
so its stability and natural roll period corresponded to
the condition A specified in table I. By means of the roll
oscillator the model was subjected to a moment with a
sufficiently constant amplitude having any desired
frequency within the considered range. The gyroscope
served to measure the roll angles.
The following test scries were carried out with the
model with the tank empty, then filled to the level
corresponding with /*/& = 0.08:
• An oscillation test with the model subjected to
roll moments with a constant amplitude of 0.289
Ib.ft (0'04 kg.m) but with different frequencies
The object was firstly to determine an acceptable
value of v# for the ship with empty tank (the value
of v^ = 0.07 which was introduced in table 1),
and secondly, to furnish a comparison with the
calculated curve for the stabilized ship
• A similar test but with a larger moment amplitude,
namely, A/a = 0.434 Ib.ft (0.06 kg.m). The aim of
this was to obtain an impression of the degree of
the non-linearity of the system, both with and
without the tank in operation
• The third series consisted of experiments in
regular waves. The model was held at zero for-
ward speed and the waves on the beam, but was
free to roll, drift and heave. The wave dimensions
and roll angles were measured. From these
measurements the ratio between the rolling
amplitude and the wave slope amplitude has been
calculated as a function of the frequency [</>„/& £«((o)]
The purpose of this test scries was twofold.
Firstly, it should provide a comparison with the
results of the oscillation tests and with the cal-
culation from which it could be determined if the
motions of drift and heave did have a significant
influence on the performance of the stabilized
ship. Secondly, these measurements should form
the basis for comparison with the results obtained
in an irregular wave pattern
• The object of the fourth series was the measure-
ment and analysis of the model rolling motion
with zero forward speed in irregular beam seas. A
check on the correctness of the mathematical
assumptions in this particular case was provided
by a comparison between the experimentally
determined spectrum of the rolling motion and the
spectrum calculated from both the results of tests
in regular waves and the measured spectrum of the
waves
The results
In fig 14 the results of the first series of tests are shown.
The measured and calculated amplitude characteristics
for the ship without the tank closely resemble each other.
The curves with the tank in operation differ. The cal-
culated curve appears to be a mean of the experimental
curve. The curve of measured roll amplitudes, presented
15
g
10-
5-
CONDITION A
:UH TANK EMPTY
EXPERIMENT WITH
Ma=0289ft.lbs
CALCULATED
ACCJQRDJNG TO
LINEAR
EQUATION OF
MOTION
CALCULATED CURVE
FOR h/tu008
TANK IN
IOPERATION
EXPERIMENT
WITH MgS
"Q289ftlbs
0.5
10
0) sec'
15
20
14. Results of oscillation texts compared with calculated curves
10
CONDITION A
HWITH TANK EMPTY
^EXPERIMENT WITH
LMa=0.2$9ft,Lbs
EXPERIMENT WITH
CALCULATED CURVE
FOR h/bsO.08
TANK IN
OPERATION
EXPERIMENT
WITH:
l89fUbs
'0434ft
IDs
0 0.5 1.0 ,15 20
CO sec'1 —
Fig 15. Results of oscillation tests for different moment amplitude*
in dimensionless form, shows two pronounced secondary
peaks. The reason for this discrepancy is the non-
linearity of the tank moment. The dimensionless pre-
sentation obscures the fact that the measured values
[167]
were all considerably lower than the 0.1 radians (5.7°)
which was the basis of the calculation. For such small
amplitudes the curve of e, versus the frequency is much
steeper than for an amplitude of 0.1 radians, which
results in a greater damping in the neighbourhood of
the tank's natural frequency and a less damping else-
where. These differences are not of practical importance
as the measured values are small.
In fig 15 the results for the largest moment amplitudes
are shown. The amplitude characteristic for the ship
without the tank is lower than in the previous case,
indicating that the damping coefficient increases with in-
creasing amplitude. The curve for the stabilized ship
shows the same tendency as has been described in the
l10
CONDITION A
^CALCULATED
(I .MAGNIFICATION
FACTOR
CALCULATED
[MAGNIFICATION
FACTOR FOR h/b
TANK IN
OPERATION
!\MEASURED
k
(i) sec
Fig 16. Results of tests in regular waves
former section but to a lesser degree. For the larger
(but still small) rolling angles, the measured values for
the largest moment amplitudes show the least deviation
from the calculated curve.
In fig 16 the results of the tests in regular waves are
given. The non-dimensional roll amplitude curve for
the unstabilized ship seems to be shifted somewhat when
compared with the previously determined amplitude
characteristics, and the peak is considerably reduced.
This last point is undoubtedly partly due to the larger
rolling angles, for the deck entered the water; and
probably there is also a decrease of the wave moment
due to the orbital motion mentioned earlier.
It is possible that part of this larger damping and
probably the slight shift of the curve are caused by the
coupling of the rolling motion and other motions; i.e.
sway and heave. This, however, is not yet clear. In any
case, this appears to be of no practical significance as is
shown by the good agreement between the measured
and the originally calculated values, for the stabilized
ship.
Before considering the next figures some quantities
have to be defined. The roll angles in regular waves are
given as ratios to the wave slope. Therefore, the spectral
density of the irregular wave pattern is presented by a
wave slope spectrum which is defined by:
G>4
Skti(co) do> = — Sc(o>) dco
J7
The average value of the highest third part of the
observed amplitudes of a random fluctuating quantity,
say the roll angle, is often called the significant ampli-
^CALCULATED
| [FROM; RESPONSE
LTD REGULAR.
, 1WAYES
CONDITION A
EXCLUSIVE TANK
I'ig 17. Comparison of calculated and measured roll spectra for the
ship alone
tude. The significant roll amplitude can be regarded as a
measure of the impression the amplitude of the rolling
motion makes on the observer. For a stationary time
series and a spectrum of small width this quantity can
be calculated from the expression :
where :
Wn
In fig 17 the wave slope spectrum is shown with two
roll spectra, one measured, one calculated from the
experimental results in regular waves with the tank not
operational. The agreement is good, as regards the
significant roll amplitudes and the frequency range.
In fig 18 the spectra for the model with the tank in
operation are shown. One spectrum is measured, another
[168]
is calculated from the results in regular waves, and a
third is calculated from the originally computed response
shown in fig 14. The agreement is good.
A comparison of the significant roll angles for the
stabilized and the unstabilized ship reveals that an overall
reduction of 50 per cent is achieved in this wave spectrum.
240
.CONDITION A
INCLUSIVE TANK.
*
I
160
80
S^CALCUUATED FR0Mi RESPONSE. _L. .._
•I TO REGULAR WAfYELS 9m*h**** \
,SM CALCULATED F80K
COMPUTED.
U) sec:
Fig 18. Comparison of calculated and measured roll spectra for the
ship with tank
SUGGESTIONS
Bilge keels
As has been mentioned, the omission of bilge keels is
not advised. There are two reasons for this. The first and
most important is that there can be emergency situations
(i.e. icing up) when it will be necessary to empty the
tank because of its negative influence on the statical
stability. If no bilge keels are fitted it will leave the ship
with extremely low roll damping.
The other reason is that the non-linear effect of the
tank is somewhat neutralized by the bilge keels. When the
motion amplitudes become large because of bad sea
conditions the tank moment is not so effective. The
damping of bilge keels, on the contrary, increases con-
siderably with increasing motions.
Dimensioning the tank
In the foregoing pages little is said about the amount of
water a roll damping tank of this type should contain.
In this case it was about 2 per cent of the displacement
which is certainly not an insignificant amount. An
overall reduction of 50 per cent was achieved but it
depends on the sea conditions what this reduction will
be. It is dependent on many factors, which roll amplitudes
and roll accelerations are found acceptable, and it is
very difficult to define a basic criterion. The ultimate
answer can only be found by experience. It is the author's
opinion that it does not pay to economize too much on
the dimensions of the anti-rolling tank, especially if one
has a free hand during the design stage of the vessel.
Position of the tank
If an anti-rolling tank is wanted, one has to provide
space for it where it will work efficiently, and the same
remarks hold as for the dimensioning of the tank.
Obstructions in the tank
It is not always possible to avoid placing stiffeners in
the tank side. If the obstruction is small, say the stiffener
height is not more than about 10 per cent of the tank
length, the influence, as has been shown by tests, is not
serious.
CONCLUSION
A fret surface tank of the type presented here, that is a
rectangular tank with flush front and rear bulkheads and
bottom, can provide an efficient means of roll damping.
Its simplicity of installation, ease of maintenance and
reliability makes it especially attractive for small vessels.
Nomenclature
b Breadth of the tank measured athwartships
Dt Depth of the tank
/ Magnification factor
jfy Magnification factor at the natural frequency of
roll
h Depth of water in the tank measured from the
water surface at rest to the bottom of the tank
1$ Virtual mass moment of inertia of roll
k+ Virtual radius of gyration of roll
/ Length of the tank measured in fore and aft
direction
M Moment produced by the anti-rolling tank
Ma Moment amplitude produced by the anti-rolling
tank
mQ^ The integral of the roll spectrum over the
frequency from zero to infinity
N+ Damping coefficient of rolling
RQ Stiffness coefficient of rolling
Sfcc(w) Spectral density of wave slope
Sj(a)) Spectral density of roll
s Vertical distance of the axis of rotation to the
bottom of the anti-rolling tank
Tt Theoretical natural period of the water motion
in the anti-rolling tank
et Phase angle between the rolling motion and the
tank moment
$«i/3 Significant roll amplitude
p. Non-dimensional tank moment
/tfl Non-dimensional tank moment amplitude
v^ Non-dimensional damping coefficient of roll
CD, Theoretical natural frequency of the water
motion in the tank
pt Mass density of the tank fluid
[169]
Catamarans as Commercial
Fishing Vessels
by Frank R. MacLear
L'emploi des catamarans pour la peche commerciale
Les catamarans offrent dcs possibilites intdressantes pour la peche
commerciale, pour les raisons ci-apres: (a) Plate-forme de travail de
grandes dimensions; (b) Possibilit6 de lever des charges sans
•entralner pour le bailment d'inclinaison transversale ou longi-
tudinale importante; (c) Possibility si besoin est, de se maintenir a
la meme place; (d) Souplesse en maticre de tirant d'eau, celui-ci
pouvant au choix etrc trcs grand ou tres faible; (e) Grande ma-
noeuvrabilitfc due £ Fecartement des helices, qui peuvent se trouver
6loign6es Tune dc I'autre d'unc distance supeiieure a la largeur
totale des bailments comparables £ une seulc coque.
Los catamaranes como embarcaciones comerciales de pesca
Los catamaranes tienen grandes condiciones como embarcaciones
comerciales de pesca debido a que poseen las caracteristicas
siguientes: (a) Plataforma de scrvicio grande; (b) Capacidad de
elevacidn de peso con escora o angulos de trimado minimos; (c)
Capacidad para mantener unacstaci6n si se desea; (d) Flexibilidad
de calado. El calado se puede hacer muy profundo o muy super-
ficial, segun se desee; (e) Maniobrabilidad debido a la gran separa-
ci6n de las helices. Las helices pueden estar mas separadas que la
manga total de las embarcaciones comparables de casco sencillo.
DURING the last century there were very few
power catamarans and these were primarily
designed, built and operated as ferry boats or
personnel transport for relatively short distances. Only
very recently has a power catamaran been specifically
built for commercial fishing. In spite of this, catamarans
show promise as commercial fishing boats.
ADVANTAGES
Large working platform
The large beam, running the length of the vessel, provides
a large working deck for easy handling of fish and gear.
The beam can Ije 33 per cent greater and the deck area
about 35 per cent more than a single-hulled vessel of
similar length. The additional construction costs should
not be in excess of 35 per cent.
Weight-lifting ability
Large weights may be hauled aboard with minimum
heeling or trimming angle. The above-mentioned
beam provides phenomenal stability and permits the
raising of large weights over the side, stern, bows or
through a well between the hulls. A large oil-drilling
catamaran has been built for service in the Gulf of
Mexico which is said to be able to handle the large
drilling rigs down between the hulls in a way previously
impractical for single-hulled vessels. The stability and
small rolling angle is said to be of great advantage. The
same qualities that make this boat desirable as an oil-
drilling platform should be advantageous for fishing.
Draft flexibility
The draft can be varied as desired because the stability
is not dependent on the individual hull form, but rather
the distance between the two hulls. Therefore an extremely
shallow draft can be obtained if required, by giving each
hull a hard chine and flat bottom with relatively generous
beam. Should a deep draft be beneficial for station
holding, deep narrow hulls would prevent lateral drift.
This deep form would in addition ease the roll by in-
creasing the period of roll. The depth to beam ratio
should not be too excessive because it can result in
excessive wetted surface and pitching. A deep narrow
catamaran hull permits a wider tunnel between the hulls
with less drag than a catamaran with too small a distance
between the hulls.
Station holding
The flexibility of draft could create a boat that would
hold station excellently and not be blown about by the
wind, as just explained in the previous paragraph.
Manoeuvrability
The widely-spaced screws provide excellent manoeuvra-
bility, either at sea or in congested harbours. A 52-ft
(15.8-m) catamaran yacht when in Dutch inland water-
ways was particularly manoeuvrable and could reverse
into very restricted spaces. Her two propellers were
18 ft (5.5 m) apart, allowing the craft to turn in her own
diagonal length with great precision. This would be very
advantageous for fishing vessels.
Compartmentation and safety
A catamaran is easier to subdivide than a single-hulled
craft because the two separate hulls can be bulkheaded
to reduce the floodable volume of compartments and
increasing safety.
Reachability
Beaching is easy because stability is not lost when bows
ground as in a single-hulled boat with one point contact.
Except in excessive surf, beaching is simple, permitting
a greater flexibility of operations, including cleaning
and even repainting the bottom.
Stern ramps
Stern ramps can be incorporated that can be raised for
conversion from a stern to a side trawler.
[170]
HISTORY
Catamarans and their outrigger cousins have been used
for thousands of years in the Pacific Islands and have
proved their seaworthiness as fishing vessels and personnel
transports, having high speed and surprisingly good
seakeeping qualities. These craft were either sailed or
paddled and often equipped for both. Powered cata-
marans are a new innovation and, although tried in the
very early days of steam engines, there have been
relatively few compared with single-hulled power craft.
It is difficult to find twenty or even ten successful
powered catamarans.
STRUCTURE
A sufficiently strong catamaran can be built to withstand
storms at sea, if properly designed. Two 52-ft (15.8-m)
catamarans, one of aluminium, the other of wooden
construction, have made offshore voyages from the
Virgin Islands to New York City without showing any
signs of fatigue. Both are twin-screwed diesels also
fitted with sails as yachts. The rigs in the boats only add
to the strain placed on the hulls and they certainly could
be converted to fishing vessels without any loss of sea-
keeping ability. One was used for sport fishing in the
Caribbean and all agreed that the 21 -ft (6.4-m) beam at
the stern was excellent for fishing on a boat only 52 ft
(15.8 m) long. Amateur built catamarans and trimarans
have crossed both the Atlantic and Pacific and it is
strongly felt that professionally built multi-hulled boats
are safe and need only prove their economic value to
become successful.
COMFORT AND MOTION
Head seas
In head seas, power catamarans have no great advantage.
If the wing (the structure connecting the two hulls) is
not high enough the operator will have to reduce speed
to avoid undue pounding under the wing. In the design
stage every precaution must be taken to ensure the
connecting structure between the hulls has sufficient
height above the waterlevel throughout its length and
particularly near the bow. The "wing" is so named be-
cause the longitudinal section is somewhat similar to an
aeroplane wing. The pitching motion, if anything, is
shorter and less comfortable than a single-hulled vessel.
Spray protection for the bridge can be improved if the
wing is extended far enough forward.
Seas at 45° on the weather bow
As soon as the catamaran turns 10 to 30° from head seas,
the motion greatly improves. The angle effectively
increases the length of the boat because the distance
from the weather bow to the lee stern is greater. Seas at
45° to the bow are acceptable and the 40-ft (12.2-m)
catamarans at Waikiki Beach in Hawaii go out through
breaking surf at this angle.
Beam seas
Beam seas are no problem unless the wave length is
exactly twice the distance between the centrelines of the
two hulls. In this condition, the most violent rolling
occurs because one hull is on the crest while the other
is in the trough, but the angle will seldom exceed the
surface angle of the sea. This seldom occurs, but a
change in course by 10 or 15° either "up" or "off"
greatly alleviates the situation because waves lift the
bow or the stern before the rest of the hull, in a longer
and smoother fashion than a direct beam sea.
Quartering seas
While this is often the very worst condition for a single-
hulled vessel, it poses far less problems to a well-de-
signed catamaran. A good powered catamaran shows no
tendencies to broach and does not roll outboard to a
greater angle than the slope of the wave. Catamarans
can come in through surf where no other vessel can
survive. This is well proved in the Hawaiian Islands
where sailing catamarans and paddled outriggers
operate through surf most of the year. This has been
done for centuries by Hawaiians and in the past 15
years with many thousands of tourists on board.
Seas dead astern
Seas dead astern are of even less concern to the catamaran
than quartering seas and operators have reported there
is no tendency to broach or to get into cumulative rolling
whatsoever.
Comfort
There is a difference of opinion when considering the
comfort of catamarans compared with that of single-
hulled vessels. On a powered catamaran with ten people
aboard, seven thought the catamaran was more com-
fortable and the other three did not like the motion.
Under somewhat different conditions, all ten would agree
that the catamarans were more comfortable. Under
certain very exceptional conditions, such as were men-
tioned previously, all ten might say the motion is too
quick and have difficulty keeping their footing.
On power-driven catamarans of 70 ft (21.3 m), 57 ft
(17.4 m), 45 ft (13.7 m) and 37 ft (11.3 m) at least 80
per cent of the people aboard thought the motion with
the sea at 45° to the bow was substantially more com-
fortable and permitted greater workability on deck than a
comparable single-hulled powered boat. (Five per cent
of the minority thought the motion was not as comfort-
able.) To generalize, most people like the motion of
catamarans better most of the time.
REPORT OF VARIOUS EXISTING
CATAMARANS
Tropic Rover
This 140-ft (42.7-m) catamaran was designed, built and
operated for quite a few years by Captain Sidney Harts-
home. He made the bows quite full because he feared
bow burying but after several years of operation this
proved unfounded and he said he would make the next
catamaran somewhat finer since his craft showed no
signs of bow burying even when seas lifted her stern.
Tropic Rover is a tourist trade vessel and trips are of
one to two weeks' duration. Built of plywood, her struc-
[171]
tural integrity never worried her owner. She has crossed
the Gulf Stream at the Straits of Florida many times and
took most of her cruises in Bahamian waters with
persons who were not used to the sea.
US Johnson
This is a 45-ft (13.7-m) aluminium catamaran owned and
operated by the U.S. Army Engineers as a work boat for
hydrographic surveys of the Great Lakes of U.S.A. It was
designed by MacLear and Harris and built by Marinette
Marine Corporation, Marinette, Wisconsin. She re-
placed small survey vessels which had to be loaded and
off-loaded by a large mother ship and has been in opera-
tion for three years. The vessel is self sufficient and is
used for shallow-water surveys, making passes straight
on and off the beach while taking soundings. Her draft
is only 3 ft (0.9 m) and grounding is not harmful to her
because of her underwater hydrojet propulsion. With two
6-cylinder dieseis, she has a top speed of about 13 mph
(11.3 knots) and is exceptionally manoeuvrable.
Margay
This 52-ft (15.9-m) twin-screw double planked mahogany
over oak frames diesel catamaran, has operated in the
North Sea and English Channel as a yacht and has
cruised from Venezuela through the Caribbean Islands
to Florida. She is equipped with sport-fishing equipment.
Stranger
This 52-ft (15.9-m) twin-screw aluminium catamaran,
owned by Robert C. Graham of New York City, has
gone from New York to the Virgin Islands and returned
with extensive chartering. Her skipper, Peter Van-
dersloot, an experienced charter skipper who has been on
single-hulled vessels previously, stated that the vessel
does 18 knots in following seas with absolutely no
tendency to broach while surfing down seas for one or two
minutes at a time. The vessel is spacious and has excellent
accommodation with an exceptional amount of stowage
space and deck area. The two dieseis produce a cruising
speed of 9 knots.
Incredible I, Incredible II
These are two small powered catamarans of "W'-bottom
shape. Each hull is a very sharp Vee shape that would
have an excessive deadrise for a single huller but can be
used in a catamaran. These relatively small craft of 15-ft
(4.6-m) and 25-ft (7.6-m) length are only mentioned
because they are the softest riding fast boats of their
kind that either the author or their owner, Mr. Harold T.
White, Jr., have ever encountered. The boats operate at
30 to 40 knots in very rough water and while motion is
somewhat short, it is far softer and easier than compar-
able boats or even boats twice their size. This is attributed
to the very fine high deadrise hulls which absorb shock
better than single-hulled vessels. They can operate faster
in very much rougher water than any existing hydrofoils
of their size or cost. A commercial fisherman could use
them for transportation from one fishing vessel to another
if helicopters were not available or too expensive.
Caribbean Twin, fig 1 and 2
This twin-hulled craft of Keasbey, New Jersey, is the only
one of its kind known to the author which was specifically
designed and built in recent years as a commercial
fishing boat. Her particulars are shown in table 1. This
craft was built by the Twin Hull Boat Company at
Keasbey Shipbuilding and Storage Yard at Keasbey,
Fig J. Caribbean Twin— general view
New Jersey, and owned by William W. Bucher. Entirely
of steel, she will be engaged in commercial fishing,
including shrimping in Florida waters. The stern ramp
can be raised for use either as a stern or side trawler.
The rolling angle is far less than a single-hulled vessel
and the deck area is substantially greater. The craft can
be beached for scraping of the bottom and painting, thus
reducing time and cost at shipyards. She could easily
TABLE 1. Caribbean Twin — particulars
Loa
Beam
Draft (loaded)
Draft (light)
Depth of hull
Engine
Generator
Reduction ratio
Ice
Fish hold insulation
70ft (21.3 m)
28 ft ( 8.56 m)
7 ft 6 in ( 2.29 m)
5 ft 6 in ( 1.68 m)
9 ft ( 2.75 m)
2 x 350 hp diesel
(228 hp continuous rating)
)OkW diesel
4.5 to 1
30 tons
6 in (150 mm)
styrofoam
Beam of each hull
Fish holds
Capacity holds
Speed
Propeller diameter
Propeller pitch
Shaft diameter
Fuel capacity
Fresh-water capacity
10 ft (3.05 m)
3,500 ft3 (100 m3)
60 tons
12 knots
48 in (1,220 mm)
44 in (1,1 15 mm)
3 in (76 mm) bronze
11, 800 Imp gal
(14,009 gal, 53,0001)
1,000 Imp gal
(1,200 gal, 4,6001)
[172]
Fig 2. The stern ramp lowered
be rigged with twelve bunks for scalloping or oceano-
graphic work, providing pleasant crew accommodation.
Although this craft has twice as many diesel engines
as the conventional fishing boat of her length, the
operators maintain that this is an advantage because of
the reliability of a second engine and the exceptional
manoeuvrability. Her earning capacity is large enough
to offset the added cost and maintenance of a second
diesel engine. The main advantage of this craft is the ease
of convertibility from one type of fishing method to
another. The cargo capacity is 20 per cent greater than
a single-hull trawler of equivalent length or cargo
capacity equal to a single-hulled craft 10 ft longer.
The cost was 15 per cent more than a single-hulled
craft but this was primarily because of the additional
engine. The builders were well satisfied and are now
building an 81 -footer (24.7 m) with the capacity and
cost of a 91-ft (27.8-m) conventional vessel. The quarters
are above deck and the fishermen find this far better
than the conventional accommodation in the forepeak
(fig 3). The living space is 50 per cent greater than an
equal length single-hulled vessel. The net tonnage is
20 per cent greater, giving approximately 20 per cent
more volume below decks. The insurance is less than
that of a wooden vessel and is further reduced by the
fact that she has twin screws.
Some fish boat operators believe that they can almost
double the size of their nets with the large stern deck
area and buoyancy of this particular catamaran (fig 4).
The adaptability is particularly important to investors.
If the commercial value of one type of fish should fall,
it would be easy quickly to convert to some other type of
fishing because of the large unobstructed deck aft.
The deck house causes no obstruction. The two hyd-
raulic cranes on the stern can be used for fishing or
alternately used to anchor by the stern during the day
while waiting for an evening catch of shrimp.
SUMMARY
It should not be construed from this paper that the cata-
maran fishing vessel will completely replace all other
commercial fishing craft, for that is not the intention.
On the other hand, the possibilities of this type of craft
should be investigated since it is believed that it has
certain features that could be advantageous to certain
fishing boat operators. How good catamarans are as
Fig 3. An impressive how view
[173]
commercial fishing vessels can only be decided by
experience and time. All that can be done is to discuss
their potential in the hope that there will be enough
people who are experimentally-minded and would be
willing to try catamarans to prove their advantages
and bring to light some other important features that
might potentially make them more productive with
larger earning capacity than other types of fishing boats.
Fig 4. The after deck with the ramp in the raised position. The twin hydraulic cranes can be used either for
fishing or for anchoring by the stern
[174]
U1SCUSS10I1 1 How knowledge of performance
influences the design of fishing craft
VALUE OF FULL-SCALE MEASUREMENT
Sainsbury (Canada): Hatfield's paper is very welcome for its
quantitative data, something which is regrettably too rare in
the field of the smaller fishing vessel. Although data emerging
from experiments such as these is invaluable to the naval
architect, one must not forget a very practical result which
comes out of the actual conduct of the tests and the taking of
measurements: that is the greater understanding by the boat
operator, the fisherman, of his boat.
In Newfoundland, they had recently embarked on a series
of trials with a number of fishing vessels varying in size from
35 to 65ft (10.5 to 20m). Until now no measurements or
trials had been made with the craft, and calculations in the
design stage had been omitted, so that practical performance
and stability was not available. The present work was started
with the intention of obtaining the basic performance charac-
teristics in terms of speed, fuel consumption, etc., together
with practical stability tests, weights, working displacement.
While the data now being gathered is invaluable in improving
the boats technically, the actual trials and measurements have
aroused far more interest among the practising fishermen
than could ever have been expected. Not only the owners of
the boats, but the majority of fishermen in the area now have
a much better understanding of their boats* capability, and
this is a result certainly as important as the actual technical
data itself.
In both the developed and developing countries, naval
architects often feel that the fisherman who uses the boat does
not always do so as efficiently as might be, because he does
not understand some of the basic principles, e.g. power,
speed, propellers. Much of this is their own fault as the facts
can be demonstrated very simply by going on board, taking
a few measurements, and explaining the reason for them and
the meaning of the results. This docs not require any com-
plicated equipment and in Newfoundland owners are now
queuing up to have their boats tested, and are extremely quick
to grasp the meaning behind it.
Sainsbury felt very strongly that this "side effect" of small
boat trials could be exploited much more, as to a large
extent the boat is only as efficient as the operator, and this, in
many cases creates a barrier to rapid improvements in
design.
Leathard (UK): The question of matching propellers is
touched upon by Hatficld. In the UK Leathard had often
found a lack of understanding of what may be achieved with
a fixed pitch propeller. It may be designed to absorb given
power at given revolutions at only one forward speed of the
ship; this chosen speed may be anywhere between zero and
the maximum attainable. Assuming that it is at some inter-
mediate position, a reduction, such as may occur when a
trawler is fishing, will cause the engine revolutions to fall off,
the torque being held constant by the fuel rack setting on the
engine: an increase will cause the torque to fall off, the rpm
being held constant by the governor setting on the engine.
The situation is represented diagrammatically below:
torque falling
rpm fulling
.§> rpm constant
0
Speed
Max
In the normal free-running design, the chosen speed is at
the extreme right of the diagram. Leathard had often heard
of high engine exhaust temperatures when trawling, suggest-
ing overload torque conditions on the engine necessary to
achieve the required power and pull, and he suggested that
there is a good case for designing a trawler propeller so that
it absorbs full power when trawling. Some sacrifice in free-
running speed has to be accepted, but it may be lessened by
allowing an increase in rpm in this condition. The propellers
for trawlers designed in this way produce no reports of high
engine temperatures when trawling. Compared with previous
vessels of a similar type, there is a loss in free-running speed
of about half a knot on about 5 per cent overspeed in engine
rpm. Incidentally, an approach to design along these lines
would have automatically reduced the free speed of the two
vessels in Hatfield's paper by a quarter of a knot or so, giving
his proposed saving in fuel consumption.
Real contribution
Dickson (FAG): Hatfield's paper is a real contribution to the
understanding of the job that fishing boats, their engines
and their deck machinery must be designed to do. The very
low apparent propulsive efficiency while the seine net is being
towed is not a reflection on the propulsive system, because
in this method of seining -fly dragging as it is called— the
boat is more or less at bollard with the winch fighting against
the propeller and at zero headway the apparent propulsive
efficiency would be zero. Dickson used to sail on an old
underpowered seiner with only three winch speeds and it
actually used to go astern when the winch was put into top
gear. Hatfield's fig 1 8 and 1 9 show very clearly the advantage
of a six-geared winch, where in the final stages of hauling the
engine speed can be slowed down to give the fixed pitch
propeller less thrust, at the same time as the ropes are speeded
up to bring them in more quickly.
Hatfield stated that the mean warp loads are little affected
by variations in the type of bottom. This is true enough in
the sense that mean warp load is determined by propeller
thrust more than by anything else so long as the net does not
snag. If one warp is on catchy stones or sticky mud while
the other is running on clean sand, one soon notices the
difference in load between the two. The sort of stony ground
that a seine net will come across is very limited and the
skipper will then shoot very little cross rope, or second leg,
so that the net will close quickly and keep coming, for it is
only so long as it keeps coming that propeller thrust and
mean warp tension are matched. As soon as the net sticks,
[175]
the momentum of the ship, even if only making a fraction of
a knot headway, causes the warp tension to rise rapidly.
There are few seconds in which to stop the winch and reverse
the propeller. Another factor that affects warp tension is
windage and on a boat of this 70ft (21 m) size db 3 cwt
(±150 kg) for a 20 knot, force 5 wind can be added or sub-
tracted dependant on whether it is astern or ahead. A stern
wind and the pitching caused by a following sea can in
themselves bring the ropes to breaking point on a big seiner.
The limits of weather in which a seiner can work its gear
are not set by the safety of the ship as is sometimes the case
on a small trawler, a seiner's gear can part all too easily.
Seining is much less hard on the boat than trawling, by
virtue of the manilla rather than the steel warp, by the lower
ship speeds during towing and partly because less engine
power is required. The Rosebloom so far as Dickson recalled
from discussions with her skipper works on fairly good
trawling ground. Tt is however shallow water and rough
ground trawling that impose the severest stresses, for then
when the gear snags on the bottom the whole momentum
is taken off the ship quickly, because the warps in shallow
water are short and have not enough sag in them to give much
spring. In this kind of trawling one hits snags often enough,
and the fisherman's reaction to this is to use heavier warp in
rough ground trawling and this increases the possibilities of
damage. One wooden boat Dickson fished in was twisted and
strained after a year or two of such work and she had to be
strengthened. She is about the same size and type as the two
described in Hatfield's paper.
The virtue of a paper like Hatfield's and research develop-
ment work of this sort is that it gives a measure of the effect
of the fishing method on the ship. This will lead not only to
improved ship design but also to improved fishing methods.
With instruments to give fair warning of excess loads, with
past records to show as examples, the subject becomes
teachable as an item of fishermen's training and training is
the key to fisheries development.
Corlett (UK): Much more quantitative work is required in
this field of small fishing vessels and Hatfield is to be con-
gratulated on some very interesting work. Turning to detailed
points in the paper Corlett was, contrary to Hatfield, rather
surprised at the small amount of propeller mis-match actually
noted; this is much less than that sometimes seen. The pitch
of the propeller of Opportune II is quite acceptable for work-
ing conditions, but in this respect controllable pitch pro-
pellers are very helpful for this type of vessel and the flexibility
obtained is much greater than with a fixed propeller. Corlett
could not really understand the lack of use of controllable
pitch propellers on motor fishing vessels in Britain.
Alternatively nozzle rudders, which also have a direct
effect upon rough water performance, can be considered and
give a significant increase in propeller flexibility as against
open screws. Admittedly it is not easy to fit nozzle rudders
into the stern apertures of some existing motor fishing vessels,
especially wood construction, but there is no fundamental
difficulty in this with new vessels. Indeed with existing
vessels it might well pay to do this, even though modifications
have to be made, because of the significant increase in work
capability that can be produced in an existing boat with an
existing engine. Indeed this can be a method of upgrading
the existing ships.
Author's reply
Hatfield (UK): The design of propeller in the UK for fishing
vessels usually comes to a compromise between the cruising
requirement and the fishing requirement, but with the bias
heavily in favour of cruising. This is natural because a good
"cruising" propeller immediately pleases the owner by giving
a high ship speed. However, a propeller designed to suit the
fishing condition is more profitable overall, and it is good to
hear that this is being done.
Hatfield agreed with Corlett on the almost complete
absence of controllable pitch propellers in the UK fleet;
there is a strong reaction against them on the part of the
operators which seems to be based principally on suspected
unreliability.
Hatfield did not like quoting weather conditions in reports
of this kind except as auxiliary information. The external
conditions which the ship and its machinery are aware of are
wind, speed and direction, and wave configuration. It is well
known that a ship can be in almost flat calm in a force 7 in
some waters, but pitching and rolling violently in a force 2
in others. Thus Hatfield preferred to quote wind, speed and
direction, and angle of pitch and roll. In fact, the weather
throughout the fishing trials of Opportune II was force 2 to 6
and at the time of his table 8 was about force 5.
SURVEY OF TRADITIONAL JAPANESE BOATS
Foussat (France): Could Yokoyama indicate whether he had
undertaken tests on the flow pattern on hulls with sharp
bilges? The flow pattern varies with the angle of entrance.
Similarly, with the same displacement and same form for the
curve of water plane areas, it is possible to design a hull
offering minimum resistance, by modifying the form of the
angle for speed and trim (given, or variable corresponding to
experimentally-obtained values), Has Yokoyama conducted
any research on this point?
Selman (UK): Selman thought everyone would admit that
straight-framed boats are more easily built than the more
conventional round-bilged types, but he had yet to be con-
vinced that they can be more economically propelled. Although
M-7 has less resistance than the best and most comparable
M-61, the latter has a displacement length ratio some 49
per cent larger so that on the balance Selman made the
round bilge form 20 per cent less resistful for the same dis-
placement. He regarded the comparison of rough weather
tests useless because one model was self-propelled and the
other towed.
Coming now to fig 5 of Yokoyama's paper Selman would
considerably modify the curve of wake as shown in that
diagram. Jf the lowest spot is ignored or omitted as has the
corresponding spot for thrust deduction and also the third
spot, it is then possible to draw a curve similar in shape to
that already drawn for thrust deduction. The two curves
would follow one another and have similar characteristics as
one would normally expect. The propulsive efficiency curve
would remain unaltered as would that for the open propeller,
but both the hull efficiency and relative rotative efficiency
curves would have the same characteristics and markedly
different values at low speeds.
Selman found it difficult to believe the low wake values
quoted for this M-7 form and believed such low values could
be caused by a breakdown in flow due to the proximity of the
propeller tips to the surface at the transom. Indeed some
confirmation of this may be found in the fact that fig 6 shows
higher values of wake for deeper immersions: for L-7 as
compared with L-12. Selman had often found a pronounced
suction at such transoms, particularly at the centreline, and
he believed that the propeller in this instance is sucking down
air from vortices formed at the surface. The effect being to
increase revolutions required to give the required thrust in
the model propelled condition and so producing an apparent
small and negative wake.
[176]
Selman concluded that he was in his 70th year and speaking
for himself would certainly require more than one wife to
assist him manage to beach a 50ft (15 m) or even a 30ft
(9 m) boat, as referred to by Yokoyama and his associates in
their paper!
Kilgore (USA): Yokoyama et al have presented curves
showing significant improvement in longitudinal motions of
hard-chined craft of high midship section coefficient over
"European types". The value of the paper would be en-
hanced if the authors would show specifically what they mean
by "European types". Also the value of their observations
would be greater if they would not only supply the geometrical
specifics of the models compared, but also information as to
whether or not the mass distribution was the same.
Interesting development
Corlett (UK): It is most interesting to see how an entire
range of fishing vessels has developed owing nothing to
Western type practice. The statement that aged couples can
haul 30 ft (9 m) fishing boats up the beach indicates that
aged Japanese couples must be exceptionally vigorous.
Turning to the details of the various ships, Corlett agreed
with the model test results for Japanese type M-7, namely a
flat trend to the resistance curve at high Froude numbers. This
is fundamentally obtained by a fairly flat run and energy
recovery from the wave system. Corlett had found it possible
to do just this and to obtain significantly higher speeds on a
given length of hull than conventional form, although often
the resistance of this type of vessel has been slightly higher
at low Froude numbers. At the same time, the actual horse-
powers are important and the slight increase of Cr at low
Froude numbers possibly represents 5 to 6 hp, whereas the
saving obtained with this type of form at high Froude num-
bers may be of the order of 100 hp or more. Equally it is
found that this type of form has good pitching characteristics
and this is borne out by the Japanese experience in the paper.
Furthermore, with an aft fishing platform as is common
nowadays in these small ships, a far aft pitching centre is
desirable in association with highly damped characteristics
at the bow in pitch. A form such as M-7 gives this although
Corlett had found that it may be advantageous to use a full
angle of entrance and to shape the forward sections very
carefully to obtain the highest possible degree of damping at
small pitch angles. Nozzle rudders help in this respect,
moving the pitching centre aft and damping the stern, It
cannot be emphasized too strongly that in a small vessel
with men working al and over the stern, everything possible
must be done to prevent movement at this end.
Turning to the propulsive efficiency of these Japanese
fishing boat hulls, it is clear that they are low mainly due to
relatively high thrust deduction and relatively low wake
fraction, This is, of course, to be expected with the rather
clumsy wooden sternpost fitted and Corlett would suggest
that the possibility exists of using prefabricated steel stern-
frames specially adapted to mate up with the wood structure
and which would give the opportunity of a cleaner ending to
the skeg. At the same time the low wake fraction is basically
because most of the wake around the hull goes up the buttock
flow stern and is not shed into the propeller. This, of course,
Typy
Of
ahip
Model
NO.
Name
of
ship
Kind
of
ship
Model
length
ft (m)
A
• LPP/
'i
Lpp
ft (m)
LwL
ft (m)
B
ft (m)
Tm
ft (m)
A
t
Cb
for
I.wl
cr
for
hwl
Cm
^}
'u
u,
'T
Is)'
Ij
ft- (m- )
Japa-
nese
7-U)
Jinsui-
maru
Exp.
boat
6.56
ir.oo)
4.050
26.60
(8.10)
L'4.00
(7.30)
6.75
(?.06)
1.31
(0.40)
2.37
0.461
o.5»'.'
0. 7«3
3.r>4
6. (.3
5.95
147.!-0
(13.75)
11
7-U)
'»
ii
It
»
»
2r>,20
(7.70)
"
1.94
I'-1. 59)
4.59
0.541
0.62r>
O.Mf>6
3.74
4.07
9.76
IVj.i'O
(17.0.-)
Round
61-U)
Nigatft-
maru
Small
trnw-
5.oo
11.52)
10.050
50.20
(an. 32)
50.00
(15.16)
12.40
(3.70)
4*14
(1.26)
31.53
0.477
o. 58?
O.UPO
4.01
3.40
M.Hfi
W.M
U.4.40)
ler
.
it
61-U')
"
H
»
n
»
49.20
(14.99)
n
3.34
(1.02)
21.43
0.424
0.556
o. ?<•>:•
3.97
4. 34
(>.-<' \
'-74.00
(M.4'lj
1 . .._
. .. „
"
61-13)
H
H
'•
M
n
413.50
U4.7W)
"
2.98
(0.91)
17.50
0.404
0.543
0.744
3.91
4.*7
5.«
r>;-7.oo
(48.W
0015
Fig 1. Further analysis on various conditions of M-7 and M-61
[177]
does produce a quiet running propeller which is capable
of higher loading than otherwise, but gives a low hull
efficiency. Various devices can be adopted to improve this
position and a simple angled skeg can be of considerable
help, producing wake fractions nearly as high as with the
conventional form but associated with the low thrust deduc-
tion of the type of stern shown. There is a good deal to be
learnt from Yokoyama's paper.
Safety factors
Lee (UK): Commenting on the effect of hull shape on
stability, fig 14 of Yokoyama's paper shows a V-bottom or
single chine form to advantage over the round-bottom form
in respect of maximum GZ and range. He had expected to
see a discontinuity in the GZ curve of the V-bottom boat
where the chine emerges. Some British 75 ft (23 m) wooden
MFVs of deep round-bottom section are being replaced by
steel boats of double chine construction. Admittedly there are
some variables, but it may be of interest to note that although
the maximum value of GZ is the same, the range of the
double-chine is less. Regarding Yokoyama's statement that
the V-bottom boat is less dangerous than the round-bottom
one, the deep round-section MFV has proved itself in rough
seas over many years; full experience with the double-chine
boat is awaited It has already been necessary, however, to
strengthen the flat bottom aft of double-chine boats in order
to prevent damage from pounding.
Author's reply
Yokoyama (Japan): Answering Selman, he said that fig 4
was not drawn for the purpose of a quantitative contest
among the boats with different conditions, but should be
understood to reveal hydro-technical feasibility for the various
types of hull forms. Both models with straight frame (M-7)
and with round section (M-61) have a similar trend over
Fn>0.3 and, as is pointed out, the difference is insignificant
when disregarding displacement-length ratios.
For the reference (fig 1) however the old test results with
M-61 having V/(0.1L)a of 5.33 and 6.23, are a little above
M-7 up to Fn -0.30 and come down about to cross that near
Fn=0.35, whereas an additional test with M-7 having
V /(0. 1 L)3--9.76 gives a little higher (10-20 per cent) line than
that for M-61 with 8.86. As a general concept the fact should
be remarked that all these results, straight or round, have not
any noticeable hump even over Fn--0.30, and a simplified
form is able to realize the same excellent characteristics as the
best boat with normal section.
The importance should be placed on the behaviour 6f
boats among waves not only for seaworthiness but for con-
struction and economy of materials, wide and thick planks.
And ship's motion is not so restrained by the mechanism of
free surging that the difference between towing and propeller
condition may become secondary level of consideration. The
comparison of power increase could not be rejected for the
present assumption of nearly the same propulsive coefficient,
if there were not found any comparable report of wave test
with small boats. Sometimes the experiences are heard that a
Japanese small boat is able to cruise with dry deck even when
the inspection boat with round section is Fighting hard against
waves.
The curves in fig 5 of Yokoyama's paper are derived from
the smoothed results for respective torque, thrust and
revolution, so the line of w and t may become unfamiliar and
a snaky line is not so meaningful as faithful saw-tooth line
passing every spot. But the facts of quite low or negative
wake at higher speed are witnessed at some tank or sea tests,
and may be explained with potential flow running near the
deep and wide bottom like transom stern or midship of
Fig 2. Revolution of model propellers
1.5 nv'sec
ft/sec
normal boats. A little abnormal trend at low speed cannot be
relied on because of scale effect inevitable for such small
model propeller (3 in or 75 mm dia) that the blade runs far
under a critical Reynold's number.
Although 7° and 17° in fig 6, the illustrated rake of shaft,
have to be interchanged, the result of the lowest propeller,
L-12 low, is lowest compared with the highest, L-7. The
air-draw effect must be possible at transom, as suggested, but
fig 2 (above) does not show any pronounced difference
of revolution even between shallow L-7 and deep D-12, so
the apparent small and negative wake may be independent on
the air suction and resulted from a distribution of flow velocity
around the bottom.
The mis-estimation of launching power is caused by a
trouble of English translation. The phrase "with only female
assistance", should be revised to "with assistance of house-
wives from several families". A man-powered winch, fig 3, is
operated by two to four persons for a 30 ft boat (3 to 5 tons)
and four to eight persons for a 50 ft boat (about 20 tons), but
petrol-engined drum should be recommended even to keep
bigamous trouble out!
Fig 3. Manual capstan
[178]
EVALUATION OF EXISTING DESIGNS
Kilgore (USA): Gueroult has supplied some wise observa-
tions, and the approach he proposes certainly should be
pursued. Kilgore was not so optimistic about Gueroult's hope
for sharing of findings by neighbouring countries when even
neighbouring fishermen are notoriously secretive.
The curves, fig 1 to 7 in Gueroult's paper, are of value as
general guides, but they will vary rather widely from fishery
to fishery, as Gueroult observes. Some of these curves are
based on hydrodynamic efficiency. Some are the averages of
current practice, but not necessarily the optima for any
particular fishery. Kilgore's interest above all is in fig 8. These
curves arc important enough to receive an explanation longer
than one sentence. What does Gueroult mean, specifically, by
profitability? How did he obtain the input for this family of
curves? If the data were from the performance of certain
boats, how many boats were considered as suitable for a
sample? Kilgore's concern here is that length is the single
independent variable, but the way the curves were obtained
might significantly affect their optimum points.
Despite these obscurities, due no doubt to Gueroult's wish
to be brief, fig 8 does illustrate a notion that must be valid:
for any fishery at a place and time, there must be an optimum
length. Perhaps this is all Gueroult wished to illustrate.
von Brandt (Germany): Three short remarks on Gueroult's
paper from the point of view of a gear technologist, in con-
nection with the calculation problem mentioned :
1. There may be a constant influencing the design of
vessels, that is the nearly equal size of fishing gear on small
and large vessels. This happens to some extent for mid-water
trawling with small or big boats or in fishing with lobster
pots etc.
2. There are some gear with a high influence on design of
fishing vessels and others with a low one. The degree of this
influence depends sometimes on the size of the vessel. For
driftnetting and line fishing one needs almost no arrange-
ment for small boats, but one needs hauling devices for
bigger vessels and special engines to give the vessel a better
manoeuvrability.
3. One needs in many cases vessels with the possibility to
operate with more than one fishing technique, e.g. drift nets
plus trawls, bottom trawls plus mid-water trawls, trawls plus
purse-seines. In Europe as well as in many developing coun-
tries, one needs not so much greater flexibility. This will make
the calculations more complicated.
Doust (UK): Congratulated Gueroult on his paper. Much of
Gueroult's reasoning agrees very well with ideas at the NPL
and the effectiveness of these methods would also seem to be
verified by the results obtained.
Author's reply
Gueroult (France) : There is an apparent contradiction between
a method evolved on the basis of statistics and the desire to
use such a method for new types of boats, for which no such
statistics are available. He was anxious to forestall this
objection, the fact being that there are any number of un-
seeable sources; these are mentioned in the references given
in the paper.
Gueroult illustrated his method from evidence which was
immediately available to him — namely, ships of over 100
tons. If the method proves to be applicable, it can later be
made for values for boats of less than 100 tons. There are a
certain number of constants common to large and small
boats— men, fish, sea and, in large measure, fishing gear,
which therefore warrant similar treatment for small and
large tonnages.
COMPUTER DESIGN OF BOATS
Leathard (UK): Two aspects of the series of papers under
discussion are illustrated by a group of five 90 ft (27.4 m)
North Sea trawlers currently under construction in a UK
shipyard. Firstly, the hull forms were designed by NPL using
the results of computer analyses carried out on trawler forms
and reported elsewhere by Doust and others. The first vessel
landed the top catch of the week at her home port when she
returned from her maiden voyage and she continues to
perform well. The second vessel has also received good
reports and the other three arc due to enter service shortly.
This is an illustration of the satisfactory results which can be
achieved with a hull designed for efficient powering and sea-
kindliness by methods similar to those outlined in the
computer papers.
Swedish interest
Williams (Sweden): Doust points out that model tests for
vessels below 100 ft (30 m) are too expensive in relation to
the capital costs of the ships. He also suggests that resistance
qualities can be established from the performance diagrams
and thus, designing the lines of smaller fishing vessels can be
carried out on basis of present analysis results.
The general impression of this research work carried out
at NPL is that the investigations are performed in a distinct
way and that the mathematical methods are well defined.
Further, the results are most valuable for the future design of
fishing vessel hulls. But it is doubtful, in the present situation,
if the mathematical optimization can replace the conventional
model tests. Even if this analysis covers a wide range of
fishing vessel types and corresponding shape parameters it
will always be suitable, both from the technical and economical
points of view, to carry out model tests also for small vessels.
If a series of ten well-equipped trawlers of 80 ft (24 m) in
length are to be built for a cost of £50,000 ($140,000), a
short experimental investigation including, say, live hull
versions will cost about £4,000 ($11, OCX)), that is less than
one per cent of the total capital costs. Besides the resistance
qualities, the influence of hull form variations upon propul-
sion factors at free running, trawling and heavy towing is
tested, properties which are not fully covered by the present
analysis. Further, it is a well-known fact that the best resistance
hull form must not be the best propulsion full form cither at
free running or at towing.
However there is no doubt that Doust provides very good
recommendations for planning such systematical investiga-
tions which will be performed in case of a short series of
fishing boats as mentioned above.
The statistical analysis of FAO resistance data has drawn
the attention to the propulsion properties of the Swedish
common trawlers, especially those built of wood. The free
running speed qualities have not been tested enough. In recent
years the distances to the fishing grounds have been increased
and therefore it is important to reduce the "steaming-timc"
and above all try to get a better profit in form of a higher
free running speed from the very powerful engines which are
now installed. It is of course difficult within a time of some
years to introduce a quite new trawler design which could
better meet the new demands of free running speed. Therefore
it is important to modify those existing types, which are
favourable from other points of view. In this connection the
design trends received from the NPL analysis will be most
useful.
It is understood that the choice of a set of suitable hull
form parameters must have been difficult. At the Swedish
State Experimental Tank (SSPA) a corresponding analysis
of resistance and propulsion data are prepared on the basis
of draft functions. The draft functions indicate the influence
[179]
of the draft upon a selected set of waterline form parameters
and the formulation of these functions is a part of the pro-
cedure for defining ship lines mathematically, see SSPA
publication No. 55 and SSPA general report No. 13.
Regarding the "over-all" form parameters length to beam,
beam to draft, maximum area coefficient, prismatic coefficient
and longitudinal centre of buoyancy, Williams agreed with
Doust. These parameters correspond to the draft functions
for maximum waterline breadth and waterline area in fore
and afterbody. But there will be some discussion about the
"local" parameters including angle of entrance at designed
waterline, maximum angle of run and maximum buttock
slope. These values characterize only limited parts of the
hull and will have different meaning for different types of hull
forms. It is perhaps more suitable to choose the remaining
parameters from the draft functions for waterline angle and
curvature fore and aft as these aflecl a larger part of the hull.
The introduction of draft functions instead of local
coefficients in the performance analysis of course will increase
the number of parameters and perhaps also influence the
rectangular distribution of data points. However, if the NPL
work is to be continued and more input data are to be treated,
it is possible that the number of significant form parameters
must be increased in order to reach a still better and more
valuable result. An analysis based on draft functions can
then be considered, as these have the advantage to give the
hull form directly.
Practical and Helpful
Corlett (UK) : Doust's and Traung's papers really point a way
and are practical and helpful. It is a pity that the 40 and 55 ft
(12.2 and 16.8 m) vessels are depicted as being of wooden
construction, as there is an increasing tendency to build this
size of vessel in steel with beneficial results, particularly with
respect to capacity and propulsive efficiency.
The regression analysis approach, using a computer, to the
optimization of data is a powerful weapon but is nevertheless
dependent upon the quality of the forms used in the analysis.
It is felt that it would be advantageous if more data could be
made available and, of course, all tend to keep their better
results to themselves— especially on these smaller ships, many
of which are not model tested. However, Doust's fig 10 to 15
are valuable in that they give an individual designer an
opportunity to check out his designs.
The optimum forms themselves appear good but Corlett
suggested that the breadth is not adequate in view of the
V f**
tendency of ^ to increase in modern boats. Corlett suggested
furthermore that the Cnie curve should aim at optimization
at economical cruising speed as there does not seem to be
much point in doing so at any other speed. The amount of
power used at low speeds is small and, short of making radical
changes to hull forms, it is not possible materially to increase
the speed of a boat of given length.
Finally Corlett said that he completely agreed with fig 49
to 51 of Doust's paper* The half angle of entrance is a matter
of considerable importance, particularly in wood construc-
tion and he felt that the bow shape shown in the optimum
forms is possibly expensive and difficult to construct in wood.
It is not cheap in steel comparatively, but in wood could be
difficult. Therefore, in fig 49 of Doust's paper the dual
nature of the optimum half angle at a given prismatic co-
efficient is of considerable interest and value and he personally
favoured, and always had favoured, using the higher half
angle in small ships of this type rather than the lower. Corlett
had found that it minimizes pitch and tends to make the
vessel relatively independent of breadth in small design
changes. Additionally it gives much more room in the ship
and better stability on a given breadth.
Regarding the waterline shape aft Corlett had, of course,
been aware that in small high displacement/length ships,
resistance is relatively independent of the waterline shape aft
but fairly critically dependent upon the buttock angle. In a
small fishing vessel, the waterline shape aft is more a matter
of seakindliness than of resistance and it may well be that in
a given case a compromise has to be adopted purely from
this point of view.
Falkemo (Sweden): At Chalmers University they are par-
ticularly interested to co-operate with NPL and FAO in the
respect of fishing vessels. This is further encouraged because
this is the first time that a suitable mathematical equation
has been developed that can produce forms on a statistical
analysis. Naval architects have made attempts at this over a
long period of years and at last a suitable equation seems to
have been produced.
The model of the 85 ft (26 m) boat was so far only tested
in calm water, but a plastic model will be made for tests in
rough water and the results of these tests will be compared
with rough water tests to be undertaken on models of typical
wood and steel construction Swedish fishing vessels. The
Swedish vessels can also undergo tests in the full scale as far
as propulsion and seakeeping are concerned. These tests
have been made possible by the close co-operation with local
fishing skippers and it is hoped at least by the next conference
to have the results of these tests.
Technical queries?
Cardoso (Portugal): What meaning does Doust attribute to
the substantial increase in standard error with increasing
V/VL? In small fishing boats in Portugal, quite a variety of
values of V/VL apply and may be up to 1 .2 or more. It would
be interesting to know whether the authors have looked into
the choice of CP in relation to the applicable value of V/\/L.
Referring to fig 47, Cardoso asked whether similar variations
were studied at other values of V/VL. If so, were they found
to coincide with previous tests and practice at coinciding
values of other parameters.
In the Traung paper, why was not 14.51 taken as the best
value of Cilltt which would correspond to a Cp of 0.65
and a half angle of entrance of 22 Jn ?
More and more gear such as power blocks are now placed
on the deck and above it so that the beam of many small
boats has had to be increased. With high values of beam, it is
difficult to obtain small angles of entrance and low values of
Cp without creating shoulders on the hull form. Besides,
especially in wooden boats, it is more difficult to construct
boats with small entrance so that the importance of finding
relatively good forms with high values of angle of entrance
cannot be ignored.
Prohaska (Denmark): He made a few critical remarks on
Doust's paper. He did not like the choice of the Telfer's
coefficients used as a basis for resistance comparison analysis
of this kind. It uses a CB value containing length in the
nominator and a speed coefficient having length in the
denominator and therefore a comparison is only feasible
for the same length vessels. Prohaska did not want to expand
on this further as Froude discovered this situation a long
time ago.
Prohaska felt that displacement may be more important
for fishing vessels than length, as far as basis of design is
concerned. In Doust's paper the length-displacement ratio
shows variation from 4 to 5 giving greatly different dis-
placements. An added argument is that cost mainly depends
on displacement and not on length.
[180]
Prohaska would also like to inquire, especially to FAO,
why are the 86 coefficients found from the computer investiga-
tion not published and not included in the paper. Without
the actual figures it is impossible for any designer to use this
work and it would be important to include these coefficients
in the proceedings.
The extrapolation from the 16ft (4.9m) model to the
ship is very much dependent on the extrapolation method
adopted (in this case ITTC). If the form effect were to be
included, it might well effect the optimization of the resistance.
Finally although these vessels are optimized in regard to
resistance, this is not the final goal which should be optimiza-
tion of propulsion and fuel consumption.
Calder (UK): Reference is made to the effects on resistance
criterion of changes in the half angle of entrance of the load
waterline. In the discussion Cardoso pointed out how difficult
it is to obtain small angles of entrance and low values of Cp.
Would a more accurate basis of comparison not be obtained
by using the half angle of entrance of the mean draught
waterline instead of using that of the load waterline?
When using the half angle of entrance of the load waterline
widely differing results were obtained from vessels of similar
proportions and dimensions. Analysis of these results pointed
to the differences caused by V sections in the fore body as
compared with U sections and this led to using the half angle
of entrance of the mean draft waterline instead of that of the
load waterline. This method was used by Middendorf in his
investigations into forms of least resistance.
Praise and gratitude
Kilgore (USA): Had nothing but praise and gratitude to
express for the Doust and Traung papers. Doust and his
colleagues at NPL have achieved a scientific breakthrough
with their concept of applying the regression matrix to the
formidable assortment of variables in residuary resistance.
The next logical step in this project is publication of these
results in a form modelled perhaps after the Taylor-Gertler
curves. This is a big undertaking. It is hoped that Traung
will be able to find the means, and that the scientists at NPL
will continue to give this work their inspired attention.
One question: It is not clear to Kilgore the combination
of buttock slope and slope of load waterline adequately
describes the afterbody, and Kilgore hoped the authors
would show how they justify these two important parameters.
van den Bosch (Netherlands): Williams suggested that more
data would lead to more parameters. One should not only
seek the optimum in resistance and propulsion in smooth
water condition, but also investigate more in detail the
rough water condition. Introducing more variables would be
more valuable from the seakeeping point of view.
Tyrrell (Ireland) : Traung's paper is very exhaustive and must be
of considerable help in the earlier stages of new designs.
Model test results however must be applied with the utmost
caution ; for example, low prismatic coefficient with fine bow
lines make for decreased resistance, but do not necessarily
preserve other qualities of greater importance for fishing
vessels. Foremost of these is longitudinal balance of the hull
above datum waterline as well as below — there must be little
movement of location of centre of buoyancy from light to
loaded condition. A vessel must not be sensitive to con-
siderable movement of weight, e.g. stowing the fish hold
unevenly fore-and-aft.
The model test revelations of the desirability for buttock
lines of small angle confirms established practice in sailing
yacht hulls over a great many years.
Jimenez (Peru): Wooden boats in Peru are equipped with
thick stern pieces which make much turbulence and result in
bad inflow to the propeller and cavitation. As a result the
speed of the wooden boat is less than that of steel boats
with their sharper stern pieces. A great deal of cavitation was
eliminated by simply rounding the corners of the stern piece
of the wooden boats.
Author's replies
Doust (UK): Thanked Leathard for his comments on the
vessel that they had successfully designed together and which
his firm had built in some quantity. From the design point of
view, it is encouraging that the application of the statistical
method has been proved down to vessels below 100 ft (30 m)
in length.
Answering Corletfs remark that the breadth was not
adequate, Doust said that the forms satisfy the stringent
Rahola criteria and also considering the results of the analysis
further increases in beam would not materially affect the
resistance performance.
Williams seemed to be concerned with the possibility that
the demand for model tests will be decreased after making
such mathematical analyses. As a member of a sister towing
tank organization also deriving income from model tests,
Doust had found that, because of the increased interest on
the part of vessel owners in utilizing the results of such
analyses, the services of the towing tank are required even
more. There is also the additional aspect that tank facilities
can be used more effectively in conducting much needed
wave tests. One of the most important factors found at NPL
for such vessels is that low resistance forms can also be made
to have good seakeeping performance by paying proper
attention to the above-water form.
Doust thanked Falkemo for telling of his plans for future
co-operative research. Doust particularly looked forward to
the results of the tests in waves with plastic-hulled models
and, eventually, full-scale trials on shipboard.
Cardoso will note that as speed increases the percentage
accuracy of the results is more or less constant, since the
average level of Cn rises as speed is increased.
Jn reply to Prohaska, Doust stated that the use of Telfcr's
resistance criterion can provide both the effect of length and
displacement, since both are incorporated in the regression
equation stored in the computer. There does not seem to be
any difficulty in presenting the regression coefficients re-
quested by Prohaska, but it was not felt that they had their
place in a paper of this nature. If people started computing
resistance with hand calculators etc., it would take a long
time and it would therefore be much simpler if they wrote to
FAO and they together did the work.
But it should be stressed that these coefficients will require
modification as more data become available and new im-
proved forms arc incorporated in any further analysis.
Regarding the use of the 1957 JTTC line, it seemed logical to
use this internationally accepted formulation for predicting
ship performance. It was Dousfs intention to allow for any
possible future changes in the extrapolation procedure by
presenting basic 16ft (4.9m) model data so that any sub-
sequent adjustments could be made by minor revision of the
computer programme.
Kilgore had asked for design charts similar to the Taylor
Gertler curves. It is to be hoped that such charts can be
prepared and incorporated in an FAO design book on some
future occasion. The use of the buttock slope angle and run
angle is justified by the results. For example, the fact that
several designers from many countries and also participants
in the FAO/Swedish Training Centre on Fishing Boat Design
have been able to use these form parameters and produce
[181]
designs from them, having the required performance, is
evidence enough.
Doust agreed with van den Bosch that propulsion tests in
waves are urgently required for small fishing vessels and it is
the intention to make such experiments as soon as time and
events permit.
Tyrrell seems to be concerned, as a boatbuilder, with the
pace of fishing vessel development in the conservative fishing
industry. Doust pointed out, however, that as Tyrrell himself
had said some of the conclusions were first proposed some
sixty years ago, but not apparently acted upon. Urgent atten-
tion should be given to these design requirements, so that
substantial gains could be made in fishing vessel performance
without waiting for the ad hoc step-by-step method envisaged
by Tyrrell.
Doust agreed with Selman's general remarks on the
question of straight-framed versus round bilge boats. Although
there are some constructional advantages for straight-
framed boats, particularly in developing countries, as pointed
out by Selman, he thought that a round bilge form in general
could be made superior in terms of both resistance per ton
of displacement, and power per ton of displacement. Sea-
keeping qualities covered a wide range of interest and im-
portance and it was not possible to generalize. Some vessels
needed minimum speed loss as the prime requirement, whilst
others needed minimum bow or stern motion, accelerations
or wetness. Doust therefore felt that Yokoyama's paper
should be checked out on a wider range of forms, perhaps
including a current, European, well-known successful form.
Hayes (UK :) For written reply see page 197
Traung (FAO): The question as to what speed to optimize
on was taken after much discussion. It was extremely difficult
to decide the proper speed because of the lack of reliable
full-scale data on such fishing boats; as speed and power are
difficult and comparatively time-consuming to measure on a
small boat. Fishermen usually exaggerate the speeds their
boats are making. The final decision was to optimize at
V/VL— 1 .1 . It is believed that such a speed really corresponds
to the economical operating speed of most fishing vessels.
Maximum trial speeds with light load and a clean bottom and
the engine in peak performance arc certainly higher but that is
not the condition for which one has to design.
Corlett said it was a pity that the 40 and 55 ft vessels were
designed for wooden construction. While it could be argued
that wood is still a most important material for boats of such
sizes, this shall not be done. The reason for designing in wood
is simply to see how the optimizing exercise would work for
vessels built both in wood and steel. Furthermore, the
optimizing exercise was really not made so much to develop
the final answer to hull-shape of boats of 40, 55, 70 and 85 ft
but to see how the computer predictions would compare with
actual model tests. One could have chosen other length-
displacement ratios, other L/B, etc. As a matter of fact, now
that it is known that the computer programme works satis-
factorily, it is hoped to find time and funds to make "syn-
thetic*' model tests of whole families of optimized forms so
that it will be possible to establish a kind of Taylor for
fishing boats. Before that, however, it would be useful if it
were possible to include the Japanese data in the programme
and lately investigations have been made which indicate that
a further parameter might make it possible also to use that
mass of important information.
STABILITY AND SEA BEHAVIOUR
The work of IMCO
Nadeinski (IMCO): The Inter-Governmental Maritime Con-
sultative Organization (IMCO) is a specialized agency of the
UN. IMCO is a sister-organization of FAO. Sixty States are
now members of IMCO. Its headquarters are in London. The
main objectives of IMCO are to facilitate co-operation among
governments in technical matters of all kinds affecting ship-
ping, and to encourage the general adoption of the highest
practicable standards of maritime safety and efficiency of
navigation. The Organization is responsible for convening,
when necessary, international conferences on shipping matters
and for drafting international conventions or agreements on
this subject. So, for instance, in March 1966 was held the
International Conference on Load-Lines.
IMCO also administers several international conventions
including the International Convention for the Safety of Life
at Sea, 1960. The Conference which prepared this Convention
also adopted a number of Recommendations arising from
deliberation of the Conference. One of the Recommendations
called upon studies on intact stability of passenger cargo and
fishing vessels, with a view to formulating such stability
standards, as may appear necessary. The Conference further
recommended that in such studies IMCO, to which this
Recommendation was addressed, should take into account
the studies already undertaken by FAO on stability of fishing
vessels, in co-operation with FAO on this matter. Following
this Recommendation IMCO initiated stability studies which
are conducted by the Working Group on Intact Stability of
Ships and by the Working Group on Stability of Fishing
Vessels. The first Group is dealing with all types of ships
and in particular with passenger and cargo ships. The second
is concerned with fishing vessels only. Both bodies are work-
ing in close co-operation and are reporting to the Sub-
Committee on Subdivision and Stability Problems. Prohaska
(Denmark) is the Chairman of the Sub-Committee and
Bardarson (Iceland) is the Chairman of the Fishing Vessel
Working Group.
This came into being in July 1964, and held since their
four sessions, the last being concluded on October 14, 1966.
Experts from 17 countries are taking part in its work. Follow-
ing agreement between IMCO and FAO, the Group is now
in co-operation with FAO which is participating at the
secretarial level. The terms of reference of the Group cover a
wide range of subjects to be considered.
One of the items provides for drafting recommendations
with regard to stability criterion to be used for fishing vessels
of the different types. With this in view, the Group after
thorough consideration, has chosen five parameters given
below as possible future stability criterion and is studying
them :
• Maximum righting arm, UZm
• Angle of heel at maximum righting arm, </>m
• Angle of vanishing stability, 0V
• Initial mctacentric height, GM0
• Angle of heel at which the edge of the upper deck
immerses, 0rd
Another item of the terms of reference calls for con-
sideration of operational practices which have an unfavour-
able effect on the intact stability of fishing vessels, with a
view to formulating reasonable and practicable precautions
which would prevent reduction in stability. Consequently, the
Group prepared its advice to fishermen, which contained
certain suggestions as to precautionary measures which
should be followed in order to maintain adequate stability of
fishing vessels during operation. The Group recommended to
inform all fishermen on these suggestions in a very simple
language using terms and expressions readily understood by
them, though most of the points should already be known
by experienced fishermen. The Group also recommended that
these suggestions should be included by fishery schools in
their training of fishermen.
[182!
Recommended practices
These suggestions were brought to attention of govern-
ments concerned. The Fishing Vessel Group worked out the
"Recommended Practice for Freeing Ports" and "Recom-
mended Practice for Exterior Hatch Coamings and Door
Sills" and recommended to apply these to new fishing vessels
and, similarly, to existing vessels as far as practicable. These
two documents will be brought to attention of administra-
tions, inviting them to inform all concerned including fisher-
men, builders and owners of fishing vessels.
The Group is studying national regulations and practices
concerning icing and shifting board and other devices to
retain cargo, with a view to drafting recommendations on
these matters. The Group is examining and comparing national
stability requirements for fishing vessels and in this work it is
applying these various regulations to a number of selected
fishing vessels. The work of the Group also includes analysis
of casualties caused by unsatisfactory stability, the information
being collected by means of intact stability casualty records,
established by IMCO.
The Group examines the stability calculations carried out
by various countries for a selected number of fishing vessels
of different sizes and types. These calculations were made on
the common assumptions prepared by IMCO, which are
known as a "Uniform basis for compilation of comparative
stability calculations" and which were published in the
IMCO Bulletin and reprinted by several technical magazines.
The Group agreed to recommend the determination of
ship's stability by means of the rolling period test, for fishing
vessels up to 230 ft (70 m) in length. This recommendation
had been arrived at by the Working Group on Intact Stability
of Ships, as a result of theoretical studies and model tests.
This Group worked out a memorandum to administrations
on this subject which, among other things, contains a recom-
mended text for the guidance to be supplied to masters of
ships. This will enable the master to check approximately the
stability of his vessel by simple calculations. Having deter-
mined the period of roll he will calculate the initial meta-
centric height (GM0) and compare it with a critical value of
GM, to be given by the administrations for each particular
vessel and for various draughts.
The work programme of the Fishing Vessel Working Group
includes other important items, such as:
• establishing of a simple method for judging stability
of small fishing vessels which could be easily applied
by their crews
• investigation of the desirability of the establishing
minimum freeboard requirements for fishing vessels
• studies on external forces affecting stability of ships,
etc
Spanish Requirements
Rebollo (Spain): The first step in the process of boatbuilding
in Spain is to apply for the appropriate licence; this is the
shipbuilder's responsibility. In the case of boats of over
35 GT, the application must be accompanied by designs
showing the general layout, hull form, hydrostatic curves and
scantlings and by a list of fire-fighting and life-saving equip-
ment and also a statement regarding, inter alia, the work that
the boat is intended to perform.
If the design does not comply with the statutory regulations,
the authorities make the appropriate observations which
must be taken into account in construction.
Once built and before they can go into service, all decked
boats undergo a compulsory stability test. For boats over
35 GT, this test determines stability in conditions: empty, on
leaving harbour, when leaving fishing grounds and when
docking in port, the transverse stability curves being plotted
in each case.
The research carried out by IMCO on fishing craft stability
is studied with great care. Meanwhile, in Spain the Rahola
criterion (including a permissible inclination of up to 60 ) is
applied.
A study is being made for assigning a freeboard to fishing
vessels, related to the stability of the vessels. For that purpose
a supplementary loading condition must be taken into
account. This loading condition applies to the maximum
allowable displacement of the vessel, with a stability that
satisfies the statutory stability requirements, corresponding
to "departure from the fishing grounds" with fish in the
holds and on deck (when this might be possible) and with
the consumables necessary to complete the proposed free-
board displacement.
Many fishing wrecks
Lenier (France): It is a well-known fact, borne out by the
statistics of accidents at sea, that the vulnerability of ships is
in inverse proportion to their tonnage. At present, over the
oceans of the world and particularly near the coasts there
are many wrecks of fishing craft. When these arc due to
collisions, running aground or errors of manoeuvre while
fishing, they do not always have tragic consequences because
the crews have enough time to make use of their radio and
thus to alert coastal stations or other boats in the vicinity.
Frequently, however, in an exceptionally heavy sea or sudden
storm, a number of small boats, unable to withstand the
fury of the elements, disappear leaving no trace. To mention
one instance: off the French coast, specifically near Britanny,
there was a sad experience of the loss of 13 fishing boats,
without trace, in a single night. The boats in question had
excellent scantlings, were sufficiently large for the grounds
they habitually worked and had radio equipment in perfect
running order, having been carefully serviced every time they
put into their home port. An enquiry conducted by the
Ministry of Merchant Marine yielded no more than surmises
as to how these boats sank. They must have been heading for
a violent storm and must have been caught by a wave which
carried away their superstructures, so that the usual distress
signalling system installed on them could not be used. Such
events are not peculiar to France. With greater or lesser
frequency, they occur in all the seafaring nations.
The Minister for the Merchant Marine has not hesitated
to make it compulsory for virtually all small fishing boats to
carry a new method of radio distress signalling which should
do much to safeguard human lives at sea — that is worth
reporting on for the sociological implications. The French
radio and electric industry has developed a transmitting buoy
which is thrown overboard when catastrophe strikes a boat.
The buoy continues to float and emits radio distress signals
which, while they do not give the boat's position, do give a
call signal whereby the boat while yet in danger, or even after
it has disappeared, can be identified. The same signal also
enables other boats so alerted accurately to locate the disaster
with their radio direction finders. The specifications of this
buoy are the subject of a decree which will become operative
very shortly. Something like 1,000 new fishing boats will be
affected.
All countries concerned for the safety of their fishermen
ought to adopt measures similar to those of France.
Anti-rolling tanks
Yokoyama (Japan): There arc two kinds of devices for
damping ship oscillations, passive and active ones. The normal
bilge keel is an example of a passive damper turning natural
flow action into useful depressing effect; whereas anti-rolling
[183]
10
.2?
o*
a
"6
05
1.0
1.5
Lw/L
T7/^ 4. Abkowilz* experiment with the model of series 60
withjwithout a bow fin (area ratio — 0,07)
fins activated by gyro-control is the other example. The
possibilities are:
A. Passive anti-roll devices:
1. bilge keel, centre board, fixed fin
2. flume tank
3. weight or large gyro
l.O r
of stern. Heave control is not usually required, except special
instrument for oceanographic observation.
A row of broken pieces of fin (Al) is more effective than
normal bilge keel while steaming, but roll is more during
anchorage. A Japanese fisheries inspection boat with such
kind of fins could not board other ships side by side without
contact damage. Flume tank (A2) is also effective except it
requires tank space with 2 to 5 per cent of displacement
(Frahm, 1911) and has somewhat noisy hiss. Shifting weight
or huge gyro (A3) is becoming an old tale (Thornycroft,
Cremieu). Automatically powered systems (Bl, B2, Dl and
D2) are possible for ships where cost is no limiting factor.
Fins and tanks have been considered for pitch damping
after the anti-roll examples. As for anti-pitching fin (Cl),
pitching angle is resulted as a magnified or damned amplitude
of external wave moment with fin action, which is proportional
to its area, square of advance speed, distance between fin
and midship, and rate of lift coefficient increase to pitching
angle. Abkowitz (1959) gave the results of fig 4 in which the
reduction of pitch angle becomes more than 50 per cent on
the wave of longer than a model bearing bow fins with the
area of 7 per cent of waterplane. The damping effect of active
fin (Dl) is not much larger than fixed fin, but it prevents from
stalling at large attacking angle to flow and always keeps the
most efficient work. A comparison is shown in fig 5 between
the heaving force of fin and sphere near the water surface,
experimented by Motora (unpublished) and calculated accord-
ing to Haskind-Newman's formula. Those effects depend on
heaving period. The damping effect of bulbous bow is
experimented by Yokoyama (1961) as in fig 6 where the
rig 5. Motora\s experiment and Haskind-Newnum's calculation for heaving force of various models near the
water surface
B. Active anti-roll devices:
1 . automatically-controlled fin
2. automatically-regulated water tank or weight
C. Passive anti-pitching devices:
1 . anti-pitching fin at bow and/or stem, bulb
2. anti-pitching tank
D. Active anti-pitching devices :
1. active fin electronically-controlled
2. active tank.
Active yaw control by rudder is so familiar that it need
not be added ; and passive yaw control is practised by design
W/gT
Fig 6. Damping effect of large bow bulb fitted to the wavelexx
model experimented by Yokoyama
184]
pitching amplitude isj-educed more than 50 per cent above an
optimum speed, v/\/gL = 0,25.
The passive tank (C2) is regarded ineffective for anti-
pitching. When the natural frequency of tank water, however,
keeps higher than encounter period, Motora (unpublished)
makes it possible through a theoretical calculation to damp
the motion with a particular device of flared tank, having side
opening near the waterline through inside duct.
Foussat (France): Has van den Bosch studied the effect of the
anti-rolling tank on a model which did not itself have fuel
bunkers or water tanks? Now, with the real thing, it is rare
not to have one or more such bunkers or tanks in the process
of emptying and which, accordingly, have free surfaces and
hence a certain impact on rolling, which is possible to study
and which varies according to the shape of the free surfaces,
the volumes of liquid in movement, their viscosity and so on.
In order to apply the free surface tank principle in a real
boat, there should be difficulty in having a fuel bunker carrying
out the required function. The tank in question would be the
boat's standby tank, which means it would normally maintain
a constant level throughout the voyage. If, in case of need,
the voyage must be prolonged beyond the expected time, the
fuel would be consumed by the engine. If, in an emergency, a
rapid increase in the GM value becomes necessary, the tank
would be discharged into a normal fuel bunker — by gravity
or by pumping. This arrangement would make for more
space on board. It would not involve reducing the capacity
of the fish hold or of the space allowed for the engine.
However, the calculation of roll damping for any craft,
whatever stabilization system is adopted, must allow for the
inertia of liquids in all shipboard containers which are in the
process of emptying.
Effect of gales
Gueroult (France): Fishing craft behave the same at sea as
other boats, but have suffered from the conservative view
that a craft with low initial stability is a better boat in bad
weather. A better boat in what respect, and in what sort of
bad weather? It is probably that at force 8 and above, a
craft with low initial stability will be more comfortable. As a
fishing craft, between calm sea/fine weather conditions and
force 8 (which represents the normal range of working
conditions) it will have a more stable working platform than
if it has high initial stability.
The lack of precision in the terms "low stability" and "high
stability" shows that only generalities are being considered.
As a rule, by low stability is meant that deemed minimum for
safety, whether the boat is upright or in an inclined position.
For small boats, "high stability" is the highest obtainable
without ballast and without exaggerated transverse dimen-
sions. The naval architect cannot be content with general
principles, but must specify dimensions which will offer the
desired seakeeping performance. Fig 4 and 7 of Gueroult's
paper were prepared with this in mind and have in large
measure been verified.
Model testing for working platform stability up to force 8
and for different tonnages would be very useful. The inevitable
consequence of a craft which is "too" stable in bad weather
will have to be accepted and, as far as possible, offset by the
usual navigational precautions. The question may also be
asked as to whether anti-rolling devices can find their greatest
usefulness under extreme conditions?
Stability aids crew efficiency
Gronningsaeter (Norway): Underlined the need for stabilizing
fishing vessels with a passive system by mentioning that one
of the most important aspects of economical fishing today is
to have the manpower reduced. In Norway they have just
reduced the manpower in their purse seining fleet by several
thousand men in two years and have increased the catching
ability. They have seen no such rationalization in trawlers
and longliners. Waterman mentioned at the White Fish
Authority Conference in London in 1965 that one of the big-
gest needs in the trawlers was to eliminate the hard work of
gutting and heading fish manually. Machines can do this in a
fairly quiet ship, but will not work well in heavily rolling
ships. Such a machine can do the work of 20 men gutting and
heading 40 fishes per minute against 4 fishes per minute by a
single man. The machines can work 24 hours a day. The same
will apply to herring sorting machines which will not work
well when the ship rolls more than 10 to 15°. One can reduce
the trawlers and longliners crew by at least 50 per cent if
the process of fish handling is mechanized after the catch is
brought on deck. Passive stabilization can aid such rational-
ization and is therefore of primary importance in the earning
capacity of the fishermen and the ship.
Gronningsaeter called attention to the fishing vessel builders
that if they could build ships in series of, say, 5 to 10 ships
of the same lines and general properties, the cost of passive
stabilization will be very small indeed compared to the
advantages gained.
Importance of damping
Field (USA): van den Bosch's paper advocates the introduc-
tion of undamped free surface roll stabilizer tanks into
fishing vessels as a means of reducing rolling in heavy seas.
Perhaps the word "undamped" is a misnomer, since van den
Boseh appears to rely upon the development of a transfer
wave (bore effect) as well as frictional damping to provide a
necessary damping of the liquid within the tank. From his
aversion to stiffening placed within the tank, it is assumed
that primary reliance is placed upon liquid damping through
the development of the transfer wave.
Basic papers on this subject, such as the works of Chadwick
and Klotter and others, as well as proprietary research which,
for commercial reasons, remains unpublished, show the
possibility of large dcstabilization effects in a theoretically
undamped tank which is tuned to the resonant frequency of
the ship. Measurement of the damping developed in the
liquid by the wave itself is difficult, and cannot be accomplish-
ed separately from frictional damping. This damping should
also be, in the absence of full-scale data, subject to a relatively
indeterminate scale effect. It may well be that an uncontrolled
free surface lank such as advocated by van den Bosch will
more closely approximate the theory of Chadwick and
Klotter than is made apparent by the testing of models.
It is believed that the introduction of controlled damping
to a free surface tank is necessary in order to make the lank
useful over a wide range of sea conditions and variations of
loading. If one accepts the analogy of Chadwick and Klotter
as substantiated by Ward and others in unpublished reporls,
and assume that the crossing points remain fixed, or nearly
so, then it must be possible to vary the internal damping of
the liquid in order to achieve an optimum, thereby resulting
in a nearly flat response over the entire frequency range.
This is best done by the installation of flow restrictions. The
flume stabilization system, a passive tank system, designed by
this method has been selected for over 200 vessels, including
a number engaged in the fishing industry, and the results
obtained have been highly satisfactory. It is inleresling to
nole Ihe continuing increase of acceptance of free surface
passive tanks since the commercial introduction of this
system in 1960. This continuing acceptance is no doubt the
cause and effect of continuing research in the field.
While van den Bosch refers to the limitation in tank size
[185]
which results in the 50 per cent roll reduction shown in his
fig 17 and 18, he does not state the nature of the sea spectrum
in which this reduction was measured, in other than mathe-
matical terms. This sea spectrum appears to have an approxi-
mate significant wave height of about 1 ft (0.3 m). In this
regard, significant wave heights exceeding 5 ft (1.5 m) occur
in the North Sea and Grand Banks areas, according to the
climatological tables, about 60 per cent of the total time.
Recognizing the limited tank size stated and the tendency for
the response of the stabilized ship to peak at a non-resonant
condition, the result that would be obtained in more rep-
resentative conditions would not be adequate. It would be
interesting if van den Bosch would set forth the tank size that
he feels to be required to obtain adequate roll reduction (for
example, 75 per cent) for the sea spectrum used in fig 17 and
18, as well as for the areas described above.
It should also be stated that fishing vessels may be subject
to greater variations of loading than those considered in this
paper. In addition, captains of such vessels may or may not
be concerned about stability, and the introduction of a large
uncontrolled free surface may present problems if not
handled properly. Here again, the introduction of sufficient
damping within the liquid to provide a flat response over the
entire frequency range is an added measure for safety and
efficiency.
In addition to this basic disagreement with van den Bosch,
as to the necessity for internal damping within the passive
stabilizer tank, it is also necessary to dispute the statement
relative to activated "U" tanks, since to Field's knowledge
no successful activated tank system has yet been installed in
a large vessel. It is believed that statements as to relative
efficiency should, in fairness, be deferred until after sufficient
operational experience has been obtained.
Experience with bilge keels
The necessity for retention of bilge keels depends upon
several factors. Some 20 vessels fitted with the system of
Field's firm have been operated in Arctic service by the
Canadian Department of Transport, through the expedient of
fitting heating coils within these tanks. Here again, the proper
amount of internal damping within the tank allows a good
stabilizer response even when the stability has been drastically
altered by icing of the upper portions of the vessel. While it is
true that the damping of bilge keels increases considerably
with large motions, the relative effect of bilge keels depends
on the size of the stabilizer tank. A properly sized and effective
stabilizer tank will furnish good stabilization even at extreme
angles of roll. This is not to advocate removal of bilge keels
from fishing vessels as such, since this is dependent upon a
basic decision as to whether minimum motion is the principal
factor or if the highest possible speed and maximum fuel
economy to and from the fishing grounds is of greater
importance.
The conclusions of van den Bosch relative to a passive tank
with flush bulkheads being an effective means of roll damping
are disputed, particularly with regard to reliability, as the
failure to obtain a flat roll response independent of frequency
for loading can result in serious operational difficulty. In any
event, it is difficult to refer to the reliability of a system with-
out the presentation of full-scale results.
Further, it would have been of interest for van den Bosch
to specify additional references, other than the mention of
Vossers. The work of Watts, as reported in the INA Trans-
actions of 1883 and 1885 bears some relationship to the
system proposed, and there are possibly additional portions
of the prior art, used in the study, which would be of interest.
Stabilization by a properly designed passive tank system
will greatly improve the productivity and utility of fishing
vessels, and is a matter for further consideration by all con-
cerned. Stabilization attempted by an unproven system
containing inherent limitations and deficiencies presents a
potential danger, particularly in smaller vessels. It is not a
question of the benefits of passive tank stabilization, as these
are now almost universally accepted, but rather a matter of
obtaining these benefits fully rather than only in part or not
at all. The most discouraging factor in obtaining general
acceptance of the principles of passive tank stabilization is
the damage which can be done by one poor installation.
Pitch and roll tested
Foster (UK): In June 1965 the White Fish Authority, on a
normal commercial voyage, carried out measurements of the
pitch and roll of a stern trawler fitted with a passive tank
free surface roll stabilizer. The principal dimensions of the
vessel were as follows: Lpp 215 ft (65 m); Beam 41 ft (12.5 m);
Draught 15.4 ft (4.7 m); Displacement 2,000 tons (sea water);
Virtual GM 2ft (0.6m); Sea water stabilizing tank 20 tons.
Several measurements were taken with the ship in the stabilized
condition, i.e. 20 tons of sea water in the tank, and immediately
afterwards, in the unstabilizcd condition, i.e. stabilizing tank
empty. Typical results obtained were as follows:
• In a force 5 beam sea at a speed of 5 knots without
the trawl gear down, reduction in roll was 25 per cent.
• In the same condition but with a quartering sea, the
reduction in roll was 33 per cent.
These results obtained in real seas were rather disappointing.
It must be pointed out that the tank was an afterthought
and was placed on the vessel in a position which was far from
the ideal. Its actual position was aft under the stern ramp, the
water in it was therefore subjected to yaw accelerations as
well as to sideways linear accelerations and roll.
Because the tank was so unsuccessful it has been removed.
However, this docs not mean the end of commercial appraisal
of such stabilizers in the British fishing fleet. At the present
time, there are a number of stern trawlers being built which
are to be fitted with them. Two in particular are sister ships,
one of which is to be fitted with a passive free surface tank,
while the other with a controlled passive tank of the U-tube
type, When these two ships come into service the White Fish
Authority intend to arrange to have them operate together
so that a direct comparison can be made on the performance
of the different systems. Once this has been done, it is hoped
to publish the findings.
Backed by experiments
Goodrich (UK): van den Bosch is to be congratulated on the
presentation and contents of his paper. He has shown that it
is feasible to reduce the rolling motions of fishing vessels
using a free surface tank of plane rectangular section. Good-
rich wished to endorse all the conclusions reached in the
paper, but it is worth emphasizing one or two points.
The results indicate that, given an adequate length of tank
a dramatic reduction in the roll response can be achieved.
The one factor which can then control the damped roll
response is the depth of water in the tank. Fig 11 to 13 in
van den Bosch's paper show the effect of varying the parameter
h/b from 0.06 to 0.08. It can be seen that a change of this
order produces relatively large changes in the response and it
is worth noting that for the ship considered, of breadth
20.28 ft (6.18 m), the depth of water would be 14.6 and 19.5 in
(371 and 496 mm) for the two curves given. This illustrates
that the depth of water must be measured very accurately in
the ship. An increase in depth beyond 19.5 in will lead to a
serious increase in the roll response at low frequencies, which
could affect the vessel when moving in quartering seas.
[186]
The results of the tests in irregular waves show that caution
must be exercised when considering the results of tests in
regular waves, or from oscillator tests. Fig 15 in van den
Bosch's paper for example shows that the peak magnification
factor of 11.5 is reduced to 1.5, an apparent reduction, of
95 per cent. However in irregular waves the significant roll
angle is reduced from 13.72° to 6.84° when stabilized, a
reduction of 50 per cent. These figures are in line with the
experience at NPL.
Experiments have been in progress with a stern trawler
for some time at NPL. The results substantiate those given
in the paper and help to emphasize the point made earlier
regarding depth of water. A variation of h/b from 0.056 to
0.081 represented a change of 12 in (305mm) in depth for
the ship. In irregular seas corresponding to a wind force 5,
significant wave height of 10ft (3.05m), the significant roll
angle was reduced from 33° out to 15 , a reduction of just
over 50 per cent. These results are for the model at zero
speed. The effect of forward speed is to materially reduce
the significant roll angle in both the unstabilized and stabilized
condition.
Whilst roll spectra are of interest to the expert it is suggested
that this form of presentation is of little interest to the ship
owner. A statistical presentation of results in the form of
cumulative distribution diagrams of roll angle are easier to
explain than spectra and show the reduction in maximum
roll angle as a percentage probability.
There is no doubt that stabilizer tanks, of the type described
in the paper, can be used widely in fishing vessels provided
that adequate space is available in the correct position in the
ship. However in certain circumstances, it is necessary to
introduce some form of constriction in the tank in order to
obtain the maximum roll stabilization. Stabilizers of this
kind have been designed and tested at Ship Division, NPL,
and are being installed in many vessels including several
stern trawlers.
More evidence wanted
McNeely (USA): He took some exception with van den
Bosch, having had some personal experience with anti-rolling
tanks. From a study of mathematical expressions and results
of model experiments, one would conclude that anti-roll
tanks or "surge" tanks would be a distinct advantage for
fishing vessels. More convincing evidence would be the actual
installation and successful use. On one occasion, McNeely
had cruised in unprotected waters aboard a fishing vessel
having an anti-roll tank and was not favourably impressed.
Although model tests and calculations prior to construction
were excellent, performance of the full-sized tank left con-
siderable to be desired. It appeared that inconsistent peak
frequency of swells interrupted a constant frequency of surge
within the tank, causing correction of some rolls and greater
amplitude to others. Of particular nuisance was occasional
late correction in rolls, resulting in a mental overcorrection
by the passengers. It was most difficult to get one's "sea
legs". Two weeks aboard the vessel resulted in disenchantment
with anti-roll tanks. Crew members having considerably more
time to evaluate the tank expressed similar opinions.
Personal experience given
Nickum (USA): In considering the effects of anti-rolling
tanks Nickum requested someone to come up with a specific
definition on which everyone could agree for the term "roll
reduction1'. The term is used to define the reduction in the
amplitude of roll and is also used to define the reduction in
number of rolls over a given figure in a particular sea spectra.
A simple, clear-cut definition that would give a comparison
of the operation of a vessel with and without roll tanks and
thus be a measure of the benefit of these tanks would be
helpful to the industry.
Nickum had personally had practical experience with anti-
rolling tank installation in two vessels. The first, a 1 45 ft
(44.2 m) ship operating out of Honolulu, and the second a
1 60 ft (48.7m) ship operating off the US Pacific Coast. In
the first case the anti-roll tank design called for holes to be
placed in the centre vertical keel which extended longitudinally
through the tank. These holes were not put in by the builder
and thus did not allow passage of water through the keel.
Unfortunately adequate tests and trials could not be made
before the vessel had to leave for her home port of Honolulu
and the action of the tank on the delivery trip and in the
first several voyages of the ship was very unsatisfactory.
Subsequently the holes were installed and tests were made
that indicated effective reduction in roll. The crew, however,
was still dissatisfied with the action of the ship and felt that it
was uncomfortable. It took two years before they got used
to using it and realized its effectiveness. On the second ship,
which was also an oceanographic vessel operated off the
US West Coast, the tank was installed properly, was activated
on the first trial voyages, and met immediate acceptance on
the part of the crew, a number of whom had been on sister
ships that had not had this type of tank. The accuracy of the
subjective judgment of crew members on a ship's motion
always makes it difficult to get an accurate reflection of the
true value of any device affecting ship's motion.
Wave slopes analysed
Nonweiler and du Cane (UK): van den Bosch's paper provides
most useful and comprehensive information on the dynamics
of passive tanks. As van den Bosch notes, some obscurities
remain due to non-linearities in the performance over a wide
range of roll amplitude, and the experimental data in fig 14
to 16 are quoted as indicative of this. Certainly the oscillation
experiment shown in fig 14 suggests some lack of precise
tuning between tank and ship (of the kind illustrated in fig 4)
and would seemingly bear out van den Bosch's remarks con-
cerning the variation of tank natural frequency with amplitude :
the roll amplitudes in this experiment are quoted as less than
the 0.1 radian of the calculation, but a more precise indication
would be interesting. On the other hand, the comparison
between calculation and measurement in the experiments
with irregular disturbances, which would be anticipated to
be most revealing of non-linear effects, shows a good agree-
ment.
Nonweiler and du Cane had recently completed a very
comprehensive analysis of wave slopes as deduced from some
3,000-ten-minutc observations (spread over a year) of the sea
at Sevenstones Light, supplied by the National Institute of
Oceanography. From this it would appear that a significant
wave slope amplitude of 3J degrees is typical of an "average"
sea: values as high as 6 degrees would be experienced for
10 per cent of the time (allowing for an arbitrary direction
between wave fronts and ship motion) and values of 10
degrees would be encountered for 1 per cent of the time. It
would be wrong of course to seek to find the corresponding
roll angles in such steep seas by applying the magnification
factors quoted by van den Bosch. As he mentions, the ship's
natural damping improves with increasing amplitude, whereas
the stabilizing effect of the tank would presumably be reduced.
Nonetheless, it is in such steep seas that fishing becomes
impossible, and the cost of an effective stabilizer would
begin to be repaid.
van den Bosch in his introduction does not mention the
moving solid weight (mounted, say, on a curved track,
buffered at each end) as an alternative stabilizing device; it is
one which has been apparently neglected as yet, but in which
we have an active interest. It exists in various forms. It may
[187]
rely simply on "natural" mechanical friction, in which case
suitable adjustment of this friction and track curvature can
produce a roughly similar performance to any free-surface
tank, with however the obvious advantage that the weight,
being more compact, has a larger effective moment than the
same mass of water, and occupies a tunnel of only about a
tenth of the recommended tank volume; further, it avoids
some of the operational disadvantages of water, and main-
tains its natural period independent of amplitude. In a
second form, it appears as a "semi -active" device with a
brake activated by an electrical switch and control system.
Finally, it may be "active", driven, say, by a hydraulic pump-
motor which conserves its energy, so remaining virtually
independent of the ship's power supplies. These various
degrees of sophistication result in improved performance and
flexibility at, of course, some extra cost. A weight of 2 per
cent of the ship displacement, with a value of GM/B of about
0.1 could provide a static heel of about -i-5 degrees (the so-
called "wave slope capacity"), and in waves of smaller slope
than this capacity, the active weight can produce reductions
in magnification factor to well below unity, virtually
eliminating roll.
Technical points raised
Norrbin (Sweden): van den Bosch's paper is interesting and
very clear. It is perfectly appropriate to have such a paper
read before an assembly of specialists, most of whom are not
from this branch of the profession. It will help to dispel from
the mind of many ship owners and ship operators that belief
in magic formulae, which from time to time is encouraged by
patent specifications.
Unlike the U-tubc type of passive tanks, the free surface
tanks mainly depend on energy losses due to flow discon-
tinuities to achieve that degree of damping, which is necessary
to avoid excessive tank liquid motions at resonance as well
as to create, at all rolling frequencies, an out-of-phase-of-heel
resisting moment high enough to even out the two response
maxima associated with the two-degree-of-freedom system.
These flow discontinuities may be initiated by a sudden
increase of channel width or by the formation of a "bore" or
"hydraulic jump" — "Wasserstoss" — in the shallow flow over
the tank bottom. The flow velocities within the tank are so
small that viscous damping will then be of second order. As
a consequence, scale effects will also be small.
The oscillating motion of water particles in a free surface
tank of moderate depth, h, which is forced to roll at resonance,
takes place along lines of U-form near to the sides and
bottom of the tank, and along an almost straight line parallel
to the bottom on the surface at the centre of the tank. Still,
the period of the standing wave is with a good approximation
given by the time taken for a wave on depth h on an infinite
surface to travel twice the width of the tank. Especially the
celerity of the shallow water wave is equal to Vgh, from
which the suitable tank depth h is governed by the relation
b2
h = — a»\ as given in the paper. It will be noticed that the
water particles of the ideal shallow wave move back and forth
with equal velocity parallel to the bottom, in which case the so-
called "critical depth" is equal to the water depth at the
critical speed condition. If the actual motion of the particles
is modified due to the end walls and due to a viscous boundary
layer along the bottom, the critical depth may occur at a
position below the surface. At the critical flow velocity a
"roller" is formed at the critical depth, initiating the forma-
tion of the bore. Viscosity may indirectly affect the bore by
changing the critical depth. It is also possible that surface
tension may introduce another source of scaling errors. Still,
Norrbin was not as pessimistic as was Field about the
application of van den Bosch's results to full-scale predictions.
At resonance the flow of water of a properly tuned tank is
lagging 180 degrees behind the roll-angle of the ship. In the
upper photograph of fig 5 in van den Bosch's paper, the ship
is seen heeled to starboard, say: water starts moving down-
slope rising the local depth at this side as the ship rolls back
to port. At a certain stage the conditions become critical in a
certain point and the roller appears. The bore front is now
travelling upstream, and the maximum damping moment is
reached in the upright position, where the rolling velocity
also has its maximum. From the second photograph one can
easily estimate two distinct levels upstream (to the left), and
downstream of the bore, which in principle make it possible
to calculate the loss of energy in the bore. Then it seems to be
possible to calculate the instantaneous damping coefficient of
the tank water, or a mean value during the cycle, and the
transverse mass transport in the tank might finally be des-
cribed by a second order differential equation with non-linear
damping, in which the forcing function depends on roll angle
and angular acceleration. Again, the roll-damping moment
due to this mass transport will then be a function of transport
amplitude and acceleration, and it will be possible to treat
the rolling in waves on basis of two simultaneous equations in
two degrees of freedom. Norrbin asked van den Bosch if he
thinks it would be feasible to evaluate his tank oscillation tests
along such lines.
It might be that the depth corresponding to a tank water
period equal to that of the ship will be too large for the
formation of the bore. In such a case it might be better to
choose a smaller width of the tank, making it a little longer
in fore-and-aft direction instead; alternatively, suitable
obstructions may be placed in the channel, creating "Borda
losses". Existing installations seem to rely on both types of
flow damping phenomena.
Five questions asked
Corlett (UK): van den Bosch's paper is most interesting and
is helpful to designers. Corlett awaited the comments of those
with a specialist interest with bated breath and it is apparent
that there is not complete quantitative agreement.
A practical passive tank must be insensitive to the natural
roll period or it will not be used by fishermen. Fortunately
the stability conditions rarely vary as much as is shown in
table 1 of van den Bosch's paper, at any rate with trawlers,
and fig 1 1 to 1 3 of his paper are thus most encouraging. The
relative insensitivity to the depth of water in the tank is
helpful provided the depth is kept less rather than more than
the median value. Safety depends upon this factor, and being
the predominant consideration, leads to the following
questions:
• How does one determine . when filling the tank unless
D
the vessel is stationary? Would this perhaps best be
done by using an auxiliary fixed capacity contents
tank?
• How noisy is the tank when operating in a con-
siderable seaway ? If it is really noisy, some fishermen
might not want to use it because of mistrust of this
apparently large amount of water rushing around
aimlessly in the tank.
• Can the out of phase component become displaced
and produce a dangerous in phase situation in the
event of the checked roll which can happen in small
ships? Corlett referred to a case where a roll is
starting and then the ship is checked by an odd sea
and then flung back the other way as sometimes
happens. He imagined the possibility in this case with
[188]
a relatively undamped tank that the water could
become in phase temporarily with the ship motion.
• What is the effect of a temporary list say when
handling gear over the side? It will be obvious that
the water will run to the lower side but, provided the
surface does not reach the top of the tank, in other
words that the list is not too big, will the tank continue
to operate efficiently and without danger?
• What modification to the amplification factor would
van den Bosch expect if bilge keels were fitted on the
ship in question?
The influence of underwater damping is critical and one
finds that the use of interrupted plate bilge keels is most
beneficial on these small ships. They must, of course, follow
the flow line which may not be easy to arrange. Corlett was
disappointed in the lack of papers concerning yawing and
broaching. This aspect of seakeeping in some waters more
than anything else separates the sheep from the goat. He
would be interested also to have van den Bosch's opinion of
the effect upon course stability and yawing of the presence of
the anti-roll tank in a small ship. In many cases, especially
with square plan view sterns for stern fishing, Corlett imagined
controlling the roll under quartering sea conditions, etc.
could be most beneficial, but, on the other hand, it could lead
to an increase in yawing as the quarters are dug into on-
coming waves.
In conclusion, Corlett thanked van den Bosch for a most
interesting paper. Any competent designer can design a tank
from the data given in the paper and Corlett looks forward
to an opportunity in the future of trying van den Bosch's
type of tank in a ship.
Author's reply
van den Bosch (Netherlands): In reply to Foussat, remarked
that every tank in the vessel, which is partially filled can be
treated along the lines set forth in the paper. If for a certain
tank the natural frequency is calculated and this natural
frequency appears to be much higher than the resonance
frequency of the ship, the only influence which has to be
taken into account is the loss of GM. When wt appears to be
much lower than o^, the influence can be neglected. When wt
approximates ^ the tank acts as an anti-rolling tank. When
a calculation is carried out, however, it will in most cases be
evident that the influence is immaterial, as the tank moments
are proportional to b3 and most fuel or ballast tanks have
a very limited width. When a large GM reduction is expected
because of the large deep tanks for instance, the GM reduc-
tion should be taken into account when deciding on a design
value for the tank.
Field suggested that the tank is "undamped" without
explaining exactly what is meant by that. When considering
fig 6 and 7 it is clear from the slope of the phase curve that
the water motion in the tank is heavily damped. Nobody
would doubt the damping of the breaking ocean swell on a
gently sloping beach and in the tank energy is dissipated in
the same way.
A theoretical treatment of the tank phenomena is given by
Verhagen and van Wijngaarden (1965). Although the theory
does not include viscous effects, the damping of the system
is clearly proved. Theoretical and experimental results show a
good agreement.
According to van den Bosch experience restrictions in the
tank may have a favourable effect only for relatively low GM
values, whereas, for the proportions of most fishing vessels a
flush tank without restrictions will give the best results or the
difference will be unimportant.
Field mentioned the work of Chadwick and Klotter (1954)
as a basic paper on the subject, van den Bosch did not agree
with this. The "Theory of Chadwick and Klotter" is in fact an
application of the general theory of oscillating systems with
two degrees of freedom, in which the motion is described by
two simultaneous linear differential equations with constant
coefficients, van den Bosch believed that this theory is
absolutely inadequate to describe the combined ship-tank
system, because the motion is not linear and the coefficients
are highly dependent on the frequency.
Contrary to the remark of Field, it is believed that scale
effects are immaterial. This is substantiated by experiments
not mentioned in the paper and by the theoretical approach
of Verhagen and van Wijngaarden, and it is in accordance
with the remarks of Norrbin.
van den Bosch did not see much sense in stating the
significant wave height or wave slope, as this suggests that
there is a direct relation between the significant wave height
or wave slope and the significant roll amplitude. As the
rolling ship responds only to wave moments in a rather
limited frequency band, the motion has no bearing on the
waves outside this range which, however, do contribute to the
significant values of the height or the slope.
Anyhow the significant wave height of the model spectrum
corresponds to about 2.7 ft (0.8 m) full scale and most of the
wave energy was concentrated in the important frequency
range.
As already stated in the paper the aim of the tests was not
to show the model under extreme conditions but to check
the validity of the applied procedure.
Goodrich is thanked for his favourable comments. He
suggests that given an adequate length of tank a dramatic
reduction in the roll response can be achieved. This has been
brought into practice in the case of bulkcarriers which have
excessive large GM values in ballast condition. By filling one
hold with sea water to a predescribed level a huge anti-
rolling tank is created, rendering the ship as steady as a rock.
Several contributors, Foster, McNeely, Nickum reported
cases of installations which behaved unsatisfactorily. Often
the causes can be traced to bad design or improper handling.
Work on this subject is often hampered by the tendency to
emotional judgment.
Nonweiler and Du Cane suggest that there existed "some
lack of precise tuning between tank and ship". Presumably
this remark concerns the fact that the "cross points" between
the characteristics of the ship with and without tank, did not
lie at the same height as shown in fig 14. This consideration
originates from the double pendulum theory. As already said
in connection with the contribution of Field, van den Bosch
believed that this theory is inadequate, because of the frequency
dependence and the non-linearity of the quantities concerned.
van den Bosch disagreed with the use of the significant
wave slope as a measure of comparison, as already mentioned
in the reply to the contribution of Field.
The remarks of Nonweiler and du Cane about moving a
solid weight are interesting. The moving weight certainly
offers possibilities which have been neglected, but van den
Bosch did not know of any installation in use nowadays.
Norrbin is thanked for his help to dispel the belief in magic
formulae, and for his contribution concerning scale effects.
His views are in agreement with van den Bosch's observations.
£-+ % It
For very high ' ratios the waterdepth in the tank has to be
D
so high that the bore is formed only in a very limited fre-
quency range, in that case this bore principle is not usable
and perhaps some other system may be more fit to cope with
this situation.
van den Bosch did not believe that choosing a tank of
smaller width will be the solution as the moment amplitude
[189]
is to a large degree controlled by the width of the tank and
stiff ships need large stabilizing moments.
In reply to the questions of Corlett it was stated that the
filling of the tank to the right level is not difficult. For instance
an athwartship partition bulkhead with a sluice operated
from outside, may divide the tank into two compartments,
one of which having the desired volume. When this supply
tank is filled to the overflow the sluice is opened and the
water is distributed over the two compartments. During full
scale measurements van den Bosch and his collaborators
used a calibrated flow meter in the feed-pipe of the tank.
The noise of the tank can be damped considerably by
fitting a perforated plate on the innersidc of the frames, with
about 75 to 80 per cent perforation.
In full scale and in model the response of the tank to
irregular motions appeared to be almost immediate. As the
tank is certainly not "relatively undamped" the danger that
the tank water will get in phase temporarily seems not great.
Moreover when the amplitude of motion increases the phase
curve flattens, indicating that the damping action spreads
over a much larger frequency range.
A temporary list will, if not too big, not much influence the
behaviour of the tank. When the list is so great that the water
remains mainly at one side, the efficiency of the tank is
presumably less than in the upright position. The tank does
not present any danger then because the effect will be reduced
to the influence of the momentary free surface on the GM
value. The loss of GM has to be considered in the design
stage.
The model in question was fitted out with bilge keels.
Knowledge about actual amplification factors at sea is very
scarce. It appears that the short-crestedness of the seas brings
about seemingly low amplification factors.
There is not much known about the coupling and phases
of the ship motions in quartering seas and certainly there is
not much known about the interaction of the tank with ship
motions other than roll. Because of this lack of knowledge
it is not advisable to place an anti-rolling tank in the ends of
the vessel. If the tank is placed amidships it can reasonably
not have much influence on yawing or course stability.
Also the yawing motion cannot have an appreciable influence
on the tank action.
CATAMARANS AND OTHER UNORTHODOX
CONFIGURATIONS
History of "Cats"
Chapelle (USA): MacLear's conservative presentation of the
catamaran is unusual where this subject is concerned. In his
short introduction he may have given the impression that
powered catamarans have been few in number. This impres-
sion is not correct. Sailing catamarans of vessel-size were
built in England in the Restoration Period and have appeared
in number since that time, of course. Power catamarans
appeared in the 1790s when Miller built his manually-
powered and sailing catamaran, with a paddle-wheel between
the hulls, which he brought to Sweden. Here he proposed a
man-of-war of this design to the king. The king referred the
proposal to Chapman, the great Swedish naval architect of
the 18th century, who condemned the plan. Fulton's steam
battery sometimes called Demologos, built at New York in
1815, was the first steam man-of-war and a catamaran.
A Hudson River steamer, having two cigar-shaped hulls was
tried in the 1840s. A cross-channel steamer-catamaran was
built in England later in the century. There were a large
number of smaller catamaran steamers, ferry-boats and river
craft, built in this century. In the 1840s the catamaran snag-
boat was introduced on the Mississippi, propelled by a
paddlewheel between the hulls or by side paddlewheels.
It must be admitted that the majority of catamaran steamers
were intended to be very fast. In this, most of the promoters
were disappointed. In many of these vessels the advantages
of the catamaran defeated the project. The great deck space
obtainable tempted the builders to add great accommodations
and as a result the displacement became heavy to support this
loading.
During the last war the German Army utilized catamarans
as tank transporters; model tests of these were carried out
in the Hamburg tank, Chapelle believed. Some of the boats
built on these test data were air-propelled, others screw.
Their speed was not very satisfactory, nor did they steer well.
In general, Chapman's comments seemed still sound; the
catamaran is best employed as a small, very light craft.
Displacement and draft determine manoeuvrability to a very
marked degree.
Steering by use of twin screws seems wasteful. Chapelle had
proposed that the twin-engines of the "outboard installation
introduced before the last war" be used. These had drive
arrangements so that the propeller steered the vessel as in the
ordinary outboard engine. Linking these together would give
more precise steering. The need for a constant loading in
catamarans remains the chief objection as a commercial
vessel.
In net fishing, where the deck space of a catamaran would
be her great advantage, quick response in steering will be a
necessity when the vessel is working close to her nets. So far
this problem is not wholly solved.
Experienced comment
Adam (France): Wanted to use his 15 years' experience as a
yachtsman on multi-hulled boats, to make some comments
on the catamaran paper by MacLear. Firstly, waves hitting
the central platform might cause very severe impact problems.
Secondly, if their rolling motion is reduced, compared to
mono-hulled boats, the high initial stability of catamarans
brings about two disadvantages (1) brutal movements
causing dangerous strains in the boatstructure; (2) rapidity
of the motion which might create seasickness as well as or
better than ample slow rolling. Lightness of construction is
the best way of overcoming these disadvantages. It can be
more easily achieved for yachting than for commercial
utilization, the latter implying carrying of goods or fish.
Takehana (Japan): Agreed with MacLear's opinion on the
advantages of catamaran fishing vessels. In Japan there are
now two steel catamaran ferry boats. Takehana thought
that smaller fishing catamarans under 20 GT and pleasure
boats, constructed of fibre glass reinforced plastics could be
introduced in the near future. This type of vessel should be
well suited for catamarans for the following reasons:
• The draft of a catamaran hull can be easily adjusted
to prevent excessive lee way of the light ship and
retaining good stability.
• FRP construction is particularly suitable to make
extremely light and strong hull structures required for
catamarans *and also to reduce construction costs
below those for wood and steel construction.
Takehana believed that a combination of these new hull
types and new construction materials would result in more
seaworthy and more economical fishing vessels.
Recent study
Hamlin (USA): The catamaran has been given serious study
for large craft only since the days of World War II. Perhaps
the first to recognize its potential advantages was Gar Wood,
who, during World War II, began the design and supervised
construction of an experimental catamaran for the US Navy.
[190]
The War ending before its completion, he purchased the
vessel from the Navy and completed it at his own expense.
188ft (57.4m) Loa with a 40ft (12.2m) beam, the vessel
was reportedly capable of speeds of 26 knots in rough Gulf
Stream seas. She eventually disintegrated at sea, presumably
because of inferior war-time materials used in her construc-
tion.
More recently, the catamaran has attracted considerable
attention in USA, primarily for marine research and survey
work, but also for yachts and fishing vessels. A 70 ft (21.4 m)
x28ft (8.5m) catamaran trawler is currently undergoing
trials. The most ambitious catamaran in USA to date is a
278ft (85m) x 105 (32m) deep drilling vessel of 5,100
deadweight tons with 3,000 hp giving a service speed of
12 knots; she was designed by Friede and Goldman (1965).
Japan is another major source of catamaran activity.
There, the Nippon JCokan KK has been building steel
passenger and vehicle ferries up to 136 x 40 ft (41 .5 x 12.2 m)
with larger ones projected, fig 7 and 8. Several are in use on
the rivers of Thailand, others are crossing between Japanese
islands.
This brief sampling of some of the worldwide activity in
catamarans should encourage fishing interests to examine
carefully the advantages accruing from the twin-hull con-
figuration. Based on a comparison of single-hull and cata-
maran craft of equal displacement and hence assumed equal
cost, some of these advantages are (Hamlin, 1965):
Fig. 7
• Approximately 50 per cent more deck space than a
conventional vessel, enclosed and open areas com-
bined, in efficient, rectangular shapes.
• 5 to 10 per cent greater cruising speed for a given
horsepower or, conversely, a reduction of about
15 per cent in horsepower for a given speed which
translates into a proportional increase in cruising
range and an increase of approximately 30 per cent
in reachable fishing area.
• Reduction of roll angles by up to 50 per cent or
better, including elimination of rhythmic rolling,
with a reduction of average accelerations and no
significant increase of maximum accelerations.
• Ability to handle large loads (up to 10 per cent or
more of the displacement) without dangerous heeling
or trimming effects.
Structurally, the catamaran seems to offer no problems, at
least within the size range of most fishing vessels. Calculations
(Mandel, 1962) indicate that, in catamarans up to 4,000 tons
displacement, scantlings adequate to meet local strength
requirements arc adequate for overall structural strength
requirements. As an added feature, the hull form may be such
as to permit the extensive use of flat plates and simple stock
shapes for structural members.
There are some important questions about catamarans
which still need clarification. Perhaps the most important
from the fisherman's point of view is how his fishing gear
should best be handled. Should he shoot and haul over the
stern, over one side, or through a central hatch? Should he
tow from each quarter, from a central point at the stern, or
from some point forward of the stern? Is it possible to avoid
hauling gear on deck by use of a hydraulically operated
platform on to which the catch could be landed under water?
Hamlin suggested that these questions might be answered
most efficiently and thoroughly by use of a man-carrying
model catamaran. Such a vessel could be rigged with simulated
lishing gear of any type, quickly and inexpensively, and such
gear could be tried out in actual fishing operations. Towing
tank testing will provide valuable information on horsepower
Fig. 8
Fig 7 and 8. A vehicle and passenger ferry, 136 X 53 ft (41.5 X 16.2 m) designed and built by Nippon Kokan KK
[191]
\ ,
X
/
-*^
V ^ n^f -' i r~ A
•* I7 l l \
\ S'
\ ?
r\
•ii
? 1
p^l
j- ::_ -XH2 /
- j
/•»*'
I 1
jm MM It
Fig 9. /4 catamaran oceanographic research vessel* 149 X 48ft (45.5 X 14.6 m), by Hamlin. Speed approximately
13 knots. A submarine is stowed in the centre well
requirements etc., but cannot adequately answer the questions
stated above.
The catamaran concept is relatively new in its application
to modern seagoing usage. It is therefore important that the
body of data on the type is augmented as rapidly as possible.
Fig 9 shows a proposed 149 ft (45.5 m) oceanographic
research vessel, and fig 10 a proposed 120 ft (36 m) passenger
catamaran.
Fig JO. A passenger catamaran, 120 x 45ft (36 X 13.7 m\ by
MacLear and Harris. Forty passengers, ten crew, J I knots cruising
speed.
New study of an old form
Melchert (Switzerland): It is amazing that catamaran craft,
which figure among the oldest constructions in the history of
ships, have been studied according to marine techniques
only in the last few decades. Certainly they have a bigger
weight and higher building costs than those of a conventional
ship of the same deadweight. However, they have so many
advantages that they will certainly have a wide field of applica-
tion in the near future. It is therefore a real pleasure to read
how these promising advantages have been pointed out by
MacLear, especially from the viewpoint of catamarans as
fishing craft.
There was one point which Melchert wanted to add to the
questions of structure and drag. The firm of consultant naval
architects, where he works, recently investigated the pro-
blem of how the open framework built up by the two hulls
and by the wing could be closed below the water in order to
make the construction stronger and more rigid. These
endeavours led to a successful solution which has since been
patented. In general, the wing structure, and especially its
connection with the hull, has lo be extremely strong and
rigid. However, when a structural connection between both
hulls is fitted, the stresses in the wing girders are considerably
reduced. The problem was how to fit such a girder below the
waterline so that the least possible increase in resistance
would occur. As against the expectation of the experts for
structural questions, this problem was solved by the hydro-
dynamic experts in such a way that not only was there no
increase in drag but, on the contrary, a considerable reduc-
tion. It should be recalled that the bow waves of both hulls
are superimposed upon each other within the channel created
by the inner board walls of both hulls. At the point where
their crests meet, a so-called fountain appears, and in the
range beyond this fountain the divergent wave system
disappears and a whole wave energy builds up an extremely
pronounced transverse wave system. This wave system is very
similar to so-called two-dimensional waves. Now Kelvin has
already shown that any two-dimensional waves can be com-
pletely eliminated. He has even calculated the form of a ship
with infinite breadth but finite length which would produce
no free waves at all.
Analysing the wave system
Remembering these facts, the hydrodynamic experts started
to analyse the wave system of a 10 knot catamaran craft of
95 ft (29 m) length, and they concluded that a similar wave
system with reverse amplitudes could be produced in the
following ways:
• introducing a cylindrical bar of a certain radius
between both hulls at a suitable position
• a more exact adaptation of the secondary wave
system could be achieved with certain elliptical or
similar forms
[192]
/•'(IT //. /I tf/wfcr H'/Y// an aerofoil profile for reinforcement of a catamaran
• a similar effect could be obtained by introducing a
girder with an aerofoil profile, the shape and the
position of which have to suit the original channel
wave profile (see fig 1 1 )
• adaptation of the secondary wave system to a variable
channel wave profile, which might become necessary
when the craft sailed at variable draught, could be
achieved by a suitable control of the angle of attack
or by lifting control through a high lift flap or by
telescopic suspension.
Of these possibilities, the high lift flap seems to be the
most appropriate from the structural viewpoint. Good results
can, however, also be achieved with completely fixed aerofoil
connections when their position and angle of attack are
selected on the basis of compromise for the varying draughts.
The secondary wave system produced by these wave-
making bodies cancels to a gretU extent the channel wave.
In the case of the 10 knot catamaran craft, there was also the
advantage that, while the hollow of the channel wave touched
the propeller tips at full speed in the original design, after
application of a wave-cancelling connection, the water level
was raised considerably at the aft ship so that the propellers
were well immersed. As compared with the resistances of the
original catamaran craft, the application of the wave-
cancelling connection reduced the resistances by 20 per cent.
The drag curves versus speed had a point of intersection at
about 8 knots, and above that speed the gain increased
continuously and had still a considerable positive gradient at
10 knots. Unfortunately, the model was on such a big scale
that the model basin could not make measurements at
higher speeds, so that the highest possible improvements at
optimum speed could not be determined, though it is quite
clear that this maximum improvement would have been far
higher than 20 per cent.
It would certainly be possible to apply more than one
connection between both hulls, provided that their own wave
systems are correctly adapted to the original channel waves.
This would permit the most effective frame construction to
be made and would allow the wave-making bodies to be
lowered, which would be of considerable advantage when
sailing in stormy seas and also from the viewpoint of ship's
structure.
In view of the above advantages, it seems to be advisable
to make use of this possibility of constructing better catamaran
craft.
Imaginative appeal
Grigore (USA): MacLear has made an outstanding technical
contribution towards bettering the performance and pro-
ductivity of the world's small craft fishing fleet. The acceptance
of the catamaran hull as a floating work platform is beginning
to dawn upon the imagination of the prospective user. It has
been too long in coming, even though some of the delay has
been keyed to the progress of design, metallurgical and
welding developments.
As one of the initiators of the US Johnson, and as the
project engineer for the development and test of amphibious
vehicles of the US Government, Grigore felt he could discuss
with authority the subject of catamarans and of negotiating
surf zones.
Of the catamaran, if it is not properly designed and hydro-
dynamically model tested, it can result in being more of a
"goat" than a boat. This almost happened to the US Johnson
insofar as her anticipated versus actual water speed was
concerned. The project engineer had been overruled by civil
engineer management to wit : That sufficient know-how already
existed about small boats, and that one of the better cata-
maran designers was conducting the naval architecture of the
boat, therefore no funds should be expended to prove the
hydrodynamic adequacy of the hull configuration. However,
in every other respect the US Johnson completely fulfilled her
requirements and upheld the judgment of her sponsors (see
Military Engineer Magazine, May-June 1962). She also
brought many converts to her favour. Insofar as beaching
the Johnson, this has been done frequently with no effect
whatsoever on either hull or the underwater jet propulsion
system. Since surf is not a predominant factor in the Great
Lakes, very little surfing experience could be gained with the
Johnson. But this is not to say that it was desired to do so or
was considered necessary.
Grigore considered that attempting to run the surf and to
ground with any catamaran should best be left to amphibious
vehicles of the surfing variety and that MacLear may be
unconsciously trying to connect the romantics of Polynesia
into the operation of catamaran fishing boats which absolutely
have no need or place in a surf environment. Cirigore could
not stress this point too emphatically. It is totally unsafe for
any inexperienced person to be caught in the powerful
clutches of a plunging surf or the treacherous secondary
currents, and undeterminable beach gradients which exist
between the surf zone and beach line.
What Grigore really believed was that MacLear intended
in lieu of surfing a catamaran fishing boat is actually beaching
it in a calm water area where sufficient tidal range exists to
bare the entire hull for maintenance purposes. Many such
areas exist without the need to recourse to jeopardizing life
and property unnecessarily in a surf zone.
Lastly, it is suggested that the co-operation of the USSR
be solicited to obtain their experience with a self-propelled
300 ft (91 m) catamaran hull built for cargo transport on the
Volga River and Black Sea routes.
Author's reply
MacLear (USA): Agreed with Adams concerning the fast
motion of catamarans but would like to add that double-
ended catamarans should be avoided to slow down pitching.
He also agreed with Chapellc that quite a few owners had
been disappointed in the speed performance of catamarans
but aluminium construction should help reduce this problem.
He was in complete agreement with Takehana in respect of
new materials, such as aluminium, fibre glass or plywood etc.
[193]
HYDROFOIL CRAFT AND HOVERCRAFT
Hareide (Norway): Since 1960/61 four hydrofoil boats have
been trading regularly as passenger vessels in Norwegian
waters. Two of them are PT-50, certified for 100 passengers
between Stavanger-Haugesund-Bergen. The remaining two
are PT-20, certified for 60-64 passengers. Two more PT-20's
started trading in 1963.
The larger vessels cross two open stretches of sea of 9 to
10 miles, although both stretches are partly sheltered by
islands and shoals. This route and such unsheltered stretches
have so far been the limit to which regular trading has been
permitted. The smaller vessels operate almost wholly within
sheltered waters.
The vessels were initially only allowed daylight operation
on the foils and only in May through September. Based on
the experience gained, winter trading in ice-free waters has
later been permitted. Likewise trading on the foils in what is
termed "civil twilight" has been allowed. This permit was
for the aforementioned route Stavanger-Bergen, subject to
the condition that the owners at one of the open stretches
provide a suitable port of refuge with arrangements for
transport of passengers to the next regular port of call. The
trading is at all times subject to the Master's discretion as
regards weather conditions, but maximum permissible wind
force and wave height have been stipulated as mentioned
below. Experiments in night operation on the foils have been
carried out. The question of such operation will be re-
considered in early autumn 1965. The authorities arc aware
that such operation is allowed in at least two heavily traffi-
cated areas in other countries and that night traffic at a
certain minimum distance from the coast has been allowed in
other cases. This last question has not been brought up in
Norway.
As to other general conditions the following may be of
special interest:
Hull as accepted by the classification society, the Norwegian
Veritas. Frequent surveys of bottom, foils, propellers, etc. on
account of weaker construction than conventional vessels and
cavitation problems.
Engine of 'Tail way type". A lighter construction than the
usual marine type. Cruising speed for PT-20 about 32 knots
and for PT-50 about 35 knots. Fuel tank capacity about
10 hours at full speed.
Stability. Damage and intact stability calculations as for
conventional passenger ships.
Life-saving appliances. As it is virtually impossible in passenger
trade to have lifeboats on board hydrofoil craft, inflatable
life-rafts have been accepted. Lifejackets etc. as usual.
Navigation and communication equipment. Usual require-
ments for other vessels in similar trades. In addition two-way
radiotelephone and radar. Regular radio contact with shore
stations to be maintained. Without first-class radar equipment
and radar observer, operation on the foils in darkness is not
sufficiently safe in coastal or congested waters. In this con-
nection it must be taken into account that because of their
high speed, hydrofoil boats will encounter about twice as
much traffic as ordinary vessels. If Hareide was correctly
informed however, radar is not at present required on hydro-
foil craft operating at night in New York harbour.
Sea and wind conditions. Wave height below 6ft (1.8m).
Maximum wind strength 6 Beaufort scale.
Usability for fishing purposes. The operation of hydrofoil
boats for passenger service has been subject to stringent
regulations as regards sea, weather and temperatures,
visibility etc. Some alleviations might be expected for the use
of the craft as a fishing vessel, but the boat is not built for,
and could presumably not be used in such rough sea and
weather as fishing vessels operate in outside the Norwegian
coast. In this connection one should take into account that
in order to keep the weight sufficiently down for the hydrofoil
craft to retain its ability to operate on the foils, it is necessary
to exempt the vessel from the conventional requirements as
regards structural strength, shell thickness etc. It will likewise
be impracticable for the craft to use dorys or other working
boats (even life-boats will be difficult to carry), and heavy
fishing gear such as trawls and purse seines. In addition such
gear might cause serious damage to the vessel which would
have to operate on the hull while fishing. The foils will
presumably also hamper or make impracticable the use of
modern fishing gear.
Fishing with trolling lines would likewise have to be
performed at low speed, that is on the hull. Quite apart from
that, such fishing as well as the use of longlining and similar
fishing tackle, could hardly be profitable considering that the
hydrofoil boat itself costs more than a fishing vessel of the
same size furnished with trawl, purse-seines or other modern
fishing gear. The high building and operating expenses will
of course reduce the usability of the hydrofoil boat in all
kinds of fishing.
The only advantage of the hydrofoil boat in the fishing
industry seems to be the rapid passage to and from fishing
grounds, weather permitting. Under such conditions she
might be used working in a team with conventional fishing
vessels in the near coastal regions for the transport of special
kinds of fresh fish or other sea food. With the present con-
struction of the ship, the loading will however at the best be
a cumbersome process.
In conclusion one might say that the hydrofoil vessel at
present does not seem to provide practical possibilities for
improved efficiency of the fisheries in waters similar to those
adjacent to the Norwegian coast. The outlook for the hydro-
foil boats in sports fishing seems more promising however,
especially as regards smaller versions than the PT-20.
Two types of hovercraft have been allowed for test opera-
tions in passenger trade in Norway, viz. the SR-N5 and
SR-N6.
Dimensions of SR-N5:
Length overall . . . 39 ft 5 in (1 1 .9 m)
Breadth . . . . 22 ft 9 in (7.0m)
Height (from lower lining of
shirt) . . . .16ft (4.9m)
Maximum total weight . 15,000 Ib (6,804 kg)
Weight of craft fully equip-
ped including fuel . . ll,0201b (5,000kg)
Carrying capacity . . 3,980 Ib (1,804kg)
Dimensions of SR-N6
Length overall .
Breadth ....
Height ....
Maximum total weight
Calculated weight of craft
fully equipped including
fuel .... ll,6301b (5,280kg)
Carrying capacity . . 8,370 Ib (3,800kg)
Fuel tank capacity when trading at full speed of about 60
knots is for 34 hours. The craft shall not be used in passenger
trade as mentioned if the wind force may be expected to
exceed 20 knots (about 10 m/sec) or if the wave height may be
expected to exceed 5ft (1.5m). The speed in combination
with sea and wind conditions shall not subject the hovercraft
48 ft 5 in (14.8m)
23 ft (7.0 m)
17 ft 4 in (5.3 m)
20,000 Ib (9,080kg)
[194]
to a vertical acceleration greater than 2 g. The craft shall be
hoisted up for inspection every 30 hours. Surveys are to be
frequent.
The construction of the craft is in accordance with that of
an aircraft rather than a ship. The skin (shell) is of paper
thickness. The characteristic feature of the hovercraft is that
its general operative purpose is to move while hovering
freely in the air at a limited height. Even though it is not
designed to move in water nor on land like ordinary vessels
or vehicles respectively, it can in an emergency stay afloat
and move at slow speed. It can also move on land or ice
under certain circumstances.
It follows from the inherent qualities of the craft, and its
method of operation included its high speed, that it has
inferior manoeuvrability, susceptibility to wind effects and a
high level of noise which makes it practically impossible for
the crew to hear sound signals. It has therefore been considered
necessary to provide special rules for the steering, signs and
signals of hovercraft. Here it may be sufficient to mention that
the hovercraft when airborne shall keep well clear of vessels.
When waterborne it is regarded as a power-driven vessel.
Operation is allowed only in daylight and clear weather.
Conditions for trading as a non-passenger ship have not been
considered. It might be added that one SR-N5 capsized
during a highspeed turn in Norway in April 1965. The main
reason was supposed to be that the longitudinal stability
keel had been torn throughout a considerable part of its
length. The keel has since then been strengthened. Another
SR-N5 capsized a little later in San Francisco during a
similar turn mainly due it was supposed to lack of experience
of the driver. Short modifications to prevent such "plough-in"
have been incorporated in the vehicles.
Apart from its speed, the greatest advantages of the craft
seem to be that it may navigate outside ordinary ship lanes
and may land on beaches or further inland if the circumstances
are favourable.
Further comments on the hovercraft seem unnecessary in
this connection, as it will appear from the above that the
present type of hovercraft is even less suitable than the
hydrofoil boat for fishing purposes. It seems doubtful if it
could be used even for sports fishing. It might, however, be
used for transport purposes where the freight charges are of
minor importance. These charges will presumably be higher
than those of a hydrofoil (and consequently of conventional
ships) as the hovercraft at least at present costs more to build
than a hydrofoil of the same capacity and trading expenses
are higher.
As will appear from the above, there is as yet rather scant
experience concerning hydrofoil craft and especially as
regards hovercraft. In addition both types of vessels may be
considered still to be in the development stage. The problems
in connection with them must be kept under constant observa-
tion in order that the rules and regulations may be adjusted
to further development and experience. Such changes may
of course also affect their usability as fishing vessels.
MacLear (USA): Hydrofoil boats have had considerable
difficulties with fast wearing out of their engines. This is
because present-day gasoline and diesel engines have too low
a ratio of horsepower to weight, and gas turbines are still too
expensive to buy and operate. This latter may soon change
however and make hydrofoils more economic as passenger
vessels. It would however seem that it will be a fairly long
time before they are used for fishing.
THE RUSSIAN POPOFFKAS
Idea Worth Trying?
Sutherland (USA): In the late 1860's, Vice Admiral Popoff,
of the Imperial Russian Navy, was apprised of a need for
additional coast defences. He is said to have believed:
". . . fixed forts require immense foundations, which prove
to be extremely costly, and, notwithstanding their cost,
sometimes weak. Besides, some points along the coasts,
known to be of great strategical importance, have been so
far left unfortified, because of the impossibility or difficulty
of building such foundations. Finally, fixed forts are dis-
advantageous, simply because they arc fixed." Floating
batteries offered a solution to this problem. Popoff knew that
by using a circular form, the greatest area and volume could
be enclosed by a minimum weight of hull steel, and the
heaviest guns and armour could be carried. Depth of water in
the planned operational area limited ship draft to about
13ft (4m) and the available building and drydocking
facilities limited the diameter. (Further discussion in
Part VI).
Popoff's circular ironclad design was model tested by
William Froude at the Admiralty Experiment Works,
Torquay. At least two circular ships were built, the Novgorod
of 101 ft (31 m) diameter, with 11 in (28cm) armour and
mounting two 28-ton guns, was completed in 1873. The
Vice Admiral Popoff, of 121 ft (37m) diameter, with 18 in
(45cm) armour and mounting two 41-ton naval guns, was
finished in 1875. Both were of very low freeboard (only 18 in
or 45cm), of approximately 13ft (4m) draft, and were
propelled by 6 propellers, at a maximum speed of 7 to 8 knots.
They were slow, wet in a seaway, lacked directional stability,
and were hard to steer. The resistance to propulsion of the
pure circular hull was some 4 to 5 times as great as that of a
conventional hull of the same displacement at 8 knots.
Novgorod and Vice Admiral Popoff had virtues as well as
faults. Goulaeff (1876) describes the circular ironclads,
comments as follows about Novgorod; "Her stability was
immense, and her steadiness as a gun platform is greater than
that of a ship of any other form. Owing to the great beam,
low freeboard, and perhaps also to the flatness of the bottom,
the rolling of the Novgorod is very limited indeed, and it
seems to me that in the present state of the subject, instead
of entering into the discussion of any theoretical hypothesis
on the behaviour of a ship, whose resistance to rolling motion
and other conditions are widely different from those of
ordinary shaped ships, it would be preferable to state only that
the greatest angle of roll which was observed while 1 had the
pleasure of steaming on board the Novgorod for several days
at sea, during the Equinoctial gales, never was such as to
expose her lower edge of the side armour — the instrument
for measuring the angle of heel showing at that time that the
arc through which she was rolling was 6 or 7 degrees; and
this was in waves in which ordinary ships steaming the same
course as Novgorod were rolling very heavily . . ."
Sir Edward Reed said in the discussion: ". . . having made
several passages in this Novgorod, over the Black Sea, one of
them in eminently rough weather, I was gratified to find that
I made those passages with the greatest possible comfort . . .
and when the waves were running to considerable height . . .
you sat in the cabin in the deckhouse with the ship in a state
of almost absolute tranquillity no rolling worth mentioning
to trouble you, and scarcely any pitching".
The success of Popoff's design is perhaps best summed up
by another comment Reed made: kt\ should like to ask those
gentlemen who spoke so strongly against this class of vessel,
if they will be good enough to refer me and this Institution
to any vessel whatever in the whole world, except the Novgorod
which carries at from 7 to 8 knots armour 1 1 in (28 cm)
thick, and two 28-ton guns. There is no other vessel in the
world that docs that." Later that same year, Vice Admiral
Popoff considerably improved upon the Novgorod's charac-
teristics.
[195]
G2
Result of tests
It was obvious that by modifying the circular form to
provide fine entrance and run, eddy-making at moderate
speeds could be significantly reduced and total resistance to
propulsion decreased. After extensive model tests, conducted
under the guidance of Tideman, Chief Constructor of the
Royal Dutch Navy, the Russian Imperial yacht Livadia was
built in Great Britain by J. Elder & Co. of Glasgow, to
Admiral Popoflf's design and specifications. Explaining the
near-circular form adopted for Livadia, Goulaeff (1881)
stated: "As the Livadia had to be a yacht, it was decided to
make all her qualities subordinate to the utmost safety of
navigation, and to the utmost comfort depending on the
possible limitation of rolling motion at sea, and on the
provision of spacious apartments with a luxurious amount of
light and air/' In further support of the Livadia design,
GoulaefT continued: "If I tell you now that the Livadia does
possess, in addition to a double bottom, three sides, spaced
not less than 6ft (1.8m) apart ensuring her against all
possible contingencies of stranding or collision in a degree
not possible to be attained in any other ship; if 1 tell you that
her steadiness at sea, as tested in a storm last autumn in the
Bay of Biscay, has proved to exceed anything that has yet
been realized; if I further tell you that this ship carries
extensive palaces, which are pronounced by many competent
critics and by thousands of visitors who have inspected her,
to excel, in the size of their apartments, light and air, any-
thing one can expect to meet afloat; and if I add to this that
her speed proves to be 15 j knots instead of 14, as intended,
then perhaps I may not be thought too bold in believing that
the ship commends herself to your special attention/'
Livadia was truly a floating palace, 230ft (70m) long, by
150ft (45.7m) beam, by 7ft (2.1 m) draft, by about 4,500
tons displacement, propelled by 3 screw propellers at a trial
speed of nearly 16 knots.
Official trials of Livadia were conducted after about 4
months in the fitting-out basin without her bottom neither
cleaned nor painted. Goulaeff (1881) and Reed (1881) quote
performance figures and Livadia' s performance is compared
with that of British naval vessels. For instance, the following
tabulation appears. Both Penelope and Orion were blunt-
bowed ironclads.
Ship
Penelope
Livadia .
Orion
Livadia .
Another comparison is given of Livadia and HMS Jris.
The latter ship made a maximum of 18.6 knots on official
trials, at a displacement of 3,290 tons, requiring 7,556 IMP.
Iris was 300ft (91.4m) in length and had an immersed
midship section area of 700ft2 (65m2). Livadia** midship
section area was 1,000 ft2 (93 m2).
Displace-
JHP
Speed
ment
4,394 tons
4,703
12.7 knots
4,420 „
4,770
13.0 „
4,700 „
4,000
12.0 „
4,720 „
4,500
12.5 „
IHP per ton
displacement
IHP per of
mid-area
Irk
2.28
10.71
Livadia
designed as built
2.35
10.50
2.79
12.35
On the first day of official trials, Livadia had a mean speed,
maintained during 6 consecutive hours, equal to 14.83 knots,
with an indicated horsepower of 10,200. On the following
day, on the measured mile, the ship attained a mean speed of
15.725 knots, with an indicated horsepower of 12,354. At
moderate speed of 12 to 13 knots, not much penalty was
exacted for Livadia's unusual form. At higher speeds, it has
been variously estimated that Livadia required from 1.4 to 2
times the power that would have been needed for a ship of
conventional form.
Commenting on Reed's (1881) paper about Livadia' s
resistance to propulsion, Froude said: "Certainly it is not
prima facie a bad form so far as wave-making resistance is
concerned because all the displacement which is in the middle
of the ship is almost in the condition of a submerged body —
it is almost out of the reach of the surface of the water.
Provided that you keep clear of the eddy-making, which is
the great bane of the original Russian round-ship designs,
there is no reason why you should have a very excessive
resistance/' Earlier, discussing Goulaeff 's (1876) paper,
William Froude said: "There is ... rather a curious fact in
relation to the resistance of these ships ... up to the highest
speed at which we drove them . . . their resistance was just as
the square of the speed . . . you might infer from that that there
would be some gain in pressing these ships to a high speed/'
It is other qualities than speed which is interesting in Livadia's
form, and justify further investigations. For a ship that is to
remain on station for long periods, one might be more
interested in minimum roll with a long rolling period, sea-
kindliness and comfort, and the large and usable deck areas
obtainable on minimum displacement.
Bay of Biscay test
His Imperial Highness the Grand Duke Constantine
accepted delivery of Livadia from the builders and made the
delivery voyage from Great Britain to the Black Sea, accom-
panied through the Bay of Biscay by several important
British guests. One of the guests, Mr. W. Pearee, then
managing director of the shipbuilding firm, said: "this ship
has the steadiest platform of any in the world . . . this ship
passed through the Bay of Biscay during a week when it is
recorded that more ships foundered than in any week during
the whole of last year, you will understand that she must be
exceptionally steady, and as a matter of fact she rolled only
3° one way and 4 another, and the range of pitching was
only 10". I am sure that no vessel in our Navy could have
passed through that sea without rolling at the least 25 to 30 /'
Admiral Sir Houston Stewart, RN, also a guest aboard
during the severe storm, opened the discussion after Reed's
(1881) paper: ". . . 1 never was in so comfortable a ship at
sea in a gale of wind . . . the absence of rolling, the easiness
of motion, the great comfort on board, and the handiness
of steering, were such as I have never seen before in any other
ship under similar circumstances of weather and sea/'
Many had expected that, like Novgorod and Vice Admiral
Popoff, the Livadia would take seas aboard during rough
weather, but Livadia had more adequate freeboard. Admiral
Stewart commented: "Sir Edward Reed took every opportun-
ity of investigating the height of the seas, because he went
into places where I did not care to go even as an old sailor.
The point where he showed you the Imperial Arms looks
over the sea, and he went to the extremity when she put her
nose down in the sea, and out to the end of those outriggers
in the height of the gale. An ordinary ship would have rolled
those in the water, but she did nothing of the kind, you
simply saw the waves spring up like surge on an ordinary
beach. Sir Edward is fully competent to tell you his opinion
of her behaviour at sea, and all 1 can say is that I fully
endorse all I have heard with regard to her/*
Modern empirical rolling formulae, developed from
experience with conventional hulls, suggest that with tremen-
dous metacentric height due to her great beam, Livadia must
have had a very short period of roll. However, Goulaeff
(1881) stated: "The rolling in no case exceeded 3i or 4° . . .
[196]
The period of oscillation, at the same time, is also very large.
Such ships, as explained in an article in Nature (July, 1880),
while obeying each wave, are by that very means exempted
from the tendency to accumulate the effect of a succession of
waves . . . The forward part of the superstructure divided the
waves, which were met vertically in two parts, while the edge
of the lower raft divided them horizontally, thus destroying
the effect of the waves on the vessel."
Livadiu had a few faults too. Reed (1881) reports on minor
damage sustained during the storm— damage which went
undetected at the time. Livadia was inadequately framed,
leaving large unsupported area of 7rt in (1 1 mm) hull plating.
In the storm, she cracked a plate, flooding a small void
compartment on the starboard bow. Strongest criticism of
Livadia focused on "pounding" experienced as she was driven
against head seas. Commenting on pounding and structural
strength. Reed (1881) stated: ". . . anyone who has observed
a tumultuous sea in a storm must be prepared to learn that a
ship of extremely light draft and of almost perfect steadiness,
receives violent blows from the ascending water, and this
more especially right forward, where the onward motion of
the ship naturally subjects the bow to additional violence
... I estimated the heights of the larger waves during the
worst part of the gale as quite 25 ft (7.6m) and, as the sea
was confused, there were at times crests and peaks of leaping
sea, so to speak, that were obviously capable of striking
under the bottom with tremendous force . . . around the bow
of the Livadia, in its outermost compartments, there were
injuries inflicted ... by the sea alone, and proving . . . that
there was considerable local weakness at that part ... As
the ship is approximately circular. Admiral Popoff has seen
fit to frame her radially, a system which naturally tends to
concentrate strength near the central parts of the vessel, and
to distribute it unduly at the exterior parts ... It is easy to
make up the deficiency in these outer parts by introducing
additional frame angle irons ... I can hardly believe that any
experienced shipbuilder now present will be prepared to
affirm that the weakness developed under the circumstances
could not have been anticipated."
stability in the presence of surface waves. The discus models
showed minimum motion and nearly followed the slope of
the waves. They were found incapable of resonant behaviour,
regardless of wave period or shape. This confirms statements
by Reed, Stewart, and others about Livadufs easy and
limited motion in a seaway.
Observation of discus models in waves and analysis of
films, showed slamming when the edge of the disc went into
a trough after crossing an unstable crest. Digging-in of the
leading edge or flooding of the upper surface were not
observed, even with the wave machine set to produce the
most precipitous waves within its capability, except when
the model was ballasted to several times its normal gross
weight. This appears to conform with Livadia experience in
confused Bay of Biscay seas and with earlier experience of
the circular ironclads, Novgorod and I 'ice Admiral Popoff.
Faced with the choice between high-drag shapes that some-
times achieved resonant motion, and low-drag shapes that
never became resonant, the discus buoy was selected. To
date, full-scale 40ft (12.2m) diameter discus buoys, now in
ocean service, are understood to have lived up to all expecta-
tions as regards hull performance. The popotTka has been
tried. It has been tested in both model and full-scale by
thoroughly reputable individuals. GoulaelT (1876, 1881) and
Reed (1881) presented facts justifying claims of very unusual
stability coupled with extremely easy motion. Yet conservative
ship designers and operators arc reluctant to depart from
conventional practice, even to the extent of model testing
the popoH'ka form and otherwise investigating its actual
merit.
If alleged popoffka characteristics can be confirmed, the
type would appear useful as factory ships for the fisheries,
research vessels, tracking ships, mobile missile erection and
launch facilities, salvage and heavy-lift vessels, underseas
mining platforms, deepsea drilling ships and the like.
Moored buoy trials
Commencing in 1962 under an Office of Naval Research
contract, the Convair Division of the General Dynamics
Corporation (1963) undertook to develop a moored tele-
metering oceanographic buoy, with a design station endurance
of one year. Comparative evaluation of drag and stability of
24 configurations of buoy hulls, involving 957 gravity tows
and 147 carriage runs in the Convair Hydrodynamics Towing
Basin, was undertaken. Towing was conducted both in
smooth water and in the presence of waves. Apparently
without prior knowledge of the much earlier popofl'kas,
flat-bottomed circular buoys of shallow draft, so-called
"discus" buoys, were among the configurations tested.
With the density of the discus model adjusted to correspond
to a 40 ft (12.2 m) diameter full scale, the model behaved as a
planing hull, above a certain equivalent full-scale velocity
depending upon surface roughness. A significant reduction in
drag was associated with this phenomenon. This appears
to confirm Froude's findings on the resistance of circular
ships. Towing of the discus models in the presence of waves
showed large variations in resistance. But, because of the
relatively large reserve buoyancy, the model was never swept
over by wave crests, so long as model density was low enough
to prevent towing under. This seems to confirm Reed's and
Stewart's comments on the dryness of Livadia"s weather
decks in stormy seas.
Two discus models were tested for buoy hull model
This written reply to the section headed "< omputcr Design of
Boats" was received late:
Hayes (UK): Regarding Williams' proposals for using
alternative parameters in a similar resistance analysis, it is
appropriate to warn against any considerable increase in the
number of parameters beyond the number used in the analysis
of this FAO data, particularly if the parameters, when plotted
against each other in pairs, do not yield a rectangular scatter
of data points. In such a situation, a successful outcome \\ould
be extremely unlikely. Parameters which are directly applicable
to the mathematical definition of ship lines tend to he of this
type — large in number and highly correlated. A discussion of
the statistical background to these remarks was given by
Hayes (1964).
In reply to Corletl's remarks on the regression analysis
approach, it is not necessary that all the forms used in such an
analysis should be of high quality. On the contrary, it is
necessary that the data contain a substantial number of forms
of lower quality so that the parameter ranges and parameter
combinations under consideration arc adequately covered.
Cardoso asked why 14.51 at a C,, of 0.65 was not taken as
the best value of CK rather than 15.71 at a C,, of 0.575
(table J(a) of the Traung et al paper). The answer is that this
table gives only part of the Cu value for the design under
consideration: in particular, it does not take into account the
f 197
effect of changing Cm. It can be seen from table l(c) that, in
order to keep ® constant at a value of 4.5, the increase of Q,
from 0.575 to 0.65 necessitates a decrease in Cm from 0.758
to 0.670. From table l(b), this decrease involves a penalty in
CR of about 2.2 units, which more than cancels out the
difference in the CR values in table l(a).
On Cardoso's last point; the equations can, of course, be
used to design vessels with high values of angle of entrance,
when these are preferred.
In answer to Kilgore's question, the justification for the use
of particular parameters must always, in the end, rest on how
well the derived equation containing those parameters fits
the data. If an adequate fit is obtained, it follows that the
parameters must have adequately described the hull shape
for the purpose concerned, at least for the variety of vessels
represented in the data.
[198]
PART III
MATERIALS
Boatyard Facilities .
Wood for Fishing Vessels .
Aluminium and its Use in Fishing Boats .
All-Plastic Fishing Vessels .
J F Fyson A 1 JO-ft Fibreglass Reinforced Plastic Trawler
Ralph J Delia Rocca
Cunnar Pcdcrsen
Comparison between Plastic and Conventional Boat-building
. C WLcvcau Materials D Verweij
Mitsuo Takchana Discussion
Boatyard Facilities
by J. F. Fyson
Chantiers de construction navale
I) est possible dc construirc a pen de frais des bateaux de peche
adaptes aux besoins locaux & condition de pouvoir fairc appel ii un
architecte naval connaissant bien les bateaux de petite taille et
ayant etudi6 la situation locale. L'uuteur recapitule les techniques
modernes de construction de bateaux en hois, traitant du trace sur
plancher et de J'etablissement des gabarits des differences entre
membrures ehantournees et membrures etuvees, du choix des
hois, de TStuvage et du ployage des membrures, de la preparation
des elements structuraux lamelles, et fournit les conseils sur les
colles et techniques de lamellation a employer. La communication
d6crit de facon detaillee Pagencement du chantier dc construction,
en insistant sur la necessite de prevoir des espaces sufllsants pour
1'entreposage et le sechage des bois, une disposition rationnelle des
machines a travailler le bois, et 1'evacuation des dechets. L'auteur
traite de la production en serie. Pour le relevage et la mise & I'cau, il
pr6conise I'utilisation de slipways ou, pour des bateaux dc petite
taille, de mats de charge (employes seuls ou en comhinaison), tous
ces appareils devant etre conc^is par des special istcs. II sc declare en
faveur de la suggestion de Christensen visant le numcrotagc des
diverses operations a des fins comptables. F.nfin, il insiste sur lu
necessite d'une bonne planification de 1'installation du chantier
naval, de son exploitation et du recrutcment de personnel quali(i6t
ct presente des recommandations pour Porganisation el la gcstion
du chantier.
Instalaciones y medios en los talleres de construcci6n de embarcaciones
Contando con un arquitccto naval dotado de experiencia en el
discfto de pcquenas embarcaciones y que liaya estudiado las
condiciones del pais, se pueden construir embarcaciones pes-
queras baratas que se adapten a dichas condiciones. Resume el
autor los modernos procedimientos de construccitSn de embarca-
ciones de madera. Describe ei trazado en la sala de galibos y la
fahricacion de modelos, las difercncias entrc la construcci6n de
cuadernas de madera entcriza curvada y de madera curvada at
vapor, la seleccitSn de la madera, tratamicntos al vapor y curvatura
de piezas, cl modo de construir las piczas estructurales laminadas,
y asesora sobre las colas udccuadas y las tecnicas de laminacion. Se
describe detalladamente lu disposicion del taller de const ruction de
embarcaciones; la neccsidad de disponer de un espacio adecuado de
secado y almacenamicnto de madera ; la disposicion de las ma qu in as
que sirven para trabajar lu madera; la climinaci6n de los desper-
dicios. Se examina la prodticcion en serie. Respecto a la eficiencia
para el remolque y la botadura, el autor aconseja varaderos
disenados por expertos, asi como gruas y combinaciones de gruas.
Se apoya la indicaci6n de Christensen de numerar las distintas opera-
ciones con fines contables. Fl autor pone de relieve la neccsidad de
una debida planificacion para montar un taller de construcci6n de
embarcaciones, dirigirlo y contratar personal capacitado. Formula
recomendaciones respecto a la planificacion y administration del
mismo.
SMALL wooden boatbuilding has traditionally been
an individualistic craft with most boats custom
built for owners with very diversified requirements.
Recent experiments, notably in the field of pleasure
craft, towards mass production suggest the possibilities
of streamlining the construction also of wooden fishing
vessels.
Perhaps the most notable advance in small boat mass
production methods is in the field of glass-reinforced
plastics, which is outside the scope of this paper. Some
of the lessons learned, however, could also be adapted
for use in wooden construction.
in the prefabrication of sections, particularly deck-
houses and superstructures, more use could be made of
aluminium and iibreglass to reduce the weight of more
conventional steel construction.
In the field of small light-weight craft for close inshore
fishing, greater use could be made of composite ply-
reinforced plastic construction which readily lends
itself to mass production methods.
DESIGN CONSIDERATIONS
Scries production and the rational use of labour are
dependent on the stabilization of the production of boat-
yards around a basic number of designs suited to local
requirements. Developing countries which are about to
make the step up from indigenous craft, which are no
longer suitable for modern fishing methods, are in a
particularly favourable position to adopt this approach.
The services of a naval architect experienced in small
boat construction —preferably fishing boats — should be
used to study local conditions and produce efficient,
economical hull shapes and arrangements suitable for
the conditions. Once a suitable hull shape has been
decided, interior layout and superstructure should be
carefully planned to enable the prefabrication of the
maximum number of components consistent with fishing
requirements. Consideration of the building procedure to
be adopted and discussions with the builder can influence
the siting of tanks and equipment so that their instal-
lation can become a logical part of the production plan.
GENERAL BUILDING PROCEDURES
Lofting and pattern making
For maximum use of prefabricated components for
series building, lofting must be fully and accurately done
and an extensive use made of patterns picked up from
the loft floor.
Patterns and templates can be fabricated from ply-
wood as its light weight, dimensional stability and
resistance to breakage make it most suitable. Three-ply
interior grade plywood, i in (6 mm) to j! in (9 mm),
depending on the size of the pattern, is satisfactory. For
lightness and economy, Douglas fir, pine or oukoume
(gaboon) are also recommended. For large templates the
shapes are cut out from the lines on the loft floor,
joined by gussets and braced by solid wood battens
fastened by clenched nails or glue.
In one-off building the costs of detailed lofting and
extensive pattern making are not justified, but in series
[201]
building with the cost spread over a number of boats,
the time saved soon justifies the extra expenditure.
Wastage can also be considerably reduced by careful
positioning of patterns to enable more pieces to be cut
from the available stock while avoiding knots, cross
grain compression failures, shakes or other defects.
Sawn frame construction
Patterns can be made for the stem, deadwood and
stern post assembly, frames, transom, bulk heads, deck
beams and engine bearers.
Frame patterns should have the futtocks and the
bevels, calculated from the loft floor, marked at appro-
priate distances on each.
If equipment for handling is available, bulkheads can
be assembled complete with frame and deckbeam, and
also insulated where appropriate, before setting up.
Templates for carvel planking can be made up as the
first boat is built. For smaller boats plywood templates
can be taken from the finished plank after spiling and
before steaming and fastening into place.
For larger boats spiling templates can be made up by
fastening battens of flexible timber around the frames so
that one batten is provided for each edge of a plank.
Then the two battens representing a plank are tied
together by numerous strips of wood cross fastened to
form a lattice girder. The templates can then be removed
and used to mark off planks for a series of boats.
Large-scale use of patterns and templates, with com-
ponents fabricated in advance and brought to the boat
as work proceeds, demands careful and accurate setting
up to ensure good fitting and to avoid wastage.
Bent frame construction
Construction procedure differs from that of sawn frame
in the preparation and setting up of frames.
Selection of stock
Where considerable bending is required only hardwoods
can be used, oak, elm, ash, hickory and beech being
suitable timbers. The grain of the wood should not
exceed a slope of 1 in 12; steeper slopes cause excessive
breakage. Knots and surface checking should be avoided
except near the ends of frames where small knots and
some surface checking are permissible. Green timber is
preferred for bending as it is usually free from surface
checks, heats quickly and does not require pre-soaking.
Preparation and steaming
To prevent side buckling, the width of bending material
should be greater than its thickness. Time of steaming
should be of the order of 1 hr per in (2.5 cm) of thick-
ness. Over-steaming should be avoided.
Bending
In small boats, frames are bent directly into the boat
after steaming but for larger boats with frames of larger
dimensions slight curves can be made over formers
without straps. One end of the steamed member is
fastened to the former and then pulled down pro-
gressively to the curve and clamped in place. More
severe bends require the use of tension straps (fig 1).
These should have end fittings to hold the wood rigidly
during bending. Blocks of soft wood should be placed
between the timber to be bent and the end fitting to
absorb the increase in end pressure as the bending
proceeds.
The limiting radius to which hardwoods can be bent
is of the order of four times the thickness, provided good
quality selected timber is used.
CAPSIZED
END FITTING
CORRECTLY
DCftlCiNEP
END FITTING
Fig L Tension strap
For bending timbers of a cross-sectional area greater
than 20 in2 (12.8 cm2) a bending apparatus is employed
consisting of a cast-iron slab with a grid of holes to take
steel spikes which act as stops. A wood former is then
fastened to the slab and the steamed member in its
tension strap is pulled down to the former using a block
and tackle (or a power winch in the case of heavy frames).
The bend can be fixed by cooling on the former or
battens can be fastened across the bent member to hold
the curve. In the case of large frames a chain holding the
tension strap to its curve allows the member to be
removed from the slab and stored until ready for machin-
ing and assembly.
Lamination
The building up of structural members of large dimen-
sions and the formation of curved members by gluing
up from thinner material particularly lends itself to
series production. Standard sawmill dimensions can be
used or machine operators can prepare quantities of
standard dimension timber in advance.
[202]
Gluing
Phenol-resorcinol-formaldehyde adhesives are recom-
mended as this type sets and cures at lower temperatures
than the phenol resin adhesives. Tables 1, 2 and 3 give
an indication of the range of temperatures, assembly and
clamping times to be expected.
TABLE 1 : Pot-life of phenol-resorcinol-formaldehyde adhesive in hours
Temperature
Fast-curing
resin
Medium-curing
resin
Slow-curing
resin
C 5°
F 41°
9-10
10°
50°
6-7
15°
59°
2i-3|
4i-5i
20°
68°
U-2
3 3£
5-6
25°
77°
2-2*
3M
30°
86°
1-1*
21-3
35°
95°
TABLE 2: Assembly time in hours
Temperature
C 5°
10°
15°
20°
25°
30°
35°
F 41°
50°
59U
68°
77°
86"
95°
Fast -curing
resin
4
3
U
1
—
—
Medium-curing
resin
—
—
23
2
H
1
—
Slow-curing
resin
- —
——
—
3
2
H
1
TABLE 3 : Clamping times in hours
Temperature C 5° 10° 15y 20° 25° 30° 35*
F 41° 50° 59° 68° 77° 8611 95°
Fast-curing
resin . 18 14 4 3 — - - —
Medium-curing
resin — — 81 5 4 2 —
Slow-curing
resin . — — — 10 54 4 3
Mixing of glue
Small amounts of glue can be mixed by hand but larger
amounts require a mechanical mixer. Portable electric
drills equipped with paddles can be used for moderate
amounts of glue, but due to the high speed of the drill
the area of paddle surface should be small to avoid
foaming.
For large-scale mixing a dough mixer with two- or
three-speed control, turning the paddles in a double
rotary motion, is ideal.
Glue spreading
For good glue joints the correct quantity of glue should
be evenly spread over the entire gluing surface. Small
areas can be covered by brushing, but for large surfaces
application by hand mohair paint rollers is suitable.
These must be cleaned before the glue hardens to an
insoluble state.
Methylated spirits can be used to dissolve glue while
it is still liquid.
For large quantities of work, machine spreaders can
be used. These are fitted with rubber-covered rollers and
control rollers to regulate the thickness of the glue
applied.
In conditions of high temperature and low humidity
a thicker glue spread will permit a longer open assembly
time. Conversely, if humidity is high and temperature
low a more economical spread can be used. Under
average conditions, of the order of 65°F (18°C) and at
65 per cent relative humidity, 9 Ib per 100 ft2 (0.45 kg/m2)
is satisfactory. Half this quantity is used on each face
if double spreading is used. The glue spread can be
checked by weighing a trial sample, before and after
spreading, before beginning a run.
Joints should be assembled and pressure applied
within the times given in table 2. Pressures of the order
of 150 lb/in2 (10.5 kg/cm2) are recommended with the
pressure evenly distributed by the use of hardwood
packing strips, of maximum thickness consistent with the
radius of the former, placed under the heads of the
clamps.
The laminations are iirst assembled in the order in
which they are to be placed in the jig with the bottom
lamination on top. Waxed paper is placed against the
jig face and on surfaces on which the laminations are to
rest. The laminations then have the glue applied to both
faces in order, either by hand with brush or roller, or in
a glue spreader. They are then promptly assembled and
pressure applied with the minimum possible delay to
reduce the time for which the glue is exposed to the
atmosphere.
It is recommended to surface the laminations just
before assembly so that the wood will be clean and free
from grease and dirt.
Thickness of laminations varies with type of wood and
quality, but as a general rule clear-grained timber can be
bent cold to a radius 40 to 60 times its thickness.
Curing
Provided the joints arc not subjected to any great stress,
the clamps may be removed after the times stated in
table 3, by which time one-half the maximum strength
of the adhesive will have been reached.
Curing can be accelerated in cold climates by the
application of heat. Excessive heat, however, should be
avoided to prevent drying out. If the clamped up laminate
is covered with a canvas or polythene cover, a fan heater
will provide a satisfactory means of raising the tem-
perature to 65°F(18°C).
Phenol-rcsorcinol glues are rather more tolerant of
moisture in timber than urea formaldehyde and phenol
adhesives and successful joints can be obtained with a
moisture content of up to 22 per cent.
Composite ply-reinforced plastic construction
Where light-weight hard chine hulls of small size for
close inshore, lagoon and inland water fishing are re-
quired, this method of construction is particularly
suited and lends itself to series production.
Joints at keel and chine are filled with resin putty and
covered inside and out with glass fibre cloth or tape
bonded to the hull with resin. Transverse bulkheads
bonded into the hull by the same method give great
strength combined with light weight. The use of exterior
moulds enables rapid assembly and production line tech-
niques for quantity.
[203]
YARD LAYOUT
The location of building and machines in the space
available should be planned to fit in with the handling
and transporting of timber and materials during the
successive processes so as to facilitate construction and
reduce unproductive labour to the minimum.
Considerable increase in productivity can be realized if
mechanization of the lifting and handling of timber is
utilized during all stages of construction. The use of a
mobile crane, fork lifts or straddle trucks, electric hoists
and overhead travelling cranes in a large yard, or rubber-
tyred trolleys in a small yard, can considerably increase
the flow of timber to and from the machines and from
boat to boat in a production line.
Timber storage and drying
The first step in this process is the storage yard whether
simply for storage of timber prior to utilization or for
the stocking of timber for air drying. In either case the
storage area should be fairly level and well drained and
the surface kept free from debris and vegetation. Ideally,
it should be covered with ashes, gravel, shells or crushed
stone with the roadways surfaced if cranes and fork
lifts are to be used.
Air drying
For air drying the stacks of timber should be raised 12 to
18 in (0.3 to 0.45 m) from the ground and should be
built on a solid foundation. These should be designed
to permit air to move freely between the stacks and can
consist of hard wood or concrete cross-members about
4x6 in (10x15 cm) in section supported on piers of
brick, concrete or creosoted timber. The foundation
should be arranged with a slope from end to end (fig 2).
Stacks may be of any length and up to three times as
high as they are wide but they should not be wider than
about 6 to 8 ft (1.8 to 2.4 m), because in very wide
stacks drying takes place very slowly at the centre and
stain and mould can occur.
As shown in fig 2, sticks are used to separate the
layers and these serve the dual purpose of allowing the
air to move freely over the timber and also to transmit
the weight from layer to layer. It is therefore important
that they should be arranged in neat vertical lines above
the cross-members of the foundation. Thin board of Jess
than 1 in (2.5 cm) should be stacked with the sticks at
intervals of about 12 in (0-3 m), particularly timbers such
as beech, elm, etc., which warp badly.
This spacing can be increased to 2 ft (0-6 m) for all
timbers 1 in (2.5 cm) or more and to 4 ft (1.2 m) for
dimensions greater than 2 in (5 cm) in straight-grained
species.
The rate of drying within a stack can be controlled
to some extent by the thickness of the sticks used. The
denser hardwoods must be dried slowly to avoid splitting
and if stacked during a hot season the sticks should not
be thicker than { in (1.2 cm), while 1 in (2.5 cm) sticks
can be used during cooler damper periods. Soft woods
and lighter hard woods tolerate faster drying conditions
so that 1 to 1 jl in (2.5 to 4 cm) sticks can be used.
When timber is to be dried after through-and-through
sawing, it is stacked in log form, thus usually providing
plenty of air space around each log and the sticks should
not be more than about ] in (1.2 cm) thick or drying
may be too rapid.
Effect of weather on drying
Should a hot season or a period of strong drying winds
follow immediately after green timber has been put out
to dry, serious splitting can occur. Nearly all hardwoods
require slow drying initially; therefore, it is preferable
to stack them at the beginning of a cool season. The
timber then has a chance to dry slowly during the first
months and splitting will be lessened. The drying rate
END VIEW
SIDE VIEW
STRAP TIES--
6in MINIMUM CLEARANCE
— FLUES
FOR
VERTICAL
CIRCULATION
SPACING
STICKS
4ft TO •
ADJACENT
STACK
Tlf16 In
MINIMUM
Fig 2. Timber stacks for air drying
[204]
can be controlled, to a certain extent, during a hot, dry
season by end coatings or cleats, temporarily covering
stacks with tarpaulins or wet sacks, or hosing the site
occasionally during the hottest part of the day.
Storage
Storage space for matured timber should preferably be
covered, with horizontal stacking if space permits. To
avoid loss of time in finding timbers of various dimen-
sions when required, separate stacks should be made of
timbers suitable for the following:
• Keel, stern and deadwood
• Frames
• Stringers and clamps
• Deck beams
• Planking
• Decking
• Joinery
The stacks should be located as near to the appropriate
machines as possible.
ov
..4QJJ
Machinery layout
The first machines should, normally, be a heavy-duty
saw, surfacing planer and thicknesser for cutting to size,
dressing the faces and thicknessing.
Space must be allowed for stacking and marking out,
from which the timber proceeds either to final dressing
and assembly, or to band saws for cutting of shapes and
bevels, or to a spindle moulder for grooving, rebating and
curving sections for rubbing strakes, etc. Additional
machinery such as a scarf cutter, tilting frame band saw
for bevel cutting, fine cabinet surfacer for dressing of
laminations before assembly, drill presses, bench grinders
and setting machine for saw blades, as well as a complete
machine shop for engine fittings and other metal work,
can be added to the basic layout according to the volume
of work and capital available.
Individual solutions of the layout will have to be found
for each particular yard but in all cases planning must
allow the most direct possible flow of timber through
the machine shop. Space must be provided around the
. 401 _
T
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CIRCULAR SAW
WALL
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40 ft
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\_ _ _ .. ~ _, _ .. _ -. _ _ _ _ i_ _.
f TJ
1 ,
1
i
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BAND SAW
WALL
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i
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T"
£3 ,..£.;
7ft
\
s
^
5ft
' .. '
4Oft
THICKNESSER
4Oft
7ft!
2ft
5ft
40ft
PLANER
Fig 3. Dimensions for machine layout
[205]
40ft
machines for the stacking of timber at the end of a run
and also for marking out prior to the next operation.
Extension tables, with rollers adjustable in height to cor-
respond with the machine tables, should be provided to
cut down the labour involved in machining heavy items.
Rubber-tyred trolleys for light and overhead hoists or
cranes for heavy items should be included and floor
space for manoeuvring provided. Fig 3 gives proposed
dimensions and clearances for the various machines. The
use of portable power tools to supplement the stationary
machinery and reduce the amount of additional handling
will also influence the shop layout.
Waste disposal
The use of special gangs operating machines continuously
for a series of boats raises the problem of waste disposal.
Where production is considerable this can be done by
the use of pneumatic collection plants. For clearing
waste in the hulls under construction, use can be made of
industrial vacuum cleaners.
The position and type of machines, the nature of the
wood to be machined and the amount of waste to be
handled must be considered when designing the plant.
The diameter of the connecting branches to the various
cutting heads and the velocity at which the conveying
air moves through the ducts are important considera-
tions. A fan provides the motive power for the air by
which the waste is extracted and conveyed through the
ductwork. This must be capable of dealing with the dust
and chippings which are carried in suspension in the air-
stream and must be robust and fitted with dust-proof ball
or roller bearings. It should preferably be sited in the
workshop where it can receive the necessary servicing.
The wood waste has to be separated from the conveying
air and this is generally done by cyclone.
Correct duct design is an important feature of a refuse
A THICKNESSER
B PLANER SURFACER
C CIRCULAR SAW
D BAND SAW
E FLOOR DISPOSAL - UP
F FLOOR DISPOSAL - DOWN
Fig 4. Waste extraction hoods.
[206]
extraction plant. Cylindrical ducting is almost invariably
used because of lower frictional resistance than square
or rectangular. The ducting should run in the shortest
practical direct line. Sharp bends should be avoided if
possible to minimize friction. Bends should be con-
structed with a throat of large radius (a 6 in (15.0 cm)
diameter pipe would have a 12 in (30.0 cm) radius in
the throat of the bend). Branch pipes are attached to the
main ducting at an angle not exceeding 20°.
Dust velocities for an extraction plant vary from 3,200
to 4,000 ft (1,000 to 1,200 m) per minute. For example,
3,500 ft (1,050 m) per minute is a suitable velocity for
joinery work where light dry sawdust is to be moved
while in the rougher work of cutting and planing keel
timbers with the consequently heavier and wetter dust
3,750 to 4,000 ft (1,150 to 1,200 m) per minute would be
required.
For a duct conveying velocity of 3,750 ft (1,150 m) per
minute the following branch connection sizes are given
as a guide:
24 in (0.6 m) cross-cut saw.
36 in (0.9 m) vertical handsaw
1 8 in (0.45 m) surfacing planer
24 in (0.6 m) thicknessing planer
Spindle moulder
Sweeping up point .
4| in ( 1 1.5 cm) diameter pipe
4£ in ( 1 1 .5 cm) diameter pipe
6 in (10.0 cm) diameter pipe
7 in (17.5 cm) diameter pipe
4£ in (11.5 cm) diameter pipe
6 in (10.0 cm) diameter pipe
The conveying velocity must not be allowed to drop or
choking will take place, consequently, a common pipe
required to serve two 6 in (15.0 cm) diameters needs to
be twice the area of one 6 in (15.0 cm) pipe, i.e. 81 in
(19.0 cm). Starting from the branch pipe furthest from
the fan, it is possible to calculate the size of the main
ducting as each fresh branch joins it. Waste extraction
hoods should be fitted with flexible pipes and telescopic
joints to facilitate the setting of cutters and their adjust-
ment. Fig 4 gives shapes and position of hoods together
with two suggestions for floor disposal points.
Series production
An assembly technique in which a manufactured article
passes from one process to another down a line is
obviously not feasible with wooden boats of over 30 ft
(9 m). However, by using gangs of workers passing
from boat to boat, completing a single or a series of
operations, appreciable time saving can be achieved.
For example, laminated frames prepared by workers in
one area can be set up by others passing down a line of
boats in which the keels and stem assemblies have
already been set. Bulkheads already built up on a frame
and deck beam assembly can be installed directly on the
keel, provided suitable lifting gear is available.
Mobile wheel-mounted tubular scaffolding of different
sizes and heights suitable for the various operations could
be used as the different stages proceed. Racks on the
scaffolding could hold the various portable machine
tools, clamps, etc., appropriate to each phase.
Reels to hold power cables for machine tools can be
mounted at convenient points to reduce cable length and
minimize snarling.
Lifting and transporting the various prefabricated
items should be carefully studied and provision made for
rails mounted on the roof beams to carry chain hoists or
electrical hoists to handle large laminated frames,
installation of engines, etc.
If space allows, a long covered building, with one or
two rows of boats under construction, would give the
best results.
Hauling and launching of boats
A pair of rails for a cradle, running alongside the building
berths, with a transfer or skids to each berth, will
facilitate the moving out for launching of completed
boats.
Marine railways
Large marine railways for hauling out and launching
heavy boats should be designed by experts, but smaller
installations can be laid down by the boatyard. Given a
hard stable surface, it is possible to Jay the railway
directly on it, but unless the surface is fairly even and
the gradient reasonably uniform, a foundation of wood
piling below the surface and concrete blocks inshore will
give better results.
The immersed portion of the track can be constructed
of wood, assembled onshore as a unit, sunk on the
previously prepared foundations, aligned and secured.
All underwater woodwork should be chosen for resist-
ance to marine borers and treated with creosote or,
still better, by one of the proprietory brands of anti-
worm preparations.
Track can be constructed on a uniform gradient
usually between 1 : 10 and 1 : 20 or on the arc of a
circle with the cradle designed so that the deck is hori-
zontal when hauled out.
Whenever possible the cradles for smaller boats, as
discussed here, should preferably be built entirely of
wood because, if structural steel is used and the cradle
is overloaded, the structural steel will assume a per-
manent bend which will be difficult to rectify. For very
large boats it will naturally be necessary to use structural
steel with cross beams, deck and blockings of wood, or
cradles entirely of steel. Where the track is uneven the
cradle should have only two wheels on either track to
maintain straight keel block line.
For large vessels, sliding bilge blocks, running on a
track and operated by lines to the side stanchions, can be
used. For smaller vessels the keel of the vessel rests on
the cross beams and adjustable bilge supports are set up
to maintain the vessel in position when hauling begins.
Hauling machinery can be diescl or electric and for a
large installation chain is superior to wire for hauling
because of its much longer life.
Derricks and sheerlegs
For lighter craft and also for removing and replacing
engines and the stepping of masts, derricks and sheer-
legs can be constructed at the dockside. Feet of such
fittings should be well fastened and staying should be
carefully calculated to allow a good safety margin for the
anticipated loads.
A pair of derricks working together can be used for
lifts of up to 15 tons and for a small yard such an instal-
lation would be much cheaper to maintain and operate
than a marine railway.
[207]
WOOD-WORKING MACHINERY FOR
BOATBUILDING
Expenditure on machinery must be studied in the light
of productive capacity of the yard, demands of the market
and possibilities of capital recovery.
A limited range of fixed machinery can be effectively
extended by a wise selection of power tools.
Fixed machinery
Less complex than the variety of machinery seen in a
large joinery shop, with its high-speed multiple-head
moulding machines, chain morticcrs, tenon machines,
etc., the range can nevertheless include many of the items
mentioned below.
Circular saw
A circular saw is principally used in a boatyard for rough
cutting of stock into planking, framing material, beams,
stringers, clamps and other heavy cuts, although it can
also be used in cross cutting, rcsawing, inhering and
with added attachments, grooving, rabbeting, etc. The
universal type of saw, in which both rip and crosscut
blades can be mounted, is the most useful. Where
lamination is practised in large quantities it will be
extensively used for resawing of laminations.
Bandsaw
Many of the operations for which a band saw is used
in a boatyard involve the cutting of bevels. Bevel band
saws arc of two types, tilting table saws in which the
bevel is cut by varying the angle of the table in relation
to the saw or tilting frame bandsaws in which the angle
of the blade is variable in relation to a horizontal table.
Both are widely used, but the tilting frame saw has the
advantage of a fixed horizontal table for manoeuvring of
heavy timbers. Changes in bevel are controlled by a
wheel and the range of bevel is usually 45° to the left and
1 5" to the right.
Both can also be used for all the other cuts normally
made with a bandsaw. A smaller bandsaw or a jigsaw is
often useful for cuts of sharp curvature in thin timber for
joinery and plywood.
Planers
For the small boatyard, combination planers, performing
both surfacing, thicknessing and various other opera-
tions depending on the attachments provided, are more
desirable, but in larger yards separate heavy duty machines
are required.
The surface planer dresses, faces and cuts square
edges on keel, frame, deck and other timber and also
tapers and bevels straight sections.
The thicknesser is used to reduce timber to dimension
after dressing.
Where high accuracy and finish are required, such as in
the preparation of laminations, a planer capable of
finishing stock to a tolerance of ±0.01 in (0.2 mm) is
needed. A double cutterhead planer capable of planing
two surfaces at once and with the number of knife cuts
per in (2.5 cm) regulated between 20 and 30 should
prove satisfactory.
Moulding machines
A two-speed spindle moulder for use with both square
cutter blocks and French spindle head is used in trim-
ming, shaping and moulding stock which is irregular in
outline and also for cutting scarf joints in keels and other
solid stock. Used with special wood jigs, such a machine
can also be used to cut variable bevels on frames or for
bevelling hog timbers for planking rabbets.
Sanders are used for sanding before assembly. Al-
though the output capacity of a drum sander is high,
unless it is fully occupied it is better to use the slower
belt sander because its running costs are lower.
Portable machinery
Portable circular saws are used for cutting to length on
the job, the rough cutting of scarfs in keels, keelsons,
clamps stringers, etc., and other jobs requiring a straight
shaping cut Small electric jig saws arc invaluable where
complicated shapes arc to be cut in plywood, e.g. plank-
ing for hard chine boats, plywood decks, etc.
Portable hand planers have many uses in the planing
of curved members, such as the dressing up of laminated
beams, frames and stems, where the shape renders planing
in a machine inconvenient.
Portable electric drills arc extensively used in all
types of assembly work for drilling bolts, lead holes for
drifts and boat nails, pilot holes for screws, etc. Where
large numbers of screw holes are to be drilled, an adjust-
able bit which drills shaft, shank and countersink in one
operation will prove a worthwhile investment.
In all drilling operations care must be taken to buy
and use only the correctly powered drill for the size of
hole. Forcing a lightly powered tool to drill out holes
beyond its capacity is expensive in time and tools.
A special power borer is also available for the drilling
of shaft holes, an exacting and time-consuming process
when done manually.
Jn plywood construction and elsewhere where large
numbers of screws are to be driven, power screw drivers
can considerably reduce the time spent in the screwing of
planking and deck panels.
Power hammers can be used for the driving of boat
nails and drifts in heavy construction.
Disc sanders arc used to sand planking and decks
before painting and vibratory sanders and portable belt
sanders for joinery items which are to be varnished.
MANAGEMENT AND PLANNING
Series production in boatbuilding, as suggested in this
paper, using groups of workmen to perform the various
operations down a line of boats, requires careful planning
and organization. A clear idea of the time required to
carry out each step, the materials and tools needed, as
well as the indirect labour and administration to support
the working gangs must be co-ordinated into a compre-
hensive work plan. An analysis such as this is directly
linked with a cost estimate and an efficient costing
system will be a valuable adjunct to all planning.
The size of each gang and its work must be decided
in relation to the other groups so that delays and bottle-
necks are eliminated. The number of machines and
[208]
machine operators must be geared to the requirements of
the construction teams so that maximum output is
achieved.
Investment of capital in machinery
When equipping a yard for series production or buying
new machinery to reorganize an existing yard, the
problem is not simply one of buying the most modern
machines with the fastest productive capacity. Several
factors should be considered. Of major importance is the
question of recovery of capital.
The cost of a machine is retrieved by way of depreci-
ation, which is an annual amount charged to the cost
of production during the working life of the machine.
Over-capitalization in machinery may result in such high
depreciation charges that they cannot be recovered
from the price fixed for boats under production and a
part of the charges will have to be recovered from
previous profits. Consequently each machine and piece
of heavy equipment acquired, must be integrated into
the overall production plan, with a careful balance
struck between the increased production obtained and
the higher depreciation charges to be supported.
The productive capacity of the machinery must be
considered in relation to other processes in the scries.
To take a simple case, a yard contemplating the purchase
of a fork lift truck or small mobile crane for the mechani-
cal handling of timber and its delivery to the machines,
must first calculate the quantity of timber which can be
processed by its machinery over a fixed period and the
amount of time which the lift or crane could be occupied
in carrying out this operation. Other possible jobs which
could be performed, such as transportation and instal-
lation of engines, are then taken into account and the
maintenance and depreciation charges balanced against
increased production and the reduction of labour costs
by the elimination of labourers for handling. Investment
in additional machinery to provide increased production
must be based on an accurate estimate of the market
possibilities so that expensive machinery is not idle,
thus increasing the establishment costs on the number of
direct-labour hours worked.
Cost estimates
An efficient costing system will provide detailed informa-
tion on each stage of production and will show how each
section contributes to the yearly output, thus providing,
as well as the production cost of the boat, information
on sources of waste and inefficiency. The expense in-
volved in introducing and maintaining a costing system
is likely to be quite heavy, therefore it should be kept as
simple as possible within the limits of the information
required.
Itemization of construction
Christensen (1955) has proposed a system of itemization
to standardize estimation and such a system should be
arranged to allow grouping of procedures performed by
each gang.
The major headings are broken down into individual
operations which are given a number on the decimal
system. Job cards can then be filled out daily under the
different numbers.
The division suggested is as follows:
1 Backbone
1.1 Keel
.2 Stem and apron
.3 Stem knees
.4 Deadwood
.5 Stern frame
.6 Skeg
,7 Transom
1.8 Fastenings
1.0 Total backbone
2 Framing
2.1 Frames
2.2 Floors
2.3 Fastenings
2.0 Total framing
3 Longitudinals
3.1 Keelson
3.2 Bilge stringers
3.3 Clamp and beam shelf
3.4 Shaft log
3.5 Engine foundations
3.6 Breast hooks
3.7 Fastenings
3.0 Total longitudinals
4 Planking
4.1 Planking
4.2 Blockings
4.3 Fastenings
4.0 Total planking
5 Decks
5.1 Deck beams
5.2 Knees, partners, blockings
5.3 Deck strapping, tie rods
5.4 Covering board
5.5 Deck planking
5.6 Fastenings
5.0 Total decks
6 Interior joinery
6.1 Bulkheads, transverse and longitudinal
6.2 Ceiling
6.3 Fish hold
6.4 Stanchions and pillars
6.5 Flooring
6.6 Built-in furniture
6.7 Doors
6.8 Ladders
6.9 Fastenings
6.0 Total joinery
7 Superstructure
7.1 Deckhouse and cabin trunks
7.2 Framing
7.3 Exterior sheathing
[209;
7.4 Doors and windows
7.5 Interior sheathing and bulkheads
7.6 Hatches and skylights
7.7 Fastenings
7.0 Total superstructure
8 Deck fittings
8.1 Masts and spars
8.2 Rigging
8.3 Deck machinery
8.4 Steering gear
8.5 Miscellaneous deck fittings
8.6 Fastenings
8.0 Total deck fittings
9 Machinery and associated piping
9.1 Main engine
9.2 Engine installation (including shafting pro-
pellers, bearings)
9.3 Generators
9.4 Controls and instruments
9.5 Tanks
9.6 Fuel filling and transfer systems
9.7 Pumps, plumbing and sanitation
9.8 Refrigeration, heating and ventilation
9.9 Accommodation engine room
9.0 Total machinery
10 Finishing
10.1 Caulking
10.2 Paying
10.3 Sanding
10.4 Preservatives and painting
10.5 Miscellaneous
10.0 Total finishing
11 Electrical
11.1 Batteries
1 1 .2 Panels and switchboards
11.3 Lighting fixtures
11.4 Wiring
11.5 Electronic equipment
11.6 Antenna and lead-in trunks
11.7 Searchlights
11.0 Total electrical
12 Equipment
12.1 Ground tackle
12.2 Fishing gear
12.3 Boats
12.4 Navigation equipment
12.5 Life-saving equipment
12.6 Fire extinguishers and equipment
12.7 Tools and spares
12.8 Bosun's stores
12.9 Galley equipment
12.0 Total equipment
13 Miscellaneous
13.1 Transport
13.2 Launching
13.3 Other items
Elements of costing
The total costs incurred in the construction of a boat
can be divided into three main headings :
• Expenditure on materials
• Expenditure on direct labour
• Cost of establishment charges
Using the itemized construction plan set out above,
materials and direct labour can be calculated for each
item as proposed by Christensen (1955).
Establishment charges
This includes yard costs, administration costs, sales and
advertising costs.
Yard costs group all the expenses incurred in the
building yard and include rent, lighting, heating, power,
plant maintenance, indirect labour, tool replacement
and depreciation on machinery. Standing charges do not
vary with production and include rent, rates, heating
and depreciation. Variable charges such as tool replace-
ment and electric power fluctuate according to quantity
of production and must be calculated on the volume of
the work estimated for the year.
Administrative costs include office and drawing office
salaries, printing and stationery, depreciation on office
equipment, audit fees, etc.
Sales and advertising costs must include the prepara-
tion of bids, display advertising, etc.
With direct labour hour costing, the wages expended
on direct labour during one hour are calculated and the
correct percentage of establishment charges added. This
percentage is calculated by comparing the establishment
costs over the previous year with the costs of direct
labour for the same period.
The successful operation of the system is dependent on
the accuracy of the estimated establishment charge
percentage and on the continuity of production during
the year. Evidently the standing charges are not depen-
dent on production, hence if there are any delays in
production the establishment charge percentage will be
higher than calculated and this increase will have to be
deducted from the profit.
The production plan
The itemized construction list can be analysed and
sections relevant to the boat under construction timed to
fit into an overall production plan. A basic timetable is
established so that each section of work is co-ordinated
into the general plan and work on various items pro-
ceeds simultaneously in order. This done, a breakdown
of the labour force can be established to assign the
correct numbers of workers to each gang so that pro-
duction proceeds smoothly. Arriving at a co-ordinated
plan is not a simple procedure and its application
depends on considerable juggling with the limiting
factors, the skilled labour force available, delivery
dates of equipment and material, facilities available in
the yard, etc. Such a plan will be subject to revision in
the light of experience gained as production proceeds
and here cost accounts are a valuable aid to increase
production efficiency.
[210]
FACTORS IN THE ESTABLISHMENT OF A
BOATYARD
The establishment of a new boatyard or the re-equipping
of an old yard to undertake series production requires a
careful study of the possible demand for new boats.
In developing countries, where a new type of fishing
industry is being established, information as to the
availability of financial aid for the purchase of boats
either by government subsidy or loan, private loan
capital or co-operative ownership will assist in assessing
the possible market.
Economic and other factors connected with the fishing
industry as a whole will provide guides to possible
development with an increased demand for boats. In-
formation on the following points will aid decisions:
• Materials for boatbuilding available locally
• Restrictions and import quotas which could
hamper the supply of necessary materials and
equipment
• Sources of skilled craftsmen for boatbuilding
• Resources of the local fishing grounds
• Ratio of supply and demand in the local marketing
of fish
• Export possibilities for fish or fish products
• Storage and canning facilities and plans for new
development
• Harbour facilities available or planned for in-
creased fleets
• Availability of crews to man larger fleets
• Existence of government fisheries schools for
training of fishermen
TRAINING OF PERSONNEL
One of the most important assets of a successful boat-
yard is the skill of its workmen and this is probably most
difficult to provide in the establishment of a boatyard
in many developing countries.
If sufficient skilled men can be found to provide a
charge hand for each gang, the remainder can be com-
posed of men trained in the use of tools (house car-
penters for example) who, under the direction of the
charge hand, will acquire the skills necessary for the
particular operations which the gang is to perform. The
transfer of the more able men from gang to gang as they
achieve proficiency in one operation will over a period
provide trained men with the all-round skills necessary
for future foremen and charge hands.
Simultaneously, longer-term training of apprentices
should be undertaken. Where craft schools are available,
provision should be made for youths to attend courses
for one day per week at the expense of the yard to
acquire proficiency in the use of woodworking machinery,
reading of drawings, use of tools, etc. Where such
courses do not exist and for supplementary courses not
provided at a craft school (lofting for example) instruc-
tion should be given at the yard by experienced per-
sonnel. In the yard apprentices should be moved from one
gang to another to cover every phase of construction.
investment in the training of young men as apprentices
should be covered as far as possible by indenture for a
stated period.
Money invested in such schemes should be included in
establishment charges and will in the long term provide
a pool of skilled labour which will result in a flexible and
smooth-running organization.
211]
Wood for Fishing Vessels
by Gunnar Pedersen
Le bois dans la construction des bateaux de p£che
Les essais normalises mis au point dans Ics laboratoires d'etudc des
produits forestiers depuis 40 ou 50 ans ont permis au bois de passer
du stade de matiere premiere artisanale a celui de matiere premiere
industrielie. La communication 6numere les facteurs structured
intervenant dans la fonction et la forme des bateaux de pfcche, et
mentionne les caracteristiqucs dc resistance a certaines charges que
doit posseder telle ou telle partie dc charpente en comparant a cet
egard le bois et les autres materiaux. On constate que, par rapport
& ceux-ci, le bois possede en maticre de resistance et de rigiditg des
proprietes superieures; ses caracteristiques sous charge statique sont
inferieures et ses caracteristiques sous charge dynamique nettement
superieures.
L'auteur montre la maniere dont la resistance & la traction, au
cisaillement et a la compression sont affectecs par les noeuds, le fil
tors, et autres dcfauts naturels du bois, ct comment, a partir
d'essais effect ues au laboratoire, peuvent ctrc obtenues des valeurs
surcs pour la preparation du projet de navire,
L'auteur traite des assemblages homogcnes (par collage), qu'il
juge les meilleurs, et expose les a van (ages, ainsi que certains
inconv6nients, des membrures lamellecs ct collees par rapport au
bois vert plein. Apres avoir evalue les proprietes mecaniques des
mcmbres ployes, des pieces dc quille, des membrures courbcs, des
barrots, il deer it brievement des charpentes entieres en hois, ainsi
que diverses possibility d'emploi du bois en combinaison avec
d'autres materiaux.
La madera en las embarcaciones de pesca
Las pruebas normalizadas llevadas a cabo en los laboratorios de
productos forestales durante los ultimos 40 6 SO aflos ban elevado
de nivcl la categoria de la madera desde correspondcr al de la
artesanfa hasta pasar a ser un material de ingenieria. En este
documcnlo se enumeran los factores estructurales en la funcibn y
forma de los barcos pesqucros, indicandose las caracteristicas de
resistencia necesarias para soportar cargas determinadas para una
pieza eslructural especifica y comparando estos requisites en la
madera y en otros mater i ales. Las propicdades especificas de
resistencia/rigidez de la madera se ha comprobado que son mas
elevadas que para otros materiales, las propiedades de carga
estatica inferiores y las de carga dinamica muy superiores.
En este trabajo sc cxplica en que forma influyen en las resistencias
a la traccion, al corte y a la compresitSn los nudos, las fibras
desviadas y otros defectos naturalcs y de qu6 forma sc pueden
deducir valorcs seguros de resistencia para el disefto a partir de los
valores dc resistencia obtenidos en las pruebas de laboratorio.
El autor trata la cuestion de las juntas encoladas homogeneamente
que considera las mejores, y cxpone las ventajas y algunos in-
convenientes de las piezas estructurales laminadas y encoladas en
relacion con las de madera verdc solida. Se senalan las propiedades
de resistencia para las pic/as de madera curvada, las piezas de
quilla, las de cuadernas curvas, baos y estructuras de madera
complclamente montadas, y tambien se describcn brevemente
algunas de las posibilidadcs dc utilizar la madera en combination
con otros materiales.
FROM time immemorial, ships have been built of
wood and one hundred years ago it was still the
only important shipbuilding material. In this
century, the use of wood in big ships has become neg-
ligible but for smaller vessels wood will continue to be
important; however, its special properties must be kept
in mind. Hard-gained knowledge of these properties,
through trial and error methods, has been forgotten at
times. For example, what has happened to the structural
designer's ideal, the homogeneous unit structure in
which the material uniformly distributes and assimilates
load stresses? Fig 1 illustrates how the Egyptians built
their obelisk carriers as homogeneous units. The clinker
built boats in the right column are also one unit. The
multi-layer clippership of the Vision class, built from
1850 (Murray, 1851), approaches the ideal (fig 1), Even
today the Vision would be far advanced on general
designs.
During the Middle Ages, the importance of one unit
construction was forgotten. The result was the so-called
European type ship (fig 1). In this design the many
essential interrelated structural and design problems,
known by masters for centuries, were ignored. But the
large European ship became, by historical circumstance,
the only important one. The design was copied and its
principles were extrapolated downwards for smaller
ships, indiscriminately. Shell built hulls went out of
fashion.
Otsu (1960) reported upon an investigation of the
longitudinal strength of a small wooden boat built in
Japan. These were his calculations for "safety factors"
for longitudinal strength properties (vessel age is not
given):
Safety factor in compression 35
Safety factor in tension 88
Safety factor in shear 16.5
Otsu concluded that the results suggested a much
stronger structure than previously estimated. (Author's
note: with content and distribution of undestroyed
material at time of investigation.) Otsu went on to say
that scantlings might be reduced to save hull weight, but
that there must always be a margin for deterioration and
easy repair. Otsu sketches an "old type" vessel with
interconnecting planks (clench built) and an "improved
type" where these strength members have been excluded.
The "improvement" claimed fulfils the easy repair
criterion of many traditional shipbuilders. Otsu's values
clearly indicate where strength is lacking and where
material should be redistributed. From a wood technology
viewpoint, it would seem that this point was reached
to facilitate easy repair at the expense of the original
aim of strength. The fact is that, if wood is properly
protected from deterioration initially, it will last for the
life of the ship without constant repair due to biological
decay.
[212]
1. DUG-OUT CANOE
22 HJORTSPRING BOAT 400 BC
21 OBELISK CARRIER 1500 BC
3.1 ROMAN sVlIP 0-200 AC.
32 NYDAM BOAT T300AC
GOKSTAD SHIP 900 AC
41 'EUROPEAN-TYPE' 1850-1920 111 DIAGONAL CONSTRUCT ION
| 1 820 • 1 850
•~^r
511 DANISH FISHING VESSEL
1920-65
5.1,2 PACIFIC COAST FISHING VESSEL
1965
5.2 SKULDELEV-SHIP 1100AC
421 BEACH LANDING LIFE BOAT
1900-60
6.2 BEACH LANDING FISHING BOAT
1965
61 LAMINATED MEMBERS
NORWEGIAN VFRHAS 1955
7 FUTURE PROPOSALS (TENTATIVE)
Fig J. Historical review of wooden boat construction
Wood must be used as an engineering material if it
is to survive competition from other shipbuilding
materials. No material can be used successfully in
engineering unless its properties are well known. The
properties of wood have been investigated scientifically
for only 40 to 50 years by forest products laboratories all
over the world, but primarily in the USA and the UK.
Structural problems
An engineer's main aim is to create a perfect balance
between function, form and material. In shipbuilding,
the structural engineer's problem is to find a rational
method of structural design. The answers to this prob-
lem are constantly being refined for design of larger
commercial ships by strength rules, leadline rules and
other guidelines. Lewis (1959) says a rational design
can be reached only where:
• the functions and requirements can be explicitly
stated at the outset
• all loads to be expected can be determined and
combined
[213]
• structural members can be arranged in the most
efficient manner to resist the loads
• adequate but not excessive scantlings can be
determined, using a minimum of purely empirical
factors
The challenge for tomorrow's builders of wooden
ships is to break free of traditional thinking, to study the
teachings of the masters of centuries ago, to combine
this with modern knowledge and to progress from there
to improve and refine ship design without forgetting the
properties of their material. Studies of wood reveal some
excellent dynamic-strength properties, superior to other
materials. The overall distribution of properties shows
wood as more versatile than any other relevant material.
If modern knowledge is conscientiously applied, builders
in wood can look forward to being in a strong competitive
position for vessels up to 100 to 150 ft (30 to 45 m).
Progressive builders may even regain some of the ground
lost to steel in the upper part of this range.
This paper lists first the members affected by the
structural requirements of fishing boat function and
form. The properties of wood are then assessed to show
how well the use of wood, as an engineering material,
satisfies these requirements. First the structural properties
(mechanical) are discussed. It is shown how practical
design stress values are evaluated from standard test
values, taking all strength reducing factors for natural,
undecayed wood into account. Next the non-structural
properties (physical) are discussed. Environmental factors
which affect physical properties and relevant combina-
tions of these are mentioned. Biological decay, and pro-
tection from decay, are taken up separately. Strength
properties of wooden joints, members and complete
structures are outlined. Tentative design proposals are
given for round and V-bottom fishing boats, based on
the foregoing information.
STRUCTURAL FACTORS IN FISHING BOAT
FUNCTION
To function as a consistent and economic unit for
catching fish, a fishing boat must provide safe living and
working conditions for the crew. It must be stable and
strong enough to withstand rough treatment. Its material
must be resilient and have good impact strength prop-
erties. Since a fishing boat may be considered a platform
from which to catch, process and store fish, this "plat-
form" must be strong enough to support all the necessary
fish-finding and catching gear, plus processing equipment.
The platform must be steady enough to allow convenient
processing work. The hold must be big enough and
strong enough to contain an optimum catch.
The overall strength properties required for various
load conditions (at sea and when docked) determine
distribution and scantlings of these structural members:
Longitudinal deck and bottom
Diagonal side, deck and bottom
Transverse bulkhead and frames
Impact-load strength requirements determine dis-
tribution and scantlings of the following structural
members, depending on load directions:
• For horizontal longitudinal loads:
Longitudinal margin members and stringers
Local easily replaceable rubbing members
• For horizontal transverse loads:
Transverse bulkheads
Transverse frames
Longitudinal margin and stringers
Local easily replaceable rubbing members along
sides
• For vertical transverse loads:
Transverse bulkheads
Transverse deck beams
Longitudinal deck stringers
Pillars connecting deck and bottom
Easily replaceable rubbing members (keel shoe,
deck cover)
Arrangements of structural members must be a
compromise between the most efficient arrangement to
support the loads and the most practical arrangement to
achieve inexpensive construction, maintenance and
repair. Arrangement in the most efficient manner to
support the loads affects the following classes of struc-
tural members:
• Longitudinal members (tension and compression) :
Longitudinal bulkheads in or outside centreline
Keel
Margin at side-deck connections
Bilge and bottom
Deck along hatch coamings
Longitudinal deck and bottom planking
• Diagonal members in deck bottom and sides
(shear):
Diagonally laid side, bottom and deck planking,
firmly fastened to longitudinal margin
• Transverse members (compression and bending):
Transverse bulkheads
Deep web frames
Normal size frames and deck beams
• Perpendicular members (compression) :
Pillars connecting deck and bottom
The interrelation between longitudinal, diagonal and
transverse members depends on the efficiency, number,
type and distribution of joints and the efficiency, type
and distribution of joint fastenings.
STRUCTURAL FACTORS IN FISHING
BOAT FORM
Assuming a fixed gross tonnage or displacement, the
following factors affect initial cost: choice of length,
L/D, L/B, block coefficient, amount of material and
construction method. Running costs are affected by:
Resistance (choice of length, prismatic coefficient,
distribution of buoyancy along length, weight of light
ship)
Propulsion (propeller must suit hull under various
working conditions)
Maintenance and repair (costs should be small)
Influence of form upon strength.
[214]
Structural considerations include choice of principal
dimensions and ratios between dimensions. The choice is
dictated by the properties of the material when arranged
in the most efficient and practical manner. Factors in the
influence of form upon hull strength include L/D, L/B,
dead rise, bilge radius, distribution or curvature along
the hull and influence of sheer curvature.
It has been recognized for a long time that smaller
ships, due to their form, are relatively stronger than bigger
ships (Hajimu, 1961 ; Alexander, 1949; Bruhn, 1901/1904;
Oehlmann, 1963; Bureau Veritas, 1963; Grim, 1952/1953;
Pedersen, 1964). The shell action, greater dead rise and
other form factors should be used with advantage to
strengthen smaller ships, thus reducing scantlings and
increasing pay-loads.
SPECIFIC GRAVITY AND STRENGTH/
STIFFNESS PROPERTIES
In order to convert raw wood material into a hull
structure which fulfils form and function, the mechanical
properties and interrelated physical properties of wood
material must be known. Jt also must be known how the
environmental factors affect physical properties, which
in turn affect the mechanical properties, in order to
protect the relevant properties from deterioration.
Specific gravity
Specific gravity is an excellent indicator of mechanical
and physical properties. The substance of which wood is
composed is heavier than water. Its specific gravity is
about 1.56, regardless of species. In spite of this, the
dry wood of most species floats in water, because a large
part of the volume is occupied by cell cavities and pores.
Variation in the size of these openings and in thickness
of the cell walls causes some species to have more wood
substance than others, and therefore to have higher
specific gravity values, and greater strength.
It should be noted that specific gravity values are also
affected by gums, resins and extractives, which may
contribute slightly to certain strength properties. Fig 2
shows curves for average strength/stiffness properties
for species of varying specific gravity ("ideal" wood).
Formulae for the curves are given in table 1, taken from
the Wood Handbook, (US Forest Products Lab., 1955).
These curves are based on numerous strength tests of
more than 160 species of varying specific gravity. The
great difference between properties of dry and green
wood is easily seen.
Static-load properties increase considerably when
moisture content decreases (below fibre saturation
point), while dynamic-load properties decrease slightly
at the same time. Strength properties differ greatly
TABLE 1
Strength/Stiffness Properties as a function of Specific Gravity
Dry Hmu/(12/0)
moisture content
Green wood
Static bending:
Fibre stress at proportional limit
Modulus of rupture
Work to maximum load
Total work
Modulus of elasticity
Impact bending:
Height of drop causing
complete failure
Compression parallel to grain :
Fibre stress at proportional limit
Maximum crushing strength
Modulus of elasticity
lb/in2
kg/cm*
lb/in2
kg/cm2
in-lb/in3
cm-kg/cm11
in-lb/in3
cm-kg/cm3
1,000 lb/in3
1, 000 kg/cm2
in
cm
lb/in*
kg/cm2
lb/in2
kg/cma
1,000 lb/in2
1, 000 kg/cm"
Compression perpendicular to grain :
Fibre stress at proportional limit
Hardness:
end grain
lb/ina
kg/cm2
Ib
cm
Ib
cm
K
10.200
0.720
17.600
1.210
35.6
2.510
103
7.255
2,300
0.162
114
290
5.250
0.370
6.730
0.475
2.910
0.205
3.000
0.210
3.740
1.700
3.420
1.550
a
1.25
1.25
1.75
1.75
2.25
2.25
2.25
K
16.700
25.700
32.4
72.7
2.800
94.6
8.750
12.200
3.380
4.630
4.800
3.770
1.25
1.25
1.75
2
1.75
2.25
2.25
2.25
Curve No. in fig 2
dry green
side grain
The properties and values should be read as equations Property — K x G". For example, modulus of rupture for green wood
where G represents the specific gravity of oven-dried wood, based on the volume at the moisture condition indicated.
[215]
Id
2d
3d
4d
5d
6d
7d
8d
9d
lOd
lid
12d
lg
2g
38
48
5g
6g
7g
lOg
12g
17.600 G,"
Fig 2. Strength! Stiffness properties of wood (US Forest
Products Lab. 1955)
depending whether force is along or across the grain (see
for example, compression strength curves 7 and 10).
Specific gravity also indicates such physical properties
as swelling and shrinking. Denser species generally
shrink and swell more than lighter. Here, influence of
gums, resins and extractives may have a considerable
effect, as a large content of these generally reduces
swelling and shrinking (see also Kollman, 1951).
Specific strength
Peery (1950) gives formulae for calculating specific
strength values in tension/bending/compression for
typical aircraft sheet materials. Assuming that ship-
building materials may be calculated using the same
formula, values given in table 2 have been derived. The
values show :
• Weight ratios for tension members do not vary
greatly for the different materials
• For members in bending, the lower density
materials (plastic, wood) have a distinct advantage
• For members in compression (buckling), the
lower density materials (wood), have even
greater advantages than in bending
The values explain why Silka spruce has been so
widely used for bending and compression members in
aircraft structures.
MECHANICAL PROPERTIES (STRUCTURAL)
Static-load properties
In table 3, values are given for static-load properties,
obtained from laboratory tests with actual shipbuilding
materials (Marin, 1962). Jt is seen that different ship-
building materials are tested in different ways, depending
on the nature of the material. Crystalline, inorganic
materials such as metals are predominantly "tensile"
materials, while fibrous materials such as laminated
plastics and wood (organic) are "compression" and
"bending" materials. Therefore the static-load properties
cannot be compared directly. Although the static-load
TABLE 2
Specific strength/stiffness values
Material
F*
Ib/in2
x 10rj
kglcn?
Iblin*
w
kRlcnf*
Ex
Ih/iri2
10"
kg/cm*
Tension
Bending
Compression
Mild steel
6.00
4,230
.283
0.0079
30.0
2.11
2.85
7.07
13.90
Aluminium alloy
3.50
2.465
.100
0.0028
10.6
0.75
1.74
3.26
3.22
Laminated plastic
3.00
2.115
.050
0.0014
2.5
0.18
1.01
1.76
2.68
White oak
1.20
.845
.024
0.0007
1.8
0.13
1.21
1.33
1.39
Sitka spruce
0.94
.660
.015
0.0004
1.3
0.09
1.00
1.00
1.00
Formula: Tension
W^w,
£
Bending:
^I_Wl /
^
Compression :
?*-»'*!
M/ «,_V
r
F : Ultimate strength in tension
E : Modulus of elasticity
w : Density
Wj : Weight of amount of material No. 1 : resisting the same load
Wa: Weight of amount of material No. 2: resisting the same load.
• Values for F vary with cross section. The values shown arc only relative values for comparison.
[216]
TABLE 3
Static-load properties (from Marin, J. : Mechanical behaviour of Engineering materials, 1962)
(a) Mild steel and aluminium alloy
Tempera
i Density *£,r.<LM
Material In/in » Sip"
<k«/<™"> (ctcm,
C°) • H)«
Ib/in* (kiz/cm*) * 10" of claMi-
' B/ city in
^Cttcent- (b) Laminated pla.tic
\*9.e
tion i Ultimate strength Modulus of
in/2in i lb;in» (kg/cm1) * 10s 1 elasticity in
fg
| Ib/Vn »
Yield Ultimate (kg/cm*)
| - I0«
atenal | ^ w™^W
Mild 0.28 6.5
steel (0.0078) (11.7)
35 60 1 30
(2.46) (4.23) (2.11)
10 '
Laminated ! 3.0 11.2 9.X : 12
Plastic (0^1) (0 79) (0 6*)) (0 85)
1.70
Alum-
inium 0.10 12.8
Alloy (0.0028) (23.1)
i '
25 35 II
(1.76) 1 (2.46) (0.77)
~
(r) Ideal wood small clear specimens 2 • 2 in (5 5 cm)
Material g
j i
DC'
iccific ' Moisture
. •( ' content
avi ¥ per cent l-ihrc stress
; at prop, limit
: I0a
t Compression parallel to grain ' ' '^rt> sl^ss at
ding In/in (kg/cm ) |'h/in* (kg/cm1) ; P«°P- limit in • Ultimate
compression shear strength
; , perpendicular ! parallel to
Modulus of Modulus of fibre stress : Ultimate to grain grain
rupture elasticity at prop, limit strength Ih'in* ' Ih/in* (kg/cm1)
10' 10* 10 :i 10" ( kg/cm B) 10"
dry 0.68 j 12 i 8.2
white : : ' <°-5K)
15.2 . 1.78 , 4.76 7.44 , 1.32
(1.07) (0.125) (0.14) (0.52) «UW)
2.00
(0.14)
Oak green , 0.60 68 ; 4.7
i 1 : (0.33)
8.3 l.2> 3.0*1 3.56 0.83
(0.58) (0.09) (0.22) (0.25) (().(>(•)
1.25
(0.09)
1.15
(0.08)
0.7(>
(0.05)
; dry 0.40 12 6.7
Silk. ' ' <°-47'
10.2 1.57 4.78 5.61 > 0.71
(0.72) , (0.11) (0.34) (0.40) (0.05)
spruce cn ()j? 42 j ,j
; . i (023)
5.7 1.23 2.24 2.(»7 0.34 •.
(0.40) (O.(W) (016) (O.IM) (0.02)
TABLL 4
Dynamic load properties (damping properties)
Material Text method Type of stress ^^
^tlfmuxiim
is Internal friction in solids:
im ",', logarithmic decrement
Mild steel Torsion Pure shear
—
0.0049
Aluminium (aircraft alloy)
_..
0.0034
Wood: maple „ „
0.021
,, : Sitka spruce „
__.
0.0521
Wood: unspecified Flexure Bending
0.027
„ : Sitka spruce
_.
0.035
Wood: laminated birch
0.073
*Staypak— Yellow birch
—
0.128
*Comprcg— YB high-impact type
0.238
,, — YB low-impact type
0.108
—maple
—
0.239
Wood — laminated birch Compression Axial
84
0.002
88
0.012
93
0.063
Staypak— Yellow birch
86
0.0013
89
0.0465
92
0.1435
Compreg — Yellow birch
83
0.173
high-impact type
89
0.232
Compreg— Yellow birch „
74
0.045
low-impact type
87
0.157
90
0.172
Compreg— maple
89
0.0002
93
0.218
* Impr. wood products developed by US Forest Products Laboratory
Reference: Report Acn-18, US Department of Defence: "Wood in Aircraft Structures'*, 1951.
[217]
strength/stiffness properties of wood are smaller than
other materials, this need not be a disadvantage.
The larger cross section afforded by wood may better
withstand buckling failures in compression and bending
members than thin walled, built up, deep profiles in
metals, laminated plastic and plywood. The low values
for shear strength parallel with the grain may cause
troubles in deep beams, which may split along the
neutral axis if precautions are not taken (Beghtel, 1959).
Dynamic load properties
Fatigue: The fatigue resistance of a material may be
defined as the ability to sustain repeated, reversed, or
vibrational loads without failure (US Dept. of Defence
Report, 1951).
Shock and impact: Of all construction materials only
wood has the property of being able to sustain high
loads for short duration (Liska, 1950). Where metal
structures may buckle locally when exposed to impact
loads, wood members are able to take about 100 per cent
overloads (see: Load-duration).
Damping: Damping capacity may be defined as ability of
a solid to convert mechanical energy of vibration into
internal energy (heat). This causes vibrations to die out.
If a truly elastic material is subjected to a cycle of stress,
the stress-strain curve will be a straight line. If the
material undergoes reversible plastic deformations
during the cycle, the stress-strain curve will be a hysteresis
loop (fig 3). The area enclosed by this loop represents the
amount of energy expended during each complete
stress-cycle. Specimens subjected to cycles of stress
below the fatigue limit can dissipate an unlimited
quantity of energy as heat without any damage (fatigue
failures). In table 4 values are given for damping pro-
perties, expressed as logarithmic decrement for the
hysteresis loop. It also gives values for some improved
wood products, developed at the US Forest Products
FREQUENCE
Fig 3. Damping Properties
Laboratory, primarily intended for aircraft structures.
The damping properties of these refined wood products,
especially the compressed wood products (Compreg),
show extremely good values and indicate what levels
may be reached by utilization of wood and wood
products in future wooden ship design.
"Ideal" material
Values given for wood in the standard tests, bending,
compression, shear etc, are valid only for "ideal" wood.
"Ideal'* wood is a wood material similar in properties to
the small, clear specimens used in the tests. This wood is
tested under standard conditions such as those inter-
national conditions proposed by FAO (1954, 1958, 1963),
which are:
SOLID WOOD
ret. (I960 MOE
GUI- LAM.- WOOD
STEEL
STRESSES.
Fig 4. Variability in mechanical properties
[218]
ii H I
" " 8 5___ I
200 K
100 —
XXD01 £3001 COn bl .1 to 10.' 1OOT 1.000.' 1OOOO'. 10QOOO days.
Fig 5, 1 Mad-duration I stress-relation for wood, ref: US Forest Products Lah. (1955)
Wood moisture content (1) 12 per cent
(2) above 30 per cent (above
fibre saturation point)
Load duration 5 min
Temperature 68C5F (20 C)
Factors which affect mechanical properties
Variability
Variability in mechanical properties is common to all
materials. Fig 4 shows that the degree of variability,
expressed as standard deviation of the frequency dis-
tribution curve for the property investigated, differs
markedly with the type of material. Man-made materials
can be manufactured to within narrow limits of tolerance
for specified properties. The frequency distribution curve
is narrow with the mean value near the approached aim.
For natural materials, however, such as wood, the
curves are wide. More than 95 per cent of the strength
values are higher than the accepted near-minimum
value, which is three-quarters of the average for wood.
Thus the factor 3/4 is used to represent variability in
wood (Wood, 1960). It also is remarked how the wood
materials can be improved by utilizing the lamination
technique (Moe, 1961).
Load duration
Wood creeps under permanent loads. For long duration
use (27 years), the US Forest Products Laboratory
recommends reducing design strength values to 56 per
cent of standard test values. Fig 5 shows the load
duration working stress curve recommended by this
laboratory (Wood, 1951). The built-in overload pro-
perties are clearly seen when using the 27-year basic
stress values.
Moisture content
Fig 2 shows that wood moisture content has a marked
influence upon strength when wood is dried below fibre
saturation point (below about 24 to 28 per cent). How-
ever, this increase need not be too seriously considered
in practical design work, since checks and shakes
develop during drying which either partially or com-
pletely nullify the increase. Generally, the increase in
strength with drying is more marked in members of
small dimension (e.g. lamellae for glue-laminate mem-
bers), where internal drying stresses are of a low order of
magnitude and where checks are not as important as in
larger members. In the larger members, drying stresses
may cause serious strength-reducing checks.
Temperature
Influence of temperature on mechanical properties
need not be emphasized in design work. Although wood
properties are adversly affected by temperature, the
comparative effect in metal is many times greater, where
internal stresses due to temperature variations may
cause serious trouble due to brittle failures.
Combined factors
The relation between initial values of stress, time and
temperature and between stress, time, wood moisture
content (WMC) and temperature have only a minor
influence under normal service conditions. The practical
designer can ignore these relations without apprehension.
Mechanical properties of clear, structural components
Basic stress may be defined as the stress which can be
permanently sustained with safety for an ideal structural
component containing no strength reducing factors.
Alexander (1949) and Armstrong (1961) give basic
stress values for a wide range of structurally important
wood species.
Strength reducing factors (knots, cross grain, etc.)
Definition of defect
A defect in timber is an irregularity occurring in or on
wood that may lower any of its basic strength properties
(Newlin, 1924). One fundamental characteristic of wood
is the difference in its strength along and across the
grain. Wood is about 16 times as strong in the direction
of the grain as across the grain. This difference in strength
with different angle of the grain accounts for the serious
weakening effect of most defects.
Effect of defects on mechanical properties
Tension is affected most seriously by cross grain, knots,
cross breaks and compression failures. Since the outside
fibres on the convex side of beams have to sustain tensile
stresses, the load capacity of a beam depends especially
on the tensile strength properties of these extreme fibres.
Reduction in shear strength is due almost entirely to
shakes and checks which reduce longitudinal shear
[219]
strength properties considerably. The effect of cross-grain
and knots is much less in compression than in tension.
The compressive strength of wood parallel with grain
is six to ten times that of wood tested perpendicular to
the grain. For bearing strength at an angle to the grain,
the intermediate values given by Newlin (1939) should
be used (Hankinson's Formulae).
Working stress values
Working stress may be defined as the stress which can be
permanently sustained with safety by a structural
component of a particular grade. Sunley (1961) gives
working stress values for different species, graded after
content of defects.
Structural grading
Stress-grading of timber was developed to save work.
Each individual piece of timber is stress-graded and
stamped as it leaves the saw. Stress grade classes are
proposed for international standardization by FAO
(1954, 1958, 1963). Grading is a useful tool for designers
when designing beams and other members where
stresses vary along the length and across the section ; for
example, in glue laminate members with lamellae of
different grades in outer and inner layers.
Design stress values
Design stress may be defined as the stress which can be
permanently sustained with safety by a structural
component member under the particular service condi-
tions of loading. To obtain design stress from basic
stress for a particular species of a particular grade of
structural timber, used to fulfil a given structural function,
the procedure outlined above and described in detail by the
US Forest Products Lab. (1955) or the Nav-Ships Manual
Vol. IH (US Bureau of Ships 1957-62) should be fol-
lowed, provided great accuracy is afforded in each case.
Safety allowance for mechanical properties
No matter how accurately one calculates the inter-
related strength properties and strength reducing
factors, one will never have a precise estimate of all the
conditions under which the wood member must be
ultimately tested in service. An additional variable will
be the judgement of the designer. After all calculations
have been made, a "factor of safety" will arise. Wood
(1960) discusses this in detail for timber structures.
PHYSICAL PROPERTIES
(Non Structural, which may affect Structural)
Fire resistance, thermal conductivity or resistance;
effects of chemicals, electrical conductivity or resistance;
diffusivity, absorption, swelling and shrinking; biological
decay resistance (FAO, 1954).
Environments affecting physical properties
Physical : fire
Chemical: effects of sea water plus oxygen
Climatic: air moisture content, temperature, oxygen
Biological: wood-destroying organisms.
Effect of environment — relevant combinations
Fire/Fire resistance
Chemical/effect of chemicals: chemical corrosion rust.
Chemical/electric conductivity: electro chemical cor-
rosion
Moisture/diffusivity: drying or penetration of wood
Moisture/absorption
Moisture/swelling and shrinking
Biological/decay resistance.
Generally speaking, inorganic materials are affected by
physical and chemical factors, but unaffected by bio-
logical. The reverse can be said for the organic materials.
Tables 5 to 8 compare and judge the first six combina-
tions.
Biological decay
Because wood is a link in nature's life cycle, certain
biological organisms attack and devour it. Their food
comes from the cell wall content, cither cellulose or
lignin, or both, the same elements which give wood its
strength (cellulose — tensile strength; lignin — compres-
sion strength).
Effect of fungal decay
Cartwright and Findlay (1958) investigated reduction
in strength caused by a fungus (Polyporus hispidus)
growing in pure culture on ash wood. They found that
impact-bending properties (toughness) were rapidly
affected. After only two weeks' exposure to the fungus,
•fc reduction i mechanical prcprrtiw
IMPACT BLNDING^ TOUGHNESS)
30 WEEKS
Hg 6. Reduction in mechanical properties of ash to attack by
Polyporus hispidus, rcf: Cartwright and fr'indlay (1958)
there was a 20 per cent reduction in this property. After
12 weeks, the impact bending properties had dropped to
10 per cent of their original values (fig 6). The following
conclusions were drawn :
• Fungi causing brown rot, in which attack is
mainly directed against the cellulose, cause a
fairly rapid loss of strength
• Fungi causing white rot, in which all wood consti-
tuents are attacked, may also cause a rapid drop in
toughness in certain species, but this will occur
less rapidly than with brown rot
• Fungal infection works most rapidly to destroy
toughness. This is followed, in approximate
order of susceptibility, by losses in bending
strength, compressive strength, hardness and
elasticity
[220]
Classification
Attack rate 1 : unaffected
Resistance rate 1 : highly resistant
Factor of protection 1 .0
TABLE 5
Environmental factors (physical properties)
2: slightly affected 3: moderately affected 4: affected 5: highly affected
2: resistant 3: moderately resistant 4: non-resistant 5: perishable
0.8 0.6 0.4 0.2
TABLE 6
Fire/Fire resistance (thermal conductivity or resistance)
Steel Aluminium
unprotected insulated unprotected insulated
Laminated Plastic
Wood
Fire resistance
0.2
0.2-0.4
0.2 0.2 0.8-1.0 thick nibrs.
0.4 O.K mcd. thick
0.2 0.6 thin mbrs.
1.0
0.8
0.3
large section
med. thick
0.6 thin mbrs.
Thermal resistance (insulation properties)
0.2
0.2
0.2 0.8-1.0
1.0
TABI t 7
Chemical/Effect of chemicals (chemical corrosion)
Chemical/electric conductivity (electro-chemical corrosion)
Steel
Chemical resistance (chemical corrosion, rust)
, surface- Aluminium alloy
unprotected protected (sea water resistant)
0.2 0.4 0.8 0.8 1.0
Lam in.
Plastic
1.0
Wood
1.0
Electric conductivity (Electro-chemical
corrosion)
0.2-0.8 for metals, depending on:
(a) combination of dissimilar metals in underwater part of hull,
(b) difference in electric potentials, (c) exposed surface areas.
1.0
1.0
TABI.F. 8
Moisture/diffusivit y : (drying, penetration); Moisture/ Absorption ; Moisture/swelling and shrinking;
Wood
Steel Aluminium
Laminated
Plastic
Stabilized
Diffusivity
Absorption
Swelling and shrinking
1.0
1.0
1.0
1.0
1.0
1.0
0.9 1.0
0.6-1.0
depends on
manufacture
0.8 1.0
unprotected from surface-protected:
moisture paints, sheathing
0.2 0.8 depends on 0.2 0.8 depends on 0.6 1 .0 depends on
species species and specie** and
efficiency of efficiency of
surface- impregna-
protection tion
0.2 0.8 ditto 0.2 0.8 ditto 0.6 1.0
ditto
0.2-0.8 ditto 0.2-0.8 ditto 0.6-1.0 ditto
[221]
\
GROWTH-RATt/ SfcAWATFR- SALINITY- CONCENTRATION RCLAT'ONS
GROWTH-RATE:/ scAWATFR-TFMPERAiuRt -RELATIONS
Fig 7. Growth-rute/growth-condition-relations for marine-borer :
Teredo Navalix ref: Kollmann (7957)
Even though infected wood is hard and firm, one
cannot assume its strength as unimpaired.
Growth of wood destroying organisms
Wood-destroying organisms demand the following
conditions to grow: food stuff (cellulose and/or lignin
in cell walls), suitable hydrogen ion concentration of
food, suitable moisture content of wood, suitable
temperature level, available oxygen (for marine borers:
seawater). In fig 7 growth rate, as function of the above
mentioned factors, for marine borer (Teredo) and in fig
8 for fungi are shown (average values).
r.iKO'A 1 H HA It •• WOOJP Mi.'i'ilUHt CO'ITS-NI HtLATIONL
•O 66 86 1OB
1u ?O .10 40
IF MPrRAT'JKt- MLIAIION5
MO
fiO
159 F "
7U C"
WOV\ 'H- KATE"
rr,-! ->N-f.ONc.-fc N ; HA; -jr, F«! •. Af
77^ 5. Growth-ratelgrowth-condition relations for wood-
destroying fungi ref: Cartwright and Findlay (1958)
PROTECTION FROM BIOLOGICAL
DETERIORATION
If combination of all growth factors listed above is not
optimum, growth rate will be reduced or even stopped
(as in winter time). If only one of these factors is removed
permanently, growth cannot progress. As it is known
that wood with moisture content below 20 per cent
(e.g. interior wood) is too dry for growth of fungi, this
fact conscientiously should be utilized in constructive
protection.
Control of wood moisture content
In order to obtain a quality wood product, fast removal
of water in the log is essential. The following procedure
is recommended: Wood is felled in summer time when
moisture content is minimum ("sapless"). Immediately
after felling, the log must be sawn into lumber. Im-
mediately after sawing, lumber must be artificially dried
to a moisture content below 20 to 25 per cent (Verrall,
1949).
Until recently, winter-felled timber followed by natural
seasoning was thought superior to summer felled timber
followed by artificial drying. The introduction oi
modern wood drying techniques has reversed this. Now
artificially dried summer felled timber is superior. This
is because any degree of wood moisture content can be
obtained in a short period and wastage due to drying
defects and biological attacks during the drying period
can be reduced. Artificial drying can be started with a
sterilization process to kill all fungi and insects and can
be completed with chemical preservation treatment.
Moisture content of wood in boats
Hirt (1944) confirms that wooden boats can be protected
by controlling moisture content. With an electrical
moisture meter, Hirt investigated moisture content of
wood in more than 85 boats operating in fresh water. He
concluded: "Information obtained indicates that the
moisture content of exposed faces of most timbers in
tight, well ventilated, fresh-water boats is below fibre-
saturation point (24 to 28 per cent); that is, too low to
permit decay even below the waterline."
Since wood absorbs water most rapidly along the grain,
the critical points arc:
• At stem and stern where planks join these members
at the rabbet
• At butt joints in planks
• Where holes are bored perpendicular to the grain,
as for fastenings, shaft tubing and sea-water
connections
• Where ends of frames soak in bilge water
• Where heads of frames and beams are continually
wet, due to leakage along stanchions and deck
seams
It is at the above points where the use of fungi and
decay resistant wood species and timbers treated with
preservatives would be of most value. Plywood members
in contact with water are apt to absorb moisture more
rapidly than solid wood because of exposed end-grain
along edges. Poor ventilation encourages a dangerously
high moisture content.
When moisture content of boat timbers is above the
fibre saturation point (24 to 28 per cent), the cause can
be traced to one or more of the following reasons :
[222]
• Use of wood with too high an initial moisture
content (above 30 per cent)
• Leakage through seams when the ship moves in
seas (European type construction, especially de-
ficient)
• Leakage through butt joints, holes for fastenings,
sea-water connections, shaft tubing or other
points
• Soaking of members in poorly drained spaces
• Water condensation on cold surfaces, when air
moisture content is high
• Constant high air moisture content in poorly
ventilated spaces
The sources of these troubles can largely be eliminated
by proper construction and provision for good ventila-
tion during construction, service and storage.
Estimated WMC values for members
When wood is installed, its moisture content should
always coincide with that expected in service to avoid
open seams, loose fastenings and other factors which
reduce the lifetime of wood and seriously affect ship
strength. These estimated moisture content values for
members at installation can be taken as (Hirt, 1944):
20 to 25 per cent for planks below the waterline
15 to 20 per cent for planks above the waterline
15 to 25 per cent for interior strength members.
Manilkara sansibarensis
Ocotea rodiaei
Parinari holstii
Terminalia prunoides
Class C
Rrachystegia spiciformis
Cynometra webberi
Eucalyptus saligna
Funtumia latifolia
Ocotea usambarensis
Pygeum africanum
Vitex keniensis
Mimusops fruiticosa
Olea hochstetteri
Tectona grandis
Trachylobium verrucossum
Class D
Albizia glabrescens
Boinbax rhodognaphalon
Cephalospera usambarensis
Cupressus lusitanica
Cupressus macrocarpa
Entandrophragma stoltzii
Fagaropsis angolensis
Khaya spp
Newtonia buchananii
Ochroma lagopus
Podocarpus milanjianus
Pseudotsuga taxifolia
Ulmus proccra
TABLE 10
Natural durability of hearrwood species from attack by fungi
(European conditions)
Based upon tests with 2 .-: 2 in (5 \ 5 cm) specimen in fungi
infested soil, Savory (1961) gives the following classification of
species. The following rating for classification is used:
Grade of durability
Very durable
Durable
Moderately durable
Non-durable
Perishable
Expected service years
25 plus
15 25
10-15
5-10
minus 5
Classification
\
2
3
4
5
Ventilation of wooden boat structures
Further preventive protection is afforded by designing
wood structures to allow good ventilation of all wood
surfaces. Necessary and adequate ventilation equipment
is a vital part of constructive protection because it allows
wood to dry. Ventilation can be afforded either by
natural air (open system) (Evans, 1957) or artificially
conditioned air with a fixed moisture content and
temperature (closed system) (MacCallum, 1959).
TABLE 9
Natural durability of heartwood species from attack by Teredo
(African conditions)
Based upon tests in Teredo infested tropic waters, with 12 • 12 in
(30x30 cm) sections from 40 different species. McCoy Hill (1964)
gives the following classification of species tested. The following
rating for classification is used:
Attack rating
Resistance
rating
Service
expectancy
(years)
Classification
Trace to slight
very resistant to
8 plus
A
resistant
Slight to moderate
resistant to
5-7
B
moderate
Moderate to
moderate to
heavy medium
slight
144
C
Heavy
non-resistant
minus- H
D
Class A
Ambligonocarpus obtusangulas
Brachylaena hutchnsii
Erythrophleum guinrense
Dialium dinklagei
Dialium holtzi
Manilkara butugi
Manilkara propinqua
Class B
Acacia nigrescens
Afzelia quanzensis
Burkea africana
Chlorophora excelsa
Cassipourea malosana
Juniperus procera
Mimusops usambarensis
Scientific name
Dicorynia paraensis
Afrormosia elata
Afzelia spp
Lophira alata
Ocotea rodiaei
Chlorophora excelsa
Eucalyptus spp
Mimusops hechelii
Sarcocephalus diderrichii
Eucalyptus microcorys
Tectona grandis
Paratecoma peroba
Class 1
Common name
Basralocus
Afrormosia kokrodua
Af/clia
Azobe, Ekki
Greenheart
Iroko
Jarrah, Ironhark
Makor*
Opepe
Padauk
Tallowwood
Teak
Peroba do Campo
Class 2
Gossweilerodendron balsamiferum Agba
Castanea sativa Chestnut (sweet) true
Frcijo
Guarca
Mahogany (Central America)
Oak (American white)
Oak (European)
Pitch pine (Honduras)
Utile
Western red cedar
Port Orlbrd cedar
Cordia goeldiana
Guarea spp
Swietenia macrophylla
Quercus spp chiefly Q. alba
Quercus robur, Q. petraea
Pinus caribaea
Entandrophragma utile
Thuja plitaca
Chamaecyparis lawsoniana
Scientific name
Class 3
Lovoa klaineana
Cistanthera papaverifera
Pseudotsuga taxifolia
Entandrophragma angolese
Dipterocarpus spp
Anisoptera spp
Larix decidua
Khaya spp
Quercus spp, chiefly Q. borealis
Pinus sylvestris
Entandrophragma cylindricum
Common name
"African walnut"
Danta
Douglas fir, Oregon pine
Gedu nohor
Gurjun, Yang.
Krabak
Larch (European)
Mahogany (African)
Oak (American red)
Redwood, Norway pine
Sapelc
[223]
Vlmus procera
Ulmus thomasi
Ulmus americana
Vlmus glabra
Aucoumea klaineana
Picea abies
Picea glauca
Picea sitchensis
Abies alba
Class 4
Elm (English)
Elm (Rock)
Elm (White)
Elm (Wych)
Okoume, Gaboon
Baltic spruce (whitewood)
Canadian spruce
Sitka spruce
Silver spruce
Class 5
Ash (European)
Beech (European)
Birch, yellow
Maple, sycamore
Ramin
Balsa
Fraxinus excelsior
Fagus sylvatica
Betula lutea
Acer pseudoplatanus
Gony stylus bancanus
Ochroma lagopus
(Sapwood of all species can be classified as perishable.)
TABLL 11
Resistance to penetration (diffusive properties)
The ease with which wood can be impregnated with preservatives
is graded into four groups. Thomas (1964) gives the following list:
1. Extremely resistant: Even under prolonged pressure treatment,
absorption is sniall and there is little or no penetration laterally
and only very little into the vessels.
2. Resistant: Species are difficult to impregnate under pressure and
require long periods of treatment. Lateral penetration is usually
not more than ft to J in (3.2 6.4 mm), but in some species pene-
tration along the vessels is quite deep.
3. Moderately resistant: Fairly easy to treat. It is usually possible
to obtain a lateral penetration of i to i in (6.4 to 19 mm) in two
to three hours under pressure and the penetration of a large
proportion of the vessels.
4. Permeable: Species can easily be penetrated completely under
pressure without difficulty, and can be deeply penetrated by the
open-tank process (non-pressure treatment).
Species classified after penetration ability: (heartwood only)
Scientific name
Afrormosia data
Guarea spp
Chlorophora cxcelsa
Khaya spp
Swietenia macrophylta
Mimusops hechelii
Shorea spp
Quercus rohur
Tectona grandis
Entundrophragma utih
Class 1
Common name
Afrormosia kokrodua
Guarea
Iroko
African mahogany
American mahogany
Makore
Red me ran ti
Oak (European white)
Teak
Utile
Class 4
Beech (European)
Birch yellow
Maple, sycamore
Ramin
Balsa (for core in sandwich-mbn
only)
(Sapwood of all species can be classified as permeable)
Fagus sylvatica
Betula lutea
Acer pseudo-platanus
Gonystylus bancanus
Ochroma lagopus
Use of heartwood
To protect the dead cells in heartwood of certain living
trees from attack by biological organisms, a natural
preservation with more or less effective toxic components
takes place in the cell walls. The use of heartwood from
such species provides certain protection.
Wood species can be chosen which have moderate tc
good natural biological resistance properties. Table S
lists some wood species classified according to natural
resistance to attacks by the marine borer Teredo in the
tropics (McCoy-Hi 1 1, 1964). Further protection against this
worm is given by sheathing of glass or nylon fibre plastic
(UK, war against — 1965). Table 10 lists some natural
durable species which are resistant to wood destroying
fungi. Species in the higher classes should be used in
combination with control of wood moisture content
(Savory, 1961; Hartley, 1960; Krause, 1954; Morgan,
1962; Hillman, 1956).
Chemical preservatives
The most effective protection for moist wood is tc
permeate it with preservatives which, in effect, poison
the food in the cell wall on which wood destroying
organisms feed. For sapwood of all species non heart-
wood, woods formerly classified as perishable and
woods for which the full cross section can be penetrated
and protected, a pressure-preservative treatment is
possible. This treatment will produce superior material
lor wooden ships of the future. The material thus
obtained will be even safer to use than the natural
durable species because the grade of protection afforded
by treatment can be controlled. Table 11 lists wood
species which can be treated easily and protected b>
penetration with chemical preservatives (Thomas, 1964),
Class 2
Gossweilerodenelmn balsamiferum Agba
Douglas fir, Oregon pine
Elm (Wych)
Elm (Rock)
Western Hemlock
Gurjun, Yang
Larch (European and Japanese)
Obeche
Sapele
Baltic, Canadian, Sitka spruce
Pseudotsuga taxifolia
Ulmus glabra
Ulmus thomasi
Tsuga hetrrophylla
Dipterocarpus spp
Larix decidua
Triplochiton scleroxylon
Entandrophragma cylindncum
Picea spp
Thuja plitaca
Chamaecyparis nootkatensis
Fraxinus excelsior
Ulmus procera
Nauclea diderrichii
Araucaria angusti folia
Pinus caribaea
Pinus strobus
Chamaecyparis lawsoniana
Pinus sylvestris
Quercus borealis
Western red cedar
Yellow cedar
Class 3
Ash (European)
Elm (English)
Opepe
Parana pine
Caribbean pitch pine
Yellow pine
Port Orford cedar
Norway pine, Redwood
Oak (American red)
JOINTS
Apart from decay, the greatest weakness in wooden
structures lies in the joints (see Timber Engineering Co.,
1957). In mechanical fastened joints the stress in one
wood member is transmitted to another through point
transmitting fastenings. Stress is naturally concentrated
around these fastenings (Ichikawa, 1955). In glued
joints, the opposite is true; there will be no stress con-
centration. Rather, stresses will flow uniformly from
member to member. Homogeneous joints, therefore, are
superior to point transmitting fastened joints. The best
joints are the homogeneous glued joint and the worst
the poor single drift bolt or round iron bars which
cannot even be post-tensioned, as can be done with
screwbolts (Yoshiki, 1959).
Should mechanical, rather than glued, joints be pre-
ferred, some effort should be made to approach the
homogeneous joint as much as possible, to avoid the
[224]
stress concentration by using post-tensioned screwbolts
in connection with ring or grid connectors (dowels). A
system of closely spaced smaller gauge fasteners such as
nails, screws and spikes is even better than a few big
widely spaced bolts. Gusset plates of plywood or Com-
preg should be used to increase the joint area available
for nailing. The minimum thickness of a given metal
fastening for small gauge fastenings for use in sea water
will often be determined from the risk of corrosion
(Baehler, 1949; Farmer, 1962; Morgan, 1962). Two
metals of different electrical potential must not be used
in the same structure because a circuit is established
and the most electro positive metal will deteriorate
(Packman, 1961). The risk of corrosion may be serious
even for heavy bolts and spikes. Such metal failure may
be as damaging to the structure as failure of the wood
material due to fungi or marine borers. The key to better
utilization of wood properties seems to be the water
resistant glues.
STRUCTURAL MEMBERS
Glue-laminated members
Possible types of glued structural members include
glue-laminated members, structural plywood, structural
sandwich and particle boards (Curry, 1957; Erickson,
1959; US Forest Products Lab., 1955; Kollman, 1951).
Some significant advantages of glued-laminated members
over green solid wood members are (Freas and Sclbo,
1954):
• Ease of fabricating large structural elements from
standard commercial lumber sizes
• Laminations are thin enough to be seasoned
readily before fabrication, giving more freedom
from checks or other seasoning defects of large
one-piece wood members
• Individual laminations can be dried to provide
members thoroughly dried throughout, permit-
ting the designer to make calculations on the
basic strength of dry wood for dry service condi-
tions
• Opportunity to design in accordance with
strength requirements, structural elements that
vary in cross section longitudinally
• Possible use of lower grade material for less
highly stressed laminations without adversely
affecting the structural integrity of the member
• Large laminated members may be fabricated from
small pre-assembled components which may be
necessitated by the non-availability of large high
grade timber
Certain factors, mostly costs, are involved in pro-
ducing glue-laminated members which are avoided in
solid wood timbers. Some are:
• Preparation of timber for gluing and the gluing
itself usually raises the cost of the final laminated
product above that of solid green timbers
• A longer period is required to cut, season and
laminate timber than is required to produce solid
green timbers
[225]
• The laminating process requires special equipment,
plant facilities and fabricating skills not needed to
produce solid green timbers
• Production of glue-laminated members requires
several additional operations and extra care to
ensure a high quality product than solid members
• Large curved members are awkward to handle and
ship by usual carriers
Freas (1956) Ketchum (1949), Moe (1961), Selbo
(1957), and UK Timber Research and Development
Association (1960) give more information on designing
glue-laminated members. Lindblom (1947) gives a
general description of manufacturing 148-ft (45-m)
wooden ships with glue-laminated strength members.
Bent wood members
Bent wood may be an alternative lo curved members of
smaller dimensions. Of the several methods commonly
used to produce curved parts of wood, bending is the
most economical in material, the most advantageous for
members requiring strength, and perhaps the cheapest.
Long experience has evolved practical bending
techniques and it requires skilled craftsmen to apply
them. Yet commercial operations often sustain serious
losses because of breakage during the bending operation
or the fixing process that follows, it has long been felt that
far more reliable information is required about the
following: criteria for selection stock; better methods of
seasoning and plasticizing wood ; more efficient machines;
techniques for drying and fixing the bent part to the
desired shape; the effect on the strength properties,
before competent bending can be performed. (Pillow,
1951; MacLean, 1953; US Bureau of Ships, 1957-62). A
special handbook has been issued where all problems
in wood bending are dealt with (Peck, 1957).
When bending it is very important to avoid over-
stressing the fibres on the convex side, which may cause
- r
Fig 9. Load deflection curves for frame-members of same
cross-section 2.0 in / 2.6 in (50 mm/.66 mm), ref: Luxford
and Krone (1956). The conversions in the sketch shall he 1370
and 430 mm respectively
tension failures. On the concave side the fibres are
compressed considerably, thus spoiling the initial
strength of the material. Therefore, the stress/strain
properties of bent wood cannot be compared with the
properties of natural material in straight solid or lami-
nated wood. On the other hand, the stress/strain prop-
erties of bent wood may not be disadvantageous if
properly utilized, as these characteristics (in bending
when decreasing the curvature) are very similar to those
of mild steel (in tension) (fig 9). Bent wood will yield
just as mild steel, and will be able to absorb several times
as much energy as laminated curved members before
failure for loads which tend to strengthen the members
(same cross section assumed) (Luxford and Krone, 1956).
This may be a useful property for bent frames for beach
landing boats, as discussed by McLeod.
COMPARISON OF STRENGTH PROPERTIES
OF STRAIGHT AND CURVED MEMBERS
Straight keel members
Luxford and Krone (1946) investigated strength/stiffness
properties of laminated, solid and bolted keel members
for a 50-ft(15-m) motor launch. The following conclusion
is given in the report:
Though the bolted, scarfed member had an uncom-
monly slight slope of the scarf (1 in 18), the strength in
bending was only about half the strength of the solid
keel member with no joint. Laminated keel members
with plain scarf joints of slope 1 in 12 in each lamination,
sustained a maximum load in bending about 20 to 25
per cent higher than solid sections without joints.
Laminated keel members with serrated scarf joints of the
dimensions used, and located as in the test, were approxi-
mately the same bending strength as solid section without
joints.
Curved frame members
Luxford and Krone (1956) also compared strength/
stiffness properties of laminated and steam-bent frame
members for a 50-ft (15-m) motor launch. If there is a
choice between transverse frame members in laminated
or solid bent wood, the important performance points
given in the conclusion should be considered. Bent
frames of the patterns tested are equalled in strength and
stiffness by laminated frames whose cross sectional
dimensions are each seven eighths as great as those of
bent frames. Strength and stiffness of bent frames may
be expected to decrease with an increase in the relative
curvature (ratio of depth or radial dimension of the frame
to the radius of curvature) and the factor seven eighths is
not applicable to frames whose relative curvature
differs greatly from that of the frames tested.
STRENGTH PROPERTIES OF COMPLETE
STRUCTURES
Wooden vessels can be contemplated as large nailed
laminated beams from a strength/stiffness point of
view (Otsu, 1960; Takehana, 1960; Tsuchiya, 1963).
Therefore an investigation of the following compound
beams is of great interest. The following performances
should be investigated.
I horizontal strakes
Indirectly
Harada et al (1950) investigated the strength properties
of "European-type" vessels, both experimentally and
theoretically, in order to improve the longitudinal
strength properties of wooden vessels built as the
European type ship. The distribution of internal stresses
in such a structure were calculated theoretically based
upon certain approximate assumptions (Yushiki, Take-
hana, 1957). Harada et al. (1954) found that the critical
points were the apparent slip between wooden members
due to "yielding" of material round the fastenings.
Other strength investigations of members were carried
out (Yoshiki, 1956). Strength/stiffness properties of
double sawn frames subjected to simple bending
loads were investigated analytically and experimentally.
The properties were all dependent on the number and
distribution of the fastenings, and yielding around the
fastenings.
Strakes directly connected
In order to improve the longitudinal shear strength of a
nailed laminated beam, keys and dowels may be inserted
between the strakes. Harada proposed this for improve-
ment of longitudinal strength properties of the European
type vessel, and found that stiffness properties of the
vessel were increased considerably. He also recommended
the introduction of keys rather than closer spacing of the
frames.
Granholm (1961) investigated strength /stiffness
properties of nailed laminated beams and found that the
properties of such a member depend on the factor
"modulus of displacement" (between wooden members),
which confirms Harada's investigation. The value of this
factor can be determined by simple detail tests, and
depends on the gauge of nails used and the hardness
(specific gravity) of wood used. The factor also depends
on the magnitude of the load applied. The modulus of
displacement is thus not constant but decreases as the
load increases, or varies inversely as the load varies in a
ship structure.
Boats and other structures built up from narrow
strips, edge nailed together, are another example of a
compound beam, the strength/stiffness properties of
which are similar to Granholm's beam(s). Shear
strength properties along the strips can be improved
considerably by gluing the strakes together, as stresses
then will flow uniformly over the continuous glue line
instead of being concentrated around the fastenings.
Due to the relatively thin shell thickness, the lateral
strength depends on a correct combination of curvature,
shell thickness, frame distribution and scantlings,
proportional to the margin member conditions. Such a
boat structure in the smaller size range (up to 50 or 60 ft
(15 to 18 m), might show promising possibilities as
claimed by Hamlin (1954, 1959) and Pedersen (1964).
Instead of nails, internal wires may be used. Goodman
(1964) investigated the strength/stiffness properties of
cylindrical shells built from strips and "frozen" into the
desired curvature (concrete moulding form) by means of
post-tensioned wires. Goodman's investigation confirms
Granholm's statement, but some remarkable points
should be mentioned.
[226]
In all tests, there was an immediate relaxation of pre-
stress after tensioning. It appeared that initial moisture
content of the panel had a considerable influence on the
magnitude of this initial relaxation. A rather surprising
finding of the tests was the fact that increases in moisture
content increased the stress level (tension stresses in
wires) only slightly, if at all.
Beam with diagonal web-members
In order to obtain better strength/stiffness properties of
large, compound beams (wooden-ship structures), Gran-
holm (1961), Harada (1950), Hishida (1957-59), Doyle
(1957) andBrosenius (1947) recommend the use of double
diagonal web plates in which the shear stresses do not
cause large deformations which may be damaging to the
structure. (See also Lindblom, 1963).
Instead of double layer or multi layer diagonally laid
planks, plywood panels may be a solution, if developable
surfaces are acceptable. Plywood panels with the grain
running in a diagonal direction would be advantageous.
They might also easily be manufactured in longer lengths
than at present and more easily scarfed in diagonal
directions.
WOOD IN COMBINATION WITH OTHER
MATERIALS
The following possibilities may be considered as materials
for use in combination with glued laminated members
and complete wood structures:
• Unidirectional glass or nylon fibre fabrics glued to
outer laminations with polyester resins
• Aluminium foil between laminations
• Aluminium strips glued to outer laminations
(tensile material)
• Post-tensioned stainless steel internal wires (rein-
forced wood)
• Sheathing or surface cover of wood for strengthen-
ing and for protection from decay and borers and,
internally, to provide clean surfaces in the hold or
below the waterline
Granholm (1954) describes in detail the technical
possibilities of combining timber and high strength steel,
that could be used in practical engineering as light
weight beams and girders.
Composite ships may be made in two ways. One
method is to have a rigid skeleton of steel or aluminium
profiles (Hishida, 1959) and sheeting of one or several
layers of wood planking, plywood panels, covered wood
or plywood sheeting. The other, the rigid skeleton may be
glue laminated wooden members, plywood members
(built up beams or web frames) or bent members and
the sheeting either of FRP, aluminium or plywood
"planking" covered with fibre plastics.
TENTATIVE DESIGN PROPOSALS
Round bottom vessels 20 to 50 ft (6 to 15 m)
Ideal structure: The ideal is one piece construction
without joints. An example is the moulded plywood
hull as produced from the hot or cold mould process
(Oehlmann, 1963), fig 10.
Construction on longitudinal frames: After erection of
a skeleton of longitudinal glue-laminated frames and
transverse bulkheads, the skeleton is covered with two
layers of double diagonal plank sheeting, with a steep
orientation of layers, and finished with a fibre-plastic
cover (fig 1.7).
Construction on transverse frames: The skeleton
consists of transverse glue-laminated frames and longi-
tudinal stringers (beam shelves) along margins. The
skeleton is covered with two layers of double diagonal
plank sheeting, with a flat orientation of layers, and is
finished with a fibre-plastic cover, (Johnson, 1953)
fig 1.7.
Strip construction: Strips may be laid in one or
several layers, either longitudinally or diagonally,
supplemented by longitudinal members (Hamlin, 1954,
1959; Pedersen, 1964).
Fig JO. Glued built-up shell. (K. Oehlmann, Travemunde)
[227]
H2
Fig 11. Longitudinal glue-laminated frames. Transverse bent-wood
frames
Round bottom vessels 50 to 150 ft (15 to 45 m)
"Ideal" structure: The "ideal" is a one piece construc-
tion built up of various closely connected layers. An
example is the 700-ton Vision built in 1850 (Murray,
1851), fig 1.3.
Construction on longitudinal frames: The skeleton con-
sists of deep longitudinal glue-laminated frames, trans-
verse bulkheads and web frames, and is used as a form
for transverse bent frames which are closely spaced and
permanently fixed to the longitudinal glue-laminated
frames. It is covered with two layers of double diagonal
plank sheeting at a 45° angle and is finished with a fibre-
plastic cover (Isherwood, 1908; Flodin, 1919; Brosenius,
1947), fig 11.
Construction on transverse members: The skeleton con-
sists of deep widely spaced frames and transverse bulk-
heads. This transverse system is covered with closely
spaced longitudinal (glue-laminated) stringers of smaller
cross section. Finally this skeleton is covered with two
layers of double diagonal plank sheeting at a 45° angle
and is finished with a fibre-plastic cover (Evans, 1957),
fig 12.
Vee bottom vessels 20 to 100 ft (6 to 30 m)
The universal strength member for all sizes is the pre-
assembled, built up, transverse frame and beam. The
corners are assembled with plywood or Compreg gusset
plates. Fastenings may be either stainless steel bolts and
connectors, or closely spaced nails. The straight solid
wood members should be pressure treated with chemicals
for protection.
Fig 12. Transverse glue-laminated frames. Longitudinal glue-laminated
stringers
Fig 13. V-frame vessel
After erection of a skeleton of the widely spaced frame
and beam members, this is covered with longitudinal,
closely spaced stringers. Chines are built up from
square strips to provide an adequate shear transmitting
area. Finally this is covered with plywood panels, if
surfaces are developable, or if not with two layers of
double diagonal plank sheeting at a 45° angle. The hull is
finished with a fibre-plastic cover (fig 13).
Acknowledgment
The author wishes to express his thanks to the following persons
for the inspiration and help given in preparing this paper: Prof. P.
Moltesen, The Danish Wood Council, Copenhagen, Denmark;
Prof. J. Moc, Department of Ship Structural Design, Technical
University, Trondheim, Norway; Research workers at Forest Pro-
ducts Laboratory, Madison, Wisconsin, USA; Forest Products
Research Laboratory, Aylesbury, Buckinghamshire, England; and
at the Fishing Boat Laboratory of Japan, Tokyo, Japan; and Mr,
K. £. Oehlmann, Travemiinde, Germany, for kind permission to
present fig 10.
[228]
Aluminium and its Use in Fishing Boats
by C. W. Leveau
Emploi de raluminium dans la construction des bateaux de peche
L'aluminium cst tenace, resilient et absorbe tr6s bicn les coups. Les
bateaux en aluminium insistent bien aux chocs produits par les
vagues, les accostages brutaux, ou les collisions avcc des &paves, car
Taluminium cede — puis rcvient a sa forme initialc— davantage que
la plupart des autres mat&riaux employds en construction navalc.
Certains alliages 16gers sp6ciaux posscdent unc haute resistance a
la corrosion marine et sont aptes au soudage, la ?.one de soudure
conservant de bonnes propriit6s physiques. Aussi les bateaux de
p6che en aluminium sont-ils maintenant soudes, a 1'exception dc
petits bailments a moteur hors-bord.
Les bateaux en aluminium n'ont pas besoin de peinture, et aux
Etats-Unis d'Am6rique la plupart nc sont pas points. Lorsqu'on
applique une couche de pcinture, c'est uniquement pour des motifs
d'ordre esth&ique.
L'aluminium sert ggalement a la construction des roufs dc
nombreux bateaux de p£che de fort tonnage a coquc en acier ou en
bois. II est egalement trcs employe pour la confection des cloison-
nements et revetemcnts de cales a poisson.
£1 aluminio y su aplicaci6n en los barcos de pesca
El aluminio es duro, elastico y ticne una gran rcsistcnda a las
abolladuras. Las embarcacioncs dc aluminio aguantan perfecta-
mcnte los golpes dc mur y los cheques violentos al atracar o contra
dcrrelictos u objctos flotantes, porque este material es mas flexible
quc la muyoria dc los utilizados en la construccion naval cuando se
somctcn a esfuerzos dc choque.
Hay aleaciones marinas especiales y muy rcsistentes a la acci6n
corrosiva del agua salada que al soldarlas adquieren elevadas
propicdades fisicas en la /ona soldada; asf, salvo las pequenas
embarcaciones con motor fucra de bordo, los pesqucros de aluminio
se sueldan hoy dia.
Los pesqucros de aluminio no necesitan pintura, y la mayoria de
los utilizados en los Estados Unidos no la llevan. Si se les pinta es
solo por motivos de est6tica.
El aluminio se emplea tambi6n para la cascta del pucntc en
muchos pesqucros grandcs con casco de acero o madcra. Para los
mamparos de los ranchos y como forros de las bodegas del pcscado
se usa tambidn mucho el aluminio.
AUM1NIUM is tough, resilient, and has great
dent resistance. Aluminium boats stand up well
when battered by slamming action of waves or
the impacts of hard docking or even when colliding with
debris. This is because aluminium deflects farther than
most other boat-building materials when subjected to
impact stress. The energy of impact is dissipated more
gradually than it is in u less ductile material. Also,
aluminium has a higher clastic limit than, say, the
polyester laminates, hence it will absorb far more impact
energy before failure.
More particularly, as compared with steel, some types
TABLE 1
Mechanical property limits for plate. Comparison chart for H112, -H113 and -H321 tempers
Alloy and
temper
Thickness
inches mm
Minimum
tensile strength
lb/in2 kg/om2
Minimum
yield strength
lb/in2 kg/om2
Elongation % in
2 in (50.8 mm)
5052-H112
0.250-0.499 6.4-12.7
0,500-2.000 12.7-50.8
2.001-3,000 50.8-76.2
28,000 1,970
25,000 1,760
25,000 1,760
7
12
16
5154-HH2
0.250-0.499 6.4-12.7
0.500-2.000 12. 7-50.8
2.001-3.000 50.8-76.2
32,000 2,280
30,000 2,110
30,000 2,110
18,000 1,270
11,000 770
11,000 770
8
11
15
5086-H112
0.250-0.499 6.4-12.7
0.500-1.000 12.7-25.4
1.001-2.000 25.4-50.8
2.001-3.000 50.8-76.2
36,000 2,540
35,000 2,470
35,000 2,470
34,000 2,400
18,000 1,270
16,000 1,130
14,000 990
14,000 990
8
10
14
14
5083-H113
0.250-2.000 6.4-50.8
44,000 3,100
31,000 2,180
12
5456-H321
0.250-0.624 6.4-15.8
0.625-1.250 15.8-31.8
1.251-2.000 31.8-50.8
46,000 3,240
46,000 3,240
44,000 3,100
33,000 2,320
33,000 2,320
31,000 2,180
12
12
12
[229]
TABLE 2
Mechanical property limits. Sheet and plate comparison chart for -0, H32, -H34, -H36 and -H38 tempers
Alloy
Uin tenoile
Min yield
Elongation in 2 in (50.8 ran), % minimum
and
temper
Thickness
inches mm
strength
lb/in2 kg/on2
strength
lb/in2 ke/omS
.020- .032- .051- .114- .129- .162- .250- .500- 1.001- 1.501-
.031 .050 .113 .128 .161 .249 .499 1.000 1.500 2.000
5052-0
5154-0
5086-0
All
All
All
25,000 1,760
30,000 2,110
35,000 2,460
11,000 775
14,000 985
18 20 20 20 20 20 18 18 18 18
12 14 16 18 18 18 18 18 18 18
15 15 18 18 18 18 14 14 14 14
5083-0
.051-1.500 1.27-3^.0
1.501-3.000 38.0-76,0
3.001-5.000 76.0-127.0
5.001-7.000 1?7. 0-178.0
7.001-8.000 178.0-203.0
40,000 2,820
39,000 2,740
38,000 2,670
37,000 2,600
36,000 2,530
18,000 1,270
17,OOO 1,2OO
16,000 1,130
15,000 1,050
14,000
16 16 16 16 16 16 16
16
5456-0
.051-1.500 1.27-38*0
1.501-3.000 38.0-76.0
3.001-5.000 76.0-127.0
5.001-7.000 127.0-178.0
7.001-8.000 178.0-203.0
42,000 2,950
41,000 2,880
40,000 2,820
39,000 2,740
38,000 2,670
19,000 1,340
18,000 ,270
17,000 ,200
16,000 ,130
15,000 ,050
16 16 16 16 l(i 16 16
16
5052-B32
5154-H32
5086-H32
5083-H32
All
All
All
All
31,000 2,180
36,000 2,530
40,000 2,820
45,000 3,170
26,000 ,830
28,000 ,970
34,000 2,500
5 5 7 9 9 9 11 12 12 12
5 5 8 8 8 8 12 12 12 12
6 6 8 8 8 8 12 12 12 12
8 8 10 10
5052-H34
5154-B34
5086-H34
5083-H34
SOS 2-41 36
All
All
All
All
All
34,000 2,390
39,000 2,740
44,000 3,100
50,000 3,520
•*7 QOO 2 60O
29,000 2,040
34,000 2,500
39,000 2,740
4 4 6 7 7 7 10 10
4 4 6 6 6 7 10 10
5 5 6 6 6 6 10 10
6688
5154-*36
5086-B36
All
All
42,000 2,950
47,000 3,310
32,000 2,260
38,000 2,680
33455
44666
5052-H38
5154-H38
All
All
39,000 2,740
45,000 3,170
35,000 2,46O
3444
3345
TABLE 3
Recommended practices for jig welding of aluminium alloys
Material
thickness
inches ran
Welding
position
Joint design
( bevel;
Current
Amps - DC
Arc
voltage
Filler wire
diagram
inches mm
Argon** gas
flow CFH
No. of
passes
3/32 2.36
Flat
None
70-110
100-120
16-22
18-22
1/32 0.76
3/64 1.19
30
30
1
1
l/o 3.18
flat
Horiz./vert.
Overhead
None
None
None
110-130
100-120
100-120
20
20
20
3/64 1.19
3/64 1.19
3/64 1.19
30
30
40
1
1
1
1/4 6.35
Flat
Horiz./vert.
Overhead
Flat
None /single
Single
Single
None
200-225
170-190
180-200
220-250
26-28
26-25
26-28
28-30
1/16 1.57
1/16 1.57
1/16 1.57
1/16 1.57
40
45
50
HO
1
2/3
2/3
2
3/a 9.53
Flat
Horiz./vert.
Overhead
Flat
Single/double
Single/double
Single/double
None
230-320
180-235
200-240
260-280
26-28
26-28
26-28
28-30
1/16 1.57
1/16 1.57
1/16 1.57
1/16 107
50
50
50
00
1/2
3
5
2
1/2 12.70
Flat
Horiz./vert.
Overhead
Flat
Single /double
Single/double
Single/double
None
280-340
210-250
225-275
2(30-320
26-30
26-30
26-30
30-32
3/32 2.38
1/16 1.57
1/16 1 .57
1/16 1.57
50
50
80
80
2/3
3/4
8-10
2
1 25-40
Flat
Horiz./vert.
Overhead
Flat
Single/double
Single/double
Single/double
None
320-420
P25-285
225-285
390-400
26-30
26-30
26-30
35-37
3/32 2.38
1/16 1.57
1/16 1.57
1/16 1.57
60
60
80
80
4-5
4-6
15 +
2
2 50.80
Flat
Single/double
350-450
26-30
3/32 2.38
60
12 +
3 70.20
Flat
Single /double
350-450
26-30
3/32 2.38
60
20 +
* Gas flows for helium are slightly higher than for argon
[230]
Representative i
TABLE 4
! of inert-gas metal-arc welded joints in aluminium alloys 5086 and 5083
Alloy and ,
tamper '
Gauge
inches mm
Tensile
strength
It/in2 kg/am2
Yield
strength i/
lb/in2 kg/on2
Elongation !
% in 2 in
(50.8 mm)
Joint
efficiency
%y
Location of fracture
tested with beads
in place
5086, 0
1/4 6.35
3B,000 2,680
18,000 1,270, 15.4
100
Parent plate, fusion line
5086, H112
1/4 6.35
38,000 2,680
19,000 1,340
14.0
100
Parent plate, fusion line
5086, H34
1/4 6.35
38,000 2,680
21,000 1,430
8.3
ttO
Parent plate, fusion line,
weld metal
5086, H112
1/2 12.70
39,000 2,740
21,000 1,480
11.4
100
Fusion line
5086, H34
1/2 12.70
39,000 2,740
21,000 1,480
12.0
84
Fusion line
5086, H112
3/4 19.05
41,000 2,U80
21,000 1,4»0
16.7
100
Fusion line, parent plate
Tested with beads
machined off
5086, 0
1/4 6.35
35,000 2, 470
17,000 1,200 12.5
100
Fuaion line
5086, H112
1/4 6.35
37,000 2,600
17,000 1,200
14.3
94
Fusion line, weld metal
5085, H34
1/4 6.35
37,000 2,600
18,000 1,270
12.9
78
Fusion line, weld metal
5086, H112
1/2 12.70
39,000 2,740
20,000 1,410
16. !>
100
Fusion line
5086, H112
3/4 19-05
39,000 2,740
20,000 1,410
16. 8
100
Fusion line, weld metal
Tested with beads
in ulace
!
5083, 0
1/4 6.35
43,000 3,030
20,000 1,410
16.2
100
Fuaion line, parent plate
5083, H113
1/4 6.35
46,000 3,240
24,000 1,690
16.6
100
Parent plate
5083, H113
1/2 12.70
45,000 3,170
22,000 1,550
12.5
88
Fusion line
5083, H113
3/4 19.05
45,000 3,170
23,000 1,640
16.0
97
Fuaion line
Tested with beads
machined off
5083, 0
1/4 6.35
40,000 2,blO
20,000 1.410
15-3
97
5083, H113
1/4 6.35
42,000 2,950
22,000 1,550
14.0
91
Weld metal
5083, H113
1/2 12.70
42,000 2,950
21,000 1,450
16.3
93
Weld metal
5083, H113
3/4 19-05
42,000 2,950
21,000 1,4BO
18.3
90
Weld metal
i
JL/ At 0.2$ offset
2/ Based on the typical tensile strength shown in the Kaiser Aluminum Sheet and Plate Book, Second Edition 195**
of aluminium have a modulus of elasticity of about
10,000,000 lb/in2 (700,000 kg/cm2) and steel about
29,000,000 lb/in2 (2,000,000 kg/cm2). Thus, some alu-
minium plate deflects farther under a given load; the
kinetic energy of impact (\mv2) is absorbed as work
(force x distance), as the plate deflects a greater distance
than it would if it were of steel. The mean stress in the
plate is thereby reduced substantially because of the
increased deflection of aluminium as compared to that of
steel.
The alloys recommended for building boats may be
called marine aluminium, and due to practical experience
and technological developments these alloys may con-
fidently be regarded as the most modern and useful of the
boat-building materials.
Tables 1 and 2 give data on such alloys that are
eminently suitable and satisfactory for boat hull con-
struction. Tables 3 and 4 give data on welding charac-
teristics for these alloys.
The typical specifications for aluminium boats given as
examples are intended as a guide only, they have been
compiled from various builders of successful boats. As
every design and construction problem cannot be
covered or foreseen it is recommended that engineering
personnel of a reputable prime aluminium producer be
consulted by naval architects and boat builders for
specific designs and for specific conditions before design-
ing the boats and before specifying and ordering the
material until experience has been gained in working
with this metal.
WEIGHT— STRENGTH
Aluminium weighs about one-third as much as steel,
and the aluminium marine alloys in tempers suitable for
ship construction have about the same yield and tensile
strengths as ordinary ship-building steel and about one-
third the weight.
Aluminium-magnesium-manganese alloy 5086-H34,
for example, has a typical tensile strength of 47,000
lb/in2 (3,300 kg/cm2), a yield strength of 37,000 lb/in2
(2,610 kg/cm2) and has excellent formability, weldability
and corrosion resistance.
The tensile strength of steel used in steel-boat con-
struction is in the range of 45,000 to 50,000 lb/in2
(3,170 to 3,520 kg/cm2) with a yield strength of about
35,000 lb/in2 (2,470 kg/cm2). When stretch-forming has
to be done, however, a hot rolled steel is used with a
yield of 24,000 to 28,000 lb/in2 (1,690 to 1,970 kg/cm2).
When it comes to strength to weight ratio alloy, 5,086 is
18,000 lb/in2 (1,270 kg/cm2) per unit weight versus 7,000
lb/in2 (493 kg/cm2) for steel and no more than 15,000
lb/in2 (1,060 kg/cm2) for the highest quality mahogany
(fig 1, tables 5 to 8).
[231]
WEIGHT WITH
EQUAL THICKNESS OX 20% 40% 60% 80% 100* 120% 140%
ALUMINUM
•^•H
^^
WEIGHT WITH
EQUAL STRENGTH
e
n. 2
D* 4<
)t 6(
ft 8
3% 10
0% 12
0% 14
OX
STEEI COMMON
ALUMINUM
M 1.1*1) 70MU
AifiAO 707411
AlClAD 701 4 T4
«06I It
M§*MJJ
••MS
•••••
•MM
=
••
•••
••B
=
••
" •
MW4MIA
Wl\Ml«
WEIGHT WITH
tQUAl STIFFNESS
G
ft 2(
n 4c
1% 6C
n. a
3% 10
0% 12
OX 14
01
t,.l
ALUMINUM
_
_
NOU (AMMO* WllOMt WIIMIQUAI tTMNCJTM IA»DUPONAN UlllUUU KNtl
tTtfNf.TM or MOM ni IDR ITIII AMDtnt OUAKANIICI> UIIIM*U$ »c»t T
I M *fl HNT WIICM1 IAIID »O* IOU
Fig I. Weight-strength in per cent— steel-aluminium
TABLE 5
Material comparisons
Material
Weight
ll>/f t3 kg/om3
Ult. tensile
lb/in2 kg/cm2
Tield tensile
2 2
lb/in kg/ cm
Ult. shear
lb/in2 kg/ cm2
Shear to grair
lb/in2 kg/cm2
Ult* bearing
> 2 2
; lb/in kg/cm
Mod. of
elasticity
lb/in2 kg/cm2
Douglas fir
33 0.43
11,700 825
8,100 570
1,140 80
910 64 *
7,420 522 +
1.92 0.135
White oak
46 0.59
13,900 980
7,900 567
1,890 133
1,410 99 *
7,040 496 +
1.62 0.114
Sitka spruce
2? 0.35
10,200 720
6,700 472
1,150 81
710 50 *
5,610 395 +
1.37 0.097
African
raaliogany
32 0.41
11,140 785
8,810 620
1,050 74
1,210 85 *
6,430 453 +
1.43 0.1005
Steal
490 6.30
60,000 4,230
33,000 2,320
45,000 3,170
60,000 4,230
29 2.04
Stainless steel
490 6.30
85,000 6,000
30,000 2,110
30,000 2,110
29 2.04
Wrought iron
480 6.17
48,000 3,380
26,000 1,830
28 1.97
A1-6061-T6
163 2.16
42,000 2,960
35,000 2,460
27,000 1,900
88,000 6,200
10 0.70
5052-H34
168 2.16
34,000 2,400
26,000 1,830
20,000 1,420
68,000 5,080
10.2 0.72
5154-H34
169 2.18
39,000 2,750
29,000 2,040
23,000 1,620
78,000 5,820
10.2 0.72
5056-B34
166 2.14
44,000 3,100
34,000 2,390
26,000 1,830
88,000 6,200
10.3 0.73
Svendur bronee
532 6.33
52,000 3,670
18,000 1,270
40,000 2,820
15 1.056
Uonel
550 7*08
75,000 5,300
35,000 2,460
26 1.83
QRP MIL P-
17549B Grade 3
100 1.28
18,000 1,270
10,000 705
21,000 1,460
1.2 0.085
RPL with grain
RPL across grain
32,000 2,250
21,000 l,4ttO
13,000 916
14,000 987
1.4 0.099
1.1 0.077
* Perpendicular to grain
+ Parallel to grain
[232]
TABLE 6x
Typical mechanical properties— wrought alloys
Alloy and
tecper
Tension '
ultimate Yield Elong-
atrength strength atlon
lb/in2 kg/cm2 lb/in2 kg/om2 % I/
Hardness
Brinell
Ho. 2/
Shear
Ultimate
strength
lb/in2 kg/om2
Bearing
Ultimate
strength ^/
lb/in* kg/om2
Fatigue
Endurance
limit £j
lb/in2 kg/om2
Modulus
Elasticity £/
lb/in2 kg/om
3003-H14
22,000 1,550 21,000 1,480 8
40
14,000 986
38,000 2,670
9,000 635
10.0 x 106 0.705 x 106
5050-0
21,000 1,480 8,000 563 24
36
15,000 1,060
39,000 2,750
12,000 845
10.0 x IO6 0.705 x 106
5050-H32
25,000 1,760 21,000 1,480 9
46
17,000 1,200
47,000 3,310
13,000 915
10.0 x IO6 0.705 x 106
5050-H34
28,000 1,970 24,000 1,690 8
53
18,000 1,270
52,000 3,660
13,000 915
10.0 x IO6 0.705 x 106
5050-B36
30,000 2,110 26,000 1,83O 7
58
19,000 1,340
56,000 3,950
14,000 985
10.0 x IO6 0.705 x 106
5052-0
28,000 1,970 13,000 920 25
47
18,000 1,270
61,000 4,300
16,000 1,130
10.2 x 106 0.719 x 106
5052-B32
33,000 2,320 28,000 1,970 12
60
20,000 1,410
71,000 5,000
17,000 1,200
10.0 x 106 0.705 x IO6
5052-H34
38,000 2,680 31,000 2,180 10
68
21,000 1,480
78,000 5,500
18,000 1,270
10.2 x IO6 0.719 x lO6
5052-H36
40,000 2,820 35,000 2,460 8
73
23,000 1,620
82,000 5,770
19,000 1,340
10,2 x IO6 0.719 x 106
5083-0
42,000 2,960 21,000 1,480 22
73
25,000 1,760
88,000 6,200
-
10.3 x 106 0.725 x IO6
5083-H32
49,000 3,450 39,000 2,740 10
-
•
_
-
10.3 x 106 0.725 x 106
5083-H34
53,000 3,730 43,000 3,030 8
.
-
-
-
10.3 x 106 0.725 x IO6
5083-H113
46,000 3,240 33,000 2,320 16
84
27,000 1,900
-
23,000 1,620
10.3 x IO6 0.725 x 106
5086-0
38,000 2,670 17,000 1,200 22
65
64,000 4ri>10
79,000 5,560
-
10.3 x IO6 0.725 x 106
continued ...
In 2 in (50.8 mO. 1/16 in (1.65 »») thiok specimen
1102.3 Ibs (500 leg) load. 0.394 in (10 mm; ball
Ultimate bearing strength with edge distance 2.0 times riret diameter
Based on 500,000,000 cycles of completely reversed stress using the R.R. Moore type of machine and specimen
Average of tension and compression moduli. Compresoion modulus about 2 percent greater than tension modulus
TABLE 6A (continued)
Typical mechanical properties — wrought alloys
1
Alloy and
temper
Tension
Ultimate Tield Elong-
strengtb strength ation
Ib/in2 kg/om2 lb/in2 kg/on2 % i/
Hardness
Brine 11
Ho. 2/
Shear
Ultimate
strength
lb/in2 kg/on2
Fatigue
Endurance
limit 4/
lb/in* kg/cm2
Modulus
Elasticity ^/
lb/in2 kg/om^
5086-E32
42,000 2,960 30,OOO 2,120 12
77
25,000 1,760
-
10.3 x IO6 0.725 x IO6
5086-H34
47,000 3,310 37,000 2,610 10
86
27,000 1,900
15,000* 1,060
10.3 x 10*' 0.725 x IO6
5086-H112
39,000 2,750 19,000 1,340 14
68
23,000 1,640
22,000 1,550
10.3 x IO6 0.72t> x IO6
5154-0
35,000 2,470 17,000 1,200 27
58
22,000 1,550
17,000 1,200
10.2 x IO6 0.719 x IO6
5154-W2
39,000 2,750 30,000 2,110 15
67
22,000 1,550
18,000 1,270
10.2 x IO6 0.719 x IO6
5154-B34
42,000 2,960 33,000 2,330 13
73
24,000 1,690
19,000 1,340
10.2 x IO6 0.719 x IO6
5154-B36
45,000 3,170 36,000 2,540 12
83
26,000 1,830
20,000 1,410
10.2 x 106 0.715* x IO6
5154-«112
35,000 2,460 17,000 1,200 25
63
-
17,000 1,200
10.2 x IO6 0.719 x IO6
5454-0
36,000 2,540 17,000 1,200 22
62
23,000 1,620
18,000 1,270
10.2 x 10^ 0.719 x 106
5454-H32
40,000 2,820 30,000 2,110 10
73
24,000 1,690
18,000 1,270
10.2 x 106 0.719 x IO6
5454-H34
44,000 3,100 35,000 2,470 10
81
26,000 1,830
18,000 1,270
10.2 x 106 0.719 x IO6
5454-H112
36,000 2,540 IB, 000 1,270 Iti
62
23,000 1,620
16,000 1,270
10.il x ID6 0.719 x IO6
5456-0
45,000 3,170 23,000 1,620 24
75
28,000 1,970
-
10.3 x 10^ 0.72!) x IO6
5456-*321
51,000 3,600 37,000 2,610 16
90
30,000 2.120
-
10.3 x IO6 0.71^ x 106
6061-T4
35,000 2,470 21,000 1,480 22
65
24,000 1,690
14,000 985
10.0 x IO6 0.705 x IO6
6061-96
45,000 3,170 40,000 2,820 12
95
30,000 2,120
14,000 985
10.0 x IO6 0.705 x 10^
* Krouse reverse bending fatigue test
y In 2 in (50.8 mm). 1/16 in (1.65 mm) thick specimen
£/ 1102.3 Ibs (500 kg) load* 0.394 in (10 mm) ball
4/ Based on 500,000,000 cycles of completely reversed stress using the R.B.
£/ Average of tension and compression moduli. Compression modulus about 2
[233]
Moore type of machine and specimen
percent greater than tension modulus
Mechi
TABLE 6n
nical property limits
Alloy and
tamper
Thickness I/
inches mm
in2 o»2
Strength minimum
Ultimata Yield
lb/in2 kg/cm2 lo/in2 kg/cm2
Elongation 2/ %
in 2 in (50.8 «B)
or 4 diam £/
6061-T4
All
All
26,000 1,830 16,000 1,130
16
6061-T6
All
All
38,000 2,670 35,000 2,460
10
6063-T4
0 -0.500 0 -13.2
All
17,OOO 1,200 10,000 705
12
6063-T6
0 -0.124 0 -O.26
0*123-1.000 0.30-2.54
All
All
30,000 2,110 25,000 1,760
30,000 2,110 25,OOO 1,760
8
10
5083-H112
All
0-32 0-265
40,000 2,820 24,000 1,69O
12
5086-E111
36,000 2,540 21,000 1,48O
21
5086-H112
All
All
35,000 2,460 18,000 1,27O
12
5154-H112
All
All
30,000 2,310 11,000 775
12
5454-H112
All
All
31,000 2,180 12,000 845
12
5456-B112
0-50 -132
0-32 0-265
42,000 2,960 19,000 1,340
12
I/ The thiokness of the cross section from uhich the tension teat specimen ia taken determines the
applicable mechanical properties. For material !-£ in or less in thickness, when not tested in full
section, the tension test specimen is taken from the centre of the section} for material over !•£ in
in thickness, the specimen is taken midway between the centre and the surface. Specimens are taken
parallel to the direction of extrusion
2/ For material of such dimensions that a standard test specimen cannot be taken, or for material thinner
than O.O62 in, the test for elongation is not required
Diam represents specimen diameter
TABLE 7
Recommended rivet diameters
Material
inches
thickness I/
mm
Rivet
inches
diameter
mm
0.
028
- 0
.036
0.
71 -
0.
91
1/16
1
.57
Over
0.
036
- 0
.048
0.
91 -
1.
22
3/32
2
.38
Over
0.
048
- 0
.064
le
22 -
1.
62
I/*
3
.14
Over
0.
064
- 0
.080
1.
62 -
2.
30
5/32
3
.96
Over
0.
080
- 0
.104
2.
30 -
2.
64
3/16
4
.71
Over
0.
104
- o
.128
2.
64 -
3.
25
1/4
6
.38
Over
0.
128
- 0
.188
3.
25 -
4.
77
5/16
8
.45
Over
0.
188
- 0
.20
4.
77 -
5.
08
3/8
9
.50
Over
0.
20
- 0
.25
5.
08 -
6.
35
7/16
11
.10
Over
0.
25
- 0
.30
6.
35 -
7.
62
1/2
12
.70
Over
0.
30
- 0
.35
7.
62 -
8.
88
9/16
14
.30
Over
0.
35
- 0
.40
8.
88 -
10.02
5/8
15
.90
Over
0.
40
- 0
.55
10.
02 -
14.10
3/4
19
.05
Over
0.
55
- 0.70
14.10 -
17.80
7/8
22
.20
i/ Thickness referred to is that of thinnest component
Hotes
The edge distance for riveting should normally be 2D (where D * rivet diameter) and never
less than 1-J-D. With these edge distances the hearing strength of aluminium alloys may be
taken as 1.8 times the tensile strength. The rivet pitch should not be less than 3D| for
water-tightness the maximum is 4D or lot (thickness of thinnest material in the joint),
whichever is the smaller*
[234]
TABLE 8
Wrought aluminium marine alloys
A. Approximate equivalents
USA
Al. Asa.
Australia
Austria
Canada
France
AFHOR
Germany
DIH
Italy
UNI
Japan
JIS
Switzerland
VSM
VK
BS
5052
AA57S
5052
1110(2%)
57S
A-G2
AlMg3
(3.3525)
PAG 2.5
A2-1
Al-3Mg
N~4
5154
C54S
PAG 3.5
A1-4H*
5456
6211
Al%54iln
3.3555
PA05+Un
Al-5Mf5+Mn
H5/6
5083
5083
D54S
(Al%+Mh)
3.3555
A2-7
N8
5086
6061
5086
AA65S
E45S
65S
(A-G4)
A-SC!?1
+Cr
(AlMgSiCu)
PASXO4?1
+Cr
A2-4
(Al-4Mff*-Mn)
AlSillg.Anti +Cu
oorodal +Cr
N5/6
E-20
The alloys given as equivalents in thic table might vary considerably in their chemical componition from one country
to another. Alloys not standardized in their respective countries are in parentheses*
B. Specification composition limits
Alloy
Si
Fe
Cu
Ibi
Mg
Cr
Zn
Ti
Other
Each Total
5052
.45Si+Fe
.10
.10
2.2-2.6
.15-. 35
.10
•05 .15
5154
Si+Fs
.45
.10
.10
3.1-3.9
.15-35
.20
.20
.05 .15
5456
Si+F«
.40
.10
.50-1.0
4.7-5.5
.05-. 20
.25
.20
.05 .15
5083
.40
.40
.10
.30-1.0
4.0-4.9
.05-. 25
.25
.15
.05 .15
3086
.40
.50
.10
.20-. 7
S.5-4.5
.05-. 25
.25
.15
.05 .15
6061
.40-.8
.7
,15-. 40
.15
.8-1.2
.15-* 35
.25
.15
.05 .15
CORROSION
It is necessary in marine applications to have good
resistance to corrosion as well as immunity from stress
corrosion.
Resistance to corrosion is determined experimentally
by the change in mechanical properties and by measuring
the depths of individual pits on test panels after pro-
longed periods of exposure. Such tests have shown that
most aluminium alloys in sea water will undergo localized
pitting to an average depth of 2 to 3 mm in one or two
years. With longer exposure, corrosion continues but the
rate of increase in depth diminishes with time. This has
been referred to as the "self-stopping" nature of corro-
sion on aluminium and is considered to be due to the
formation of protective corrosion products over the
small pits.
When aluminium is placed in contact with other metals
commonly used in marine applications, it may be attacked
by galvanic corrosion. This action is much like that of a
wet electric cell. Galvanic corrosion of aluminium is
more severe when aluminium is coupled to copper or
copper-bearing alloys— bronze, brass, monel— than when
it is coupled to steel, lead or nickel. Also, galvanic
corrosion of aluminium is more severe in a bimetallic
couple immersed in sea water than in a couple merely
exposed to marine atmosphere or immersed in fresh
water.
Generally, bimetallic couples are undesirable. Through
appropriate design, however, galvanic corrosion of alu-
minium can be prevented or minimized. The most com-
[235]
FILLET ui i£Ai iNCi
COMPOUND TOP ANO
HOT TOM TO PREVENT \
WATEK SFJPAGl
ALUMINUM PIA^F
!'K IMK NIOPRENE OR SIMILAR
NON ABSORBFNT MATERIAL
INSFRTFO 6FTWEEN THE STEEL
AND ALUMINUM PAYING sunrAr.FS
- i ' MINIMUM
^~
WtATHEfl SIDE
'111
I Poini bo*H I*.. I and aluminum faying turlo'.t with (wo
coo't ol unc chroma), pr.m.r b.tor. r.v.tmg
1 RIO.II homm.r.d down on it.*) nd« Fipot.d nv.l h.arfi
on aluminum plat, temtch bfuih.d. tl.on.d and paml.d
<*i»h i.v.rol coaU o» unc thfomal. prim.r
.1 R.comm.nd.d tiv.t mal.fialt
o 300 t.n.i Kami. it H..I
Fig 2. Details of aluminium to steel connections
M. v/ CAWILLO
Anode Placement
Modified 3 14 61
Anode Material - 99.99% Zin
(MIL-A-18001E)
Anodes touched to steel rudders with st««l
Studs welded to rudders und sterl nuts,
Anodes attached tu aluminum t>y weans of
6061 -T6 alloy studs we I Jed ty aluminum
and type 102 stainless ste«l nuts. Non-
hardftning, uluminum pigmented calking
compound used at beddinj material
between zinc anodes und aluminum.
Nate Optimum anode placement will
vary «*;•>' ^ull and service conditions.
®
__L Hull (Al) - 2 anodes
4"* 8"* 0.5"
One on each side, 2 ft out
from level and 1 5 ft from bow.
CD
Front Strut (Al) - 2 anodes
4" * 4" x 0.5"
One on outside surface of
_ each strut.
v£/
Shaft - One spherical anode on each
ihaft.
Rear Struts (Al) - 4 anodes
4" , 8' * 0.5'
One on outside surface and
one on inside surface ol each
»t of struts.
®
CD
Rudders (!>tl) - 4 anode*
5" x 10" * 0.5"
One on outside and Jne
inside surface of eac-h
^ rudder.
©
Transom (A I) - I anodes
4" K b" x 0.5
©
Fig 3. Anode position on aluminium boats
mon control of galvanic corrosion in bimetallic con-
nections is accomplished by separating the interfaces
between the aluminium and the dissimilar metal with
gaskets, washers, sleeves and bushings of insulating
materials, such as neoprene, alumalastic, fairprene,
presstite and micarta. These materials prevent the flow
of galvanic current necessary to sustain the attack on the
aluminium (fig 2).
Painting the surfaces of both metals with zinc chromate
paints will also inhibit galvanic corrosion in salt water.
Woods treated with copper-containing compounds
should not be used in contact with aluminium. Wet or
unseasoned wood may cause corrosion of aluminium if
in direct contact. Faying surfaces between wood and
aluminium should always be protected by painting the
wood with a zinc chromate paint, an aluminium pig-
mented paint or a bitumastic paint, and by applying
zinc chromate primer to the aluminium.
Some harbours and jetties have stray electrical cur-
rents in the water and in order that the aluminium will
be fully protected against electrolytic action, as there
could be bare spots on the hull bottom, zinc anodes are
placed on the bottom, shafts, struts or rudders so the
anodes will absorb the corrosive action instead of the
aluminium. See chart of anode placement on the m/v
Cabrillo (fig 3).
PAINTING
The principal reasons for painting aluminium boats are
(1) to add eye-appeal and (2) to prevent fouling of the
hull bottom. The inherently good corrosion resistance
of aluminium is attested by long-time exposure of un-
painted boats.
Painting aluminium, as with painting of other
materials, requires appropriate preparation of surfaces
prior to painting, the use of proper application methods
and acceptable paints. Surfaces must be clean to assure
good bonding. Solvent wash and either inhibited alkaline
cleaners or an alcoholic-phosphoric acid cleaner are
used. Further prcpaint treatment is desirable. This
consists of either a thin coat of zinc chromate wash
primer or the application of any one of the proprietary
chromate-phosphate chemical conversion coatings.
For decorative use, the same marine paints used on
other materials can be applied to aluminium. The manu-
facturer's directions should be followed.
Selection and application of antifouling paints on
aluminium requires special comment. Antifouling paints
containing mercury in any form, i.e. oxide, chloride or
mercuro-organic compounds, are not to be used on
aluminium under any circumstances because the mercury
will destroy the aluminium by forming an amalgam.
Copper-containing antifouling paints can be used, pro-
vided a sufficiently thick (usually 2 to 3 coats of a com-
patible red lead or zinc chromate anticorrosive paint)
layer of barrier paint is first applied to the aluminium.
If applied directly to aluminium, these copper-containing
antifouling paints may cause galvanic corrosion. A third
type of antifouling paint, containing organo-tin com-
pounds, has been recently introduced by a number of
leading marine paint manufacturers for use on alu-
minium, steel and non-metallic materials. Exhaustive
tests indicate that organo-tin-coutaining antifouling
[236]
paint systems are compatible with aluminium, even
without intermediate barrier paints. Many organo-tin
systems tested provided protection against marine fouling
for a period equivalent to a normal boat season. With
most organo-tin systems tested, the use of barrier paints
resulted in greater protection against marine fouling
under extreme fouling conditions than was provided by
the same system without the barrier paint, although one
vinyl system containing organo-tin was equally effective
with or without barrier paint. (Summerson et al., 1964.)
Restoration of the paint or repainting of an old boat
requires the cleaning and preparation methods described
previously. To remove old paint, organic paint removers
are recommended. Removers based on caustic (alkali)
are not acceptable. Light sand blasting can also be
used but care should be exercised to avoid overblasting,
resulting in removal of aluminium. In repair and main-
taining copper antifouling bottom paints, damaged
areas should be cleaned to bare metal, properly pre-
treated and painted with barrier paints before applying
the copper antifouling top coat. Organo-tin antifouling
paints can be applied directly over a wash primer or
chemical conversion coating.
Following is a step-by-step description of repainting
an aluminium boat:
Other pre-treatment, fillers and paint systems than
those recommended may be used, but since each com-
ponent of a system must be compatible with the total
system, the use of trade names has been employed in
order to be specific and to ensure the required com-
patibility. Experience has shown that "short cuts" or
deviations from the procedure can lead to unsatis-
factory results. Consequently, all steps must be followed
in order.
Removal of old paint
• Strip old paint with a commercial paint stripper
such as Turco 4260 B or equivalent. The stripper
should be applied and allowed to remain on hull
for approximately one hour or until paint film is
readily removable. The loosened paint can be
easily removed by steam cleaning using a neutral
detergent additive such as Turco Steamsall in the
boiler water.
• Use a disc or belt sander or rotary wire brush
(stainless steel) to remove any chemical coating
pre-treatments, such as Alodine, from hull area.
(As an alternative the entire hull may be sand-
blasted after paint removal to remove filler com-
pound, corrosion products, etc. Use clean sand
and avoid excessive blasting.)
• Seams, crevices and pitted regions, if present,
should be filled with suitable fairing compound
such as Devcon's plastic aluminium filler.
Prepaint treatment
Entire hull area should be washed with a phosphoric
acid-alcohol water reducible cleaner such as Turco WO 1
or equivalent. Flush thoroughly with fresh water. Allow
to dry thoroughly.
Application of paint
• As soon as hull is dry, it may be spray painted
with one thin coat of metal etching primer. The
film thickness should not exceed 0.5 mm, with
0,3 mm desirable.
• This can be followed almost immediately with one
coat of anticorrosive spray applied to a dry film
thickness of approximately 1.5 mm. (Follow
paint company's recommendations for thinning
of paint and for drying time.)
• Follow with two coats of metallic anticorrosive.
• Follow with two coats of antifouling paint to
produce a dry film thickness of 2 to 3 mm.
COSTS
Benford and Kossa (I960) stated as follows:
A steel tuna clipper, 1,200 tons displacement, power,
one 1,600 hp dicscl engine; to be built on the U.S.
west coast.
Structural hull invoiced weight .
Structural hull material cost
Structural hull man hours per ton of
steel
Structural hull man hours — total
Total material cost of vessel, including
machinery and outfit
Labour
Overheads (80% of labour)
Sub-total
Profit (10°;,)
Insurance (1%) ....
302 tons
£21,500
153
40,200
£119,000
£96,200
£77,000
£292,200
£29,200
£2,900
($60,400)
($333,000)
($269,600)
($215,700)
($818,300)
($81,800)
($8,200)
Total cost of steel vessel, does not in-
clude fishing gear ....
£324,300 ($908,300)
340.000 Ib
£54,500
£21,500
($153,000)
($60,500)
£33,(XX)
£500
($92,500)
($1,500)
If aluminium was used in lieu of steel for the hull and
in lieu of wood for the deckhouse, the cost may be as
follows :
Structural aluminium hull weight
Structural aluminium material cost
Structural hull cost in steel
Additional hull material cost
Additional deckhouse in aluminium
Total additional material cost . , £33,500 ($94,000)
About 56% additional hull and deckhouse material cost.
An example of a complete aluminium vessel
Estimating labour cost the same for the aluminium hull
as for the steel hull, the following are total costs for the
aluminium tuna clipper:
Total material cost of vessel, including
machinery and outfit— £119,000+
£33,500 ($333,0(X) (-$94,000)
Labour
Overheads (80% of labour)
£152,500 ($427,000)
£96,000 ($269,000)
£77,000 ($215,700)
Sub-total
Profit (10%) .
Insurance (1 %)
Total cost of aluminium vessel
Total cost of steel vessel .
Additional cost of aluminium vessel
£325,500 ($911,300)
£32,500 ($91,100)
£3,300 ($9,100)
£361,300 ($1,011,500)
£325,000 ($908,300)
£36,300 ($102,200)
About 11.5% additional cost of the complete tuna
clipper.
[237]
Shipyards may argue that it is more difficult to
fabricate aluminium than steel into a hull but ship-
yards accustomed to fabricating aluminium hulls will
testify that it is easier to handle the aluminium plates
as they weigh only half as much as steel plates. In
addition, the welding speed for aluminium is about
three times as fast as for steel, even though more pre-
welding preparation is needed in order to assure clean
surfaces.
The aluminium tuna clipper discussed here should
cost no more than about 10 per cent more than a similar
sized steel vessel.
Weight saving
There will be about a 152 tons weight saving in the
aluminium hull versus the steel hull. This weight saving
can be utilized in various ways: (1) to obtain more
speed with the same power; (2) to reduce the size of the
power plant and reduce fuel consumption and still
obtain the same speed as the steel vessel; (3) increase the
carrying capacity in addition to (1) or (2).
Saving on maintenance
The hull and deckhouses of an aluminium fishing vessel
may be left unpainted, thus affording a tremendous
saving on up-keep. The bottom may be painted with
antifouling if needed.
Even if it is decided to paint the aluminium vessel
there will still be a saving on maintenance over wood-
and steel-hulled vessels.
ALUMINIUM APPLICATIONS TO HULL
Typical specifications for 14 to 18 ft (4.3 to 5.5 m)
aluminium outboard fishing boats
(1) Welded construction
ALLOY
Hull
Sides:
Bottom :
Sides:
Bottom:
Sides:
5052-H32 to -H36
Same
5086-H32or-H34or-H112
Same
6061-T6
Bottom: Same
Transom
5052-H32 to -H36
5086-H32or-H34or-H112
Decking
5052-H32 to -H36
5086-H32or-H34or-H112
6061-T6
Framing— formed sheet
5050-H34 or -H36; 5052-H32 or -H34;
5086-H32or-H112
Castings— for strength
Sand and permanent mould: 355-T51 ;
356-T51;357
MATERIAL
THICKNESS
0.090 in (2.3 mm)
0.1 25 in (3.1 mm)
0.090 in (2.3 mm)
0.125 in (3.1 mm)
0.090 in (2.3 mm)
0.125 in (3.1 mm)
0.125 in (3.1 mm)
0.125 in (3.1 mm)
0.080 in (2 mm)
0.080 in (2 mm)
0.080 in (2 mm)
Castings— no special strength required
Sand and permanent mould: 43-F
Permanent mould: A214-F
Sand castings: F-214-F
(2) Riveted construction
ALLOY
Hull— Transom—Decking
505-H34 or -H36; 5052-H32 to -H36;
MATERIAL
THICKNESS
6061-T4 or T6
0.074 in (1.9 mm)
Seats— backed with floatation material
Same as hull
Framing— extruded shapes
6061-T4; 6062-T4 or -T6; 6063-T4
or-T6
Framing — formed sheet
5050-H36; 5052-H32 or -H34; 6061-T4
Castings— for strength
Sand and permanent mould: 355-T6;
356-T6; 357
Die castings: 218; 360; Almag-35
Castings — no particular strength required
Sand castings: 43-F; F214-F
Permanent mould: A 214-F
Die castings: 13; 43; 218; 360
0.040 in (1.1 mm)
Rivets
Sheet alloy
5050 and 5052
6061
For best results
6053-T61
6063-T6; 6061-T6
Typical specifications for 35 ft (15.8 m) fishing boat
welded aluminium construction
MATERIAL
ALLOY THICKNESS
Side plating
5086-H32 or -H 34 or -H 11 2 0. 1 88 to 0.250 in
(4.7 to 6.3 mm)
Bottom plating
5086-H32or-H34or-H112
Transom
5086-H32or-H34or-H112
Decking
5086-H32or-H34or-H112
Framing
Extrusions— 5086-H1 13 or 6061-T4
or-T6
Formed sheet— 5086-H32 or -HI 12
0.219 to 0.250 in
(5.6 to 6.3 mm)
0.219 to 0.250 in
(5.6 to 6.3 mm)
0.1 88 to 0.250 in
(4.7 to 6.3 mm)
[238]
Castings— for strength
Sand and permanent mould:
355-T51;356-T51;357
Castings — no special strength required
Sand and permanent mould : 43-F
Permanent mould: A214-F
Sand: F-214-F
Mechanical fastenings
Use 18-8 stainless-steel fasteners for hardware to deck
and hull, guardrails to hull, engine to bed, strut to hull,
under- water fittings to hull.
Welding castings to sheet and plate
With high silicon casting alloys such as 43, 355, 356 and
357, use 4043 filler wire when welding to thin sheet.
The 5000 series filler alloys may be used in welding to
wrought alloys in heavy sheet or plate gauges.
With 214 cast alloys, 5000 series filler alloys such as
5154, 5356, 5183 are recommended in preference to 4043.
Fuel tanks
Integral with hull— same as hull. May be clad with 7072
alloy on the fuel side if desired.
Separate tanks— Alclad 3003-H14 or Alclad 3004-H32.
Bare alloys may be protected with chemical conversion
coatings of the chromate variety such as: Alodine 1200,
Bonderite 721, Iridite 14-2, Turco 4178, Oakite Chromi-
coat.
Fresh-water tanks
Alclad 3003-H14 or Alclad 3004-H32.
Fuel piping and fittings
Alclad 6061-T61, Alclad 6063-T6, Alclad 3003-H18,
Alclad 3003.
If suitable aluminium alloy or stainless-steel valves
are not obtainable, use non-ferrous tubing and connect
to aluminium tanks by insulated flange or stainless-
steel nipples.
Fresh-water piping and fittings
Same as fuel piping and fittings.
Salt-water piping and fittings
Non-ferrous, stainless-steel or plastic is recommended.
Non-ferrous sea valves or fittings should be electrically
insulated from hull. Aluminium piping and fittings:
Alclad 6061-T6, Alclad 6063-T6, Alclad 3003-H18, may
be used provided suitable aluminium alloy or stainless-
steel or plastic valves and fittings are available
Some aluminium-hulled fishing boats in U.S.A.
(1) Gillnetters
Since 1959 some 81 aluminium gillnettcrs have been
built for salmon fishing in Alaskan waters. Eleven of these
were built by Marine Construction and Design Co.,
Seattle, Washington, and the balance by Matsumoto
Shipyard, Vancouver, B.C., Canada (fig 4, 5, 6 and 7).
Their particulars are as follows :
L— 32 ft (9.5 m)
B— 11 ft 6 in (3.5m)
T— 2 ft 5 in (.74 m)
Light-weight— 6,000 to 7,000 Ib (2,721 to 3,175 kg)
Fish-hold capacity— 27,000 Ib (12,254 kg) of fish, aft
cockpit capacity 8,000 Ib (3,628 kg) of fish
Fig 4. Gillnetters under construction
[239]
Fig 5. Gillnetter removed from jig
Fig 6. Interior of a 32-fi (10.6-m) gillnetter
7. Structural profile and main deck plan of a 32-ft (10.6-m) aluminium gillnetter
Speed— 15 knots
Main engine — 165 hp Gray marine gas engine, engine
rpm— 3,400
Propeller—20 in diam. x 17 in P (510 x 430 mm)
Reduction gear — 2 : 1 hydraulic
Shaft diam.— 1J in (38 mm)
Material — 5083 or 5086 aluminium, depending on ship-
yard; sides and bottom £ in (6.3 mm); bulkheads,
deck and floor plates •& in (4,7 mm); cabin J in
(3.2 mm). Extrusions 5083-H112 aluminium alloy.
(2) Seine skiffs
Dozens of these boats have been built of aluminium
since 1959. Many of these, built by Alfab Co., Edmonds,
Washington, have the following particulars :
L— 17 ft 6 in (5.3 m)
B— 8 ft 7 in (2.6 m)
Main engine — a variety of power plants was used
Fuel capacity— 95 gal (360 1)
Material — 5086 aluminium for hull plating with 6061
aluminium extrusions for framing
Others have dimensions of 18 ft 6 in x 8 ft 6 in
(5.6x2.6 m) and 18 ft 6 in x 9 ft 6 in (5.6x2.9 m),
some built by Kazulin-Cole Shipyards, Tacoma, Wash-
ington; and some by Marine Construction and Design
Co., Seattle, Washington.
(3) Purse seiner
The Josie J, an all-aluminium purse seiner, was built in
1960 by the Alfab Co., Edmonds, Washington, for Mr
S. A. Johnson, Seattle, for operations in Alaska and in
Puget Sound. Particulars are as follows:
L—57 ft (17.4m)
B— 18 ft 6 in (5.6m)
F2401
fr'ig 8. Aluminium menhaden seiners at work
T— 7 ft 6 in (2.3 m) loaded
Weight— 53,000 Ib (24,000 kg) without seine, skiffs and
gear
Speed — 24 knots in light condition, 18 knots loaded
A similar boat in steel would have weighed about 26,500
Ib (12,000 kg) more.
Material— 5086 aluminium, \ in (6.3 mm) for shell
plating; -ft in (4.7 mm) for bulkheads; decks are
i in (6.3 mm) with deckhouse and upper deck
•& in (4.7 mm).
(4) Purse seine boats for Menhaden fishing
In 1958, 78 of these boats were built by R.T.C. Boat
Company, Camden, New Jersey, for Fish Products
Company, Lewes, Delaware. Since that time some 150
such boats have been built, and operations range from
the Virginia Coast to the Gulf of Mexico (fig 8).
These boats, L— 36 ft (10.9 m), weigh 10,000 Ib
(4,536 kg) less than similar steel boats, a weight reduction
of some 63 per cent.
Material— 5052 aluminium, ft in (4.7 mm) for sides
and i in (6.3 mm) for bottom.
Rail cap Jkl I.'2>c3/16ir.(765
Stanchion* 3» I 1/2 n 3/16 in
Duck 3 loytrs 3/8m(IOmm) plywood r.ov«r§d OftCk l/4m(6?Smm) aluminium with decking
Wai»t__2Jgjjifi 3/8 in (10 mm) plywood
i 3/4 < 5 1/2 PQK t?«gmi 22 C-C
,'X ' 5/6in(l6mm) plywood gusi«ttf<')
et I i/4 »fi \/£ m(4!S»i40fi\rt)i ook 2? C -C rrom»t 3»l 1/2
P'onking 3 loyen 3/8 m( 10 mm) plywood^
Floor 2 l/ZKtm(635ilS3jnm) oak
_.FIoor 2 loytn 3/emMOmm) plywood
Fig 9. Midship sections of a draggcr
[241]
(5) Dragger
The midship section sketches of a proposed 51 ft (15 m)
dragger designed by naval architect Cyrus Hamlin,
Manset, Maine, U.S.A., should be of interest.
Mr Hamlin estimates that the aluminium hull would
cost 15 per cent to 20 per cent more than the wood hull,
but this may be less at a yard experienced in aluminium
construction. Offsetting the higher cost will be practically
no maintenance of the aluminium hull, more fish-hold
capacity and less weight. The hull and deck planking
would total H in (28.6 mm) in thickness versus J in
(6.3 mm) for aluminium and 5£ in (140 mm) deep
frames and deck beams in wood versus 3 in (67 mm) in
aluminium (fig 9).
The dragger is designed for either stern or side traw-
ling. The midship section of the aluminium hull shows
the ceiling, or inner fish-hold lining, to be of plywood
which, of course, could be of aluminium.
(6) Crayfishing boat
Built by Engineer and Marine Services, Fremantle,
Australia, in 1960 for crayfishing. Now owned and
operated by Australian Aluminium Company, Sydney
(fig 10, 11, 12, 13). Particulars:
Lr-64 ft (15.5m)
B— 1 7 ft 6 in (5.2m)
D— 8 ft (2.4 m)
T— 4 ft 6 in (1.4 m)
Power — one 230 hp Deutz engine with 2 : 1 reduction
gear
Speed— 11.3 knots
Range— 500 to 600 miles
Hull plating — ^ in (8 mm)
Deck plating — & in (4.7 mm)
Frame spacing — about 18 in (.457 m)
The owners report that this vessel has been very
successful and that there is a complete absence of either
pitting or corrosion. The hull is left unpainted.
(7) Sport fishing boats
The Lee Scott, a catamaran, built in 1958 by Forster
Shipyard, Terminal Island, California. Particulars:
L— 45 ft (13.7m).
B— 16 ft (4.9 m)
Power — two 100 hp Gray marine gas engines with 2 : 1
reduction gears
Speed— about 17.3 knots
Material — hull plating ^ in (5.5 mm) 5086 aluminium,
framing of 5083 and 5086 aluminium extrusions.
A 48 ft (14.6 m) aluminium charter sport fishing boat
was built in 1960 by Jansen Machine Works, Troutdale,
Oregon. Particulars:
L— 48 ft (14.6 m)
B— 12 ft 3 in (3.7 m)
T— 2 ft 8 in (.8 m)
Speed — 20 knots
Power — two 671 Gray marine diesels with 1.5 : 1
reduction gear
Material— sides and bottom £ in (6.3 mm) 5086-H34
aluminium plate; bulkheads, decks and cabin & in
(4 mm); framing 6061-T6 extrusions and bar stock.
Fig 10. Crayfishing boat at sea
Fig 11. Hull plating on crayfishing boat
Fig 72. Stern framing of crayfishing boat
Fig 13. Stern tube of crayfishing boat
[242]
Outboard rental boats used for sport fishing get severe
and heavy-duty use. The Manager, Mountain Harbour
Landing, Arkansas, has this to say: "We spent less than
£36 ($100) total maintenance on our 100 Duracraft
Pacemakers", 14 ft (4.3 m) aluminium outboard boats,
"in three years of rental use". That is an average of
2s 5d (33c) per boat per year. The Manager, Crystal
Springs Fishing Village, writes: "£7 ($20) was our total
maintenance cost for our fleet of 106 Duracraft Pace-
makers in their fifth season of use." Less than 3d (4c)
per year per boat!
Rental boats are usually left unpainted; the only
maintenance required, as a rule, is an occasional hosing
down with fresh water, inside and out. The particulars
are as follows:
L— 14 ft (4.3 m)
B— 4 ft 2 in (1.3 m), 4 ft 6 in (1.4 m), 5 ft 4 in (1.6 m)
D— 21 in (.5 m), 22 in (.6 m), 24 in (.7 m)
Weight— 135 Ib (61 kg), 183 Ib (83 kg), 198 Ib (90 kg)
Alloy and temper of hull material-— 6061 -T4
Thickness of hull— .063 in (1.6 mm)
Thickness of transom, deck, seats—
.080 in (2 mm) transom
.063 in (1.6 mm) seats
.063 in (1.6 mm) deck
Rivets— 6053-T61
Extrusions: side keels — 6061 -T5; spray rails, centre
keel, cap rain— 6061 -T42
Capacity— 745 Ib (338 kg)
Power — maximum 1 8 hp
Speed— 20 to 23 knots
ALUMINIUM FISHING BOAT APPLICATIONS
OTHER THAN HULL
Fish-hold linings and pen boards
Aluminium pen boards and fish-hold linings were first
installed in the United States in 1959 in the William J.
O'Brien, a 20-year-old, 122ft (37 m), Boston trawler.
Material for the extrusions was 6063-T6 and the fish-
hold lining was 5052 alloy (figs 14, 15, 16).
Similar wooden pen boards weigh 8 Ib (3.6 kg) dry
and up to 14^ Ib (6.6 kg) wet and have to be dried out
and painted several times a year. The aluminium extru-
sions weigh about 5 Ib (2.2 kg), wet or dry, never need
painting, are easy to clean and retain no odours. They
also increase the cooling efficiency of the ice and decrease
spoilage by allowing oxygen to reach fish stored against
Fig 15. Aluminium pen boards and fish hold lining
Aluminium food
.V8ln(IOmm> fir piy«ood
5052-H34 aluminium 091 mil 3 mm) thick
lowMt ttrokt aluminium oxidt imor
3 m( 76. S mm) no 24 aluminium *ood
>Cf>wt - ftOQl- T6
I 1/2 i 1 1/2 x I* m( ,581*381 16.6 mm)
aluminum
yiSjniSjnm] olymjnjum plot*
VBtBtlOmm) aluminium nvjt
Shtll (Hot*
Fig 14. Aluminium pen board installation
Fig 16. Pen partition details
the sides along the corrugations. The aluminium pen
boards last almost indefinitely whereas the wooden
boards have to be replaced frequently.
To re-line the fish hold with aluminium, the hold was
stripped down to its steel hull and treated with zinc
chromate. A 2 in (50 mm) layer of plastic foam was
used to replace the cork. The aluminium sheets were
overlapped and made watertight with an adhesive tape.
The sheets were secured with aluminium screws to the
underneath furrings.
Aluminium fish-hold linings and aluminium pen
boards have been in use in European fishing vessels
for about 17 years and have proved to be far more
sanitary than wood, and have withstood corrosion and
the most rigorous service conditions. Wood, on the
other hand, gets water-soaked and heavy, slime accumu-
lates in cracks and crevices which is impossible to
entirely remove and clean, so that bacteria in large
numbers populate the fish holds and contaminate the
fish catch.
Deckhouses
Numerous steel-hulled fishing vessels and fishing research
craft are built with aluminium deckhouses and pilot
houses to save top-side weight and for reducing main-
tenance (fig 17, 18, 19).
One such craft, a 165 ft (50.3 m) research vessel,
Albatross IV, designed by Potter, M'Arthur & Gilbert,
Inc., Boston, and built for the US Bureau of Com-
mercial Fisheries by Southern Shipbuilding Corp.,
[243]
46 m aluminium ,
5)n • l/4ln
'.765»65mm)
21/2 »l/4in(«4x«.5m
Stttl F.8. •
4*1/4 in (102 »65 mm) F B. alum in
»4in*5/l6m| \ vi/4m aluminium
(— 3/16 in Al.
(Smm)
3/l6m(5mm)AI !
/,--•* , -'•• j. a/16 »e in (Bxliimm) alum
{$*•""' 3/16 m' Bmm) aluminum pit
6*5/16 >n < ?03»Bmm) aui
Fig 17. Aluminium deck house
Aluminium bulkheads are also used in the main deck-
house cabin of the same sheet gauges and extrusion
sizes as in the bridge deckhouse and boat deckhouses.
A 99ft 11 in (30.5m) dragger, also designed by
Potter, M'Arthur & Gilbert, Inc. and built for the
Boston Fishing Co., Inc., used •& in (4.7 mm) 5052-H38
aluminium for deckhouse siding and roofing. Fish hold is
lined with f in (9.5 mm) fir plywood faced with .051 in
(1.2 mm) thick 5052-H34 aluminium sheet. Pen partitions
are of -ft- in (4.7 mm) 5052-H38 sheet with stiffeners of
5x£ in (127x6.3 mm) flat bar and lixljxj in
(38 x 38 x 6.3 mm) 6061-T6 extrusions.
Both of the above vessels were built to American
Bureau of Shipping rules and designed to Lloyds Class
Al Fishing Service Rules.
3/l6in(Snm)
Aluminium platt > Ikhia
10x2 BB6 xB B9in(234x73 5*226mm)
. Blym.|nmm C.IFP 21 to pR 2,7) IW«lnl32mm)
aluminium pip* itanchion_.
.aS.t.nifi-lmnjl.Alum.
Bi6x26in(204x204xf
_x ISmral alum, bro_cka.!.J
4x3x5/l6in(l02K765x8mm)
^
\4x3x3/8in(l02x76.5xlOmm)
Wil minium L
3/16 in (9 mm) Al.
ploti bulknaod
SiJium'brackalA
3/l6in(5mm)
alum, plata
Buikhtad
_*!5n>
3/16 In (5mm) aluminium
_pla1« buikhtad
2x1 1/2x1/4 in
(Slx38x65mm)
^Hwtrtad olum,JL „
Zxl 1/2 1 1/4 In
(9lx3B*B.9mm
^invtrUd alum
-
4x3x5/
oluminn
*~^-- " sL . i
1
i I2»5x30in(306x76j5x75mm)
|\fjan«« »mt_. . ... .1
Vl6:n(5mm)AI.
4x3xl/4in(l02 »765»63mm) *
JfLVtrttd t :
BtBx
brack*
-?. xl 1/2x1/4 ml5l » 3 8 » 65 mml.iwar. tf d
e»Bx.lOinU04x204x7.5)
.»
>
)
1
1/4 in dlo 11 wlra
r lift Itntt
JBRIDOE DCtK.
2 8 M7Zmm) aluminium
J.QAT DECK,
F/^. 18. Aluminium deck house
4 m ft3in«5/16m alu
U02»765»B mm)
Vfeln ttMl platt
IB mm]
8 in olum
2mm)
4 « 5/16 in tl«»l
. ]I02 xBmm)
LL
Fig 19 Detail "^" of deck house shown in fig 18
lell, Louisiana, used i in (6.3 mm) 5052-H34 alu-
iium plate for the top bridge deckhouse siding and
f and with 4 x 3 x J in (102 x 76 x 6.3 mm) aluminium
•usions for side stiffeners and 4 x 3 x J in (102 x 76 x
mm) roof framing. Railing up-rights are made of
in (31.7 mm) standard aluminium pipe as is the top
gitudinal rail with f in (19 mm) pipe for intermediate
igitudinal rails. Deckhouse superstructure, on top of
t deck, is made of .28 in (7 mm) aluminium plate for
is and has the roof deck made of .33 in (8.3 mm) and
in (7 mm) aluminium plate. Side stiffeners are
3 x •& in (102 x 76 x 8 mm) extru. Interior bulk-sions
ds are of -ft in (4.7 mm) sheet with 2xl£xJ in
x 30 x 6.3 mm) inverted angle extrusions. Railings on
bridge deck are the same as on the tophouse roof.
Aluminium deckhouses can be left unpainted in order
to save on maintenance, and in hot climates the alu-
minium deckhouses have a far cooler interior tempera-
ture due to the heat reflectivity characteristics of alu-
minium. Stability is enhanced by having less weight top-
side and carrying capacity is increased by the amount of
weight saving obtained through elimination of the steel
structures and substitution of aluminium. Over half of
the weight can be saved in such structures.
Other ship-board applications
Funnels, radar masts and signal masts are other items
made of aluminium. Although the weight is not great,
due to the high position in the vessels any weight saving
there is of consequence from the stability point of view.
Maintenance cost savings again are of importance in
these items.
The following is an example of maintenance and life
obtained from a firm of British trawler operators:
Steel funnel Aluminium funnel
Average life 10 years
£50 (*140)
Initial cost .
Cost of painting
(steel monthly,
aluminium semi-
annually).
Repairs over life .
Total cost 10 years
Total cost 20 years
Est. life 20 years
(after 5 years exp.)
£126 (S353)
£480
£50
($1,344)
($140)
£160
0
($448)
0
£580 ($1,624)
£1,160 ($3,248)
£386 ($801)
[244]
>oxes
Iverscn and Son, A.S., Norway, has in recent
produced over 30,000 fish boxes made of alu-
m which are used for boxing fish at sea (fig 20).
stored in this way, in a chilled hold, are reported
90 per cent suitable for filleting, and this figure,
;aid, is expected to reach 100 per cent. Such alu-
m boxing increases hygienic conditions of trans-
tion due to reduced presence of bacteria. In
on there is a reduction in maintenance costs as
nium boxes will last almost indefinitely. The boxes
Fig 20. Aluminium fish boxes
ade of Norwegian alloy number M 57S (similar to
o. 5052) with a thickness of .08 in (2 mm) at the
ind .07 in (1.75 mm) for sides and bottom. Their
L is 2 ft 11 in (810 mm), width 1 ft 64 in (480 mm),
; 6J to 7fff in (175 to 185 mm). The weight is
ximately 11 Ib (5 kg) with a volume of 15 imperial
>9 1). A wooden box would weigh approximately
22 Ib (8.2 to 10 kg). The bottom features a draining
i-ll holes in each side trough and 3 holes in each
o arranged that melted ice water and slime does not
to the box below when stored on top of each other.
SUMMARY
>mic factors arc the main reasons for using alu-
m in fishing boat construction. After five years of
:ing experience with aluminium gillnetters, a firm
iska, having a fleet of 41 such 32-ft boats, rcprc-
g an investment in excess of £215,000 ($600,000)
ttremely pleased with the performance of these
The representative of the firm has this to say:
"I would never put this amount of money into
wood, steel, or plastic. These boats are faster,
stronger and maintenance-free. True, like all
boats there are bumps and dents, but the ease
with which we can repair these is phenomenal.
We have an Aircomatic welder with argon gas
at the cannery and anything that develops we
repair quicker than is possible with wood, with
results as good as brand new. These boats have
given us excellent service with no deterioration
to the 5086 aluminium plate. Our maintenance
costs on them to date have been nil. Their greater
speed and carrying capacity increase their yield,
fishermen being equal. Personally, I feel these
make all other small fishing boats obsolete."
These boats are entirely unpainted. Sanitation in the
smooth aluminium fish holds, which are easy to clean, is
another obvious advantage.
There are now more than 80 aluminium gillnetters
fishing for salmon in Alaskan waters, and some 230
aluminium Menhaden purse seine boats, each 36 ft
(11 m), service motherships in the Gulf of Mexico and
off the US east coast, and there are numerous other
types of aluminium fishing boats giving excellent service.
Economic advantages
We have, then, the following economic advantages when
using an aluminium fishing boat: (1) reduced mainten-
ance, practically nil; (2) reduced fuel consumption per
mile of travel due to lower weight; a 65 ft (19.8'm)
aluminium boat, for instance, weighs about 54,000 Ib
(24,494 kg), 24,000 Ib (9,886 kg) less than the 78,000 Ib
(35,380 kg) of a steel boat with the same dimensions;
(3) reduced draft; (4) constant weight of the hull, no
water absorption as with a wooden hull ; (5) possibly better
manoeuvrability due to less hull weight; (6) no dry or wet
rot and no painting, caulking or puttying needed as with a
wooden hull and no rust as with a steel hull; (7) greater
speed with the same hp due to less weight; (8) better
sanitation, keeping the fish in good marketable condition.
An aluminium hull will last almost indefinitely. An
example of the lasting qualities of marine aluminium is
the 55 ft (16.8 m) aluminium yacht Diana II built in
England in 1931. In spite of severe service with the
British Navy during World War II with limited and
sometimes no maintenance this hull is still in excellent
condition having outlasted many power plant changes.
As long as proper alloys are used and care taken with bi-
metallic connections during construction there is no
reason why an aluminium fishing boat hull would not
last almost for ever. Such a hull requires no maintenance
whereas a wooden hull needs constant attention, and a
steel hull needs chipping and scraping off the rust and
painting and eventually there is no hull left. Teredo
attack, especially in southern water, is a constant threat
to a wooden hull as are dry and wet rot.
When considering smaller fishing boats used in con-
junction with larger vessels the purse seine skiffs may be
mentioned. Heavy, waterlogged wooden seine skiffs are
difficult to take off and on the seiners, and nets and
leads can get snagged on the wooden framing members
that may be splintered. The lightweight aluminium seine
skiffs, on the other hand, are easy to handle and their
smooth and clean interior is a real asset when handling
the nets. As the aluminium skiffs never need painting the
upkeep is negligible and they will last almost indefinitely.
Their light weight provides more speed with equal
power and could make them more manoeuvrable, cuts
down on fuel consumption, and if more speed is not
desired a smaller power plant will provide a speed equal
to the heavier wooden hulls. Also, there are no leaks in a
welded aluminium hull, whereas a wooden hull develops
leaks after having been out of the water for a time due to
shrinkage of the hull planks, and time is required for
swelling; also, puttying and caulking is often required.
The aluminium hull may be launched at any time without
fear of leaks and without any work on the hull.
[245]
3/I6 inOmm) aluminium
4ftl'4m (K)2i68mm) FB. olummium
»n • l/4in aliMiMwm F8 '
(/6b»«3mm)
21/2 Bl/4ui(64»6.5mm)
Stttl F.B. - .
J« to • 4 in i9/l6nl v I/4 m alumi
(l50»lOZ»8mm)i. ! I '6 5 mm)
— MS w «.
(Smm)
3»l/4tn Al F- B
/r- * T" L j- 5/l6 * 6 <nl6»l53mm) alu
Fig 17. Aluminium deck house
Aluminium bulkheads are also used in the main deck-
house cabin of the same sheet gauges and extrusion
sizes as in the bridge deckhouse and boat deckhouses.
A 99ft 11 in (30.5m) dragger, also designed by
Potter, M'Arthur & Gilbert, Inc. and built for the
Boston Fishing Co., Inc., used •&• in (4.7 mm) 5052-H38
aluminium for deckhouse siding and roofing. Fish hold is
lined with | in (9.5 mm) fir plywood faced with .051 in
(1.2 mm) thick 5052-H34 aluminium sheet. Pen partitions
are of -& in (4.7 mm) 5052-H38 sheet with stiffeners of
5x£ in (127x6.3 mm) flat bar and lixl£x± in
(38 x 38 x 6.3 mm) 6061-T6 extrusions.
Both of the above vessels were built to American
Bureau of Shipping rules and designed to Lloyds Class
Al Fishing Service Rules.
IO»2B86iB89in(254n735»2Z6mm)
. 9L«mlnium L. iffl. 21 U PR Ml . 1 »M In ( 32 mm )
aluminium pip* stanchion ^ ,
.2 8 IniTjBjm) afamtntum J3 inl8 4mm) Alyn^
X\
S5"
\4»3«3/8in{l02»r6.5»IOmm) 1 J f
\oluminium L \t |
25m(6 5mm)
e*8iiZftin{204ii204*r '
aluminium fcrw
kM
• 69 mm) alum, bra cfctt ]
3/16 in (5 mm) Al.
plati bulkhtod
3/l6in(5mm)
alum plata
^bulhhtad
3/16 In (Smm) aluminium
^plat* bulkhtod
2*1 l/2»l/4in
2il l/2>IMh
4 »3 »5/l6in(IOZ »76a«8mm)
(91 i38K6.fi mm
i
aluminium I
J»a*«-»±—
. mv.ru d alum
>...
•
22in(ft5mm) , .S0in(7.5mm) , -
-• - — I __f / ( '
.30,n,75mm),*,.A
L".-M»..»..T«|
^[of« buTkhtad,
jfivtrttd U \ %
brgckft J
!
_2 »l .1/2 Kl/4jni5I.K36»65mm)'n^rUd t.
. Tpj> rail lin aluminium plp«
1/4 in dia ii wlra
JBffiOE. DECK.
2 8 In ( 7 2 mm) aluminium .
Fig. 18. Aluminium deck house
4m*3,ni5/l6in olu
(I02iir65iie mm)
5/ttin BtMl plot*
t Aluminium nvttt 101
' b* made up on ntopri
4 . 5/16 m ilial F.8.
Fig 19 Detail *VT of deck house shown in fig 18
Slidell, Louisiana, used i in (6.3 mm) 5052-H34 alu-
minium plate for the top bridge deckhouse siding and
roof and with 4 x 3 x i in (102 x 76 x 6.3 mm) aluminium
extrusions for side stiffeners and 4 x 3 x f in (102 x 76 x
9.5 mm) roof framing. Railing up-rights are made of
li in (31.7 mm) standard aluminium pipe as is the top
longitudinal rail with J in (19 mm) pipe for intermediate
longitudinal rails. Deckhouse superstructure, on top of
boat deck, is made of .28 in (7 mm) aluminium plate for
sides and has the roof deck made of .33 in (8.3 mm) and
.28 in (7 mm) aluminium plate. Side stiffeners are
4 x 3 x ^ in (102 x 76 x 8 mm) extru. Interior bulk-sions
heads are of •& in (4.7 mm) sheet with 2x l£x J in
(50 x 30 x 6.3 mm) inverted angle extrusions. Railings on
the bridge deck are the same as on the tophouse roof.
Aluminium deckhouses can be left unpainted in order
to save on maintenance, and in hot climates the alu-
minium deckhouses have a far cooler interior tempera-
ture due to the heat reflectivity characteristics of alu-
minium. Stability is enhanced by having less weight top-
side and carrying capacity is increased by the amount of
weight saving obtained through elimination of the steel
structures and substitution of aluminium. Over half of
the weight can be saved in such structures.
Other ship-board applications
Funnels, radar masts and signal masts are other items
made of aluminium. Although the weight is not great,
due to the high position in the vessels any weight saving
there is of consequence from the stability point of view.
Maintenance cost savings again are of importance in
these items.
The following is an example of maintenance and life
obtained from a firm of British trawler operators:
Aluminium funnel
Est. life 20 years
(after 5 years exp.)
£126 ($353)
Steelfunnel
Average life 10 years
Initial cost .
Cost of painting
(steel monthly,
aluminium semi-
annually).
Repairs over life .
Total cost 10 years
Total cost 20 years
£50 ($140)
£480
£50
($1,344)
($140)
£160
0
($448)
0
£580 ($1,624)
£1,160 ($3,248)
£386 ($801)
[244]
Fish boxes
Bernt Iversen and Son, A.S., Norway, has in recent
years produced over 30,000 fish boxes made of alu-
minium which are used for boxing fish at sea (fig 20).
Fish stored in this way, in a chilled hold, are reported
to be 90 per cent suitable for filleting, and this figure,
it is said, is expected to reach JOO per cent. Such alu-
minium boxing increases hygienic conditions of trans-
portation due to reduced presence of bacteria. In
addition there is a reduction in maintenance costs as
aluminium boxes will last almost indefinitely. The boxes
Fig 20. Aluminium fish boxes
are made of Norwegian alloy number M 57S (similar to
US No. 5052) with a thickness of .08 in (2 mm) at the
ends and .07 in (1.75 mm) for sides and bottom. Their
length is 2 ft 7J in (810 mm), width 1 ft 6J in (480 mm),
height 6J to 7j5c in (175 to 185 mm). The weight is
approximately 11 Ib (5 kg) with a volume of 15 imperial
gal (69 1). A wooden box would weigh approximately
18 to 22 Ib (8,2 to 10 kg). The bottom features a draining
system — 1 1 holes in each side trough and 3 holes in each
end, so arranged that melted ice water and slime does not
run into the box below when stored on top of each other.
SUMMARY
Economic factors are the main reasons for using alu-
minium in fishing boat construction. After five years of
operating experience with aluminium gillnetters, a firm
in Alaska, having a fleet of 41 such 32-ft boats, repre-
senting an investment in excess of £215,000 ($600,000)
are extremely pleased with the performance of these
boats. The representative of the firm has this to say:
• "1 would never put this amount of money into
wood, steel, or plastic. These boats are faster,
stronger and maintenance-free. True, like all
boats there are bumps and dents, but the ease
with which we can repair these is phenomenal.
We have an Aircomatic welder with argon gas
at the cannery and anything that develops we
repair quicker than is possible with wood, with
results as good as brand new. These boats have
given us excellent service with no deterioration
to the 5086 aluminium plate. Our maintenance
costs on them to date have been nil. Their greater
speed and carrying capacity increase their yield,
fishermen being equal. Personally, I feel these
make all other small fishing boats obsolete."
These boats are entirely unpainted. Sanitation in the
smooth aluminium fish holds, which are easy to clean, is
another obvious advantage.
There are now more than 80 aluminium gillnetters
fishing for salmon in Alaskan waters, and some 230
aluminium Menhaden purse seine boats, each 36 ft
(1 1 m), service motherships in the Gulf of Mexico and
off the US east coast, and there are numerous other
types of aluminium fishing boats giving excellent service.
Economic advantages
We have, then, the following economic advantages when
using an aluminium fishing boat: (1) reduced mainten-
ance, practically nil; (2) reduced fuel consumption per
mile of travel due to lower weight; a 65 ft (19.8'm)
aluminium boat, for instance, weighs about 54,000 Ib
(24,494 kg), 24,000 Ib (9,886 kg) less than the 78,000 Ib
(35,380 kg) of a steel boat with the same dimensions;
(3) reduced draft; (4) constant weight of the hull, no
water absorption as with a wooden hull ; (5) possibly better
manoeuvrability due to less hull weight; (6) no dry or wet
rot and no painting, caulking or puttying needed as with a
wooden hull and no rust as with a steel hull; (7) greater
speed with the same hp due to less weight; (8) better
sanitation, keeping the fish in good marketable condition.
An aluminium hull will last almost indefinitely. An
example of the lasting qualities of marine aluminium is
the 55 ft (16.8 m) aluminium yacht Diana II built in
England in 1931. In spite of severe service with the
British Navy during World War 11 with limited and
sometimes no maintenance this hull is still in excellent
condition having outlasted many power plant changes.
As long as proper alloys are used and care taken with bi-
metallic connections during construction there is no
reason why an aluminium fishing boat hull would not
last almost for ever. Such a hull requires no maintenance
whereas a wooden hull needs constant attention, and a
steel hull needs chipping and scraping off the rust and
painting and eventually there is no hull left. Teredo
attack, especially in southern water, is a constant threat
to a wooden hull as are dry and wet rot.
When considering smaller fishing boats used in con-
junction with larger vessels the purse seine skiffs may be
mentioned. Heavy, waterlogged wooden seine skiffs are
difficult to take off and on the seiners, and nets and
leads can get snagged on the wooden framing members
that may be splintered. The lightweight aluminium seine
skiffs, on the other hand, are easy to handle and their
smooth and clean interior is a real asset when handling
the nets. As the aluminium skiffs never need painting the
upkeep is negligible and they will last almost indefinitely.
Their light weight provides more speed with equal
power and could make them more manoeuvrable, cuts
down on fuel consumption, and if more speed is not
desired a smaller power plant will provide a speed equal
to the heavier wooden hulls. Also, there are no leaks in a
welded aluminium hull, whereas a wooden hull develops
leaks after having been out of the water for a time due to
shrinkage of the hull planks, and time is required for
swelling; also, puttying and caulking is often required.
The aluminium hull may be launched at any time without
fear of leaks and without any work on the hull.
[245]
All-Plastic Fishing Vessels
by Mitsuo Takehana
Bateaux de ptche en plastiques renforces
La communication 6tudie, des points de vue de la technique et du
cout, Inapplicability des plastiques renforces de fibres de verre a la
construction des coques de bateaux de peche. II semble que les
chantiers japonais de construction de bateaux de pgche puissent
offrir un important d£bouch£ a ce proc£d£, & condition que soient
effectues les travaux de recherche necessaires. L'auteur d6crit les
types de bateaux de pdche pouvant etre construits en plastiques
renforces.
L'6tude fournit egalement des donnees sur Techantillonnage et le
cout des bateaux japonais. II est signal 6 que le prix de revient des
batiments en plastiques armes pourrait dire ramend £ 120 pour 100
seulement de celui des bateaux en bois. La communication s'attache
aux avantages que presentent les navires en plastiques renforces,
etant donn£ que, par rapport au mode de construction classique,
cette technique permet une 6norme reduction du poids de la coque.
Embarcaciones pesqueras hechas enteraraente de plastico
El trabajo describe la aplicabilidad de los plasticos reforzados con
fibre de vidrio en la construccibn del casco de las embarcaciones
pesqueras desde el punto de vista de la tecnologia y el costo. Al
parecer, existe un amplio mercado potencial en las industrias de
construcci6n de barcos pesqueros del Jap6n, a condici6n de que se
realicen investigaciones adecuadas. Se indican ejemplos de los
tipos de embarcaciones pesqueras que se pueden construir con
dichos plasticos.
Se indican tambien datos sobre escantillones y costos en cl
Jap6n. Se hace notar que el costo de las embarcaciones de plastico
reforzado con fibra de vidrio podria reducirse 1,2 vcces en relation
con el costo de las embarcaciones de madera. Este trabajo trata
tambien de las ventajas del disefio de las embarcaciones de plastico
reforzado con fibra de vidrio debido a la enorme reducci6n del
peso del casco en comparacibn con la construcci6n corriente,
FIBREGLASS Reinforced Plastic (FRP) is no
longer new in many countries as a material for
naval or pleasure craft, and the demand for it is
ever increasing. FRP is now unanimously recognized as
the best plastic material that can be suitably used at sea.
The writer intends to discuss whether FRP can play any
helpful role in the modernization of about 350,000
Japanese small wooden vessels. Japan is now suffering a
Fig L 5 GTpole and line boat
remarkable rise in construction costs of wooden boats,
aggravated by the shortage of good quality timber and
lack of skilled shipwrights. This has resulted in using
steel for small boats of even less than 5 GT. The change
in material demands changes in hull shape, which also
changes vessel performance. FRP could, therefore, well
replace wood as the construction material for smaller
fishing craft if its advantageous properties are fully
utilized, namely, light weight, good durability, thermal
qualities, decrease in vibration and corrosion. FRP should
be further investigated for workability, cost and other
factors.
FRP was first used about four years ago in Japanese
fishing boat construction. Today the material is seen in
about 300 laver-picking and 100 pearl-working boats,
several pleasure fishing boats and fishing patrol boats of
32 to 43 ft (10 to 13 m). A tuna fishing vessel of 54 ft
(16.5 m) length overall has recently been constructed.
This is the largest vessel in use to be constructed of FRP,
although several of a larger size are under trial.
The main obstacles to the full utilization of FRP for
fishing boats are :
• Uncertainty about strength and durability among
would-be users
• Only recently have the proper procedures been
established with regard to ship form shape, method
of construction and testing
• Economy in applying the material has not been
analysed enough
• Technical training is needed for those going into
the FRP business, as well as promotion of the
material among boat owners.
Fig 2. 20 GTpole and line boat
[246]
Japanese technologists have done five years research on
applying FRP to high-speed boats from 8 to 39 ft (2.5 to
12 m). Another study is under way on the application of
FRP to fittings of large ships. The writer is planning a
third project to remove the above-mentioned bottlenecks
by promoting FRP applications in co-operation with
governmental organizations, research institutes and
manufacturers.
SPECIAL FEATURES OF SMALL BOATS
Table 1 shows the number of sea-going motor fishing
vessels in Japan at the end of 1963. In 1964, steel boats
and woooden boats increased by 522 and 3,339 respec-
Fig 3. 3 GT trawler
tively. The increase of the latter includes those converted
from non-powered boats. In terms of gross tonnage,
however, the steel boat has increased by approximately
63,600 GT, while wooden vessels have decreased by about
7,000 GT. This indicates that the average size of wooden
vessels has decreased. Mechanization of non-powered
vessels is indicated by the 2.1 per cent increase in the
number of powered vessels below 5 GT. Preference for
larger engines is seen in the increase of average engine
output ; for example, from 39 to 42 hp for the vessels
between 5 to 19 GT. Japanese small fishing vessels below
50 GT can be classified into a few groups based on their
economy.
Vessels under 1 GT are not engaged in active commer-
cial fishing. Many are owned by part-time retired fisher-
TABLE 1 : Powered sea-going fishing vessels (as at the end of 1963)
Type of
construction
or size of
No. of
vessels
GT
hp
vessel
Steel .
Wood .
3,299
189,216
1,121,258.56
788,263.74
1,906,280
3,108,150
Total .
192,515
1,909,522.30
5,014,430
Less than 5 GT
5—9 GT
10—19 GT .
20 GT and over
167,684
8,041
7,129
9,661
300,174.93
58,755.39
108,024.79
1,442,567.19
1,315,237
227,078
406,310
3,065,805
Note : Number of other fishing vessels which are not listed above are :
Non-tidal water, powered 3,600
Non-powered 202,820
Among these, 175,436 vessels are less than one GT
men. Vessels of 3 to 5 GT have high productivity and are
the core of the coastal fishery. Their main methods are
small-scale trawling and pole-fishing. The vessels of 5 to
10 GT are not necessarily economical, depending on the
operating waters. Some owners have replaced their boats
with vessels of 20 to 30 GT. The vessels of 40 to 50 GT
are highly capitalized fishing operations with larger crews.
Fig 4. 5 GT trawler
This paper will refer only to the group below 30 GT,
with emphasis on those from 3 to 5 GT, including non-
powered vessels such as cultivation boats and tenders.
Fig 1 to 20 provide a comparison of wooden and FRP
boats, ranging from a 5-GT pole fishing boat to the larg-
est plastic tuna vessel in Japan. In 1960 the Japanese
Fisheries Agency prepared drawings of 16 kinds of small
prototype wooden fishing boats, with a view to curtailing
the amount of materials and the number of processes.
Fig 1 1 and 12 are some of these drawings. FRP construc-
tion requires standardization. In the first place, various
local types were selected and those which were popular
over a large area were chosen. This selection was consid-
erably difficult as it involved minimizing traditional
differences in various areas. Timing was another problem
as the right advice must be given at the right moment if
fishermen are to accept such modification of their vessels.
NEED FOR FRP CONSTRUCTION
Table 2 shows the consumption of wood and price
trends in Japan. As is shown, the domestic supply has
increased only 22 per cent during the last eight years,
while imported wood increased 7.5 times. The price of
timber in 1 963 was 2.2 times the price of general commod-
ities. During the period, the quality of wood for boat
construction has declined, resulting in quicker hull
TABLE 2: Consumption and price of timber in Japan
Consumption
Price Index
Year
Domestic Product
Import
General
Commodities
Timber
1955
38,256
2,054
343.0
509.9
1957
41,667
2,893
368.8
614.8
1959
42,827
5,705
348.3
604.1
1961
49,333
9,635
355.7
764.0
1963
46,882
15,300
356.0
786.9
Note: Product and import unit is 35,315 ft3 (1,000 m3)
Unit of price index is average of 1934 — 1936
[247]
Fig 5. 2 GT trawler
TABLE 3 : Annual construction of wooden vessels
Year
1955
1957
1959
1961
1963
Vessel more than 20 T
or more than 50 ft (15 m)
60
100
63
64
35
Small vessel
13
14
14
13
15
Total
73
114
77
77
50
Note: l.Unitisl.OOOGT
2. Information is obtained from the Japanese Transportation
Ministry
deterioration. At the same time, construction has become
inferior as there are fewer apprentice shipwrights. This
trend is seen especially in vessels below 5 GT which are
built in small village shipyards. In table 3 the number of
small wooden vessels remains almost unchanged because
they cannot be built in steel. Table 4 shows the trend of
the standard cost of a fishing boat hull. The hull construc-
tion cost of wooden fishing boats has increased by as
much as 60 per cent; the cost of steel construction has
Fig 6. Shell-fish and laver boats
remained almost unchanged. This is due to rising wood
costs, shortage of skilled shipwrights and no improve-
ments in construction of wooden vessels. On the other
hand, building techniques for steel vessels have consider-
ably improved so that the rise of both material and labour
costs are almost cancelled.
To cope with this situation, a few shipyards, which
formerly built in wood, have been consolidated into one
enterprise to strengthen their facilities and build steel
vessels. Now 20 GT auxiliary boats for purse seining and
5 GT fish carriers are built in steel. The construction of
these small steel boats is, however, outside of the existing
ship-building standards of construction work, and
establishment of standard regulations is needed.
Meanwhile, traditional small fishing boats are built of
wood in small-scale shipyards which cannot afford addi-
tional equipment to start building steel boats. Under the
circumstances, it seems advantageous for them to learn
FRP construction techniques as the equipment needed is
less expensive than for steel vessels.
TABLE 4: Cost of fishing vessels
Cost/GT in £ (t)
Quality
5 GT
10
GT
20 GT
1957
1963
1957
1963
1957
1963
Non-powered wooden vessels
Excellent
77
108
(216)
(302)
(after 1 2 years,
Good
55
88
residual value 5%)
(154)
(246)
Normal
45
64
(126)
(179)
Powered wooden vessels
Good
84
128
94
144
104
164
less than 20 GT (10 years,
Normal
(235)
65
(358)
100
(263)
70
(403)
115
(291)
76
(459)
124
7%)
(182)
(280)
(196)
(322)
(213)
(347)
in £ ($)
Quality
20 GT
30 GT
50 GT
100 GT
1963
1963
1963
1957
1963
Steel vessels
Excellent
380
340
312
280
190
(15 years, 10%)
Good
1065
320
(952)
295
(873)
270
(984)
250
(812)
250
(895)
(825)
(755)
(700)
(700)
Normal
280
250
230
220
220
(784)
(700)
(644)
(616)
(616)
Note: Valuation unit is £/GT ($/GT)
From Prof. Takagi: Fishing Boat Society of Japan, 135 (Fcb 1965)
[248]
Fig 7. Laver btwt
PROBLEMS IN FRP CONSTRUCTION
The problems involved in the construction of small FRP
fishing boats are:
• FRP construction does not require any joints,
making it light and durable, while conventional
wooden boats require joint strength, resulting in
heavy structure. If FRP vessels are built on wooden
boat lines, they tend to float excessively and lose
balance
• As seen in fig 1 to 20, there are various hull
shapes according to local requirements. It is neces-
sary to standardize them into a few shapes taking
the preceding item into account. Difficulties in
building different designs of FRP vessels can be
overcome by applying prefabrication techniques.
This is especially true for Japanese traditional type
pole-fishing vessels and trawlers. However, there is
a huge number of small vessels which do not re-
quire special designs for local conditions. Examples
are, laver-picking boats, pearl-cultivation boats,
tenders and launches, which can be built easily
by means of the female mould method. Large
vessels over 39.4 ft (12 m) should be built by means
of the male mould method
% Since shelters are often not large enough to accom-
modate many small vessels, they bump, and
fenders are necessary
% Small vessels are often accommodated in shelters
where there is no water at ebb tide. Many small
vessels are beach-landed. Therefore, a special
plastic cover on the bottom is necessary or easily
replaceable false keels must be added
> FRP-built boats have significant hull deflection
adversely affecting the engine and shafting. The
engine bed should be wooden or wood reinforced.
When reinforced by wood, attention should be
paid to the different durabilities of wood and
plastic
Fit! tf. Lavcr boat in FRP
EXAMPLES
Laver* and pearl boats
For open boats such as laver-and-pearl cultivation boats,
the female mould method is used, since about 100 vessels
are built from one mould. It has been concluded that
three types of laver-collecting boats can be FRP-built in
Japan; the Ariakc type (fig 8), Funabashi type (fig 10)
and Toyohashi type. On the other hand, modification of
existing design is needed for the pearl-boats so they can
also be used as tenders. The new designs are shown in fig
13 and 14. This boat develops about 12.5 knots with a
10-hp outboard engine and two men on board. The
dimensions arc L x B x D = 16.1 x 5.27 x 2.23 ft (4.92 x 1.6
xO.68 m), with hull weight 190 kg. Central deflection is
0.2 in (5 mm) under the bending moment of , with the
maximum stress rated at 355 lb/in2 (0.25 kg/mm2), when
the distance of two hanging hooks is 1 1.44 ft (3.48 m).
The price of this is £140 (US$390) for the hull and £130
(US$360) for the engine, totalling £270 (US$750). The
weight of the hull is only 190 kg in comparison with 800
kg for a wooden boat of the same size. The heavier weight
* Note: lavcr is a kind of seaweed.
Fig 9. Laver boat in FRP
[249]
of the wooden boat necessitates an 18-hp engine to make
the same speed. A wooden boat of the same size costs £90
(US$250) for the hull plus £210 (US$585) for an 18-hp
engine, totalling £300 (US $ 835).
Japanese traditional boat
The prefabrication method is applied to this type of boat
without the mould. Therefore the construction procedure
is the same as for wooden boats. Plates are made by
attaching FRP on one side of a vinyl chloride foam plate.
The plate is used as a hull plate with the FRP side out.
The outside joints are sealed with FRP and the inside is
coated with FRP to the required thickness. This process
is difficult for double curvatured surfaces, but the Japan-
ese-type boats have no such structure. Fig 15 and 16
show an experimental boat built by this method. Various
tests, such as rolling, strength, vibration and speed, had
been carried out with this boat. The dimensions are
LxBxD* 18.2x4.25xl.97 ft (5.54 x 1.29x0.60 m).
The engine is 3-hp diesel and the engine bed is made of
zelkova. The deck beams and deck plates are also wood.
The performance data are :
Maximum speed
GM light condition
Rolling period
Extinction coefficient
Radius of gyration
5.75 knots
0.83 ft (0.27 m)
1.64 sec
0.058
1.141 ft (0.47m)
Fig JO. Laver boat
These data indicate that deck comfort should not
differ from the same size wooden boats. This prefabrica-
tion method has been applied to several sport fishing boats
of 33 ft (10 m) to 40 ft (12 m) (fig 17) in small local
wooden shipbuilders who learned the FRP technique.
Japanese traditional sport fishing boats
Sport fishing boats built of FRP sandwich system with
vinyl chloride foam plates in the middle layer by means
of cage-type male mould have the following specifica-
tions:
L x B x D 41.0 x 7.9 x 3.6 ft (12.5 x 2.4 x 1 .09 m)
Hull weight 2 tons
Engine 20 hp diesel
Speed 9 knots
Vibration tests of a full-scale model showed a wooden
engine bed dispersed vibration. The thicknesses of FRP
used are :
Fig 1L L 5 GT pole and line boat
[250]
/J. 2.5 GT shell-fish ami laver boat
Side 0.1 4 + foam 0.394-0.09 in (3.5 + foam
10 + 3 mm)
Flat keel 0.14 + foam 0.79+0.09 in (3.5 + foam
20 + 3 mm)
Bilge strake 0.14 + foam 0.59 + 0.09 in (3.5 + foam
15 + 3 mm)
Deck 0. 14 + foam 0.39 + 0.1J in (3.5 + foam
10 + 2.8 mm)
Fig J3, Multi-purpose boat in FRP
Fig 14. Embarkation test of a multi-purpose boat in FRP
Tuna catcher boats
The largest FRP boat built in Japan based on the cage-
type male mould method is a tuna catcher boat (fig 20).
The specifications are as follows :
Length overall 54.3 ft (16.5 m)
Breadth 12.2 ft (3.70 m)
Depth 5.0 ft (1.52m)
Main engine 120 hp diesel, 1,500 rpm
Fig 15. Sports fishing boat in FRP
Fig 16. Engine bed of a sports fishing boat in FRP
[251]
TABLE 5: Comparison of tuna
catcher boats (wood, steel and FRP)
Hull material
Steel
Double diagonal
wooden hull
FRP sandwich
Length, ft (m)
49.4
52.5
49.25
Breadth, ft (m)
(15.04)
12.13
(16.00)
11.84
(15.00)
12.13
Depth, ft (m)
(3.70)
4.96
(3.61)
5.02
(3.70)
5.00
Cubic number ft3 (ma)
(1.51)
2,970
(1.53)
3,110
(1.52)
2,980
(84.0)
(88.2)
(84.4)
Fish-hold capacity, fta
(m")
335
388
325
(9.5)
(11.3)
(9.2)
Main engine, hp
120
90
120
Maximum speed, knots
9.1
9.4
9.7
; Displacement, ton
18.26
19.44
12.64
!KG/D
0.93
0.80
0.90
GM, ft
(m)
4.07
4.30
4.88
(1.24)
(1.31)
(1.49)
Freeboard, ft (m)
3.05
3.48
3.31
V
(0.93)
(1.06)
(1.01)
( Displacement, ton
26.84
28.81
24.49
KG/D
1.01
0.93
0.98
Departure
GM, ft
(m)
2.20
2.29
2.26
condition
(0.67)
(0.70)
(0.69)
Freeboard, ft (m)
2.49
2.88
2.52
\
(0.76)
(0.88)
(0.77)
/ Displacement, ton
38.08
37.94
29.23
KG/D
0,89
0.86
0.94
Arrival
GM, ft
(m)
1.97
1.93
2.13
condition
(0.60
(0.59)
(0.65)
Freeboard, ft (m)
1.61
2.23
2.03
^
(0.49)
(0.68)
(0.62)
Fig 17. Aspects of a sports fishing boat construction with no mould
[252]
Table 5 shows the comparison of wooden and steel boats.
Materials used are :
Shell plate: outside—glass 6 layers 0.24 in (6 mm)
core— vinyl chloride foam 0.79 in (20
mm)
inside— glass 2 layers 0.12 in (3 mm)
Deck plate: 0.59 in (15 mm) plywood covered with
two layers of glass
Scantlings of shell plates are designed to be as strong as
1.8 in (45 mm) thick cryptomeria planking, which will
protect the hull against swordfish or marlin attack.
Others
A laver fertilizer boat LxBxD = 24.6x7.9x2.78 ft
(7.5x2.4x0.85 m), weighing 1.8 tons was built with the
FRP vinyl chloride foam sandwich construction. The
cage-type male mould was used. Several FRP pleasure
boats have been modified into fishing patrol boats in
various districts.
FUTURE DEVELOPMENT
Essential research
Small localized vessels have their own traditional hull
forms developed by experience of traditional fishing
techniques and local sea conditions. This is particularly
applicable to the size of boat which could be readily
fabricated in FRP. It is difficult to introduce any drastic
change of boat building materials because of tradition.
The initial introduction should be in such items as work
Fig 18. Male-mould construction
boats, sampans and equipment like hatch boards,
ventilators, life raft cases and fishing gear, where there is
ample scope for plastic construction. The method could
then be extended to other vessels as builders become
more familiar with the material.
The introductory requirements are as follows : —
• The design should take full advantage of reduced
hull weight and emphasis placed on stability, roll
angle and damping
% Application of wooden material for engine bed,
deck and other parts should be further investi-
gated
• Instruction programmes should be arranged so
that work could be easily carried out by local
wooden boat builders
• The development of an effective inspection method
is required
• Fatigue, wear, durability of FRP vessels should be
tested by experimental boats
• Special hull forms which could only be built with
FRP such as catamaran, wave form bottom, etc.,
likely to lead to improved performance for smaller
fishing boats, should be developed
Standards and specifications
Standards should be established for work, inspection,
construction and design. Simple calculable standards may
be more useful than lists of scantlings for small fishing
vessels which have a large variety of hull forms. Design
data should show how many layers of FRP are necessary
to provide the required strength and the type of rein-
forcement fibre to be used.
Fig 79. After launch
Economic considerations
There is a deep-rooted general conception that FRP
boats are more expensive than wooden boats. The cost of
FRP pleasure vessels is the same as that for plywood ones,
because of mass production. An advantage of plastic
construction is that the boatyard may be smaller than the
conventional yard, thus reducing overhead costs.
TABLE 6: Cost of non-mould FRP boats and wooden boats (sports
fishing boats)
Non-mould
Item
FRP
Sandwich boat
Wooden
boat
£
$
£
$
Fibreglass
190
530
—
Resin (polyester)
no
310
—
—
Sandwich core
(vinyl chloride foam)
100
280
.—
Other running supplies
30
84
—
—
Timber, bolts and nails
260
730
450 1
,260
Manufacturing cost
240
670
230
645
Management cost
20
56
20
55
Total
950
2,660
700 1
,960
Note: Boat dimensions, 41.0x6.95x3.48 ft (12.5x2.12xl.06 m)
Boat type, Japanese traditional type
Boatyard, conventional wooden boatyard
[253]
If plastic vessel fabrication becomes widespread, the
cost of construction will be competitive with that of
wooden boats, especially as the cost of FRP materials is
decreasing while wood prices are increasing. If the de-
mand should become large enough unskilled labour could
be used, thus reducing costs even more.
The present constructional costs of FRP laver-collec-
ting boats in a special factory are as follows :
Female mould method :
Material cost: Resin £0.2 (US$0.6) per kg
Fibreglass £0.5 (US$1.4) per kg
Polyvinyl chloride foam £1.22
(US$3.4) per kg
Others £1.20 (US$3.3) per kg
Cost of mould : Wooden mould 7 times cost of boat
FRP mould 2 times cost of boat
Cost of man/hr: About £0.4 to £0.55 (US$1.1 to $1.5)
per unit process. One unit process is
2 kg of material.
However, a certain amount of material is lost during
the construction. The weight of a completed boat is 120 Ib
(55 kg), and the selling price is £55 (US$153), which is
much higher than the locally built wooden boat of £20 to
£25 (US$56 to $70). Generally, the selling price of FRP
vessels is estimated at £1 (US$2.80) per kg. The above cost
is estimated on the assumption that 100 vessels are built
from one mould. A choice of female, male and non-
mould methods may be made to obtain economic effici-
ency by considering the number of vessels to be built as
follows :
Female mould method
Male mould method
Non-mould method
20 to 100 vessels
20 vessels or less
1 to 10 vessels
Fig 20. 54ft (16.5 m) tuna catcher in FRP
As shown in table 5 comparing the non-mould
method with conventional wooden boat construction, the
FRP vessels cost 35 per cent more than wooden boats.
This difference for non-mould method can be reduced to
20 per cent in the near future.
A wooden boat will last five years while FRP boats will
remain in use for ten years and maintenance costs for
FRP will be far lower than for wooden vessels. Therefore,
the difference of building cost can be easily covered by
these advantages.
There are still many problems to be solved for all-
plastic fishing vessels, and the most important matters to
promote FRP vessels are as follows :
• Technical know-how of FRP boats is needed
among fishermen
• Advantage of FRP vessels on durability should be
fully utilized
• Design of special hull form should be developed
• Proper work method, inspection method and
standards should be established
• Construction costs should be lowered
When the above problems are properly solved, FRP
will surely take a firm stand in the fishing boat-building
industry, which is a quite large potential market for FRP.
[254]
A 110-ft Fibreglass Reinforced
Plastic Trawler
by Ralph J. Delia Rocca
Chalutier de 110 pieds (33,5 m) en plastique renforc*
L'intere't croissant que suscite 1'immense potentiel de production
alimentaire des oc6ans se manifeste par le besoin de nombreux
chalutiers modernes am£lior£s quant au rayon d'action et au
volume de cale. Get objectif peut etre atteint 6conomiquement par
1'emploi des interessants materiaux de construction que cons-
tituent les plastiques renforces de fibres dc verre.
L'auteur indique comment il est possible de rgaliser un chalutier
de 110 pieds (33,5 m) en partant d'une recente 6tude approfondie
concernant des dragueurs de mines 6tats-uniens. Les plastiques
renforc6s presenters des avantages dans la construction des
chalutiers, et 1'auteur les compare aux materiaux classiques.il
traite de divers aspects de la preparation des plastiques: renforts,
r6sines, precedes de moulagc, fabrication du stratifie, ainsi que des
propri£t£s physiques des stratifies recommandes.
La communication etudie la realisation de coques en plastique
renforce (panneaux simples, la coque dtant munie de membrures,
construction en "sandwich", construction mixte), et recommande
un choix de modes de construction des coques.
En conclusion, 1'auteur prgsente un avant-projet de chalutier de
110 pieds conforme aux reglements des societes de classification,
avec des 6chantillonnages compares pour le bois, 1'acier ct le
plastique renforce, et donne un rgsumg des caractdristiqucs du
batiment.
Arrastrero de plAstico de 110 pies reforzado con fibra de vidrio
El interes cada vez mayor que despierta la enorme fuente potencial
de alimentos que es el mar requiere la construccion de muchos
arrastreros de diseno mcjorado en lo que respecta al radio de
operaciones y a la capacidad de carga. Esto se puede conscguir
econ6micamentc utilizando las ventajas de construccibn que
representa el plAstico reforzado con fibra de vidrio (PFV).
Se dan los resultados acerca de la viabilidad de un diseno de
arrastrero de 110 pies, empleando como base un amplio estudio
realizado para los dragaminas de Estados Unidos. Se exponen las
ventajas de PFV para los arrastreros, compar£ndolo con otros
materiales de construccidn. Se examinan los refuerzos aplicables de
fibra de vidrio, resinas, m6todos para trazar, y construcci6n de
laminados, incluyendo las propicdades fisicas de los laminados
recomendados.
Se examina la construcci6n de cascos utilizando el PFV, inclu-
yendo forros y cuadcrnas simples de materiales mixtos o en capas, y
se scleccionan y recomiendan tipos de construcciones de cascos.
Sc da un diseno preliminar para un arrastrero de 1 10 pies basado
en normas de regulaci6n que incluyen bocetos de escantillones para
madera, acero y PFV; ademas se resumen y comparan estas
caracteristicas de los barcos.
K;CENTLY the vast potential food source in the
sea has intensified the interests of both govern-
ment and commercial organizations throughout
the world to develop and expand their fishing industries,
requiring, therefore, the replacement and expansion of the
fishing fleets, the construction of new processing facilities,
research and development to improve fish-catching
equipment and processing systems and conductance of
oceanographic studies to determine fish propagation and
migration. Most government agencies with jurisdiction
over their fishing industries are providing all or part of
the necessary funds and assistance for these programmes.
In the USA, there is similar interest and the expansion
of the fishing industry, particularly the replacement and
addition of new fishing craft, is being given considerable
attention.
Fig L 110-ft side trawler
[255]
--T-- {"Trow
I • PfAH
2. 110-ft stern trawler
In connection with this expansion, the author's
company has conducted an independent limited study
for commercial fishing boats of FRP construction. The
object was to ascertain the relative characteristics of
trawlers of FRP hull construction and standard wood or
steel construction. The trawler was selected because of its
wide use and the need to catch more fish, fish in deeper
water, reduce manual labour, be easily convertible from
one fishing method to another and be suitable for bad
weather fishing. The 110-ft (33.6 m) length was selected
as an average length for a medium-size trawler and for
comparison with a similar study conducted on US
Navy FRP minesweepers between 112 to 189 ft (34.2 to
57.8 m) (Spaulding and Delia Rocca, 1965). One stand-
ardized hull would be used for both the side and stern-
type trawlers with necessary adjustments in deckhouse
and fishing equipment locations. Fig 1 and 2 illustrate
the typical side and stern trawlers considered. The
principal characteristics of these trawlers are:
Lwl 110 ft (33.6m)
B 23 ft 6 in (7. 19m)
D 13 ft 6 in (4.13m)
The results are preliminary since the hull designs were
limited to the development of the midship sections, and
the associated characteristics being compared were
derived from Fishing Boats of the World: 2 for wood and
steel hulls and from the minesweeper study for the FRP
hulls.
COMPARISON OF HULL CONSTRUCTION
MATERIALS
Large wooden hulls of frame and plank construction
must be rigidly constructed to prevent working and
leakage at fasteners, seams and joints, resulting in scant-
lings larger than is necessary to resist the applied loads.
Wooden construction reduces space available and water
soakage can increase the weight approximately 5 per cent,
thereby reducing cargo capacity. Metal water and fuel
tanks further increase the hull weight. For the prevention
of dry rot, space is required behind the ceiling and insula-
tion for forced ventilation. Wooden hulls require
considerable maintenance and are completely rebuilt
throughout a 20-year period.
Steel hulls are heavier than wood or FRP hulls since
they require a high corrosion allowance. Insulation in
the fish hold must extend beyond the inside face of the
frame flanges. Repairs are difficult in the fish hold as
welding is not permitted on either side and the crew
cannot carry out repairs. Maintenance is high because
of the necessary periodic chipping and painting. Life
expectancy of the original hull is 20 to 25 years.
FRP is superior to both wooden and steel hulls because
of excellent durability qualities and low maintenance.
Recent US Navy surveys on a submarine fairwater
(N. Fried) and the US Coast Guard on a 40-ft (12.25 m)
patrol craft (Cobb, Jr., 1962) has substantiated this.
Time in dry dock is considerably reduced due to the one-
piece hull and deck, eliminating all caulking and re-
tightening or replacement of fasteners to maintain
watertightness. Further, FRP hulls are not subject to
accelerated weather and water exposure deterioration,
dry rot, biological attack and swelling due to water
soakage associated with wooden hulls. Impact damage is
restricted locally, minimizing repairs. Repairs to fibre-
glass hulls are simple and easy, requiring less skilled
labour and hence further reducing maintenance costs.
The life expectancy of FRP boats is not as yet deter-
mined due to its relatively recent development. Based on
limited durability reports (N. Fried, Cobb, Jr., 1962)
it appears an exceptionally long life expectancy can be
predicted.
The above and the large savings in hull weight make
[256]
FRP a most suitable and preferable hull material for
trawlers. Its versatility and properties far surpass other
materials in providing the essential requirements for a
successful design, ease of fabrication and excellent
durability.
CRAFT APPLICATIONS
FRP is a proven hull material providing satisfactory
service in commercial, naval and pleasure craft through-
out the world. Since its first application to hull construc-
tion in 1946 in the US, over a million pleasure craft and
over 2,000 US Naval craft have been built of it. Eighty
per cent of all US Naval craft purchased last year are
FRP construction. Its application to larger and larger
hulls is rapidly progressing and the limiting size is still
undetermined.
Many craft over 50 ft (15.3 m) have been constructed
of FRP and provide satisfactory service. Included are the
77-ft (23.5 m) pilot boats built in Holland, 67-ft (20.5 m)
power yachts built in England, 80-ft (24.5 m) passenger
boat and 100-ton tanker built in Russia for river service,
52-ft (15.90 m) high speed gas turbine craft and 57-ft
(17.4 m) mine-sweeper for the US Navy and a 65-ft
(19.9 m) crew boat in the USA. Of greatest interest to the
fishing industry is the recent construction of the 63-ft
(19.3 m) stern and 74-ft (22.6 m) side FRP trawlers in
South Africa (Ship and Boat Builder, 1965). This yard is
contemplating the construction of a 96-ft (29.4 m) trawler
and anticipates the construction of vessels up to 140-ft
(42.8 m) in this material. It now has a considerable backlog
of orders for large FRP fishing boats.
The results of a recent study for 112 to 189-ft (34.25
to 57. 8m) US minesweepers concluded that vessels in this
size range can be satisfactorily designed and constructed
with the present available materials, fabrication tech-
niques and construction facilities.
Other applications of FRP in the marine field giving
satisfactory service include funnels, deckhouses, hatch
covers, reefer panelling and doors, submarine super-
structures, shaft fairwaters tanks, antenna trunks,
awnings, torpedo tubes, ventilation covers and buoys.
MATERIALS AND MOULDING METHODS
Since the innovation of the fabrication of reinforced
plastic laminates with thermosetting resin and glass
fibres, continuous research and development by the
manufacturers, fabricators and government agencies
have improved resin formulations, fibreglass rein-
forcements and moulding techniques to produce good
sound structural laminates. Although there are many
types and variation of basic materials and moulding
techniques, this study is limited to those proven both
economical and satisfactory for the construction of large
hulls.
Reinforcements
New types of glass filaments with high strength and
moduli properties are now available. However, due to
economics and the medium strength-high rigidity
requirements for most hulls, the filaments in the rein-
forcements for structural laminates are still of lime-
alumina borosilicate glass with low alkali content,
known as E-glass. This glass composition has high
chemical stability and moisture resistance.
The fibreglass filaments are manufactured in parallel
bundles or strands usually consisting of 204 fine filaments
drawn together from a bushing without twisting. The
diameter of the filaments can vary from 0.00020 to 0.001 00
in (0.005 to 0.025 mm) with 0.00038 and 0.00053 in (0.0097
to 0.0135 mm) in 1 50's and 75's yarns* respectively, being
mostly used for plastic reinforcement. These basic strands
are used to make the different reinforcements such as
continuous roving, chopped strand mat, cloth and woven
roving.
For maximum laminate dry and wet strengths, the
fibreglass filaments used in reinforcements for structural
laminates are sized or finished with a coating to improve
the chemical bond between the moulding resin and the
glass filaments. Vinyl silane si/cs or finishes such as
Garan and A 172 were most widely used with polyester
resins for marine laminates until the recent development
of a new improved type (Araton). This has improved
laminate strength and other properties due to faster
and more thorough wet-out of the individual filaments
during moulding.
The economical reinforcements most commonly used
in boat hull laminates are:
• Chopped Strand Mat of short randomly oriented
fibres held together with a high solubility resin
binder compatible with the moulding resins and
varies in weight from |lo 2oz/ft2 (0.587 to 1.546
g/cm2). Mat is easy to wet out, builds up thickness
rapidly but is not as strong as cloth or woven
roving. It is commonly used in commercial boats
for the hull and decks separately or in combina-
tion with cloth, woven roving or both. It also is
widely used in both commercial and military
boats in way of contacting surfaces of joints and
secondary bonds including repairs, as a surface
ply against the gel coat and in the bonded surfaces
between the skins and cores of sandwich panels
• Woven Cloth is made of 1 50' s or 75's (30,240 or
15,120 m/kg) yarn in a plain open weave con-
struction with approximately equal strength in
both directions weighing approximately 10 oz/yd2
(70.47 g/cm2) and commonly known as "boat" cloth .
Cloth is expensive and builds up thicknesses too
slowly to be economical when used alone. It is used
for surfacing interior areas of exposed mat or
woven roving laminate to improve appearance.
It is also used for repairing damaged laminates
• Woven Roving is made of flattened bundles of
140's or 75's (28,224 or 15,120 m/kg) yarn in a
heavy plain weave construction with a slightly
greater number of strands in the warp direction.
It is available with variations in the number of
strands per bundle and width-to-thickness ratio
of the bundle. The 5x4 weave pattern weighing
approximately 24 to 27 oz/yd2 (169 to 190 g/cm2)
is most widely used for hull and deck construction
* Refers to 15,000 and 7,500 yards of filament/pound (30,240 and
15,120 m/kg).
[257]
separately or in combination with mat. Although
it is more difficult to wet out than mat, it is the
most commonly used since it is strong and builds
up laminate thickness rapidly and economically
The 140's and 150's (28,224 and 30,240 m/kg) yarn
weights are generally specified for naval boat construc-
tion and the less expensive 75's (15,120 m/kg) yarn is used
for pleasure and commercial craft. Differences in strength
and other properties for these yarn weights are negligible
for cloths and woven rovings of the same construction
and weights.
Resins
The resins used in hull construction are limited to the
thermosetting polyesters and epoxies. Although epoxy
laminates have less shrinkage and slightly better physical
and weathering characteristics, most hull laminates
and other marine products are fabricated of polyester
resins because of their versatility, ease of handling and
low cost. Laminating resins must be compatible with the
finish on the reinforcement to obtain the necessary bond
for maximum strength and durability.
Practically all pleasure and commercial boat hull
laminates are fabricated of general purpose rigid poly-
ester resin pre-compounded by the manufacturer with a
small amount up to 10 per cent maximum, of flexible
polyester resin to improve the impact resistance.
Self-extinguishing or fire-retardant polyester resins,
having approximately the same physical characteristics
as the general purpose rigid resins, are available with
slightly higher cost and weight. The small increase in cost
of the completed boat is well worth the added safety.
To prevent draining (run off) of the resin when
laminating the hull sides and transom structural lami-
nates, approximately 2 to 3 per cent maximum by weight
of silicon dioxide filler is blended into the polyester resin.
This type of filled resin, (thixotropic) resembles a heavy
oil in consistency. The fabricator can add the silicon
dioxide filler to obtain the desired consistency or pur-
chase the filled resin pre-compounded from the manu-
facturers.
To improve surface finish and increase durability,
specially compounded gel or outer surface coats of
filled resilient polyester resin are generally applied to the
female mould surface prior to laying-up the structural
laminate. Where colour is moulded into the outer surface,
organic coloured pigments in conjunction with mag-
nesium silicate, titanium dioxide, talc or other fillers and
silicon dioxide for thixotropy are added to the resin in
quantities up to approximately 20 per cent maximum
with no effect on the laminate's physical properties.
Some companies recommend that the resilient resin be
left clear with only the silicon dioxide additive and the
colour added in the subsequent layer of reinforcement
for maximum protection.
To start the polymerization or the curing reaction of the
polyester resin, a liquid or paste catalyst of 1 to 2 per cent
by weight is mixed into the resin. The rate and conditions
of the curing reaction depend on the type and amount
used. The most common types used with polyester
resins are cuemene hydroperoxide and methyl-ethyl-
ketone peroxide.
For room temperature curing of polyester resins,
without the application of heat, it is necessary to add an
accelerator such as cobalt naphthanate or manganese
naphthanate in combination .with one of the above
catalysts to start a rapid curing reaction.
When fabricating by the contact moulding method, it is
necessary to provide adequate time for impregnation
of the reinforcement with the resin between the com-
pletion of mixing and the hardening of the resin, and to
prevent excessive exotherm during curing of thick
laminates. To control this time or resin pot life, certain
combinations and quantities of catalyst and accelerator
are used. Normally, methyl-ethyl-ketone peroxide is
combined with cobalt naphthanate to obtain a rapid cure
and cuemene hydroperoxide is combined with manga-
nese peroxide to permit a slower cure with lower exo-
therm. Catalyst and accelerator must never be mixed
directly together, since this combination is explosive.
Core materials
Structural core materials for stiffeners and sandwich
panels in hull construction are limited primarily to
polyurethanc foam and balsa wood. Polyurethane foam
in various densities is more widely used for stiffeners
and bulkhead sandwich cores and balsa wood is used
for some lower hull, bulkhead and deck sandwich panels.
To obtain greater bond strength the balsa wood cores
are placed with the edge grain perpendicular to the face
laminates. Polyvinyl chloride foam is now being used as
an experimental core material in some small boats being
fabricated in the US and recently in a large catamaran
sailing vessel. Although service experience is very
limited, it is performing satisfactorily.
Applicable military and commercial specifications as
well as recommended procedures for using the basic
materials described above are available from the manu-
facturers. Additional detailed information and descrip-
tive discussions are presented (Gibbs and Cox, Inc.
1960 and 1962).
Moulding methods
Most FRP boat hulls are manufactured by the open
mould or contact moulding method with room tem-
perature cure. Partial or complete hulls, decks or bulk-
heads of sandwich construction are moulded by the
vacuum bag method to obtain a good bond between the
core and laminate faces. Matched die moulding is being
used extensively by one US boat manufacturer for hulls
up to 17 ft (5.20 m).
For larger hulls including the 110-ft (33.6 m) FRP
trawler, the contact moulding method with room
temperature cure is the only practical method now avail-
able. Future improvements and new innovations of
moulding methods may change this.
There are a number of proven techniques used with
the contact method to fabricate hulls of this size in
single skin and frames or sandwich construction. For
single skin and frames construction, a sectionalized
wood or steel female mould is the the most practical
since the entire hull, interior bulkheads and framing
can be constructed while rigidly maintaining the hull in
the same vertical position. For smaller hulls the female
[258]
mould may be rotated about a longitudinal axis to permit
the hull laminate to be laid down on a relatively hori-
zontal surface. Further, the female mould produces the
finished exterior surface.
A male mould similar to the female mould may be
used to simplify fabrication of the shell by beginning the
laminate at the keel (now at the top) and continuing
down the sides and transom. This technique has the
disadvantages of being difficult to remove the finished
hull shell from the mould, rotating it and maintaining
its shape when in the inverted position to mould in the
internal bulkheads and framing. Also the high cost of
sanding or light sandblasting and painting the outer
rough surface more than offset the advantage of moulding
the shell downwards.
For a sandwich-type hull construction it is extremely
important that an excellent bond be obtained between
the core and face laminates. This can be accomplished,
without pressure, by carefully moulding the laminate
faces down on the core. However, when the core is
placed on the inner or outer laminate face, pressure,
preferably by vacuum bagging, is necessary to achieve a
good bond.
Sandwich-type hulls have been moulded with both the
female and male moulds. Similar advantages and dis-
advantages as for the single skin and frames hull exist
with the additional cost and the problems associated with
vacuum bagging large areas.
If sandwich construction is limited to a prototype or
few hulls, an inexpensive wooden female or male form
will be more economical. With this technique the foam
core in board configuration is planked over the form
and the inner or outer laminate face is applied directly
on the core, depending on which type of form is used.
After the first applied laminate face is cured, the par-
tially completed sandwich must be inverted to lay-up
the laminate face on the opposite side of the core to
complete the sandwich. The advantages of being able to
mould-in bulkheads and framing and having a more
rigid structure to rotate will occur when the female form
is used.
Based on the above, the use of a female mould for
fabricating either a single skin and frames or sandwich-
type hull is considered to be the most practical since the
entire hull and internal bulkheads and framing can be
constructed without inverting a partially completed hull
and having a finished outer surface.
Laminate construction
Structural fibreglass-polyester laminates may be rein-
forced with chopped strand mat, cloth or woven roving
used individually or in combinations. Considering all
other factors equal, the strength of a laminate is directly
proportional to the type and amount of fibreglass
reinforcement it contains. Other factors which affect
strength are the resin, chemical finish on the fibreglass
filaments, moulding method, fabrication techniques,
quality control and experience. The most important
factor in the fabrication of FRP hulls is that the manu-
facturer creates the structural material as well as the hull
configuration. Through his experience and a quality
control system, the basic materials, the moulding
method and technique, and the environmental conditions
are selected to construct the laminate best suited to the
application by the most economical production
procedure.
The strength of FRP laminates can be varied to
compare favourably with wood, steel, aluminium and
other high strength materials. If necessary extremely
high strength laminates of approximately 300,000 lb/in2
(21,130 kg/cm2) tensile strength, can be produced with
special reinforcements and resins by the iilamcnt-
winding process. However, to construct a large FRP
trawler which will be economically and operationally
competitive with wood and steel trawlers, the basic
materials available now must be judiciously selected and
moulded.
Therefore, the laminate selection was limited to E-type
glass of mat, composite mat-woven roving or all woven
roving reinforced polyester resin fabricated by the
contact or hand lay-up moulding method with room
temperature cure. These laminates correspond re-
spectively to the "low", "medium" and "high" glass
content laminate classification established by SNAME
(Structural Plastics Task Group of the Hull Structures
Committee, 1965). The physical properties given in
table 1, obtained from the above classification, were used
for the preliminary structural design of the FRP trawler.
The results of a comprehensive study of the effect of
glass content on laminate unit weight and cost conducted
for the large minesweeper hulls (Spaulding and Delia
Rocca, 1965) using the same basic materials and the
conservative values given (Gibbs and Cox, Inc., 1962
and SNAME, 1965) indicated that, although the mini-
mum laminate weight occurred at approximately 50 per
cent glass content by weight, there is very little increase in
weight between 35 and 60 per cent. This is due to the
relationship between strength and density which varies
with the glass content. Laminates in the low glass
content range have lower strengths and densities re-
quiring greater thicknesses and those in the high glass
content range have higher strengths and densities re-
quiring lesser thicknesses resulting in little difference in
the unit weights, within the 35 to 60 per cent glass
range. However, assuming the cost of the mat and woven
roving reinforcement is the same, there is a significant
increase in materials cost, approximately 19 per cent.
For this study, the selection of the laminate reinforce-
ment need not depend on strength and unless a high
modulus of elasticity is required for longitudinal bending
deflection, the most economical within weight limitations
is preferred.
The mat laminate with 25 to 30 per cent glass content
may be the most economical but will have the greatest
hull weight. A composite laminate of alternate plies of
2 oz/ft2 (1.566 g/cm2) mat and 24 to 27 o7./yd2 (169 to
190 g/cm2) woven roving reinforcement with an average
glass content of about 35 per cent will increase the
material cost approximately 5 per cent above the all mat
laminate and will decrease the weight approximately
3 per cent. An all 24 to 27 oz/yd2 (169 to 190 g/cm2)
woven roving laminate with an average glass content of
about 50 per cent will increase the material cost approxi-
[259]
i2
mately 16 per cent above the all mat laminate and will
decrease the weight approximately 4 per cent.
Therefore, it appears that the all mat laminate should
be selected. However, the composite mat-woven roving
laminate at a 5 per cent increase in cost will reduce the
weight 3 per cent, will increase the hull bending modulus
approximately 30 per cent and will increase the impact
resistance of the hull considerably. Further, the mat-
woven roving laminate is much easier to fabricate,
requires less labour due to the reduction in weight and
gives excellent service with minimum maintenance and
repairs. These advantages are well worth the extra cost
of the basic materials which is negligible when con-
sidering the total costs.
Since both these laminates are equally attractive, the
preliminary design for the FRP trawler was based on
both.
It should be noted that the construction selected in the
minesweeper study is the all woven roving reinforced
polyester with 50 per cent glass content. This was based
on both naval and navy boat contractors' experience
with this standard construction, and its higher strength,
moduli and impact resistance.
HULL CONSTRUCTION
Since there is much controversy as to the most appro-
priate material for the internal framing of large FRP
hulls, various structural systems of FRP, aluminium and
wood were investigated for both single skin and sand-
wich construction for the minesweepers (Spaulding and
Delia Rocca, 1965). The composite mat-woven roving
polyester laminate with 35 per cent glass content was
used as the fibreglass reinforced plastic material.
The following nine different framing systems were
evaluated for ease of attaching framing to skin, con-
tinuity of the framing system, remaining useful volume,
simplicity of framing, ease of maintenance and repairs,
ease of attachment of fittings and equipment, hull
thermal insulation qualities and midship sectional
properties.
FRP single skin hull construction
(1) Closely spaced FRP longitudinals and widely spaced
FRP transverses
(2) Closely spaced FRP transverses
(3) Closely spaced aluminium longitudinals and widely
spaced aluminium transverses
(4) Closely spaced aluminium longitudinals and widely
spaced FRP transverses
(5) Closely spaced FRP longitudinals and widely spaced
aluminium transverses
(6) Closely spaced aluminium transverses
(7) Closely spaced wood transverses
FRP sandwich hull construction
(8) Widely spaced FRP longitudinals and FRP trans-
verses
(9) Widely spaced aluminium longitudinals and alu-
minium transverses
The results of this investigation indicate that all the
FRP framing systems 1, 2 with the single skin shell
construction, and system 8 with the sandwich construc-
tion have many advantages over the others considered.
Framing systems 1 and 2 are considered the most
economical to construct, maintain and repair. Of these
two, longitudinal framing system 1 is preferred since
all of the longitudinals contribute to the longitudinal
bending strength and stiffness of the hull and because
this system is considered simpler and more economical
to construct.
Framing system 8 with sandwich construction of the
same laminate construction and polyurethane foam core
provides excellent thermal insulation qualities, has a
minimum number of frames with greater unobstructed
interior areas and minimum maintenance requirements.
However, it will be more difficult and costly to construct
and repair. Further, sandwich construction with the
thick faces and core required for these large size craft
are very difficult to inspect for complete quality assurance
and very difficult to locate minor damage and leakage
prior to it becoming necessary to carry out extensive
repairing.
Framing systems 3, 4, 5 and 9 of full or partial alu-
minium can provide lighter and stiffer hulls but are not
recommended due to increased costs and construction
time, and the difficulty to construct, maintain and repair.
Further, the problem of attaching and maintaining the
aluminium frames to the fibreglass laminate has not been
completely resolved and previous limited experience has
not been too encouraging. Also, the effect of the dif-
ferences in moduli, rate of thermal expansion, etc. have
not been resolved. Considerable research and develop-
ment is necessary before these framing systems can be
applied with complete assurance.
The closely spaced wood transverses framing system 7
is considered unacceptable and not recommended since
many of the problems associated with similar aluminium
systems will also apply but with far greater emphasis on
maintenance. Undesirable increased hull weight above
the all FRP system is another important disadvantage.
It was concluded that further investigation of the large
FRP trawler would be limited to the single skin and
longitudinally framed hull and sandwich constructions.
Economical studies were made of the effects of
variations in framing spacing for the single skin and
frames construction and the variations in the thicknesses
of the faces and core for sandwich construction for a
FRP minesweeper.
For the single skin and frames construction, it was
concluded that in general closer spaced longitudinals
and transverses will result in a lighter structure due to the
associated reduction of shell thickness. However, this
will increase the complexity of construction and associ-
ated fabrication costs. The effect of the variation in
laminate glass content between 35 and 50 per cent was
also considered and found to be inconsequential in
regard to unit weight and cost of materials.
For the sandwich construction study, the laminate
construction used is the same as used for the single skin
and frames construction. The core material selected is
polyurethane foam of 6 to 8 lb/ft8 (2.87 to 3.83 kg/ma)
[260]
density. Results indicated that the best compromise
for weight and cost requires a core depth of approxi-
mately 3 to 4 in (76 to 101 mm) with approximately | in
(9.5 mm) thick laminate faces. In addition to the 6 to 8
lb/ft3 (2.87 to 3.83 kg/m8) density foam, closely spaced
internal vertical shear webs of similar laminate con-
struction are considered necessary for over-all rigidity,
shear strength and to resist large local impact loads.
When compared to single skin and frames, a hull of
sandwich construction as considered for this study, is
slightly heavier in weight and substantially more costly.
HULL STRUCTURAL DESIGNS
To ascertain hull structural configurations for evaluation
of the proposed FRP trawler, preliminary structural
designs were limited to the development of representa-
tive midship sections of a typical 1 10-ft (33.6 m) trawler
of wood, steel, FRP single skin and frames and sandwich
type constructions.
Specific design criteria such as water loading for the
shell, decks, bulkheads, flats, etc. are not available since
trawler scantlings are generally derived from previous
proven designs. Where applicable, scantlings were de-
veloped in accordance with recommendations and rules
established by authoritative organizations.
Wood trawler
The midship section developed for the wood trawler is
illustrated in fig 3. The scantlings are based upon tables
20 and 21 of Traung (1960) and are representative of
bent frame wood construction now used on the US west
coast. Although specific construction details vary from
country to country, the basic structural arrangement is
considered typical of the majority of wooden fishing
vessels of this size. Mo additional insulation is required
in way of the fish hold because of the excellent insulation
properties of the hull planking and inner ceiling.
Steel trawler
The midship section developed for the steel trawler is
illustrated in fig 4. The steel scantlings given in fig 4 are
derived from table 23 of Traung (1960) and are intended
to satisfy the minimum requirements of both Lloyds
Register of Shipping and American Bureau of Shipping
Rules, 1965. Transverse framing is used throughout,
with non-tight floors on each frame. All framing members
and plating surfaces in the fish hold must be insulated
and sheathed.
FRP trawler single skin and frames
Fig 5 illustrates the proposed fibrcglass construction
for a trawler of single skin and longitudinal frames
KEELSON 14" X 18"
SlSTFR KEELSON 12"
. All MATERIAL DOUGLAS Fl R OR
EUUIVALFNT SOfT WOOD UNLF5.S
NOTED.
. KLOOR 5" X f." WHITE OAK
. ..ARDQARD 5" X 1 ?" \_ BLOC.K)NG 5" TH«CK
- KEEL 14" X lt>"
:-,Hor 3" RED OAK
Fig 3. Midship section JJO-ft wooden trawler
[261]
GUARD 6" X 6"
WHITE OAK
CENTER KEEL • 5/16
(12.75 LBS/FT2)
1. ALL MATERIAL MEDIUM STEEL
UNLESS NOTED,
nOTTOM SHELL 5/1 6*
(i p. 75 LBS/FTC)
. Midship section 1 10-ft steel trawler
DECK LONG I TUD^NAL1-.
* 4* X 3" X .l7*J\. ' \
SPACED IB" O.C. \
Plf TtfB — "y IS
TlT ^T y ^j»
~™/ 7
B"x3%.LJl"J\. — / KACL Of /
SPACED 6'-0'r O.C. INSULATION — /
A SHEATH I NT.
'.fNTrR KLLL
WEIJS, . vn"
f I ANGL "-I/"'
TANK. TOP PANEL'.
2" THICK CORE
.21" TOP & BOTTOM
UUARD 0" X 6H
WHITE OAK
1. LAMINATF5 CONSTRUCTED OF ALTEWNATE
PLITS or ? OZ/SQ. n. MAT AND 24 -
27 OZ/SQ. YD. WOVEN KOVING.
2. ALL COKE MAUKIAL MOLYURETHANC FOAM
OR EQUIVALENT:
Z LB-VCU FT DENSITY FOR LONGI-
TUDINALS 6-8 LnS/OJ FT DENSITY
FOR TRANSVERSE FRAMES, LONGITUD-
INAL OIRDCR'j, CENTER KLEL AND
TANK TOP F'ANELV
s*rtinn J 10-fi fihreelass trawler. Sinele skin and frames
TABLE 1. Physical properties of typical marine laminates41
Physical property}
Per cent glass by weight
Specific gravity
Flexural strength
lb/ina x 103
kg/cm2 x 10"
Flexural modulus
Ib/in3xl06
kg/cm2 x 10°
Tensile strength
Ib/in2xl08
kg/cm2 xlO6
Tensile modulus
Ib/inaxl06
kg/cm2 x 10°
Compressive strength
lb/in*x!03
kg/cm* xlO3
Compressive modulus
lb/ina x 106
kg/cm2 x 10°
Shear strength perpendicular
Ib/inaxl03
kg/cma x 103
Shear strength parallel
Ib/inaxl03
kg/cm2 x 103
Shear modulus parallel
Ib/inaxl06
kg/cm2 x 10°
Average values for guidance only
Chopped strand Composite Woven roving
mat laminate laminate^ laminate
Low glass Medium glass High glass
content content content
25-30 3(MO 40-55
1.40-1.50
18-25
1.27-1.76
0.8-1.2
0.06-0.08
11-15
0.77-1.06
0.9-1.2
0.06-0.08
17 21
1.20-1.48
0.9-1.3
0.06-009
10-13
0.70-0.91
10-12
0.70-0.85
0.4
0.02
1.50-1.65
25-30
1.76-2.11
1.1-1.5
0.07-0.11
18-25
1.27 1.76
1.0-1.4
0.07 -0. 10
17 21
1.20 1.48
1.0-1.6
0.07-0.11
11-14
0.77-0.99
9-12
0.63-0.85
0.45
0.03
1.65-1.80
30-35
2.11-2.47
1.5-2.2
0.11-0.16
28-32
1.97-2.25
1.5-2.0
0.11-0.14
17-22
1.20-1.55
1.7-2.4
0.12-0.17
13-15
0.92-1.06
8-11
0.56-0.77
0.5
0.035
* Properties from short-term loading tests— wet condition. Composite and woven roving
values for warp direction.
t Tested in accordance with ASTM Standard Specification or equivalent Federal Standard
LP-406b.
J Based on typical alternate plies of 2 oz/ft2 (1 .566 g/cma) mat and 24 oz/yd2 (169 g/cma) woven
roving.
supported on widely spaced transverse webs. The scant-
lings indicated are representative of a composite rein-
forced laminate laid up with alternating plies of 2 oz/ft2
(1.57 g/cm2) mat and 24 to 27 oz/yd2 (169 to 190 g/m2)
woven roving. These scantlings are based on the
average physical and mechanical properties for a
composite laminate of 35 per cent glass content given
in table 1,
The scantlings were derived by calculating steel scant-
lings to the American Bureau of Shipping Rules and
converting them to equivalent FRP scantlings. Plate
panels were converted on the basis of providing equal
stiffness, requiring steel thicknesses to be increased by
the cube root of the flexural moduli. Beams and frames
scantlings were converted by the direct ratio of tensile
strengths.
The scantlings so derived were compared with the
requirements of the new Lloyds SR 65/39 Provisional
Rules being prepared for the application of FRP to fishing
craft and were found to be in remarkably close agreement.
In fact, the only differences were in the main deck
longitudinals and the web frame at the bilge, which are
1 in (25.4mm) deeper than required by Lloyds. A review
of the first draft of these Lloyds Rules, which are subject
to revision prior to publication, indicate that they are
exceptionally well compiled and in considerable detail.
The scantlings given in the Rules are for an all-mat
reinforced polyester laminate moulded by the contact or
hand lay-up method. However, the designer is permitted
to modify the scantlings where fibreglass reinforcements
other than chopped strand mat are used.
Tn order to evaluate the effects of glass content on the
weight, strength and cost of the FRP trawlers, similar
calculations were made for an all-mat reinforced laminate
with a glass content of approximately 25 per cent.
Although this results in skin and frame laminates about
10 and 20 per cent thicker than those given in fig 5
respectively, the laminate specific gravity is reduced to
about 1.42 from 1.50.
Though a nominal thickness of foam insulation would
[263]
mCK PANEL
3 -I/.'" 1HKK f.OKf. —7
.37* TOP PAC-t /
.:M" BOTTOM FACC /
f'HFAK WMl'> At h" O.C/
GUARD 6" X 6"
WHITC OAK
I DP \ BOTTOM PANEL
i- 1/'" THICK f.OHF
', ln nillMOAHI) I Af.C
.'!" INHOARD fACE
ICAR WEBS AT (.>" O.C.
1. LAMINATn ON'-'TWDf ! FD Or Al TEKNATE
PI IF'" nr ;' 02 /:''«. TT. MAT AND i-:4 -
?7 OZ'MJ.Vfi. WOVFN WVINC.
£« All r-)HC MAtriviAL TO Bf f: - 8 LH/
r u. n . in wr, i T r POI ru»t THAW roAM
OK f UU I VAl TNT .
MPf
Wni'. .50"
MANSE '-" X .1.0"
Fig 6. Midship section 1 W-fi fibreglass trawler. Sandwich construction
be required in the fish hold adjacent to the outer skin, the
framing members will not require additional insulation
since their polyurethane foam cores will be more than
adequate.
FRP trawler sandwich
Fig 6 presents the alternate FRP trawler utilizing sand-
wich construction for the shell and deck. The design of
this hull structure is based upon providing equivalent
panel strength and stiffness as provided by the single
skin and frames. Again, both the composite laminate of
alternate plies of mat and woven roving and an all-mat
laminate were considered. The all-mat panels require
face thicknesses about 20 per cent greater than those in
fig 6. The transverse frames are similar to those used
for the single skin and frames design. Additional
insulation is not required in way of the fish holds since
the polyurethane core has more than adequate thermal
protection.
The core material selected for the sandwich construc-
tion is a 6 to 8 lb/ft3 (2.87 to 3.83 kg/m3) density poly-
urethane foam or equivalent, which is required to resist
local bearing loads on the face of the laminate, and to
transfer the shear loads between the skin and core as
well as between the individual panel and frame. In
addition, it may be necessary to incorporate laminate
shear webs, as shown in fig 6.
COMPARISON OF TRAWLER
CHARACTERISTICS
To evaluate and compare the characteristics of the
proposed FRP trawler with the equivalent wood and
steel vessels, estimates of capacities, weights, costs, etc.
were prepared based on the midship sections presented
in fig 3, 4, 5 and 6. Additional information regarding
fish gear, machinery, etc. was obtained from Traung
(1960).
Table 2 compares the weight, area, stiffness and
strength characteristics of the four midship sections
illustrated. The weights of wooden members are based
upon a specific gravity of 0.45 and 0.70 for soft and hard
wood respectively, and the fibreglass laminate specific
gravities are assumed to be 1.42 and 1.50 for the all-mat
and composite mat-woven roving laminates respectively.
The use of FRP in lieu of wood significantly reduces the
weight of the primary hull structure by 43 to 53 per cent.
The single skin and frames is about 10 per cent lighter
than the sandwich construction and the use of the
composite mat-woven roving laminate will save about
5 per cent in weight over the all-mat laminate construc-
tion. The steel and wood midship sections are approxi-
mately equal in weight.
The use of FRP construction will increase the net
cross sectional area in way of the fish hold approximately
16 per cent over the wood construction, while the cor-
[264]
TABLE 2. 110-ft (35.6 m) trawler comparison of midship sections characteristics
FRP
Wnntt
St * Single skin & frames
Sandwich
rr \HtU
Mat
Mat-roving
Mat
Mat -roving
Weight/ft amidships*
Ib
1,500
1,510
760
700
850
770
(kg)
(680)
(685)
(345)
(318)
(386)
(349)
Weight/ft relative to wood
—
1,00
.51
.47
.57
.52
Hold area inside sheathing
ft2
200
220
230
230
234
234
(m2)
(18.6)
(20.4)
(20.4)
(21.4)
(21.7)
(21.7)
Hold area relative to wood
-•-
1.10
1.15
1.15
1.17
1.17
Moment of inertia, 1 1
in4 x 103
16,660
1,242
4,173
3,641
4,285
3,590
(cm4x!03)
(686,730)
(51,230)
(171,990)
(150,140)
(176,680)
(148,000)
Modulus of elasticity, E
lb/in3 xlO6
.85J
30
.95
1,2
.95
1.2
(kg/cm2 x 10")
(0.060)
(2.1)
(.067)
(.085)
(.067)
(.085)
El
lb/in2 xlO13
14.1
37.3
4.0
4.3
4.0
4.3
(kg/cm* x 1012)
(41.3)
(109)
01.7)
(12.6)
01.7)
(12.6)
Stiffness relative to wood
—
2.6
.29
.31
.29
.31
Section modulus
in3 xlO3
190.4
13.6
46.2
40.4
47.9
40.2
(cm3 x 103)
(3,121)
(242)
(757)
(663)
(785)
(659)
Stress for 2.7 x 106 ft Ib Mom.,
lb/in2
170
2,190
700
800
680
810
(kg/cm2)
(11.9)
(154)
(49.3)
(563)
(47.9)
(57.1)
Ultimate strength
Ibin2
6,500§
60,000
14,000||
17,000«[
14V000||
17.000H
(kg cm2)
(458)
(4,227)
(986)
(U97)
(986)
(1,197)
Ultimate factor of safety
38
27
20
21
21
21
* Includes tank top, but neglects insulation or sheathing
t Neglects tank top, wood ceilings
Actual modulus for wood, 1 .7 x 106 lb/in2, reduced 50 per cent for slippage of joints
§ Ultimate compressive strength of Douglas fir
H Ultimate tensile strength of chopped-strand mat (SNAME, 1965)
II Ultimate compressive strength of composite mat-roving laminate (SNAME, 1965)
responding increase for steel is about 6 per cent less, due
to the necessity of insulating the tank top and framing
members.
Due to the inherent flexibility of FRP, the relative hull
deflection for both single skin and frames and sandwich
construction will be about 3J times that of the equivalent
wood trawler, assuming twice the calculated deflection
of the wood trawler to account for joint slippage, and 9
times that of a steel trawler, for equal bending moments.
This flexibility will not seriously affect the performance of
a trawler with machinery aft. However, with the mach-
inery well forward, stresses due to excessive hull deflec-
tion may be induced in the propeller shaft and bearings
which will have to be considered when designing. If
necessary, the hull deflection can be reduced by increasing
the all-mat or composite mat-woven roving laminate
thicknesses or providing a laminate with a higher elastic
modulus such as an all-woven roving laminate.
The stresses in the fibreglass laminate hull, though
greater than those of the wood hull, are not considered
significant. The fact that the safety factor for the wood
hull is nearly twice that of the fibreglass hull is indicative
of the relative inefficiency of wooden construction, where
shell scantlings far in excess of those dictated by normal
loadings are necessary to provide sufficient overall hull
rigidity and tightness. The tank top has not been in-
cluded in the calculations of hull stiffness or strength,
since it is often discontinuous in way of the machinery
spaces.
Light ship weight
Table 3 presents estimated light ship weights for the
structural configurations considered. The hull structure
for the wood trawler was estimated by proportioning the
weight/foot amidships from table 2 to that of a similar
vessel with a known hull structural weight. The steel hull
structure is obtained from Fishing Boats of the World : 2
and is about 10 tons heavier than the wooden hull. Since
the weight of the shell and deck of the steel and wood
trawlers will be nearly identical, this 10-ton increase
reflects the greater weight of the steel bulkheads, flats,
deckhouses, etc.
The hull structure weight of the single skin and frames
fibreglass trawlers were based both on the savings in
weight/foot amidships (table 2) and the results of a similar
study of a 110-ft (33.6 m) fibreglass Inshore Mine-
sweeper (SNAME, 1965). Proportioning results of this
study indicate that although the use of FRP in lieu of
wood reduces the weight of the shell and decks 49 to 53
per cent amidships for the all-mat and composite mat-
woven roving laminates respectively, the reduction in
overall hull structural weight will be only about 38 to 41
per cent. This reflects the reduced weight savings in such
items as bulkheads, flats and deckhouses.
For the sandwich construction hull, the 43 and 48
per cent reductions in weight per foot amidships relative
to wood construction, table 2, are equivalent to a 34 and
38 per cent reduction in overall hull structural weight,
table 3. The use of sandwich construction is seen to add
about 5 tons to the hull structural weight.
These hull weights are combined in table 3 with the
outfit, machinery and fish gear weights obtained from
Traung (I960) and a 10 per cent margin is added to
obtain the light ship weights. An additional margin of
5 per cent is included for the wood hull weight for
soakage.
[265]
TABLE 3. 110-ft (33.6 m) preliminary light ship weight estimates
FRP
Wood Steel
120
50
7
25
202
20
10
232
Hull structure — tons
Outfit and hull Eng.-~ tonst
Fish gear— tonst
Main and aux. machy — tons§
Sub total — tons
Margin — design (10 per cent)— -tons
Margin — soakage (5 per cent)— tons
LIGHT SHIP— tons
Hull structure relative to wood
Light ship relative to wood
* From fig 283, Traung (1960)
t From fig 284, Traung (1960)
j Estimate 3 per cent of light ship, Traung, (1960)
§ From fig 285 and 286, Traung (1960)
The significant weight savings resulting from the use
of FRP construction can be used to increase fish-hold
capacity, endurance and reduce horsepower, individually
or in combination. The use of integrally-moulded fuel
and water tanks in a FRP hull, instead of the indepen-
dent metal tanks now used in most wooden trawlers,
will permit significant increases in available tank capacity
by eliminating voids adjacent to the shell and decks.
The reduction in the light ship weight will cause an
increase in light ship vertical centre of gravity of about
5 per cent. This is due to the reduction in hull structure
weight having a centre of gravity below the overall light
ship centre. Consequently stability requirements must be
considered early in the preliminary design,
Light ship cost
Preliminary light ship cost estimates presented in table 4 are
based upon US construction at current average wage and
productivity scales. In view of the wide regional variation
the costs given are approximate though the trends
indicated are quite significant.
To establish a valid basis for cost comparison, it is
necessary to assume that the techniques in constructing
large fibreglass hulls is sufficiently advanced that all
problems associated with logistics, manpower utilization,
lay-up techniques, etc. have been satisfactorily resolved,
and the required facilities are readily available. Present
experience is very limited, and so it can be assumed that
the costs derived in this study are somewhat optimistic
but should stabilize to the indicated ranges as further
experience is gained.
Material costs for wood and steel are derived from
Traung (1960). FRP material costs are based upon the
following recent prices assuming bulk purchasing:
Costs
Item UK shilling lib t/lb
General purpose resin (non-fire
retardant) 1.75 0.245
2 oz mat (27.6 g) 3.44 0.48
24-27 oz woven roving
(169-190 g) 3.52 0.49
Polyurethane foam
(prefoamed boards) 7.17 1.00
130*
50
7
25
212
21
233
1.05
1.01
Single skin & frames
Mat Mat-roving
75 71
50 50
7 7
25 25
Sandwich
Mat Mat-roving
80 75
50 50
7 7
25 25
157
16
173
.62
.75
153
15
168
.59
.72
162
16
178
.66
.77
157
16
173
.62
.75
The resultant single skin laminate and sandwich unit
costs were increased to account for other materials
(metal, wood, castings, doors, etc.). All material weights
were increased 15 per cent to account for wastage, and
the 10 per cent design margin in table 3 was included.
Productivity rates are very difficult to evaluate since
they vary widely. For the production of a single hull, the
values shown in table 4 are considered to represent
average rates. The productivity value for sandwich
construction of 300 to 310 man-hours/ton is tentative
and reflects the slower lay-up rate of foam core material.
Wage rates for fibreglass laminators vary from £0.54
to £0.895/hr ($1.50 to $2.50/hr) with £0.627 ($1.75)
representing a fair average.
The costs of outfit, hull engineering, machinery and
fish gear are derived from Traung (1960) and are con-
sidered constant for all structural configurations. Mould
costs are based upon the FRP minesweeper study and are
representative of an open sectionalized female mould for
the single skin and frames hull and a less expensive open
framework for the sandwich hull. Deck moulds and
special scaffolding are included.
The effects on labour costs for the duplication of hulls
were determined by applying a reduction factor, de-
veloped from limited US Navy and industry information,
to all direct labour costs in accordance with the following
list:
Hull number
1
2
5
25
Relative labour cost
1.00
.943
.849
.670
These values result in a laminating rate of 15 Ib per
man-hour (68 kg/hr) for the twenty-fifth hull. This is
considered representative for production of FRP hulls
by the contact or hand lay-up moulding method.
The costs given in table 4 are plotted in fig 7 and indi-
cate that FRP construction will be more expensive than
either wood or steel, particularly for a single hull. How-
ever, for 5 identical hulls or more, the cost of a single
skin and frames fibreglass trawler will be approximately
5 per cent greater than the wood or steel. Sandwich
[266]
B
*l H'
I
s« s
""
sss
o 8 "^ 5"§S?S5RSRS5S2
'g ^ ^ «o ^ JD^ 2{? 25 SS^vS^S^
S» ^^ ^^ rr* *
•^ ^r '••i ^^ r**
,2 «e "- • *"" ^ C^IC>I*-^
•^ oo ^ '
I [.....
I .1 -!SSaSmsog"g~^3 jfg
! I * 3 °;
^ <TJ *C* <
^^ #»v ®^ ^* - I
1 ! !
OS
J2
s
ill
111
I
[267]
200
5 io 15 20
Number of Identical Hulls
Fig 7. 110-fi trawler — Preliminary Cost estimates
construction is considerably more expensive, approxi-
mately 26 to 28 per cent.
The cost differential between the all-mat and the
stronger, lighter composite mat-woven roving laminate
construction is negligible. Within the accuracy of these
estimates, it can be concluded that the cost of a FRP
hull is relatively unaffected by glass content. Similar
studies for the all-woven roving laminate used in the
minesweeper study confirms this conclusion for up to
50 per cent glass content.
It is instructive to study the overall cost per pound
for the hull structure. These values are shown below for
a procurement level of 5 hulls :
Cost
Hull material £/lb $/lb
Wood 0.172 0.48
Steel 0.150 0.44
FRP single skin all-mat laminate . . 0.305 0.85
FRP single skin mat-roving laminate . 0.32 0.89
FRP sandwich panel all-mat laminate . 0.40 1.12
FRP sandwich panel mat-roving laminate 0.42 1.17
This indicates that the favourable cost structure of the
single skin and frames construction is directly attribut-
able to the significant weight reduction achieved. This
favourable comparison is strictly limited to a large,
relatively heavy planked wood being replaced by a lighter
fibreglass hull. For smaller boats, or those incorporating
a laminated plywood hull, the use of FRP construction
will result in a higher first cost relative to wood or steel
construction.
CONCLUSIONS
FRP as a hull material for large trawlers averaging 110 ft
in length is considered feasible and practicable. The
reality of their construction is virtually assured in view
of the South African shipyards9 experience of the 63-ft
and 74-ft trawlers and their anticipation of building
similar vessels to 140 ft of the same material.
Considerable advantages are available over wood and
steel trawlers in weight and space saving, reduced
Maintenance, ease of repair and excellent durability.
[268]
TABLE 5.
110-ft trawler, summary
r of characteristics
Characteristic
Wood
Steel FRP*
Capacity
Fish hold volume — ft3
6,000 (165.6m3)
6,600 (182 m3) 6,900 (190 m3)
Tons iced fish
110
120 125
Light ship weight — tons
232
233 168-173
Maintenance
Constant
Constant Light
Vulnerability
/Fire, Rot,
\ Marine Borers
Rust Firet
Repairs
Difficult
Moderate Simple
Estimated cost
1 trawler
£114,800
£115,500 £141,500 to 141,900
($319,700)
($322,200) ($394,700 to 396,600)
Each of 5
£104,100
£103,700 £109,100 to 109,700
($290,500)
($289,300) ($304,500 to 306,100)
Each of 25
£90,850
£90,750 £94,950 to 95,250
($253,500)
($253,200) ($264,900 to 265,800)
* Fibreglass reinforced plastic single skin and frames construction
t Greater fire resistance to wood by the use of fire-retardant self-extinguishing polyester resin.
Construction costs for procurement of five or more
hulls are competitive.
Results of a recent industry survey (Spaulding and
Delia Rocca, 1965) in the USA indicates that there are
several interested organizations with adequate facilities
and plastic fabrication experience in large boat and other
structures, and similar interests and capabilities exist
throughout the world.
At present, the single skin and frames construction
with closely spaced longitudinals and widely spaced
Fig 8. 110-ft fibreglass trawler
transverses, fabricated in a sectionalized female mould
by the contact or hand lay-up moulding method with
room temperature cure polyester resin is the most
attractive.
Other important advantages of FRP trawler con-
struction are greater cargo capacity, less vulnerable to
rot, borers and corrosion and greater resistance than
wood to fire damage by the use of fire-retardant or self-
extinguishing resins at a slightly higher cost.
A summary of the important trawler characteristics
for wood, steel and FRP single skin and frames construc-
tion is presented in table 5. Except for slightly higher cost,
the FRP trawler is superior to both the wood and steel
trawlers in regard to capacity, weight, maintenance,
vulnerability and repair.
Fig 8 presents a proposed FRP 110-ft stern trawler
which can be developed, and constructed with available
basic materials in a number of shipyards with adequate
facilities and experience.
The ease of forming complex shapes with this material
results in a ship form with smooth flowing lines and
surfaces, and should be a safe, sound ship providing
many years of satisfactory service with minimum
maintenance.
The opinions expressed are those of the author and should not be
construed as reflecting the official views of Gibbs & Cox, Inc.
Acknowledgments
Acknowledgments are due to Mr. M. G. Forrest, Vice President-
Naval Architect, and Mr. R. L. Scott of Gibbs & Cox, Inc.
[269]
Comparison between Plastic and
Conventional Boat-building Materials
by D. Verweij
Comparaison entre le plastique renforce et les mat&iaux classiques
employes en construction navale
Le plastique examin6 est un polyester arm6 de fibres de verrc. Les
caract&istiques de ce produit peuvent varier selon le type de ren-
forcement adopt£, mais la communication n'&tudie a fond que le
polyester renforce de "mats" (feutrcs de verre) et de tissus de
"roving".
L'auteur expose une m&thode permettant de comparer les
caract6ristiques m£caniques, et ddcrit un critere judicieux de
comparaison fonde sur la resistance a la traction et a la flexion et sur
la rigidite.
II rapproche ensuite le polyester armd de verre textile des mat£ri-
aux traditionnellement utilises en construction navale, pour con-
clure que ce stratifie soutient bien la comparaison avec les m&taux et,
sauf sous le rapport de la rigiditd, avec divers bois.
Apres avoir expos£ les a vantages de la construction en "sand-
wich" avec du polyester renforce de fibres de verre, 1'auteur dtudie
les propridtes mteaniques de ce mat&riau, qui sont jugees satis-
faisantes.
Enfin, il examine le polyester arm6 sous Tangle de la resistance a
a corrosion, de 1'entretien, et de la facilit6 de reparation.
Comparaci6n entre los materiales plasticos y los de tipo corriente en
la constniccidn de embarcaciones
£1 material plastico utilizado es la fibra de vidrio reforzada de
pollster (FRP) y puede variarse segun el tipo de refuerzo aplteado,
pero solamente sc cxamina a fondo la FRP reforzada con esterilla y
mecha trenzada.
Se investiga el m6todo de comparacidn de las caractcrfsticas
mecanicas y se explica el criterio correcto de comparaci6n basado
en la resistencia a la tracci6n, la resistencia al corte y la rigidcz.
Seguidamentc se comparan la FRP y los materiales corrientes
para la construcci6n de barcos y se descubre que la FRP se puede
enfrentar con ventaja con los materiales metalicos y, salvo en lo
referente a la rigidez, con varias maderas.
Se expone la necesidad de la construcci6n con FRP en forma de
capas intcrcaladas, estudiandose las propiedadcs mecanicas de
este tipo de material y comprobandose que rcsultan favorables.
Por ultimo se examina la durabilidad, por lo que respecta a la
resistencia a la corrosi6n y al mantenimiento, y tambien la facilidad
de reparaci6n de las construcciones con FRP.
PLASTIC for the construction of fishing craft is
usually fibreglass reinforced polyester (FRP) and
manufactured from two components, plastic poly-
ester resin and a reinforcement of glass fibre. Although
other plastics (i.e. Epoxide resin) are worth attention,
the current high price of Epoxide makes its use pro-
hibitive for fishing vessels and most other craft.
Very soon after the initial attempt of the various ship-
yards and manufacturers to use FRP in 1954, it was
realized that more research was required in two fields.
Basic material and its use
In the Netherlands this was largely carried out by the
Plastics Research Institute of Delft which played a major
part in research and the training of personnel.
Construction in FRP
The economical use of FRP for boat construction can
only be achieved if the designer fully appreciates that the
vessel is to be an FRP construction. The various strength
characteristics that can be achieved must be utilized and
the various materials forthcoming. Hence close co-
operation between the Research Institute and the
Technical University of Delft Shipbuilding Department
was set up.
Governmental co-operation
At about the same time, when the initial results looked
promising, the Netherlands Government, and especially
the Navy, entered into the operation and a great number
of naval vessels were built. This, in turn, enabled a
great quantity of data and experience to be acquired.
Pilot vessels of 78 ft (23.40 m) were built and proved
successful.
International co-operation
Gradually international co-operation has been built up
with firms in Japan, Hong Kong and Israel. This has
avoided duplication of research and development
already carried out elsewhere. In principle, also, this has
led to agreement, based on experience gained in the
Netherlands, to develop and build fishing vessels con-
structed in this medium. In 1962, an International Board
to consider "Synthetic Materials for Shipbuilding" was
set up, and this Board reported to the International Ship
Structural Congress (ISSC) in July 1964.
TYPES OF FRP
There are various compositions for glass fibre reinforce-
ment, such as mat, woven roving, glass fabrics, surfacing
tissue and unidirectional materials (fig 1). Only mat,
woven roving and unidirectional materials will be con-
sidered here.
The mechanical qualities of FRP are determined by
the type as well as the amount of glass reinforcement
used. Some possibilities are given in table 1. By using
different combinations of amount and type of reinforce-
[270]
TABLE 1 : Various types of FRP
Glass reinforcement
Mat ....
Woven roving .
Unidirectional .
Glass %
28
45
50
Tensile strength
Win* kg/cm3
12,150 (850)
31,000 (2,170)
53,000 (3,710)
Crossbreaking strength
Ib/in* kg/cm*
19,300 (1,350)
31,500 (2,200)
64,000 (4,480)
E modulus
Ib/in* kg/cm*
1,070,000 (75,000)
1,500,000 (105,000)
3,000,000 (210,000)
ment, the range of mechanical qualities can be large.
The skilled designer can do so to his advantage, using
different combinations of different glass reinforcement in
various parts of one particular boat.
Fig 1. Types of glass reinforcements
PRINCIPLE OF COMPARISON OF
MECHANICAL CHARACTERISTICS
The incorrect method
A comparison of strength to specific gravity is shown in
table 2. The following statement was added to this table:
"From this table it appears that FRP has the highest
TABLE 2: Comparison of strength to specific gravity
Material
Specific strength
Wood (Dry)
FRP
Aluminium
Steel
7.5
0.75
29
1.5
32.5
2.5
65
«=101b/inaxI08
-19.4
-13
Specific strength^
I
Fig 2. Beam submitted to tensile force P
,p
Fig 3. Beam submitted to bending force P
,P
direction of gram
Fig 4. Wooden plate supported at right angle to grain
,P
direction of grain
Fig 5. Wooden plate supported parallel to grain
Criterion for tensile strength
If a beam (fig 2) with unit width and thickness H is
subjected to a tensile force Ft, then the tensile stress <?,
equals FJH. Beams of different materials are of equal
weight if their thickness, //, varies in inverse ratio to their
specific gravity. Therefore, the maximum tensile force
which beams of equal weight but of different materials
can withstand is dependent on the ratio :
Criterion for bending strength
The beam in fig 3 with unit width and thickness H is now
subjected to a bending force /v This results in a bending
stress :
ah = M ; M =s %Fbl = bending moment
W = %H2 = modulus of section
specific strength". This statement is rather bold and it is
an oversimplification to such an extent that it becomes
partially incorrect. To get a correct insight into the
qualities of various materials, we must clearly separate
tensile strength, bending strength and rigidity.
[271]
Analogous to 2, the maximum bending force which
beams of equal weight can withstand is dependent on
the ratio:
TABLE 3: FRP versus steel and aluminium as regards strength and stiffness
FRPmat(2S%)
FRP woven roving (45 %)
Shipbuilding steel
Aluminium (MMgl)
lb/in2 (kg/cm2)
lb/in2 (kg/cm2)
lb/in2 (kg/cm2)
lb/in2 (kg/cm2)
Specific gravity .
Tensile strength .
Y 1.5
a, 12,150 (850)
1.6
31,000 (2,170)
7.8
64,000 (4,500)
2.65
38,000 (2,660)
Crossbreaking strength
aB 19,300 (1,350)
31,500 (2,200)
64,000 (4,500)
38,000 (2,660)
Modulus (Bending) E
1,070,000 (75,000)
1,500,000 (105,000)
30,000,000 (2.1xlOfl)
10,000,000 (700,000)
crry1
8,100 (566)
19,350 (1,363)
8,200 (578)
14,350 (1,011)
<TB y~2
8,580 (600)
12,250 (863)
1,050 (74)
5,410 (381)
Ey3 ...
318,000 (22,250)
361,000 (25,432)
63,200 (4,452)
538,000 (37,900)
<TJ y"1 x 102 x 6,920" l
100
241
102
179
<rBy-2xlOax7,100-1 .
100
144
13
64
Ey~3xlOaxl87,000-1
100
114
20
170
Criterion for rigidity
Apart from strength, we must consider stiffness. It may
happen that a beam (fig 3) bends so much under a force
Fb that the deflection, a, surpasses acceptable values,
although the bending stress ab may stay within normal
limits. Therefore, stiffness and strength must be dealt
with separately. The deflection, a, depends on the ratio
Fb/EI where £= modulus of elasticity, and 7= moment
of inertia =TV A3.
Analogous to 2 again, the bending force which causes
beams of equal weight to deflect equally depends on
the ratio :
£
COMPARISON OF FRP WITH STEEL AND LIGHT
ALLOY AS REGARDS STRENGTH AND RIGIDITY
In table 3, FRP, both with mat and with woven roving
as reinforcement, is compared with steel and light alloy
on the basis of equal weight and using the three criteria
found above. With FRP mat as a basis, it follows :
FRP-woven roving is stronger than aluminium,
FRP-mat and steel
FRP-woven roving is more rigid than FRP-mat and
steel
Aluminium is more rigid than FRP-woven roving,
FRP-mat and steel.
Summary of criterion
For a given weight :
tensile strength proportional to ~f
bending strength proportional to ^f
E
rigidity proportional to -3
COMPARISON OF FRP WITH WOOD AS
REGARDS STRENGTH AND RIGIDITY
General
Whereas comparison of the mechanical qualities of
FRP with those of steel and aluminium was rather simple,
a comparison of FRP with wood is more difficult. This is
because of the following:
• Variations in mechanical qualities of various
samples of the same wood can differ greatly
• The mechanical qualities of wood are greatly
affected by the moisture content
TABLE 4: FRP versus wood as regards strength and stiffness
Specific gravity
Tensile strength
Crossbreaking strength
Modulus (Bending) E
Ey-8 . . .
a,y-1xl(Px6f92D-1
FRP mat
lb/in2
(kg/cm2)
1.5
12,150
(850)
19,300
(1,350)
1,070,000
(75,000)
8,100
(566)
8,580
(600)
318,000
(22,250)
100
100
100
FRP woven
roving
Ib/in2
(kg/cm2)
1.6
31,000
(2,170)
31,500
(2,200)
1,500,000
(105,000)
19,350
(1,363)
12,250
(863)
361,000
(25,432)
241
144
114
Oak
lb/in2
(kg/cm2)
0.85
6,700
(472)
6,700
(472)
1,210,000
(85,240)
7,900
(557)
9,300
(655)
1,980,000
(135,264)
99
109
630
Teak
lb/in2
(kg/cm2)
0.85
9,300
(655)
9,300
(655)
1,170,000
(82,427)
10,950
(771)
12,900
(881)
1,920,000
(135,264)
135
69
610
Fir
lb/in2
(kg/cm2)
0.55
6,800
(479)
6,800
(479)
1,040,000
(73,268)
12,400
(874)
22,500
(1,585)
5,900,000
(415,655)
154
264
1,865
lb/in2
(kg/cm2)
0.85
6,300
(443)
6,300
(443)
1,410,000
(99,334)
7,400
(521)
8,750
(616)
2,310,000
(162,740)
92
103
730
[272]
• A wooden boat is not a homogenous structure,
but consists of a great number of parts held to-
gether by frames and fastenings. These fastenings
cause weak spots in the structure
Therefore, a comparison on the basis of laboratory-
selected samples of wood bears little relation to the
characteristics of the complete wood enstructure in the
boat. Nevertheless, an attempt is made to compare FRP-
mat and FRP-woven roving with oak, teak, fir and pitch
pine (table 4). The mechanical qualities of the wood are
those for wet wood, taken along the direction of the
grain, i.e. for wooden beams, supported and loaded as
in fig 4.
An investigation of the characteristics of wooden
beams, supported as in fig 5, will give much lower values
and should be considered when analysing table 4.
Conclusions from table 4
Using the same criteria as outlined previously, the con-
clusions are:
On the basis of equal weight, wood (in wet condition
tested as in fig 4) is much more rigid than FRP and also
stronger than FRP-mat. However, FRP-woven roving is
stronger than wood.
Fig 6. Drop test with FRP lifeboat
Practical examples of FRP compared with wood
The comparison of the various materials as given in
tables 3, 4 and 5 is based on a comparison of beams out
of the different materials.
• It is difficult, if not impossible, to compare FRP
with wood solely on the basis of the tables show-
ing mechanical characteristics, but rather with
actual experience with wooden and FRP boats,
Fig 7. Pram type motor launch
which have stood up in practice, and have been
built lighter than comparable wooden craft and
with good results. Some examples may illustrate
this
• Tn many countries, ships' lifeboats made of FRP
have almost completely replaced former wooden,
steel and aluminium boats. These FRP boats are
lighter than the others, yet they are strong
enough (perhaps even too strong) for their pur-
pose. Only FRP lifeboats have to pass rigorous
tests, amongst these a drop test, illustrated in
fig 6. It is unthinkable that wooden lifeboats
would survive such treatment
• Fig 7 shows a pram-type motor launch entirely in
FRP with both mat and woven roving as reinforce-
ment. The hull itself is about 40 per cent lighter
than if made in wood
The FRP boat is stronger. In a test report, issued by
police authorities after testing the prototype for some
months, it was said :
". . . in shallow water, on several occasions sand and
stone bottoms were hit and the boat suffered no damage.
Even when running full speed and with the ebb-tide the
boat ran aground on a stone jetty below the water sur-
face which brought the boat to a sudden stop. The
damage done was some scratches on the hull and a
dented bilge keel. Once the boat was jammed between a
bigger vessel and a mooring post which led one to
expect that everything would be crushed; however, after
the pressure was released, the boat returned to her old
shape. If this had happened to a wooden craft, it would
have been irreparably damaged, whilst a steel boat
would have been dented severely."
Another proof of superiority of FRP over wooden
boats can be found in the military field. A great number
of armies are replacing or have replaced their wooden
storm and assault boats by FRP boats. These boats can
be made not only lighter for the strength required but
have lower maintenance and repair costs.
FRP SANDWICH CONSTRUCTION
General
When comparing FRP with aluminium, but more especi-
ally wood, it was found that although FRP was stronger,
it was less stiff. This can be overcome by adopting a
sandwich-type of construction. The principle of this is
illustrated in fig 8. The inner and outer skins are held
apart by a core of light-weight material. For this, PVC-
foam has been used with success in a great many cases.
For FRP fishing craft, the rule is:
outer skin 0.3 times core thickness
inner skin 0.2 times core thickness
In theory the skins can be much thinner, but they
become so vulnerable that they have little practical value.
Influence of mechanical characteristics
For the sandwich in fig 8, with facings of woven roving
with specific gravity, 1.6 and PVC-foam core with
specific gravity, 0.08, we find an overall specific gravity of
0.59.
[273]
a
Ffc *. Sandwich FRP
So the sandwich with total thickness 1.5 AT has the
same weight as a solid FRP laminate with a thickness
= 1.5 #x 0.59/1. 6= 0.55 #. When calculating the mo-
ment of resistance and the moment of inertia for both the
sandwich and the solid laminate, we find :
ratio sandwich: solid of modulus of section:
0.224 H2
0.05 H2
= 4.5
ratio sandwich: solid moment of inertia:
0.190 H*--
However, the bending strength of the sandwich as
well as the modulus of elasticity are lower than those
found for the solid laminate. For the sandwich in
question we find :
6£= 15,700 lb/in2 (1,100 kg/cm2)
£=1,145,000 lb/in2 (80,000 kg/cm2)
Therefore the
strength sandwich FRP 15,700
strength solid FRP =! " * 3 1,500
Rigidity of sandwich FRP , «3 6 1,145,000
Rigidity of solid FRP " " 1, 500,000"
Translating this into the criteria used in tables 3 and 4
we obtain table 5.
• The handling characteristics of beach-landing craft
are mainly governed by the weight of the boat.
Above a certain weight limit, it is impossible to
handle a boat alone or with two people. For a
given total weight, therefore, a boat made out of a
material with a high strength : weight ratio can be
larger
• It requires less power for the same speed to
propel a lighter vessel, and therefore either speed
may be increased or power reduced
On the other hand, it is not necessary for a boat to
be heavy in order to be stable and to have good sea*
keeping qualities.
In a report by the Towing Tank in Hamburg (MGckel,
1963), it was clearly proved that in comparing the
stability of wooden pilot boats and FRP pilot boats, the
lighter FRP boats were just as stable. Of course, and
this is very important, the designer of FRP boats should
take into account the influence on weight of the con-
struction material, which he selects when determining
length, beam, depth and freeboard as well when design-
ing the linesplan of the boat in question.
IMPACT
All wooden construction boats are rather easily damaged
by impact forces; steel and more especially aluminium
get severely dented or even damaged by impact forces.
Steel and aluminium are moreover weakened considerably
by notches or scratches. FRP, on the other hand, shows
excellent impact resistance, with FRP-woven roving by
far the best. Moreover the impact resistance values are
only slightly reduced by notches. This is of great practical
value. Not only will a FRP boat be able to withstand
rought treatment, but also a crack once started will not
continue easily as is the case with steel and aluminium.
CONCLUSION
From table 5 it is clear that the FRP sandwich is the best
as regards mechanical qualities.
INFLUENCE OF WEIGHT
In the foregoing great stress has been laid on selecting a
construction material with favourable relation of strength
and stiffness for weight. It was found that FRP fulfils
these requirements best. Weight is so important because
of the following reasons:
• If a boat is heavy, then much material must be
handled during construction which increases
building costs
FATIGUE
All of the materials mentioned in this paper show
reduction in strength if submitted for a prolonged time
to alternating or constant forces. Both wood and FRP
show fatigue strength after 10 million cycles of around
25 to 30 per cent of the static strength; aluminium is the
same or even less good than FRP. Steel is slightly better in
this respect, since it retains about 40 per cent of its
strength.
For FRP sandwich constructions, a PVC-foam core
may be severely weakened in case of high temperatures
and is especially the case with horizontal surfaces like
decks, when other core materials should be considered.
Criteria
Tensile strength
Crossbreaking strength
Stiffness
TABLE 5 : FRP versus other materials at equal weight
100
100
100
FRP woven FRP
roving sandwich
241 218
144 320
114 1,190
Steel Aluminium Oak
102
13
20
179
64
170
99
109
630
Teak
135
69
610
Fir
154
264
1,865
Pitch
pine
92
103
730
[274]
CORROSION RESISTANCE
Steel
Under salt-water conditions, steel needs continuous and
excellent protection to prevent rapid corrosion. Some
woods, especially those containing acids, such as oak and
Douglas fir, may have a severe corrosive influence on
steel.
Aluminium
Aluminium shows quite different results, depending on
the type of alloy used. Some alloys show little or no
corrosion in sea water. However, aluminium remains a
difficult material as regards corrosion and may give quite
unexpected results. If wood, treated with preservatives
containing copper, comes into contact with aluminium,
this will lead to rapid corrosion. Also many antifouling
paints have a disastrous effect on aluminium. Ships' life-
boats have been corroded completely where supported
by leather-covered chocks.
Wood
With the exception of teak, all wood should be protected
by proper painting to prevent rot and decay.
FRP
FRP is not affected by sea-water, provided proper raw
materials of boat-building quality have been used and
have been handled with the necessary knowledge and
care.
DURABILITY AND MAINTENANCE
One of the main advantages of FRP over any other
material mentioned above is that it is durable, if made
properly, even if unattended and without maintenance,
except perhaps for a regular coat of antifouling paint.
There are several examples demonstrating this long-
term durability. In a report regarding three U.S. Coast
Guard boats (Cobb, 1962) results of inspection of these
ten-year-old boats were most encouraging. Neither sea-
water (heavily polluted in this case) nor leak oil and dirt
on the inside had had any measurable effect on the
laminate. Especially important was that the maintenance
costs for these craft had been 80 per cent less than for
comparable steel craft.
The U.S. Buships report (Alfers-Graner, 1960) on the
superstructure of a U.S. submarine. After having been
used for more than five years, the flexural strength was
still 88 per cent and the flexural modulus 91 per cent of
the original values. There was no change in hardness.
FRP mat .
FRP woven roving
PVC-foam.
Steel
Aluminium
Oak
Teak
Fir
Pitch pine
TABLE 6: Heat conductivity
BTUIfilft*lhrl°F
0.10
0.12
0.03
40
140
0.14
0.14
0.09
0.14
Kg cal/m/m^/hrfC
0.06
0.08
0.02
26.87
94.05
0.09
0.09
0.06
0.09
THERMAL INSULATION
For fishing craft, proper thermal insulation can be an
important requirement. Table 6 shows again that FRP,
especially FRP sandwich, has excellent qualities. An
illustration of the heat-insulating qualities is given in
the aforementioned report (Cobb, 1962). During a
serious tanker fire in the port of Houston, a FRP and a
steel patrol boat were despatched to the scene of the
accident. The crew of the FRP boat were able to operate
closer to the intense heat and for a longer period than
those on the steel boat, because of the low conductivity
of the fibreglass boat. While the topside paint was
scorched, the laminate did not ignite nor was it damaged.
COSTS
Prices of materials
For a fishing craft, especially if made in sandwich, the
excellent thermal insulation of FRP will make it possible
to reduce drastically or leave out extra thermal insulation
layers. This influences building costs favourably.
Prices of materials may vary considerably according
to location. Current prices in the Netherlands arc given
in table 7.
TABLE 7: 1965 prices of materials in the Netherlands
Nettf./ Ih Ij kg Waste % Gross £/lb ijkg
FRP mat . 0.104
0.229
12
0.117
0.258
FRP woven
roving . . 0.122
0.269
14
0.139
0.306
FRP sandwich
PVC 0.185
0.408
14
0.211
0.445
Steel
0.025
0.055
15
0.029
0.064
Aluminiui
n
0.154
0.340
15
0.177
0.390
Oak
0.034
0.075
50
0.051
0.112
Teak
0.137
0.302
50
0.206
0.454
Fir.
0.026
0.057
50
0.039
0.860
Pitch pine
0.036
0.079
50
0.054
0.119
Taking into account, however, the differences in
strength and rigidity of actual vessels, wooden con-
struction is about 40 per cent and steel 100 per cent
heavier than FRP. Table 8 gives an indication of the
actual material costs for boats of different materials.
TABLE 8: Actual material costs for boats of different materials
FRP mat
FRP woven roving
FRP sandwich
Steel
Aluminium
Oak
Teak
Fir .
Pitch pine
100
88
95
37
113
46
175
35
48
Labour costs
The influence of labour costs on the total price of a vessel
is great. Moreover, it is to be expected that this influence
will increase, since almost universally they are increasing
more rapidly than the cost of materials. With FRP,
especially, the labour costs are influenced by several
factors:
[275]
• Number of boats required
• Type of glass reinforcement
• Solid laminate, sandwich, or both
• Degree of mechanization
• Construction details
• Finish required
In many cases the designer can have a great influence
on the actual labour costs and it requires much experience
to design optimum boats in this respect. In view of the
great number of variables, it is impossible to make a
valid comparison of labour costs of FRP with other
materials.
Summary
Material costs of FRP are by no means excessive. Labour
costs of FRP vary greatly depending on design and the
number of boats required. Provided they can be made
in sufficient quantity, experience in different countries
indicates that in many cases FRP boats are not more
expensive, and often cheaper, than boats of other
materials.
REPAIRS
One of the outstanding advantages of FRP is that
repairs can be easily carried out. To illustrate the extent
to which repairs are possible, we refer to fig 9 showing
a 33-ft (10 m) sailing yacht, badly damaged during a
hurricane. The insurance company accepted it as a total
loss on the basis of experience with wooden vessels;
nevertheless, the boat was successfully repaired, as shown
in fig 10, at a price of less than 10 per cent of the original
value.
RANGE OF LENGTH OF VESSELS
FRP is suitable for boats up to at least 120 ft (36.6 m)
in length. Lloyd's Register of Shipping takes this length
as the upper limit in its present rules for construction.
The largest FRP vessels built so far are 77 ft (23.4 m) in
length. They are two pilot-boats (fig 11) built in the
Netherlands. The largest FRP fishing craft to date have
a length of 74 ft (22.6 m). These trawlers were built in
South Africa. FRP can be used certainly for fishing craft
up to 100 tons.
Fig 9. Damaged FRP yacht
Fig 10. Same yacht after repairing
Fig II. FRP pilot vessel "Albatros"
BUILDING POSSIBILITIES OF FRP BOATS
Especially if boats are to be built in quantity, FRP offers
great possibilities to the designer, both as regards appear-
ance and the incorporation of special design features that
influence performance (bulbous bow) without great
increase in the price of the vessel.
Types of moulds
The building of FRP boats always requires a mould.
When a great many boats of the same type are required,
it pays to make the mould in FRP over a wooden
pattern of the boat.
When a sandwich construction is adopted, a FRP
mould can be advantageously used when a large series
is to be built. Should only a small number be required,
rather simple moulds should be considered, consisting
of a number of frames, covered with narrow battens at
regular intervals
Acknowledgment
The co-operation of Prof. Ir. J. H. Krietemeijer of the Delft Tech-
nical University, Department of Shipbuilding; and Mr. L. Taal,
President, Plastic Engineering Co. Ltd., KTB, Amersfoort, Nether-
lands, is gratefully acknowledged.
[276]
The employment of
new and conventional materials in
boatbuilding
BOAT YARD FACILITIES
Reid (Canada): Conveyed his congratulations on Fyson's
paper, and added a few comments for further discussion.
In the case of developing countries a question arises
regarding available or proposed boatbuilding facilities and
whether these should be centrally located or situated around
the coasts in certain strategic locations. As part of a study
Reid had undertaken for the Canadian Government con-
cerning the improvement of fishing boats in certain areas,
one of the major problems that was found was the great lack
of suitable boatbuilding yards of any kind.
The fishermen themselves are excellent boat builders with
a high degree of personal skill and quite capable of producing
the new types of vessel recommended. The problem is that
these fishermen are concentrated in isolated communities,
none of which in themselves could support boatyard facilities
without considerable financial government aid.
The suggested alternative might be the establishment by
the government of small boatbuilding facilities in certain
strategic areas. These facilities should include only the
essential machinery such as bandsaw, circular saw, planer,
power drills, etc. The facilities should be sufficient to handle
all heavy milling, leaving the light work to be done by the
traditional methods. It would be an advantage that a main-
tenance man or instructor should be present to actually
handle such equipment.
There should also be adequate stocks of any material or
equipment not easily obtainable locally.
If standard vessels are to be built, then master templates
for all the heavy members should be available at each loca-
tion, a system found very successful in Newfoundland, where
these problems occur.
Some education system in boatbuilding should be available
to the fishermen, preferably in the off-season period.
Finally Reid advised to use traditional methods of con-
struction that are easily performed by the fishermen building
for themselves. He had some reservations about the wide
application of glued laminate construction which may be
difficult to control under adverse conditions in heat and
humidity that prevail in many developing countries.
Methods of improvement?
Rasmussen (Denmark): Congratulated Fyson on an excellent
paper. It is very seldom one sees this comprehensive subject
treated so concisely and at the same time so completely.
On the subject of steambent frames versus laminated frames:
what in Fyson's opinion would be the best course to take in
an area where the old double-sawn frame system is about to
be discarded in favour either of steambent or laminated
frames?
It appears that the technique of steambent heavy stock,
for example 3 x4 in (75 x 100 mm) or more, is a difficult one.
More details on glue types would be welcome. Has Fyson
any experience on use of epoxy glues in comparison with the
more well-known glues on the phenol-resorcinal and the
resorcinal types. This question is specially related to the
necessary pressure needed.
O'Connor (Ireland): Congratulated Fyson on a paper which
does present a very good blueprint for development of boat-
yards in those countries which are endeavouring to improve
their fishing craft.
The boatyards operated by the Irish Sea Fisheries Board
have in operation a section control system such as Fyson
suggests and it is found very satisfactory and can be re-
commended, provided the supply of materials for each
section is efficiently organized.
One notable omission in Fyson's paper is some advice on
the storage and installation of the boat machinery. With the
long delivery times nowadays quoted by engine and machinery
makers and the probable transport delays which might be
experienced in the case of deliveries to countries without
their own engine manufacturing concerns and, even in the
case of some which have, it is a wise operator who makes
provision for any such delays and therefore some advice on
machinery storage would be welcome to readers.
There is no mention either of the necessity for the equipping
and manning of a fitters shop to take care of the machinery
installation and repair work. O'Connor suggested that some
of Fyson's engineer colleagues might well add their advice on
this important point for the benefit of developing countries.
These additions would make this paper a comprehensive
document.
Problem of using FRP
Verweij (Netherlands): Fyson's remarks that for series pro-
duction co-operation between the builders and an experienced
naval architect is essential, equally holds when one considers
building of boats in FRP.
The naval architect then should have a thorough knowledge
of the theoretical and practical problems of designing and
building FRP boats.
Verweij differed with Fyson as regards the usefulness of a
mixed plywood reinforced plastics construction for small
craft. .
Vcrweij's objections against such a mixed construction is that
in the long run these two different materials can be separated
from each other by water penetration. Especially for open
fishing craft which will always have water on the inside of
the hull, this composite construction will give rise to troubles.
It is better to rely on either a whole wooden or a whole
fibreglass construction.
Where Fyson proposes the use of aluminium deckhouses
on steel vessels, in order to save weight, corrosion must be
feared. Certainly, it can be done, but one has to be very
careful.
Moreover, there is a great difference in thermal expansion
between steel and aluminium, with aluminium expanding
twice as much. Fibreglass, however, shows the same expan-
sion as steel and presents no corrosion difficulties.
[277]
Experience in India
Devara (India): Fyson did a splendid job in covering all
aspects of boatyard facilities, organization and running of it.
It richly deserves congratulations.
A few observations first by explaining the experiments
made in India might be interesting. A boatyard was started
in Kakinada (Andhra Pradesh) in 1959 with a production
target of 5 boats (30 ft or 9 m and below). There were only a
few hand tools. Later on a few power tools were added.
During the second year, with a view to improving the rate
of production, the workers were formed into two groups to
build an equal number of boats. They were encouraged to
compete with each other in early completion of the boats.
This worked well in the beginning, but failed later on, as
there was no incentive (say by way of bonus) for the boat-
builders who did the job in a shorter time. Later on, they
were grouped according to their skills and were allowed to
do repeat jobs, e.g. one group in charge of keel assembly
and the next in planking off and so on. This worked very well
since it was coupled with increase of wages for whoever
showed better efficiency in completing the same jobs.
From 1961, all materials were purchased in bulk by calling
all-India tenders, and after having properly estimated the
yearly requirements.
By these steps and close and constant expansion and
guidance, the efficiency of the boatyard was improved. This
boatyard is well known for producing teakwood (tectona
grandis) boats at a far cheaper price compared to other
parts of India, e.g. 30 ft (9 m) boats in teakwood are priced
at £650 ($1,800), whereas the prices in other yards are £1,000
to £1,150 ($2,800 to $3,200) though built with non-teakwood.
A few words to the participants from developing countries:
• Please do not over-mechanize the boatyard, but use
the full manpower available, so as to provide greater
employment and also to reduce high overheads due to
costly machinery
• Give good training to boatbuilders in all aspects,
including using small power tools and time-saving jigs
• Have constant and close supervision — which often
results in finding out ways and means of economizing
the number of operations and cutting down wastage
• Proper planning of production programme, pro-
curement of materials, utilization of the specialized
skills of workers and close supervision of the boatyard
can result in efficient and economical running
McNeely (USA): Fyson's paper will be of inestimable value
in the establishment of sorely needed shore facilities in
developing countries.
Australian experience with bent frames
Swinfield (Australia): With reference to Fyson's paper re
"plank templates", it is submitted that the "old fashioned"
half model (of as large a scale as practical) holds many
virtues even today including that of "plank layout".
It is not necessary to spile every plank and if the "scaling
method*' of plank layout is used between, say the garboard
and the bilge plank and the bilge plank and sheer plank,
then most other planks can be bent around and "set" from
the work bench direct on to the moulds. This of course does
not include "stealers". If the designed shape of the boat
precludes using the "scaling method" of plank layout then
the design of the deck frame and the design of the stem could
usually be so arranged that planking becomes relatively
simple. Because "planking" itself is usually vulnerable to
misadventure and "teredo" it should always be easy to
remove and replace any plank.
Referring to the selection of stock Swinfield emphasized
that all timber should be sawn with the grain running parallel
with the face of the bent frame. Fyson quoted a limiting
radius of four times the thickness for bending. This seems
remarkably small and probably accounts for many broken
frames in the "after life" of some vessels. Swinfield recalled
an unusually high proportion of broken frames in fishing
vessels with deep heels and in "metre class" yachts with very
deep heels. The practice of bending any timber to such excess
should be discouraged. If such is necessary it is much better
to "deep cut" the end of the frame, subjected to the excessive
bending, and so "laminate" the otherwise over-stressed timber
or frame.
It might be mentioned that the method of fastening the
planking to or through the bent frame should always be very
carefully considered in the light of the dimensions and species
of timber used in the frame.
A solid (one piece) bent frame can usually be through
fastened with a "turned" or clenched copper nail; it is not
absolutely necessary to roove such a frame. A light frame or
one that is composed of two laminations does not always
take kindly to such a procedure and invariably splits between
the clenched fastenings. It is suggested that a fully rooved
frame is necessary in an extreme case or an alternate arrange-
ment of rooves and clenched nails be used.
Swinfield referred to bent frames steambent around
ribbands which "run around" the vessel from mould to mould
or bent frames that are bent inside ribbands, garboards and
sheer strakes. Frames bent away from the vessel and left to
cool for machining are rarely used in Australia. The limiting
dimensions of steambent "hardwood" frames would be
about 3J x 3 in (82 x 76 mm) in two laminations. Glue is not
used in such construction and copper through-fastenings are
invariably used. In all cases it is essential to paint the faying
surfaces of all frames before applying the planking to avoid
rot in the years to come.
UK methods listed
Lee (UK): Fyson is to be given full support in his warning
that the establishment of a new yard or the re-equipping of
an old one for the series production of boats requires a
careful study of the possible demand.
The following comments reflect experience in UK:
Air drying: Most boatyards find it better to obtain prepared
material from timber merchants than to undertake extensive
air-drying in the boatyard.
Series production: In the building of large craft it is useful to
have a platform at deck level on which light wood-working
machinery is mounted. This enables the workmen to cut and
prepare the timber without wasting time going down the
scaffolding and to the mill.
Marine railways: Railways impose a restriction on movement
whereas greasy ways on wood or metal runners enable boats
to be moved with greater freedom. The space available can
be used to much greater advantage particularly when there
is a variety of types of boat. There is no necessity for points,
etc.
Portable machinery: Portable electric saws have proved very
useful as they can cut heavy timber without it being moved
to a fixed circular saw, which would be expensive on labour.
When the timber has been cut substantially to shape it is
lighter and easier to handle.
Apprentices: Most boatyards find that although they have an
extensive training programme, after they are trained the
apprentices are lost to other industries.
[278]
Boiling better than steaming
Colvin (USA): Fyson's paper gives a good synopsis of the
small wooden boatyard. More stress should be made on
detailed lofting, regardless of the fact that it is a one-off
building. Experience has always been that the more detailed
the lofting, the less labour involved in the later stages of the
construction.
It is becoming more difficult every year to obtain good
steam-bending stock. However, it has been found that
boiling rather than steaming gives a more supple timber with
which to work and does not have the tendency to dry out the
wood as does steaming. Also, soap and kerosene is added to
the water which eases the bending as well as gives a pre-
servative action. Tn the heavier frames, rather than bend
over a form, Colvin normally bends a frame to | molding
full siding, forming the two of them simultaneously and
riveting the two. Rather than use the pheno-resorcinol-
formaldehydc adhesives, they are using epoxies with seem-
ingly better results. They do cure at low temperatures and are
easier to spread.
Unless the yard was well-planned in the beginning, there
is little that can be done to arrange the buildings in an
orderly fashion to have a more or less continuous flow of
material. Most yards have been expanded as necessity
demanded; and, with the changes in technology and con-
struction, and the availability of smaller tools and more
efficient means of handling timber, the expansion has not
necessarily been correct. One of the most difficult aspects of
wooden boat construction is the necessity of having a great
deal of capital invested in timber that is just drying. It has been
found that carefully controlled dry kilns produce equally as
good timber for boatbuilding perhaps as air-dried stock,
which permits the yard to invest its capital in other things
than timber. The cost of air-drying is becoming prohibitive
in that ideally it should be turned at least once during drying
and then baulked during the final stages where the straight-
ness and all can be controlled to a nicety. The availability of
large timbers in soft woods, i.e. Douglas fir, has altered the
methods of building on the Chesapeake Bay, where hard
woods are very difficult to obtain in any length or of good
quality.
Technical equipment needed
The type of railway is dictated more by whether it is a
building yard or a repair yard, or both. In Colvin's own yard,
where they are primarily engaged in new construction, only
launching ways are used and they have no railway as such.
They find that steel cradles are best for launching on all types
of boats from the smallest to the largest as they do not have
to worry about their floating up under the hulls. With the
larger vessels and the extremely heavy cradles, they secure
the cradle to the hull during launching and then drop the
cradle after the vessel is afloat alongside a crane, retrieving
it and then greasing it ready for the next launching. For very
small craft under four tons displacement, launching is via a
crawler crane. They found a crawler crane to be an excellent
investment in comparison to derricks and sheerlegs as it
allows the installation of engines, the raising of spars and
lifting heavy loads any place in the yard, including heavy
keel timbers. It also can be used for pile driving and dredging,
and can be barge-mounted for light salvage work. All in all,
it becomes a very versatile and useful machine.
With the advent of lighter and more powerful electric
engines, the portable machinery has in many instances
replaced the fixed machinery, especially in the interior joiner
work, decks and cabin work.
Fyson is absolutely correct, and it should be stressed, that
light machinery doing heavy work is expensive in time and
tools. This is a common fault with many small yards where
the owners are endeavouring to save a few dollars and end
up spending three times as much as one heavy-duty tool
would have cost.
It is no doubt desirable to use the system proposed by
Christensen in the itemization of construction. In theory,
such a cost analysis is highly desirable, but in practice it
becomes very difficult and an unwieldy system— unless the
yard is very large and can afford the additional labour
necessary to keep track of the book-keeping. A
slightly simpler system is to use the main headings
— i.e., backbone, framing, etc. as items, but add the total
fastenings as an item, total paint as an item, etc. as these are
purchased from independent suppliers, and billing is very
easily posted. After the vessel is completed, a cost per unit
weight of planking, or a cost per unit weight of displacement,
or per ton, or any other convenient method can be used to
determine the cost. For a larger vessel, the increase in
machinery can be directly figured based on machinery costs
as can the equipment, Item 12.
The establishment of a small yard, while it does depend on
the demand for new vessels, also depends a great deal on
the reputation and the ability of those operating the yard.
A well-established yard in USA will sell their vessels not only
several hundred miles but several thousand miles from its
location, and in many instances, export their vessels, so the
yard location of necessity need not be in the middle of the
demand area, but in an area that is accessible to materials,
labour and transportation.
Training of personnel
The undertaking of training of personnel is one of the
most difficult areas of operation unless the yard is established
in a long-time boatbuilding centre. It seems that it is almost
as easy and as fast to train personnel from the beginning
rather than try and adapt a house carpenter to boatbuilding
or a professional cabinetmaker to interior joiner work. Their
preconceived ideas are often the biggest bottleneck in produc-
tion. In many of the high schools in USA, there are shop
courses, and an enterprising employee will usually be found
utilizing these facilities. In USA, it is very difficult to indenture
apprentices, and individual state requirements are such that
schooling must be made available to children until they reach
a certain age, so that unless the enterprise is very large the
cost of employing apprentices with their required school-
ing is prohibitive. Also, the four or five years that are required
to elevate one to journeyman at low initial pay causes most
people to go into other industries which offer higher pay to
begin with, even though there might be little future in the
work. It is perhaps true that, worldwide, one of the most
difficult aspects of wooden boat construction is the training
of the future builders.
Training in developing countries
Heath (Zambia): Fyson invited discussion on training in
developing countries. For the interest of those considering
setting up a boatbuilding programme in wood construction
the following points might be worth noting.
A minimum period of 4 years experience as a carpenter has
been necessary for a trainee boatbuilder, a 12 month course
will produce a man suitable for employment as a helper to a
more experienced boatbuilder. It has also been found that it
is not necessary or desirable to train boatbuilders as in a
school i.e. with theory and basic joints, etc. A year working
more as an apprentice gives better results and is productive
if a building programme is in progress.
It is appreciated that in a case where no boatbuilders exist
at present it will be necessary to start as a school, this was
[279]
done in Zambia, but after three years it was found the school
was able to switch to production. Over a five year period from
scratch, 60 boatbuilders were trained. The boat types taught
and built varied from dories to open motor fishing boats of
26 ft (8 m) LOA both carvel, clinker and marine plywood
constructions were used.
The greatest importance is "follow up" after training, in-
cluding provision of boatbuilding materials and loan schemes
for fishermen, to purchase the boats built by the ex-trainees.
If these last points are not taken into consideration, at the
outset of promoting an improved boat scheme for fishermen,
the whole project will almost certainly fail.
Author's Reply
Fyson (FAO): Thanked Reid for his interesting comments
which were certainly relevant to the earlier stages of boatyard
development. His suggestions for the use of master tem-
plates is a good one and Fyson added by way of example
that in Senegal, where he was responsible for boatbuilder
training, they are in fact doing this. Trainees from the course
form co-operatives at the end of their training period to build
42 and 52ft (13 and 16m) fishing boats. For this purpose,
they will have the use of master templates made up in plywood.
On the question of the use of laminated or steambent
frames to replace sawn frames, as mentioned by several of
the contributors, Fyson considered that the choice is depend-
ent on factors which vary from country to country, such as
the experience and skill of boatbuilders and the availability
of suitable timber for steambending. Where skills have been
sufficiently well established in traditional methods, and close
and careful supervision of the correct use of glue and clamping
techniques is available, lamination can be successful, and
Fyson gave as examples Ghana and Nigeria, where lamina-
tion techniques are being successfully used. A further factor
in making this decision is the question of cost. Given the
availability of suitable timber for steambending, then lamina-
tion will definitely be more expensive.
Fyson agreed with Verweij on the difficulty of coating
planked hulls with fibreglass. However, there is another use
of fibreglass, of which Fyson had some experience, in the
construction of small hard chine plywood boats, less skilled
labour can be used and costs cut by the use of fibreglass tape
to seal the keel and chine joints.
Epoxy glues are very sensitive to humidity and for this
reason Fyson did not recommend their use in tropical
countries.
The idea of laminated frames constructed in a central
workshop to be distributed to smaller yards is interesting, but
would probably be impractical unless the boatyards were
situated close together.
To Verweij, Fyson said that in most developing countries,
wood is locally available, while steel and plastics must be
imported. Therefore, because of exchange controls and
currency problems, wood is liable to be the dominant material
for some time to come.
WOOD IN FISHING VESSELS
Potter (USA): Simpson's (1960) proposals were used in his
design office for the design of about 12 wooden fishing
vessels ranging in size from 72 to 125 ft (22 to 38 m) LOA.
Some of these were built exactly to the scantling rules and
some departed from them to conform more closely to general
practice. Potter, having succeeded the late Simpson, had
revised his scantling figures.
Table 30 of Simpson's paper shows the smallest vessel, 68 ft
(20.75 m) to be of heavier construction than the proposed
scantling rule would require. The 85 ft (25.9 m) LOA vessel
is built in many respects of scantlings equal to the proposed
rule, and the largest vessel, 115.86ft (35.3m) LOA is built
quite a bit lighter than the rule would require.
Nine vessels have been used for a re-evaluation, and the
trend of the comparison between actual construction and the
"Suggested Standard Scantlings" shows the same thing as
table 30. Therefore, the key tabulation of table 28, "Standard
Frame Spacing and Plank Thickness" and fig 150 "Section
Moduli of Frames" and fig 151, "Section Moduli of Deck
Beams" have been revised to more nearly conform to actual
contruction practice.
TABLE 1
Standard frame spacing and plank thickness
N Frame Spacing Plank thickness
Inches mm Inches mm
4.00
12
305
H 38
4.25
13
330
1ft 41
4.50
14
356
1] 44
4.75
15
380
H 48
5.00
16
406
2 51
5.25
17
432
2i 54
5.50
18
457
2J 57
5.75
18
457
21 57
6.00
19
483
60
6.25
20
508
2
64
6.50
20
508
2i
67
6.75
21
533
2!
67
7.00
21
533
2;
70
7.25
21
533
2i
70
7.50
22
559
2\
73
7.75
23
584
3 76
8.00
24
610
3 76
The new table 28 "Standard Frame Spacing and Plank
Thickness", here given as table 1 shows a reduction in frame
spacing beginning at N=6.50 and through to the largest si/e
listed, N— 8.00. The maximum frame spacing is reduced
from 26 in (686 mm) to 24 in (610 mm). The plank thickness
is reduced beginning with N = 5.75 and above. The maxi-
mum plank thickness is reduced from 31 in (89 mm) to 3 in
(76 mm).
Fig 1 "Section Moduli of Frames" is Simpson's fig 147 and
shows the original proposed graph line and a new one (dotted)
which approaches the spots indicating values for the nine
vessels investigated.
Fig L Section Moduli of frames
[280]
Fig 2 "Section Moduli of Deck Beams", is Simpson's fig 150
and is treated in the same way. There are two other changes
suggested:
Keelsons: Sided and moulded 4xt, up to LOA -100 ft
(30.5 m)
Sided and moulded 4i x t above LOA= 100 ft (30.5 m)
Sister Keelsons: The original paper says "Not used under
90 to 95 ft (27 to 29 m.) LOA". This should read
"Not used under 80 ft (24 m.) LOA."
7 B
Maximum beam of ship
Fig 2. Section Moduli of deck beams
No other changes seem indicated up to the present. If the
process of scantling design outlined in the original paper is
followed, using the changes shown herewith, it is believed
that the result may be a strong and durable vessel. The reason
for saying "may" instead of "will" is because the best size
for the various pieces of timber is only one factor leading to
strength and durability. The strength qualities of each piece
can vary from excellent to worthless and of course it also
requires certain qualities to help insure durability and long
life. Even with all these factors on the favourable side, the
final result really depends on the skill and knowledge of the
builders. Tight, well made joints and well placed fastenings
well set up can make all the difference between a good vessel
and a poor one.
Practice in USA Northwest
In the Northwest section of USA it has been generally
considered that bent-frame construction is the cheapest and
best in vessel sizes up to about 50ft (15m) length overall.
In vessels of 50 to about 70 ft (15 to 21 m) LOA there have
been some with bent frames and some with sawn frames.
Above 70 ft (21 m) LOA practically all commercial vessels
have been sawn-frame construction.
The reason for use of bent frames in this area is because
good bending oak is available locally, and can be worked in
sizes up to about 3J in (89 mm) square with average ship-
yard skills and a minimum of equipment. Also, there is very
little waste of material if the timber is suitable and well
selected.
When a builder has developed a popular model the same
moulds and ribbands can be used for a number of vessels,
thus reducing the cost, material and time to build. The
basic simplicity of making up the framing of this type, con-
sisting of two bent pieces and a plank floor joining them
over the keel, contrasts with the templating, cutting, fitting,
bevelling and bolting together of perhaps 12 pieces in the
average sawn frame. The bent frame, in sizes up to about
2J in (63 mm) square, can be twisted to the required bevels.
The best bending stock in USA is known as Appalachian
white oak (Qitercus alba) and is found in a broad area inland
in the mountain regions as well as along the sea coast. The
coastal oak was cut off for shipbuilding and other purposes
in the early years of settlement, but second growth timber
has provided enough for boatbuilding needs except during
accelerated building in wartime. In modern times logging
machinery and transport makes this material available to the
shipyard from a very wide region.
This is fortunate because only unseasoned oak from young
trees is suitable for steam bending. Oak which has been
seasoned before bending will very often crack after short
service. In wartime large amounts of oak were shipped to
building yards at a distance, and because it was unseasoned
it checked very badly and a lot of it was wasted.
It might be thought that the use of unseasoned timber in a
boat would be likely to cause rot. However, the steaming
process seems to sterilize the material and it is not common
to find rot in steambent framing.
Problem of bent frames
At times yachts built in Europe have been delivered to USA
in which many of the steambent frames suffered brittle
fractures. One vessel which Potter had surveyed, only two or
three years old, had over fifty broken frames. He had often
wondered whether the European oak (Quercus robur) is
suitable for steam bending, or whether the examples of
brittleness which have come to his attention are because
these frames were bent of seasoned timber.
Each boatbuilder of experience will have developed some
little variations on the usual methods of steambent framing,
but the basic system is as follows :
Frames to be bent in place. From the loft layout, forms of
braced planking are made to the inside of plank and set up
on the keel. Ribbands or stringers (of spruce, usually) are
fastened to the forms at close intervals, extending from bow to
stern. This constitutes all the preliminary work prior to
bending the frames.
The shipyard may order the frame-stock in log form which
is cut to size in the yard. This is the best arrangement because
the material is not dried out at all before use and also the
yard has full control of the cutting. If the timber supplier is
local and co-operative the frame stock may be ordered in
quarter-sawed flitches, ready for the yard to complete the
sawing and planing.
One of the benefits of a square frame— that is, siding and
moulding equal— is that the individual pieces can be turned
to put the flat of the grain parallel to the planking, which is
the easiest to bend and does not tend to split from plank
fastenings.
The milled framestock is then placed in a steam box where
it is steamed until pliable enough, usually one hour per inch
(2.5cm) of thickness. A three inch (7.5cm) thick frame
should steam for three hours. This is where the judgment of
experience makes a great difference. The man in charge of
the steaming must keep tally of the frames in the box and if
he is capable, the number of broken frames will be much
reduced.
The steam box is usually a long watertight box with a
[281
removable opening at one end through which the frames are
inserted and removed. There are sometimes racks to support
the frames and insure complete exposure, but often the
frames just float in water allowed to stand about half-depth
of the box. Most shipyards have a wood-fired steam boiler,
using scrap wood for fuel, and the steam is introduced into
the box at several points along its length and directly into
the water. One yard used a discarded torpedo tube for a
steam box, and also introduced a small proportion of kerosene
into the steam bath.
When steamed long enough, the frame is removed from
the steam box and as quickly as possible is passed over the
top of the ribbands and bent into place against them. The
crew doing this work must be quick to keep the frame from
cooling. A series of bar or C-clamps are used to pull the
frame tightly against the ribbands. At the top a sort of
wrench is applied to twist the frame to the correct bevel.
Usually a few blows of a mallet or heavy hammer on the
upper end are required to drive the frame heel tightly in place
at the keel.
Method of bending and fitting
Frames to be bent on a form and fitted cold. Equipment
required is a flat bending area with either a heavy plank
flooring or a cast iron grid bending slab such as is used for
bending steel frames. The desired contour is chalked on the
floor or grid and a series of shaped blocks or cleats are
fastened down defining the bend to be made. Here is where
experience counts, because the bend should be a little sharper
than the finished frame, since it will tend to straighten out
while cooling.
The end of the frame at the keel is where the frame stock
is first secured, so usually there are two cleats or blocks on
the bending flat at this point with a space for the frame be-
tween, plus a wedge. At each of the cleats there must be means
of clamping or wedging the frame.
A block and tackle is rigged to hook into a loop of rope at
the upper end of the frame and haul it around from the
straight to the bend required.
Heavy frames tend to fail in bending from compression on
the inner face of the bend and from tension on the outer face
which causes cracks or slivering splits. The compression
failures can be minimized by care in achieving a smooth
bend with no local irregularities and by enough support from
the cleats on the inner face to eliminate localized pressures.
The tension failures can be minimized by use of a steel
strap with a strong square hook at one end. The strap is
made the width of the frame and the hook is of fairly heavy
angles or other shapes, just the right size to fit snugly over the
end of the frame. In use, the hook is fitted to the end of the
frame as soon as it arrives from the steam box and the strap
is pulled tightly against the frame stock and nailed or strongly
clamped to the frame at the end of the strap, the idea being
to prevent stretching the outer fibres of the wood. The
assembly of frame stock and strap is then bent around the
cleats in the usual way. The use of the strap tends to increase
compression within the frame stock and thus requires extra
care to prevent compression failures.
The bending procedure is then as follows:
Frame stock arrives at the bending flat as hot as possible,
strap is attached, heel of frame wedged into the cleats pre-
pared for it, block and tackle attached at the other end,
tackle hauled in steadily, and frame clamped or wedged to
each cleat as frame meets it. All this must be done quickly
but it is very important that it be done smoothly.
Once in shape the frame is allowed to cool briefly and
wooden strips are then nailed across the bend like the chord
of an arc to prevent straightening out, one strip before
removing from the bending flat and the strip on the other side
immediately after. A pair of frames is made from each set of
blocking, or more as may be needed for a group of identical
vessels.
The resulting frame has no bevels, which must be cut from
the material. A case could be made for using the required
frame moulding without regard to the bevels. When beveled
the frame will be undersize compared to the square section
frame, but this will occur gradually as the frame location
approaches the ends of the vessel, where it need not be so
heavy. However, the usual practice is to add the bevel require-
ment to the moulding of the frame. This makes bending
harder and increases the chances of bending failures.
Note that even in construction where the frames are bent
in place against the ribbands, it is usual to "mould" the
bulkhead frames on the flat as described here, thus having a
flat face to the frame.
Fastening of frames
In contrast to a double sawn frame there is no question
that fastenings in a bent frame are more of a problem because
there is much less material to receive the fastenings and
because the fibres are already stretched or compressed to
some degree.
The main difference in the fastenings is that it is not
practical to use drifts because the frame is too light and
springy to take the heavy hammer blows. Even the use of
nails for plank fastenings requires backing up the frame with
a heavy iron to give sufficient inertia. The best fastenings in
smaller sizes are bronze wood screws or copper rivets, and
in larger sizes, through-bolts.
Fortunately, most fastenings into a bent frame are at right
angles to the flat of the grain. The exception is the fastenings
from floors to frames. Very often these are a series of bolts
in a row, each cutting through the same layers of grain of
the wood. Where it is possible, bosom floors should be used
instead of the usual ones on the side of the frames, the
fastenings then being through the flat of the grain.
Some years ago Potter worked on the design of a 60 ft
(18.3 m) wooden vessel which carried a heavy deck load at a
speed of over 20 knots in the open sea. This vessel had a
bent frame construction which was similar to that shown in
fig 3. While there are lot of pieces in this construction they
are light and easy to handle and Potter considered the end
Fig 3. Proposed construction section for 60 ft vessels (beam 16 ft,
depth 8 ft)
[282]
result is a very strong construction with some flexibility. The
outer and inner frame stock and the spacers between the
stringers are all of the same size. Because of the small cross-
section of the frame stock it is easy to bend and may be
easier to procure. Note that the inner frame provides a means
for securing a bulkhead.
Fig 4 shows the scantling section of a small tugboat built in
1948 and still in general service as a contractor's tug. It has
been used in heavy service and still is in excellent condition.
The contractor tried to bend these frames against the ribbands
but found they were too heavy and had to be bent on the
slab, being put into the boat after cooling and "setting".
Potter's comment on Pedersen's paper was to suggest that
more emphasis must be placed on the practical economic
aspects of the use of wood in vessel construction, as it is not
often possible to try for the refinement of structure which the
paper recommends.
He was very interested in the forced drying out and he
enquired whether this caused any adverse effects on the
seams and butts of the ship structure?
Fig 4. Construction sections for diesel powered tugboat (loa 45ft,
maximum beam 1 3.5 ft, depth 6.5 ft)
Norway's use of wood
Ullev&lseter (Norway): In Norway, more than 95 per cent of
the fishing fleet of 40,000 smaller and larger vessels are
wooden vessels. There has not been many essential changes
in the construction and building methods. The knowledge
gained in wood science has not been used to its full extent in
the wooden shipbuilding field. Today's constructional
methods for wooden vessels, make the biological destruction
of the wood a very interesting field of study.
Due to the severe biological destruction in Norwegian
wooden fishing vessels, especially by wood rotting fungi, the
Agricultural College of Norway, Department of Wood
Technology, was in 1958 given the problem by the Directorate
of Fisheries to determine the different biological agencies and
give recommendation for its prevention.
In 1960 Ullevalseter had visited 69 wooden shipbuilding
yards and collected 78 samples of wood from different
vessels attacked by wood rotting fungi. From an earlier
survey, there were 12 samples, so the total collection amounted
to 90 samples.
Besides the wood rotting fungi studies were also made on
damage caused by a wood-destroying insect— Nacerda
melanura and the marine borers Teredo and Limnoria.
The following biological agencies of destruction are
therefore registered :
A. Wood— destroying insect— Nacerda melanura
B. Marine borers- Teredo and Limnoria.
C. Wood rotting fungi.
1 . flasidiomycetes— Wet rot
Coniophora puteana, fig 5
Trametes serialis, fig 6
Lentinus lepideus
Poria sp, fig 7
Polyporus annosus
2. Ascomycetes and Kungi Imperfccti, fig 8
Phialophora fasticata
Chloridium sp
Trichoderma lignorum
Penicillium sp
and several unidentified.
There is a well established agreement among all wood
scientists that the most effective preservative method for wood,
against biological destruction is pressure treatment with
creosote or chemical compounds. In the future, there will be
used more pressure treated wood in the building and repairing
Fig 5. Typical appearance of wet rot in ships frames* caused by
Coniophora Puteana
Fig 6. Typical decay in Scotx Pine Timber by Trametes Serial is
[283]
of wooden vessels, but one must not forget that the main
lines on which to work to solve the rot problem must be to
design the vessels in such a way that one can control and
keep the moisture content in the wood below the level that
creates the rot danger culture condition.
This means the importance of using well seasoned timber
in the building of new vessels and to practice regular moisture
check when the vessel is in use or storage.
Fig 7. Large rot pocket. Rot caused by Poria Sp
Difficulty of drying
Since there are very limited periods of good natural climatic
drying conditions in Norway, particularly in winter, autumn
and spring, it is a major problem always to builders, on how
to dry out new wooden materials and vessels in use. Even
when heating can be introduced, this method can be both
ineffective and expensive.
In addition to causing cracks and warping of the wood,
very often only partial drying of the surface takes place,
leaving the deep seated residual moisture in the wood. During
high humidity periods, high temperature drying can even
increase dampness and restrict drying, causing sweating and
condensation.
In the practical field application the dehumidification
technique of drying wood is important. The drying equip-
ment is a compact unit and has the advantage of being
portable. The dehumidification drying technique is based on
the principles of absolute humidity moisture extraction,
following and simulating the best natural climatic summer
condition for drying, i.e. 65 to 75r F (18 to 24" C) at 45 to
55 per cent relative humidity, with a steady gentle breeze or
air change. This technique operating in a closed area will
efficiently simulate these ideal summer drying conditions all
the year round, irrespective of outside climatic conditions,
granting a background temperature of 65 to 75° F is created
in the closed drying area. Since the drying zone is closed,
little outside air change occurs so the raising of background
temperature can be economically and easily created with very
little heat losses. The warm air circulating over the damp wood
steadily evaporates moisture from the wood into the air to a
high humidity condition. This moist air is drawn back to the
dehumidification unit and the moisture is condensed out of
the air and absolutely extracted, then drained away. The dry
air is then sent away to repeat its pick up of moisture from the
wood.
The following results are obtained from practical drying
test of inner shell area with a portable dehumidification unit.
The main objective of the drying test was to reduce moisture
content in wooden structure below danger point of rot
inception and culture environment for fungi growth. Of
primary consideration, this drying technique would provide
the dry background (18-20 per cent m/c) necessary for a
surface treatment of timber by chemical preservatives which
will not penetrate wood if saturated with moisture.
Testing moisture content
The ship to be tested was a Scots pine built fishing vessel
53ft (16m), built 1955. The fish hold was 600 to 700ft3
(17 to 20m3) dripping saturated everywhere. From 3pm
September 9th, 1965, to 12 am September llth, in 45 hours,
the dehumidifying unit extracted approximately 400 Ib (200 1)
moisture from the hold area. The next 48 hours extracted
1801b (901) moisture, which gave an ultimate moisture
content of the wood of 1 8 to 20 per cent. The moisture content
was checked with an electric moisture meter.
A low moisture content of 18 to 20 per cent is of course no
limit of the drying capacity, but in drying out vessels one will
not find it practical to dry to a lower moisture content because
of the problem of wood shrinkage. A second guide to the
control of moisture is to include in new vessels, remote
metal probes in rot-dangerous hidden areas of ship structure,
fig 9. The metal probes will be linked by flex wires to a
central open point so that the moisture content of hidden
timbers can be checked by electric moisture meter at regular
intervals and the rot danger culture condition anticipated
before it is too late. Much of the rotting goes on in these
hidden areas, and extensive damage is done before visual
indication appears. It is then too late to apply drying and
preventive techniques. Some suggestions for the future
would therefore be to build wooden vessels with (a) remote
metal probes, fixed at all vital areas, (b) a small permanent
dehumidifying unit to deal with excess moisture in critical
areas and (c) the possibility to give a massive dry out with a
larger dehumidifier.
Fig 8. Soft rot, caused hy Ascomycetes and Fungi Imperfect! in ships
planking
The important point is, there is no other known practical
method of measuring the moisture content of wood in the
field, except the laboratory approach of weighing wood
samples on a micro-balance. The electric moisture meter is a
fair practical guide — as accurate as is possible and based on
sound calibration principles. It is used widely all over the
world, in the field and in laboratories. If checked, at weekly
intervals as a routine, this would bring the problem far more
under control. Prevention is always far more effective and
economic than cure.
This should be the main objective: To know the potential
danger point — the excess moisture content of timber— is
[284]
10 points to
insidious
Remote areas
in ship.
2"stainless
steel probes
20'flex wires
fixed in vul-
nerable areas.
Plug in to panel
points for spot
check.
10 point-
remote Spaced as electric
indicator moisture meter probes
colour.
Panel in convenient
visual position,
(eq. cabin)
lUctrlc moiitur*
Fig 9. Fixed probe technique on wooden ships
90 per cent of the battle, for it is so much easier and quicker
to dry out 5 to 10 per cent excess moisture than it is to deal
with 100 per cent saturation.
Techniques for prevention
The long term approach of getting at the root of the
problem, by prevention techniques during the ship building
is the basic scientific principle on which to work.
Pedersen has presented a most interesting paper on wood
as a building material for fishing vessels. When Pedersen gives
the advantages of glued laminated members it seems likely
that he was forgetting to mention one advantage of great
importance and that is that each individual lamination can
be pressure-treated with chemical compounds, which in the
end can result in a structural element that is 100 per cent
penetrated. This seems to be one of the major arguments for
using glued laminated members in the future building of
wooden fishing vessels and the safest way with today's
knowledge to obtain increased protection against biological
destruction.
In Norway there are at least two boat-yards that have taken
advantage of the research carried out and are using the
combination of pressure treatment and the laminating
technique to give the new fishing vessels increased protection
against biological destruction.
Boat-yards also are finding the combination of pressure
treatment and the lamination technique competitive. A
fishing vessel built of pressure treated laminated members,
with all its advantages, only costs about 10 per cent more than
a conventionally built vessel and 10 per cent less than a steel
vessel.
Potter put forward the question of any damage being
caused on the wood as, for example cracking, with the de-
humidification technique of drying. To UllevSLseter's know-
ledge no extensive cracking takes place and this is one of the
major advantages with the dehumidification technique com-
pared to the common high temperature drying. This is because,
with the dehumidification, one is simulating the best natural
climatic summer condition for drying, i.e. 65 to 75 F (18 to
24° C) at 45 to 55 per cent relative humidity. At this low
drying temperature, the wood is dried very gently and the
surface tension is reduced to a minimum.
Simplicity and strength
Chapellc (USA): Pedersen has presented a very interesting
paper. Wood construction has been under attack for some
years on various grounds. This paper gives an answer to some
of the criticisms raised against wood.
However, it seems that the proposed glue-laminated
construction may be needlessly complex and, therefore,
costly. The supply of timber is not so stringent in the areas
known as boatbuilding centres, to require a completely
laminated construction. Glue-lamination has been accused
of producing brittle structures, but if such weakness exists,
the method can be applied in producing built-up forms, as
substitutes for large scantling timber members, without fear.
The part that might be played in timber construction, by
reversing the field of study, can well be considered. This is to
use simple hull forms, with a mixture of natural timber and
glue-laminated construction, primarily for exploration of
low cost construction.
In large wooden hulls, the procurement of heavy timber
has become an increasing area of difficulty. The solution does
not seem to be further gambles in experimental construction,
whether plastic, sheet material, glue-lamination or complicated
variations in wood construction. Composite construction;
implying use of steel frames, deck beams, floors, keelsons,
stem and stern liners and plate knees and stringers, with
wooden planking and decking, should certainly be first
explored.
This might save both cost and weight, combining the
supposed advantages of both steel and wood construction. A
yard experienced in wood construction could readily convert
to composite construction with only a small outlay in equp-
ment and in training help. There appears to be something
wrong with the strength calculations that create the supposed
need of very elaborate structures or for new materials. Few
boats built reasonably well, of timber, fail in strength for
engineering reasons. Rather, failure is due to rot or corrosion
or some external cause (worms, accidents, etc.). The classic
approach of taking structural details out of the hull and
applying assumed or rationalized estimates of loading is, of
course, faulty. The true loading of a boat hull is on the hull
as a whole and strain gauge studies indicate how difficult it is
to work out a useful estimate of probable loading in design
stages. It is this complication that also leads to over-designing
structure members. It was this that created so much interest
in scantling tables and standards in former congresses, for
these were based on trial and error over a long period, rather
than on theoretical engineering.
There is no need to produce stronger hulls by new construc-
tion methods, but rather to maintain similar strength with less
weight, labour and, of course, cost. This is particularly true if
information is being collected for use in the underdeveloped
fisheries, where capital investment must be low. Surely, this
is not a commonly suitable area for the introduction of
expensive, foreign materials and complicated building
techniques.
In making comparisons between wood construction and
other materials, there seems to be a tendency here to make
general statements derogatory to standard wood construc-
tion. There are certainly serious problems in the use of timber
[285]
and there are areas where other building methods might be
utilized.
However, it does not aid these other building techniques
to exaggerate the shortcomings of timber construction by
assigning extraordinary maintenance problems, short life,
lack of scientific data or other imaginary objections to use of
timber.
The decisions that must be made in deciding which tech-
nique of building is to be used, with respect to an under-
developed fishery, are too important to be based on anything
but an objective approach.
Laminated multiple-layer planking
Lindblom (Finland): Expressing appreciation of Pedersen's
excellent and comprehensive study of the material "wood".
Lindblom had been building wooden boats for almost 40
years, but he was really hardly fully aware of the beauty and
the outstanding properties of this material until reading
Pedersen's paper. He admired (and shared) Pedersen's
enthusiasm for the subject. The paper contains everything a
builder of wooden boats wants to know about the material he
is using.
Lindblom could find no reason for criticism at all. On the
contrary! In this paper, there is one statement which he
would like to underline. Pedersen has, as the first person
Lindblom knew of, treated wood as "engineering material",
a promotion and title this material really deserves.
LindblonVs firm once, ten years ago, was perhaps the
biggest wooden boatbuilders in the world — and at that time
they made extensive use of laminations in as much as all the
structural parts of serial built hulls (bed, frames, floors,
beams, etc.) were of laminated wood. They had obtained full
class approval for the lamination and construction technique
by the Marine Register of USSR.
After this period, during the last five to six years, they have
concentrated their attention as to wood on the problem of
developing a practically (and economically) usable technique
for the production of laminated multiple-layer planking (the
skin only).
In this respect, there has been some success. There are in
Finland about a dozen boats (fast naval gun boats, length
72 ft (22 m), displacement 50 tons, speed more than 36 knots
which are in service today. These boats have intentionally
been put through the most severe punishment to a degree
which has resulted in broken frames etc., but the planking
has endured this test. An evidence of this is the fact that for
a recent repeated order the Navy specified the same laminated
triple skin planking with thickness of 5 in (22 mm) main-
tained.
Some laboratory research tests aiming to obtain strength
figures have been carried out and are still going on. As this
material is not ready, as soon as there is more practical
production results, especially as to the economy and picture
of the building of round bilge hulls with multiple-layer
"glue-welded" planking a paper will be prepared and pub-
lished.
Lindblom would not bother to work along these lines if he
were not convinced that there is a great possibility for "glue
welded" wooden boats, but he was of course, as always,
an optimist and has behind him a long and mostly happy
marriage with wood which may influence his opinion. Only
the future can give the definite answer.
Wood best but scarce
Cardoso (Portugal): Thanked Pedersen for an excellent paper
on wood properties. It is said that steel (or even plastics) is
much better than wood for fishing vessels of more than a
certain length. The truth of such a statement is in fact depend-
ent on the economics of the locality concerned and has little
to do with the strength properties of the materials concerned.
Wood is indeed one of the very best materials available for
boat building.
The problem is only that in Europe and North America it
is becoming more and more difficult to find wood of good
quality, especially of the heavy scantlings necessary for larger
vessels. Also the skill of the ship's carpenter is of a high
order and he has a hard trade. Consequently his pay increases
steadily with time and he is more and more difficult to find in
comparison with steel workers, for whom training facilities
are much more readily available.
That this is indeed an economic reality is proved by the
fact that, without doubt, in Portugal where the economic
evolution described has not been so rapid, wood is still by
far the better case for fishing vessels of under 82 ft (25 m)
length.
Experience with plywood
Andersson (Sweden): After many years experience in building
both wooden yachts and fishing and catcher vessels up to
700 GT in the traditional way, Andersson had, during the
last ten years, been doing some development work with birch
plywood.
This is especially for refrigerated cargo vessels, normal
cargo vessels in the hold and for sun roofs etc. In ten years, it
has replaced loose boards of pine and other species because
of its better quality, labour simplification and improved
strength, tightness, etc. The material has been developed to
resist mildew and to have improved strength. This was
achieved by using improved gluing methods. The pressure
while gluing was increased from 100 to 200 lb/in2
(7 to 14 kg/cm2) to 270 to 350 lb/ina (18 to 22 kg/cm2), which
made it necessary to use new processes. On 8,000-ton refriger-
ated fruit carrying ships, the temperature in the cargo room is
changing from 43° down to 7° F (+6° down to -22° C)
and back — this is an additional test of the material.
Mildew was difficult to check. The usual preparations
against mildew could not be used due to the regulations for
the keeping of food stuffs. One new anti-mildew preparation
showed great promise without being poisonous. This was
tried on the surface of the plywood as well as mixed into the
epoxy paint. Mildew started again after some years. It was
then determined that the starch and sugar contained in the
wood expanded to the surface; the anti-mildew combination
was then also mixed into the glue used between the different
plies. In this way the glue layers also prevented mildew attacks
and the material became resistant throughout. A further
improvement was made in that the plywood sheets were
painted mechanically, by colour rollers using a pressure of
150 to 170 lb/ina (10 to 12 kg/cm2). The primer was pressed
into the wood fibres which resulted in good adhesion and
density of the anti-mildew mixture paint. After priming, the
panels were polished and further applications were made.
Two paint types were used— epoxy and uretan. Both lacquers
are of the hardening type.
The panels are made with grooves in all four sides, which
results in a great labour simplification. The waste compared
with loose boards has been reduced from 25 to 3 per cent.
The time for fitting has been reduced to half. These materials
are fully resistant against rot. Delaminations on any great
scale have not taken place.
Plywood glued to metal
These refrigerated cargo ships have plywood surfaces for
insulation and air ducts in the holds up to 185,000ft2
(17,000 m2). The thicknesses used are •&, t, i, J in (7, 9, 12,
18 mm). In addition 1 in (25 mm) is used for floors and the
[286]
top of bottom tanks. Truck transports up to 10 tons are
carried on such floors.
An advantage of the material is that under a load it gives
way and then returns to its original position. Compared with
metal and steel, it is much more elastic and easy to fit.
During banana transportation, the humidity is about
95 per cent at 37 to 43° F (-| 3 to +6°C). On the return
voyage, the holds are cooled down to ~-8°F (-22°C) in
order to reduce the humidity. This happens at two to three
week intervals during shipments between North America
and Europe. This hard testing proves this material can very
well be used for the construction of fishing vessels. Government
agencies are issuing certificates at the request of builders and
owners.
When gluing together with steel and other metals, tars of
epoxy have proved to be a very useful material. It is free
from water, contrary to other glue types. It has to be used
with a hardener which can be timed to suit the type of work.
For work which has to be carried out over a long period, the
hardener can be fitted to take place 7 to 8 hours after the
application of the glue. This epoxy tar prevents rot or the
penetration of water. At scarphs and other connections the
tar is penetrating so well into the material that delamination
of the ply layers is prevented. The tar has good elasticity
which makes it possible to glue together plywood with steel
and other metals.
This method of gluing plywood with metals has been tested
for a long period and is recommended as a good solution
also when building fishing vessels.
Relative virtues of different materials
Thiberge (France): A number of the papers give the impres-
sion that this or that material is conclusively better than the
others. The problem has two sides. Each of the materials
mentioned has its own peculiar technical characteristics
which naval architects and shipwrights must exploit as best
they can, but the accompanying drawbacks must also be
accepted in the various cases, and some attempt made to
compensate for the weak points by correspondingly better
hull construction.
Turning to Pedersen's paper in particular, it is so encyclo-
paedic on the properties of wood that one wishes to translate
them into practical applications immediately. Several succes-
sive stages must be gone through before one could hope to
arrive at entirely novel structures for fishing boat hulls. In
calculating the strength of the actual materials, it is not
enough to understand the material itself; it is necessary also
to know what stresses it must resist, potential strain patterns
and places of maximum stress. Now, these incognita arc too
complex and too numerous, and as regards the values of the
mean stresses to which the hull is subject under operational
conditions — and those stresses will obviously vary in a number
of ways depending on what sort of sea is running and, on the
other hand, the hull strength factors and their reciprocal
effect.
In the European fishing sector, the introduction of novel
structures for wooden hulls means that several successive
stages must be gone through and will need a certain amount of
time, particularly in the sense of the time taken by users to
try out under operational conditions the innovations as they
are introduced. At all events, there have been new developments,
as may be seen when one reviews the last ten years, for
example, in the use of plywood, laminated frames and engine
bed design. Obviously, not all innovations occur at the same
place or in the same manner.
Pedersen remarked that scientific research on wood has
been going on in all parts of the world over the past 50 years.
The research and publications of the Tropical Forest Tech-
nology Centre at Nogent-sur-Marne, on, inter alia, a very
wide range of African woods, should be mentioned in this
connection.
One final remark, this time on the strength of European-
type boats as evaluated by the Japanese. Otsu's safety co-
efficient had the following values: 35 (compressive strength);
88 (tensile strength); 16.5 (shear strength). It is a matter of
evaluating the strength of a part of the planking in respect of
the stresses it is normally called upon to withstand. However,
it is clear that the Japanese researches concluded that this
type of construction has its weaknesses, in that the material
"yielded" round the fastenings. Considering the cross checks
made with French research conducted a few years later, a
safety coefficient of 88 for tensile strength cannot allow for
the working loose of joints. Can some light be thrown on this
question ?
Plastic shearing on wood
Vcrweij (Netherlands): Pedersen mentioned the possibility of
sheathing wooden craft with fibre plastics. There are certainly
cases where this method is attractive, but the use of fibre-
glass for this purpose should be restricted to plywood boats.
In a planked boat the working of the wood will eventually
loosen or break the fibreglass skin unless this skin is very
thick which results in excessive weight. For planked wooden
craft nylon covering can be used successfully for instance by
applying "cascover" or similar method. Regarding laminating
of wood this is certainly a process well worth contemplating
in some cases. However, it puts a rather heavy burden on the
capacity of the workmen and is in general rather complicated
in practice. He would hardly consider it of great value for
developing countries.
Pressure treated pine in planking and fish hold lining
Haavaldsen (Norway): The proper preservation of wood in
fishing vessels is of great economical importance. In Norway
pine is used to a large extent in planking and girder. Tech-
nical experts strongly recommend the use of pressure treated
material, but this has been prohibited by health authorities
due to the risk of contamination. Since most of the pressure
treated material contains soluble substances these can con-
centrate on the surfaces due to evaporation of water from wet
material. So far known there is only one exception: Pine
treated with Boliden K 33 salt holds after fixation only very
heavy soluble substances (e.g. copper and chromearsenates).
It was felt that this material could be used without any risk
of arsenic poisoning. To throw light on the problem simple
experiments were performed to see if toxic amounts could
appear in fish contacting the Boliden K 33 impregnated pine.
Small pieces of fish fillets weighing about 1 oz (approx. 28 g)
were laid on either dry or presoaked small impregnated wood-
blocks at a temperature of 50° F (10' C) for 48 hours. The
fish fillets used were from Norwegian haddock and cod and
were alternatively placed with the muscle or skin side con-
tacting the impregnated material. Each fillet was trimmed
never to exceed $ in (0.8 cm) in thickness. For the practical
consideration there was no difference between the two ways
of applying the samples, and in table 2 the values are com-
bined. Each figure represents six samples.
Days ofpre-
soaking in sea
water
1
2
0
TABLI; 2
mg arsenic per K fish fillet
Cod Norwegian Haddock
range rartffe
0.008 0.005-0,010 0.010 0.0050.015
0.008 0.005-0,013 0.007 0.001 0.009
0.004 0.0020,008 0.003 0.001-0.003
[287]
The samples were small and the flow of resin around knots
made the surface inhomogenous in respect to preservation
substance. This is the reason for the range observed. If
larger samples of fish had been used, a narrower range would
have been found. Neglecting this and taking the highest value
found, 0.015 mg arsenic, as the base for consideration it will
appear that a man eating 0.7 Ib (0.3 kg) of a very thin fish
fillet, the whole side of which had been in contact with
Boliden K 33 impregnated pine, would have received a dose
of 4.5 mg of arsenic corresponding to about 6 mg arsenic
trioxide. Arsenic trioxide has been used for therapeutic
purposes and Norwegian doctors prescribed it in daily doses
of 15 mg. The lethal dose that can be found in the literature is
between 70 and 180 mg. It will appear from this consideration
that intoxication by arsenic contaminated fish under practical
circumstances, where only a small part of the fish can be in
contact with the fishholding material, cannot appear.
FUNGI ATTACK AND DECAY
Rasmussen (Denmark): Congratulated Pedersen on the
admirable manner in which all the relevant information on
wood properties has been compiled — ready for use for boat
designers. However, naval architects are never satisfied
regarding detailed information, and in this connection
Rasmussen asked two questions:
While Scandinavian pine is said to be fairly good for
pressure treatment, it is well-known that heartwood of pine
cannot be pressure treated. Has Pedersen any additional
information on the effect of fungi attack in actual practice
on such heartwood parts of, for example, pressure treated
construction elements of laminated pine.
The possible use of pressure treated beech as a ship-
building material is also intriguing. Has Pedersen any detailed
information on the use of pressure treated beech ?
Research initiated
Pedersen (Denmark): In 1963 OECD arranged a meeting
entitled Deterioration of Wood in the Marine Environment.
The Icelandic delegation, headed by Bardarson, reported on
an internal Icelandic meeting which had concluded that it
was advisable to have the following co-operative work:
fundamental scientific work by institutes in OECD member-
countries only, and technical and practical work by wooden
shipyards, associations and others interested in the problem,
under the guidance of the Government authorities. The main
subjects for fundamental research could be the following:
• Study of fungi causing decay in wooden boats
• Species of timber especially susceptible to decay by
fungi and marine borers etc
• Effect of different treatment of wood
• Non-destructive methods for testing for decay and
borers in wooden boats
The main subjects for technical and practical work could
be:
• Selection of timber for wooden shipbuilding and
quality certification
• Storage of timber for shipbuilding
• Practical possibilities of treatment of wood for ship-
building (boiling, drying, impregnation etc)
• Construction details in wooden vessels, influencing the
ecology of fungi and marine borers
• Practical aspects regarding repairing of wooden
vessel already damaged by fungi or marine borers
In the OECD meeting, Harmsen (Myceological Laboratory,
Wood Dept, Technological Institute, Copenhagen, Denmark)
stated that in many cases deteriorated oak was infected before
assembly (Polyporus sulphureus and Stereum spp), and in
other cases the decay was due to absorption of water through
leaks, condensation and/or poor ventilation (Coniophora
cerebella). Table 3 summarizes the fungi observed in samples
of different wood species. Often more than one species of
fungi were found in the same boat. The table gives no in-
formation concerning the relation between attacked and
sound boats, this relation may be more than 10 per cent. The
expense in repair varies from a negligible amount to £3,000
($8,500), or even sometimes more than the insurance value
of the vessel. The number of motor fishing vessels in Denmark
is approximately 8,300 of which about 4,300 are less than
5GT. In Denmark 13 local mutual insurance companies
insure against losses due to "fast-growing" fungi and only
such attacks are covered by the insurance.
In table 4 detailed figures showing the Danish condition
are given. In the period 1950-64 the insurance companies
have paid a total amount of 3.2 million dkr (£160,000 or
$450,000) distributed on 253 vessels repaired. Owners them-
selves have paid an amount approximately of 900,000 dkr
(£45,000 or $125,000). Economical losses due to attacks of
"slow-growing" fungi (i.e. soft rot) are assumed to be of the
same magnitude and may be approximately 4 million dkr
(£200,000 or $560,000). The average costs of repair of detected
damages therefore may be approximately 1 million dkr
TABLE 3
Fungi observed in Danish wooden boats (mainly fishing boats) as of August 1963—219 boats
Wood species
Fungus species
(fir7'
Picea
(spruce)
Larix
(larch)
tsuga
(dougl.
fir)
Fagus
(beech)
Fraxi-
nus
(ash)
Quercus
(oak)
Un-
known
Total
per cent
of
samples
Coniophora cerebella
35
18
2
2
3
2
95
1
158
81
Polyporus sulphureus
—
—
—
—
—
—
15
. —
15
7~]
Polyporus spp *
7
3
—
1
2
—
4
1
18
8 >30
Polyporus sp (unidentified)
8
1
—
1
_ ~
—
22
1
33
15j
Stereum hirsutum .
—
—
—
1
.— .
24
_
25
11 1
Stereum frustulatum
—
—
—
—
—
4
—
4
2MB
Stereum sp .
—
—
—
—
—
—
9
1
10
5j
Other species t
10
1
—
3
—
—
6
—
20
Unidentified
13
5
—
2
—
4
20
2
44
Soft rot
2
3
___
—
2
1
35
1
44
Electrochemical attack
1
—
—
-—
—
— —
5
—
6
* Fomes foment ariusm, Polyporus balsameus, P.versicolor, Porta monticola, P.vaillantH, P. xantha, Trametes serialis
t includes Coprinus sp, Paxillus, Schizophyllum, Hymenochaete, Corticium, Peniophora, blue stain fungi and moulds
Insects: Xestobium rufovilhsum, 1 sample, oak. Nacerdes melanura, 1 sample, oak.
[288]
(£50,000 or $140,000) per year. The insurance value of the
fishing fleet in 1962 was about 400 million dkr (£20 million or
$56 million). The number of fungi-attacked vessels was
24 vessels older than 40 years before 1925
65 vessels between 30-40 years 1 926 1 935
85 vessels between 20-30 years 1936-1945
17 vessels between 10-20 years 1946-1955
TABLE 4
Economical losses due to detected and repaired fungi
attacks in Danish wooden fishing vessels
Year
No. of re-
paired
vessels
Amount paid
J,000</Ar
Insurance
value of
fleet in
No. of
vessels in
fleet
million dkr
( ;5GT)
1950
1
20
142
1951
144
1952
2
31
160
1953
2
21
163
3,597
1954
2
29
167
3,590
1955
7
106
173
3,578
1956
7
55
184
3,567
1957
19
21 1
208
3,633
1958
27
205
234
3,682
1959
22
218
290
3,814
1960
24
290
366
3,970
1961
22
298
417
4,045
1962
43
526
438
4,060
1963
75*
1,215*
4,062
Total
3.216
Owners1
own risk
880
7 dkr 1 US
dollar
4,096
-4.1 million dkr
20 dkr -1 pound sterling
*sum of non-specified attacks
Information on 62 vessels is lacking. To illustrate Harm-
sen's statements, fig 10 shows a great knot with white-pocket
rot situated in a floor member in a vessel during construction
in a Danish yard. Fig 1 1 is taken from Cartwright (1958) and
shows an axial cut-through such a knot with white-pocket
rot, caused by the fungi species Stereum gausapatum, which
attacks dead branches on living trees.
In 1950 the Danish Ministry of Fisheries built a fishery
research and inspection vessel, Jens Vaever, at a well-known
shipyard. It was built with first-class workmanship and had
tight-fitting ceilings in all cabins etc. Nine years later this
vessel was condemned. The fungi (Stereum hirsutum) had
eaten most of the longitudinal strength timbers. The fungi in
question especially likes sapwood of white oak and infected
sapwood must have been fitted when the vessel was built. In
the shipyard, just as in most other traditional Danish
yards, wood logs and even planks arc placed on the ground
where the risk of infection by fungi is especially high. Due to
the high moisture level in newly cut timber, the wood pro-
vides a good growing substance for spores and mycelia of
wood-destroying fungi, created from adjacent pieces of
rotting timber lying in the yard.
Wood can be compared with meat, and the following
question is relevant: "does anybody dream of placing a lump
of raw meat on the ground for a week in summertime before
eating it?" The next question therefore is: "why then is it
permitted to use wood which has been placed on the ground
and consequently infected by fungi, as a boatbuilding
material?" The result may be either that human lives and
material are lost for unknown reasons at sea, or the attack
Fig 10. Knot with White Pocket Rot in a floor member
ig 77. Axial cut through a knot with White Pocket
TABLI- 5
L.OS
Loss of lives of Danish fishermen:
is 01 lives
i ana mi
arena 1 1
in Licni
nark ai
uring ti
ic peric
>a IVM
-H4
Causes
7957
52
5.?
54
55
56
57
5*
59
60
67
62
63
64
Suspicious: in connection with wreck-
age for unknown reasons
6
5
13
. _
13
15
13
13
8
1
4
21
Suspicious: unspscifisd reasons .
2
1
3
...
4
3
1
1
1
_!_
Unsuspicious: spscified reasons .
16
20
15
21
13
12
14
15
6
13
12
14
..,
Total loss of lives:
24
25
31
21
26
31
30
29
15
14
17
35l
15
19
Loss of Danish fishing vessels:
Suspicious: sprung a leak for unknown
reasons
2
3
6
6
1
1
2
—
2
5
2
1
3
Suspicious: wrecked for unknown rea-
sons .
7
5
7
1
2
7
6
3
4
3
2
6
6
4
Unsuspicious: specified reasons .
13
8
10
10
13
5
3
8
5
13
13
12
6
5
Total loss of fishing vessels:
22
16
23
17
16
13
11
11
11
16
20
20*
13
12
'Including 1 1 losses in connection with losses of 5 steel vessels,
including 5 losses of steel vessels.
;289]
is detected in time and repaired as shown in fig 12. As shown
by Cartwright and mentioned in Pedersen's paper, even a
slight attack by fungi has a serious weakening effect on
impact load strength properties of wood.
In addition to being a problem of high economical im-
portance, decay is also a problem of safety. In table 5 from
the statistics issued by the Danish Ministry of Fisheries, a
classification is given of losses of lives and vessels. In 1951 to
1964 128 fishermen and 97 vessels have been lost due to
unspecified reasons. Some losses may be caused by attacks
from wood-destroying fungi in the timber structure.
Fig 12. Fungi attacked wooden fishing vessel under repair
Icelandic investigations
Bardarson (Iceland): Owing to serious damage in wooden
fishing vessels, caused by fungi, the Icelandic Government
began in 1955 to assist owners of the vessels involved.
Thus the Government paid compensation in the form of
90 per cent of repair cost as follows:
Year
1955
1956
1957
£
31,300
76,600
188,000
US $
87,613
214,145
527,245
When the fungi attack (mainly Coniophora cerebella and
some Poria spp) was discovered in increasing number of
vessels an insurance system was created by Law of 29th April
1958 and committed to the Icelandic Fishing Vessels Joint
Insurance Institute.
Since the beginning of this Insurance system compensations
have been paid as follows:
Year
1958
1959
1960
1961
1962
1963
1964
1965
Total:
92,500
185,006
73,300
117,000
83,000
137,761
247,874
375,349
1,311,790
259,782
517,192
205,230
328,155
232,234
384,450
691,742
1,047,485
3,666,270
(The figures for 1965 are partly estimated.)
The figures of the years 1958 to 1965 incl. represent
approximately 75 per cent of the actual repair costs, as the
vessels owners have in their own risk 10 per cent and also one-
third of new material for old.
The number of vessels insured against fungi-attacks has
been about 600 vessels in recent years, and the insurance
amount, which is based on 90 per cent of hull value and other
woodwork (machinery and equipment is excluded) is about
£485,000 (US $1,354,000). Until the year 1960 the approxi-
mate annual addition was about 25 new wooden fishing
vessels to the fleet, worth about £250,000 (US $700,000),
Since 1960 almost all new-built Icelandic fishing vessels are of
steel — only a few of the smallest types are still built of wood.
In the year 1958, when the fungi-insurance began, until,
and including 1962, 85 wooden vessels have been repaired
after such damage, and eight have been condemned as total
loss.
In the year 1963, 17 vessels were involved in fungi-attack;
of these 13 vessels were repaired and four vessels condemned.
In 1964, 32 vessels were involved; of these 19 vessels were
repaired and 13 vessels condemned.
In 1965, 47 vessels suffered fungi-attack; thereof 23 vessels
were repaired and 24 vessels condemned.
Precautionary treatment
When repairing wooden Icelandic fishing vessels, and in
new buildings care is taken to use the best available wood
quality, and although not artificially dried, it is treated with
fungi-destroying chemical preservatives, containing at least
5 per cent of penlachlorphcnol according to request by the
State Directorate of Shipping. At the same time care is taken
to ventilate as far as possible the closed-in spaces where
structural members are covered with ceiling, watertanks etc.
Experience has shown that fungi attack is very seldom in the
engine-room where dry, hot air keeps the moisture in the
timber lower. Further mechanical ventilation of other parts
of wooden fishing vessels and also artificial periodical drying
out (dehumidification) of existing wooden vessels with
repeated conservation by chemical preservatives containing
pentachlorphcnol is now under consideration in Iceland.
In spite of the fact that more than 90 per cent of new-
built fishing vessels for Iceland are now built of steel, there
are still many wooden vessels in the Icelandic fishing fleet,
and the smallest ships are still built of wood.
WFA survey in UK
Sutherland (UK): A decay survey was instigated by the White
Fish Authority in conjunction with Forest Products Research
Laboratory and Torry Research Station, both of the Ministry
of Technology, to investigate the increased incidence of
decay in the fishrooms of Scottish wooden fishing vessels.
Forest Products Research Laboratory have been acting as
advisors, examining specimens of decayed timber removed
from fishing vessels and determining the species of fungi
found.
Torry Research Station are engaged in testing the effects
of a variety of wood preservatives on the quality of fish by
treating fish boxes, keeping fish in the boxes, later cooking
and testing the quality of the fish by means of a taste panel.
The report is still awaited but it is known that rather wide
differences in the results have been found.
The Authority are carrying out the field research and a
large number of fishing vessels are being surveyed for signs
of decay. Moisture content surveys are being carried out by
drilling into the timbers with a borer or an auger and extract-
ing cores of up to 2 J in (63 mm) long. These cores are
weighed almost immediately, dried in an oven at 21 2° F
[290]
(100° C) for 4 hours, then reweighed. Wide divergencies of
moisture content have been found in the same fishroom, and
readings from 20 to 1 20 per cent have been recorded. Readings
are also being taken before and during building to determine
the exact amount of drying that takes place during building.
These new vessels are to be checked periodically to record
the build-up or otherwise of moisture content.
In new construction certain remedial steps have been
taken, the main ones being— oak has superseded larch for
ordinary beams, the deck planking is pressure-impregnated
and all other wooden members of the boat are either dipped
or surface treated with a wood preservative.
The use of more decay resistant timbers is being investigated
and in some cases, is being tried,
The problem in the case of existing fishing vessels is more
serious as the replacement of susceptible timber by more
decay-resistant timber would be a long and expensive process,
It is advised that the fishroom should be dried, the paint
removed and the whole of the interior timber surface treated
with a wood preservative and that no repainting should take
place. This treatment should be repeated at each annual
overhaul.
Possible remedy for decay
Forest Products Research Laboratory have suggested a
possible remedy for the decay in fishing vessels which is now
being examined. A specified amount of a borax paste is
applied to the larch beams. The paste diffuses into the timber,
killing any incipient decay and inhibiting the timber from
future attacks.
Twelve pieces of larch, 6 in (15cm) square and 14 in
(35.6 cm) long similar to that supplied to the boatyards were
prepared by Forest Products Research Laboratory in the
following manner. Two 4 in (16mm) holes were drilled
through from top to bottom and the holes packed with borax
paste. One of the holes was plugged at both ends whilst the
other hole was plugged only at the bottom in order to as-
certain whether diffusion is more rapid with one end open to
the humid atmosphere of a fishroom. The blocks which were
painted with bitumen leaving the top face bare, were then
fitted alongside the beams on three different fishing vessels,
four to each boat, leaving the top bare surface slightly below
the decking to allow the moisture to gain access to the bare
face of the treated blocks. A further 12 blocks, treated in a
similar manner were retained at Forest Products Research
Laboratory to act as a control.
This treatment, if successful will enable vessels to be
protected at a reasonable cost. A quantity of this borax paste
has now been supplied by Forest Products Research Labor-
atory and will be tried on a number of fishing vessels.
Borings will be made at regular intervals to follow the move-
ment of the paste into the timber. A U-shaped piece of cheap
timber painted all over will be fixed alongside a larch beam
which has had all sealing materials, such as paint, removed.
The groove will be packed with the solution.
The paste is made up as follows:
weight parts
"Timbor" (trade name for borax
powder) 5 Ib 80
Water 5 Ib 80
"Polycel" (wallpaper adhesive) 1 oz 1
Ethylene glycol 2 oz 2
The dry "Timbor" and "Polycel" are mixed together and
then added slowly to the ethylene glycol and water, stirring
the mixture all the time. The paste is ready for use about
24 hours later and should be sufficient in quantity to treat
three deck beams. Approximately 1 Ib of paste is required
per yard (0.5 kg per m) of beam with a section of 6x8 in
(15x20 cm), which means that the groove in the U-shaped
timber should be J to 1 in (12 to 25 mm).
It is necessary, when surface preservative treatment is to
be carried out on a fishing vessel, that the timbers should be
dried and all paint removed whereas with the borax treatment
only a small area of paintwork requires to be removed and
the wetter the timber, the quicker the diffusion.
Tentative conclusions
Some conclusions have been reached as a result of the work
carried out up to the present. It appears that the larch
members of the fishroom show appreciable drying while the
oak members show little difference in moisture content. This
is not so important as oak is more resistant to decay. Furtner
work is required in this field to establish how often forced
drying would need to be carried out to yield a cumulative
effect which could be expected to reduce the overall decay
hazard.
Although there is a wide range of moisture content read-
ings in the same fishroom there is one common factor. The
timber in and around the ice lockers and especially the
beams above the ice locker are very wet, giving a clear
indication of the detrimental effect of open ice lockers. This
in itself suggests a strong argument for ice lockers to be made
in the form of insulated vapour-proof boxes separated from the
fishroom main timbers to allow free ventilation.
It will be seen from table 6 that the main fungal attack on
the larch beams has been identified as Coniophora cercbclla
(Cellar fungus) and the main fungus identified in decayed
Douglas fir is Poria monticola. This latter fungus is not natural
to UK but is imported in the Oregon pine from North
America. The spores of the fungus lie dormant in the timber
but become active under suitable conditions.
The treatment of Douglas fir decking by pressure im-
pregnation will stop the spread of the fungus from one
plank to another and thence to the beams. It will not stop the
internal decay within any plank that contains those spores as
only sterilization and pressure impregnation would make
certain of decay-free timber. Decay in oak is more severe
where linings have been or are fitted to the fishroom and
suitable ventilation is not present. Several cases of decay in
oak were due to sapwood being present and in others red or
turkey oak had been used instead of European oak. This red
oak, which is no more resistant to decay than larch, is almost
impossible to distinguish with the naked eye from white oak.
(Pedersen (Denmark) advised a study of the guide for dis-
tinguishing red oak from white in US 1957-62, Vol I, pp 8-10).
TABLF 6
Material from 20 Scottish-built boats examined (a few samples came
from sources other than the WFA). The table shows the number of
boats in which decay by the fungi listed was confirmed in the timber
species indicated
Un-
Poria P."f Poria known Ster-
monti- car- sp wood eum
cola bonica dsst- sp
Conio-
Timber
phora
cere-
hella
Larch
9
Oak .
2
Red Oak .
Douglas Fir
2
Gurjun
Baltic Redwood
dsst-
royer
1
^Includes two instances where, by inference, the fungus had spread
from Douglas fir to larch.
t Poria carbonica is like P. monticola, a North American fungus.
[291]
K2
Importance of joints and scarphs
Pedersen (Denmark): As mentioned by Potter and as is well-
known to all boatbuilders, the strength and stiffness of a
wooden boat depends on the joints. Their strength depends
on their fitting and the right distribution of proper fastenings.
The moisture content must also be on the same level as in
service to avoid open seams and loose fastenings. Vital
details, such as keys and dowels of hard wood, placed in
the scarphs to take shear, have been "forgotten" in the last
decades. Boatbuilders claim that they are time-consuming to
fit and therefore the cost will rise if such ''refinements'* are
insisted upon. The result has been an increase in scantlings
in individual members (when comparing Danish rules issued
in 1933 and 1947). This has created an even more unfavour-
able ratio between strength of joints and strength of scantlings,
consequently there is a general decrease in overall strength.
Fig 13 shows that timbers in sawn double frames formerly
were connected by fastenings placed near the edges, while
present-day practice only shows fastenings placed in the
neutral axis of the frame members. Detailed performances
showing joints of varying efficiency as found by tests should
be given for the advice of the boatbuilder and scantlings
should be determined accordingly.
': i ' ' : :'|'i i ' ' I;'!'; ; •
• :•!•: ; •
s
A
i i ' ! i ! i i 'i
I 1 D! !D! [ o1
1 { ' { ' i ' i ' " '
! ! H||!E3 ! m\
, X + ^U-...- A J. * *-
FORMER-DAY PFRFORMANCE.
ZT
PRFfifNT DAY PEf?FQF;M ANCT .
Fig 13. Double frame practice formerly and today (types and distri-
bution of fastening and wooden keys in old type frames)
Fig 14 shows floor/frame joints in a vessel under construc-
tion. When supplies of curved shipbuilding timber were
plentiful, there was no trouble to find the right piece of
timber for every curved member. Scantlings-rules were based
on this. Today it is not unusual to find curved pieces sawn
from straight or nearly straight timber, with cross grain as
the result, thus having little strength.
Fig 15 shows a part of the frame system of a wooden
vessel. In one of the timber pieces, a long shake running
across the member can be seen. Fig 16 was taken in a flat-
bottomed vessel (ferry). At both ends, approximately one
third of vessel's length from stems, all floor members are
notched down to half the rule moulding, consequently re-
ducing the strength of this vital point on the floor element.
What is the reason for demanding heavy rule scantlings
outside the notches, when such strength-reducing notches
are tolerated at this vital spot ?
Fig 15. Shake due to cross grain in a frame member
Fig 14. Performance of frame joints in a_vessel under construction Fig 16. Floor member notched down to give place for propeller shaft
[292]
Lamination
Hareide (Norway): Added some comments on experience of
laminates in Norway. A series of experiments are at the
moment in progress but not yet complete. They feel that by
the correct use of laminated structures, much strength can be
gained. Temperature and humidity control are essential. If
not correctly laminated under right conditions, laminates are
liable to disintegrate either in a short while or maybe over a
long period. Machinery is important and at the moment still
not satisfactory. In Norway they still use manual assembly
but are experimenting with machinery.
Sinclair (UK): It would seem, from comments so far made,
that the fabrication of laminated members is very difficult,
This is not the truth; a well laid out shop and good super-
vision can provide laminations without a great deal of highly
skilled labour. A slatted platform which can be used in the
same way as a steel frame slab can be erected above hot water
pipes supplied by an ordinary central heating boiler and
pump. The glued members can be covered by tarpaulins and
left to set overnight. It is not claimed that laminations are
better than, only a substitute for, natural frames, beams etc.
when natural wood supplies arc difficult. Both can be in-
corporated in the same vessel.
Glue lines in laminations can easily be tested for adhesion
but the real test is whether they will last for 15 to 20 years.
In't Veld (Norway): As the technical leader of a boatyard in
Norway building laminated and pressure treated fishing
boats for the North Atlantic, In't Veld said that it is not so
simple as Sinclair said. It is not only the heating, but also and
maybe more important is the moisture, which is supplied
while heating for hardening and it is the moisture in the
timber before glueing, temperature in working sheds, drying
methods of pressure treated wood, and so on.
Another difficulty is training the workers and in Norway
the skilled boatbuilders are "dying out". This is the only
reason why fishing boats arc made of steel. The average age
of boatbuilders in his yard is 45 years, but they are now
training a new generation. This boatyard has built about 400
ships since 1902 in a district where almost everyone was a
boatbuilder.
To make clear the difficulties in the laminating method
there have been examples of boats falling to pieces. Well,
these boats were made by yards where it was believed that
laminating was a simple affair, but these yards were no longer
in existence. This happened at the beginning of the laminated
period.
The laminations are controlled by the Norwegian Wood
Council to the rules of the Norske Veritas. Everyone ordering
a laminated vessel has to insist on inspection by an authori-
tative institution, to the rules of Norske Veritas or similar.
Traung (FAO): There was a meeting in Denmark in 1964 to
consider wood for shipbuilding. It was announced that
Norske Veritas had rules for laminated fishing vessels since
1955. If a boat was built in Denmark to the rules of Norske
Veritas, would the boat be approved -the answers were
**yes". Now Hareide indicates that he is working on some
new rules for laminated wooden fishing vessels in Norway —
will the Norske Veritas rules be amended?
Hareide (Norway): They are not working on new rules, they
are experimenting to improve the procedure of lamination.
The further purpose is to facilitate the work and give guidance
to shipbuilders, thereby promoting safety and reduction of
prices.
The rules of Det Norske Veritas on wooden vessels have
been approved by the Norwegian Authorities, and are now
under revision.
Retvig (Denmark): Denmark has no rules for lamination of
fishing vessels. If any owner wishes to build with laminating,
the Danish authorities will approve the vessel, if it is classed
in Norske Veritas or Bureau Veritas.
If the owner wishes his vessel to be unclassed, the Danish
authorities will approve the dimensions after the classification
rules, as regard laminated ships. For conventionally built
wooden fishing vessels the rules issued by the Danish Govern-
ment are known to be near the strictest in the world and need
to be revised, in order to save wood and weight. It is difficult
to take the necessary steps for such revision until there will
be similar rules for all the Scandinavian countries and
perhaps UK and Germany, for fishing vessels operating in
the same area and under same circumstances.
Scantling rules
Pedersen (Denmark): Gnanadoss (1960) compared scantlings
in respect of cubic content of timber per 1 m (3.28 ft) length
amidship for: Simpson's (1960) proposals; New England
trawlers as built (no rules); Bureau Veritas, France; Danish
Government rules; Swedish rules; Newfoundland rules;
Hanson's (1960) experience data (US Pacific coast). Conclu-
sions:
• Small and medium -si zed boats are much more heavily
built than would appear necessary according to
Simpson's proposal
• Boats built to the Danish rules are the heaviest in the
categories analysed
• Newfoundland rules lay down that where timber
other than Newfoundland timber is used, it may be
sided and moulded Jin (12.7mm) smaller if the
construction is entirely of hard wood. This reduction
does not appear sufficient in the larger boats
• It might be possible to evolve unit weights for the
different categories of boats, which may form also a
basis for estimating the total weight of the hull
• The possibility of gathering further information to
cover small boats, to compare the existing scantlings
and to suggest more judicious and rational use of
timbers
• Gnanadoss' comparisons form a basis for comparing
scantling regulations in several other countries and
eventually to formulate uniform regulations
• Simpson's proposals appear a fair basis for determin-
ing the scantlings and are a fine blend of scientific
knowledge with practical experience
in 1964 the Danish Wood Council in co-operation with the
FAO Fishing Boat Section arranged an international meeting
in Copenhagen entitled "Structural research on wooden
fishing vessels". Forty participants from 15 countries agreed:
• That a non-dimensional approach based on expected
strains and stresses and applicable to various methods
of construction should be encouraged
• That it would appear important as a first step to
decide upon common rules for defined geographical
regions
• That at the same time no effort should be spared to
utilize existing knowledge and rules for the inter-
mediate establishment of a more rational rule basis.
This should encourage improvement of local building
practice, improving the safety and economy of vessels
by better utilization of building materials
• That continuing international co-operation in establish-
ing such rules should be encouraged by all means
[293;
• That ways and means should be found to allow for a
co-ordination of individual studies in this direction
to be effected, and
• That proper preservation of wood is of equal import-
ance as the provision of suitable scantling rules
Pedersen had carried out work following the conclusions.
Rules issued by the following authorities (Classification
Societies and Governmental bodies) were compared:
A Bureau Veritas, 1963
B German Lloyd, 1964
C Danish Governmental
rules, 1947
Al:
A2:
Bl:
B2:
B3:
CI:
CII:
D:
D Swedish Governmental
rules, 1952
E Norwegian Veritas, 1955/57 El:
E2:
F White Fish Authority,
Scotland, 1960 F:
5-4 OM (17-7 1 FT)
double frames
glue-laminated frames
single frames
double-frames
glue-laminated frames
open double frames
closed double frames
double frames
double frames
glue-laminated frames
single and double frames
40FT(l2'2M> LOA
LOA/D 5-3O
B/0 1-65
6OFT(l8-3M) LOA
LOA/D 6'65
B/D 1-965
8 OFT (2 4-3 M) LOA
LOA/D 77 O
B/D I-97O
I OOF T (3O5 M) LOA
LOA/D 6-90
B/D 200
Fig 17. Midship sections of vessels
Four basic vessels of length 40, 60, 80 and 100 ft (12, 18,
24 and 30 m) LOA and same type of midship section, fig 1 7,
were compared in respect of the following terms:
weight over strength of longitudinal and transverse
strength members
utilization of material (solidity)
weight over capacity
cargo carrying efficiency (deadweight displacement ratio).
The following assumptions were made:
1 . All wood material assumed to be homogeneous and
isotropic
2. No joints in longitudinal and transverse strength
members
3. Only one part of a double frame was considered to
be effective when calculating section modulus for
double frames
4. Keel, keelson and garboard material to be con-
centrated at keelcorner
5. Bilgeplanks and bilgestringers to be concentrated at
bilgecorners
6. Sheerstrakes, beamshelves, beamclamps and covering
boards to be concentrated at the deck side corners
7. Principal dimensions determined from fig 18 (figures
given in Danish rules as table 1A, page 11)
8. Section modulus for midship sectional cross area
was calculated in the traditional way (1 m deck
planking area is excluded for hatch opening)
9. Section modulus per 1 m floor frame and beam
system was calculated from the following equation:
WB = , where b = siding of one part, h =
s
moulding and s = frame spacing
(Reference: Bureau Veritas rules 1963, page 15,
article 5-21-45, and page 20, article 5-46-3)
10. Floor members to be considered as members lying
between keel and bilge
1 1 . Frame members to be considered as members lying
between bilge and deck corner.
20 MCTfttfc 2S
kCNCTH OVCNALL
Fig 18. Principal dimensions of vessels
The results of these calculations are given in fig 19 to 26.
The conclusions are:
Weight/strength of longitudinal and transverse strength
members
Fig 19 shows how much longitudinal material is used to
obtain the same section modulus of the mid-sec area. All
rules compare very equally in this respect. The curves are
downward sloping, which is surprising as it was thought that
more longitudinal material was needed for the larger sizes.
The longitudinal material seems to be better utilized in the
larger sizes than in smaller. An explanation may be that
local strength requires nearly the same thickness of hull
planking for all sizes. The diverging character of the Scottish
curve F in the upper size range is remarkable.
[294]
2
Is
LENGTH OVERALL
g 19. Longitudinal material per 1 m mid-sec area: section modulus
of mid-sec area
In fig 20 the values differ widely. Curves E± (Norwegian
sritas) and B2 (German Lloyd, double frames) show the
ost unfavourable values, while curves A2 (Bureau Vcritas,
Li-lam frames) and B3 (German Lloyd, glu-lam frames) show
e best. Danish curve C, CI and CII show intermediate
ilues.
II
60 F££T BO
IS 20 MCTaCS 25 30
LENGTH OVERALL
Fig 20. Floor material per J m m?d-sec area: section modulus per 1 m
floor system
In fig 21 the curve Al (Bureau Veritas, double frames)
compares most unfavourably, and curves Bx (German Lloyd,
single frames) and F (Scottish rules, single frames) show best
values. Danish curve C lies in the upper range of the diagram.
LENGTH OVERALL
Fig 21. Frame material per I m mid-sec area: section modulus per .
frame system
The curves A2 and A: (Bureau Veritas) in fig 22 show m
unfavourable values, while curves D (Swedish) and F (Scotti
show best. The Scottish curve F shows a remarkable 1
value in the 60 ft range, The Danish curve C shows
intermediate trend of all curves given.
O-5
LFNGTH OVERALL
Fig 22. Beam material per 1 m mid~sec area: section modulus per 1 m
beam system
Utilization of material (solidity)
This is a concept used in aircraft design to compare how
well material is utilized in the same structure made in different
applications. The curves Cl and Cll (Danish) in fig 23 show
[295]
most unfavourably while the curves Aa (Bureau Veritas, glu-
lam frames) and B3 (German Lloyd, glu-lam frames) show
most favourable values.
I* 20 METPES 25 3O
LENGTH OVERALL
Fig 23. Total material per m structure of mid-sec area: volume of a
1 m prism with mid-sec area
Weight/capacity
Fig 24 shows how much material is used in order to obtain
the same payload volume. Payload volume is a rough
20 METRES 25
LENGTH OVERALL
Fig 24. Total material per 1 m mid-sec area: payload volume per 1 m
mid-sec area
measure for GT of the vessel. Here the curves CI and CII
(Danish) compare worst, while curves B3 and A2 show best
values.
// PAYuOAD APIA
MIDSHIP SECTION AREA
Fig 25. Payload volume per 1 m mid-sec area: actual volume per 1 m
mid-sec area
Fig 25 shows roughly measure of the "tonnage factor"
or GT:displacement ratio. Here the Danish curve C naturally
shows the lowest values due to the great moulding of the
transverse members. This, claimed to be favourable by
Danish boatbuilders, is only apparently favourable because
it is gained at the cost of heavy amounts of timber.
IS 20 METRES 25
LENGTH OVERALL
Fig 26. Deadweight: displacement ratio
Cargo carrying efficiency expressed by the term— deadweight:
displacement ratio
Fig 26 indicates the cargo carrying ability or efficiency
for vessels compared. As deadweight is equal to displace-
ment minus weight of light ship, it is obvious that values
approaching unity are most favourable. The curves A2
[296]
and B3 show most favourable values, while the curves CI
and CII show most unfavourable.
The Danish rules permit two different double-frame systems,
see fig 27. A fixed timber-spacing and not a fixed frame-spacing
is prescribed by the rules, and it is left to the boatbuilder if he
prefers open double frames with 2 in (50 mm) distance
between the timber parts or closed double frames, in which
the timber parts lie close together. In practice the same
vessel can be either built with a greater number of relatively
stronger closed double frames or a smaller number of
relatively weaker open double frames. In the calculation
differences occurred, as only frame spacing is used in the
equation, but even greater differences than shown in the
graphs exist in practice. In no other rules docs this strange
situation occur, although the two performances of double
frames are also allowed in other rules (i.e. Norwegian
Veritas).
As a general conclusion, it may be said that material
seems to be utilized and distributed most efficiently in vessels
built in accordance with the rules issued by Bureau Veritas
1963 and German Lloyd 1964 for vessels built from glued-
laminated strength members, while the most inefficient use
and distribution of material seems to be prescribed in the
rules issued by the Danish authorities, 1947.
DANISH RULES:1947
TIMBERSPAClNG't. fixed
FRAMt SPACING is. vary.
NORWEGIAN VTRITAS 1955
TIMBERSPACING: t , vary
FRAME. SPACING, i. fixed
Fig 27. Frame and timber spacing in open and closed frame per-
formances according to Danish and Norwegian rules
Boat strength basis
Sutherland (UK): Pederscn is at least a courageous man and
if his tables of comparison were designed to make official
bodies wake up to the discrepancies in scantling sizes in the
wooden fishing fleets fishing in the same waters he succeeded
in his purpose. However, it is suggested that until there is a
basic strength requirement from which to work such com-
parisons are of little use except possibly to make those
nations whose vessels are in the more favourable side of the
diagrams sit back complacently and say "Well, we always
knew our boats were stronger".
Can Pedersen say what the strength requirements are and
if so, on what does he base his findings ?
The divergence shown on each of the graphs for the
Scottish scantlings are of course due to the fact that at 80 ft
(24m) the single sawn frames become double. The reason
for this is that the sizes of timber required for single sawn
frames are difficult if not impossible to obtain. However, it
is doubtful if any fishing boat of over 80 ft (24 m) will be
built of wood in the UK in the future.
Wood versus steel
Bardarson (Iceland): Congratulated Pederscn for his excellent
paper. Wood has been the material mainly used for smaller
Icelandic fishing vessels for centuries, and for many many
years there have been Icelandic rules for the construction of
wooden vessels up to about 250 GT.
Such vessels have been built both in Iceland and abroad,
the main structural members being of oak. During the last
ten years time, the problem of fungi in wooden vessels, very
costly repairs and the general increases in the size of Icelandic
fishing vessels, has had the result that new vessels are being
built more and more of steel. Many Icelandic wooden ship-
yards are now starting the building of all-welded steel ships
instead of wood. It has been found that after the changing
over there is still sufficient work for the wooden ship-builders
in a small steel shipyard. Craftsmen in wood make the
moulding loftwork, erection and lining up of the steel ships,
and there is a considerable amount of woodwork in every
steel vessel.
They have built even very small boats of steel, down to
33ft (10m) decked vessels, but with increase in size, all-
welded steel has more advantages over wood construction.
Above 80 to 100 GT the all-welded steel vessel is very much
superior to the wooden vessel.
Although not believing in the future of larger wooden
vessels, Bardarson again expressed his thanks to Pedersen
for his excellent and very interesting paper. He was sure it
will be studied carefully by everyone concerned in the building
of smaller fishing vessels. He agreed with Pedersen's views
that new developments in wooden shipbuilding must be
found if wood is to survive the competition from other ship-
building materials.
Kilgore (USA) : In regard to metal versus wood in developing
regions, attention is called to the advanced fleet built in
Mexico in the past few years. The Mexicans would have had
sound reason for choosing predominantly steel construction.
Wood maintenance cheaper
Mines (Canada): The consensus of opinion in Eastern Canada
has always been that it is more economic to maintain steel
trawlers than wooden trawlers. During the past 20 years some
casual observations were made that led us to initiate a more
detailed study, The casual observations led us to believe that
wooden trawlers had less maintenance and fuel costs, but the
detailed data have revealed that this is true only in the over-
all average and that the cost varied considerably from vessel
to vessel and from year to year. This variation applied to
steel trawlers as well.
Three wooden and three steel trawlers were studied for
1963 and 1964 and the data are given in tables 7, 8 and 9.
These vessels have been selected as an average of the whole
fleet. In order to make the test as fair as possible, the largest
wooden vessels and the smaller steel vessels have been
selected for this purpose. The best estimates would indicate
that there are about 75 wooden trawlers over 100 ft (30.5 m)
and 50 steel trawlers over 115ft (35m) in the Province of
Nova Scotia. Wooden trawlers arc not generally, or for that
matter even rarely, built over 115 ft. This is due to the fact
that it is difficult to obtain timber of sufficient structural
strength to construct a wooden trawler of a greater length.
Jt could be well stated that the utilization of 3 wooden and
3 steel trawlers is an inadequate sample for a universe of
this size; but these are the vessels which have fished a full
year and under those conditions and with those stipulations
which make them conducive to a comparable study of this
nature.
Obviously two years of study are insufficient to arrive at
any substantial conclusions, but it is the hope to continue
these records for a further two or three years, at which time
the concept might be validated that maintenance and fuel
costs for vessels of steel and wood do not play as important a
[297]
TABLE 7
Comparative data on wooden versus steel trawlers, Nova Scotia:
(Canadian $1 -US $0.93)
1963
Wooden
trawlers
Steel trawlers
1
2
3
Average
Average
4
5
6
Year built and average age
1950
1957
1951
10.3
9.0
1956
1952
1954
Length (ft)
115
115
115
115
134
124
137
141
Construction Costs ($)
285,948
296,156
287,528
289,877
433,333
450,000
420,000
433,000
Number of trips
30
31
26
29
27
26
27
27
Days at sea
262
266
227
252
259
265
257
255
Hours fishing ,
2,874
3,634
2,317
2,941
2,431
2,349
2,706
2,239
Number of crew
16-18
14-18
15-18
14-18
15-17
15-17
14-17
16-17
Landed weight (Ib) .
3,745,776
4,808,520
3,050,140
3,868,145
4,426,122
4,107,941
4,357,100
4,813,325
Landed value ($)
189,816
254,007
145,792
196,538
170,459
151,017
168,440
191,920
Hull repairs
9,018
8,985
9,849
9,284
11,074
7,880
10,689
14,651
Engine repairs .
8,170
3,629
8,993
6,931
11,836
13,598
16,460
17,285
Marine insurance
7,364
7,967
7,369
7,567
12,045
12,824
9,862
13,449
Fuel, oil, grease
20,984
18,725
14,753
18,154
19,852
17,291
20,225
22,041
Total receipts .
191,316
254,007
145,792
197,038
170,459
151,017
168,440
191,920
Total expenditures .
83,020
91,276
82,615
85,637
107,178
96,509
106,372
118,653
Net cash return to labour
and to capital
108,296
162,731
63,177
111,401
63,281
54,508
62,068
73,267
Net cash: crew share
72,188
97,640
52,931
74,253
63,275
55,716
61,907
72,203
boat share
36,108
65,091
10,246
37,148
6
-1,208
161
1,064
Less depreciation
'-21,446
-19,232
-21,565
-20,748
-32,500
- 33,750
-31,500
-32,250
Net earnings of boat
14,661
45,859
11,319
16,400
-32,494
-34,958
31,339
-31,186
TABLE 8
Comparative data on wooden versus steel trawlers, Nova Scotia: 1964
Canadian $1 -US $0.93)
Wooden trawlers
Steel trawlers
J
2
3
Average
Average
4
.5
6
Year built and average age .
1950
1957
1951
11.3
10.0
1956
1952
1954
Length (ft)
115
115
115
115
134
124
137
141
Construction costs ($)
285,948
296,156
287,528
289,877
433,333
450,000
420,000
430,000
Number of trips
30
30
30
30
24.6
25
24
25
Days at sea
250
265
258
258
240
246
236
238
Hours fishing .
2,681
3,547
2,808
—
—
2,259
—
—
Number of crew
14-18
16-18
15-18
15-18
12-17
12-17
12-17
12-17
Landed weight (Ib) .
3,863,316
4,733,118
3,605,019
4,067,151
3,548,866
2,824,844
3,475,667
4,346,088
Landed value ($)
201,716
259,804
190,992
217,504
136,306
105,516
131,185
172,217
Hull repairs
9,568
9,616
11,538
10,241
8,093
6,913
7,738
9,627
Engine repairs .
7,945
7,658
17,405
11,003
17,959
15,883
16,017
21,976
Marine insurance
7,364
7,967
7,368
7,566
10,665
11,281
8,675
12,139
Fuel, oil, grease
24,240
19,092
28,016
23,783
22,700
21,724
20,370
26,007
Total receipts .
201,716
259,804
190,992
217,504
136,306
105,516
131,185
172,217
Total expenditures .
94,090
91,335
111,522
98,982
115,387
111,379
112,017
122,765
Net cash return to labour
and to capital
107,626
168,469
79,470
118,522
23,919
-5,863
19,168
49,452
Net cash: crew share
76,521
99,890
70,956
82,456
49,190
36,424
46,922
64,225
boat share
31,105
68,579
8,514
36,066
-24,271
-42,287
-27,754
-14,773
Less depreciation
-21.446
-19,232
-21,565
-20,748
-32,500
-33,750
-31,500
-32,250
Net earnings of boat
9,659
49,347
-13,051
15,318
-6J,771
-76,037
-59,254
-47,023
place in costs of operation as might have been the original
thinking.
Over the two-year period the average wooden trawler spent
255 days at sea, landed 3,967,648 Ib (1,800 ton) of fish valued
at £68,000 (C$207,021). The steel trawlers, on the average,
spent 250 days at sea, landed 3,987,494 Ib of fish, about the
same amount, but only valued at £51,000 (C$153,382) see
table 9. The higher-average landed value for the quantity
landed by the wooden trawlers when compared with that of
steel trawlers is accounted for mainly by the higher average
prices received. The species mix was also much better for
the wooden trawlers since approximately 40 per cent of catches
were obtained on George's Bank for which a premium price
is paid.
[298]
Comparative data on woodei
(Averages j(
TABLE 9
ers, Nova Scotia
or 1963 and 1964)
Wooden trawlers
Steel trawlers
1963
1964
Average
Average
1963
1964
Age ....
10.3
11.3
10.8
9.5
9.0
10.0
Length (ft)
115
115
115
134
134
134
Construction costs ($)
289,877
289,877
289,877
433,333
433,333
433,333
Number of trips
29
30
29.5
25.8
27
24.6
Days at sea
252
258
255
250
259
240
Hours fishing .
2,941
—
—
—
2,431
Number of crew
14-18
15-18
14-18
14-17
15-17
12-17
Landed weight (Ib) .
3,868,145
4,067,151
3,967,648
3,987,494
4,426,122
3,548,866
Landed value ($)
196,538
217,504
207,021
153,382
170,459
136,306
Hull repairs
9,284
10,241
9,762
9,583
11,074
8.093
Engine repairs .
6,931
11,003
8.967
14,897
11,836
17,959
Marine insurance
7,567
7,566
7,566
11,355
12,045
10,665
Fuel, oil, grease
18,154
23,783
20,968
21,276
19,852
22,700
Total receipts .
197,038
217,504
207,271
153,382
170,459
136,306
Total expenditures .
85,637
98,982
92,309
112,282
107,178
115,387
Net cash return to labour
and capital .
111,401
118,522
114,962
42,050
63,281
20,919
Net cash: crew share
74,253
82,456
78,354
56,232
63,275
49,190
boat share
37,148
36,066
36,607
14,138
6
28,271
Less depreciation
-20,748
-20,748
-20,748
- 32,500
32,500
- 32,500
Net earnings of boat
16,400
15,318
15,859
46,632
-32,494
60,771
Economic factors listed
The cost differential between the wooden and steel trawlers
regarding hull repairs is negligible, as is also the case with
fuel, oil and grease; on the other hand engine repairs for
the steel trawlers were approximately 65 per cent higher than
for the wooden trawlers, and marine insurance was 50 per
cent higher for the steel trawlers (see table 8).
The main difference between wooden and steel trawlers
lies in the capital investment or outlay which, on the average,
was £96,000 (C$289,877) and £144,000 (C$433,333) respec-
tively. There are no comparative figures available on the life
span of wooden versus steel trawlers but there are still a few
wooden trawlers in operation after 20 years of service. Most
of the older wooden vessels, the Lunenburg Schooner for
example, have become obsolete and are now being used for
coastal freighting and other commercial operations outside
the province, therefore, making it inconvenient to maintain
records of their life span.
A final point concerns the general impressions of sea-
kindliness which involves the period of roll and mount of
pitching. In this part of the world the period of roll is re-
stricted because the boats have to be stiff enough to take care
of the icing and sea conditions. Therefore, it can be said that
the boats are relatively stiff. The other factor involved
concerns pitching which can cause a great deal of discomfort
in heavy rigid structures without resilience.
For this reason a wooden ship has an easier motion and
caters more to sea-legs. This is borne out by the fact that
most of Nova Scotia's older and more reliable skippers
prefer to sail in wooden ships.
Size of boat decides the material
Rebollo (Spain): Generally speaking, boats up to 82 ft (25 m)
length are built of wood and larger boats of steel in Spain.
In this contribution, only wooden boats (since the discussion
is limited to under 100 GT) will be considered. Broadly,
when a boat is built, e.g. between 62 and 82 ft (19 and 25 m)
length, three of four templates offering three or four varia-
tions in beam and depth are available. Length is decided, for
the most part, by the template actually chosen. The tem-
plates serve only to shape the hull and are subsequently dis-
mantled for use with other boats. In this way the builder
greatly simplifies his task and needs only two or three simple
machines to work the wood. In addition to, and independent
of, the shipyard, there are assembly workshops where engine,
tubing, pumps etc. may also be assembled. The deck houses
were formerly made of steel but in recent years some light
(e.g. aluminium magnesium) alloy has been used. The plans
of the deck houses are submitted for approval. Special
attention is paid to how they are fastened to the deck, and to
ensuring that the fastenings arc strong enough. The com-
panionways used to be made of wood but, since a number of
boats were lost due to damage caused to the latter, and
consequent flooding through these openings, they are now for
the most part built of steel and strongly secured to the deck.
Author's reply
Pedersen (Denmark): Potter in his excellent contribution gave
a clear picture of the difference between non-engineering and
engineering structures. Fyson in his paper, stressed the many
technical and economical advantages of series-produced
vessels over those individually-built. Large-sized glue-
laminated members and sheet-panels seem to fit extremely
well into this pattern, especially if simple hullforms are
accepted by customers. Centralized production of such
standard-elements seems to be the only possibility of obtain-
ing products of adequate quality.
Since 1939 a great deal of information on glue-laminated
products has been issued by Forest Products Laboratories
the world over (Wilson, 1939; Freas, 1950; Schniewind, 1964).
Production of glue-laminated members, plywood, etc.*
demand "laboratory conditions". An exact procedure and
strict schedule must be followed.
Standard running tests normally used are the block-shear,
and delamination-tests. In the dclamination-test, 15 to 20
years exterior conditions are simulated in order to find
percentage failure of glue-line after this period. These
[299]
accelerated delamination test results are compared with long-
term tests under service conditions. In Germany, Switzerland,
Sweden and Norway, glue-laminated wooden structures were
introduced in 1920. Although only the non-water resistant
casein glues were used, these structures have now given 40
years of perfect service, even under most adverse conditions
(Wilson, 1939; Selbo and Gronvold, 1963).
Ullev&lseter is correct when saying that one of the major
advantages of the lamination technique is, that each individual
lamellae can be 100 per cent protected before assembly,
resulting in a 100 per cent safe wood product. Gluing of
salt-treated Norway- or Scotch-pine (Pinus sylvestris) gives
no trouble (Selbo and Gronvold, 1956; Selbo, 1957; Truax
et al, 1953; Selbo, 1964). Rasmussen's fear of fungi-attacks in
heartwood of treated glue-laminated members is unfounded.
However, if a 100 per cent protected product is wanted,
species belonging to class 4 in table 2, treated with copper-
chrom-arsen-salts or similar efficient preservatives should be
used.
Haavaldsen's information is received with thanks, as one of
the major objections against the use of copper-chromarsen-
salts for wood protection in fishing vessels is now invalid.
Good average properties of laminated wood
Glued laminated wood is a refined wood product with
better average properties than natural wood. Because of
eliminated risk from fungi, insect and other biological attacks,
less checking and shrinkage, etc., glue-laminated members
will give more trouble-free service than members made from
unprotected members of natural green wood. This will be
especially true under adverse temperature and humidity
conditions, as proved by Lindblom (1963) in arctic glue-
laminated wooden-ships. A plan which could quickly raise
the status of wooden boat building in developing areas, taking
Greenland and Denmark as an example, can be proposed as
follows: Several well-established factories for glue-laminated
wood exist in Denmark. Sets of glue-laminated members and
other standard elements could be shipped to Greenland and
assembled there, using trained local labour. Greenland
fishermen and boat builders could develop types and sizes of
vessels suited to Greenland conditions, instead of being
dependent on vessels as used and built in Denmark.
As stated by many discussers, weight of light ship should
be kept as small as possible in order to increase pay load.
Therefore, materials with high specific strength-values should
be given first priority.
When comparing scantlings of traditional wooden fishing
boats on an equal weight/strength-basis, the results seem
surprising. As Sutherland stated, the value of such an
investigation is limited until basic strength-requirements are
determined. For relative comparisons, however, the figures
can be used.
As might be expected, the figures referring to glue-laminated
vessels compare most favourably in respect of the ratios
compared.
Mines' comparisons, based on three steel- and three
traditional-built wooden vessels are valuable. Those in-
vestigations, however, do not confirm the commonly accepted
thinking among naval architects that great differences in
maintenance- and running-costs occur, when comparing
representative vessels built from different materials. In
Mines' opinion, the main difference lies in the capital invest-
ment, if the same lifetime for the vessels compared is assumed.
If this conclusion is correct, vessels should be built as in-
expensively as possible, regardless of materials used.
Neglect of good practices
Bardarson mentioned that traditional-built wooden boats
are being replaced by steel vessels, due to very costly repairs
of fungi-attacked wooden vessels. In this case maintenance-
costs on wooden vessels are very high and lifetime very short.
This, however, need not mean that steel is better than wood,
rather that wood was used in a wrong way, i.e., placed in green
condition in very compact structures where growth-conditions
for wood-destroying fungi are favourable.
In all reports on fungi-attacks in wooden vessels from
different countries, there seems to be a general trend, namely
a rapid increase in the number of attacks in the last 10 to 20
years only. The explanation may be that vital assumptions
and unwritten rules accepted formerly, have now been
forgotten.
Requirements for selection, preparation, etc., of wood
before installation, as given in the old rules, are only of a
very general nature and interpreted in a haphazard way by
the individual builders.
Due to the minimum steel plate thickness of •& in (7 mm)
required by reason of corrosion, smaller steel-vessels are
excessively heavy and consequently uneconomical. Kilgore
referred to the large fleet of smaller steel vessels built in
Mexico. It would be valuable to know why the Mexicans have
chosen steel for other materials, and what their experiences
are with these vessels.
Excessive weight causes waste
The important question on influence of weight upon
efficiency and economy for different sizes and types of
vessels should be taken up as a separate point at a future
congress.
As Retvig stated, and mentioned by Rasmussen in his
paper, and being well-known since the Second FAO Fishing
Boat Congress in 1959, the Danish rules for wooden fishing
boats demand excessively heavy scantlings, resulting in
expensive and heavy boats.
Unnecessary amounts of expensive boat building timber
are used. It is the fishermen in the first instance who must
pay for the timber and for the transport of this unnecessary
and expensive ballast, but in the end the housewives have to
pay for more expensive fish.
Every year millions of kroner are wasted due to overheavy
boats. Danish fishermen already have paid great bills in
human lives and material due to disasters which may be
traced back to undetected fungi attacks in the unprotected
wood-members.
(Editor's Note: The Danish rules for the construction of
wooden fishing vessels were officially cancelled on 6 December,
1966).
Chapelle and Thiberge remarked that a true picture on the
loads acting on a hull in service is difficult to obtain. Mow-
ever, thanks to work being done by classification-societies,
technical universities, etc., data are being collected, treated and
crystallized into strength-criteria for main structural members
of ship- and boat-structures, thus giving the engineer a
rational design-base from which to work.
The final goal— a rational design procedure— seems to be
within reach in not too many years.
ALUMINIUM AND ITS USE IN FISHING BOATS
Whittemore (USA): Me had designed and constructed a
group of the aluminium gillnetters referred to by Leveau.
The strength to weight ratios indicated of 1 8,000 lb/in2
(1,250 kg/cm2) for aluminium versus 7,000 lb/in2 (500 kg/cm2)
for a steel structure implies that the weight of an aluminium
structure would be approximately 38 per cent of a steel
structure. This appears to be a little optimistic since it
generally has been recommended that for a welded structure,
the scantlings and thicknesses of the aluminium structure
[300]
should be at least 50 per cent greater than that of the equiva-
lent steel structure. This would result in the weight of an
aluminium structure being approximately 50 to 52 per cent
of the weight of a steel structure. This same ratio is indicated
in fig 1 of Leveau's paper for Alloy 5086-H32.
Any shipyard with experience in construction of steel
vessels which is contemplating entering the aluminium boat
construction field, should proceed with caution. Aluminium
does not behave the same as steel in a welded fabrication
and therefore theories and practices which were used in the
construction of steel hulls are not directly applicable to
aluminium fabrication. For example, aluminium does not
have the same shrinkage characteristics as steel when welded.
A steel hull would show a great deal of distortion in the
plating if all the interior framing were continuously welded,
but can be kept relatively smooth by using intermittent
welding. Aluminium hull structures on the other hand show
little distortion when the framing is welded continuously and
greater distortion when heavy intermittent welds are used.
With the availability of the high-speed continuous-feed
welding machines, it is possible to weld stiflfencrs with a small
continuous bead for the same or less cost as the heavier
intermittent weld of the same total strength.
The smaller continuous welds are preferred over the
heavier intermittent welds in areas subject to vibration and
impact loads. Serious cracking problems have developed in
aluminium plating subject to vibration and impact loads
when intermittent welding was used.
The cracks generally started at the ends of the intermittent
welds, in the heat-affected zone. The ends of the intermittent
welds form hard spots in the middle of the plating around
which the plating is free to move, relatively. However, by
continuously welding the stiffeners to the plating in these
areas of high loads, the cracking problems were completely
eliminated. Hard spots arc eliminated and the reduction in
strength at the heat-affected zone in the parent metal is
decreased using the smaller continuous weld at a higher rate
of speed.
Extruded panels prove helpful
In recent years, special extruded aluminium panels have
been available from the aluminium manufacturers with the
stiffeners forming an integral part of the plating. This makes
an excellent structural system for a hull subject to vibration
and impact loads since the intermittent welds with their hard
spots and heat-affected zones are diminished. These panels
have been used in vessels subject to high impact loads such
as hydrofoil panels.
Hard spots of any kind arc to be avoided in the hull
plating. Stiffeners should not terminate in the middle of
plating panels. Brackets for foundation structures should be
extended to the nearest panel stiffeners. The ends of bulkhead
stiffeners should not be simply welded to the shell plating or
tank top plating. The ends of such stiffeners should either be
stopped just short of the shell plate with a diagonal trim to
permit freedom of movement or else bracketed to a shell
stiffener. Brackets connecting longitudinal shell framing at
bulkheads should be carried to bulkhead stiffeners or elimi-
nated using a boundary stiffener or doubler plate at the
inboard edge of the shell stiffeners.
Most of the above precautions are not necessary in steel
hull structures for the type of vessels be in:? discussed here,
although some of these precautions are applied in large steel
tank ships.
The 57ft (17.4m) all-aluminium purse seiner vessel
referred to by Leveau was faster than similar size wooden
and steel seiners, but nowhere near as fast as he has indicated.
The vessel was originally equipped with a 470 continuous hp
engine, which is about double that normally installed in a
vessel of this size and service. With a ready-for-sea displace-
ment including normal gear and fuel of about 70 per cent of
that of a similar steel vessel, the aluminium seiner achieved a
speed of about 40 per cent greater than that of a normal steel
vessel, as would be expected. The 24 and 18 knot speeds
referred to by Leveau were what was originally hoped for
prior to construction.
Where speed without cargo or draft restrictions with cargo
are important, aluminium hulls are an effective answer,
provided experienced aluminium repair facilities are in the
operating vicinity or the owner acquires aluminium welding
equipment and trains personnel to use it.
Importance of technical skill
Allen (USA): As a manufacturer of a number of aluminium
boats, some of which appear in Leveau's paper, and a
shipyard which has maintained most other aluminium vessels
in the area, Allen did not feel that Leveau's paper gives
proper significance to the problems which persist in design
and construction for the elimination of cracks. Since the
principal use of aluminium in small boats is in high-speed
vessels, the problems are further aggravated, particularly in
the stern structure which by the nature of design is usually
quite flat. Builders contemplating building aluminium
vessels for the first time should take advantage of the technical
help offered by experienced naval architects and aluminium
companies.
Aluminium should not be encouraged in areas where
welding equipment and materials and skilled personnel are
not readily available. The repairs of cracks is not just a
matter of welding, but usually demands a revision of structure.
Jn the stern of high speed vessels, this more often than not
occurs in fuel tanks.
As a further observation of aluminium vessels, which have
been in service even with knowledgable owners, there is a
tendency to ignore the galvanic corrosion of dissimilar
metals in mounting new fittings or changing deck machinery
With the most careful use of technical assistance and the
greatest care in construction with the most qualified workmen
in USA, it is not possible to insure complete elimination of
cracking (sometimes in the most unexplained locations).
Although almost all of aluminium boats have developed
bothersome cracks, the most serious cracking problems
affecting safety of vessels have occurred in wood vessels
50 to 90 ft (15 to 27 m) long, using full hold capacity alumi-
nium sea water tanks to carry live king crabs in Alaska.
British practice cited
Lee (UK): Leveau makes a very good case for the use of
aluminium alloys in fishing boats. Practice in the UK differs
in respect of the following:
Antifouling composition: lead based paints arc not used on
aluminium structures in marine conditions as corrosion
would be serious in the absence of an effective barrier.
Mechanical fastenings: stainless steel is prone to crevice
corrosion when continuously immersed in sea- water. Corro-
sion pitting may arise, even when not immersed, from chloride
contaminated moisture. Galvanic protection, e.g. electro-
deposited zinc coaling, is necessary.
Whsre aluminium alloy is joined to steel the fastening is of
steel, not aluminium.
It should be noted that aluminium is subject to fungal
attack in the presence of kerosene-type fuels and water. Fuel
tanks at least should be suitably protected. The aluminium
is pretreated with Alochrome 1200 (IC1 Paints, Slough) and
coated with an epoxy resin; a polysulphide rubber PR 1422
[301]
(British Paints) is used for sealing all joints and for giving an
overall finishing coat.
Japanese details
Takehana (Japan): Some examples of aluminium ships built
in Japan are:
1. Japanese Coast Guard Patrol Boat: Daio (1949)
2. same: Arakaze (1954), this is the first ship made of
Al-Mg-Mn (A2P7)
3. Superstructures of Escort Ship: Akebono (1955)
weight of aluminium used is 40 tons
4. Torpedo Boat No. 7, 8, 10 (1957-1962) displacement
120 tons, weight of aluminium hull 50 tons, speed
50 knots
5. Superstructures of Canadian Boxide Carrier Sun-
walker- (1957) weight of aluminium 200 tons
6. Tuna Fishing Catcher Boat (No. 8 Akebono) (1956)
Length overall . 51 ft (15.5 m)
Length BPP . 46 ft (14m)
Breadth . . 11. 8 ft (3.6m)
Depth . . 5.25 ft (1.6m)
Thickness of shell
plating . . fff in (5 mm)
Thickness of deck
plating . . J in (3 mm)
Frame . . 0.16 x6x 1.6 in (4 x 150x40 mm)
Frame spacing . 2.6 ft (0.8 m)
Deck beam . 0. 1 6 x 4.7 x 1 .6 in (4 x 1 20 x 40
mm)
Hull weight . about 8 tons (corresponding
weights for wood 13 tons,
steel 1 1 tons, FRP 7.5 tons)
Recent increase in USA
MacLear (USA) : From 1950 to 1960 relatively few aluminium
boats were built in the USA. From 1960 to 1965 there has
been a substantial increase and at present most US aluminium
shipyards are at 100 per cent capacity. The early difficulties
have mainly been eliminated and several yards that once built
in wood or steel now construct in aluminium exclusively,
or primarily. Referring to cost, the following comparisons
are interesting. From the same US yard, double planked
wooden construction is quoted as costing $2.50 per Ib and for
aluminium construction $3.00 per Ib based on a completely
outfitted vessel. This gives a difference in price of 20 per
cent, but because of the weight saving in aluminium, the
figure is more like 15 per cent.
Another quotation from Germany taking steel construc-
tion as the datum, places double planked wood cost 2 per
cent higher and aluminium construction 1 1 per cent higher.
This gap is lower than many realize. As far as fishing vessels
are concerned, it must be remembered that the extra capacity
and earning power might well offset the extra constructional
costs.
Temperature and conductivity
Pedersen (Denmark): Aluminium has excellent electrical and
heat conductivity properties, consequently poor insulation
properties. (See table 6 in Verveij's paper).
Could Leveau answer the following questions :
• How much does the necessary installment of insulation
material in an aluminium hull affect the building
costs?
• Can an aluminium hull be safely protected from the
rapid rise in temperature in the material in case of a
fire, in order to avoid an early collapse of the struc-
ture?
Toullec (France): In reply to Pedersen: Since aluminium has
a very high conductivity it transmits to the boat as a whole
the temperature of the water, which exerts a moderating
influence and one making for a high degree of comfort
without a lot of insulation being necessary.
Pedersen (Denmark): What if temperatures are constant,
arctic or tropic? Would it not then be necessary to insulate?
Problem of impact loadings
Nickum (USA): Typical views of deck house framing and
plating would be more helpful if frame spacing had been
shown. Tabular values of allowable deflection for decks,
particularly of small vessels which have only personnel loads
involved might also be helpful in preventing over-designing
and putting in too much material. Also the data on ultimate
strength of materials would be more useful to the designer
of welded structures if values in the "as welded" condition
were included, or at least a statement that in designing for
welded structures the strength in the fully annealed condition
should apply.
Recent experience in USA, particularly in the development
of structure for hydrofoils which are subject to high impact
loadings, show definite advantages in the use of extruded
aluminium panels. These extrusions can be obtained with
"T" stiffeners extruded in place on the panels. They have
been obtained in widths up to 26 in (660mm) in width.
While the dies are very costly they are very definitely advan-
tageous in reducing weight.
Fig 28 is an example of how very thin skinned sections can
be used for heavy loadings by the use of haunches or elliptical
fillets in the material just next to the "T" stiffeners. This
particular section can take pressures up to 45 lb/in2
(3.15 kg/cm2) at the yield point of the material.
£0.32"
Fig 28
Nickum endorsed Allen's warning that competent people
and procedures must be used for working aluminium.
Shrinkage is often a serious problem to an inexperienced
operator. An example is a 210ft (64m) vessel now under
construction which shrank a total of 10J in (270 mm) during
the construction, caused by lack of allowance for shrinking
and poor welding procedures.
Special care has to be taken in the layout of the framing
so that the welding head can reach all parts of the structure.
Special care should also be taken in the use of aluminium
to see that it is not subjected to fire. Because of its low
melting point, a fire next to one of the main structural mem-
bers can very seriously reduce the vessel's strength. On a
Norwegian vessel which recently burned off the US Pacific
Coast, no aluminium fittings, including the deck house, the
funnel, the life boats and all inclined ladders, were left on one
side of the ship which had been subjected to the fire.
Corrosion factor
Verweij (Netherlands): Aluminium is certainly suitable for
many applications. However, especially in sea water or at
[302]
the seaside, one has to be aware of unexpected difficulties
due to galvanic corrosion.
This danger will be greater if used in areas where people
understand less of this corrosive action. Even with anti-
fouling paints, one has to be very careful. In general, painting
of aluminium requires minute attention.
Whereas impact strength of undamaged material is good,
this is not the case with the notched impact resistance.
Therefore, a beginning of a crack will easily go on.
In great contrast to this is the behaviour of fibreglass,
where the notched impact resistance is nearly as great as the
unnotched impact resistance. Also the absolute values for
fibreglass are very high.
Construction of aluminium boats requires greater tech-
nical knowledge and skill than is required for any other
material.
Protection from ice
Petersen (Denmark): There is another purpose for aluminium
in Scandinavia and Greenland namely to preserve wooden
fishing boats during navigation in icefilled waters and specially
take care of the planks in the waterline bell. In former days
galvanized iron sheets were used or in the oldest day copper
plates. Today copper is very expensive and galvanized iron
has a very short life time and it became natural to test
aluminium. For boats built for fishing in Greenland, where
navigation in ice is very common in several months of the
year, A to ,'{$ in (1.5 to 5 mm) aluminium plates, 1.5 ft (0.5 m)
over load waterline and 1.5 ft (0.5 m) below light waterline
are used. Before the sheets are fastened the planking is
painted with neutral asphalt after the caulking has been
finished. Galvanized 1 in (25 mm) spikes are set at a distance
of about J in (20 mm) along the edges.
The quality is salt water resistant aluminium with hardness
J H. (Al-Mg). Different firms have useable alloys. Alumi-
nium for this purpose has a lifetime about three to four years
against about two years for galvanized iron sheets.
Troup (UK): To a naval architect engaged with design of
aluminium craft, Leveau's paper is of great value. When a
UK shipyard first began to use aluminium, they found that
they had considerable difficulty in riveting. The rivets were
very easily overworked, and on some occasions the heads
burst off with some startling results.
Developing countries should not use aluminium without the
advice of experts. Furthermore one cannot use steel workers!
They are much too heavy-handed, so if one wishes to train
people to work aluminium use sheet-metal workers.
Some technical points
Leathard (UK): Aluminium has a comparatively low impact
value. The value given by Leveau is measured with stresses
only in one direction. It should be corrected as the value is
not the same for plates stressed in two or three directions.
The section shown in fig 2 of Leveau's paper stiffener
section is standard in USA. It was to a large extent used in
aluminium superstructure in Bergensfjord built in UK. This
stiffener serves a two fold purpose. It gives a better location
of the welds of the stiffener to the plate and at the same time
acts as a backing strip for the butt-weld of the plate. The
design of aluminium structures requires expert advice. This
is an example of the right way to use such a section.
Table 8 of Leaveau's paper shows several different alumi-
nium alloys. This could possibly create confusion and UK
has standardized a rather small number of sea water resistant
alloys.
Toullec (France): Leveau's excellent paper is worth several
comments but time only permits one, concerning the essential
quality of this material, namely its lightness. The fact that
trawlers must have enough immersed hull surface to counter-
balance the drag of the trawl seems to me to be incompatible
with the reduction in underwater body needed for high
speeds. Is there any information on vessels currently in
operation? Careful studies should lead to a form capable of
reconciling the two needs.
Nickum (USA): Concerning reducing the number of alloys,
it should not be forgotten that aluminium is a much more
sophisticated material than steel, for example the weldability
varies between the different alloys. The alloy 54 56 is very
weldable while the alloy 60 61 which has a higher strength
should not be welded. It should be remembered that the
alloy 54 56 has its yield strength considerably reduced when
welded. When welded the strength qualities go back to the
unannealed condition and one has to take these corrected
figures into the strength calculation. One also has to take into
consideration the welding in different axes, especially when
designing close to the yield strength of the material.
Overcoming stubborn prejudices
Kilgore (USA): The aluminium producers have come into
the boatbuilding and shipbuilding market aggressively only
a few years ago, and have had to deal with some stubborn
prejudices before they could even begin talking the virtues of
their product. The first of these prejudices is the notion that
aluminium corrodes in salt water. Every day one still en-
counters that old notion. The second is that welding alumi-
nium is a tricky business, reserved only for highly trained
technicians.
The aluminium-magnesium alloys do not corrode to any
significant extent. Skill in welding aluminium properly does
not take more training than skill in proper welding of steel.
It is true that both these statements deserve some qualifica-
tion. Aluminium is lower in the electromotive scale than iron,
and hence more care is necessary in exposing dissimilar
metals. Aluminium welding requires procedures different
than for steel. But neither of these reservations adds significant-
ly to the cost of using the product.
In comparing the two metals, people usually leave out the
corrosion allowance which must be added to the required
thickness of exposed steel. This varies with the environment,
but after computing the thickness for strength and stiffness
one always has to add enough steel so that in a given number
of years sufficient thickness will remain. This is not necessary
with the aluminium-magnesium alloys.
Another factor in the value of an investment is the probable
salvage value at the end of useful life. The salvage value of a
steel boat is at present practically nothing, even if it were in
first class condition. Scrap aluminium is now bringing over
£7 ($20) per ton. Still another saving is the saving in
haul-outs.
Taking all factors into consideration, and not forgetting the
greater operating profitability through reduced weight, the
aluminium fishing vessel is generally the best bargain the
fisherman can find. This is not true for those vessels where
the hull is the major part of investment. But in fishing rigs of
the common sizes, the hull alone represents only a part of the
investment, and a long list of other items cost the same no
matter what the hull may be: refrigeration system, propulsive
system, steering system, ground tackle, accommodations,
electronic gear, rigging and winches, navigational equipment,
fire-fighting and lifesaving requirements, general stores, and
the fishing gear itself.
There is one objection to aluminium: with simplified
construction, even the smallest shipyard can bid on the
construction of a fairly large steel hull, subject chiefly to
[303]
his ability to launch it. The reason is that for shaping and
bending heat can be used instead of heavy and expensive
machinery. It is quite amazing what a workman with only
a torch burning liquified petroleum gas can do with a piece
of steel. The labour costs a little more than power shaping,
but when the job is done the yard does not have its capital
tied up in costly machinery. Now one doesn't dare play a
torch on an aluminium plate. So how does one make it fit?
Big potential for small craft
Colvin (USA): There is, without a doubt, a great potential
for aluminium in small craft, and especially in small fishing
vessels; however, in the past decade there has been a great
deal of misleading information put forth to favour aluminium
over steel construction. There are, of course, instances where
aluminium surpasses steel, but there are many others where
the high cost of aluminium construction does not compare
favourably with steel, cannot be justified, and would be a
detriment to progressive fishing and boatbuilding if it were
forced upon the fishermen.
Levcau has been very instrumental in the USA in putting
forth useful information to the naval architects for their
guidance in the design of aluminium vessels. The data and
cross-comparison tables that he has formulated and pub-
lished on various occasions have done a great deal to ease the
burden of seeking pertinent information regarding alumi-
nium construction. However, it would be appropriate at this
time to point out several items which should be carefully
thought over by designers as well as builders in arriving at a
solution to a given problem. For a number of years, a high
corrosion resistant steel has been available in USA with a
tensile strength of 70,000 lb/in2 (5,000 kg/cm2) minimum and
a yield point of 50,000 lb/in2 (3,500 kg/cm2) minimum, with a
shearing strength of 37,500 lb/in2 (2,650 kg/cm2) and an
endurance limit of 42,000 lb/in2 (3,000 kg/cm2) against the
28,000 lb/in2 (2,000 kg/cm2) of this mild steel. Basing the
carbon steel on a minimum yield of 33,000 lb/in2 (2,300
kg/cm2) and a working stress of 18,000 lb/in2 (1,300 kg/cm2)
the high strength steel with a minimum yield of 50,000 lb/in2
(3,500 kg/cm2) would be 18,000 times 50,000/33,000-
27,270 lb/in2 (1,900 kg/cm2) or a ratio of yield points of
1.515 or, say, 1.50. Yet the cost of high tensile steel is only
about 50 per cent more than mild steel. Since the weight ratio
for tension members is inversely proportioned to the yield
points of the two, then 33,000/50,000 =.66. Using high tensile
only for the shell plating and decks, and assuming that the
shell and decks are 68 per cent of the total hull steel, and the
savings by reduced scantlings of the shell by weight is then
34 per cent net on the shell, or a hull with 78 per cent of the
total weight of mild steel, a saving of 22 per cent would
result, or about one-half the weight saved by the use of all-
aluminium construction at an increase in cost of less than
1 per cent of the cost of mild steel.
Comparative strengths
A very thorough examination of the strength of aluminium
versus steel indicates that the thickness of aluminium must
be H to 2 times the thickness of steel for the same stiffness
or the same strength, which gives a saving, if averaged out, of
44 per cent on steel weight for mild steel and 22 per cent for
the high tensile steel; yet the cost of the aluminium structure
over the mild steel structure is four times as much!
Leveau has correctly shown the 56 per cent additional
hull and deck house material cost, but has lumped it in with
the machinery and outfit, which hides the true cost of the
aluminium hull. As it is interpolated downwards into small
fishing vessels of say five to 20 tons displacement where the
hull cost and the machinery cost are about equal, the figures
differ from those for the larger vessels, To the fisherman who
is spending, say, £11,500 ($32,000) of which £5,750 ($16,000)
is in the hull and £5,750 ($16,000) is in the machinery and
outfit, the material cost of the steel would be roughly £715
($2,000) and the equivalent cost of the aluminium would be
£2,850 ($8,000) or a difference of £2,135 ($6,000), or 18.75
per cent of the total delivered hull cost and 37.5 per cent of the
bare hull cost. Going still further, since probably borrowing
the greater portion of the money involved, the additional
£2,135 ($6,000) on a 10-year loan at 6 per cent simple interest
would raise the figure to £3,400 ($9,600). This is indeed a very
hard thing to sell, especially if the fishing operations are, as
they are in many instances, on a marginal basis to begin with.
When preparing identical designs for steel and aluminium,
it was found that cost wise it would be advantageous to use
the same engine, regardless of the hull that was built. The
weight difference amounted to about 2J tons, and yet there
was less than a knot (8 per cent) difference in their cruising
speeds when speed was of minor importance.
Colvin heartily concurred with Leveau that the fabrication
of aluminium is certainly not any more difficult than steel,
and in many instances is probably easier and simpler than in
steel ; however, the difference in weight becomes a very minor
problem in the handling of large plates in the size of vessels
under consideration.
Coatings protect against corrosion
Almost all of the classification societies at the present time
will allow substantial reductions in shell plating if the shell
is to be coated with the inorganic zinc silicate compounds
that are now available to the marine industry. This only
further reduces hull weight and at the same time indicates the
effectiveness of these coatings as protection against corrosion.
There arc a number of companies in USA that arc gua-
ranteeing over 15 years effective corrosion resistance of
these materials, and there should be no unusual main-
tenance problem to speak of in steel vessels. So now the
maintenance difference between aluminium and steel is
almost nil if both are to be painted. Even if the topsidcs are
not painted, most certainly any vessel that remains in salt
water for any period of time must have anli-fouling and must
be hauled once a year in the northern climates and twice a
year in southern climates for repainting. This is necessary on
aluminium boats just as on the steel.
One must be very careful in the design of aluminium
vessels since it is almost impossible if not impossible to
achieve 100 per cent strength joints through welding as can
be done very easily in steel. About the only material that can
be fully welded 100 per cent is aluminium in the annealed
condition. One may expect an efficiency of approximately
85 per cent with good welders. The cost of welding aluminium
is much higher than the cost of welding steel as far as the
deposit of weld metal is concerned; however, the speed of
welding reduces the labour involved so that apparent averages
in small yards seem to be about 1.2 to about 1.32 times the
cost of welding in steel.
The significant applications for aluminium where the
lighter weight is justified both by cost and by application is in
fishholds, penboards, deck houses, and in any small boat is
definitely advantageous. The aluminium becomes more
economic in fishing vessels that are to be used as beach boats
and are not permanently kept afloat which obviates the
necessity of any painting.
One must remember, especially in small craft, that the
scantlings of the steel, wood, or aluminium hulls are not
based on the strength requirements of the hull so much as on
the ease of working and the availability of the material. In
[304]
two experimental hulls which were based on oyster skiffs
26 ft (8 m) in length, they had a shell plating of .0747 in (1.9
mm). They proved to be extremely strong ( ^ of the deflection
of the wooden hulls), were lighter in weight than the wooden
counterparts, and were completely electrically welded. This
would normally be about one-half the scantlings that would
be considered desirable for ease of construction for a 26ft
hull.
"Real handbook for users"
Lindblom (Finland) gave thanks for a most comprehensive
paper — a real handbook for users of aluminium. Leveau's
paper was like "a letter in the mail", unexpectedly offering aid
when needed. Lindblom's firm is (probably) the only ship-
yard in Finland building round bilged boats in all-welded
aluminium. But, of course, they have encountered a whole lot
of problems, not yet solved. Nevertheless, there is a certain
definitely positive quality in this material the saving of
weight.
They have built and are building fast patrol boats for
Coastguard and Navy service. The bigger boats of this type
are built in steel and Lindblom had in vain tried to persuade
customers to use wood or light metal in lieu of steel.
This is best illustrated by an example. A steel built patrol
vessel of 115ft (36m) in length and 130 tons displacement
makes a speed of 26 knots with three 1,350 hp diesels given a
total of little over 4,000 hp together. Recently made calcula-
tions indicate that if this hull were to be built of light alloy, a
speed of about 24.5 knots would have been possible with
only two engines of the same size, totalling 2,700 hp as
against 4,000. The saving in cost would have been sub-
stantiated to say the least of it. Owing to saving in weight,
one engine complete with shafting, piping, cables etc., the
corresponding reduction of bunkers (fuel, lubricating oil,
etc.), the use of aluminium in a case like this seems to be not
only fully motivated, but in respect of money-saving im-
perative.
The reason why a lighter construction for hull was not
accepted by the buyer is supposed to be the ice. This is,
however, not correct. On a boat of this si/e, type and speed,
the propellers are by far the most vulnerable spots and not
the hull.
Lindblom had been experimenting with surface layers of
Dynel-Epoxy laminate on wooden shell and the results are
very encouraging and also studied the adhesion of this
laminate on aluminium.
This type of laminate has a very high resistance to abrasion.
How would it be to use such a laminate on aluminium hulls
as protection against the abrasive tear of this ice. if possible,
such a combination would greatly increase the possibility to
use aluminium.
Virtues listed for small craft
Hamlin (USA): Aluminium is the best material now available
from which to build small fishing vessels. It is lightweight,
strong, and highly resistant to deterioration. Barring some
sort of galvanic accident, an aluminium craft should last
almost indefinitely. Geerd Hendel, a naval architect of
Camden, Maine, USA, and a pioneer in aluminium construc-
tion, recently examined very carefully his 26 ft (8 m) alumi-
nium sloop built before World War 11. The only deterioration
he could discover was in a few rivets, easily replaced, and in
the faying surface between the hull and the wood fin keel
where some pitting was found due to holes in the insulating
bedding compound. This is a remarkable record for a boat
built of less suitable alloys than those available now, and a
boat which has been exposed to the constant wear and tear of
charter service most of its life.
Another argument for using aluminium in fishing vessels
will become increasingly strong as the demand for a higher
quality of landed fish is felt by ship owners. The ability of
maintaining a highly sanitary state on an aluminium craft, a
non-porous material which requires no paint, is non-toxic,
and will not rust, should serve increasingly as an incentive to
its use.
There is a question, however, about the use of aluminium
as a lining for fish holds, especially refrigerated ones. The
advantages, such as cleanliness and light weight, are obvious,
but it seems that the same qualities of heat transmission which
are an advantage in the rest of the vessel arc a disadvantage
in a fish hold, since aluminium will permit the flow of heat
to all parts of the fish hold lining much more rapidly than
another material will. It is perhaps significant in this connec-
tion that the latest Ross stern trawler will not have an
aluminium lining in its fish hold, according to news releases.
Cost must be reduced
McNcely (USA): Although Leveau's paper presented a
sound economic argument for greater use of aluminium in
fishing-vessel construction, considerable opposition will
remain until initial costs arc somewhat more competitive.
The new alloys are much stronger than the layman realizes
and quite resistant to salt-water corrosion. In this instance
McNcely referred to aluminium otter boards used with the
Cobb pelagic trawl and live-well tanks on Alaskan king crab
boats.
Foussat (France): Marine aluminium alloys have been used
in French fishing vessels since 1955. On the basis of informa-
tion received from Aluminium Fran^ais, aluminium has
been installed (a) on live-bait tanks and wheelhouses on tuna
clippers and, (b) on trawlers, pen boards, fish-hold stanchions
and other accessories. They are practically in mint condition
even where they were installed as long as ten years ago. All
these vessels have skiffs made of light alloys. Wheelhouses
are painted, but only for appearance sake. The live-bait
tanks are also painted because the fishermen think that the
sardine kept inside them are better off that way. The other
parts have never been painted.
The alloys used arc, in accordance with standard French
nomenclature, AG4 and AG5 for sheet metal and ASGM
for extrusions.
The installations of the 12 vessels in question, in particular
where the fish hold equipment is concerned, have proved to
be hard-wearing, so able to take knocks and so easy to
maintain that there can practically be no going back now.
Hygiene is the most important consideration with refrig-
erated fish holds with temperatures in the region of 32' F
(0°C), and aluminium provides a perfect complement to the
plastic cladding of the walls. These holds keep entirely
odour-free.
Author's reply
Leveau (USA): In reply to Allen's remarks about the im-
portance of elimination of cracks, Leveau stated that cracks
generally are the result of vibration cycles which are different
from steel, and refers to the chapter on Vibration contained
in the book A/aminum Boats published by Kaiser Aluminum
and Chemical Sales, Inc., Oakland.
To Lee's comments on UK practice, Leveau replied that
when painting aluminium boats with anti-fouling compounds,
barrier coats should be used as explained in all painting
recommendations. Mechanical fastenings of dissimilar metals
should always be protected, as shown on page 235. The
drawings on page 235 also show the fastening materials, and
page 239 refers to fuel and water tanks.
[305]
MacLear discussed comparison of costs and Leveau
would add that the price differences quoted are approximately
the same in various yards with slight differences, depending
usually on the yard's experience with aluminium construction.
In reply to Pedersen's queries concerning insulation,
Leveau said that aluminium hulls built in the USA are not
insulated, and neither is it necessary.
Nickum had mentioned the hazard of fire, but this is a
problem with most materials.
Verweij points out the problem of galvanic corrosion, but
Leveau said that this can be eliminated with proper care in
the separation of bi-metallic connections and in following
published instructions for painting. Investigations on notch
or crack propagation in aluminium are going on at various
organizations. A fibreglass Coast Guard rescue boat recently
came apart and sank in San Francisco Bay. Leveau had
never heard of an aluminium boat coming apart.
Leveau thanked Troup for his interesting comments and
agreed that expert help is needed as it is in most construction
projects of whatever kind, especially in developing countries.
Jn reply to Leathard and Toullec, he said that it is up to
qualified naval architects who design the aluminium vessel to
consider stress calculations and the lighter weight for the best
performance.
Nickum commented on aluminium alloys and Leveau
agreed that it is correct to use care in strength calculations
in welded structures, and table 4 of his paper may be used as
a guide. Alloy 6061 can be welded and frequently is, although
the strength of the weld zone is considerably reduced.
In reply to Kilgore's comments, space did not permit
Leveau to go into the matter of forming and bending
aluminium plate and shapes. However, all of the major
aluminium prime producers have publications dealing with
this subject.
To Lindblom's comments, Leveau added that aluminium
has shown remarkable resistance to ice. As a matter of fact,
several outboard boats and a 27 ft (8.3 m) fire boat have
been used in icebreaking operations with no damage to the
aluminium shell.
To Hamiin's question, Leveau believed that aluminium
fish hold linings and partitions have better ice-keeping
qualities than any other materials. That is also the reason for
using aluminium in the freezing compartments of domestic
refrigerators.
To McNeely's comments, Leveau said that initial costs of
aluminium boats are about 10 to 20 per cent above other
materials, depending on the yard. However, less maintenance
requirements, more speed with the same power, more carrying
capacity, offset this in a short time. Note comments in
the first three paragraphs of his paper.
PLASTIC FISHING BOATS
Mclnnes (UK): During recent years, increasing interest has
been shown in the use of reinforced plastics for the hulls of
fishing boats. In view of this interest, Lloyds Register have
published their "Provisional Rules for the Application of
Reinforced Plastics to Fishing Craft" (Lloyds Register, 1965).
These rules have been based on the experience gained with
reinforced plastic commercial craft and yachts since the first
boat of this material, a 56 ft (17 m) motor yacht, was com-
pleted to class in 1956. The rules cover fishing craft between
20 to 100 ft (6 to 30 m) in length, but design studies of larger
boats have been carried out.
Although the rules are primarily intended for the guidance
of owners and builders wishing to use this method of con-
struction for fishing craft to be classed with the Register,
they should also prove useful guidance to builders, and those
at present contemplating building-up or replacing their
fishing Meets. The requirements have been presented in a
simpler technical manner and contain much descriptive text
with sketches of constructional detail.
Many of the problems and pitfalls experienced by moulders
over the past few years are mentioned, and consequently can
be avoided by the boatbuilders just starting to use this new
material. One such problem dealt with is that mentioned by
Takchana and by della Rocca, namely the need for a stiff
bottom construction over the entire length of the propeller
shafting.
Hull scantlings arc given for solid single skin and for
sandwich construction. Here is envisaged a thinner core
material than that proposed by della Rocca, as at present
there is no suitable polyurethane core material available on
this side of the Atlantic.
The various types of laminations mentioned in the papers
have been described in the rules, but for simplicity of pre-
sentation, the requirements are stated in terms of the
general purpose chopped strand mat. If laminates of woven
roving, or of composite mat-woven roving arc to be used, the
requirements are obtained by adjustment for the higher
strength materials. In Britain similar procedures are used to
those so well presented by Verweij and Lloyds will try to
incorporate such correction factors when revising the rules.
A section dealing with structural and production con-
siderations is included and draws the builder's attention to
the need for careful and economic planning, in detail design
as well as the fabrication procedures to be carried out on the
shop floor. A note of warning is included as regards over-
stretching the yard's capacity of both labour and moulding
space. "Don't bite off more than you can chew" is a fairly
good rule for boatyards, as the successful use of this material
is directly related to maintaining simplicity and consistency.
Questions asked
If work of a high quality is to be achieved and consistently
maintained, it is essential that the hulls are moulded under
good conditions, and as is Lloyds' normal practice with other
plastic craft, they require the hulls of fishing boats to be
moulded in an approved workshop. There are a few comments :
• When boats are being lifted by hooks, it is usual to
use a bending moment of WL/6 with a conservative
stress of J ton/in2 (80 kg/cm2) rather than the WL/12
value given by Takchana,
• Della Rocca mentioned the use of fire-retardant resin,
but this should not be advocated as it will cause an
unjustifiable increase to the material costs, with
possible adverse effect on weathering characteristics.
If fire retardency is desired it may be obtained by the
normal methods such as the use of a fire-retarding
paint,
• Could Della Rocca give us details of experience with
balsa wood sandwich in vibration areas? It may be
satisfactory with smoothly running engines but a bit
doubtful when heavy dicsels are fitted,
• In Della Rocca's paper, he relates the plastic scantlings
to steel scantlings and in doing so it should be stated
that deductions can be made for corrosion and for
higher possible negligence,
• The involved chemistry and adding of the various
ingredients to the resin mix is not as complicated as
would appear. There is an increasing tendency for the
moulder to use the material straight from the drum
with only the addition of the catalyst, and sometimes
pigment,
[306]
• The selection of the laminate construction has been
dealt with at length, mostly in favour of the composite
mat/woven roving. The mat laminate should not be
so easily disposed of. This construction is being used
in the 85 ft (26 m) South African boats under survey
and is proving structurally adequate and economically
sound,
• As mentioned by all authors, the designer has plenty
of scope with this material and reduced scantlings can
be achieved by intelligent design. Uni-directional
material can be employed in the sheerstrake, deck
edge and in the keel to increase the hull stiffness.
Bilge keels and rubbing bands can effcctivley be made
into strength members,
• Can Takehana give any further information on the
use of ultrasonics for the detection of delamination
and for the measurement of laminate thickness?
Japanese practices
Lee (UK): Takehana's paper illustrates the difficulty of
introducing a new material of construction, the full value of
which is only achieved by using new concepts of design and
manufacture. It is too much to expect seafarers to accept so
much novelty at one time and it would be a pity if reinforced
plastics attracted a bad reputation through inappropriate
treatment. Takehana's approach is to be commended.
The statement that FRP vessels built on wooden boat lines
are comparatively light requires qualification as the scantlings
of wooden boats vary greatly and stiffening or bulk has to
be worked in FRP boats far beyond the needs of strength in
order to achieve an acceptable degree of rigidity.
The following information reflects experience on this
matter in UK:
Boat
14ft (4.3 m) sailing
dinghy ex mast, sails
and rigging
27ft (8.2m) ship's sea
boat including engine
36ft (11 m) ship's and
harbour work boat in-
cluding engine .
52.5ft (16m) harbour
launch including en-
gine
Wood
FRP Composite
580 Ib 370 Ib
(263kg) (168kg)
1 .77 tons 1 .72 tons 1 .80 tons
5.3 tons 5.3 tons
17.74 tons 14.9 tons —
The hull shapes illustrated in Takehana's paper show
sharp chines. FRP does not take kindly to such shapes as the
sharp edge is resin-rich and will chip under bumping condi-
tions. Practice in UK is to work to a radius of curvature
equal to twice the thickness of the laminate. Incidentally,
plane surfaces which are associated with sharp edges are not
as easy to release from a female mould as are curved surfaces,
the greater stiffness of which facilitates removal.
Stiffeners and bearers
As for the significant hull deflection of FRP boats, stiffening
is certainly a matter which has to be considered in design.
There is evidence that, with some resins and methods of
manufacture the amount of deflection is progressively less
with time, indicating possibly a continuing cure of the plastic.
The remarks about wooden engine-bearers are of particular
importance. Wooden bearers are easier to adjust when
fitting the engine or replacing the engine by another one and
they absorb vibration better than do plastics bearers. Wood
in way of the engine also absorbs some of the noise which
might be troublesome with an all-FRP laminated structure
as this material reflects and transmits noise. Nevertheless,
FRP is better than metal as regards vibration and noise.
The sandwich construction described by Takehana is
particularly appropriate when it is required to have a clean
interior surface, free from the obstruction caused by stiffeners.
The polyvinyl chloride (PVC) core, laid on sections, has also
the advantage as serving as a mould. UK practice is to have
a much thicker core than that. Caution is necessary with this
method of construction as expanded plastics are weak in shear.
Takehana's proposal regarding an effective and reliable
means of inspection is fully supported. Ultrasonic methods
are showing some promise.
Regarding the remarks about fatigue, wear and durability,
the UK has a 25 ft (7.6 m) FRP boat which was built in 1953
and has served for experiments in repair techniques, etc.
The boat is now nearly at the end of the normal "life" of its
wooden counterpart and will be kept in service for a further
five years with the intention of finally testing it to destruction.
The evidence is that it is superior to wood as regards durability.
Experience shows that sacrificial wood is necessary for rubbers,
false keel, etc. in order to safeguard against wear by abrasion.
Long-term experience is awaited about the fatigue of FRP,
particularly when associated with the large amounts of de-
flection as pointed out by the author, and this might be
serious in a very long craft. It is worthy of note, however,
that two FRP boats, the 36 ft (1 1 m) llala and 21 ft (6.4 m)
Golif crossed the Atlantic safely, meeting some very rough
seas, in the Transatlantic single-handed sailing race of 1964.
Takehana's statement that overhead costs are reduced in a
boatyard concentrating on plastic construction needs quali-
fication as extra costs arise from the temperature and
humidity controls necessary when working with plastics.
Takehana docs not mention the use of a spray gun in
depositing FRP. This is a method which lends itself to mass
production and it gives very good results.
Experiment in Zambia
Heath (Zambia): The Fishing Craft Experimental Section of
the Fisheries Department of Zambia, has recently made a
one-piece glass fibre mould from a marine plywood version
of FAO's design BB 59— the 24 ft (7.3 m) beach boat shown
in Gurtncr's paper.
Two hulls have been built from this mould, using 1 J oz
glass mat and polyresin, using six laminations on the bottom
and five on the sides. Engine beds are 3 in (76 mm) thick
hardwood, 9 ft (2.7 m) long and are bonded with glass and
resin to the hull.
One boat is powered with an 8.5 hp air-cooled diesel, the
other with a similar 16hp model which has also to supply
power to a line hauler.
Information is needed on :
• Effect of humidity during the laying-up process
• Effects if any of the sun in the tropics on fibreglass and
resin laminates
• Is it necessary to use a gel coat what is the advantage
apart from colour? Cracked gel coats have parted
from the hull
• What are the suitable plastics for petrol and fuel oil
tanks, and fireproof plastics?
• Experience in setting up a fibreglass boatbuilding
business in a developing country (sub-tropical).
Information is needed to set up a possible co-operative
enterprise to build, say 30 beach boats a year in the
first instance
[307]
Rebollo (Spain): So far only a few pleasure craft have been
built in plastics in Spain. In any case, the Government as a
general rule does not intend to authorize the use of plastics
for hull construction until rules have been drawn up regarding
appropriate scantlings and standards been established for
quality, strength, fire resistance and other properties of these
materials.
Type of engine bearer defended
Venveij (Netherlands): Takehana points out, as was already
done by Takagi and Hirasawa, that it is essential for Japan
to build a large number of fibreglass fishing vessels in order
to reduce maintenance costs.
In Takagi and Hirasawa 's paper, it is also mentioned that
the ratio A /LED is constantly increasing. There again, the
adoption of fibreglass as building material would be favour-
able, since the resulting lower hull weight would tend again to
reduce the ratio A/LBD.
Thus there is not too much danger that the hulls become
too light and "lose balance" as mentioned by Takehana, but,
of course, one never can use the same lines plan when chang-
ing from a wooden into a fibreglass boat and stability must
also be carefully investigated. Also the problems with bump-
ing and grounding during ebb tide will not present any real
difficulties.
As regards the problem of the use of wood in engine
bearers, Verweij disagreed altogether that it is essential. His
experience goes to diesel engines up to 310hp. All these
engines have been installed on fibreglass bearers without using
wood at all, but by using box type fibreglass girders filled
with foam to dampen vibration.
As regards essential research, Verweij agreed whole-
heartedly with what Takehana suggests.
As for fig 11 and 12 in Takehana's paper, Verweij com-
mented in this respect on Yokoyama's paper. In fig 5 of that
paper, the calm water propulsive characteristics are given.
As Yokoyama says himself, the relative rotation efficiency of
the propeller is very low. This must be due to the shape of
the afterbody. Maybe the building methods with wood
require this, but when building this boat in fibreglass, it
would be very easy and not very expensive to build a tunnel
for the propeller.
This would not only improve the propulsion characteristics,
but would also very effectively guard the propeller, when the
boat was aground or lying ashore, without the need of some
mechanism to raise the propeller under such conditions. An
idea of the afterbody of the present wooden vessel and the
proposal for the FRP vessel is given in fig 29.
SECTION A-A_J__
— WOODEN
— FRP
SUGGESTED MODIFICATION FOR FRP
CONSTRUCTION TO IMPROVE
PROPULSIVE EFFICIENCY AND
PREVENT GROUNDING DAMAGE
Fig 29
Synthetic FRP qualities
Kllgore (USA): Three papers have dealt with plastics con-
struction (Takehana, Verweij, Delia Rocca). Pedersen has
also mentioned composite construction of wood and fibre-
glass. For the sake of completeness on this subject, it is
suggested that reports be added on the properties of the
synthetic fibre reinforced-plastics ; they depend on wood for
strength. The chief of these is Polypropylene, but Dynel and
Dacron also show promise. Briefly the advantages are:
• Resins used with synthetic fibres stick to damp wood
• Resins are elastic
• Elongation of fibres at rupture is over 20 per cent
• Moulds are not necessary
• Mass production is not necessary for economy
• Cheapest kinds of wood are suitable for cores
• Skills in wooden boatbuilding are readily adaptable
• Resulting weight is lighter than fibreglass
• Fastenings need not be non-corrosive
• Impact properties are superior to fibreglass
• The useful life is longer than fibreglass
• The cost of one boat of composite wood-synthetic
plastics is much cheaper than a single fibreglass boat
Recently the Society of Small Craft Designers (USA and
Canada) has had two comprehensive papers on the synthetic
fibre-reinforced plastics by Lord and Koopman, and a
summary by Koopman follows below. Enough boats have
been built this way to prove practicability.
US practices
Koopman (USA): Large savings are possible through the use
of FRP in both large and small fishing vessels. These materials
have been successfully applied to small hulls, but are seldom
applied to large hulls where their benefit may be felt most.
Delia Rocca stresses the weight saving in hull structure, but
says little about the effect this saving has on the other elements
of the hull. The use of FRP requires that an entirely new hull
be designed. Full ends arc no longer necessary to provide
that little extra displacement. The added cross-sectional area
of the hold is small. Capacity must be increased by the
lengthening of the hold as well as the hull. A slight increase
in the hull length will increase cost little and require no more
power. The power requirements for a hull of a specified hold
capacity are lower than that of todays standards. The reduc-
tion of power and full requirements make the FRP fishing
trawler less costly to construct than a wood or steel vessel.
A FRP fishing trawler has the disadvantage that it must be
constructed in a costly mould. It is difficult to make altera-
tions in hull design to suit changes in fishing gear. A mould
may become outdated before its cost has been defrayed.
Wood is not out of contention with FRP. Through the
use of synthetic FRP wood can be used at its optimum,
resulting in light, inexpensive structures. FRP has had
limited success when combined with wood because of its
relative rigidity. The synthetic reinforced plastics, such as
Polypropylene and Dynel, however, are highly flexible.
Stress concentrations are not built up by the dimensionally
unstable wood.
A synthetic reinforced plastics covering serves to:
• Prevent decay
• Protect the wood from abrasion and bruising
• Unify the wood structure
• Reduce the cycling of the wood moisture content
A synthetic reinforced plastics covering does not:
• Prevent moisture from entering the wood
• Add appreciably to the structural strength because of
its low modulus of elasticity
Polypropylene and Dynel reinforced polyesters and epoxies
have been used successfully in the designs of Lord for over
[308]
TABLE 10
Typical properties of Polypropylene and Dynel reinforced plastics
Property ....
4o7(113g)Vectra
3.75 oz( 106 g)
Flexural Strength
Polypropylene
Travis Dynel
Yield ....
. lb/in2 .
6,000 7,000
6,000-9,700
kg/cm2 .
422-493
422-683
Ultimate
. lb/ina .
10,000
6,000 9,700
kg/cm2 .
705
422-683
Flexural Modulus .
. Ib/in* • 10r'
1.10-4.33
1.05-4.10
kg/cm2 x 105
0.0775-0.306
0.0705-0.289
Elongation at rupture
. Per cent
20
1.5 10.0
Fzod impact ....
. ftlb/in of notch
18-20
0.50-0.75
kgm/25.4 mm
2.5-2.77
0.07-0.104
Specific gravity
.
1.05-1,10
1.15 1,20
five years. The largest hull constructed with these materials
is 95 ft (29 m) long. There are no indications that much
larger hulls cannot economically be constructed using wood-
plastic composite structure.
Polypropylene and Dynel reinforcements are used with
flexible polyesters and high elongation epoxies. Use of the
more conventional rigid thermosctting resins results in
brittle and notch sensitive laminates. Polypropylene rein-
forced plastics is used for the general covering of hulls. It acts
to unify the hull by preventing the shifting of the wood
members, and also acts as a crack arresting covering. Though
a wood core covered with polypropylene reinforced plastics
may be broken, the fibrous web which results prevents com-
plete rupture of the panel and leaking is held to a minimum.
Dynel reinforced plastics is notch sensitive, but has unusually
high abrasion resistance. It is ideal for docking shoes, ice
guards, and other chafe gear.
Neither Dynel nor Polypropylene reinforced plastics
require gel-coats as do the FRP. Dust from sanding is not
irritating, and the flexibility of the fabric lends itself to easy
lay-up. See table 10 for some typical properties of Poly-
propylene and Dynel reinforced plastics.
In fig 30 is the midship section of a synthetic reinforced
plastic-wood composite trawler having the same dimensions
as the hull used by Delia Rocca for his studies. The section
only serves as a comparative study, and many improvements
can be made upon it. Panel stiffness and other local properties
of the wood-plastic composite structure are superior to that
of the single skin, mat-roving hull proposed by Delia Rocca.
In determining the strengths of the wood a grain slope of
1/10 and a moisture content of 15 per cent was used. The
frames are laminated and the planking is edge glued with
high elongation epoxies. The structure is lightly tacked
together with bright nails since the glued joints give unity to
TABLE 1 1
Midship section characteristics 110 ft wood and synthetic reinforced
plastic composite trawler
Weight/ft (m) amidships, Ib (kg)
Weight/ft (m) relative to wood
Hold area inside sheathing ft9 (m9)
Hold area relative to wood
Inertia, in 9~ft 9 (cm 8-m 9)
Elastic modulus, lb/in9 (kg/cm9) x 10*
El, Ib-ft9x 10» (kg-m9x 10") .
Stiffness relative to wood
Section modulus, in*-ft (cm9-m)
Stress for 2.7x 108 ft-lb (0.375x 10
m-kg) mom. lb/in9 (kg/cm9)
Ultimate strength lb/in • (kg/cm9)
Safety factor on ultimate
750
.50
237
1.19
62,790
1.10
69
.70
8,372
323
(1.120)
(22)
(105.300)
(0.0775)
(33.7)
(4.275)
(22.8)
(490)
the structure. The bright nails will not rust once the hull is
covered. The first ply of Polypropylene cloth is set in epoxy
to obtain the best possible adhesion to the wood, but the
rest of the covering is done with the less expensive polyesters.
Tables 10, 1 1 and 12 are a result of an examination of the
wood-plastic composite structure. The values in these tables
are intended to correspond with similar values entered into
tables 2, 3 and 4 of Delia Rocca's paper.
All wood white pine
All facings 4 ounce
polypropylene plastic
Fig 30. Midship section of 110 ft wood and synthetic reinforced
plastic composite trawler
TABLE 12
Preliminary light ship weight 110 ft wood and synthetic reinforced
plastic composite trawler
Hull, structure, tons
Sub-total, tons
Margin—design (10 per cent), tons
Margin — soakage (3 per cent), tons
Light ship, tons
Hull structure relative to wood
Light ship relative to wood
65
147
15
4
166
.54
.69
[309]
TABLE 13
Preliminary light ship cost estimates 110 ft wood and synthetic
reinforced plastic composite trawler
Material cost/ton . . £343 ($960)
Hull weight with margin . . 72 tons
Invoiced material ( x 1.15) . . 83 tons
Material cost .... £28,450 ($79,680)
Manhours/ton . . . .200
£/manhour ($/manhour) . . £0.83 ($2.32)
£/tons labour ($/ton labour) . £162 ($464)
Direct labour . . . . £11,940 ($33,410)
Overhead, 80 per cent labour . £9,540 ($26,730)
Material, labour, and overhead . £50,000 ($139,820)
Profit (10 per cent) . . . £5,000 ($13,980)
Sub-total £54,700 ($153,830)
Outfit, machinery, etc. . . £57,500 ($161,700)
Mould cost . . . . £— ($— )
Total, 1 boat .... £112,500 ($315,500)
Total, each of 5 boats . . £100,000 ($280,800)
Total, each of 25 boats . . £83,300 ($233,500)
Total cost relative to wood :
1 boat 99
5 boats 96
25 boats 92
McNcely (USA): One of the more important implications of
Takehana's paper is the ease with which mass production
techniques might be employed to lower the cost of standard
hull forms. If a reduction in the number of base hull forms
could be effected then lower costs through mass production
might accelerate the advancement of fishing in developing
countries. What is suggested here is that it is unreasonable to
have a thousand different hull designs for use in about 20
various fisheries. Standardization in FRP construction might
be an important key to the development of fisheries in several
sections of the world.
Netherland experience
Verweij (Netherlands): Delia Rocca's paper is excellent. As
regards the materials of the core it must be pointed out that
excellent experiences have been obtained in the Netherlands
with polyvinyl chloride (PVC) foam, which was used in deck
and hull of both 50 ft (15 m) landing craft and 77 ft (23.5 m)
pilot vessels. For future application, polyurethane foam may
be contemplated for the deck, whilst retaining PVC for the
hull core. With PVC foam, extensive research was done and
amongst other things, it was found to have good durability
and fatigue characteristics. Not much is known so far about
the fatigue properties of polyurethane.
As regards the various types of hull construction, the
systems mentioned there under (1), (2) and (8) are to be
preferred over others and also that (1) is better than (2).
When dealing with sandwich construction, Delia Rocca
rightly points out the additional advantage obtained with
excellent thermal insulation. However, Verweij did not share
Delia Rocca's opinion as regards the weight of a sandwich
versus a solid construction. Also the new Lloyds rules arrive
at lighter weight for the sandwich. This different approach
may also explain greatly the higher price of the sandwich
boats — Delia Rocca finds.
As regards difficulties with the propeller shafting, which
may arise due to hull deflection, a flexible coupling and, if
necessary, a part of the shafting at midlength with a universal
joint at both ends will cure the problem.
Lee (UK): One point which seems to be omitted from the
remarks on reinforcement is that chopped strand mat limits
"wick" action in the event of damage and thus minimizes
delamination.
Mould costs similar
MacLear (USA): Complimented Takehana for his paper and
noted with interest that the mould costs in Japan are very
similar to those of the USA and Europe. Mould costs are
often equal to the cost of the boat, if the hull alone is moulded.
If a deck mould is also made the total mould cost can be
twice the cost of the finished boat, and if extensive interior
mouldings are made the cost ratio can be as high as three
times.
He had very much enjoyed Delia Rocca's paper and did
not doubt that there will be 110ft (34m) fibreglass trawlers
in the future. He thought one should start with boats of
60 to 70 ft (18 to 21m).
He also mentioned that he had seen fibreglass both outside
and inside of a plywood boat. In the beginning he was con-
cerned about rot. The US Coast Guard is considered to be
very severe in their demands and they had tested such a
12-year-old boat and had found no deterioration. This boat
was 100ft (30.5 m) long, used for charter parties going out
one to three days at a time for fishing for pleasure. The plastic
boat industry has grown very fast in the USA, 50ft (15 m)
boats are laid up in two days compared with the usual one
to six months for a wooden boat. The US Coast Guard and
US Navy now make most of their smaller boats in FRP.
A boat owner had had a wooden 40ft (12m) boat and
had been spending £1,000 ($3,000) a year in up-keep. He
now has a fibreglass boat of the same dimension and spends
£180 ($500) yearly in up-keep. This great difference seems
too good to be true, but other owners agree that it is quite
possible.
Finally a warning. A lot of boat yards in USA which
started with fibreglass constructions have gone bankrupt.
It is interesting to note that there are a great many satisfied
plastic boat owners but quite a few disappointed moulders.
Timely and valuable
Colvin (USA): Takehana's paper is a very timely one with a
great deal of food for thought. It is quite evident that he has
found in Japan a very similar problem to that which exists
in USA that is, a sharp increase in the cost of timber along
with its decrease in quality, and the scarcity of skilled wooden
shipwrights, and the even further scarcity of those willing to
undertake the long apprenticeship to become wooden
shipwrights.
It will be appreciated by all the difficulty of the Japanese
Fisheries Agency in selecting the prototypes because of the
vast variations not only from locality to locality, but of the
various vessels within the locality. The laver and pearl boats
do lend themselves to the FRP construction. However,
aluminium as well as steel also lend themselves to this type
of vessel. Takehana points out that steel construction is
becoming more popular and this is also true in USA. The
small village shipyards that already have the technical
capabilities of building in wood would find the change-over
into steel one of a minimal cost and very little change in
technique. It would require the training of a welder, but the
equipment outlay would be less than £180 ($500). This is
especially true of those yards building in sizes under 50ft
(15 m) in length as a 180 amp AC/DC welder and an oxygen-
acetylene cutting torch would be the only absolute require-
ments. While the methods of working in metal are different
to those in wood, yard personnel experienced in wood
construction require only a few weeks to grasp the differences
in technique. Also, in oysterboats that range from 28 to 35 ft
(8.5 to 10.7m) in length, it is possible to build not only a
stronger boat and a better boat but a lighter boat in steel than
conventional wood planking and the same weight as plywood
planking. The small shipyard, however, is not faced simply
[310]
with whether or not they can continue to exist by building
just wood or just steel; but it finds itself faced with the
problem of having to use FRP and aluminium as well as steel
and wood. Each has its place where it functions best. The
cost change-over from wood to FRP construction would be
approximately the same as for steel construction if spray
equipment were purchased.
Theoretical or actual strength?
Takehana's method of building without moulds would
indeed eliminate much of the initial cost that is associated with
FRP construction. A point that he has brought out very
clearly is the desirability for design data showing how many
layers of FRP are necessary to provide the required strength
along with the type of fibre to be used. While it is possible
in theory to calculate this strength, the theoretical strength
and the actual strength arc two different values. A great deal
of skill is required in the lay-up of FRP hulls if they are to
have consistent integral strength and uniformity. The tem-
perature, humidity and the human factor all affect the end
result of FRP hulls. And if it is to be spread out on a wide
scale through a variety of builders, then there should be a
means of testing each of the hulls via a trepanized system
with a sampling of at least ten spots per side. If the quality of
the lay-up lacks by a certain percentage of the theoretical
lay-up, then additional material would be called for. Under
this system, it would make the builders more conscious of
quality.
The advantage that is inherent in most Japanese fishing
vessels is their simplicity of form which, in turn, gives them a
dampening motion, permits rather heavy loading, still
maintaining very good powering characteristics. The abandon-
ment of the design of a traditional vessel and its replacement,
while it often cures one problem, creates many more. Some-
times they even go so far as to solve and cure problems that
have not even become apparent. It would seem that the solution
to the small craft problem would be in the training of the
small builders into all materials. Then full advantage could
be taken of wood, steel, FRP and aluminium simultaneously
and by the same builder.
Balancing sales with production
In USA FRP does cost more than its counterpart in wood,
and that while mass production allows one to turn out a
vessel in a shorter length of time, it also creates the problem
of having to expand the facilities too a point where sales
must keep up with the production, and ideally must exceed
production. If a small yard is to mass produce, then the yard
layout in woodworking tools is approximately the same as it
had been in the wood boatbuilding unless, of course, they
purchase the moulds from a competent pattern shop which
would make their plate layout very minimal.
The actual lay-up can be done by semi-skilled workers;
however, in Takehana's table 6, it is noted that the timber,
bolts and nails in the non-moulded sandwich boat is 58 per
cent of that of the all-wooden boat, which indicates that some
skilled labour is going to be a requirement. The vessels
shown in fig 11 and 12 are ideally suited for direct conver-
sion to metal construction*
It will be interesting to see the developments in fibreglass
reinforced plastics over the next few years in Japan. If the
vessels can become standardized, perhaps the solution then
falls entirely within the realm of FRP in small craft at least.
However, if the standardization becomes impossible, then it
would seem that diversification in the small yards, in gradually
introducing various components of FRP will be the way to
gain acceptance of the material and give the necessary time
to the individual builder to develop his techniques.
Author's replies
Takehana (Japan): Answer to Mclnnes: The bending moment
WL/12, stress 25 kg/cm'2 was obtained from static experiment,
so in the design stage the bending moment must be taken as
WL/6 with consideration to dynamic action.
Due to the recent development of ultrasonic techniques, it
becomes possible to generate waves which have higher
power and narrower pulse width. It has been said that flaw
detection in high decrement material is impossible, but now
this becomes possible.
The present applications of this high power detector are as
follows :
• Detection of tumour in human body
• Detection of cracks in fire clay
• Detection of a flaw in the solid propellant in a missile
Ultrasonic waves look also promising in the non-destruc-
tive detection of cracks and dclamination in FRP laminates.
Pulse width 0.05
Output power .
Frequency
. 0.1 /AS
. 10 kw
10 megacycles
The answer to Kilgore is: If a wooden plank is completely
enclosed by synthetic fibre plastics, delamination would
occur by the swelling of the wood due to the absorption of
water. Should this point be solved completely, this would be
the best way to save wood, make a strong and rigid ship and
reduce the maintenance costs.
Answer to Colvin: Lee has also mentioned the spray gun
but it appears very difficult to handle and the laminate
produced is not so strong as roving cloth reinforced plastics.
The raw material is also more expensive if mass production
is not adopted. A more desirable piece of equipment for a
plastic boatyard would be a temperature controlled workroom
for cold and bad weather countries. Regarding table 6 which
shows that in FRP no-mould construction, timber bcilt nails
are only 58 per cent of those required for wooden construc-
tion. But in using these, less skilled labour is required than
for the wooden ships.
Answer to Lee: a sharp chine is not favourable in FRP
construction and it is preferable to round up the sharp
corners, but not to such a degree as to affect the roll-damping
characteristics. To the point that poly vinyl-chloride (PVC)
core is not very strong to shear, the combination cf paper
honeycomb and plastic foam might offer a solution.
Meeting Lloyd's rules
Delia Rocca (USA): Mclnnes stated that the provisional
Lloyd's rules envisaged a thinner core material than that
proposed in his paper; as at present there is no suitable
polyurethane core material available on the US side ( f the
Atlantic. The Lloyd's rules "are exceptionally well done and
in considerable detail". The proposed scantlings are in
remarkably close agreement with these rules. Two methods
were used to extrapolate the Lloyd's rules requirements for
sandwich construction with 36 in or 3 ft (0.9 m) stiffening
spacing to the 72 in or 6ft (1.83m) spacing used in the
proposed 1 10 ft trawler. First, as specified by note 3 of table 2
in Lloyd's rules, where the spacing of the stiffening members
differs from the basic 36 in, the section modulus is to be
modified in the ratio of the spacing squared. By simple
arithmetic, (72/36)2, the factor for increasing the section
modulus is 4. To maintain the same mat laminate thickness
and weight, the 1 in (25 mm) core depth specified in table 2
was multiplied by the factor of 4 giving an equivalent core
thickness of 4 in (100 mm). The second method used was to
[311]
determine the section modulus required by Lloyd's rules for
a single skin laminate for 72 in (1.83 m) stiffener spacing and
determining an equivalent sandwich section. Both approaches
gave very close agreement and resulted in the scantlings
presented, in fig 6 of the paper. The core material is not
considered in the strength of the panel by Lloyd's rules and
the paper.
Mclnnes' comment in regard to the use of fire-retardant
paint as a normal method of obtaining fire retardancy is
satisfactory for steel or wooden hulls. This method is not
recommended for fibreglass reinforced plastic hulls since in
addition to the cost of painting the outer and inner surfaces
of the hull, the paint will probably peel off unless it is an
expensive plastic type of paint compatible with the polyester
resin. Further, the outer surface will require light sand
blasting or sanding to remove the wax and mould prior to
painting. If the approximate 5 per cent increase in the overall
cost of the trawler is considered by some to be excessive for
fire-retardancy of the entire laminate, it is then recommended
that only the outer gel coat resin and the resin used with the
innermost ply be fire-retardant. This will result in a superior
and more durable hull requiring much less maintenance at a
considerably reduced initial cost.
In reply to Mclnnes' request for details of experience with
balsa wood sandwich panels in vibration areas where heavy
diesels are fitted, Delia Rocca advised the use of a balsa core
sandwich panel in the bottom of a 50ft (15.3m) pleasure
craft directly below a generator driven by twin diesels at high
speeds in fairly rough weather without any detrimental effect
on the sandwich panel.
The corrosion issue
Delia Rocca agreed with Mclnnes' comment that when
relating the plastic scantlings to steel scantlings, deductions
can be made for corrosion. In converting the steel scantlings
obtained from the American Bureau of Shipping Rules to
fibreglass reinforced plastic construction for the 110ft
trawler, .08 in (2 mm) for corrosion from the 0.31 in (8 mm)
steel plating was deducted prior to calculating a laminate of
equivalent stiffness based on the cubed root of the ratio of
the flexural moduli.
Delia Rocca recommended the composite mat-woven
roving laminate in lieu of the all-mat laminate for the 110 ft
trawler because for a 5 per cent increase in material cost, a
3 per cent savings in weight, a 30 per cent increase in hull
bending modulus and greater impact resistance will be
obtained. Further, experience in the USA indicates that it is
much easier and quicker to lay-up the composite mat-woven
roving laminate than the all-mat laminate.
Heath requested information on specific items, the following
advice is offered:
• Since the glassfibres readily absorb water prior to
being laminated, excessive moisture in the moulding
shop due to high humidity will accumulate on the
glassfibres which prevents the resin from coming in
contact with the compatible chemical finish on the
glassfibres and the chemical reaction at the resin-glass
interface does not occur resulting in a poor bond,
• The effect of the sun on fibreglass reinforced plastic
laminates will improve the basic laminate properties
until full resin cure is achieved and the properties will
remain constant. However a good weather-resistant
gel coat is necessary on the surface exposed to the
weather to protect the basic laminate. Pigmented gel
coats after a number of years will have a tendency to
fade,
• A gel coat is recommended and should be reinforced
with a layer of 1 oz mat minimum with the next ply of
reinforcement laid-up just after the resin on this mat
has begun to gel. This will prevent the peeling off of
the gel coat. If the gel coat peels, the entire surface of
the hull must be sanded and resurfaced with a good
polyester gel coat, or an epoxy base paint,
• Polyester resins are suitable and will resist attack by
petrol and fuel oil tanks but they must completely
cover the fibreglass reinforcement and be fully cured.
A gel coat surface will provide exceptionally good
protection. The author does not know of any com-
pletely fireproof plastics. However, good fire-resistant
or self-extinguishing polyester resins such as Hooker
Chemical Company, Durez Division Hetron polyester
resins are available,
Disadvantages of plastic-coated hull ignored
The following reply to Koopman's comments will also
apply in part to Kilgore. Koopman has presented a very
impressive discussion for a plastic-coated wood hull
emphasizing all of the advantages and disregarding all of the
disadvantages. Koopman's statement that Delia Rocca had
disregarded the effect of weight savings on the other elements
of the hull is incorrect. Delia Rocca clearly stated in the
discussion on Light Ship Weight under the Comparison of
Trawler Characteristics the many uses that can be made of the
weight saved and particularly noted that the reduction in
weight will raise the light ship vertical centre of gravity about
5 per cent requiring consideration of stability early in the
preliminary design.
Koopman's proposed hull construction has limited service
experience of approximately five years and has many fabrica-
tion, maintenance and durability disadvantages. The fabrica-
tion of the wood core requires temporary internal framing
which becomes scrap when removed and replaced with the
very expensive pre-laminatcd transverse frames. Maintaining
the moisture content in the wood to a predetermined content
during construction particularly in the warmer climates must
be quite difficult. Swelling of the core and framing with possible
cracking of the thin plastic skin can occur when the core
begins to absorb water after launching. The application of the
plastic skin to the core can be very difficult since the first layer
must be placed with epoxy resin to obtain a good bond.
Epoxy resins normally have high viscosities and will require
diluting or considerable working to properly wet out the thin
reinforcement. Excessive diluting of the resin can cause
run-off of the resin resulting in dry areas at the top of the lay-
up and excessive resin at the bottom. Further epoxy resins
cause skin irritation and in severe cases can cause permanent
skin damage unless proper precautions such as gloves, masks,
etc., arc taken. The following layers of reinforcement placed
with polyester resins can also have problems since there is an
interaction between the polyester resin and the polypropylene
reinforcement causing swelling of the fibres and a weakness
in the bond between the resin and fibres. Also the interaction
between the polyester resin and polypropylene inhibits the
hardening reaction of the resin requiring larger amounts of
catalyst in order to complete the cure. Shrinkage of the semi-
rigid polyester resin which is generally 4 to 8 per cent will
cause locked -in stresses in polypropylene fibres and negates
to a large extent their elongation which is essential for this
composite material to function properly.
Analysis of cost factors
For fabrication of this sandwich hull expensive jigs or heavy
lifting equipment is necessary to rotate the large hull after the
outer skin is placed on the core. A substantial cradle to
[312]
properly hold the hull form is also required to prevent dis-
tortion when the hull has been turned over and the inner
laminate and framing are added. This will add substantially
to the fabrication costs. After lay-up of the inner skin the
attachment of the internal frames to the shell will require some
fastenings since a bond between the inner skin laminate and
wood frame with polyester resin is probably insufficient to
resist hull torsion and twisting. Since polypropylene reinforced
plastic-covered hulls are flexible, heavy items such as
generators and heat exchangers should not be mounted on
either the bottom or light frames. Unless these heavy items
can be mounted to internal decks, additional structural
framing will be required t • properly support them on the hull.
After completion of the hull, the outer skin must be finished
by sanding the entire hull surface prior to painting. Sanding of
polypropylene reinforced plastics can also be troublesome due
to the resiliency of the fibres causing pulling away of the fibre,
particularly if the laminate begins to heat up.
In regard to maintenance problems, experience in the
flexible polyester resins has indicated that they have very poor
weathering qualities and are particularly subject to degrada-
tion when exposed to a water or high humidity environment.
Therefore several coats of a good protective paint is required.
The thin skins can be easily damaged and pulled away from
the core due to gouging from rubbing against sharp objects or
dragging heavy items on the deck. Repairs will be difficult
due to replacement of the wood core. Decay or rotting of the
wood core will occur around bolts, screws and other through
attachments to the hull. Also pinholes in the thin skins can
also cause decay. Damage to the core due to impact loading
can be extensive since wood will have a tendency to split along
the length of the grain.
In regard to durability, although the plastic skins will
provide some protection, water and some air will get into the
core causing decay in some areas, particularly in high stress
areas where slight cracks in the skins are unnoticeable. Under
these conditions, decay may be accelerated and the expected
20-year life for wood boats may be reduced.
The greatest concern with this type of construction is that
progressive failure of the wood core due to overstrcssing or
decay cannot be determined during normal inspection and a
catastrophic failure can occur without any prior indication
of potential failure.
Doubtful adhesion
Verveij (Netherlands): Koopman mentioned interesting
possibilities about combining wooden hulls with synthetic
fibres. This can offer a good protection for the outside. It is
doubtful, however, whether there will be a proper adhesion
with next layers using polyester resin, if the first layer was
impregnated with epoxy. In building boats with glass poly-
ester, the mould can be made out of glass epoxy and in that
case no separating agent is needed. Therefore, it may be better
to try resorcinol formaldehyde glue to cover a wooden hull
with synthetic fibres.
However, when comparing a FRP vessel with a wooden
vessel covered with plastic on the outside, one must respect
statements by experts on wooden boats such as Chapel le who
admits that failure of wooden boats is caused by rot or corro-
sion. This rot in fishing craft usually starts from the inside
rather than from the outside. The FRP boat is rotproof both
inside and out. To protect the wooden boat on the inside by
a plastic covering is also both complicated and costly.
Heath has a number of specific questions to which the
following reply is offered :
Humidity, if excessive, can have a detrimental effect on
the cure of the resin. However, actual data are very
scarce. The humidity of the air is not so important as
the presence of actual water on the surface of the glass.
Therefore it is important to store the glass in closed
polyethylene bags preferably containing a little
silicagel, in a room where the temperature does not
drop below the temperature in the laminating room.
Also the resin should never be lower in temperature
than the laminating room and preferably a few degrees
warmer. In this respect it should be borne in mind that
resin which has been kept in a cool place for some time
needs quite a time to take the temperature of the
workshop on a warm day,
• The actual laminating should not be done in full
sunlight, but under cover. In direct sunlight too much
styrene can evaporate, resulting in undercure. Also the
rate of cure along the object under construction may
vary. However, once the FRP laminate has been
properly made, even tropical sun does not have an
adverse effect,
• If a gel-coat is used, not much time should elapse
between the setting of this gel-coat and the start of the
actual laminating, in order to obtain a stronger bond.
Also the gel-coat should be kept thin. Apart from
colour, the gel-coat gives a smoother surface, making
cleaning easier and reducing marine growth. It can
also improve weatherability,
• For fuel and petrol tanks polyester can be used, but a
gel-coat is also necessary. The laminate should be
completely cured. For petrol tanks an isophtalic resin
is better. To Vervcij's knowledge there is not a really
permanent fireproof polyester resin available now-
adays. Therefore he proposed to limit the use of fire-
proof resins to a coating in areas needing extra protec-
tion (such as engine room with petrol engines),
• Information about setting up a FRP boat-building
business can be given more fully in personal corre-
spondence. However, some general remarks in con-
nection with FRP boatbuilding might be useful.
Industrialization plays a more and more important
role, and this importance will continue to grow also
in developing countries. FRP lends itself eminently to
this trend of industrialization. Contrary to wooden
boatbuilding, mainly unskilled, though intelligent
labour is required and one can learn to work with
FRP in a rather short time. Basic for successful
building FRP boats is a design made by someone who
is an expert in this field and a clear and complete
manual for the actual building of the boat, together
with a detailed list of materials. The next requirement
is a few people with some and preferably a good
experience of working with FRP who can instruct and
lead a group of unskilled labour,
The industrialization also asks for standardization, and here
again FRP can help, asking for standardization itself. Finally,
a certain production can be reached in FRP with lower
investments than needed for this production in wood, steel or
aluminium.
Several contributors have pointed out the importance of
low maintenance cost of FRP as compared with other
materials. This factor, having great influence on the earning
power of a vessel should duly be taken into account. Of
course also the initial building cost remains very important.
Therefore, continuous efforts are made to reduce the building
costs of FRP vessels through effective use of materials, but
especially by improving production techniques. This improve-
ment of production techniques is at this moment one of the
main items which is being investigated by a Netherlands Panel
[313]
preparing a report for the 1967 International Ship Structure
Congress. It is expected that the result of this study will
contribute greatly to making FRP commercially attractive
for cargo and fishing vessels up to about 170ft (50m) in
length. Of course also builders of smaller vessels can benefit
from these investigations.
USE OF CONCRETE
James (UK): The use of concrete in the marine field is cer-
tainly not new. Between 1917 and 1922 due to the shortage of
steel during and just after World War 1 over 150,000 tons of
concrete shipping was built on both sides of ths Atlantic,
ranging in size from 7,500 ton oil tankers to small tugs and
lighters* The hull thickness on such vessels ranged from
between 4 and 6 in (102 and 152mm). A new material, a
derivative of concrete has now been developed in UK. in which
the hull has a thickness of only J in (22.2 mm). In this
development all the data obtainable on concrete ship con-
struction over the years has been utilized.
The basic raw materials are sand, cement, steel reinforcing
and other special additives that give this material good
properties.
Concrete boat construction requires no expensive moulds
such as are required in glass-reinforced plastic boat con-
struction and therefore one boat can be produced relatively
cheaply, it not being necessary to recover expensive mould
cost over a series of identical hulls.
All that is required is a suitable jig to support the keel,
preferably capable of having wheels attached for easy move-
ment and a set of wooden frames similar to wooden shams
used in conventional wood boat construction. The steel
reinforcement being built up around these frames. Any shape
of hull may be produced in this manner. The stem mould and
transom mould are removed to facilitate access to the
reinforcement when the hull is cast. After the hull has been
cast and is no longer "green" it is sprayed continuously with
water for between 100 and 1 50 hours according to conditions.
The other frames are then removed and the hull cleaned off
internally.
During the laying-up of the reinforcement for a hull, it is
not necessary to adhere to any strict temperature control,
when the hull is cast, however, it is advisable to maintain a
moderate temperature with a reasonable degree of humidity.
The ultimate tensile strength of this concrete material is
5,340 lb/in2 (390 kg/cm2) and because a mesh reinforcement
is used, it will have this tensile strength in all directions. Most
boats less than 100 ft (30 m) in length are now built of wood
because it is cheaper than aluminium or glass reinforced
plastic. Therefore this concrete shall be compared with wood.
The tensile strength of wood is approximately 6,000 lb/in2
(422 kg/cm2) along the grain and negligible across the grain,
also the tensile strength of a wooden hull is diminished con-
siderably by the fastenings and the fact that the grain often
"runs out" whereas in concrete hulls there are no fastenings
and the tensile strength is accordingly uniform.
The compressive strength of this concrete material without
reinforcement is about 7,200 lb/in2 (500 kg/cm2) after seven
days and 12,225 lb/in2 (860 kg/cm2) 28 days and continues to
increase with age far in excess of wood. Young's modulus of
elasticity for this concrete material is 1.30 x 108 lb/in2
(91 ,400 kg/cm2).
The specific gravity of the concrete is 2.4, that of glass-
reinforced plastic is 1.6, and of a wooden hull including
fastenings 0.9. In spite of the weight of the material a concrete
hull compares favourably in overall weight with both wooden
and gliss reinforced plastic hulls because a concrete hull
requires no heavy internal frames or floors and a panel almost
half as thick as timber is equally as strong.
Vessels shorter than 100 ft (30 m) do not have stresses upon
the hull that are excessive. On a 75 ft (22.9 m) trawler
displacing 1 10 tons the maximum stress at deck level or the
bottom of the skeg, depending on whether the vessel is
hogging or sagging will not exceed 1,000 lb/in2 (70 kg/cm2)
if the thickness of the hull is approximately J in (12.7mm)
thick. Therefore, with the tensile strength of the concrete
material being 5,340 lb/in2 (390 kg/cm2) there is ample
margin for safety.
A pertinent question is whether a concrete hull is sufficiently
strong to withstand rough treatment such as abrasion against
dock walls or rubbing against other craft. For such vessels
concrete is immensely hard and shows great resistance to
abrasion. It has distinct advantages over reinforced plastics
in this sphere. Because of its greater thickness and the fact
that even if the surface suffers abrasion it will not weep as is
the case with a glass-reinforced plastic hull due to its internal
porosity.
After exhaustive tests Lloyds Register of Shipping have
intimated that they will give 100 A I classification to a vessel
with a concrete hull, also the British White Fish Authority
will accept applications for grants.
A concrete hull is very strong and yet is also extremely
flexible. A sample strip was tested by Lloyds Register of
Shipping and the following results were obtained. Size of
strip: 21.65 in (550 mm) long, 5 in (127 mm) side, and 0.65 in
(16.4 mm) thick. The distance of the loading point from one
support point was 8.5 in (216mm). Normal stress levels
+700 to -600lb/ina (+49.2 to -42.2 kg/cm2). It was
flexed for 2 > 10fi cycles without fracture.
Stiffened by metal
The concrete hull is stiffened by the insertion of metal
frames spaced in accordance with the size of the hull and to
these frames are attached lugs to take bulkheads, etc.
James' firm has also devised a method of casting into the
hull, floors and engine beds in concrete and these strengthen
the main structure to a considerable degree.
Vessels constructed of this concrete material up to 40 ft
(12m) in length are slightly heavier than an equivalent vessel
constructed in wood, glass-reinforced plastic or steel. Larger
power-driven hulls are lighter than steel or wooden hulls and
yet have the same strength and are equally rigid. It should
also be noted that vessels up to 60 ft (18 m) in length can be
constructed of J in thick (22.2 mm) material. This thickness
weighing only 1 1 Ib/ft2 (52.8 kg/m2). However, the thickness
of a glass-reinforced plastic hull is greatly increased as the
hull sizes increase. Thereby adding to the cost of materials,
A concrete hull is fire resistant and in this respect has con-
siderable advantage over wooden hulls and glass-reinforced
plastic hulls. Test panels have withstood 3,100UF (1,700'C)
for 1 J hours with no effect on the material.
It is quite possible to construct decks and superstructure
in the concrete material, using the same form as the hull skin.
By doing so one produces a very strong and rigid hull due to it
becoming a complete monolithic structure. On smaller vessels
this is not advisable due to the weight factor.
It is not necessary to protect a concrete hull with paint, but
any normal good quality marine paint will be quite adequate
for decorative purposes and anti-fouling. A concrete hull
requires no maintenance. It is a homogeneous structure,
therefore it cannot leak, cannot corrode and is immune to
marine borers. Barnacles and algae will attach themselves to
a concrete hull below the water line in the same manner as a
timber or metal hull, but they may be easily removed with a
powerful detergent which will have no effect on the hull
Concrete cannot be attacked by marine borers and hulls built
[314]
in this material will not deteriorate as is the case of hulls built
of wood where a very short life span may be expected.
A tremendous advantage of a concrete hull over other forms
of hull material is that it can be so easily repaired. If a con-
crete hull is damaged in a collision it can be repaired in about
one-tenth of the time taken to repair a wooden hull. The
procedure for repairing is as follows: The damaged area is
broken away until the surrounding concrete material is
undamaged and solid. It should be remembered that when a
hull is damaged, the damage is completely localized and is
confined to the area where the impact took place. Once the
broken concrete has been removed any broken mesh reinforce-
ment is replaced and knocked back into its original position.
Simple repair kits
A suitable repair kit is supplied by the makers and the
ingredients mixed in accordance with the instructions and is
then applied to both the interior and the exterior of the
damaged section. The exterior is left slightly rough and finally
"ground off ". The hull is then painted and finished as it was
before damage. Normally a repair can be effected in one
ordinary working day. Whereas it is comparatively simple to
repair a concrete hull even in tropical conditions, the same
does not apply to glass-reinforced plastic hulls where materials
if stored tend to deteriorate and it is not always possible to
maintain the correct working temperatures that are all impor-
tant in effecting a satisfactory repair.
Hulls built of the concrete material arc relatively cheaper
than wood and steel and are cheaper than reinforced plastic
hulls over 30 ft (9 m) in length. The main labour involved in
producing a hull is in setting up and forming of the reinforce-
ment. Consequently larger hulls are proportionately cheaper
than smaller hulls. It must also be realized that to produce a
reinforced plastic hull cheaply a number of hulls have to be
produced from the same mould whereas in the case of a
concrete material hull it is quite possible to produce a single
hull to a particular shape economically.
Above 34ft (10.35m) concrete hulls can compete with
wooden, steel and reinforced plastic hulls. For example a
24 ft (7.3 m) hull complete with floors and engine beds is sold
for £700 ($1,960), a 28 ft (8.5 m) hull complete with floors
and engine beds for £800 ($2,240), a 34ft (10.3 m) hull for
£1,000 ($2,800) and a 45 ft (13.7 m) hull for £2,100 ($5,880).
Concrete hulls are dry, durable and more easy to repair than
hulls made from other materials. Concrete is relatively cheaper
than any other form of construction.
Concrete hulls do not absorb any amount of moisture and
therefore there is no risk of contamination by fish in fishing
boats, moreover, it is a very good insulator having a thermal
conductivity of 68.88 BTU/ft2/°F/hr (335 kcal/m2/°C/hr), con-
sequently there is little or no risk of condensation in concrete
hulls. Furthermore, such a hull is completely odourless.
Due to the built-in framing and strength inherent in the
material, it is possible to obtain 1 1 per cent more space in a
concrete material-hulled craft than in a similar sized hull
constructed in any other material. It must also be stressed that
concrete-hulled craft may be cast into practically any form to
meet the particular requirements of the purchasers, rather than
the purchasers having to accept a standard design as in
reinforced plastic hulls, or prohibitive costs as in wood and
steel hulls.
It has already been stated that the basic raw materials for
the construction are sand and good quality cement. Both
these items are usually readily available in most countries.
This is, of course, of paramount importance particularly in
under-developed territories and countries that lack their own
steel mills and accordingly have to import the raw materials
for other forms of construction, often using valuable foreign
exchange.
It is also important to note that apart from one trained
technician, it is quite possible to construct vessels in this
concrete using intelligent but unskilled labour.
Finally the advantages may be summarized as follows:
continuous and monobloc structure, smooth surface, perfectly
watertight, no maintenance costs, easily repairable, extremely
strong but without losing a marked degree of elasticity.
COMPARISON OF MATERIALS
Hamlin (USA): A fairly recent complication of the ship-
owner's and naval architect's decision-making function is the
proliferation since World War II of the materials from which
fishing craft can be built. In addition to traditional steel and
conventional framed and planked wood, there are aluminium,
fibreglass-reinforced plastic (FRP), and various ways of using
wood, such as glued strip, sheet and moulded plywood, and
multi-layer parallel laminations. Furthermore, combinations
of materials are becoming more commonplace, such as rein-
forced plastic layers over wood, aluminium structures on hulls
of other materials, etc.
Many criteria arc used in evaluating the various properties
of a building material. One of the most important is its cost,
not only the cost of construction but also the cost of annual
ownership as affected by the building material, and the
expected efficient life of a vessel built of the material. As a
start in evaluating these cost factors fig 31 can be used.
100000
6
» 4
2
10000
£
8 * 4 fi e g
. Construction cost versus displacement as of October 18 1965
These curves were prepared from rather haphazard data
regarding the advertised cost of small and medium-sized
yachts available on the USA market and no great reliance
should be placed in these curves, particularly those for FRP
and aluminium vessels. No attempt was made to classify them
as to quality or end use, but an effort was made to equalize
the basic necessities such as crew and power plants.
The curve for wooden boats has been building up over
several years. It fairly represents the cost of average quality
sail and power yachts built in the USA. Both the FRP and
aluminium curves are based on data obtained during the 1964
New York Motor Boat Show. There were 30 points for FRP
boats, nine for aluminium boats. The curves drawn could
tentatively be taken as representing the cost of average stock
boats of the respective materials.
[315]
There is not a great deal of difference between the selling
costs of stock and custom boats. The production savings of
stock boats seems to be almost wholly offset by the cost of
advertising, commissions, etc., required to sell the larger
production.
Even though there may be a considerable question of the
validity of the curves shown on the graph they indicate the
general pattern of costs with respect to building material and
size. Certainly it would be interesting to see these curves
refined, and also to see a companion graph of curves, based on
annual cost of ownership for the various materials, against
size of percent depreciation in value for each material against
years of life. These three sets of curves would be invaluable in
choosing the building material for a specific design.
In examining fig 31, the curves for wood and FRP seem to
be in an expected relation with each other. The small wooden
boat, with its multiplicity of relatively delicate components,
can hardly be expected to compete in cost with the simplicity
of FRP construction. The large wooden craft, on the other
hand, has only a slightly greater number of parts than its small
counterpart, whereas the large FRP craft is complicated by
framing, cores, etc., to provide necessary strength and stiffness
thus making it relatively more expensive to build.
What is surprising, at least at first glance, is the low cost of
small aluminium craft relative to the other two materials.
This must undoubtedly reflect the ease of building with flat
plates and simple extruded sections as well as the ability to
form and weld large hull sections of aluminium quickly and
cheaply. Certainly the large number of aluminium gill nctters
on the US and Canadian West Coast, with a displacement of
6,000 to 7,000 Ib (2,700 to 3,200 kg), as reported by Leveau
and Brandlmayr would tend to validate the curve of aluminium
costs.
The spread of the curves in fig 31 would seem to indicate a
need for increased attention to shipbuilding and maintenance
costs, these being a major part of any fishing operation.
Perhaps the question is of sufficient importance that the FAO
Fishing Vessel Section would consider establishing a Per-
manent Panel to raise the subject of costs from one of "by
guess and by gosh" to something approaching a rigorous
discipline.
Vcrveij (Netherlands): Although Hamlin himself already
doubted the validity of fig 31, Verveij did not hesitate to call
this graph misleading. Since boats of equal size (taking the
total volume as the base to compare size) have different
displacements if made in wood, aluminium or FRP with FRP
having least weight at equal strength, one is in fact comparing
boats of different sizes when using fig 31.
Lower maintenance balanced higher initial cost
Reid (Canada): As the designer of a fairly large number of
moderately-sized welded steel fishing vessels over the past ten
years he made the same comment to each of the authors of
the FRP papers. The point is made, in all these papers, that
the higher initial cost of the proposed material is more than
offset by the decreased cost of maintenance in comparison to
wood or steel construction. The point is made that steel
requires virtually constant maintenance during its service life.
It has been common practice on the Pacific Coast of
Canada and the USA to use special coatings on all external
steel (except below the light waterline). This coating includes
not only hull steel but deck — deck house and wheelhouse,
funnel, mast, boom, deck gear and hardware.
Originally the coating consisted of sand blasting (or shot-
blasting) of all mill scale followed immediately by metallizing
of all sand-blasted surfaces, using either zinc, aluminium or
lead to a specified depth, usually of 8 to 10 mill thickness.
Since epoxy-based paints have become available, the metal-
lized surfaces are coated with a commercial epoxy paint. In
extreme cases, where inaccessible bilge spaces may occur due
to hold linings, etc., these spaces have also been coated.
US Navy test results recently released indicate that zinc
coatings only can be expected to give a service life of 1 8 to 20
years, there was no doubt of a life of 20 years or better if
epoxy paint was used over the zinc.
Experience has been that these expectancies should easily
be reached. The present cost in Western Canada for such
coatings varies between 75 and 90 cents per square foot
so treated — however, this cost is reduced by the cost of sand
blasting and painting which would have to be done otherwise,
In service damage due to wire being dragged along the
bilges has indicated that the metallic coatings tend to be
carried into any grooves cut in the steel - again in extreme
cases of surface damage it is a simple matter to wire brush or
sand blast damage portions clear and recoat.
With the exception of normal maintenance costs which
occur on any vessel -it is not certain that the notably higher
costs of either aluminium or reinforced plastic can at present
be justified by the unknown but expected lower costs of
maintenance.
Faulting (USA); With the increasing difficulty of obtaining
suitable shipbuilding lumber and personnel with the skills
requisite to the construction of round bottom wooden boats,
there will be an increasing use of sheet materials such as steel,
aluminium and plywood. Its properties of strength and corro-
sion resistance combined with predictable and enduring
connectability by welding, would make aluminium seem
generally preferable to the other two. It is hoped that
increasing availability of the material plus experience in its
use will bring the price of aluminium construction into line
with that of competing materials in the near future.
The usefulness of sheet materials for hull construction would
seem to be greatest in the intermediate size range where the
number of craft built to a single design is usually insufficient
to justify the mould and other costs of reinforced plastic
construction. Further, such craft are frequently constructed
in smaller yards which arc not equipped with all of the metal-
forming equipment necessary for the construction of moulded
metal hulls.
Fyson (FAO): Cost figures for a wooden fishing vessel to
provide a comparison with figures given for aluminium and
plastics can be illustrated as follows. A 52ft (16m) purse-
seiner without fishing equipment or electronics, built in Sene-
gal will cost approximately £14,000 ($40,000) or about £80
($225) per m3. Further figures on cost comparison can be found
in Gurtner's paper.
[316]
PART IV
ENGINEERING
Technical Experiences of Mechanization of Indigenous Small Engine Types and Machinery Installations Curt Borgcnstam
Craft ERKvaran
Hydraulic Deck Machinery
Outboard Engines in Coastal Fishing Frank ( Vibrant Jr. ami Kurt Bruttinger
E Estlander and N Fujinami
Refrigeration Facilities in Small Fishing Boats
The Location and Shape of Engine Wells in Dug-out Canoes Seigoro Chigusa
Thomas C Gillmer ami Oyvind Gulbrandsen Discussion
Technical Experiences of Mechanization
of Indigenous Small Craft
by E. R. Kvaran
Experiences sur le terrain en matiere de mecanisation des petits
bailments autochtones
L'auteur relate ses experiences personnel les dans ce domainc, en
s'attachant particulierement a Installation de moteurs interieurs.
Selon lui, la motorisation dcs bateaux ne suscitc aucun probleme
social s6rieux, tout en permettant un accroissement immediatdu
niveau de vie. De plus, si Ton equipe simultan6ment plusieurs
bailments dans la meme region, la rivalitc umicale qui s'etablira
entre pechcurs les aidera a surmonter leurs difticultes initiates.
L'autcur deer it Installation de moteurs interieurs, tubes d'etam-
bot, etc., dans les bateaux autochtones, ainsi quc les modifications
dcvant etre apportees a la coque. Vient ensuite un expose des
difficultes qui survienncnt generalement sur le terrain, 1'auteur
preconisant, meme au prix de couls initiaux plus eleves, la facilite*
d'entrctien et la fiabilite plutot que la simplicite. La rnise en place
d'un bon service apres vente constituent egalcrncnt un atout
precicux, et eliminerait notamment les consequences sou vent
ndfastes des r6parations cflectuees sur place dans des conditions
primitives.
Experiencias tecnicas en la mecanizacion de pequeiias embarcaciones
exoticas
La descripci6n del autor sc basa en su propia expcriencia, particular-
mente en lo que se refiere a la instalacion dc motores internos.
Arguye que la motorizacion dc los barcos existentes no crea
ningun problema social importante, sino quc ofrece una mejora
inmediata en el nivcl de vida. Ademas, si en una misma regi6n se
transforman varias embarcaciones simultaneamentc, la rivalidad
amistosa induce a los Pescadores a soportar los primeros incon-
venicntes.
Sigue una description del acoplamiento de motores internos y
hclice a popa en las em ha re ad ones existentes, con las necesarias
moditicaciones del casco, explicandosc las dificultades con quc se
tro pie/a normalmente en la practica y abogandose por la facilidad
de manutcncion y la scguridad funcional en ve/ dc por la simpli-
ficacion. aim admitiendo que cl gasto initial cs mas elevado. Un
bucn servicio del vcndedor al cliente es tambien una cnorme
vcntaja pues evita las defectuosas rcparacioncs primarias locales.
A CONSIDERABLE amount has been published on
the various aspects of the mechanization of fishing
craft. Many relative papers are lo be found in the
publications of the Fisheries Department and Bureaus,
in reports by FAO, the Colombo Plan, USATD and
other international agencies, and in papers of the Indo-
Pacific Fisheries Council, most of which have a limited
circulation even amongst those directly concerned with
the subject, while a few papers have enjoyed a wider
distribution in books and in periodicals.
This paper deals with the mechanization of fishing
craft both with respect to the installation of engines for
propulsion and of mechanical devices for handling
fishing gear. It will concern ilself primarily with the
installation of inboard engines in existing craft types
which have not been specifically designed or developed
for use with an engine.
There are still many unmechanized craft which could
profitably be motorized. Many factors contribute to the
retardation of their mechanization: poverty amongst
fishermen is the most potent, lack of organization is
another, and the formation of really effective co-
operatives amongst small fishing operators for the pur-
pose of furthering mechanization has been difficult and
sporadic. Various governmental loan schemes have been
very useful, but the scale on which mechanization of
existing craft has proceeded is nevertheless much too
small.
One of the factors has been competition from com-
pletely new mechanized boat types which, if well designed,
are inevitably more efficient than the indigenous craft.
This would not be a matter for concern, were it not for
the fact that the introduction of new types entails a very
much greater capitalization lhan ihc motorization of
existing craft, and can lead to the abandonment of
usable old boats. A given investment in new boats or
ships may result in increased catches as great as would
result from the same investment in motorization,
although this is not usually Ihe case in a fishery which is
still completely unmechanized. Motorization, on the
other hand, will inevitably provide greater employment
opportunities in the fishing community, and in most
developing countries labour saving is not per se an
objective at the present lime and the dislocation of
persons engaged in fishing can create serious problems.
Motorization of existing craft can thus often be
justifiable as a preliminary step to further development.
This will be true especially in cases where the motorized
craft are capable of exploiting the same grounds with the
same or similar methods as those proposed for the more
highly developed alternate fishing method.
A number of large development schemes have been
proposed for various developing countries involving
investment in factory ships, large catcher vessels and
expensive shore installations. As proposed, these plans
inevitably show rapid capital formation and can be very
attractive, at least to anyone who believes in "more jam
the day after tomorrow". Due to the large capital require-
ments, however, such schemes are critically dependent on
achieving the planned production, and fluctuations in
fishing operations can result in great losses instead of hand-
some profits. Comparable disappointments can certainly
occur in the case of motorization of existing craft, but
the result then is usually that the increase in individual
earnings which was hoped for is not forthcoming, or is
less then expected. Provided that some reasonable
[319]
preliminary trials or investigations have been carried out,
mechanization of existing craft rarely, if ever, leads to an
actual operating loss, if excessive mechanical troubles
can be avoided.
There may be subtle, or not so subtle, sociological
reasons for favouring the mechanization of existing craft,
or the introduction of new but small boat types as
against launching into large-scale operations. Much has
been made of the suggestion that, compared with
agriculture, the fishing industry, the only other significant
basic source of food, is in a very primitive state. While this
may well be so from one point of view, it can be very
misleading when considering the state of modern large-
scale fishing enterprises. These make use of expensive
and complex equipment and the operation as well as the
design and selection of this equipment calls for trained
specialists. In most developing countries the existing
fishing community is not the place to find such specialists,
nor even candidates for training. The rapid development
of a large-scale fishing industry can lead to the existing
fishing community being completely by-passed, with a
new set of men taking over the new fishing industry. The
old industry is then doomed to stagnation and eventual
disintegration.
The introduction of small-scale mechanization can do
much to prevent this situation from arising. Experience
with engines will help to prevent antagonism toward still
more advanced techniques. Even more, it will tend to
limit the drift away from the existing fishery which is
typical of successful fishermen and particularly of their
educated sons in countries where fishing does not enjoy
high social standing. When the industry can offer a place
for educated and highly trained men, at least in the top
levels, it will no longer be necessary for members of the
younger generation to turn to medicine, law or other
professions to prove their worth and to seek their
rightful place in society.
MAIN TYPE OF INDIGENOUS FISHING CRAFT
Almost anything which floats and has sufficient buoyancy
to carry a man can be used as a fishing craft. Anthro-
pologists speculating on the origin of water travel usually
conjure up pictures of primitive man paddling astride a
log, lashing together poles or bamboos or stitching skins
or bark on to a frame to create the first boats. Whatever
the truth may be, these three models do represent
archetypes of the most common indigenous fishing craft
still in use. The log, long since scooped out and shaped to
form a dug-out canoe, is often provided with one or even
two outriggers for increased stability, and craft may be
made from intricately shaped and jointed pieces to give
greater seaworthiness and manoeuvrability. The kayaks
and umiaks of the Eskimo and the American Indian
canoes are perhaps the most widely publicized of the
sewn boat types but various woven or stitched boats used
in Africa and South-Asia are of far greater economic
importance. Finally, and obviously of much later origin,
are planked boats, which free the builder from the
limitations of size and shape imposed by the more
primitive constructions. There are no hard and clear
lines of division between these four main boat types, as
combinations are common. Dugouts may be enlarged
by adding a planked or woven superstructure, planks
may be sewn or lashed together and wooden boats may
have a woven matting bottom. One has a tendency to
think of non-mechanized, indigenous craft as being
something primitive. In many cases this is so, but in
others the craft represent a very high state of develop-
ment with respect to the lines, the construction, the
workmanship and suitability for the purpose for which
they are intended. Even when labouring under the severe
handicap of not having available metal fasteners or
suitable timbers, beautiful, effective, and seaworthy
craft have been developed, as in the case of the fishing
boats of the Maldive Islands. Tank tests carried out for
FAO on Pakistan fishing boats show that the hull form is
difficult to improve on from a propulsion point of view.
The justification for mechanization lies in the economic
field. No man's time is today worth so little that he can
afford to depend on the vagary of the wind.
The construction of the boat will naturally affect the
possibilities of mechanization and the manner in which it
can best be carried out. Inboard engines, especially diesels,
require reasonably rigid hulls and ones which are not too
narrow, while outboards can be mounted on almost any
hull form provided it is not too high. Even a bathtub
has been fitted with an outboard and used as a boat to
illustrate how far mechanization can be carried.
INSTALLATION OF INBOARD ENGINES
The installation of an inboard motor in an indigenous
craft usually presents many more problems than does
that of an outboard, as it entails at least three or four
separate entities which must be reasonably harmonized
if a satisfactory job is to result. The engine must be
firmly mounted in the hull and the stern gear fitted in
proper relationship to the engine on one hand and to the
propeller location on the other. Auxiliaries such as the
water inlet, the exhaust piping and silencer, air-ducting
and fuel tank must be located and fixed so as to function
effectively with a minimum of interference to the opera-
tions to be carried out. An engine box or house may be
required and, usually, a completely new rudder, differing
in design and mounting from the original.
A basic characteristic of most non-mechanized craft is
shallow draft, and the first decision to be made is what
to do about this problem, preferably before the engine
has been purchased or selected. If the shallow draft is
essential for the operation of the boat, a lifting propeller
or a high-speed engine with direct drive must be used.
The former is rarely satisfactory except on hulls specifically
designed for it, which would of course not be the case
in this instance. When a high revving propeller is used,
especially close to the surface, loss of efficiency and
aeration will have to be tolerated, and even so it is
usual to find that the original draft is so small that even
with the smallest practicable propeller some increase in
draft must be accepted. This is usually brought about by
reconstructing the stern of the boat, or more commonly,
by adding a false keel.
Unless the installation is being carried out by a naval
architect or engineer it is unlikely that any drawings will
[320]
be made and it is then easy to underestimate the size of
the keel required, not to mention the angle of installation.
Most indigenous craft are hauled up on a beach, regularly
or occasionally. After mechanization it is often found
that this is much more difficult than before and not only
due to the added weight. As long as a boat has a straight
keel it can be pulled up on rollers or blocks. If a false
keel is added and it does not extend the full length of the
bottom of the boat, there will be a "dog-leg" in the keel
line, which will cause the boat to lift clear of the rollers
under the middle and to drop down each time the end
of the keel passes a roller. This can add surprisingly to
the effort required to pull up the boat, especially with
primitive equipment and on a soft surface. Lack of
adequate protection for the propeller in the form of a
strong skeg under it will make the problem much worse,
and what was formerly a simple routine job may take on
the aspects of a major undertaking.
The straight triangular-type false keel which is recom-
mended for shallow boats will be about as deep as the
diameter of the propeller, if it is to be made deep enough
to provide material for a propeller or rudder-skeg and
should be as long as the straight part of the bottom
of the craft in the case of a dugout, or as long as the keel
in the case of a framed boat. It can be tempting to reduce
the size of the false keel by not allowing for the skeg,
and adding one under the end of the keel, but this has the
same drawbacks as fitting a short keel, namely, the keel
line will not be straight and hauling up is hampered. If it
is necessary to reduce the size of wood used to make the
false keel, it is much better to bring it up to the level of
the stern tube only and to use a separate piece above the
tube, that is to split the deadwood along the shaft
centreline. This will also be a big help if the boring tools
available arc inefficient, as is commonly the case when
local craft are being fitted with engines.
Draft Problems
Shallow draft creates problems inside the boat as well
as outside. If the engine must be fairly high relative to the
waterline and the shaft is short, the angle of installation
may be excessive. A longer shaft will not only result in lost
working space but may seriously weaken the keel struc-
ture as the angle of incidence of the shaft to the keel
becomes small and the hole or slot which must be cut
can become quite long and detract appreciably from the
strength of the keel. In this respect dugouts made from
good solid trunks may be easier to mechanize than
planked craft. The engine, with stationary-type mounting
lugs, can be placed almost directly on the thick bottom
mounted only on a wedge to give the required angle and
the weakening due to the long stern tube hole is not
significant.
In framed boats the distribution of the weight and
vibration of the engine on to a number of frames be-
comes essential if subsequent stern gear troubles and hull
leaks are to be avoided, and long, deep engine bearers
are required. For such installations stationary-type
mountings at the bottom of the crankcase are most un-
satisfactory and marine-type mountings are very much
preferable. Here a reduction gear which drops the pro-
peller shaft below the crankshaft centre line is also very
useful in reducing the angle of installation.
Normally one would avoid bolting engine bearers
through the planking, much less the engine holding down
bolts. In the case of local craft this is sometimes not only
unavoidable but may be desirable either to strengthen
the structure or for the sake of simplicity. Take for
example the case of a dug-out canoe in which an engine
with a stationary-type mounting is to be installed. The
engine bed can consist of a single flat wedge-shaped
piece of wood, shaped to the curve of the hull on the
bottom side and sloped to the required angle on top.
The boat will probably require a false keel, and two
extended keel bolts arc sufficient to hold the bed down.
Four or six engine bolts through the bed and the thick
bottom complete the installation of the engine itself.
In framed and planked boats the need for long engine
bearers was mentioned earlier. Such bearers will often
do little real distributing of the weight unless a new
system of floors is introduced at the same time and
through bolting through the hull will often be the only
practicable solution. In boats which have a system of
heavy frames, longitudinal strengthening may be more
important than adding floors, as in many such boats
the planking alone supplies all the longitudinal strength,
the keel being but a slightly thicker plank in the centre
of the boat. When long, heavy engine bearers are
introduced, excessive working of the planks from the
turn of the bilge up to the gunwale may result unless
stringers or longitudinal clamps are also provided. Once
a boat has been mechanized it will be called upon to
meet waves head on and will suffer much more slamming
than it did as a sailing vessel. This is probably a more
important reason for providing additional strengthening
than is the vibration of the engine. If the hull is very
flexible, it may retain much more of its original nature
if an outboard motor is fitted, as in this case strictly
local stiffening will usually suffice. If the engine is used
solely as an auxiliary to sail, this problem of facing head
seas will not be so important, but experience seems to
show that engines never remain auxiliaries for long and,
in fact, the problem becomes that of ensuring that a sail
is available for emergency use.
Stern gear is usually a source of much trouble in the
operation of mechanized local craft. In the first place, it
may be difficult to install properly, without excessive
alterations in the stern of the boat. The need for careful
workmanship while installing the stern gear is usually
only appreciated after repeated and costly failures. This
applies not only to shaft alignment but to details such as
obtaining a good fit for the stern tube, ensuring that the
stern bearing flange scatings are strictly at right angles to
the shaft line, and that the mounting of the bearings
and the various blocks and other bits and pieces which
will inevitably be required are solid enough to stand up
to protracted use.
Most local craft will require a long stern tube due to the
usual combination of a flat bottom, a level keel line and
shallow draft, and fitting a real shaft log may be difficult.
The apparent shaft log is likely to be in reality a cover for
the stern tube and, in fitting this tightly to the tube to
prevent leakage, it is easy to distort the tube or the
321]
mounting of the inner bearing flange, thus paving the
way for future stern gear troubles.
If beaching or shallow water operation is not contem-
plated, the installation can be greatly simplified by using
a strut-mounted, outside bearing and eliminating the
long stern tube as well as the false keel, but this will
result in an extremely exposed propeller unless the bottom
line of the craft has considerable curvature and compara-
tively more draft than is usual.
TROUBLES COMMONLY ENCOUNTERED
Mechanical troubles can lead to the failure of attempts
to introduce motorization. In a typical case, the operator
will be someone with no previous experience with engines,
and he will usually receive a very scanty preparation for
his new role. Often he will have difficulties in obtaining
skilled help for his repair work, either because of a
remote location or because he finds the charges of an
experienced mechanic or workshop too high. (These
same charges might be considered reasonable by, say,
the operator of a fleet of diesel trucks.) Unless the sales
agent of the engine, the government, or some other body
take definite steps to assure regular servicing and
moderately priced repairs, the maintenance field is almost
sure to be taken over by poorly qualified persons;
bicycle repair shops, for example, can blossom into fully
fledged diesel repair stations over night. The net result is,
of course, premature failure of the engine and exorbitant
repair bills, if the engine is not abandoned altogether.
This problem is a difficult one to solve, and circumstances
will vary from place to place. In the first instance the
onus will rest on the engine manufacturers or their
export agents in selecting good representatives in the
importing countries. The criteria for good agents
for the purpose of dealing with small-scale fishermen
may be quite different from what is required for dealing
in other lines of machinery, and the possibility of having
a different representative for small marine engines than
for other products is worth considering. A system based
on sub-agencies for this purpose can also lead to im-
provements in service if the sub-agents are given a
fair deal by the main representatives. The practice of
selling engines cheaply and making the profit on the
sale of spares is particularly unfortunate when applied
to motorization of fishing craft, as operating money is
in chronic short supply in this business. Take for example
the case of a fisherman who has been earning, say, the
equivalent of £10 (US $28) per month. He borrows
money for a small engine and mechanizes his craft for
£400 (US $1,120). After paying all loan payments and
operating expenses, including his salary, he is left with
a net profit of 50 per cent per year or, say, £15 (US $42)
per month. This money will most likely be used to aug-
ment his family expenditure, not to form a reserve against
unexpected major breakdowns. On the assumption that
his loan was obtained at reasonable rates, he would be
better off if he had paid more for the engine, made smaller
profits, but could be assured of cheap repairs. This point
is beginning to receive recognition. In Ceylon, for ex-
ample, the prices paid to engine dealers for small engines
given on loan includes provision for over £35 (US $100)
for various specified free services.
Early Problems
During the early stages of motorization there were
many who felt that the simplest engines possible, such as
hot bulb semi-diesels would be ideal for this purpose.
This has not proved to be the case, mainly because these
engines need an operator adept at carrying out minor
adjustments at frequent intervals, and seem to be most
popular in countries with a long history of small boat
mechanization, for instance, the Scandinavian countries
and Japan. Full-diesels, which require little or nothing
in the way of adjustments by the operator, if they are
periodically serviced by a qualified maintenance man,
have proved more satisfactory, but by no means trouble-
free either.
The most common source of trouble in a mechanized
boat is, however, probably not in the power plant at all
but in the stern gear. Much of the difficulty can be
attributed to poor workmanship in installing the stern
gear and engine or to lack of follow-up checks during the
first critical weeks. But a great deal of the trouble stems
from the use of inferior or unsuitable materials or com-
binations of materials, leading to early corrosion and
breakage. As many engine manufacturers do not make
their own stern gear, problems of assessing responsibility
are somewhat complex. There are numerous cases of
engine makes which have operated successfully for some
time and then have begun to suffer from premature
stern gear failure. Such cases almost always prove to be
the result of a change in the materials used by the
original supplier, sometimes without the knowledge of
the engine manufacturer or of his agent, if he is obtaining
the gear from a different source.
The motorization of indigenous craft is by and large
being carried out in tropical or sub-tropical countries.
Materials which have proved satisfactory in temperate
waters do not always stand up to the higher temperatures
and possibly greater salinities that they will be called upon
to meet under the new conditions. The rate of chemical
reactions is, roughly speaking, doubled for an increase
in temperature of 20°F (10°C). Operation in waters
25°F to 35°F (J5°C to 20CC) warmer than the home seas
will lead to corrosion rates 3 to 4 times greater, and the
original reasonable life span will not be approached at
all.
Poorly designed or selected propellers contribute to
unsatisfactory performance. Many or most indigenous
craft have lines very different from the boats considered
normal by the engine manufacturer. While a few companies
have taken the trouble to make a realistic propeller
selection for these craft, this is the exception rather than
the rule, and it has even happened that the propellers
supplied (which were obtained by the engine manufac-
turer from an outside source) differed significantly from
the manufacturer's own specifications, sufficiently so as
to cause overloading and bearing failure.
Gearbox difficulties
Gearbox troubles, due to maladjustment, are all too
common and unnecessary but are not to be blamed on
[322]
the engine manufacturer. The selection of undersized
gear boxes, taking into account the rough treatment
that they will inevitably be subjected to, is another matter.
One chronic trouble with many gearboxes is that it is
difficult to obtain a positive neutral position, and for
some fishing operations the continuously rotating
propeller is a hindrance. One of the contributing factors
is that the engines are often stored for long periods under
tropical conditions before being installed, and the gear-
box oil becomes gummy, causing the clutch plates to
stick. The simple remedy of thorough flushing is not
always carried out, with the result that from the first day
the fisherman suspects that he has received a defective
piece of machinery. Unfortunately, however, flushing is
by no means a sure-fire cure for this defect. The writer has
been guilty of making his own contribution to gearbox
troubles. In the interest of standardization, identical
shafts were specified for engines with and without
reduction gears. Due to the rigidity of the shafts even
comparatively slight misalignment was sufficient to
cause failure of the gearbox output shaft on the direct
drive engines.
The design of the diesel engines commonly used in
mechanizing small fishing craft can vary in a great
number of details although there arc very few funda-
mentally different types. A sales feature commonly
overstressed is "simplicity". An engine with exposed,
lubricated valve gear, no air cleaner, a wire mesh
lubricating oil strainer, no flywheel cover, gravity feed
fuel supply and no instruments can certainly be described
as "simple", compared to an engine with a totally
enclosed, force fed lubrication system with renewable
filter elements, an underslung oil bath air cleaner, a fuel
lift pump, lub oil pressure gauge, water cooled exhaust
manifold, raised hand starter, and so on. But does this
make it more desirable, particularly from the point of
view of an inexperienced operator? By no means. What
he wants is an engine which is easy to start, and will run
for long periods with minimal attention. Most of the
"complications" which over the years have been added
to marine diesels are there because they contribute to
these ends. They all add to the price as well as to the
value of the engine and this should be given full considera-
tion when comparing engine quotations.
In actual operation the troubles met with cover the
whole range of possible faults. As experience is gained,
many of the trivial ones disappear. Air locks, lack of
lubrication, loose accessories, rusty chains, leaking pipe
connections soon become, or should at any rate become,
things of the past. Running with poorly adjusted fuel
pumps or injectors, with worn bearing or pistons, with
inadequate cooling water circulation, with dirty oil will
go on for a much longer time and, fair or not, it is during
this period that judgement will be passed on the merits of
a particular brand of engine. Engines which cannot
stand up to rough treatment of this nature will be found
wanting, and the operators will not be prepared to accept
the blame for failure if other engines can "take it"
better than their own. The ability of an engine to with-
stand abuse, in addition to legitimate demands for long
hours of continuous full throttle operation alternating
perhaps with long periods of idling operation, will
depend on design factors about which the operato-
knows nothing and cares less. On the other hand it is
unlikely that he will be over-fussy about fuel economy
nor, within limits, about lubricating oil consumption.
Replacements
When an engine, which is still under the manufac-
turer's guarantee, develops trouble of any sort, it is
axiomatic that there will be disagreement between the
operator and the engine agent regarding the responsibility
for repairs. Most manufacturers' guarantees are really
of very limited value to a fisherman in a remote area of a
distant country. The usual stipulation is that the damaged
parts be returned carriage paid to the factory, and that
they will be replaced free of charge if the manufacturer
finds that the fault is due to a defect in material or
workmanship. Fortunately, many field agents, often
with the approval of their principals, are more liberal
and will replace and refit parts, without sending them
first to the factory, in cases where they are not able to
account satisfactorily for the cause of failure, without
necessarily acknowledging that it was due to a factory
defect.
This kind of service would again indicate that profit
margins should not be too small and that it is desirable
to have some sort of arbitration system worked out in
advance to decide in dubious cases. Many of the initial
difficulties could be minimized by proper training of the
fishermen in the use of their engines. It does not seem to
be fair to place this burden on the engine sales, unless it
is being paid for specifically. The care and operation of
engines is becoming a necessary part of the knowledge of
almost any fisherman and should become a part of his
general education, with such formal training as is
necessary coming from a public institution of some sort.
Once mechanization is well established this problem
tends to take care of itself as far as small engines are
concerned, as young fishermen will learn to handle
engines long before they become engine owners.
There is strength in numbers. The writer feels that
mechanization has a very much better chance of success
if it is not attempted on too small a scale in any one
given locality. The first members of any community to
take to the use of engines must expect to meet opposition
and, if an opportunity presents itself, ridicule. If one or
two such craft are introduced they may well make a
brave showing, until the first inevitable troubles appear.
As the early profits are put back into repair bills the
operator may be hard pressed to justify his actions to
everyone who "told him so". If this happens a few times
he may well be prepared to yield to majority opinion,
give up, and revert to doing what every one else is doing.
The situation is quite different if one or two boats are
out of action while six or seven others are still earning
good money. They will act as a spur and every effort will
be made to get the laid-up craft back into operation as
quickly as possible.
AIDS TO MECHANIZATION
Much could be done to improve the efficiency of mecha-
nized local craft if the equipment to be installed were
[323]
L2
especially designed for this purpose, or were made
flexible enough so that it could easily be adopted to this
use.
Outboard motors which can be provided with ab-
normal extensions fit many types of local craft much
better than standard outboards, or outboards extended
by 4 in (101.6 mm). At least one manufacturer has
developed abnormally long motor shafts for this specific
purpose, but unfortunately most manufacturers are so
far not prepared to vary their production schedules to
cater to this specialized market. Outboards with low
propeller speeds, designed for thrust rather than speed,
are also beginning to find their way into this field but
again only a minority of engine manufacturers has
responded to the need for development along these lines.
A true light-weight diesel outboard would find a
tremendous market as far as indigenous craft are con-
cerned, but none has appeared so far, despite some very
attractive advance advertising. In the meantime inboard/
outboard drives or diesels fitted to outboard drives could
become very useful in this field if they were designed with
local craft in mind. Operating costs are of vital import-
ance to most operators of mechanized fishing boats,
and in many cases where loans for the initial purchase
are available, the operating costs take on greater signifi-
cance than initial costs, and this fact creates a great
demand for diesel units rather than petrol.
In many developing countries petrol is associated
with luxury road transport and is heavily taxed, while
diesel fuel is primarily associated with industry and
public or goods transport and is consequently marketed
at a much lower price. In these countries inboard
engines are almost inevitably diesel, and outboards
would become so also if it were to become possible.
Duty-free petrol for fishermen is often advocated, but
in fact this can create a very undesirable situation in
countries where the price of a few gallons of petrol is
worth the average daily income of a fisherman. A 30 hp
engine operating at full load for 8 hr per day will require
something of the order of 16 Imp gal (19 gal), (73 1) of
petrol per day and with a tax rebate of, say, Is 2d (US
$0.15) per gal, this could have a black market value
approaching 10s (US $1.40) per day, a sum sufficiently
high to tempt the operator to stay at home whenever,
fishing prospects are poor or for some reason he is not
keen on going out. Obviously a fisherman used to earning
£10 (US $28) per month would be much more tempted
than one who makes £70 (US $200), and elaborate
controls would be required, especially where fishing is
completely decentralized.
Installation is much easier if the engine can be installed
at a large angle, even up to 15 degrees. A large angle of
installation will not always solve the problem, unless the
gearbox mounting is such that it does not cause dif-
ficulties in the narrow and limited space at the extreme
stern. Generally speaking it is a great advantage to have
all the mounting lugs or flanges on one straight line, but if it
is necessary to install theengine as far aft as possible this can
be a disadvantage, as the rear mounting lugs will be too
low when the engine is installed at a large angle, and the
engine will sit too high. A possible solution would be to
have reversible mounting feet on the gear box. In the
normal position they would lie on the same line as the
engine holding down lugs. When reversed the feet would
be higher on the side of the gearbox. A stepped engine
bearer would be used, giving adequate thickness under
the gearbox feet, but still permitting a low centre line
for the engine. Fig 1, (a); (b); (c).
0 Normal installation
Aft Installation
© Aft installation
Gtarbox-lufli rtvened
Fig I. Use of stepped engine bearer
Improvements in lifting-type stern gear would make it
much more popular. The most common source of
trouble in this stern gear is the universal joint, which is
usually made so that the slightest wear introduces
excessive play. While universal joints of much higher
quality are available for general purpose use, none appear
to be obtainable for use in sea-water. The lifting mecha-
nisms can also stand much improvement, especially
with regard to ensuring proper alignment in the working
position.
Life of bearings
Stern bearings which depend on water lubrication wear
out much faster if the housing is not designed with
water scoops to ensure positive water flow through the
bearings. Diversion of part of the cooling water for this
purpose has not proved too successful on various local
boat types. The flow pattern around the external bearing
may well prove to be such that very little, if any, of the
water passes out this way and the system may not show
any improvement over simply submerging the bearing.
Best results have been obtained with water lubricated
bearings which are mounted externally, that is, on the
end of the stern tube rather than being fitted inside the
tube. The reverse is true for grease lubricated bearings,
which function best if the white metal is to a large
[324]
degree inside the shaft log or deadwood, particularly if an
effective oil seal and sand excluder is provided behind the
white metal. Bearings with renewable white metal
sleeves are much easier to maintain than bearing housings
which require re-metalizing. Generous grease cups or,
better still, small grease pumps for the stern bearings
more than justify the slight extra cost.
In the writer's experience the most suitable stern gear
for small fishing boats has a grease lubricated white
metal inner bearing and a water scoop lubricated
rubber outer stern bearing. For some installations the
protruding outer bearing may create space difficulties, in
which case an outer white metal bearing in the stern
tube and grease lubricated through the stern tube would
be the choice. Installation requiring a grease tube to be
run through the deadwood can be troublesome,
particularly if the deadwood is made up of various
pieces, as may happen when a false keel has been
necessary.
Even if some sort of engine box or house is provided,
and often it will not be, the engine is going to be exposed
to spray and a humid atmosphere and rust will form
between repaintings. The use of sheet metal should,
therefore, be avoided as much as possible in the designs
of mountings for gauges, air cleaners, etc., as well as in
these parts themselves. Screws and other fasteners
should be corrosion resistant, especially the fasteners for
the exhaust manifold and piping. For the same reason
external threaded piping should be avoided. If a dry-type
air cleaner is used it should not be one which can rust to
pieces and gradually be sucked into the cylinders.
It is impossible to trace the relative importance of the
various factors leading to excessive cylinder wear on
small marine engines and the operator is usually blamed
for having neglected his oil changes or his injectors, but
a quite considerable number of worn liners and pistons
can beyond a doubt be attributed to the consumption of
wire mesh from cheap air cleaners.
The writer has a strong preference for the under-slung
type of oil-bath air cleaner or the centrifugal oil bath
despite the fact that these are somewhat bulky and that
their mounting on the engine often leaves much to be
desired. Automotive-type air cleaners not only tend to
rust internally above the oil level but there is also a
danger of the oil content being sucked into the cylinder,
with drastic results in a rough sea. In any case these
air cleaners only work effectively if mounted horizontally,
but on most engines they take on the same inclination
as the centre line of the crank shaft.
Starting ability
The most important feature of an engine from the
operator's point of view is the ease with which it can be
started. As far as external accessories are concerned
starting will involve the cranking system, practically
always by hand for smaller indigenous craft, the
decompressor arrangement, and such starting aids as may
be provided for the various makes of engines. Overhead
hand starters are, generally speaking, the most satisfactory
particularly if attached to the crankshaft rather than the
camshaft. Loose starting handles which fit on to the end
of the camshaft or crankshaft are the least desirable,
especially if it is necessary to build up an external support
for the handle. Rigid mounting of the raised shaft is the
first requirement and easy servicing of the release pawls is
the next one. Effective chain tighteners will add very much
to the life of the chain, and this point could stand
improvement in a number of current designs. Shifting
the shafts support to tighten the chain is not a very
satisfactory method. Not only do the brackets tend to
work loose, but there is the danger of the shaft binding
if the adjustment is not carried out properly. If an idler
wheel is used, it should be reasonably proportioned and
firmly mounted. A spring loaded chain follower prob-
ably offers the best solution. In any case, the inclusion
of a half link in the chain to permit shortening after some
time would aid matters but is rarely if ever found. To
prevent rotation of the raised shaft when the engine is
running due to drag in the free wheel mechanism, a
small friction disc is useful. The handle of the raised
hand starter should be removable, as otherwise it
constitutes a definite hazard at the time of stopping the
engine, which may kick back as it comes up against the
compression for the last time. On the other hand it is
annoying if the handle falls off by itself each time it is
released.
The desirable type and location of the decompressor
will depend on the type of hand starter, but it should be
such that starting by one man is easy. Automatic de-
compressors are not desirable, as the number of turns
required before releasing depends too much on the
strength of the operator and on the condition of the
engine.
Individual decompressors for each cylinder can be
useful, particularly with hand starters fitted directly to the
flywheel, or in cases when one cylinder is in better
condition than the others.
Of the various starting aids available, the writer has
found that the most useful one is a small cup permitting
the introducton of a measured quantity of lubricating
and fuel oil mixture into the inlet manifold or better still
into the combustion space. Self-igniting paper introduced
into the combustion space can also make starting very
easy, but the igniters tend to be sensitive to moisture
during storage, and are usually not at hand when
required. Certain slow speed engines with heavy con-
necting rods and cast iron pistons are provided with
cups for introducing petrol during starting. While this is
all right for the engines concerned, it does encourage
bad habits and the operators and mechanics carry this
practice over to high-speed engines where the result is
bent connecting rods, or worse.
Many local craft are very narrow, which makes
accessibility even more important than usual. The fact
that the boat is not designed to take an engine can cause
further problems. For example, it was suggested above
that the foundation for the engine in a dugout can often
be made of one solid piece. This will not be possible if the
lubricating oil can only be drained out through a plug
under the centre of the engine. Even in hulls using proper
engine bearers such plugs become very inaccessible after
a series of floors has been added. Drains at the front end
of the crankcase are also found in converted stationary
engines which must either be mounted dead level, which is
[325]
usually not possible, or the oil must be removed through
the side covers. Small drain pumps would solve these
problems adequately, but these are far from being
standard fixtures. Lubricating oil filters, especially if
built into the crankcase or sump, can be difficult to
remove after the engine has been installed, and external
filters often interfere with the engine bearers or floors.
Sump strainers should be removable for cleaning
without the necessity of dismantling the engines. Auto-
motive or tractor-type engines modified for marine use
often present particularly acute accessibility problems as
it is no longer possible to drop the sump to get at the
lower part of the engine.
One can naturally not expect standard production
series to be radically altered to suit this one type of
application but there is no doubt that a few firms
specializing in, or paying attention to, this market
could achieve a considerable volume of business in
marine engines and accessories especially modified to
meet the needs for mechanization of indigenous craft.
FAO Naval architect Erik Ext lander installed the outboard (right) on a
Ceylonese Kattumaran log-raft. His daughter participated in trials to
convince fishermen of the safety of such an installation. An outboard
motor enables the Ivory Coast fishermen (below) to reach the better
fishing grounds faster. Some of the catch is shown by a member of the
crew, while another removes the outboard.
[326]
Outboard Engines in Coastal Fishing
by E. Estlander and N. Fujinami
Utilisation des moteurs hors-bord pour la p&he c6ti6re
Soixanle-dix pour cent des bateaux de peche en usage dans le
monde, notamment en Asie, en Amdrique du Sud et en Afriquc, ne
sont pas encore motorises. Pour les bateaux de petite taille, la
solution la plus facile — et fr^quemment la seule possible— est la
pose d'un moteur hors-bord. Les auteurs procedent £ une comparai-
son fondde sur des essais effectues & Ceylan, entre 1'installation dc
moteurs interieurs ct de moteurs hors-bord, des points de vue de la
fiabilite du moteur, du rendement et de reconomie. 11s enumfcrcnt
en conclusion les caracteristiques ideales d'un moteur hors-bord
destin* & la pcche.
Motores fucra de bordo en la pesca costera
El 70 por ciento de las embarcacioncs de pesca del mundo se halla
todavia sin mecanizar, principalmente en Asia, America del Sur y
Africa. El metodo mas facil para lograrlo en las embarcacioncs
pequeftas consistc en instalar motores fucra dc bordo, siendo esta
frecuentemente la unica solution. Se compara la instalaci6n dc
motores fuera de bordo/cntrobordo dcsdc cl punto de vista dc la
seguridad, cficiencia y cconomia del motor, basandosc en las
experiencias tenidas en Ceilan. Por Ciltimo, se enumcran los re-
quisites de un motor ideal fuera de bordo para fines pcsqucros.
THE developed fishing nations now tend to operate
large highly industrialized undertakings. This is
not so in many developing countries where the
dense coastal population cannot be absorbed into other
industries. The lack of harbours, marketing facilities
capable of handling the large catch, and also the necessity
to concentrate those employed in fisheries in a few large
base ports rather than in the scattered villages makes
heavy industrialization problematical at the present time.
Development of fishing industries should, therefore,
be made step by step. There are many areas where small-
boat fishing is profitable and the introduction of nylon
nets and mechanized craft to such areas have made
coastal fishing an important factor in the local economy.
According to the FAO Yearbook of Fishery Statistics
1962, the approximate total number of fishing vessels
in the world is 1.5 million (table 1). It is assessed that one
million or 70 per cent of these vessels are still un-
mechanized, and these are mainly concentrated in
Asia, South America and Africa. If table 1 is analysed
into countries and local areas, it is obvious which
regions of the world arc suitable for mechanization
(tables 2 to 7).
This paper deals with the mechanization of inshore
fishing vessels up to 30 ft (9 m) and the advantages of
outboard propulsion for such vessels.
INBOARD INSTALLATION
Until recently small craft were mechanized by light in-
board diesel engines, ranging from 5 to 40 hp.
Difficulties have been encountered with inboard
engines, however, partly due to the poor design of the
stern gear. Even well designed stern gears suffer because
of poor boatbuilding and mishandling of the boats. The
main difficulties are: (a) The incorrect installation of
engine beds and the shaft log, accommodating the engine
and the stern gear, causing non-alignment which results
in worn-out bearings and shaft, (b) Sand and other
foreign material, depending on the design of the pro-
peller bearing, may also cause bad wear, (c) Incorrect
design of the stern disturbs the even flow of water to the
Africa
America North
America South
Asia
Europe
Oceania
Total
Total
94,851
144,792
140,230
930,251
228,905
11,435
1,550,464
TABLE 1
Mechanization of fishing vessels by regions
Powered
sub-total
inboard
outboard
(7,883)
(750)
(3,360)
(108,604)
(975)
(1,809)
(9,767)
(536)
(599)
(240,164)
(9,503)
(960)
(98,872)
Z
(465,290)
(11,764)
(6,728)
Non-Powered
(69,748)
(25,500)
(129,354)
(689,861)
(112,082)
(1,026,545)
Note: The totals in the left-hand column are not the exact sums of the sub-total of powered boats and non-powered boats in the other
columns. Similarly the sub-totals of powered boats are not the exact sum of inboard boats and outboard boats. This is because the
data was incompletely reported, with some countries presenting a full breakdown and others, only over-all totals. The bracketed
figures therefore have no consistency, but give a rough idea for each item. Vertical addition of the above figures does not reflect this
inconsistency.
This remark also applies to tables 2 to 7. The figures of outboard engines are not well shown but considerable numbers of them are
used in various countries, for example Uganda, Ceylon, Malaysia, Japan, USA etc.
[327]
Total
TABLE 2
Mechanization of fishing vessels in Africa
Powered
Non-Powered
sub-total
inboard
outboard
Dahamay
22,502
2
1
\
22,500
Ghana
10,480
2,218
268
1,950
8,262
Ivory Coast
330
180
60
120
150
Libya
416
117
74
43
299
Mauritania
25
3
3
22
Mauritius
1,754
180
24
156
1,574
Melilla (1961)
1,821
71
1,750
Morocco
2,552
817
-_
.
1,735
Mozambique
3,805
47
47
—
3,758
Niger
168
14
14
„ —
154
Portuguese Guinea
116
6
—
—
110
Reunion
406
359
204
155
47
Sao Tom6 and Principe
384
.
—
384
Senegal
6,859
874
27
847
5,985
Sierra Leone
2,660
60
20
40
2,600
South Africa
5,444
1,301
4,143
South West Africa
487
128
.
359
Tanganyika
5,409
37
3
34
5,372
Togo
2,898
4
„...
4
2,894
Tunisia (1958)
3,652
—
—
—
—
Uganda
5,900
1,450
—
—
4,450
UAR (Egypt) (1958)
13,568
Zanzibar and Pemba
3,215
15
5
10
3,200
Total
94,851
(7,883)
(750)
(3,360)
(69,748)
Antigua
Bahama Islands
Barbados
Bermuda
Canada (1961)
Cuba
Greenland (1960)
Grenada
Guatemala
Martinique (1960)
Mexico (1957)
Netherlands Antilles (1959)
Panama
Puerto Rico
St. Pierre and Miquelon
Trinidad and Tobago
USA (1961)
Total
TABLE 3
Mechanization of fishing vessels in America, North
Total
Powered
Non-Powered
sub-total
inboard
outboard
286
81
66
15
205
1,320
70
70
.
1,250
598
528
490
38
70
250
—
—
. —
—
45,282
30,390
—
—
14,892
3,471
2,660
. —
—
811
1,750
522
—
—
1,228
610
55
50
5
555
29
29
29
—
—
1,036
—
—
—
— .
8,566
—
—
..._,
—
712
—
—
—
—
251
231
. —
—
20
1,300
631
160
471
669
124
—
—
—
—
1,720
1,390
110
1,280
330
77,487
72,017
—
—
5,470
144,792
(108,604)
(975)
(1,809)
(25,500)
Total
Argentina
Brazil (1961)
British Guiana
Chile
Ecuador
Peru
Surinam
Venezuela (1958)
Total
TABLE 4
Mechanization of fishing vessels in America, South
Powered
Non-Powered
sub-total
inboard
outboard
1,357
438
414
24
919
119,396
3,360
—
—
116,036
805
421
91
330
384
5,819
1,971
__
3,848
4,960
260
—
—
4,700
1,109
—
—
—
—
480
276
31
245
204
6,304
3,041
—
—
3,263
140,230
(9,767)
(536)
(599)
(129,354)
[328]
TABLE 5
Mechanization of fishing vessels in Asia
Total Powered
Non-Powered
sub-total
inboard
outboard
Aden
6,510
110
90
20
6,400
Brunei (1959)
226
Cambodia
19,113
205
135
70
18,908
Ceylon
20,701
1,557
1,557
19,144
Cyprus
422
346
12
334
76
China (Taiwan)
26,393
6,051
20,342
Federation of Malaya
22,109
9,770
12,339
Hong Kong
9,769
5,267
,
4,502
India (1961)
85,000
2,020
—
82,980
Indonesia (1961)
198,626
3,157
....
195,469
Iraq
1,820
80
30
50
1,740
Israel
392
122
270
Japan
404,035
191,899
212,136
Korea, South (1961)
42,300
5,015
_..
37,285
Macau
2,908
176
—
2,732
Pakistan (1960)
30,779
2,344
—
, _
30,435
Philippines
1,701
1,427
—
274
Portuguese India (1960)
5,095
10
—
_ .
5,085
Ryukyu Islands
2,744
2,059
2,059
685
Singapore
2,080
673
187
486
1,407
Thailand (1961)
4,966
4,443
—
— .
523
Turkey
1,962
1,033
1,033
..-
929
Vietnam, South
40,600
4,400
4,400
—
36,200
Total
930,251
(240,164)
(9,503)
(960)
(689,861)
TABLK 6
Mechanization of fishing vessels in Europe
Total
Powered
Non- Powered
sub-total inboard outboard
Belgium
398
398 —
—
Denmark
9,398
3,872 — —
5,526
Faeroe Islands
253
253 — —
^._
France (1960)
15,238
. _
—
Germany
3,060
2,025 — —
1,035
Greece (1959)
15,185
5,019 — —
10,166
Iceland
2,311
_ — .
—
Ireland (1960)
2,203
704 — —
1,499
Italy
45,567
14,974 _ __
30,593
Malta and Gozo
402
—
—
Netherlands
2,807
1,985 — —
822
Norway
39,746
39,682 — —
64
Poland
1,597
1,285 —
312
Portugal
Spain (1960)
18,658
48,053
3,322 — —
12,910 -- —
15,336
35,143
Sweden (1960)
10,603
2,874 —
7,729
United Kingdom
8,098
7,814 — —
284
Yugoslavia
5,328
1,755 — —
3,573
Total
228,905
(98,872) (0) (0)
(112,082)
Australia
New Zealand
Total
Total
9,865
1,570
11,435
TABLE 7
Mechanization of fishing vessels in Oceania
Powered
sub-total inboard
(0)
[329]
(0)
outboard
(0)
Non-Powered
(0)
propeller, introducing vibrations, with consequent
deterioration of the aft bearing, (d) Galvanic action in
copper-sheathed boats can also pose problems, (e)
Fishing boats in most tropical countries have to seek
shelter in river mouths and creeks where the water is so
shallow that in rough seas the boats are dashed hard
against the bottom when passing through breakers or
over sand bars outside the entrances. This introduces
strains which can cause shaft non-alignment.
If something appears amiss, especially with the stern
gear, it can cause more trouble than most other compo-
nents of the marine diesel unit, necessitating beaching for
repair. In the operational areas, beaching arrangements
are limited, and repairs a lengthy process. Beaching can
result in damaged copper-sheathing and loosening of the
bearing and stern tube, makes waterproofing difficult,
and causes a serious loss in fishing time.
There are other problems which make the installation
of inboard engines difficult; for example, in existing local
boats it is often difficult to find a suitable position for
the shaft through the hull, or sufficient space for the
propeller, and to install proper engine beds and an
effective rudder.
OUTBOARD INSTALLATION
As an answer to all these problems, the easily installed
outboard engine was introduced. The outboard engine,
originally developed for pleasure craft with little regard
to economy, has been a tremendous success and has been
produced in millions. It is simple, easy to handle, safe,
light and cheap. Heavy-duty engines have been developed
and tried out in the fishing industry. Outboard motoriza-
tion of some small indigenous fishing boats was success-
ful when introduced a few years ago, but it was found
that the success depended a great deal on efficient engine
servicing. Poorly organized servicing, sometimes during
the early stages of motorization, can adversely affect
results. Jamaica, Trinidad, Malaysia, Uganda and
Ceylon are among the countries where outboard motor-
ization has caught on successfully. However, the two-
stroke petrol engine used in outboards today is the most
uneconomical to operate of all piston engines in use,
because of the high price of fuel due to heavy taxation,
and a fairly high specific fuel and lubricating oil con-
sumption.
Using cheaper fuel for outboard engines has long been
considered, and paraffin as a fuel has been used by some
Japanese manufacturers. Diesel engines as an alternative
were tried out by others, but with insufficient success to
encourage introduction to the market. The diesel design,
with its high pressures, makes the powerhead heavier
and more expensive, thus eliminating two of the main
characteristics attributed to the petrol outboard engine —
lightness and low price. It must be admitted that there
is a maximum boat size in which an outboard engine can
be run economically, and such a size can be found by
making a comparative analysis for a particular boat
equipped first with an inboard and then with an out-
board engine. This limit may be indicated by the size of
propellers available for outboard engines, although this
situation might change in the future. Such a decision
can be made more precisely between an outboard engine
and a petrol or kerosene inboard engine installation.
When, for example, 10 hp or less is required, it would be
cheaper and more advantageous to install a small petrol
or kerosene inboard engine rather than the heavier and
costlier diesel.
A COMPARISON OF OUTBOARD AND INBOARD
INSTALLATION
The outboard engine has so many excellent characteristics
which are superior to the inboard engine that its wider
use is inevitable if the right types are available on the
market. These advantages are:
• The boat will be considerably lighter, and can
therefore carry more fish and gear
• There is more space for the fishing operations
• The boat construction is simplified without the
engine bed, shaft log and rudder installation
• Lower installation costs
• The cost of the engine is only a fraction of the cost
of a diesel engine
• As the combination of engine and stern gear is
"factory made", there is less possibility of stern
gear troubles
• The boat does not have to be beached when repair
work is needed on the engine, stern gear or rudder
• The fishing time lest for repairs, as in the case of
inboard engines, can be reduced to almost
nothing by replacing the outboard by another in a
matter of minutes
• If the engine is well insulated from copper-
sheathing, the chances of galvanic action may be
reduced, although further study is needed to
substantiate this
• The propeller acts as a rudder, which affords the
boat better manoeuvrability when going through
surf. With an inboard engine, the rudder is
practically useless in surf when the waterflow is
of the same direction and speed as that of the
boat
• With outboard installation the possibilities of the
craft sinking are greatly reduced because of the
reduced weight of the hull and engine. The engine
could also be jettisoned in an emergency. This
eliminates the need of having the boat decked from
a safety point of view
• The water flow to the propeller is more even than
with inboard installation
On the other hand, the disadvantages of outboard
mechanization in comparison with inboard, are as
follows:
• Several types of outboard engines are run with a
high compression ratio, and therefore require a
high-octane fuel
• Price of fuel is sometimes exorbitant because of
government tax. Several governments have,
however, reduced this tax for the fishing industry
• The specific fuel consumption is twice as high
• The life of the engine is shorter
• The propeller selection is limited
• A power take-off is not yet available
[330]
TABLE 8
Comparative data for different engine installations for 27.5 ft (8.4 m) fishing boats
Power
Diesel inboard
Twin outboard*
Single outboard
22 hp
2 x 14 fy>
14 hp
Actual fishing days per annum
200
220
220
Additional fishing days if boat is not idle for engine repairs
20
Hours per day to and from fishing grounds (28 miles)
4
4
42
Speed knots
7
7
5.8
Fuel consumption, litre/hour
5.8
16
8
Price of fuel, incl. lubrication oil, per litre, pence (cents)
5.15(6)
14.6(17)
14,6 (17)
Depreciation (years)
6
3
2.5
Maintenance costs (per cent of engine value)
15
15
15
Weight saving available for cargo Ib (kg)
880-1,100
1.100-1,320
(400-500)
(500-600)
Increased net carrying capacity from 50 nets to ...
65
70
TABLE 9
Initial cost of boat ready for fishing
Hull
Engine beds/wells
Rudder
Installation of engine
Equipment
Engine (including freight, handling, excluding import duty)
Total cost of boat
Driftnets at £8.9 ($25) each 50-65-70, plus 20-20-25 spares respectively
Total cost of boat equipped for fishing:
Diesel inboard
22 hp
£ (!)
615 (1,720)
36 (100)
28 (80)
71 (200)
71 (200)
535 (1,500)
Twin outboard* Single outboard
2>\4hp \4hp
£ (!) £ (!)
615 (1,720) 615 (1,720)
18 (50) 12 (30)
71 (200) 71 (200)
356 (1,000) 178 (500)
1,356 (3,800)
625 (1,750)
1,060 (2,970) 876 (2,450)
758 (2,125) 848 (2,375)
1,981 (5,550)
1,818 (5,095) 1,724 (4,825)
The approximate prices of boats and engines are based on costs in Ceylon in 1963
TABLE 10
Running cost (annual)
Annual depreciation of boat over 10 years
(cost of boat minus cost of engine)
Annual depreciation of engines:
diesel over 6 years
twin outboards over 3 years
single outboard over 2j years
Annual depreciation of nets over 2 years
Interest of capital invested 6 per cent
Maintenance of boat, 10 per cent value
Maintenance of engines, 15 per cent value
Maintenance of nets, 20 per cent value
Cost of fuel and greasing:
diesel, 4,640 1 at 0.06
twin, 14,080 1 at 0.17
single, 8,360 1 at 0.17
Salaries for 5 fishermen at:
360 for diesel
360 for twin
"400 for single
Diesel inboard
22 hp
£ (!)
82 (230)
89 (250)
313
119
82
80
125
99
(875)
(333)
(230)
(225)
(350)
(278)
643 (1,800)
1,632 (4,571)
Twin outboards
2x\4hp
£ (I)
70 (197)
119
(333)
855 (239)
643 (1,800)
2,451 (6,863)
Single outboard
14 hp
£ (I)
70 (195)
379
109
70
54
152
(1,062)
(305)
(197)
(150)
(425)
71
423
103
70
27
170
(200)
(1,187)
(289)
(195)
(75)
(475)
507 (1,420)
714 (2,000)
2,155 (6,036)
* Longer fishing time
The figures for the breakdown of fishing costs and salaries are based on the average results of a few fishing trips
[331]
TABLE 11
Annual income
Diesel fully-equipped boat 200 fishing days with 50 nets
Twin outboards, 220 fishing days with 65 nets
Single outboard, 220 fishing days with 70 nets
Running cost
Profit
Diesel inboard
22 hp
£ (!)
2,285 (6,400)
654 (1,829)
Twin outboards Single outboard
2xl4hp 14hp
£ (!) £ (!)
1,631
(4,571)
3,270
2,451
(9,152)
~~(6,863)
3,520
2,155
(9,856)
(6,036)
819 (2,289) 1,365 (3,820)
The approximate average income for such a fishing boat when driftnetting is based on figures collected in Ceylon in 1962, with regard to
the size and price of the catch. The catch per net is calculated at 8 Ib/day (3.6 kg), and the price per Ib (0.5 kg) of fish is 7 pence (8 cents),
which is possibly an underestimate.
ECONOMIC CALCULATIONS
To establish the maximum economical boat size for
outboard engine installation, and to compare the
economy of the outboard with the inboard, it was
planned to carry out tests in Ceylon with outboard
engines on a 2?i-ft (8.4-m) fishing boat originally
designed for inboard engine. Although this has not been
done, it is of interest to study the preliminary calculations
based on data collected for the tests.
The main dimensions are :
Length 27 ft 6 in (8.4 m)
Beam 8 ft 4 in (2.54 m)
Engine, inboard diesel, 22 to 25 hp
Speed 7 knots
The comparative calculation in tables 8 to 11 shows
this boat installed with (a) an inboard diesel, (b) twin
outboard engines, and (c) a single outboard engine built
into a well. The proposed fishing method is with driftnets
(30 x 3 fm hung, mesh size 4 to 6 in), under conditions
usually prevalent in Ceylon.
These comparative tables show that an outboard
engine can compete favourably with the small diesel in
boats up to 30 ft (9 m) long, mainly because of the lower
weight and less space required in the boat. The lower
initial investment for the outboard would be most
advantageous in many countries with low financial
resources.
RECOMMENDATIONS
There is no outboard perfectly suited to the fishing
industry. The main reason for this is the question of
economy. A fast running two-stroke petrol engine has
its economical criterion in the speed and velocity of the
gas in the engine. Possibly there are ways of making the
power head more economical, which probably would
result in an increase of vibration and noise. A question is
whether or not a four-stroke engine would be more
economical, without upsetting the balance of low price
and small weight.
The lower part of the engine, which transfers power
into efficiency (thrust) must be considered of the utmost
importance when designing an engine suitable for slow
running fishing boats. The diameter of the propeller has
to be big, so that the thrust distributed on the disc area
of the propeller is not too high. In order to acquire a
better propeller efficiency, the propeller rpm should be
lower than is usual on present outboard engines.
The efficiency of a propeller is determined by many
factors, including the relation between shaft horse power,
speed of advance and the propeller revolutions. In de-
signing the lower part of the outboard engine, calcula-
tions should take these factors into account and theo-
retical speculations should be supported by practical
tests.
The following characteristics, for a displacement type
fishing boat, are required for the outboard engine:
• Output of 10 to 15hp
• Two cylinders should be so arranged that the
firing would be alternate. This would make
hand-starting easier when the engine has to be
started in the open sea and it is difficult to keep the
boat still against the waves
• Recoil start rather than an ordinary straight pull
rope start, which is too slow. An electric starter
would only increase the breakdown risk
• The propeller should have a large diameter and
low revolutions
• The propeller diameter should be suitable for
heavy and badly-shaped boats but, on the other
hand, the pitch should not be too large, to prevent
the engine being overloaded when the boat is
moving against heavy waves or is loaded
• The propeller should be so designed that it can be
changed with the minimum use of tools, in order
that propellers of different pitch can be easily
interchanged when going to fishing grounds and
returning. It would be an advantage if the propeller
and fastening components could be buoyant. (The
question of a controllable pitch propeller should be
considered by the manufacturers.)
• The engine must be built to withstand impact wnen
being unshipped and carried to a storage place,
and it must be so designed that the cooling water
cannot enter the cylinders if the gearbox is lifted
too high
• A pipe should be fixed around the circumference
of the engine, which would serve as a grip for
carrying and handling and also as protection
when the engine is laid on the beach
[332;
• A petrol trap should be provided to prevent petrol
flowing into the crankcase when the engine is
being carried. If this is not possible, the arrange-
ment should be to hold the engine with the car-
burettor face down. Otherwise starting the engine
will be difficult
• The engine should be so encased and the cover
lockable so that thefts of small parts are difficult
• All hot parts of the engine should be encased to
prevent burns being sustained when lifting the
engine from the boat
• The tiller should be long enough to permit a man
on a catamaran (log-raft) or in a canoe to stand
and steer the boat
• Fuel supply should be from a large tank
• The ignition should be by magneto
• The flywheel should be protected
% Where there is no space to keep tools dry, a tool
box should be supplied that can be attached to the
engine or screwed somewhere in the boat
• For certain fisheries, it would be an advantage to
have a small generator so that fishermen can
employ lights during the night. It could be
arranged in combination with the magneto
• Engines must be waterproof, perhaps by encasing
the engine in a waterproof tarpaulin and fixing a
breathing pipe on top of the engine cover. This
should be used only in bad weather conditions,
or if the engine is partly protected
• Fuel consumption must be low, because petrol is
often very expensive due to heavy taxation.
Fuel consumption can be reduced on a two-stroke
engine by using a rotary valve, which should not
increase the price of the motor when mass
produced. The lower unit can have a higher
efficiency through good propeller design and so
reduce consumption
• The engine should use only low-octane petrol
• The ratio between engine and propeller revolutions
may be so high that a second gear is required to
avoid making the propeller gearbox too big. In this
case, a power take-off from a gearbox connected
to the power head could easily be provided and
would be of great advantage, for three reasons:
(a) to drive a generator for fishing with lights
(b) to drive a hydraulic power unit to serve a
power block, net roller, line hauler, etc.
(c) to drive a water pump to circulate water in
the fish well, spray water when live-bait
fishing, for bilge pumping, cleaning, etc.
• All engines should be supplied with a small bilge
pump. Most fishing boats leak, and it is useful to
have the pump also for cleaning purposes
• Great care must be taken to indicate when an
engine may need servicing, because many owners
might not be able to read, write, or make telephone
calls. The organizing of engine servicing is a
necessity for every fishing engine, as the fisher-
men usually have no experience in repair work
• It might be advantageous to manufacture certain
parts of the engine in "sealed units", which could
only be repaired by skilled mechanics. Many
instances of engine damage have occurred when
fishermen, inexperienced in maintenance, have
attempted repairs
• A bracket could be supplied with the engine, for
clamping on to the side of the boat
• The exhaust, if taken out over the water surface,
should have a flexible exhaust pipe with a "quick
snap-on" connection. When engines arc installed
in wells on larger boats, the exhaust pipe must be
run clear of the well
• An engine installed in a well does not necessarily
(depending on boat types), need an arrangement
for tilting. Such arrangements are more compli-
cated to build, and result in a much larger bottom
opening than is desirable. The opening need only
be large enough to provide sufficient steering
clearance and avoid propeller cavitation.
CONCLUSION
The market for outboard engines for small fishing boats
would seem large enough to encourage manufacturers to
design units solely for this industry. To date, however, the
heavy-duty outboard engine is basically still a converted
pleasure boat engine.
The installation of an outboard engine in existing
fishing boat hulls is not the entire answer. Fishing
techniques have to be adapted to mechanized boats,
marketing has to be considered, and above all efficient
engine servicing has to be organized, in the initial stage
with government assistance, until there are sufficient
engines in the area to make private enterprise servicing
an economic proposition.
In many areas, such as the large man-made reservoirs
of Lake Kariba, Lake Kaptai and the big dams in India,
the boats used are totally unsuitable for mechanization.
Boats have been developed along coastlines, of East
Africa for example, from which no fishing other than
handlining can be performed. In places like Lake
Victoria, Lake Chiloa and Lake Nyasa in Africa, the
inshore areas are over-fished, but no fishing can take
place further out because the boats are unsuitable for
open water. Here, boatbuilding has to be developed.
When designing a small boat for such remote areas, the
limited local facilities, the local timbers, the impossibility
of obtaining simple items like nails, screws, bolts,
not to mention woodworking tools, and, above all, the
total lack of craftsmen, have to be borne in mind.
The development of small-boat fishing and the problem
of motorization of existing craft has several very interest-
ing aspects, and still demands a great deal of initiative
from the manufacturer of small engines.
[333]
The Location and Shape of
Engine Wells in Dug-out Canoes
by Thomas C. Gillmer and 0yvind Gulbrandsen
Emplacement et forme des putts ft moteur pour pirogues monoxyles
Des points de vue 6conomique et technique, la memorisation de
certains types de pet its bateaux dc pgche au moyen de hors-bords
installs dans un "puits" int6rieur a la coque pr&sente un grand
interet. Les auteurs examinent les avantages et les inconv&nicnts de
cette technique dans le cas de pirogues d'Afrique occidental se
prttant a ce type d'installation. L'6tudc repose sur des essais tant
sur modeles rgduits qu'en vraie grandeur sur des coques de forme
analogue* Les rdsultats permettent de formuler les conclusions
suivantes: (1) Le puits permet d' installer le moteur de maniere plus
pratique et plus rationnelle que tout autre systeme; (2) L'emplace-
ment longitudinal du puits, sur le type de pirogue etudi6, n'exerce
pas une influence importante; (3) La forme et les dimensions de
F orifice du puits affectent de facon marquee les caracteiistiques de
vitesse et de puissance.
Situaci6n y forma de las barquillas de motores en canoas de troncos
Econ6mica y estructuralmente, tiene muchas ventajas la potencia-
ci6n dc ciertos tipos de pequenas embarcaciones de pesca instalando
barquillas de motores. Se examinan aqui las ventajas e incon-
venientes de tales barquillas en relaci6n con su empleo en tipos
adaptables de piraguas de Africa Occidental. Este examen sc basa
en pruebas de ambos modelos y en canoas de escala normal de
casco de forma similar. Los resultados de la prueba indican que: (1)
Las barquillas de los motores proporcionan un montaje del motor
mas pr£ctico y eficaz para esta adaptacion que otros sistemas; (2)
La situaci6n longitudinal de la barquilla no tiene gran importancia
en el tipo de embarcaci6n probado; (3) La forma y tamafio de la
abertura de la barquilla influye grandemente en las caraoteristicas
potencia-velocidad.
KICENTLY research has been carried out to decide
the best location of outboard motors other than
directly on the transom. In many cases side
brackets have been used but this generates a transverse
moment which must be counteracted by a steeringmoment.
This increases the overall drag and hence the power
requirement. Consequently, side bracket mounting, while
expedient and certainly more practical structurally, must
be considered a less efficient means of propulsion than
centreline mounting.
The structural limitations are of considerable import-
ance when considering the installation of a centreline
engine well. Flat-bottom skiffs are perhaps the most
adaptable (Beach, 1960). In the absence of the longi-
tudinal keel timber, a centreline well is structurally
sound.
Hull configuration also imposes both structural as well
as installation limitations. Round-bottom, and to a lesser
extent vee-bottom craft, because of their keels and deeper
sections, make well installation problematical. Notable
exceptions to this are craft of monocogue or homogeneous
hull structure, such as the indigenous dugout. Hull
materials such as moulded reinforced plastics or pressed
aluminium, particularly in the original design and build-
ing process, lend themselves to the introduction of motor
wells. These materials, however have only been found
advantageous in the more prosperous fishing communities.
The dug-out log canoes of West Africa are traditionally
propelled by paddles, often beached and launched
through surf; motor propulsion would be a most sig-
nificant improvement operationally, and ultimately
economically.
Their shape is also easily adapted to well construction,
being rather full in section which, while rounded, is rather
flat in the centreline vicinity. They have straight longi-
tudinal lines for the greater part of their length with rather
full ends and a hull thickness on the bottom of 5 to 6 in
(12 to 15 cm). This provides a solid base for securing the
well structure, simultaneously keeping it high and thus
not imposing high static water pressure.
It is significant to study the hydrodynamic phenomena
surrounding the introduction of the necessary orifice
through the hull shell of these structurally adapted craft
and particularly the effect on resistance. In Ghana, Sene-
gal and Dahomey this problem was resolved in testing
models of the prototype craft; the tests were begun and
continued (when time and facility permitted) in the towing
tank in the US Naval Academy, Annapolis. In 1964 two
typical somewhat similar Ghanaian canoes were acquired
by FAO for power and speed tests in Dakar, Senegal.
The resistance data from the model tests has been
given in its simplest form and is presented graphically on
the model scale primarily because of lack of information
of the full-scale conditions. These conditions are variable
and so lack true conformity to the lines drawing as to
make dependable Pc against speed representations of the
prototype hulls most inadvisable. In addition, because of
the variation of Reynold's number between the model
and the prototype, the dynamics of the water flow into
and around the wells introduces scaling factors which are
difficult to predict from model to full scale.
It should be pointed out that any inferences and inter-
pretations suggested must be comparative, indicating
primarily tendencies and probable effects.
[334]
DESCRIPTION OF MODELS AND APPARATUS
Model 1 is of a Senegalese pirogue or canoe of 31.2 ft
(9.5 m) length (model scale 1/6.35). The hull lines (fig 1)
were taken from a FAO drawing made from measure-
ments of a typical pirogue taken off at Soumbedioune in
October 1962. The basic hull of this, not including the
decorative stem and stern extensions or the wash or spray
shields, was 28.6 ft (8.7 m) length, 4.4 ft (1.34 m) beam
and the depth amidships of 1.58 ft (0.48 m). The hull has a
rather extreme longitudinal curvature of the bottom
(fig 2) and the sections are rather flat bottom "U" shape,
of flaring sides with an angle of about 30" from the
vertical.
Tn this model a motor well was positioned correspond-
ing to full-scale dimensions of 8.5 ft (2.6 m) aft of the
midsection and was of the proportions shown in fig 3,
31 Jxl3J in (80x35 cm), the same size as used in all the
tests. The forward end at the bottom of this well forms
the forward half of the opening through which the lower
unit of the outboard engine and propeller projects. In
fig 3 it is shown with perimeters that rake back at an
angle of 45° with the longitudinal axis of the hull. This
forward end of the well is fixed and is actually a portion
of the bottom of the hull. The after part of the well bottom
is an adjustable hatch, fitted with hinges at its after edge.
When closed, this hatch is nearly flush with the bottom
and allows a smaller opening to exist of the shape shown
(fig 3). The purpose of the hatch is to enable the engine
to be tilted for protection when beaching or approaching
FIG I HULL LINES, SENEGAL PIROGUE, USNA MODEL
FIG 2 SENEGAL PIROGUE , USNA MODEL I
— —- •" * " i
— -l_~"_~- — -=rr-..~. — • - - - t "
FIG 3 BASIC WELL CONSTRUCTION
FIG 4 HULL LINES . GHANA CANOE . USNA MODEL 2
[335]
Fig 5. Ghana canoe, VSNA Model 2
Fig 6. Water level gauge in Model 2
Fig 7. Ghana canoe rigged for towing
the bottom. The angular position of this hatch affects the
hydrodynamic characteristics of the hull, as will be des-
cribed.
Model 2 is of a Ghanaian canoe of 32.8 ft (10 m) length
(model scale 1/6.5). The hull lines (fig 4) were taken from
a FAO drawing reconstructed from measurements of a
typical Ghanaian canoe taken off at Seme, Dahomey, in
April 1963. The basic hull of this canoe, exclusive of stem
elongations, was 29.5 ft (9 m) length, 4,85 ft (1.48 m)
[336]
beam and a depth amidships of 2 ft (0.6 m). It does not
have as much bottom curvature longitudinally as the
Senegalese canoe and is of a round bilge section which, in
the bottom, is fairly flat amidships. The ends are quite
full and "apple cheeked" (fig 5). The motor well was in-
stalled in this model of the same dimensions as described,
in a first location 4.9 ft (1.5 m) aft of the midsection,
and later in a second location with the forward edge of the
well amidships. The wells were both fitted with the same
hinged hatch in the bottom. In the model wells a gauge
was installed that registered water level variations to 0.01
in (fig 6). The models were ballasted and trimmed to an
operating displacement of approximately equivalent to
1, 800 Ib (820 kg) full size.
They were finished with several coats of exterior grade
varnish and hand rubbed to a smooth, dull surface.
Turbulence stimulators were fitted since the tests were to
take place in the Reynold's number range in and below the
transition at flow region.
During the tests of model 2 a dye jet tube was fitted
ahead of the well opening for flow studies. High-speed
cinematograph cameras were used in connection with
these studies but the quality of the film precludes repro-
duction. Fig 7 shows the model of the Ghanaian canoe,
ballasted and attached to the carriage for towing.
MODEL TEST PROCEDURES
It was decided to use the standard-shaped motor well
(fig 3) in two locations and test a range of hatch
closure angles for various speeds to determine the speed
against resistance and speed against water level curves.
These tests were carried out, first with the Ghanaian
canoe, model 2, with various hatch closure angles from
0° to 90° at 30° intervals. The same procedure was followed
for the Senegalese canoe, model 1. The water level
tests were conducted after the resistance tests. Before the
motor well position was changed to another location and
the tests repeated, a dye tube was incorporated to stream
dye aft in line with the well for observation of the flow
characteristics in the vicinity of the well opening. This
was observed and photographed.
EXPERIMENTAL RESULTS AND DISCUSSION
Model tests
A naked hull test was made before cutting any motor
well in the model of the Ghanaian canoe, model 2. These
test results were compared with the results with the
well installed and the hinged hatch in the closed position
(fig 3). The results for these two conditions showed no
significant difference indicating that the aperture, formed
by the hatch and the shaped closure ends, produced so
little additional disturbance of the flow that it was not
measurable. The inference here is that this is a most
efficiently-shaped aperture, producing practically no
disturbance of water flow, and this was substantiated in
the visual dye-stream observations. Referring to the test
curves of resistance against speed-length ratio (fig 8) it
can be seen that there is a considerable difference in
resistance with the hinged closure hatch fully open and
closed. It was observed in the water level tests in the wells
that when the hatch plate is fully open (at 90°) there was
considerable turbulence in the well with water entry into
the hull and extreme fluctuations in water level at the
upper speeds. It became necessary under these conditions
to seal the top of the well temporarily. The additional
drag produced by the fully-opened well might be com-
pared to an appendage drag with a proportional flat plate
or projected area similar to the after face of the well.
The flow conditions are, of course, not similar but the
effect and nature of the flow may be comparable.
Fig 8. Speetll Resistance, Model 2, Well /
The tests with the closure plate at angles of 30 and 60°
respectively show resistance values of similar but not
identical quantities and indicate that resistance increases
with hatch angle at some significant values. At medium
speeds there is a junction of data (approximately K/vZ=
1.0) where the angle of the closure plate between 30° and
60° makes very little difference. At upper speed length
ratios (V/VL=].5) there is no apparent change of resis-
tance from the closed position up to 30\
From the direction that the 60" plate angle curve
appears to be taking at these higher speeds, it would be
possible to say that an impact resistance against the face of
the plate is building up. This is borne out further by the
tests of water level where observations show turbulence
developing in the well at these speeds with the plate at
60°. While no tests were conducted with hinged plate at
angles between 60 and 90', it would be reasonable to
predict that the well turbulence would develop at decreas-
ingly lower speeds with increase in plate angle. This
would indicate increasing resistance until the limit with
the fully-open hatch was reached.
With the well relocated in the second position, near
but aft of the midsection (fig 4) the tests as in the initial
well location were repeated. The indications shown for
this condition (fig 9) are in general slightly more favour-
able. The resistance curves for the various plate angles
are of similar nature when compared with the results of
the same series with the first well position. They show
small quantitative decreases in resistance at most speeds
in the operating range. In most cases these incremental
values, particularly at small plate angles, are so small as
not to be of general significance.
Model 1, the Senegalese pirogue, was tested with the
well as shown in fig 1. It is interesting that the basic
[337]
Fig 9. Speed/ Resistance, Model 2, Well 2
resistance curve with no well installed shows a more
steeply rising curve for this flat-sectioned hull from a
lower resistance value (fig 10) than model 2. In the speed
range of K/VZ=1.0 a specific resistance (R/A) of .012 is
given while in model 2 (Ghanaian canoe) for the same
speed, JR/J—.017 is recorded. However, the excessive
longitudinal curvature of this hull rapidly increases the
resistance at the more critical hull speed values near 1.3
speed-length ratio. An exceedingly deep hull-generated
wave was quite apparent at this speed.
The open well test of model 1 shows less increase in
resistance than model 2. There is also a marked closing of
the curves as the speed increases. This is quite obviously
due to the previously observed build-up in an excess-
ive amount of wave resistance. At speed-length ratios of
1.2 to 1.25 the wave contour along the hull conforms
closely to the contour of the bottom of the hull, indicating
a lower pressure differential at amidships. This would
produce a reduction in the drag effect of the open well,
reducing it to lesser proportions in the high-speed range.
As the curves indicate, at these higher speeds there is
little or no change in resistance between fully-open and
closed well. It must be pointed out that this phenomenon
should not be generalized to include other types of hull
with more conventional bottom shape or less longitudinal
slope in the after bottom.
During the preliminary tests of both models it was
observed that they had very poor directional stability
characteristics. Model 1 actually became self-broaching
when at speeds greater than K/VZ—1.00. This condition
was noted while checking simple behaviour characteris-
tics where the models were towed from their centre of
floatation. Using a special towing bracket which allowed
the three directions of angular freedom, this instability
Fig JO. Speed/ Resistance, Model 1
was most apparent at speed-length ratios over 1.00 and
was in all cases noted after the steady state was reached
and not during acceleration or deceleration. Model 1 was
repeatedly swamped under these conditions. Similar
steering behaviour has been observed subsequently in the
full-scale tests.
The tests of static water levels in the model's engine
wells were made for the total range of speeds (fig 1 1).
These pressure head levels, together with the indicated
turbulence, have been noted and also their relation to the
resistance results. It should be pointed out that the water
level differentials were extremely small and of generally
inconclusive significance except to relate the hull-genera-
ted wave level. In the case of the fixed aperture at closed
plate 0° angle the indicated well level followed the external
Model spMd (knot*)
Fig JL Water level/ Speed, for various hatch openings, Model 2
[338]
^^^^ *»•»« •»•• »•• ••••» >|. *«•<*<• . - -. Otoict in ti.p..
Pig 12. Ghana canoe, outboard-motor installation* position I
water level (hull wave) very closely. Such a condition
suggests those to be found by installation of a phot static
tube.
Canoe tests (full-scale)
The full-scale tests were carried out in the port of Dakar
with two Ghanaian canoes of the same main dimensions:
Loa 20 ft (8 m)
Maximum beam 4 ft (1.25 m)
Dry weight 772 Ib (350 kg)
There were however differences in the longitudinal
Fig 13. Well* cut through canoe A (Note thickness of hull)
shape of the canoes, canoe A having more longitudinal
curvature on the bottom than canoe B.
The first thing to be decided was the dimensions of the
opening to be cut in the bottom of the canoes. After
discussions with Mr. A. Collart, FAO Fisheries Expert
in Dahomey, who is well experienced with canoes, it was
agreed that lifting the motor vertically before grounding,
as done in Senegal, was an unsatisfactory solution. The
opening should be long enough to permit tilting the motor.
The largest motor considered for the canoe was 18 hp and
the dimensions of the opening were based on this motor
size with a propeller diameter of approximately 9j in
(24 cm). The width of the opening was 132 in (35 cm) to
give reasonable steering angles. Only longshaft motors
were considered practical and gave a dimension of 20J in
(52 cm) from the top of the transverse bulkhead to the
underside of the bottom. There are on the market motors
with larger propeller-diameters for higher efficiency, and
for these motors the length of the opening has to be in-
creased. A propeller of 13 in (33cm) diameter would
require an opening of 35.5 in (90 cm) length.
To reduce the resistance of the well, it was evident that
the opening had to be partially closed in some way.
Several possibilities were considered, but the one shown
in fig 12 and 14 was selected because of its efficiency and
simplicity. This consists of a hatch with a hinge, flush
with the bottom at the aft end. This hinge can be very
simple, just a steel rod fastened on each side to the top of
the hatch and turning in holes bored in the side of the
canoe. Stops must be placed on the sides of the opening
forward to prevent the hatch from dropping through.
Under speed, the water pressure pushes the hatch up. A
device as indicated in fig 12 will prevent this but still
enable the hatch to be quickly released when approach-
ing the beach. If by accident the motor should hit the
bottom while crossing the bar it can tilt freely and thus
major damage will be avoided.
The first tests were of two different well positions. In
position 1 the forward bulkhead of the well was placed
about one-third of the overall length from the aft end in
canoe A. Fig 12 shows this position and fig 14 shows
position 2 further aft, which was tried on canoe B. The
[339;
Fig J4. Ghana canoe, outboard-motor installation, position 2
drawings also indicate the construction methods. In
canoe A a box was built around the opening; 2Jx2J in
(6x6 cm) pieces were through-bolted to the bottom of
the canoe and the sides of the well nailed to these. Canvas
strips soaked in thick paint were placed in the joints to
render them watertight. The aft well position in canoe B
permits simplification by placing just one transverse bulk-
head forward of the opening for motor attachment.
Tests results
The motor used during all the tests was developing a
nominal 14 hp at 4,800 rpm. Initially both canoes were
tested with the motor fitted on the side as normally used,
then the wells were installed as shown in fig 15. All the
trials were in the Port of Dakar under favourable wind
and sea conditions.
Speed was measured by stop-watch between two
fixed points 4,690 ft (1,430 m) apart, at least once
in each direction at each throttle setting.
Fig 15. Well installations. Canoe A with installation
position 1 to the right, and canoe B with installation position
2 to the left
Fig 16. Resistance dynamometer
[340]
Motor rpm was determined by a vibration tacho-
meter and fuel consumption by an electronic
apparatus giving an accuracy of 0.1 gal/hr.
The thrust measurements were made with the
apparatus shown in fig 16, It consists essentially of
a hydraulic cylinder with a piston placed between
the lower unit of the engine and the transom. The
propeller thrust is thus directly tramsmitted through
the piston to the fluid in the cylinder which in turn
registers the resulting pressure through a trans-
mission line to a calibrated pressure gauge.
T=AxPxh.c
*P
where: T= thrust (kg)
A :-- piston area (cm2)
P --^pressure at gauge (kg/cm2)
Ac=distance of piston axis from engine pivot (m)
/;p=distance of propeller axis from engine
pivot (m)
This device can be applied to any hull powered with an
outboard motor and offers easy measurement. The test
results for the two canoes are given in table 1.
It will be noted that by placing the motor in a well, the
speed increased no less than 1.1 knots for canoe A and l .2
knots for canoe B. An additional advantage is more
adequate protection for the motor and less spray being
thrown into the boat. The tests show beyond doubt that
the more complicated well installation gives higher
performance.
10 knots
'1.4
'1.6
'1.8
~T20 "22 '2.4 VA/C
-.4 .5 -6 .7
Fig 77. Speed I thrust curve, Ghana canoe , /4
1670 Ib (850 kg)
1430 Ib (650kg)
5000
1.4
1.6
1.8
2.0
.4 .5 -6 7
rig Jti. Fuel consumption, Ghana canoe A
The difference in maximum speeds of canoes A and B
can be attributed to difference in shape; the flatter bot-
tomed canoe B has a much better performance at higher
speed-length ratios. A direct comparison between the two
different well positions, therefore, was not possible.
Extensive trials were made with canoe A in order to
determine fuel consumption, revolutions and thrust at
different speeds. Fig 18 gives the fuel consumption
and the rpm of the motor at two different loadings. The
thrust curve is shown in fig 17. By adding 440 Ib (200 kg)
the top speed dropped 1.1 knots and the fuel consumption
per nautical mile, increased 1 5 per cent.
In order to get a comparison between the two differ-
ent well positions, 1 and 2, it was decided to try them on
the same canoe. Canoe A was chosen for these tests
because its form is most representative of the Ghanaian
canoe (fig 12 and 13). It was also decided to get a com-
parison between the well and the transom installation.
During the tests of the latter (the end of the canoe was cut
off and the motor fixed on a transom), the well-openings
were plugged with polystyrene blocks shaped to the form
of the bottom of the canoe. Table 2 gives an impression
of the four different motor installations tested, as shown
in fig 19. These tests were performed after the motor had
been used for some rough beach-landing trials and there-
fore it was not in the same condition as during the first
tests. The top speed of the canoe with the motor in the
well, position 1, dropped from 9.3 knots to 7.8 knots.
[341]
TABLE 1 : The speed for maximum throttle
Motor side mounted
Motor in well
Type
Canoe
rpm
Speed
in knots
Well
type
rpm
Speed
in knots
A
4,650
8.2
1
4,850
9.3
B
4,700
8.5
2
5,000
9.7
TABLE 2: General impression of the installation
Speed in Cost of Loss of Steerinlf Protec-
knots installation space *ieenn* tionof
motor
7.0 10 10 6 4
Side-mounted
7.0
10
10
6
4
motor
Motor in well,
Position 1
7.9
3
7
8
10
Motor in well,
Position 11
7.8
6
8
9
9
Motor on transom
8.1
7
9
10
5
This is, however, of rather small importance since we are
more interested in comparing the different installations
than the absolute top-speed.
The speed for maximum throttle is shown in table 1 .
It will be noted that, with the exception of the side-
mounted motor, the difference in speed is not great. The
best in this group is the transom installation, with a speed
SIDEMOUNTED MOTOR
of 8.1 knots; the worst, the motor in a well, position 2,
with a speed of 7.8 knots.
One significant observation for both canoes with the
motor in the well or on the transom was their bad course-
keeping stability. Especially with the motor in the forward
well position, the canoe was tender on the helm. A reason-
able explanation for this is the lack of lateral-plane aft
caused by the large curvature of the bottom. The steering
problem can be solved by fixing a roughly streamlined
plank aft on the side of the canoe, as indicated in fig 12.
When approaching the beach, it can be pivoted. It is also
possible to add a keel on the canoe, but this should be
placed so far aft so as not to interfere with the handling
on the beach.
Under speed the propeller creates a suction which
reduces the amount of water in the well. In the well,
position 1 , the water depth at rest was 6.25 in (1 6 cm), and
this was reduced to 2.4 in (6 cm) at speed. In the well,
position 2, there was little water both at rest and at speed.
The wells were also tried without a hatch to cover the
opening and this introduced much turbulent water into
the well. The drop in speed, without hatch, was 0.6 knots
for position 1 and 0.4 knots for position 2.
The choice of a certain type of installation must be
based on many factors beside the speed: cost of instal-
lation, loss of space, steering and protection of the motor
from spray. These qualities are not measurable, but table
2 is based on the general impression of the different
installations during the tests.
Beach landing must also be considered. On landing,
the catch is first unloaded, but the bigger canoes are still
too heavy to be dragged up the beach. Five to ten men
hold each end of the canoe and start turning it, using the
lever principle. The men are alternately lifting and pres-
sing down the ends, thereby changing the centre of rota-
tion, as shown in fig 20. Tn this way, the canoe is "walked"
V
'- T
MOTOR IN WELL , I
Pomt of rotqtiQn.
MOTOR IN WELL , Z
•r
MOTOR ON TRANSOM
Fig 19. Different ways of motor installation
\ppint of notation
Fig 20. Method of moving a canoe on the beach
up the beach. Cutting off one end of the canoe to install
a motor on a transom will, therefore, make the handling
on the beach more difficult.
Crossing the surf is, from an operational point of view,
the most critical period. To date, in Ghana, the motor
has always been placed on the side of the canoe which
makes it very exposed to breaking waves. The fishermen
[342]
therefore take off the motor and put it inside the canoe
before paddling through the surf. In Senegal the motor is
always installed in a well and consequently has much
better protection. The motor is used also when crossing
the breakers and is lifted up just before grounding. The
steering is not done however with the motor, but by the
master fisherman sitting far aft with a paddle. The reason
for this seems to be tradition. The motor has taken over
the work of the paddlers, but the master still prefers his
steering position aft. This works well in open sea but,
no doubt, steering with the motor gives a more positive
control when going through the breakers.
The full-scale values show thrust values through speed-
length ratio values of 1.2 to 2.4. Relating model and full-
scale data is an interesting procedure because reliable
full-scale test speed-power data is rarely available. The
comparative speed-power values were reduced from full
Fig 21. Ship model correlation
scale to model dimensions in this case. Fig 21 attempts to
show an extension of the model test values to points
reduced from the full-scale tests on the Ghanaian canoe 1
with engine in well position 1 at full load, 1,880 Ib or 850 kg
(3 men+200 kg) which most closely corresponds to the
model displacement.
CONCLUSIONS AND RECOMMENDATIONS
The speed-resistance curves substantiate the results of
power requirements for the various well openings.
Summary of the model test results:
• In all well positions, the best condition was with
least aperture opening
• As the angle of the hinged plate was increased, the
measured resistance increased in both models
• Model 1 different plate angles at higher speeds
show no appreciable change in resistance
• The change in well position in the Ghanaian canoe
to midships results in a very small improvement
in resistance characteristics
The model test results also verified the poor directional
qualities of the canoes. In connection with the small im-
provement in powering the amidship well location with a
conventional outboard motor, a rudder would be required
because of a lack of a turning couple. The additional
drag of a rudder would appoximately offset the powering
advantage, resulting in a dubious net improvement.
As suggested from full-scale trials the addition of a fin
or skeg would be most helpful. Such an addition for opera-
tion from the beach in surf would at least offer an addi-
tional safety factor while detracting a small amount from
the powering characteristics. To summarize specifically
the differences between the two models tested :
Model 1 (Senegal pirogue)
• Well aperture results in comparatively small in-
creased resistance with the maximum occurring
at V/VL=l.Q to 1.1 and then diminishing to zero
• At higher speeds the wave-making resistance of
this hull increased excessively with the wave con-
tour producing a diminished to negligible effect of
the well opening
Model 2 (Ghanaian canoe)
• The opened well shows a relatively large increased
resistance throughout the entire speed range which
is manifested when the hinged plate is open at
angles greater than 60°
• With the hinged plate at angles of less than 60°
there is comparatively small increase in resistance
and this decreases with plate angle. The small
aperture existing when the hinged plate is closed
results in no measurable increase in resistance over
that produced when the hull has no aperture at all
To correlate the model tests to the full-scale tests at
this stage is rather difficult, but some correlation is ap-
parent.
Primarily, the evidence of poor directional capabilities
was discovered. Secondly, in the limited ranges of speed
where model and actual canoe's data overlapped there is
good evidence of similar results. Finally, in the full-scale
Ghanaian canoe, there was a speed reduction of 10 per
cent between fully-opened well and the "closed hatch"
(0° plate angle) condition. This corresponds to the results
shown in the model tests. It must be remembered that:
• The full-scale canoes have an undetermined rough-
ness coefficient that could be determined only with
more detailed data over the lower and medium
speed ranges
• The "scaling-up" of model resistance values, taken
at higher speeds (F/VZ=1.5), is frequently un-
reliable
• The model and actual canoes were not of identical
geometric form but only "similar'*
• The well locations of the model and actual canoe
corresponded in only one instance
• The effect of the propeller operating below the well
aperture changes the flow character of the water in
the vicinity and increases turbulence aft of the well.
This in turn will produce differing resistance
coefficients
[343]
However, it is not extremely important that exact
correlation between model and prototype be searched for,
but rather trends, performance characteristics of a similar
nature and data that agree generally. In these tests it is
more significant and important that one series of tests is a
displaced extension of the other. In this respect the model
tests, together with the full-scale canoe tests, provide a
thorough and extensive investigation.
The model tests generally substantiated the full-scale
tests, showing that variation in longitudinal well location
does not have a marked effect on the powering charac-
teristics. It might additionally be suggested that further
study of such longitudinal locations could result in an
optimization of steering capabilities.
Generally, it may be concluded from both full-scale
tests and model tests that motor well installations pro-
duce some deterioration in the powered performance and
speed characteristics, but these effects are not significantly
large. In any case, when considering other types of tran-
sient motor installation together with various operational
factors (see table 2), the motor well installation is superior
to any other, as applied to these West African canoes.
The final choice of motor well is, of course, dependent
upon the nature of the practical working conditions.
There seems to be very little difference shown in tests
between the full-scale position 1 andposition2 or the model
tests with different longitudinal locations. The more
significant factor is the use of the hinged hatch plate
with the well installation, and the importance of keeping
this hatch closed, or nearly so, in operation.
Jamaican dugout canoe with transom stern to accommodate an outboard. Compare with Thomas's paper p. 432 '.
[344]
Engine Types and Machinery Installations
by Curt Borgenstam
Moteurs et appareiis auxiliaires
La gamme de groupes propulsifs dont disposent aujourd'hui les
pecheurs peut aisement desorienler par sa varietd, depuis le classiquc
moteur marin jusqu'au moteur d'automobile Iggcr et a grandc
vitesse.
L'auteur commence par cxposer les conditions requises d'un appareil
propulsif pour bateau de peche: puissance dc traction, lie lice a
grand diametre et a petit pas, rapport poids/puissance pouvant aller
de 25 a 35 kg/ch, faible longueur, possibilite dc fonctionner durant de
longues periodes entre deux revisions, et de se preter £ d'importants
travaux d'entretien a bord. II examine les avantages ct les in-
convenients des semi-diesels, dcs diesels ct des moteurs a essence,
et traite ensuite de divers aspects particulicrs de 1' installation:
carlingage ct montage du moteur, pose de 1'inverseur, du reductcur
et de 1'arbre. L'auteur d6erit les systfcmes d'cchappcment du type
"sec" et a injection d'eau, ainsi que les systemes dc graissagc par
carter sec et par carter classique. II etudie divers dispositifs de
refroidissement : pompe classique a piston, pompe a engrcnages,
pompe centrifuge, refroidissement direct par eau de mer, ct systemes
indirects tels que le "refroidisseur de quille". 11 expose un agence-
ment des organes d'alimentation reduisant an minimum le risque
d'incendie, et menlionne certaines precautions & prcndre contre Ic
feu. L'auteur etudie les auxiliaiiss de bord (prise de force pour
treuil ou autre equipement de pont, generatrices dc courant, moteurs
auxiliaires) et Temploi de Thelice a pas variable. II traite poin-
ter-miner des divers types de commandes el d'appareils dc controle
et de leur agencement.
Tipos de motores e instalaciones mecanicas
£1 surtido de instalaciones de fucrza de que se dispone actualmente
constituye una rica y asombrosa variacion de diferentes tipos de
motor que van desde el clasico motor marino a los motores ligeros
de gran velocidad, para automoviles. El autor cxpone en primer
lugar los requisites especiales del motor de una embarcacion
pesquera: fuerza de traccion; helice de paso pequeno y gran
diametro; relaci6n entre peso y potencia hasta 60 u 80 libras/cv
(25 a 35 kg/cv); poca longitud; largos periodos de funcionamiento
entre las revisiones; posibilidades para un considerable manteni-
miento a bordo. Se examinan las vcntajas e inconvenientes de los
motores de bola incandcsccnte, dicsel y de gasolina. Se mencionan
factores especiales de la instalaci6n : soporte o bancada del motor,
colocacion del cambio dc marcha, engranaje reductor y eje motor.
Se describen sistemas de escape dc descarga en seco y en humedo y
sistemas dc Iubricaci6n con colcctor de aceite secos y humedos. Se
examinan varies sistemas dc rcfrigeracieSn : bomba normal dc
piston, bomba de engranaje; bombas centrifugas; sistema directo
de refrigeration por agua de mar; sistemas indirectos tales como
el refrigcrador de quilla. Se describe la instalaci6n de un sistema de
combustible que reduce al minimo el peligro de incendio, asf
como ciertas precauciones contra los inccndios. El autor examina la
instalacion del equipo auxiliar, tal como el dispositivo para accionar
la maquinilla y artes de cubicrta, sistema electrico, motores auxiliares
y uso de la helice de paso variable. Se mencionan los tipos, discno y
distribution dc los mandos del motor y de los instrumentos.
IN the Scandinavian countries the fishing fleets were
mechanized at a very early stage. At that time, this
process could be based largely on engines and mach-
inery components which were designed and built
specifically for their marine purpose. The machinery was
created from necessity and took a classic form which so
well answered the requirements that little cause existed
for detailed research and study of its salient features.
Now fishing fleets elsewhere are facing the same
problem of mechanization, but the situation is quite
different. It is no longer possible to develop and build
engines or equipment for a limited market. Units designed
and built for other purposes must often be adapted and
modified to suit the marine requirements. The general
trend towards higher performance has also necessitated
the introduction of a more refined and more complicated
technique. This has not been gained at the cost of
reliability. On the contrary, reliability and ease of
handling have improved immensely. However, this is true
only if the operator understands engine maintenance
and has a proper place, tools and spare parts for it.
A similar process has taken place in the field of motor
boats for naval, commercial and pleasure use. The follow-
ing account is mainly based on the author's experience
from this branch of technology and from installation
and service of engines in Swedish west coast fishing
vessels.
INSTALLED POWER
For a pleasure craft the required power is determined
by the desired top speed, the cruising speed and the hull
resistance at these speeds. For planing craft the position
and magnitude of the hump in the resistance curve at the
transition from displacement to planing condition must
also be considered.
For a iishing vessel, however, the required engine
power is also largely dictated by the demand for pulling
power during fishing. This is the difference between the
available propeller thrust and the resistance of the hull.
Both vary with the speed, and it is valuable to know
both these curves plotted against speed. They can be
based on model tests and/or calculation, but many small
boat projects cannot carry the cost of either. In such a
case the designer must resort to rules of thumb plus
experience. Results from towing tests have also been
published and it is often possible to calculate the resis-
tance by using the data from a similar hull.
The available propeller thrust increases with diminish-
ing speed. At zero speed the thrust can be about 50 to 60
per cent higher than at full speed. Among other factors,
the rate of increase is influenced by the pitch ratio in
such a way that a larger diameter and a smaller pitch,
within reasonable limits, improves the pulling power at
low speed with some sacrifice of top speed.
[345]
The propeller characteristics alone are not decisive
since the power and torque delivered by the engine also
varies with speed.
A controllable pitch propeller can improve on the
thrust curve because engine speed can be kept constant
so that full engine power is available regardless of the
towing speed.
This is in fact the most important, but often over-
looked, advantage of the controllable pitch propeller,
which is sometimes considered as just an alternative to a
reverse gear (fig 1),
Thrust
Retfotonce
Controllable pitch propeller
Fwtd pitch propeller
low pitch ratio
Rxtd pitch propeller
high pitch ratio
Speed
Fig J. Towing characteristics with fixed and controllable pitch
propellers
If the propeller is designed to absorb full engine power
at full speed, the thrust at bollard condition will suffer
from lack of engine power, because the engine can then
only reach about 60 per cent of its full speed with a
corresponding fall-off in output. On the other hand, if the
propeller is designed for bollard condition, it can give a
a high thrust at zero and low ship speed, but it will not be
able to absorb the full engine power at full speed. The
engine must then be throttled back to avoid over-revving
with a corresponding loss of thrust and performance
under free-running conditions.
To design a fixed pitch propeller for top speed usually
is less advantageous mainly because most fishing craft
have a very steep resistance curve at higher speed. To
push the speed above 8 to 11 knots (depending on the
size and length of the boat) requires a great increase of
power. This is certainly the case when putting a motor
into one of the older types of fishing boats, which usually
have such convex buttock lines in the afterbody that
they will squat considerably if high engine power is
applied. A more modern design, with a good "run" aft,
especially those with a transom stern, will not suffer
from this to the same extent. The demand for more
speed increase is better met by improvements in hull
form than by power increases.
It must also be borne in mind that higher engine power
not only means higher cost, weight and bulk, but also
greater stresses due to vibration and propeller thrust.
The minimum installed power should be determined by
the propeller thrust required for towing of the fishing
gear for safe manoeuvring and to keep pace and course
in wind and sea. The shape and lines of the hull have a
great influence on the characteristics of the vessel in this
respect, and also the proportion of lateral plane to the
aerodynamics of the body above the waterline.
GENERAL REQUIREMENTS OF FISHING
VESSEL ENGINES
Weight
The weight requirements are moderate for fishing boat
engines. Up to 60 to 80 Ib/hp (25 to 35 kg/hp) is an
adequate weight/horsepower ratio. Modem diesels of
industrial, marine or automotive type offer no problem
in this respect nor does, of course, the petrol engine.
Size
It is important that the installation is short, as the engine
has to compete with the fish hold for the length available.
This applies not only to the engine itself but includes
also the whole of the drive shaft line with thrust bearing,
shaft seal, propeller mechanism, reduction and reverse
gear. If the engine is fitted with power take-off at the
front end for the deck machinery or windlass, this must
also be built as short as possible
Athwart ships, sufficient room is required for easy
access to all components which have to be serviced on
board.
Height is seldom critical in small open boats. However,
it must be possible to lift the whole engine out, especially
if it is an automotive type which requires periodic
workshop overhaul.
Vibration
In fishing boat engines there is no pronounced require-
ment to strive for extreme quietness or vibration-free
running. Elastic mounting is seldom regarded as
necessary.
Running characteristics
A fishing boat engine must often run for long periods at
very little load. The combustion even at low load must be
sufficiently clean to prevent excessive carbon deposits
to be built up. Sales pamphlets never have anything to
say about the behaviour of the engine at part load. Price
per horsepower is often regarded as the most efficient
sales argument. As engines are designed and built to be
sold, it is natural if the part load characteristics are often
sacrificed or overlooked to attain favourable top power
figures in the brochure.
The degree of utilization is usually very high. Some
fishing boats are run for more than 4,000 hours a year,
e.g. 55 per cent of the total time. For this reason the time
between overhauls must be long. For 4,000 hours the
engine must function without servicing other than
cleaning the filters and injectors, valve clearance adjust-
ment and other minor operations. A top overhaul can
possibly be accepted, entailing cylinder head removal,
decarbonizing and grinding of valves.
In this respect the requirements are quite different
[346]
from those in the pleasure boat field. Here running
periods of more than a few hundred hours a year are
exceptional.
Overhaul
Regarding overhaul work, the general trend points
towards all major overhauls being conducted by work-
shops ashore, suitably equipped for the purpose with
tools, spares and trained personnel. The traditional
requirement of a marine engine to enable complete
stripping and repair on board was long ago dropped in
the pleasure boat field. This means in practice that
automotive engine types with underslung bearings are
readily accepted. It is this new concept that has made
possible the low price, thanks to mass production, the
low weight and high specific output of modern pleasure
boat engines.
Even if the same trend has made itself felt in the
fishing boat field, the conditions are very different.
Shore workshops are often remote, especially in less
industrialized countries. The organization of the fishing
is also such that it is desirable that repair and main-
tenance of the engines can be carried out entirely on
board. If this is the case, the engine design must be
carefully studied so that the vital service points can also
remain accessible in the actual installation on board.
HOT BULB ENGINES
When the fishing fleets of the Scandinavian countries
were motorized the mechanization was largely based
on the use of hot bulb engines. A great number of
manufacturers concentrated their efforts on this type of
engine which in many respects was eminently suited for
fishing vessels. It soon got a well-deserved reputation for
reliability and it also had other merits. It was not very
demanding in the quality or filtration of the fuel, thanks
to its ignition system and the low injection pressure
which made the pumps and nozzles less sensitive to wear
and dirt. It was so heavily dimensioned that it could stand
corrosion as well as a certain amount of neglect and
maltreatment without mechanical protests.
The hot bulb engine has found a good market as a
marine and industrial engine in several remote countries
where its simple, rugged construction and low demand on
workshop support have been highly appreciated. In
more industrialized countries, however, sales have re-
ceded in favour of diesel engines, mainly as a result of
the demand for higher power and less bulk and weight.
The manual work and service of the hot bulb engine is
also a heavy and dirty job and does not satisfy modern
standards.
Another objection against the hot bulb engine for
marine use has been the necessity to preheat the bulbs with
blowlamps, which means a certain fire hazard. Scandi-
navian fishermen have been used to this procedure for
many decades but in many other areas the handling of
blow torches on board a wooden boat must be regarded
as rather dangerous. Modern hot bulb engines have
electrical preheating systems but, in spite of this and other
detail improvements, the engine is seldom competitive
compared with other types.
DIESEL
For smaller fishing boats the most common replacement
for the hot bulb engine is the diesel. In the lower power
bracket, up to about 25 hp, slow or medium-speed
engines are available, designed and built for industrial
or marine use. There are quite a few Swedish makes (e.g.
Bolinder), some Norwegian (e.g. Sabb and Marna), and
several British and Italian. This class of engine is simple
in design. Most are built to enable overhaul on board
and often so slow running (800 to 1,200 rpm) that they
can be directly coupled to the propeller in a small
fishing boat. One installation difficulty for the engines of
industrial type is often that the mounting feet are placed
rather low, which suits a stationary bedplate but is
less adaptable to engine bearers in a boat.
In the higher power bracket, above about 25 hp
and up to about 300 hp, the market is mainly dominated
by automotive-type diesels. In most cases the marine
engine is made up by "marinizing" an existing basic
automotive engine, which is fitted with reverse gear, see-
water pump, heat exchanger and a water-cooled exhaust
manifold. With few exceptions even the "pure" marine
engines have much resemblance to automotive engines
and generally follow their standard in layout and
construction.
The main advantage of this system is that the engine
can be very cheap for the power it gives, thanks to mass
production methods that can be employed for the large
series of the automotive industry. The marine service
can also benefit from the experience gained from the
automotive field. Availability of spare parts should be
better and the network of service depots and agents more
efficient than for a pure marine engine made in small
numbers.
Generally speaking, experience with the automotive
engine at sea is positive, but attention must be drawn to
some characteristics which are often overlooked by the
boat designer and user. The auto engine usually affords
less accessibility for service and overhaul on board than
marine engines. The auto engine's crankshaft is invariably
carried in underslung main bearings in the cylinder block.
This gives a compact, sturdy, light and cheap design
which is desirable for a vehicle engine installed for
accessibility from underneath. In a boat, however, con-rod
and main bearings cannot be got at without lifting the
whole engine out. A few engines are fitted with crankcase
doors either on the block or on the oil sump, but these
are usually rather narrow and difficult to work through.
Overhaul or repair of bearings with the engine on
board is hardly recommended for auto engines. They
have lead bronze bearings and hardened crankshaft
journals, and in the case of bearing seizure the source of
failure and the amount of damage to shaft and the
other bearings is usually such that the engine should be
treated in a proper workshop. The moving parts are also
highly loaded and require an exactness and cleanliness in
their fitting that can seldom be guaranteed on board. The
bearing cap bolts must, for instance, be tightened with a
torque wrench or by measuring the elongation, which is
difficult to do in the cramped space on board.
Another class of engine which has recently been de-
veloped is the auxiliary engine for sailing boats. These
[347]
have one or two cylinders and a power of about 10 to 20
hp. They are rather high revving and are largely based
on automotive practice but their dimensions and equip-
ment are dictated by their marine use. Naturally, a sailing
yacht engine must be very compact to enable it to be
hidden below the deck. Their lower half and mounting
feet are also designed to permit installation far aft and
in a narrow space, that is, conditions very similar to
those in a small fishing boat. It seems that this type of
engine deserves more interest from the designers of
smaller fishing craft.
PETROL ENGINES
Because of the low weight and small dimensions the
petrol engine is the natural choice for an outboard
motor, which in turn might lend itself better to adoption
in existing small fishing boats than the inboard engine.
There seems to be a demand for a diesel outboard
motor, but as far as is known there is only one such
on the market. This is natural, for the overwhelming
number of outboard motor customers are the pleasure
boat owners and for this application, low weight and
silent, smooth running is much more important than
low consumption and cheap fuel.
For inboard installations in fishing boats the petrol
engine can seldom compete with the modern diesel. Its
main advantages are low weight, little noise and vibra-
tion, but none of these is any great problem in a low-
powered fishing boat. It is sometimes argued that
handling and maintenance are understood and learned
more easily by people used to motor car engines. How-
ever, in coastal areas ripe for mechanization of fishing
craft the vehicles with which mechanics and workshops
first come in contact are usually commercial vehicles
which are fitted with diesel engines more often than not.
One advantage of the petrol engine is that it can be strip-
ped down to its smallest part and reassembled without a
clean workshop being available. The injection pump and
injectors of a diesel, on the other hand, require the utmost
cleanliness and care due to their small clearances and
passages which are not found anywhere in the petrol
engine or its systems.
Another advantage of the petrol engine is that ft is
easier to start by hand cranking due to its lower com-
pression ratio.
It is cheaper in first cost, which is, however, outweighed
after some time of operation by its higher consumption
and fuel cost
The fire risk is higher. This can efficiently be kept under
control by proper installations and restriction on the use
of open fire and smoking on board. However, such
conditions certainly do not prevail in primitive fishing
boats.
A great drawback of the petrol engine in small open
boats is the ignition system which is sensitive to moisture,
dampness and water spray.
There are very few inboard petrol engines being built
today as pure marine engines. Most of the available types
are marinized automotive engines. From a maintenance
point of view they must be treated like the high-speed
diesels.
ENGINE BEARERS
The purpose of the engine bearers is to support and
distribute the engine weight and the stresses set up by
thrust, torque and vibration to such a proportion of the
hull structure that there is no risk of excessive distortion
or damage even when running at full power in a heavy
sea. The classic type of marine engine was supported by
surfaces along the sides of the bedplate running the whole
length of the engine and resting against the top surface
of the engine bearers. These were made to fit the support
surfaces of the engine.
Modern engines usually have no such support surfaces
but the weight is taken by four or six feet. This allows
more freedom in the shape of the bearers, which have to
be built up only to meet the feet. However, they must still
be solid enough to distribute the load from the engine.
They must extend for a considerable distance fore and aft
of the engine and should be connected to the longi-
tudinal bottom hull stringers. This is of particular
importance in the aft part, for flexing of this part of the
bottom can upset the shaft line and cause bending
stresses in the shaft, couplings and gearbox. The bearers
should not end too abruptly. A discontinuity in the
strength can give rise to stress concentrations.
For the design of the bearers it is important to study
Transverse piece
of round iron
inserted in holes
in bearer
Fig 2. Alternative arrangements of engine holding down bolts in wooden bearers
[348]
the bottom half of the engine. Many modern engines
have their starter motors, generators, oil filters and other
parts placed rather low. It must be ascertained that all
such parts are accessible for maintenance and not
blocked by the engine bearers.
The same care must be applied to the gearbox. Oil
coolers and oil pumps are sometimes placed low in the
oil sump and require space for withdrawal in case of
failure.
So-called "french screws" or "coach screws" should
not be used for the engine mounting as these have to
be unscrewed from the wood bearers each time the engine
is lifted out of the boat. It might have been acceptable
with the old-type engines where at least the bedplate
spent its whole life mounted on board. Instead, the hold-
ing down bolts should be through-bolts or possibly french
screws with their heads sawn off and threaded top ends
(fig 2).
Under the engine feet there should be generous metal
pads to prevent the feet from being pressed into the wood
surface.
It is a great advantage if the engine feet are adjustable.
Especially if the engine is placed far aft, it is preferable
if the aft feet can be placed higher than the front ones.
Otherwise the bearers might be of dangerously low sec-
tion in the aft critical part. Adjustable feet can also
greatly facilitate the lining up of the engine.
Another way of saving time of lining up is to use
wedge-shaped rectangular washers under the feet with
oblong holes (fig 3).
Wedge
Fig 3. Wedged inserts' under holding down holts can facilitate
alignment
REVERSE GEAR
If the boat has a fixed pitch propeller the engine must be
fitted with a reverse gear. This contains two clutches:
one for forward, one for stern drive. Several types of
clutches are used: conical with or without linings,
multiplate or brake band types. A common fault with
many gearboxes is that one of the clutches does not
disengage completely with the lever in neutral. The
result is that the propeller turns a little. This can be
accepted in a pleasure boat but can often be a nuisance
in a fishing boat during handling of nets and lines.
Mechanical reverse gears have a manual adjustment
to compensate the linkage for the wear of the clutches. It
is important that instructions are given on how to make
this adjustment, for in many cases the mechanism is so
designed that increased wear results in a rapid increase
of clutch pressure. This in turn increases the risk of
clutch slip, which increases the rate of wear, etc. Clutch
slip also gives rise to friction heat with risk of distortion
and damage to clutch plates.
In gearboxes of more advanced design the clutches are
compressed by oil pressure delivered by a separate
oil pump. No adjustment is needed in this case.
The reverse gear train is often of planetary type,
either with helical or conical gears. In the "twin disc"
system there are two separate gear trains for ahead and
astern, both in constant mesh and connected to the drive
shaft via two separate clutches. This type of reverse gear is
usually made with a reduction in each gear train. In the
aforementioned type the reduction gear is mechanically
separate, even if it is flanged to the reverse gearbox.
The gearbox is often lubricated by the engine system,
which has the advantage that only one oil level has to be
checked and that no separate oil pump is needed. It
means, however, that the gearbox is fed with oil con-
taminated by carbon from the combustion and that the
engine is lubricated with oil which might contain
abrasives from the wear of the gearbox clutches.
A separate oil system for the gearbox is to be preferred
also for the reason that a proper grade and quality of
oil can be selected for the gearbox, differently from the
engine.
REDUCTION GEAR
The best propeller efficiency is obtained at a shaftspeed
which does not necessarily coincide with the crank shaft
speed of the engine. It is usually lower. It is not always
possible, or even advisable, to design for maximum
propeller efficiency. Limitations of draught can, for
instance, favour a smaller, fast-running propeller with a
sacrifice in efficiency. But in many cases a reduction gear
is needed to enable an acceptable combination of engine
and propeller speed.
The reduction gear can be incorporated in the reverse
gear or it can be flanged to its housing. In a few cases
it is separate from the engine and reverse gear. The most
usual design has only two helical gears but planetary
reduction gears can be built smaller and lighter, especially
for higher reduction ratios.
The efficiency of the reduction gear can be of the order
of 95 to 98 per cent, that is, a loss of 2 to 5 per cent of the
engine power has to be taken into account. Contrary to
the loss in a reverse gear this is continuous, and the
corresponding heat loss must usually be taken care of by
an oil cooler incorporated in the sump or separately
mounted.
SHAFT LINE
The propeller shaft can be made of steel or bronze, but in
modern motor yachts, where a small diameter and long
life is essential, the shaft is generally of either stainless
steel or monel. MoncI is a bronze alloy with a high
nickel content, which is very resistant to salt-water
corrosion and fatigue stresses.
In pleasure craft, the shaft is nowadays almost in-
variably carried in rubber bearings. These have proved
to have a long life and abrasive dirt is either flushed
through or bedded in without harming the shaft journal.
Thanks to their resilience, a small inaccuracy in lining up
can also be tolerated.
[349]
The rubber bearings are water-lubricated, and it is
important that the water supply is generous. Water
scoops are a good help and their resistance is no problem
in a slow vessel. A worn rubber bush cannot, of course,
be repaired but must be replaced. In remote areas the
old-type white metal lined bronze bush might have the
advantage of being repairable with local means without
a spare part supply.
A stuffing box is fitted to the front end of the stern pipe.
There are several types of very efficient rubber seals but
all have the disadvantage that the shaft has to be dis-
mounted and withdrawn if the rubber seal must be
replaced. For practical reasons the old type of seal with
packing material of greased yarn compressed by a gland
nut is preferred.
In modern yachts it is common practice not to attach
the stuffing box directly to the stern pipe, but to con-
nect it via a piece of flexible rubber hose with hose
clamps (fig 4). This ensures that the stuffing box is
Fig 4. Stern tube with flexibly mounted stuffing box
concentric with the shaft even if the lining up is not
absolutely perfect and also that the box follows the
movements of the shaft. In such installations where the
engine is flexibly mounted, a directly-coupled propeller
shaft can be accepted, although the layout is theoretically
wrong, providing the stuffing box is sufficiently free to
move. Watertightness depends on the tightness of the
rubber hose. It is thus essential that the hose is a close
fit, that it enters over the pipe a distance at least its
diameter and that the hose clamps are double, of first-
class quality and well tightened.
The propeller thrust is usually taken up by a thrust
bearing in the gearbox of a solidly mounted engine. In a
theoretically correct elastic mounting the engine must be
"fully-floating". This means that there must be an inter-
mediate cardan shaft with two couplings, either rubber
couplings or universal joints. Some plants actually run with
the universal joints transmitting the propeller thrust. This is
the case in a class of Swedish Coast Guard transport
ships (3x210 hp) but the normal arrangement is to use
a separate thrust bearing and fit a spline on the cardan
shaft. This is the ideal solution but unfortunately it is
also the most expensive and takes up much valuable
longitudinal space.
Even if the engine is solidly mounted, as is generally
the case in a fishing boat, a flexible coupling on the output
shaft is of value, preferably one which can take axial
loads. A rubber coupling can take a certain amount of
angularity and also some misalignment. The manu-
facturer usually claims permissible values.
EXHAUST SYSTEM
The exhaust manifold on the engine and the exhaust pipe
cannot benefit from any air flow cooling such as in a
motor-car installation. In a boat they must be cooled
with water. An important part of the marinizing of an
automotive engine is therefore the replacement of the
standard exhaust manifold with a water-jacketed mani-
fold, usually of cast iron. Some marine engines have
exhaust manifolds of cast aluminium. This can give rise
to trouble and leakage on longer units because of the
difference in heat deformation of the aluminium manifold
and the cast iron cylinder head. If the short pipes between
exhaust ports and manifold are not water-cooled they
should be lagged with asbestos.
The exhaust pipe can be of the "dry" or "wet" type. A
dry exhaust system is water-jacketed and cooled by the
cooling water leaving the engine and passing in the jacket
between the inner and outer pipe. Unless self-draining,
the jacket must have a drain cock at the lowest point.
In a wet system the cooling water is injected in the
exhaust pipe and cools the exhaust gases directly. It
should be noted that the vaporizing of the water might
expand more than the contraction of the cooled exhaust
gas, so that a certain back pressure can be expected.
However, the system is cheaper, simpler and at the same
time has a good silencing effect. For these reasons it is
more common than the dry system.
The injection of the water into the pipe must take
place at a point where it is absolutely safe from being
sucked backwards into the engine. The first part of the
pipe is water-jacketed and the water injection is arranged
after a downwards bend of the pipe.
The exhaust pipes are made of stainless steel or gal-
vanized steel. Petrol engines can have pipes of copper,
but for diesel the copper can become corroded by the
sulphur content of the exhaust gases, especially with a wet
system.
If the engine is flexibly mounted the exhaust pipe must
also have a flexible connection, made of a heat-resistant
hose or twin bellows. This part is uncooled and must be
insulated with asbestos.
A modern system is to make the whole pipe of rubber
hose, which works well if the water spray in the hose is
sufficient.
There must be ample clearance all around the exhaust
pipe so that no inflammable material can catch fire or get
overheated by radiation.
LUBRICATION SYSTEM
It has often been claimed that a true marine engine must
have a dry sump lubrication system (fig 5). This means
\ Scavenging pump
Fig 5. Dry sump lubricating system
[350]
that there is a separate oil tank and that the engine is fitted
with two pumps: a pressure pump to feed oil from the
tank to the lubrication system, and a scavenge pump to
suck the oil from the sump and back to the tank. The
scavenge pump must have slightly larger capacity to
ensure that the sump is not overfilled. In practice it will
pump oil, plus a certain quantity of air, which is then
separated in the tank. On its way back from the engine
the oil may have to pass an oil cooler.
The dry sump system is used on most larger marine
engines. The wet sump system is used on most small
engines and all automotive engines, even in their mari-
nized versions (fig 6). In this case the oil sump is also the
Oil pump Cooler
drain the oil down into the bilge or into the engine tray.
For this reason a marine engine must be fitted with a
separate hand-operated drain pump. If the reverse gear
has a separate oil sump the drain pump can also be con-
nected to this with three-way cocks, or it can be fitted with
a separate drain pump on larger units.
The crankcase is usually fitted with a funnel or trunk
to ventilate the oil fumes. In a marine installation where
the engine is placed in a manned engine room or inside a
cabin these fumes can be very unpleasant, especially
if the engine is worn so that combustion gases and
pressure can blow past the pistons. To prevent this the
funnel can be connected to the air intake, so that the
crankcase is kept under a certain vacuum and excess oil
fumes are drawn into the intake air. For supercharged
engines this system is not readily adaptable as most
manufacturers of superchargers are anxious to get as
clean air as possible to their impellers, and indeed de-
posits on the impeller vanes can have a very bad effect
on their efficiency.
COOLING SYSTEM
The cooling of a marine engine might at first sight seem
very simple since there is the whole sea full of water for
cooling. In fact there are several factors which complicate
matters considerably.
At high speed a suitably formed scoop might be all
that is needed to feed sea water to the cooling system,
but with the exception of pure racing boats a marine
installation needs a pump (iig 7). Many types of pumps
Fig 6. Wet sump lubricating system
oil tank and there is only one pump sucking oil from the
bottom of the sump to the lubrication system. The oil
cooler, if any, is placed in the feed line from the pump,
not on the return side as in the dry sump system.
One advantage claimed for the dry sump system is
that there is less risk of air introduction through move-
ments and rolling in a seaway. Another advantage is that
the oil sump is less bulky, so that the engine can be more
easily accommodated in the boat.
In practice, the risk of the oil splashing in the wet sump
and of aeration of the oil is not very great. Regarding
space requirements, usually the fly-wheel is the lowest
part and governs the position of the engine on board.
The wet sump system works well but when an auto-
motive engine is marinized it should be noted that it
must often be inclined up to 5° to 15°. In some cases the
sump must be redesigned, the suction pipe repositioned
from the pump to the lowest part and the oil dipstick
re-marked to compensate for this. An oil cooler might
have to be introduced because the sump is not cooled
by the air flow as in a motor-car.
In an automotive installation the oil is easily drained
directly from the oil plug into a well or tank. In a boat the
oil plug is very inaccessible, and even if there is a tray
under the engine, this is seldom large enough to permit
drainage of the whole oil quantity in the boat. Also from
a fire risk point of view, it is not recommendable to
[351
Regulating valve
Pump
Fig 7. Salt-water cooling
are found on marine engines but most have their different
limitations. The piston pump is the classic type, which has
the advantage on a reversible engine that it works in
both directions of rotation. However, it is rather heavy
and clumsy and its valves need a great deal of attention in
order not to become inoperative due to corrosion, sand,
weed or dirt.
The gear-type pump has also been very common. It is
simple and has no moving parts other than two gear
wheels with a coarse pitch. However, grit and sand can
cause rapid wear of gears and housing and its capacity is
dependent on a tight fit between these. A rubber coating
on the gear wheels can increase their life but a separate
drive gear train between the wheels is then needed, where-
by its simplicity is lost.
The centrifugal pump is simple and reliable but its
capacity is often found to be too dependent on the
engine speed of operation as the delivered pressure varies
with the square of the impeller tip speed. A positive
displacement pump is generally preferred.
Among these it seems that the vane type with a flexible
rubber impeller has captured the market in the last ten
years for small and medium-size marine engines. The
radial vanes deflect against a half-moon-shaped cam
in the housing, and once a suitable material for the
impeller was found it seemed that this type of pump met
the demand very well. It has been widely employed both
as salt-water pump and bilge pump. It must always run
wet. Dry friction will cause rapid wear of the impeller.
To eliminate this risk with a bilge pump it is fitted with a
clutch and it is advisable to blend a continuous small
water flow into it from the water-cooling system. A worn
impeller can easily be replaced, but here again is an item
dependent on a proper spare part supply and which
cannot be repaired with local resources.
On the intake side of the salt-water system there should
be a strainer so arranged that it can be removed and
cleaned with the boat afloat when the sea-water cock is
closed. Still better is a twin system to permit cleaning of
one strainer with the other in operation.
The water temperature is regulated by hand or
thermostat. A temperature as high as 165" to 175° F (75°
to 80° C) is aimed at as this has a very beneficial effect in
keeping cylinder wear down. The hand cock or thermo-
stat is so arranged that a varying proportion of the water
is by-passed to the outlet side. A thermostat in the sea-
water system will be corroded rather soon and must often
be replaced but the mass-produced types are very
cheap (fig 8).
Thermostat
Thermostat
Fig 8. Salt-water cooling with thermostat
The direct sea-water cooling system will cause cor-
rosion in the cylinder block and head. On heavier
engines where the dimensions are generous this is
accepted. The unfortunate thing is that the rate of
corrosion increases with the water temperature which
should be kept high to diminish cylinder wear.
This problem is eliminated by using indirect cooling,
which has gained ground more and more, first on the
automotive types with their thinner cylinder walls, but
also on other types. The salt water is led through a heat
exchanger to cool the circulating fresh water. The design
of the freshwater pump and the thermostat can be
taken over directly from the corresponding automotive
engine and will seldom give any trouble (fig 9). Most
manufacturers of small engines have preferred to mount
the heat exchanger directly on the engine, combined with
a header tank. This facilitates the installation of the
engine and ensures that the layout and execution of the
cooling system is kept under control by the manufac-
turer. The system usually works well but the design of
the heat exchanger must be rather compact to allow
accommodation on the engine. This often leads to
Cooler
Pumps
Fig 9. Freshwater cooling
cooling elements with narrow passages, which can be
clogged and are difficult or impossible to clean. If the
boat is expected to operate in dirty water, in rivers for
instance, it may therefore be better to accept a larger
heat exchanger with wide and straight tubes. This must
then often be mounted separately, preferably below the
floors.
A very simple form of indirect cooling is the keel
cooler. In this case the heat exchanger consists of a pipe
or a bundle of pipes placed on the outside of the boat
bottom. The fresh water circulates through the pipes
and is cooled directly by the water flowing around them.
One disadvantage is that the outboard cooler is exposed
to mechanical damage in case of grounding or beaching
or hitting a floating object. Engine manufacturers have
been rather sceptical about the outboard cooling system
for this reason and also because the design and execution
is entirely in the hands of the local boatbuilder, often too
far from their control.
Even with a freshwater cooling system a certain
corrosion can occur in the engine. Manufacturers
sometimes recommend the use of rain water, but a very
simple and good method is to add a small percentage of
soluble oil to the water system.
FUEL SYSTEM AND TANK INSTALLATION
The quality of the fuel system is of utmost importance in
a marine installation. Many engine failures and even
catastrophes can be traced to a faulty or badly maintained
fuel system. A leaking fuel system means a potential fire
risk, which is one of the worst dangers on board.
In one litre of fuel there is more energy stored than in
half a ton of dynamite, but still there is little danger so
long as the fuel is kept in the tank and in the system,
because it has no contact with oxygen. The important
thing is to prevent it from leaking.
Welded steel is used for the tank. Copper is not recom-
mended because of the sulphur content of the fuel. The
tanks should be tested with a hydraulic pressure to check
the tightness. It is a good rule to avoid flat plates as
much as possible, as these are more prone to vibration
and cracks.
The filler cap must be so placed that excess fuel is
discharged overboard and not into the boat if the tank is
overfilled by accident during refuelling. The filling funnel
should end above deck, never below deck, for during
filling the fuel vapours will otherwise flow out of the
mouth and down into the bilge. Fuel vapour is heavier
than air.
[352]
To facilitate the discharge of fuel vapours there
should be a vent pipe from the tank to the boat's side.
Rules for the dimensioning and design are found in the
recommendations of several organizations; for instance,
the Swedish Boatyard Association.
It should be possible to remove the tank completely
for repair or cleaning without having to cut out a piece
of the deck or superstructure.
The fuel pipe should be led from the bottom of the
tank up through its top. This is the safest system. If the
line is taken down from the lowest part of the tank
there must be a good quality cock valve directly fitted
to the tank. A dished sludge trap with a drain plug
should be arranged below the fuel pipe and in the tank
bottom.
The pipes must be well clamped to prevent vibration.
It is recommended to fit rubber between the clamp and
the copper pipe to eliminate the risk of wear and cor-
rosion in the pipe. The part closest to the engine should
be flexible, either with a bend or a hose. The hose
should be of synthetic rubber, not of plastic which can
age and lose its elasticity
A fuel filter should be fitted in the line. It is always good
to have a double system so that one filter can be cleaned
without stopping the engine. Most diesels have such a
twin filter either fitted on the engine or as part of the
delivery.
FIRE EXTINGUISHING SYSTEM
Considering the often catastrophic effect of a fire on
board it is surprising how many boats are running
without any fire-extinguishing equipment or with
defective equipment. Assistance is usually distant, and
in practically all cases one is left to do what one can to
save ship and life with the resources on board. In case
of a fire in the fuel there is little to be done with water.
It might just make things worse by spreading the fire.
The risk of fire is diminished first by a well laid out and
well executed fuel tank and electrical installation. It is
also important to keep the installation in order, to check
the systems regularly, look for leaks, loose contacts,
worn insulation and other defects.
Open fire must also be used with great care. Many
disasters have occurred and many lives have been lost
because careless smokers throw burning matches,
glowing ashes and tobacco around.
In case of a fire it is important to act quickly and to
have something to act with. A main rule is to prevent air
access. A piece of canvas, a blanket or even a cap or
jacket thrown over the fire might be of good help, and
better still if it is first soaked in water.
A portable fire extinguisher should be placed close to
the helmsman and one in the engine room if it is manned.
The portable extinguishers are of short duration as they
must be light, so it is good to have several.
In larger boats there should also be a fixed system of
carbon dioxide bottles which can be discharged in the
engine room and the tank room by pulling a handle at the
helm. Before this is done the engine room must be
evacuated and the hatches should be closed to prevent air
access.
It can also be of benefit if the fuel cocks can be shut off
remotely from the bridge by pulling a handle so that no
fuel can leak out and make the fire worse. This is seldom
seen on yachts or fishing boats, but such a system is used
on the fast motor torpedo boats of the Swedish Navy.
AUXILIARY MACHINERY
In larger fishing craft fitted with a trawl winch, this is
often driven by the engine via a front power take-off. The
classic system consisted simply of a flat belt pulley on the
front end of the crankshaft driving another pulley on the
trawl winch shaft. It was brought into action by tension-
ing the flat belt with the aid of a movable jockey-pulley.
This simple system unfortunately does not fit well on
modern engines and is now being superseded by more
refined systems. The modern engines run too fast to
permit a direct belt drive. The multi-cylinder engines
also require great attention to the problem of torsional
vibration, with the result that an elastic coupling might
have to be introduced in the transmission. In some
automotive engines the front end of the crankshaft is not
at all designed for a power take-ofT.
The clutch, reduction gear and elastic coupling all add
to the installed length of the plant, so that a certain
design effort must be made to make the layout as short
as possible.
Fig 10. A compact combination of oil operated clutch, reduction gear, controllable pitch propeller control
mechanism and thrust block.
[353]
M
TABLE 2
Transmission
Component
Cost
Installation
Cost
Operating
Cost
Maintenance
Cost
Weight
Control
Safety
Mechanical
1
3
2
4
2
4
4
Electric
4
4
1
3
4
1
3
Pneumatic
2
1
4
2
3
3
2
Hydraulic
3
2
3
1
1
2
1
power hoist, topping lift and vangs for handling the pots.
While not strictly deck machinery, the pumps that
sardine and herring seiners frequently have for trans-
ferring the catch from purse seine to boat and from boat
to processing plant, serve the same function as winches
and brailing nets.
One deck machine not listed in table 1, but carried on
almost all fishing boats, is an anchor windlass, now
generally power-driven on larger boats.
POWER FOR DECK MACHINERY
Power to drive deck machinery can be supplied by either
the propulsion or auxiliary engines. In vessels of less
than 100 GT the power source is generally the propulsion
engine.
The main types of transmission are:
• Mechanical
• Electrical
• Pneumatic
• Hydraulic
CUSHION
VALVE
-o
7
PRESSURE
REGULATING
VALVE
SUPERCHARGING
PUMP 1
Fig 1. Typical closed loop circuit
Each has advantages and shortcomings with respect to
cost, weight, control precision, safety and maintenance.
Table 2 gives an estimated relative comparison of those
systems, 1 being the most and 4 the least advantageous.
This comparison is not absolute but it does indicate a
favourable position for hydraulic drives.
HYDRAULIC TRANSMISSION
Systems
Hydraulic systems and equipment applied to fishing
vessels are adaptations from other industries. Lerch (1964)
describes the two basic hydraulic systems, that is, the
closed loop, sometimes called "hydrostatic", and the open
loop. These systems are discussed below in general
terms. The symbols used in the accompanying diagrams
are the so-called JIC (US Joint Industry Conference)
symbols (Lerch, 1964).
Closed loop system
The usual characteristic of the closed loop system (fig 1)
is one pump and one motor in a circuit, where the pump
discharge goes directly to the motor inlet and the motor
outlet returns directly to the pump suction. It is possible
for one pump to supply oil to several motors and
cylinders in series, but all would have a common speed
depending on the displacement of the pump. The pump
has a variable displacement which controls both speed
and direction of motor rotation.
This system was developed to provide alternatively
rapid movement and precise control of large guns, both
in coast defence and on warships. The system provided
variable speed and load, using constant speed electric
motors for prime movers. This eliminated the need for
frequent starts of these motors whose size and number
Cylinder-block
Drive-
Pistons
Cylinder block
Fig 2. Schematic arrangement of axial type piston pump or
motor
[356]
with each gun or turret was such to tax the power
supply with high starting currents.
The military requirement of compact size for the
amount of power transmitted caused the development of
high pressure systems, generally about 3,000 lb/in2 (211
kg/cm2).
A variation of the system is used in electro-hydraulic
steering gears of larger ships, where rams replace the
motor in the closed loop.
The high pressure of the usual closed loop system
requires the use of piston-type machines. Fig 2 and 3
show schematically two common piston devices which
can be either pumps or motors. In fig 2 as both the
cylinder block and the drive shaft rotate together, the
pistons move in and out of their cylinders. Ports in the
Outlet
leoction
ting
Inlet
Fig 3. Schematic arrangement of radial type piston pump or
motor
valve plate admit fluid while the pistons move outward
and discharge fluid while the pistons move inward.
In fig 3, similar functions are performed as the cylinder
block rotates and the pistons are guided by the reaction
ring placed eccentrically with respect to the drive shaft.
Where these devices are used as pumps, their displace-
ment is varied respectively by changing the angle between
the drive shaft axis and the axis of the cylinder barrel, and
changing the eccentricity of the rotating pump body
relative to the circular reaction ring.
A common feature of the high pressure piston equip-
ment is that they are designed for positive pressure only
in the cylinders. Vacuum tends to collapse the springs
holding the pistons against the wobble plate or reaction
ring so that running any length of time with a vacuum
will destroy the equipment. This restricts the closed
loop system with piston equipment to machinery where
large overhauling forces will not occur which can
generate a vacuum in either pump or motor. The circuit
usually is fitted with a constant displacement super-
charging pump of small capacity to make up leakage and
to maintain a positive pressure on the suction side of the
main pump and on the motor when it is overhauled.
Fig 1 shows also the supercharging pump and circuit
combined with a relief valve circuit which relieves or
"cushions" inertia pressures introduced to the circuit
when starting and stopping heavy motor loads.
Some vane-type, variable displacement pumps are
on the market which can be used effectively in closed
loop systems with the same degree of control possible
with piston-type pumps. However, since this type of
pump is not internally balanced hydrostatically as are
most vane pumps, which will be discussed later, the
system pressure must be low, generally below about
1,000 lb/in2 (70 kg/cm2) to avoid excessive wear.
The closed loop system has limited application to
fishing vessels under 100 GT. Most piston equipment is
designed to transmit powers greater than necessary for
the deck machinery on these boats. Also the precision
required for this type of equipment makes the cost
prohibitive. The requirements for a pump for each
hydraulically powered deck machine increase the cost
over a system where one pump can supply several
motors.
Open loop systems
The characterisiic of the open loop is that a pump takes
oil from a tank at atmospheric pressure and raises it to
some operating pressure for delivery to one or more
motors or cylinders. The oil leaving the motors or cy-
linders returns to the tank, again at atmospheric pressure.
Two basic loops can be used, one at constant pressure
and the other at constant volume.
In the constant pressure loop, the pump delivers oil to
a header whose pressure is controlled by a regulator.
The motors and cylinders receive oil from the header
through control valves and flow regulators to control
their direction and speed. The simplest circuit arrange-
ment, fig 4a, has a constant displacement pump with a
relief valve to control pressure. For illustration, this
circuit includes three driven devices: (1) a motor re-
quiring direction control, but no speed control, (2) a
cylinder with speed regulation, and subject to over-
hauling forces, and (3) a motor with one direction
rotation having speed adjustment, but not subject to
overhauling. Note that the speed regulating controls are
shown in scries with the motor and cylinder. Where
overhauling is a problem, the pressure compensated flow
control valve is in the return branch so the pressure in the
cylinder (or motor) is always positive, thereby eliminating
air leakage into the circuit through shaft seals, and re-
ducing the risk of cavitation in the hydraulic fluid. If
overhauling is not a problem, the flow control can be
placed in either the supply or the return line with equal
effect. While not shown in fig 4, by-pass speed controls,
discussed below with the constant volume loop, could be
used but only if located between the direction control
valve and the motor. Another feature, not shown but
perhaps necessary where driving a high inertia load, is a
cushion valve similar to that in fig 1 located between the
direction valve and the motor (or cylinder).
Since the pump shown in fig 4a must always deliver its
volume at rated pressure even when no motors are run-
ning, it wastes power. The sudden drop in pressure
through the relief valve converts the pressure energy into
heat which is lost to the system. Two refinements can
improve the efficiency by reducing the energy loss when
[357]
PRESSURE
REGULATING
4a- SINGLE FIXED
DISPLACEMENT PUMP
4 b - DOUBLE RXED
DISPLACEMENT PUMPS
4c- VARIABLE DISPLACEMENT
PUMP, PRESSURE
CONTROLLED SERVO
Fig 4. Typical open loop, constant pressure circuit
motors are not running. Fig 4b shows the constant
pressure loop supplied by two pumps, one larger than
the other. At zero and small demands, the small pump
maintains pressure and the large pump circulates oil
with small pressure change. The only losses at zero
demand are friction in the larger pump and those from
the pressure drop of smaller pump flow. The second
refinement shown in fig 4c is to use a variable displace-
ment pump similar to that used with a closed loop
system, with its displacement controlled by the header
pressure. Thus at zero demand, the pump stroke provides
only enough flow to accommodate system leakage and,
as demand increases, displacement and flow increase to
maintain constant system pressure.
Fig 5 shows a typical constant volume loop, also called
an open centre series loop. The pump circulates all the oil
through the control valves in series. At zero power de-
mand, the only energy loss is the pump and fluid friction
in the system as the pump develops only the pressure
required to circulate the oil. As one or more control
valves are moved to require power, the pump develops
only that additional pressure necessary to overcome the
load on the driven machine.
Since all the pump flow must circulate through the
system at all times, various schemes can be provided to
control motor speed where a motor displacement is less
than the pump displacement, and to regulate individual
motor speed over a large range. Fig 5 also shows several
of these schemes as they might be applied to the constant
volume loop, although in normal practice fewer devices
would be connected in one loop.
The various typical drives perform as described below.
For sake of illustration, all drives are shown as reversing
motors, although the control of cylinders is similar.
Also, for simplicity, no cushion valves are shown
whereas these would be required in services with large
inertia loads or in circuits with large oil flow.
(a) This motor is connected simply for reversing
with constant speed in each direction, and repre-
sents the vast majority of installations appro-
priate for fishing boats.
[358]
BRAKE VALVE
Fig 5. Typical open loop, constant volume circuit
Into* -**
Fig 6. Schematic arrangement of external gear pump or motor Fig 7. Schematic arrangement of internal gear pump or motor
[359]
(b) The addition of a pressure compensated
adjustable flow control valve in parallel with the
motor, between it and the reversing valve, by-
passes a fixed amount of oil with one valve
position but not with the other. Thus an
adjustable reduced motor speed occurs in one
direction but full speed in the other.
(c) The flow control valve in the position shown
regulates motor speed below maximum rpm
in both directions of rotation.
(d) The motor speed and direction control is
essentially the same as (a). In normal operation,
the counterbalance and brake valve is held open
by the supply pressure in the external pilot.
Pressure required to open the valve is about 1
that required by the internal pilot. In the event
that a load overhauls the motor so that loop
pressure drops below the pilot setting, the valve
tries to close until the direct discharge pressure
from the motor can open it. This acts as a brake
on the motor and its speed will decrease to that
at which the external pilot will again open the
brake valve. Ultimately, equilibrium occurs
whereby the motor will accept the overhauling
load at a speed proportional to the load's
magnitude.
As shown, the valve acts as a brake for both
directions of motor rotation.
If braking in one direction only is required, the
brake valve can be located between the direction
control valve and the motor.
(e) This is a two-speed arrangement where two
identical motors, mechanically connected, drive
a common load. An additional valve directs the
flow so the motors are in series, as shown, for
full speed, and in parallel for half speed. Fig 10
shows a motor where the circuit can be changed
from series to parallel internally.
(f) Here two separate motors are controlled
together, so that they can drive separate
machines at proportional speeds irrespective
of the load imposed on either one. The added
mechanically coupled motors shown, divide the
total oil flow into two paths, the volume of each
depending on the displacement of the motor
through which it passes. If the pressure increases
in one path because of the final motor's load,
the flow divider becomes a "motor pump" which
transfers energy from the unloaded path to the
overloaded first path. All the while, both final
motors turn at their original proportional speeds.
(g) This control arrangement is a variation of (b)
and (c). It adds a simple globe valve to by-pass
the motor. Fully opened, the motor does not
run. As the valve is closed, the motor speed
increases to maximum when the valve is fully
closed. This scheme is used to start a motor
smoothly and only incidentally to control speed.
The arrangements shown in (b) and (c) provide
better speed control, as the amount of oil by-
passed is constant, irrespective of pressure drop
across the motor.
For fishing boat applications, the various open loop
hydraulic systems are most advantageous. The equipment
used in these systems is generally simple and rugged in
construction, and mostly the same as that in general
industrial use.
Fig 8. Schematic arrangement of vane pump or motor
Pumps and motors
The normal pumps and motors are positive displacement
devices and will operate at pressures up to 2,000 lb/in2
(140 kg/cm2). Fig 6 to 9 show schematically the following
common devices.
External gear pump, fig 6
Internal gear pump, fig 7
Vane pump with unbalanced rotor, fig 8
Vane pump with balanced rotor, fig 9
Fig 9. Schematic arrangement of balanced type vane pump or
motor
Generally these devices can be used as motors as well as
pumps. Their construction permits them to operate with
a vacuum occasionally without major damage.
The gear pumps and motors are the simplest, having
the least moving parts. However, they are nothydro-
statically balanced, which adds to bearing and tooth
[360]
friction, and decreased efficiency at the higher pressures.
The maximum pressure for good efficiency is about
1,500 lb/in2 (105 kg/cm2). The gear devices generate
noise because of the abrupt displacement of oil where the
gear teeth mesh.
Vane devices, particularly with hydrostatically balanced
pumps and motors, have several advantages, despite the
complications of more moving parts, in that side thrust
is balanced so bearing loads are nominal. In fig 9, fluid
enters through ports in the end covers at <ka" and "b",
and discharges through similar ports at "c" and "d".
Most small devices have the ports connected internally
so that incoming fluid divides equally and then joins after
passing through. A variation of this is shown in fig 10,
which is a two-speed, balanced vane-type motor, with
self contained direction, speed control and cushion
Fig 1L Three drum trawl and seine winch driven by two-speed
motor shown in fig JO
Fig 72. Two drum trawl winch with gypsies for purse seining
Fig JO. Open view of two-speed balanced vane motor with
mounted control valves for series or parallel flow
valves. Referring again to fig 9, at low speed, the fluid
divides and enters ports "a" and "b" simultaneously,
and then rejoins after passing through ports "c" and
"d". At high speed, all fluid enters port "a", leaves
through port "c", re-enters through port "b", and
finally leaves through port "d". This motor accomplishes
in one unit the circuit shown in fig 5e.
Vane pressure on the body is independent of fluid
pressure so that friction and efficiency are nearly con-
stant for a given speed. This feature permits the balanced
rotor vane devices to run efficiently at pressures up to
about 2,000 lb/in2 (140 kg/cm2). Because of the side
thrust of the unbalanced rotor vane devices, their
maximum operating pressure for best efficiency is
limited to about 1,000 lb/in2 (70 kg/cm2).
HYDRAULICS FOR SMALL FISHING BOATS
Typical deck machinery
How hydraulics have been applied to some of the deck
machinery mentioned earlier is illustrated in fig 1 1 to 18.
[361]
Fig 13. Three drum trawl and seine winch with separate long-
line hauler
Fig 1 1 shows a typical trawl winch with three drums,
two for either the trawl warps or purse lines, and a third
for brailing or cargo. In addition, it has two gypsies and a
wildcat for the anchor. This winch is driven by a hydraulic
motor similar to that shown in fig 10.
Fig 12 shows a winch for a smaller boat, typical of the
west coast of North America. This is intended principally
for stern trawling, but can be used for purse seining,
using the two gypsies shown. Fig 13 is a similar winch,
except that it has a third drum and a separately powered
longiine hauler, making it more versatile for a "combina-
tion" boat. Each winch is driven by a single, balanced
and the driven trolling gurdy. A similar arrangement is
on the other side of the boat. The propulsion engine
drives a single pump to supply the motors.
Fig 18 shows a seine skiff that works with the purse
seiner whose winch is shown in fig 14. Note the small
power block.
In developed fisheries, the advantages of hydraulically
powered deck machinery have been utilized down to the
smallest boats, even to seine skiffs with purse seiners. The
devices used generally provide enough pulling power to
enable one man to do the work of several, or allow him
to pull in his fish faster than he can manually.
Fig 14. Purse seine winch
Fig 15. Longiine hauler
vane-type hydraulic motor with roller chain speed reducer.
Fig 14 shows a purse winch, using the two gypsies for
the purse lines or other duties. The piping in the
background is part of the supply, return, and controls
for the winch and for the power block this boat also
carries.
Fig 15 illustrates a longiine hauler and power gypsy
used on many Scandinavian fishing boats. It is driven
by a slow-speed, direct-drive balanced vane motor moun-
ted in the base.
Fig 16 and 17 show two ways of powering a trolling
gurdy. Fig 16 shows a mechanical clutch and drive with
belts and counter shaft from the propulsion engine. The
speed and direction of the gurdy, both port and starboard,
are controlled by the "retired" automotive transmission
on the right. Fig 17 shows a gear-type hydraulic motor
Fig 16. Trolling gurdy driven through automotive transmission
[362]
Hydraulic deck machinery for fisheries of developing
countries
Deck machinery similar to that described above would be
advantageous to fishermen in developing countries. A
gypsy, longline hauler, trolling gurdy, or one of various
net rollers, capable of pulling about 450 Ib (200 kg) at
about 100 ft per minute (0.5 m/sec) would greatly
improve the fishing efficiency, and hydraulic power
offers a convenient driving method.
Fig 17. Trolling gurdy driven hy hydraulic motor
Prime mover
A propulsion engine, even as small as 5 hp could be
used to drive a hydraulic pump. Where no engine has
been installed the labour saving with hydraulic deck
machinery may justify installation of a propulsion
engine, especially if cheap second-hand automotive
engines are available for conversion. An alternative,
where no propulsion engine exists, is a small engine of
about 3 to 5 hp. Single cylinder, air-cooled petrol
engines of this size are available at a cost, in the order of
£35 (S100) in U.S.A.
Fig 18. Purse seine skiff with hydraulic power block
Hydraulic components
A simple open system with operating pressure of about
1,000 lb/in2 (70 kg/cm2) permits the choice of a wide
variety of equipment, pipe and hoses in the power
range up to about the 5 hp. The circuit for such a
system is shown in fig 19. An automotive power steering
unit is ideally suited. It is designed to be belt driven from
an engine power take off, and is complete with its own
oil reservoir, strainer and flow control valve. The
direction control valve can be of a size and quality used
on earth-moving machinery such as road graders and
light bulldozers.
The principal advantage of hydraulic power trans-
mission is that the driven equipment may be remotely
located from the power source. This advantage can be
extended further by having a single hydraulic motor
with control valve and sufficient hose to allow moving
the motor from one fishing device to another as the season
CONTROL VALVE'
-•-., ASSEMBLY MOTOR
FILTER WITH
"BY FKSS "
AUTOMOTIVE POWER STEERING
PUMP UNIT, 5 GPM WITH
BUILT IN RESERVOIR -
STRAINER.FLOW CONTROL
V-BELT DRIV£.
I I ENGINE
Fig /P. Hydraulic circuit for proposed basic power unit
[363]
THREADED
FOR
ATTACHMENT
SPEED REDUCER \
Fig 20. Basic drive assembly
and fishing techniques vary. Fig 20 to 23 illustrate
typical applications that might be used.
Basic drive
The basic drive assembly consists of the hydraulic motor,
a reduction gear with a drive flange and a mounting
bracket. This is shown in fig 20.
The driving flange is the only visible rotating part of
the assembly. Bearing in mind simplicity of construction
pins of sufficient size are fitted in the flange which are
in line with holes to be provided in the attachment
BASIC DRIVE
SUPPORT POST
flange of each fishing device. A bolt is inserted through
the hub of the flange, which, when tightened, will press
the driven flange firmly against the face of the driving
flange. The studs transmit the torque from the driving
flange to the driven flange. The driving flange has a $ -in
(5-mm) recess which fits a pilot in the driven flange in
order to maintain axial alignment. Two clamps, which
form part of the mounting bracket, can be placed over a
3-in (76 mm) pipe post (34 in (84 mm) outside diameter)
either in the vertical or horizontal position and rotated to
suit the needs for the method of fishing pursued.
As the working area on a small vessel is located most
likely aft, the socket support for the pipe post or for a
davit would be placed on either port or starboard. The
hydraulic control valve as well as the terminus for the
hydraulic flexible hoses would be placed in the vicinity
of the socket for accessibility during operation. A suf-
ficient length of hose should be employed to permit
shifting the basic drive assembly into any desired position.
The supporting pipe of the horizontal design could be
turned in the deck socket and positioned in the most
favourable place by pins. It should be placed facing
outboard or inboard for a beam net work or facing fore
Fig 21. Basic drive assembly with gypsy— mounted on vertical
post
Fig 22. Basic drive assembly with longline hauler — mounted
on vertical post
and aft for fishing operation over the stern. A series of
holes should be drilled in the pipe to suit the various
possible positions.
A design of this type limits the line pull to 450 Ib (200
kg). Nevertheless this gear has power available to replace
several men under normal operational requirements.
Typical applications :
• Power gypsy, in fig 21
• Longline hauler, fig 22
Consisting of two parts: the rope-winding pulley
and a fairleader pulley. The entire assembly can be
rotated to any position to suit the immediate
requirements
• Net sheave, fig 23
The design permits the net to be placed over the
sheave if clamped to a davit, as illustrated in fig 23.
If centreline suspension of the net sheave is
desired, a simple yoke can be provided above the
assembly
• Net reel. Power supply to a net reel on a gillnctter
can be accomplished by the installation of a basic
drive assembly with a roller chain drive to reduce
the speed of the net reel to acceptable limits. The
high-speed sprocket would bolt to the driving
flange in the same manner as other devices
The estimated cost of a basic drive assembly, as shown in
fig 20, and the hydraulic components with 100 ft (30 m)
of hose and end fittings, as shown in fig 19, is £215
($600) based on U.S.A. manufacture. The costs of the
various attachments, supports and installation aboard a
boat would be added to this cost.
While the basic drive as described has a high-speed
motor and an industrial type speed reducer, no reason
exists to prevent the use of a lower speed hydraulic motor
with the driving plate mounted directly to its output
shaft. It is important that a standard driving flange and a
standard mounting bracket be adopted so that manu-
facturers throughout the world could build the basic
Fig 23. Basic drive assembly with net sheave — mounted on davit
drive assemblies, and the various attachments, with
assurance that the assemblies would fit.
Acknowledgments
The authors thank the following sources for the illustrations and
photographs as listed below:
Machine Design, Fluid Power, Reference Issue, Dec. 12, 1963,
chapter 4. "Pump selection" by C. J. Hohman and A. O. Roberts,
Jr: Fig 2, 3, 6,7, 8 and 9.
A. S. Bergens Mekaniske Verksteder, Bergen, Norway: Fig 10,
11 and 15.
J. Swann (1963) Ltd, Vancouver, B.C. Canada: Fig 12 and 13.
[365]
STANDARD GRAPHICAL SYMBOLS
(from ASA-732,10)
Basic symbols can be combined
in any form desired. No attempt
is made to show all combinations.
LINES AND LINE FUNCTIONS
LINE, WORKING
LINE. PILOT (L>20W)
LINE, DRAIN (L<5W)
_...._
CONNECTOR
(DOT TO BE 5X
WIDTH OF LINES)
•
LINE. FLEXIBLE
W
LINE, JOINING
1
LINE, PASSING
-4~
DIRECTON OF FLOW
LINE TO RESERVOIR
ABOVE FLUID LEVEL
BELOW FLUID LEVEL
"1
LINE TO VENTED
MANIFOLD
-3
tii
PLUG OR PLUGGED
CONNECTION
X
TESTING STATION
(GAGE CONNECTION)
— *
POWER TAKEOFF (HYD.)
— -#
RESTRICTION, FIXED
^
X-N
RESTRICTION, VARIABLE
v£/
x*-N
PUMPS
PUMP, SINGLE,
FIXED DISPLACEMENT
[*fl
PUMP, SINGLE,
VARIABLE, DISPLACEMENT
v*y
MOTORS AND CYLINDERS
MOTOR. ROTARY,
FIXED DISPLACEMENT
C*Fj
MOTOR. ROTARY,
VARIABLE DISPLACEMENT
C*K)
MOTOR, OSCILLATING
\ J
CYLINDER, SINGLE ACTING
CYINDER. DOUBLE ACTING
SINGLE END ROD
DOUBLE END ROD
1 1
|
1
|
I
MISCELLANEOUS UNITS
ROTATING SHAFT
(ARROW IN FRONT OF SHAFT)
4-
COMPONENT ENCLOSURE
• 1
• I
RESERVOIR
I |
PRESSURE GAGE
®
OTHER
• Insart appropriate Itttt r combinations
and add appropriate symbols to Indi-
**•*. •!«•***««» j*jinn.*fitim flnur lln**
cata snans or connscnni now urtvi.
ACC ACCUMULATOR
ELEC MOT ELECTRIC MOTOR
ENG ENGINE
FLT FILTER
FM FLOW METER
HE HEAT EXCHANGER
INT INTEN8IFIER
PS PRESSURE SWITCH
STR STRAINER
TACH TACHOMETER
[366]
VALVES AND BASIC SYMBOLS
VALVE, CHECK
— <) —
VALVE, MANUAL SHUTOFF
— s —
VALVE, MAXIMUM
PRESSURE (RELIEF)
-gr
VALVE, BASIC SYMBOL
SINGLE FLOW PATH IS
MODIFIED.
n
VALVE, BASIC SYMBOL
MULTIPLE FLOW PATHS
ARE CHANGED
MM
VALVE, SINGLE FLOW
PATH, NORMALLY CLOSED
*
VALVE, SINGLE FLOW
PATH, NORMALLY OPEN
$
VALVE, MULTIPLE FLOW
PATHS, BLOCKED
1 1
1 t} 1
TT
VALVE, MULTIPLE FLOW
PATHS, OPEN
(ARROWS DENOTE DIREC-
TION OF FLOW)
ij
n$
M
VALVE. SPECIAL
(IDENTIFY AND CONNECT
ALL LINES)
1 1
VALVE EXAMPLES
VALVE. RELIEF
REMOTELY OPERATED
(UNLOADING VALVE)
— dp>
VALVE. DECELERATION
NORMALLY OPEN
f*fcwfT"|vy
VALVE. SEQUENCE.
DIRECTLY OPERATED
n*?*
iMi
VALVE. PRESSURE
REDUCING
ffi?*
Lbffl
VALVE EXAMPLES (CONT.)
VALVE, COUNTERBALANCE
WITH INTEGRAL CHECK
VALVE, FLOW-RATE
CONTROL, VARIABLE,
PRESSURE COMPENSATED
VALVE, DIRECTIONAL,
2 POSITION
3 CONNECTION
VALVE, DIRECTIONAL,
3 POSITION
4 CONNECTION
OPEN CENTER
VALVE, DIRECTIONAL,
3 POSITION
4 CONNECTION
CLOSED CENTER
METHODS OF CONTROL
SPRING
PILOT OPERATED
PILOT OPERATED,
DIFFERENTIAL AREA
OTHER
* Insert appropriate letter combinations
and add connecting flow lines.
CENT
COMP
CYL
DET
ELEC MOT
HYD MOT
MAN
MECH
SERV
SOL
SOL PLT
THRM
CENTRIFUGAL
COMPENSATOR
CYLINDER
DETENT
ELECTRIC MOTOR
HYDRAULIC MOTOR
MANUAL
MECHANICAL
SERVO
SOLENOID
SOLENOID CONTROLLED,
PILOT OPERATED
THERMAL
[367]
SAMPLE COMPOSITE SYMBOLS
PUMP, DOUBLE, WITH ELECTRIC MOTOR
ONE FIXED DISPLACEMENT
ONE VARIABLE DISPLACEMENT WITH
COMPENSATOR CONTROL
PUMP, DOUBLE, WITH IN-BUILT CHECK,
RELIEF AND UNLOADING VALVES.
VALVE, PRESSURE COMPENSATED VARIABLE
FLOW-RATE CONTROL WITH
MAXIMUM PRESSURE CONTROL
VALVE, RELIEF AND REPLENISHING
VALVE, 4-WAY, MANUALLY CONTROLLED,
SPRING CENTERED.
(PORTING AT CENTER IS P TO T
WITH CYLINDER PORTS BLOCKED)
SIMPLIFIED
SYMBOL
VALVE, 4-WAY
SOLENOID CONTROLLED,
PILOT OPERATED.
SPRING OFFSET
COMPOUND
SYMBOL
\ I ^^TFT^^^^MB I
VALVE, 4-WAY, SOLENOID CONTROLLED,
PILOT OPERATED, NO SPRING
(ONE PORT PLUGGED)
I_LJ
[368]
Refrigeration Facilities in Small
Fishing Boats
by Seigoro Chigusa
Installations de refrigeration a bord des petite bateaux
L'auteur fait un bref historique do Involution des petits bailments
de pdche japonais, en exposant les facteurs 6conomiques ayant
joud dans 1'adoption d'installations modernes de refrigeration. II
passe en revue les installations et mdthodes d'entreposage frigorifiquc
pour des batiments d'une jauge brute allant de 20 a 100 tonneaux.
On etudie plus particulidrement rinfluence, sur les besoins en
matiere d'installations frigorifiques, des facteurs suivants: duree
des sorties, volume des captures et especes pechees (et, partant,
capacite des cales a poisson), temperature d'entreposage n6cessaire
a une bonne conservation, types desolations, utilisation en alter-
nance des cales pour Ic poisson et pour le mazout, materiel frigo-
rifique et fluides frigorigfcnes, et automatisation integrate du
dispositif de congelation. En fin, des tableaux et illustrations sont
consacres a requipement frigorifiquc ct a I'agencement des cales de
navires de divers ddplaccments.
La refrigeracidn en las pequenas embarcaciones
Sc hace un breve hislorial de las pequeftas embarcaciones pesqueras
japonesas, con la explicaci6n de los factores econbmicos que
intervienen en la instalaci6n de frigorificos modernos. Se analizan
instalaciones y metodos adecuados de almacenamiento para barcos
de 20 a 100 toneladas brutas, haci6ndose referenda a los efectos
resultantes de los siguientes factores: travesia, tallas y especies
capturadas (y, en consecuencia, la capacidad de las bodegas de
pescado), temperatura para una buena conservaci6n, tipos de
aislamientos, utilizacion de las bodegas alternativamente para
pescado y carburante, frigorificos y refrigcrantes y sistemas de
almacenamiento totalmentc automAticos. For ultimo se exponen
grabados de instalaciones generates de rcfrigeraci6n de bodegas y
sus diversas disposiciones para barcos de distintos desplazamientos.
THE first refrigerating facilities in Japanese
fishing boats were installed on Yuryo Maru, a fish
carrier, in 1907. Since then, Japan has gained
valuable experience in the installation.
In pre-war days, Japanese fisheries mostly operated
in the coastal waters of the islands, with the exception of
Northern Pacific fishing or whaling expeditions. There
was no pelagic fishing, which requires longer voyages,
and so the refrigerators installed in fishing boats were
not fully utilized, and some of them were even removed.
After World War IT, Japanese fisheries were extended
from the exhausted coastal waters to offshore or pelagic
waters to secure marine sources of protein and to
stabilize the nation's nutrition. According to the ex-
pansion of fishing grounds and the increase in operating
periods, refrigerators have become essential.
The modern Japanese refrigerated fishing fleet needed
steady progress in techniques and national economic
support to be developed.
This paper describes refrigerators installed in vessels
of 20 GT to 100 GT, and furnishes information about
their design and construction for possible use in other
countries.
TYPES OF STORAGE
In general, for maintaining freshness offish catch aboard,
the following three methods are used :
(1) Storage with ice (refrigerators may be used in
addition)
(2) Storage in chilled sea water (chilled sea water is
produced by means of ice or refrigerator)
(3) Storage in frozen condition by means of refrigerator
Method 1 and Method 2 have been used from pre-
refrigeration days and, depending on operating periods,
species of fish and location of fishing grounds, do not
necessarily need refrigerators. It is to be noted that there
are limits on storing temperature and volume of ice to be
taken aboard.
Initially, if with the introduction of refrigeration no
ice was used in Method 1, it was not satisfactory and the
freshness of the fish deteriorated. Nowadays, it is
generally agreed that in the case of Method 2, even if
refrigerators are used, a minimum amount of 60-70 per
cent of the ice necessary for cooling without a refrigerator
is necessary. The reason is that inadequate circulation
of cold air in the fish holds does not achieve uniform
cooling of fish near the cooling pipes and centre of the
holds, and also ice performs the following functions
which are essential for securing freshness:
• Pre-cooling of fish
• Washing by melted ice
• Acting as pads between fish in holds
• Uniform temperature of individual fish
When it is difficult to obtain ample ice, Method 2 by
means of a refrigerator or Method 3 must be adopted.
Table 1 shows in brief the methods of storage of fish
and the limit of storing days.
Generally speaking, the two methods without re-
frigerator in table 1 are applied to popular commercial
fish, such as mackerel-pike, mackerel and cod, so that
more hold space can be occupied by actual fish and the
methods with refrigerator are applied to high grade fish
such as prawn and tuna.
[369]
TABLE 1
Method of storing Limit of storing days
Method Refrigerator
(1) Storage with ice
(2) Storage in chilled sea
water
without
with
without
„ with
(3) Storage in frozen condi-
tion by means of
refrigerator with
40
60
30
40
over 60
30
40
20
30
over 40
Table 2 shows that even small vessels use refrigerators
according to the length of a trip and methods of storage.
Tuna catchers of about 20 GT engaged in mother-ship
operations make daily trips. As the supply of ice from
the mother-ship is not usually sufficient, the catchers use
Method 2 by means of a refrigerator, or Method 3. Such
methods of storage for day trips may not seem necessary
but they were important for pre-cooling fish before
transferring it to the mother-ship.
TABLE 2
Kind of boat SL'e(^""
Fish catch Operating
per trip period
(tons) (days)
Storing method
refrigeration plus
Tuna long-
liner
»»
20
40-50
95-100
one day
30-35 30-40
60-75 50-70
ice or only re-
frigeration
ice
ice or only re-
frigeration
Two-boat
trawler
90
30-40 20-30
ice
As shown in table 2, tuna longliners of 40 to 50 GT
and two-boat trawlers of about 90 GT are using Method 1
because of their limited operating period of 30 to 40 days
but bigger tuna boats, 95 to 110 GT, are obliged to use
Method 3 because of their 50 to 70 days operating period.
It is the general trend in Japan to use more refrigerators
on small vessels. In fact, Method 1 was preferred in the
past because it allowed more space in the fish hold and
also the product had a better market price but nowadays,
because of the improvement in storing techniques and
longer trips, refrigerators are becoming more and more
popular.
STORING CAPACITY BY TYPE OF STORAGE
The fish catch storable per unit volume of fish hold
varies greatly with species of fish and storage method.
Method 2 gives a storage ratio of 47 to 50 lb/ft3 (750 to
800 kg/m3) and is popular for mackerel and mackerel-
pike. Method 1 for tuna can feasibly store 32 to 37
lb/ft3 (520 to 600 kg/m3), and Method 3 26 to 32 lb/ft3
(420 to 520 kg/m3) in bulk, respectively. Regarding two-
boat trawlers in which fish is packed with ice in boxes
and also refrigerated, the storing capacity is only 22 to 28
lb/ft3 (360 to 450 kg/m3).
In Method 3 the enlarged engine room space, because
of the enlargement of the freezing chamber or related
facilities, reduces the capacity of fish holds. When the
fish hold is sub-divided into compartments the original
capacity will be slightly more reduced. However, if other
methods are adopted, the freshness of the fish is greatly
affected because of the length of the trip.
DAY'S CATCH, SIZE OF COMPARTMENT
AND CAPACITY OF REFRIGERATOR
The catch of a small tuna boat or two-boat trawler is
approximately 2 to 5 tons per day. Hence, the ideal
capacity of the hold should be 700 to 1,000 ft3 (20 to
30 m3) (10 to 15 tons) which should be filled in 5 to 6
days; a multi-compartment hold reduces the total amount
of fish stored and should be avoided as far as possible.
The size of the compartment for Method 1 should be
decided by taking account of the following:
• When the capacity of the compartment is large it
takes a long time to fill and requires frequent
opening which causes oscillations in temperature
• Poor cool-air circulation makes it difficult to
maintain the freshness of the catch at the com-
partment's centre
In the case of Method 1 , therefore, it is essential to
place cooling pipes adjacent to the movable partitioning
boards at the centre of the compartment. Method 3 is
not yet popular among small vessels and it is only installed
in a few vessels of 99 GT. Aiming to lower the centre of
gravity of the hull, these vessels have working rooms on
the upper deck under the bridge deck, preparation rooms
below the working rooms and one or two freezing
chambers on both sides of the preparation rooms.
STORING TEMPERATURE AND OPERATING
PERIOD
The temperature of Method 1 without refrigerator is
32°F (0°C) for fish in contact with ice, and 37.5 to 50°F
(3 to 10°C) elsewhere. When refrigeration is used the
temperature can be lowered but care should be taken
that the fish are not frozen. The storing temperature of
fish by Method 3 is generally 0°F (~18°C), up to an
operating period of a month, —4 to — 9.5°F (—20 to
~-23°C) for 2 to 3 months, -13 to -18.5°F (-25 to
-28°C) for 3 to 5 months, and -~20°F (-29°C) and
below for more than 6 months. Table 3 shows the storing
temperature of fish in small fishing boats.
TABLE 3
Kind of boat
Size of boat
(GT)
Storage
time by days
Storing
method
Storage
temperature
Tuna boat
40-50
30-40
(1)
0 to - 1°C
(32 to 30°F)
••
95-110
50-70
(3)
-20 to -23°C
(~4to-9.S°F)
Two-boat
trawler
90
20-30
(1)
+ 3 to 0°C
(37.5 to 32°F)
[370]
It shows that the storing temperature offish by Method
3 in tuna boats less than 100 GT is —4 to — 9.5°F
(—20 to — 23°C); this is due to their operating period of
about two months but the storing temperature of
larger tuna boats over 200 GT is —22 to — 29°F (-30
to — 34°C). With such low temperatures fish can main-
tain good quality after de-freezing, and the product is
equally well accepted as the product of Method 1 .
SPECIAL CARE FOR REFRIGERATORS USED
FOR BOTH METHODS
Refrigerators used for Method 3 need to have a very large
capacity compared with those used for Method 1 to
freeze the fish rapidly and maintain the temperature in
fish holds as low as possible. When the refrigerating
machinery is used for Method 3 only, there will be no
difficulties but if the same machinery is used for Method 1
either at the same time or alternatively the fish will
sometimes be over-frozen and the quality reduced.
The following arc preventive measures against such
situations:
• Control of refrigerating machinery capacity
When a compressor for Method 3 is used for
Method 1, its capacity must be reduced by an
unloading device.
• Control of evaporating temperature by pressure
regulator
When a compressor capacity is too big or one
compressor has to maintain two different tem-
peratures, for Method 3 and Method 1, the suction
pressure of the compressor must be lowered by the
regulator as the evaporating temperature is
proportional to the suction pressure and big
differences between the temperature of the cooling
pipes (evaporating temperature) and of the fish
holds must be avoided, otherwise the fish placed
near cooling pipes will be over-cooled, and slow
freezing will begin.
• Insulation of bulkhead between fish holds for
Method 3 and Method ]
When one of two adjoining fish holds is used for
Method 3 and the other one for Method 1, the
quality of fish in the hold for Method 1 may be
seriously damaged because of over-cooling or
slow freezing by the effect of the low temperature
of the hold for Method 3. Insulation of the com-
mon bulkhead has to be very efficient.
• Piping arrangement
In general, over-cooling of fish holds is not a
problem for Method 3 and it is natural that when
the highest temperature in the holds is lowered to
the required degree the temperatures around the
cooling pipes will drop by 5£ to 7°F (3 to 4°C).
This drop in the temperature must definitely be
avoided for Method 1 because partial over-cooling
or slow-freezing is not permissible for this method.
The piping which is used for both Method 1 and
Method 3 must be arranged having the correct
pitch on the ceiling, wall and bottom of fish holds
and be divided into suitable arrangements in
order to make the hold temperature as uniform
as possible.
CAPACITY OF REFRIGERATOR AND
INSULATION
Initially carbonized cork boards were used for insulation
but were not popular because of the danger of rotting
in wooden boats and a reduction in hold capacity in steel
boats. Furthermore, when refrigerating apparatus was
initially installed, grid coils and their sparring were
thought to be a substitute for cork insulation boards
and the number of boards was reduced. This was not
found to be practical.
TABLL 4
Location
Method \
Method 3
2 to 2 C
-18 to 23 C
-25 to 30' C
(28.3 to 35.6 F)
<0to 9.5' F)
( 13 to -22' F)
in
in
in
(mm)
(mm)
(mm)
Ceiling
3.9
5.8
7.8
(100)
(150)
(200)
Side wall
3.9
5.8
6.8
(100)
(150)
(175)
Bottom
1,9 2.9
3.9-4.9
5.8
(50-75)
(100 125)
(J50)
fForc
3.9
5.8
6.8
i
(100)
(150)
(175)
Eng.
3.9 5.8
6.8-7.8
7.8 8.8
Bulkhead
Room
(100-150)
(175 200)
(200-225)
Inter
1.9
2.9-3.9
3,9-4.9
hold
(50)
(75 KM))
(100 125)
Note: Insulation materials are foamed plastic.
Regarding the cooling pipes installed in wooden
boats, there was a fear that the deflection of the wooden
hull might produce breaks in the pipes but this was
overcome by good piping arrangements and practically
no faults occurred.
The insulation thickness of existing fishing boats is
shown in table 4.
The refrigeration capacity is usually designed on the
assumption that the refrigerator operates for about 12 to
18 hours per day under the temperature conditions shown
in table 4. The values in table 5 are actually used con-
sidering such factors as heat gain by the frequent opening
of the hatches, and use of pre-cooling before refrigerating.
TABLL 5
Kind of bout
Two-boat trawler
Tuna boat
Size of boat
GT
Kind of
storage
Capacity and
number of
refrigerator
90
Method 1
2 to 3 RT x 1 set
39-47
>»
3 to 5 „ x 1 set
96-99
»»
5 to 9 „ x 1 set
99-111
Method 3
13 to 17,, x2set*
20
Method 2
2 to 3 „ x 1 set
Note: * includes one set for freezing.
[371]
HOLDS ALTERNATIVELY USED FOR FISH THEN
FUEL OIL
Fishing boats now require more fuel oil aboard than
previously with the expansion of fishing grounds and
longer total voyage time but when their constructed oil
tanks are enlarged, their fish-hold capacity must be
reduced. Formerly, fuel oil was taken in drums or vinyl
tanks in the fish hold on the outward voyage but now it is
taken into the hold itself and fish carried back in it.
This eliminates overcoming unexpected difficulties,
damage of vinyl tanks, etc. After the fuel oil is consumed,
the fish holds are cleaned to receive the fish. The wooden
ceiling plank in fish holds was often made oiltight for
storing fuel oil but it was rather difficult to prevent
oil from permeating the insulation boards. Plastic
structure and resin paint are now successfully used in
some tanks for this purpose.
Nowadays most fishing boats have a watertight metal
ceiling (steel or aluminium alloy) on which the cooling
piping is arranged. This metal ceiling, however, pre-
viously caused an enormous heat gain due to its direct
connection with the frames through metal supports,
i.e. angle bars, but this is now eliminated as insulated
materials are used as supports, etc.
ARRANGEMENT IN ENGINE ROOM
It is essential that the engine room space should be
minimized for maximum fish-hold capacity. To this end
small fishing boats less than 50 GT are provided with no
generators or electric motors and their main engines are
used as a direct power source for all necessary equipment,
while larger fishing boats of 100 GT have been provided
with AC motors or hydraulic motors.
From fish holds
Suction header and
heat exchanger
a a
K>
, i Dryer and
fi strainer
Liquid header
J. .-Receiver . $
\ 1 -J
Pressure switch «-U Cooling water pump
• ID
2>X
Fig L R-12 piping diagram
Accumulator
From fish holds
Compressor
-4— .Cooling water pump
Fig 2. Ammonia piping diagram for storage hy crushed ice
Refrigerating facilities are fitted forward in the engine
room or on the upper deck, and the expansion valve
panel and the suction header, etc., on the fore bulkhead
of the engine room, the condenser at the top of the port
or starboard side, and the receiver (horizontal or vertical
type) underneath the condenser. Since these items are
cramped in small fishing boats, every precaution must be
taken against dangers by, say, automation or non-
manual control using compact units.
REFRIGERANTS
The refrigerant used is mostly ammonia, Fron accounting
for only 20 per cent. Ammonia is mainly used because of
the following:
(a) Low cost
(b) Higher efficiency in high-capacity refrigerating
facilities
(c) Gas leaks easily found
F3731
(b) above indicates that ammonia is best for flooded
systems or refrigerant recurrence systems used in re-
frigerating facilities of large capacity. Fron is colourless
and odourless, which causes difficulty in locating a leak
until, arrival at fishing grounds. Fron refrigerants have
the advantage in small fishing boats or school boats in
respect of safety, easy automation and compactness and
weight of units and therefore small boats using Method 1
will more frequently have Fron refrigerants.
Compressors of a reciprocating type with a range of
rpm from 400 to 1,400 and compressors of a rotary
type can be used for both ammonia and Fron. The
condenser in most cases is of horizontal shell and tube
type which has solid-drawn steel tubes (galvanized on the
surface in contact with water) for ammonia and albrac
or Low-fin tubes for Fron for good durability and
reduction of weight and compactness.
Recently, to reduce engine-room space, a square-type
:ondenser was manufactured and installed on the upper
deck.
AUTOMATION SYSTEM
Most refrigerating facilities previously installed were
manually controlled and ineffective. The thermometers
in a hold did not necessarily indicate the correct tem-
peratures in all parts of the hold. So in Method 1 the
temperature was controlled by checking the volume and
temperature of the bilge. At first it is difficult to obtain
correct temperature adjustment for good preservation
and only experience solves this, but this difficulty would
be eliminated by automatic control. Automation of
refrigerating facilities commenced with an automatic
expansion valve for facilities using Fron, and later high-
speed multi-cylinder compressors, also safe or protective
equipment such as the dual pressure switch (DPS), oil
protection switch (OPS), water pressure switch (WPS).
Now automatic expansion valves and evaporating
pressure regulators (EPR) have been adopted for
ammonia facilities. Fully automatic R-12-type refrigerat-
ing facilities (non-manual) having all essential equipment,
Multi suction trap
Accumulator
Multi suction trap
Cl C!
Pressure Switches
Cooling water pump
Fig 3. Ammonia piping diagram for freezing
i.e. thermostat and magnetic valve, DPS, OPS and EPR,
are being contemplated for use in two-boat trawlers.
Automatic control of facilities will eliminate over-cooling
around the cooling pipe and slow freezing in Method 1.
Fishing operations and treatment of fish always
required considerable manpower, and labour saving
aboard has recently come under consideration due to the
difficulty of obtaining fishermen. Many labour-saving
methods, like the adoption of conveyor belt systems
in the process of freezing, are being utilized.
General arrangement plans of refrigerating facilities
are shown in fig 1, 2 and 3.
SPECIFICATIONS OF REFRIGERATING PLANTS
Typical examples of refrigerating plants for Japanese
fishing vessels of 20 to 100 GT are shown as follows:
1. 20-GT tuna catcher (Method 2)
Lpp 5 1.1 8 to 52.50 ft (15.60 to 16.0 m)
B 11.48 „ 12.14 ft ( 3.50 „ 3.70m)
T, 4.72 „ 5.25 ft ( 1.44 „ 1.60m)
GT 19 to 20 tons
Speed about 9 knots
Fish-hold capacity 353 to 495 ft3 (10 to 14 m3) (2
subdivisions)
Storing t 0°C (32°F)
NH3 compressor Reciprocative Type
3.27 in diam x 0.276 in L x2 cylinders x 450 rpm x 3 1,620
BTU/hrx5 hpxl set (83 mm diam x 70 mm Lx2
cylinders x 450 rpm x 7,968 kg cal/hrx5 hpxl set)
Rotary Type
NRL— 5 x 1 ,300 rpm x 4, 1 60 BTU/hr x 5 hp x 1 set
(NRL— 5 x 1,300 rpm x 10,624 kg cal/hr x 5 hp x Iset)
NH3 condenser 14.96 in diam x 34.25 in L x 35.52 ft2 to
14.96 in diam x 47.24 in Lx 49.51 ftaxl set
(380 mm diam x 870 mm L x 3.30 m2 to 380 mm diam
x 1,200 mm L X4.60 m2 x 1 set)
Cooling water pump 176.6 cu ft/hrx29.5 ft h to 247.2
cuft/hrx 26.20 ft h
(5 m3/hrx9 m h to 7 ma/hrx8 m h)
NH3 receiver 10.5 in diam x 3 1.5 in Lx55.12 Ib to
12,52 in diam x 33.46 in Lx77.16 Ibxl set
(267 mm diam x 800 mm L x 25 kg to 31 8 mm diam x
850 mm Lx35 kgx 1 set)
Oil separator 6.50 in diam x 17.72 in h to 8.50 in diam x
24.80 in h x 1 set
(165 mm diam x450 mm h to 216 mm diam x 630 mm
h x 1 set)
Liquid separator 6.50 in diam 17.72 in h x 1 set
(165 mm diam x450 mm h x 1 set)
no.3 hold no.l hold
no 4 hold no.2 hold
Fig 4. General arrangement of tuna hngliner 39 GT
[375]
Cooler, Shell and tube type: 12.52 in diamx 39.37 in
Lx40.90ft2xl set
(318 mm diam x 1,000 mm L X3.80 m2 x 1 set)
L-shape section coil type: 1.34 in diamx 72 1.8 ft
951. 4 ft (2 series)
(34 mm diam x 220 m to 290 m (2 series)
Circular pump 459.1 ft3/hrx 32.81 ft h to 706.3 ft3/hrx
65.62 ft h x 1 set
(13 m3/hrx 10 m h to 20 m3/hrx20 m hxl set)
2. 40 to 50-GT tuna longliner (Method 1), fig 4
Lpp 64.90 to 65.30 ft (19.78 to 19.90 m)
B 14.40 „ 15.09 ft ( 4.39 „ 4.60m)
Tj 6.69 ., 6.90 ft ( 2.04 „ 2.10m)
GT 39 to 47 tons
hp 180 to 250
Speed about 8 knots
Fish-hold capacity 1413 to 1765 ft3 (40 to 50 m3)
(6 subdivisions)
Storing t 0 to -2°C (32 to 28.4°F)
NH3 compressor 3.50 in diam x 3.50 in L x 2 cylinders x
400rpmx41,500BTU/hrx7.5hpx! set
(89 mm diam x 89 mm L x 2 cylinders x
400 rpm x 10,458 kg cal/hr x 7.5 hp X 1
set)
or 3.94 in diam x 3.00 in L x 2 cylinders X
600 rpm x 67,850 BTU/hr X 10.0 hp x 1
set
(100 mm diam x 76 mm Lx2 cylinders
x600 r.p.m.x 17,098 kg cal/hr x 10.0
hp x 1 set)
NH3 condenser 14.96 in diamx 34.25 in Lx35.5 ft2 to
14.96 in diamx 59.06 in diamx 61. 9
ft2 x 1 set
(380 mm diamx 870 mm Lx3.3 m2 to
380 mm diamx 1,500 mm Lx5.75 m2
x 1 set)
Cooling water pump 247.2 ft3/hr x42 ft h x 1 set
(7m3/hrxl3 mhxl set)
NH3 receiver 18.90 in diamx 27.56 in Lx 147.70 Ibxl
set
(480 mm diam x 700 mm L x 67 kg x 1 set)
Oil separator 8.50 in diam x 23.62 in h x 1 set
(216 mm diam X 600 mm h x 1 set)
Liquid separator 8.50 in diam x 23.62 in h x 1 set
(216 mm diam x 600 mm h x 1 set)
Cooling coil 1.07 in diam x 1,968 ft L (6 series)
(27.2 mm diam x 600 m L) (6 series)
3. 90-GT tuna boat trawler (Method 1)
Lpp 88.58 ft (27.00 m)
B 17.40 ft ( 5.30 m)
T! 8.60 ft ( 2.62 m)
GT 90 tons
hp 340
Speed 9 knots
Fish-hold capacity 2,825 to 3,885 ft3 (80 to 1 10 m3)
(5 subdivisions)
Storing t 0 to + 3°C (32°F to 37.4°F)
R- 12 compressor 2.28 in diamx 1.77 in diamx 3 cylin-
ders x 1 ,500 rpm x 3 1 ,620 BTU/hr
x5 h.p. xl set
(58 mm diam x 45 mm L x 3 cylinders x
1,500 rpm x 7,968 kg cal/hr x 5 hpx
1 set)
or NRL— 5x1,720 rpm x 3 1,620 BTU/
hrx7.5 hpxl set
(NRL— 5x1,720 rpm x 2.4 RTx7.5
hpxl set)
R- 12 condenser 10.51 in diamx29.53 in Lx45.2 ft2Xl
set
(267 mm diam x 750 mm L x4.2 m2 x 1
set)
Cooling water pump 247.2 ft3/hr X42.6 ft h x 1 set
(7m3/hrxl3 mhxl set)
R-12 receiver 10.51 in diam X 47.24 in L x 176.4 Ib x 1 set
(267 mm diamx 1,200 mm Lx80 kgxl
set)
Oil separator 5.91 in diamx 16.14 in h 8.50 in diamx
24.80 in h x 1 set
(150mm diamx410mm h— 216mm diam
x 630 mm hxl set)
Cooling coil 1.34 in diam x 1,968 ft L (5 series)
(34 mm diam x 600 m L (5 series)
4. 95-GT salmon and trout drift-netter (Method 1)
Lpp 86.94 ft (26.50 m)
B 18.70 ft ( 5.70m)
T, 8.53 ft ( 2.60 m)
GT 96 tons
hp 350 to 440
Speed 9 knots
Fish-hold capacity 3,355 to 3,885 ft3 (95 to 1 10 m3)
(5 to 6 subdivisions)
Storing t 0°C (32°F)
NH3 compressor 3.94 in diam x 3.94 in L x 2 cylinders x
400 rpm x 59,288 BTU/hr x 10 hpx
1 set
(100 mm diamx 100 mm Lx2 cylin-
ders x 400 rpm x 14, 940 kg cal/hr
x 10 hpxl set)
NH3 condenser 8.90 in diam x 59.05 in L x 61 .9 ft2 x 1 set
(480 mm diam x 1 ,500 mm L x 5.75 m2 X
1 set)
Cooling-water pump 247.2 ft3hr X42.6 ft h x 1 set
(7m3/hrxl3 mhxl set)
NH3 receiver 13.78 in diam X 70.87 in L x 198.4 Ib x 1 set
(350 mm diamx 1,800 mm Lx90 kgxl
set)
Oil separator 8.50 in diam x 23.62 in h x 1 set
(216 mm diam x 600 mm h x 1 set)
Liquid separator 8.50 in diam x 23.62 in h x 1 set
(216 mm diam X 600 mm h x 1 set)
Cooling coil 1.34 in diamx 3,280 to 3,937 ft L (10-12
series) 34 mm diamx 1,000 to 1,200 m L
(10-12 series)
[376]
no.5 hold no3 hold
hold
no.4 hold
Fig 5. General arrangement of tuna longliner 99 CT
no.2 hold
5. 100-GT tuna longliner (Method 1), fig 5
Lpp 88.58 ft (27.00 m)
B 19.03 ft ( 5.80 m)
T! 8.69 ft ( 2.65 m)
GT 99
hp 350 to 430
Speed 9 knots
Fish-hold capacity 3,531 to 4,591 ft3 (100 to 130 m3)
(5 to 6 subdivisions)
NH3 compressor 5.0 in diamx4.02 in Lx2 cylinders x
500 rpmx 118,575 BTU/hrx20 hpx
1 set
(127 mm diam x 102 mm L x2 cylinders
X500 rpmx 29,880 kg cal/hrx20 hp
x 1 set)
NH3 condenser 22.44 in diam x 59.06 in L X98.0 ft2 x 1
set
(570mm diam x 1,500 mm Lx9.1 m2xl
set)
Cooling water pump 459 ft3/hrx45.9 ft h
(13m3/hrxl4m hxl set)
NH3 receiver 1 8.80 in diam x 43.3 1 in L x 23 1 .5 Ib x 1 set
(480 mm diam x 1,100 mm Lxl05 kgxl
set)
Oil separator 8.50 in diam x 23.62 in h x 1 set
(216 mm diam x 600 mm h x 1 set)
[377
Liquid separator 10.51 in diamx29.53 in hxl set
(267 mm diam x 750 mm h x 1 set)
Cooling coil 1 .34 in diam x 3,937 to 4,265 ft L (8-9 series)
(25 mm diam x 1,200 to 1,300 m L (8-9
series)
6. 100-GT tuna longliner (Method 3),rfig 6
Lpp 89.80 ft (27.37 m)
B 2 1.65 ft ( 6.00m)
T! 8.86 ft ( 2.70 m)
GT 99 to 1 1 1
hp 400 to 450
Speed 9 knots
Fish-hold capacity 3,002 to 3,178 ft3 (85 to 90 m3)
(1 to 4 subdivisions)
Freezing capacity 2 to 4 tons/24 hr (2 rooms)
Storing t fish-hold -20 to -23°C (-4 to - 9.4°F)
freezing -30°C (-22°F)
NH3 compressor 3.74 in diam x 3.00 in L x4 cylinders x
1 , 1 50 rpm x 23 1 ,880 BTU/hr x 30 hp X
2 sets
(95 mm diam x 76 mm Lx4 cylinders
x 1 , 1 50 rpm x 58,430 kg cal/hr x 30 hp
x2 sets)
NH3 condenser 26.0 in diamx94.50 m Lx230.3 ft2xl
set
(660 mm diam x 2,400 mm L x 2 1 .4 m2 x
set)
Working room
Freezing room no3 hold no.l hold
no.4 hold no.2 hold
Fig 6. General arrangement of tuna hmgliner III GT
Cooling water pump 1,059 ft3/hr X42.7 ft h x 1 set
(30m3/hrxl3 m hxl set)
NH3 receiver 23.6 in diam x 86.6 in L x 77 1 .6 Ib x 1 set
(600 mm diam x 2,200 mm L x 350 kg x 1
set)
Oil separator 12.5 in diam x 35.4 in h x 1 set
(318 mm diam x900 mm h x 1 set)
Liquid separator for fish hold 12.5 in diam x 35.4 in h x 1
set
(318 mm diamx900 mm
h x 1 set)
for freezing 8.5 in diam x 70.1 in h x2
sets
(216 mm diam x 1,780mm
hx2 sets)
Cooling coil for fish hold 1.68 in diam x 1,968 ft L
(5 series)
(42.7 mm diam x600 m L
(5 series)
for freezing 1 .68 in diam x 2,624.6 ft L
(4 series)
(42.7 mm diam x 800 m L
(4 series)
[378]
UlSCUSSlOlK The application of contemporary
engineering techniques to fishing craft
MECHANIZING INDIGENOUS CRAFT
H0gsgaard (Denmark): Denmark began mechanization by
using four-stroke hot bulb engines while in Sweden two-stroke
hot bulb engines were adopted. Sweden made the better choice,
so when larger sizes came into use, the Danes changed to the
Swedish system. The Swedes used water injection. It is very
important that engines can run a long time at low speeds. The
combustion chamber is usually made in two halves like a ball.
The Swedes used injection at the top of the combustion
chamber. The injection on full-power was direct and concen-
trated. At low speeds, fuel is sprayed to the sides of the bulb.
In Denmark the atomizer is installed on the side and this gives
excellent results.
Borgenstam has given an excellent paper, but H0gsgaard
did not recommend blow-lamps. Sulphur cartridges should be
used instead for starting. H0gsgaard would like to add that
low-compression engines are not necessarily dirty. He con-
sidered that in Denmark they had arrived at an excellent result
with their low-pressure oil engines. This is the most uncom-
plicated engine type ever manufactured and is very useful in
countries where not sufficient trained people are available.
Developments in India
Gnanadoss (India): K varan had observed that competition
from completely new mechanized boat types had tended to
slow down the process of mechanization of existing craft. This
is not to be taken as a general feature. In India, mechanization
of fishing craft started with indigenous fishing craft after
World War 11, and modern, well-designed boats were intro-
duced about ten years later. Today they have nearly 4,000
indigenous fishing boats mechanized in India and more and
more existing craft are being mechanized every year.
These craft are well advanced from the point of view of
design, and also well adapted for the type of fishing they are
engaged in. Most important of all, they could so easily take
an inboard engine to provide the motive power which is in
fact the only aid the fisherman needs for his method of fishing.
The low building costs of these existing craft also contribute
a good deal to this development. Therefore, it follows that
mechanization of existing craft is not a preliminary step to
favour development, as Kvaran has put it, but is the final step
itself —as far as these boats and the fishing they are meant to
exploit are concerned. It should, however, be stressed, that
these boats are essentially inshore fishing boats.
The real problem in India is the matter of proper powering
of these boats. In most cases, these boats have been con-
siderably overpowered. The psychology of the fisherman
being the same the world over, whenever the fisherman has
the choice of the engine, he tries to install an engine which is
more powerful than what his friend's boat has — to satisfy his
pride and to get that imaginary extra knot — which he seldom
does. This psychology has, to some extent, been taken advan-
tage of by some engine salesmen, which of course has not done
much good to the fishermen.
One of the disheartening aspects of mechanization in India
is the after-sales service by the engine supplier. In many
instances, such a facility does not exist at all, and even if it
does, the benefit of such service is meant to go more to the
engine supplier himself than to the fishermen.
It is needless to emphasize that the service mechanic should
be a person who can identify himself completely with the
fisherman, go out to sea with him and share his experiences
in full. There have been instances of service mechanics who
could not even withstand the motion of boats while in the
harbour and have demanded that the boat be put on hard
ground if the engine has to be attended to.
Although hundreds of engines of four or five different
makes have been sold in India, Gnanadoss had yet to come
across any one engine supplier who attempted to come closer
to the fisherman by providing him with a simple instruction
manual which the fisherman can read and understand.
Strong demand in Tanzania
Chipepo (Tanzania): There is a great demand for outboard
and inboard motors in Tanzania, East Africa.
The traditional double chine boats, called Ka Rua, arc the
ones mainly built there by the local carpenters. The length of
these craft is less than 40 ft (12.2 m), using one main sail. The
rigging of the sails has been learned from the Arabs. They
are driven by the wind. Both large and small types of these
craft use the same means of sailing. Some of these boats are
good if they are mechanized by outboard or inboard engines
for the larger ones. Prototype boats have been developed by
the Ministry of Agriculture in 1961. It took three years to
arouse the fishermen's interest in modern craft.
Later the fishermen were given loans to enable them to
buy the new types of small craft. These craft are built by 12
apprentices and are 24 ft (7.3 m) in length and powered by
l()hp outboard motors. Eventually, some of the first-
mentioned sailing boats will be mechanized. The experience
gained by other developing countries and the information on
experiments conducted elsewhere will be of much benefit to
Tanzania when outboard and inboard mechanization is
started.
Earnings must increase
Sapre (India): Kvaran and Borgenstam have given very useful
information. Kvaran has stated that labour-saving is not in
itself an objective. This is not clearly understood. When a
boat is motorized, the owner has to increase his earnings by
various ways like going out to sea for a longer time, using
more gear, etc. However, it may not always be possible to
increase his earnings sufficiently and in such an event he may
prefer to reduce one of his crew to increase the earnings per
head. This is more so when a new boat is built and the engine
is installed. With rising costs of boat-building materials and
engines, the use of labour-saving devices appears essential. It
would have been advantageous if winch installation would
also have been covered along with the engine installation.
[379]
No mention has been made about spares. It is very essential
to provide for spares, especially if the engine is an imported
one. Sapre agreed with Kvaran's remarks about difficulties
with stern gear when it is not manufactured by engine makers.
Kvaran has correctly emphasized the unsuitability of some
materials in tropical waters, even though they may be suitable
in temperate waters. In a few cases, the fishermen lost their
propellers, as the propeller shaft and nut were not made of
proper material. The remarks about hand-starting of engines
are useful.
Borgenstam has covered various aspects with regard to
marinization of automotive engines. In India a few engines of
"land type" are being marinized and the various points
stated by Borgenstam on marinizing should be of benefit.
McNeely (USA): Kvaran pointed out the need to do more
than just sell an engine or other equipment. One must also
provide training, repair facilities and periodic maintenance
checks. This is an excellent paper with invaluable hints for
anyone connected with mechanization of indigenous small
craft in developing countries.
Borgenstam's paper with its thorough discussion of prob-
lems in the introduction of mechanization to small craft in
developing countries is valuable for its presentation of the
relationship of social preferences in the selection of size and
type of engines, controls, propellers and fuel systems. He gave
hope that a current transition period between ignorance and
familiarity with modern mechanisms will solve some of the
problems.
Skilled maintenance essential
Lyon Dean (UK) : Mentioned the importance of the training of
those who are to look after the engines. Dean underlined what
Gnanadoss had said on this point, which is a problem not only
for developing countries. Any new mechanical development
on a fishing vessel tends to be looked upon with suspicion by
fishermen. The advantage of this new mechanical equipment
can be nullified by very minor failure.
Therefore, if one is to have new mechanical equipment
accepted readily, one must ensure that the operator at sea is
trained in its use and its maintenance. Engineers on fishing
vessels should be trained to a comparable level with merchant
marine engineers.
A comprehensive spare part service should be available in
local engineering shops and repairs carried out by men who
have been fully trained by the makers in major servicing. This
will be even more important when going into diesel electric
machinery.
Useful experience from Ireland
O'Connor (Ireland): Kvaran's paper gave a very adequate
account of the many problems facing development officers in
many countries. Kvaran has, in enumerating all the difficulties
which can arise in engineering indigenous craft, made a very
good case for concentration by developing countries on the
establishment of suitable designs for motorization. O'Connor
suggested for Kvaran's consideration that the successful
scheme adopted in Ireland for the replacement of the manually
propelled "curragh" of lath and canvas by a planked open
boat of 26 ft (8 m) or 3 GT (weight 1 ton) powered by an
8.5 hp air-cooled diesel with 2 : 1 reverse gear on propeller,
and financed mainly by a grant and low interest loan scheme
might be suitable for copying. These small craft in Ireland are
operated mainly by part-time fishermen on pot fishing, drift
netting and even trawling and are to be found very widely
scattered on general rocky West Coast of Ireland. They can
be beached satisfactorily in not too difficult a manner and
kept in safety during severe weather, which has a habit of
occurring without much warning on the Atlantic shore. If he
were Kvaran, O'Connor would concentrate on outboards for
small craft motorization if hulls were not designed for inboard
engines and would expect fewer headaches as a result. This
problem was dealt with in Ireland by the organization of a
fleet inspection and maintenance scheme, operated by his
Board and designed to improve standards and thus protect
state investment.
Kvaran mentioned the problem of maintenance. This Irish
maintenance scheme was successful and there is now much
greater interest in the machinery and its care, so much so that
the Board no longer does the work and limits itself to the free
inspection of both engines and hulls. Report is given to a
skipper giving advice as to the work necessary and if he so
requests, the work is inspected after completion also. Simul-
taneous with the maintenance programme, interest was
aroused among local garages and machine shops in marine
engine repair and maintenance, as many of these had
experienced diesel fitters who were, on inspection, found quite
capable of carrying out this work and are now doing so, thus
replacing the Board's service satisfactorily, it having initially
brought the machinery to a reasonable condition.
It was found, however, that it became necessary to give
special attention to those operators of the smaller size craft
who lay their boats up for the winter. Proper steps were not
being taken to ensure the well-being of the engines. For this
reason a programme of special visits has been commenced by
the diesel engineer at lay-up time, to these owners to show
them exactly how the lay-up should be done and special
advisory leaflets have been prepared and distributed.
Economic points
Mendis (Ceylon): Estlander and Fujinami point out that the
fishing economy is affected by the number of nets and the
number of days that a fisherman can operate, and they give a
figure of 65 nets which can be shot quickly enough, but take
a long time to haul. Sixty-five nets would be 7,800 ft (2,400 m)
long and at a hauling speed of 20 ft (6 m) per minute, this
would take 6£ hours hauling time. A heavy catch of fish or
change in wind direction also puts a limit to the number of
nets that one should chance shooting.
A 17J ft (5.3 m) boat with 10 hp outboard and two men
working from 10-15 nets has now become very popular in
Ceylon.
Ferrer (Philippines): Considering the mechanization of
indigenous boats and the acute lack of capital, the engines
must be inexpensive. The dugouts in the Philippines are now
using 5 to lOhp four-stroke air-cooled engines. The stern
tubes and fittings are manufactured locally at a cost of about
£7 ($20) and the engines are very reliable ones costing about
£45 to £90 ($125 to $250) per unit. This price is very reasonable
and within the reach of the fisherman. These engines are those
normally used, even though they do not have the refinements
of self-starting and reversing gears. Some 4,000 units are now
in use with very satisfactory performance.
Progress in Japan
Yokoi (Japan): The total number of fishing boats in Japan has
been slightly decreased from about 400,000 in 1954 to about
380,000 in 1963. However, the motorization of these fishing
boats has been considerably advanced year by year. In 1954
the powered fishing boats occupied only 34 per cent of total
numbers, but in 1963 it was increased to 51 per cent. It should
especially be noted that the number of powered fishing boats
over 5 GT had not been increased but under 5 GT the number
has increased 1.54 times during this period. Only 28 per cent
of fishing boats under 5 GT were motorized in 1954, but in
[380]
40
"Q
X
§
d)
I
I
ft
UJ
CD
2
3O-
20
TOTAL
I I I
'XX*'
'N^NON-POWERED
-""POWERED UNDER 5 GT
I
*O
1955
1957 1959
YEAR
1961
1963
Fig 1. Motorization in Japan
1963 the figure was raised up to 45 per cent. The number and
percentage of powered and non-powered boats under 5 GT
is shown in fig 1 ; fig 2 indicates engine types for the powered
boats over the past ten years.
Tables 1 and 2 show the progress of mechanization and
types of engines used for various sizes of vessels.
From table 2 it is clearly seen that diesel engines play the most
important role in mechanization of small craft in Japan.
Over 80 per cent of fishing boats of 1 to 5 GT are motorized
and this percentage is increasing year by year. For the power
source of the boats, use of diesels is being increased and it is
assumed that most of the boats will be powered by diesels in
the near future. Generally speaking, the size of power required
6O-
O
u
O
s
Q.
20-
NON POWERED
N
ELECTRIC^
IGNITION
POWERECJ^ —
\
^
f
^/DIESEL
I
1954 1956 1956 I960 1962
YEARS
Fig 2. Motorization under 50 GT
for fishing boats varies according to the fishing method and
place, and it is difficult to obtain exact relation between size
of boat and engine power. Fig 3 shows the relation between
the gross tonnage of boats and hp range of diesels and the
speed of the boat obtained under the condition, based on the
statistics of existing vessels in Japan. It is normal for these
vessels that the range of L/B is 4 to 5 and L/T is 8 to 11.
Average main dimensions, engine output and speed obtained
for various sizes of Japanese vessels are shown in table 3.
A few examples of principal particulars of dicscl engines
TABLE 1
Progress of mechanization of various sizes of vessels
Grand total Under 1 GT 1-3 GT
3-5 GT
Total
Non-powered ....
Powered
. 350,258 (100%)
. 182,574(52.0%)
. 167,684(48.0%)
202,063 (100%)
158,223(78.5%)
43,840(21.5%)
120,649(100%)
20,791 (17.0%)
99,858(83.0%)
27,546 (100%)
3,560(13.0%)
23,986(87.0%)
Diesel .
Hot bulb
Electric ignition
TABLE 2
Types of engines used for various sizes of vessels
Grand total Under 1 GT
107,757 (64.0 %) 20,296 (46. 1 %)
11,201 (6.7%) 384(0,9%)
AQ V)& /->Q 10/\ 1? I An /<7 no/^
48,726(29.3%)
23,160(53.0%)
1-3 GT
70,551 (71.0%)
4,768 (4.4%)
24,539(24.6%)
3-5 GT
16.910(70.0%)
6,049 (25.0%)
1,027(5.0%)
[381]
TABLE 3
Average main dimensions, output and speed of various sizes of vessels
Under 1 GT
1-2 GT
2-3 GT
5-5 GT
Length
ft
m
16.4-21.3
5.0-6.5
21.3-36.2
6.5-8.0
27.9-31.2
8.5-9.5
31.2-36.1
9.5-11.0
Breadth
ft
m
3.3-3.9
1.0-1.2
4.3-5.3
1.3-1.6
5.6-6.2
1.7-1.9
6.2-7.2
1.9-2.2
Depth
ft
m
1.6-2.3
0.5-0.7
2.0-2.6
0.6-0.8
2.3-3.0
0.7-0.9
3.0-3.3
0.9-1.0
Engine output ....
hp
3-5
6-10
10-15
15-25
Engine weight .
Ib
kg
220-440
100-200
440-550
220-250
550 880
250^00
880-1190
400-540
Speed
knots
4.5-5.0
5.0-5.5
5.5-6.5
6.5-8.0
TABLE 4
Specifications of diesel engines (vertical type)
Item
Unit
Under 1 GT
1-2 GT
2-3 GT
3-5 GT
Cooling system .....
,
Sea water
Sea water
Sea water
Sea water
Cylinder arrangement
Vertical
Vertical
Vertical
Vertical
No. of cylinders ....
3
2
2
1
Cylinder bore
in
mm
3.7
95
3.7
95
3.3
85
3.3
95
Stroke
in
mm
4.5
115
4.5
115
3.9
100
4,5
115
Stroke volume
in3
cm"
149
2,445
99
1,630
69
1,135
50
815
Output
hp
24
16
11
7
No. of revolutions of crank shaft
rpm
1,600
1,600
1,650
1,400
No. of revolutions of propeller shaft .
rpm
870
870
708
805
Break mean pressure ....
lb/in2
kg/cm8
78.2
5.52
78.2
5.52
75.1
5.29
78.2
5.52
Piston speed .....
ft/sec
m/sec
20.1
6.14
20.1
6.14
18.0
5.5
17.6
5.37
Dry weight (including stern gear)
Ib
kg
1,057
480
814
370
550
250
506
230
CO
o
UJ
Ul
12345
GROSS TONS
Fig. 3. Sire, speed and hp of boats
are shown in table 4, according to the sizes of vessels installed
with them, and an installation arrangement of such an engine
is shown in fig 4.
These engines are designed for less expensive production,
easy handling, long durability low maintenance cost and
comparatively light weight.
The motorization of fishing boats under 1 GT is far behind.
In 1963, approximately 80 per cent of them were not powered.
There were a few types of vertical water-cooled diesels for this
size of vessel. Easy handling, easy starting by hand, light
weight, low fuel consumption, long durability and low
maintenance costs are the most important factors indis-
pensable to this size of engine.
The modification of horizontal water-cooled diesels for
agriculture and industrial use into marine diesels has already
been taken up. For this, the rpm is reduced and a reversing
gear added. The power takeoff has been connected to the
propeller shaft through the reversing clutch as the power
takeoff runs at half speed of crank shaft. The stern shaft is
equipped with the lifting device in most cases, which is
convenient in shallow waters.
[382]
Fig 4. Layout of 2 to 3 GT boat with 4 ftp horizontal diesel
Technical details
Modified engines are equipped with cooling water pump
instead of evaporating cooling with a hopper tank provided
with land-use horizontal diesels. The fuel oil tank is usually
integral with the engine body for the land-use horizontal
diesels, but this has been so modified that the tank can also
easily be installed separate from the engine body. Fig 5 shows
the installation drawing. The specification of the engine is
referred to in the first and second columns of table 5.
These diesels have comparatively small height and can be
installed under the working deck and keep good stability.
Since the engines are compact, less space is required. At
present, over 10,000 sets of this type of engines have been used,
forming about 23 per cent of the powered boats under 1 GT.
A special arrangement has been made to install small
horizontal agricultural diesels. This particular application has
been successfully made in Vietnam. The Vietnamese indigenous
fishing boats are called "bamboo bottomed** junks. The hull
is made of bamboo-knitted basket and detachable wooden
deck is fitted. It is difficult to install the conventional marine
engine in such a unique boat. Therefore, a special outboard
engine with combination of compact, light rigid agricultural
diesel and stern gear devices has been successfully developed.
These engines arc the same as the engines which have been
used for pumping water, polishing rice, running fibre decorti-
cator and so on in the country (fig 6).
The engine hopper is provided with the device to protect
overflow of the cooling water. The stern gear device is driven
TABLE 5
Specification of small diesel engine (for under 1 GT boats)
Unit
(/)
(J)
(.*)
(4)
Cooling system ......
Sea water
Sea water
Sea water
Air
Cylinder arrangement ...
.
Horizontal
Hori/onlal
Horizontal
Vertical
No. of cylinders ....
1
1
1
I
Cylinder bore .....
in
mm
2.8
70
3.3
85
2.6
65
2.6
65
Stroke
in
mm
3.1
80
3.9
100
3.0
75
2.8
72
Output
hp
3
4
3
3
Stroke volume ......
in3
cma
19
308
35
567
15
249
15
239
No. of revolutions of crank shaft
rpm
1,800
1,500
2,000
2,600
No. of revolutions of propeller shaft .
rpm
900
750
1,000
1,300
Brake mean pressure .
lb/in2
kg/cm2
69
4.87
60
4.23
77
5.43
62
4.35
Piston speed ......
ft/sec
m/sec
16.4
5.0
15.7
4,8
16.4
5.0
20.4
6.24
Dry weight (including stern gear)
Ib
kg
286
130
440
200
207
94
148
67
_- 995-
Fig 5. Layout of 0.8 to 1.5 GT boat with 4 hp horizontal diesel
[383]
Fig 6. A 3 hp horizontal diesel installed on deck
by a V-belt and the reduction of the propeller speed is adjusted
by the pulley ratio. It is equipped with lifting device and clutch
gear which provides positions of forward, neutral and reverse.
This special engine has all the necessary function for operation
of the boat. The engine and stern gear can easily be installed
or detached respectively with only four bolts. At present these
engines have the types of 3, 3.5, 4.5, 5, 6 and 8 hp. For
reference, the specification of the 3 hp engine is shown in
column (3) of table 5 and fig 7 indicates installation drawings
of the engine with the "bamboo bottomed*' junk.
Some types of small fishing boats are constructed with very
thin board, therefore, it is indispensable to install lighter
Fig 7. Layout of 2 to 14 GT Vietnamese fishing boat with 3 hp horizontal diesel
[384]
diesel engines on such boats. For instance, the aforementioned
horizontal diesel engine of 3 hp weighs 210 Ib (95 kg), includ-
ing stern gear, which might be a little too heavy for the small
boats, depending on the construction of hull. Taking this into
consideration, the undermentioned engines have been
developed for inboard installation.
The modified air-cooled diesel develops 3 hp and weighs
about 148 Ib (67 kg) including reversing clutch with reduction
gear. The air-cooled diesels were originally designed for land
use and have been used for powering agricultural two-wheel
hand tractors, portable generators, air compressors, winches,
etc. And with adaptation of reversing clutch with reduction
gear, these engines have been developed into marine diesels;
they are cheaper due to mass production and have the charac-
teristic of easy handling, rigid construction and lower main-
tenance cost. The power of the engines is taken off from the
crankshaft and is connected to the propeller shaft through the
reversing clutch with reduction gear. The reversing clutch with
reduction gear is of simple cone type.
in sheltered water, 1 hp per 1 ft (0.3 m) of boat length;
in open sea 2 hp per 1 ft (0.3 m) of boat length;
for shrimping 1 j hp per 1 ft (0.3 m) of boat length.
The Government is anxious to obtain bigger boats in order
to develop lobster, shrimping fisheries and middle-water
trawling.
Propeller noise
Margetts (UK) : The question is : does noise from the propeller
frighten fish? Mechanization has been profitable and, with
unchanged fishing gear, ships have progressed from the use of
sail, which is silent, through steam engines to noisy motor
boats, but still the catches have kept increasing. So it can be
said that noise has not had a very bad effect.
Fish can hear and their range of hearing is somewhat
similar to that of human beings. They are most sensitive to
low-frequency noises. Their ability to detect direction is,
however, poor. A steadily-increasing noise, e.g. from an
> Layout of 0.5 to LI GT boat with 3 hp air-cooled diesel
The installation of the 3 hp engine is shown in fig 8. The
specification of this engine appears in column (4) of table 5.
About 2,000 sets or more of the air-cooled marine diesels
have been in use in Japan, Okinawa and South-East Asian
countries for the last one or two years.
Caribbean practice
Plosso (Trinidad and Tobago) : Good fishing grounds surround
his islands. This has attracted over 200 Japanese longliners
fishing for tuna and large numbers of fishing boats from
Formosa and the USA fishing for shrimp. Although the
population is one million and there arc 74 fishing centres there
are no fishing harbours. There are about 2,400 pirogues
propelled by outboards of about six different types and 600
shell boats powered by inboard engines. The outboard motor
on the pirogue must be carried from the water to the fisher-
man's home daily and should therefore be light. The 600 shell
boats are 35-40 ft (10.7-12.2 m) long and are used for
shrimping.
Maintenance and servicing are important requirements.
Therefore most fishermen have two outboard motors, so that
if one should fail, the other may be used while the other is
repaired. The distance to the repair shops is sometimes as
much as 20 to 30 miles, therefore the outboard is preferred
because it is much easier to transport an outboard engine to
the depot than tow the boat with the inboard engine to the
repair shop. The average catches of pirogues engaged in
trolling and handlining is 60 to 80 Ib (27 to 32 kg) per day
and 300 to 500 Ib (135 to 230kg) when gillnetting. The
fishermen are encouraged by the Government by a duty rebate
on gasoline and diesel oil, a loan for buying a boat or engine
and on engines and no import duty imposed on vessels over
35 ft (10.7 m) in length and on engines and special equipment
on fishing vessels. As a general guide for engine installation,
the fishery authority recommends the following:
advancing trawler, probably does not affect the fish, but a
sudden noise will frighten them perhaps causing them to
scatter. In some methods of fishing such as ring netting, the
crew are careful to make as little noise as possible.
Trawl warps split up shoals of pelagic fish and steaming
ships disperse fish near the surface, but this is probably due to
sight rather than sound. It is likely that in dirty water propeller
cavitation will not affect fish much because it cannot be seen,
and that in clear water it is only one of a number of things that
fish will see, so that, in general, propeller cavitation will not
be an important factor in frightening fish.
There are, however, many species of fish and wide ranges to
both their condition and the condition of their environment
so that the sort of generalization given here must be accepted
as such.
Traung (FAO): When fishing for tuna with live bait in
Australian waters, it has been noticed that steel ships catch
rather less than wooden ones. Ships with their engines aft
catch rather less than those with their engines forward
because fishing is done aft, and if the auxiliary engine is near
deck level rather than below the water level, so much the
better. It seems that vibrations aft are especially liable to
reduce the catch.
Nickum (USA): In the first steel tuna clipper in the USA, it
was considered whether the hull noise would frighten the fish.
Douglas Fir chocks were placed under the engine and there
was no problem because of the steel hull construction. As has
been pointed out by Traung, generators are normally placed
on the upper deck, but in many USA tuna clipper boats
they are placed in the engine room, with no noise difficulties
although it must be said the engine rooms are forward, away
from the fishing area.
There is a great difference in tropical and temperate con-
ditions as far as equipment and machinery is concerned. Even
[385]
though the machinery may be designed to operate at 85° F
(30° C) water temperature, they do not always function well.
Heat transfer rates must be closely watched and also excessive
corrosion. An example of this is a 10,000 tons fish factory
vessel whose ammonia condensers had | in diameter tubes
which after four months were so fouled that it required the
entire freezing capacity of the plant just to hold the tempera-
tures in the storage hold.
OUTBOARD AND INBOARD ENGINES
Selman (UK): In recent years FAO has done much to
encourage the mechanization of small indigenous craft
through the medium of outboard petrol engines. They were
probably right in doing so, since it can be shown that such
engines can be used to propel the most primitive and inexpen-
sive of all craft ; a solid log.
However, in Selman's opinion, outboard petrol engines
have little advantage except their first cost which might
approximate a half to a third of a comparable diesel inboard
engine. However, since so many outboards are primarily
designed for relatively high speeds of the order of 20 knots
and have a very small propeller, full revolutions are seldom
achieved in small indigenous craft capable of speeds of the
order of 5, 6 or 7 knots and it is by no means unusual for the
potential thrust to be reduced to about a quarter of what is
possible, if a much larger propeller running at much lower
speeds could be adopted. Some few firms do in fact fit 4 : 1
reduction gears and larger propeller more suitable for small
commercial craft but these of necessity cost more.
Selman hoped everybody concerned would be quick to
adopt the next step which he saw as simplified by soundly
designed craft of a more serviceable and conventional type,
propelled by the cheapest of all inboard diesels, the small air-
cooled. The high cost of petrol and frequent servicing required
Fig 9. Performance of a 25 ft craft
Fig 10. Performance of a 36ft craft
by the high-speed petrol outboard will, Selman felt, cause
some disillusionment to native fishermen unless progress can
be quickly made towards more sophisticated craft.
Reference had been made to diesel outboards and Selman
remembered examining a 40 hp engine of this type made by a
British firm and exhibited at a Boat Show some four or five
years ago, but which never went into production. Such engines
would prove too heavy for the transom of most small craft
and produce an undesirable trim. Consider the advantages of
a small air-cooled engine. There is little to go wrong there
are no water pumps, pipes or heat exchangers and in cold
climates there is nothing to freeze up, the fuel cost is nominal
and at 2,000-odd revolutions, very low maintenance.
A comparison made of the performance of a hypothetical
36ft (llm) craft weighing 12.4 tons shows that a 40 hp
air-cooled engine fitted with a 2 : 1 reverse reduction gear
was capable of only 5.9 knots for the same nominal power,
and if the propeller pitch be modified to absorb the whole of
the power available, 6.7 knots became possible.
Actually in the three alternatives the thrust hp was 21, 5
and 9.8 which shows that although the diesel would probably
cost from twice to three and a half times the price of the
outboard, the diesel cost £41 ($115) per thrust hp, whereas
the outboard cost could vary between £50 and £26 ($140 and
$73) when the reliability life and running cost of the outboard
is taken into account probably of the order of 2 or 3 : 1.
More attention should be paid to the use of diesel engines
since mechanization has proved worth while. A similar
comparison has been made for a 25 ft craft and details of both
are shown in fig 9 and 10 and table 6.
Not designed for fishing work
Gulbrandsen (FAO): In any discussion of outboard and
inboard motors, it must be remembered that the present type
of outboards used in fishing boats is to a large extent a
F3861
TABLE 6
Comparison of economics of outboard with inboard air-cooled diesels
Boat
Engine
characteristics
Performance
with standard propeller
L
A
Propeller
Propeller
Actual
hp
ft
tons Type
hp
rpm
Price
designed
Diam.
Pitch
speed
rpm devel-
for knots
in
knots
oped
25
4 out-
6.0
4,500
£115
10
6.4
3.94
4.43
3,650 4.38
board
($322)
(1.08
thrust hp)
25
4 air
6.5
2,000
£245
5.7
16.2
4.45
5.7
2,000:2 6,5
cooled
($690)
diesel
36
12.5 out-
40
4,500
£250
20
8.96
4.07
5.9
3,100 27.5
board
($700)
(5
thrust hp)
36
12.5 air
48
2,000
£866
7.75
20.1
13.56
7.75
2,000:2 48
cooled
($2,430)
diesel
Performance with
special propeller
Boat
Type
Propeller
Actual
hp
Thrust
L
Diam.
Pitch
speed
rpm
devel-
ft
in
knots
oped
hp
25
out-
6.4
3.33
4.94
4,500
6.0
1.6
board
25
air
_
__
__
3.0
cooled
diesel
36
out-
8.96
4.94
6.70
4,500
40
9.8
board
36
air
21
cooled
diesel
For 25 ft boat price per hp for air-cooled diesel is 1.96 times outboard but only 13 per cent dearer per thrust hp under best
conditions for outboard.
For 36 ft boat price per hp for air-cooled diesel is 2.88 times price outboard but only 62 per cent dearer per thrust hp under
best conditions.
Running costs of outboard likely to be 3 times that of air-cooled diesel.
Note: cost for air cooled-engine includes stern gear, shaft stern tube and propeller.
converted pleasure boat engine and not fitted for the job. To
be fair, one must compare the best type of inboard diesels
with the best type of outboard gasoline motor suitable for
heavy fishing boats. That means a sturdy engine fitted with a
slow-running, large-diameter propeller. This importance of
low-propeller revolution has been clearly pointed out by
Traung (I960c, 1964). Since then, there have appeared on the
market some motors following this suggestion. Gulbrandsen
had the opportunity to test two identical motors of 18 hp,
but with largely different propeller-revolutions and propeller
diameter on a 21 ft (6.4m) beach-landing boat with a dis-
placement of 1.1 tons.
Fig 1 1 shows the result of the tests. Above 6.3 knots, that
means for the higher thrust, engine A with the large-diameter
propeller, is clearly the most efficient. At full throttle, it gives
half a knot more speed than engine B. With a heavier displace-
ment, the difference would have been even greater. The fuel
consumption curve shows the bad economy to run the engine
at full throttle. The resistance of the boat increases sharply
above a speed-length ratio of 1 .4. Reducing the throttle in this
range has little influence on the speed, but cuts drastically on
the fuel consumption. If, for engine A, the throttle is reduced
so that the boat makes half a knot less speed, the fuel con-
sumption drops from 1 .36 to 0.88 Imp gal/hr (6.2 to 4 1/hr), a
saving of 35 per cent. Tests with other outboard engines
showed that the same speed reduction meant a saving of 25
to 30 per cent in fuel consumption.
These are figures that really count. Applied to the com-
parison between outboards and inboard motors on a 27 ft
(8.2m) boat— as appeared in the paper by Estlander/
Fujinami— it means that the figure of 1.75 Imp gal/hr (8 1/hr)
quoted as the fuel consumption of a 14 hp motor can easily be
reduced by 25 per cent, that is to say to 1.32Imp gal/hr(6 l/hr)by
using the right motor-propeller combination. This gives £130
($360) less in yearly running costs for the single outboard
alternative and a corresponding 26 per cent increase of profit.
It's shocking how little attention some outboard dealers
pay to adopting the right propeller for the boat. Gulbrandsen
had seen an example of nearly a thousand outboards being
sold to native fishermen in a West-African country without any
check on the performance when mounted on the canoe. The
pitch of the propeller was too big, and all the engines were
working far below the operating range recommended by the
factory. There is no excuse for carelessness like this. With an
outboard it is a very simple operation to try different pro-
pellers, measure the rpm with a vibrator tachometer and
select the propeller giving the rpm recommended by the
factory.
The fisherman who wants to buy an outboard for his heavy
displacement boat, should keep the following well in mind:
• Select an engine with a big gear reduction and a large
diameter propeller
• Ask the dealer to test the engine on the boat, measuring
the rotation per minute, to insure that the motor is
working in the rpm range recommended by the
factory
• When going to and from the fishing grounds,
remember that reducing the throttle so that the engine
works at approximately 500 rpm lower than maximum,
means a great saving in fuel consumption and an
increased life of the engine
[387]
N2
600O
5OOO
4OOO
3OOO i
2OOO
IOOO
6 7
SPEED KNOTS
1-2
1-6
1-8
Fig 77. Results of tests on two 18 hp motors with differing propeller
revolutions and diameters
A buyer of an outboard for a fishing boat should pay just
as much attention to the gear ratio and the propeller diameter
and pitch as to the labelled horsepower. He should test the
motor on the boat, measuring the rotation per minute to
ensure that the motor is working in the rpm range recom-
mended by the factory. Only in that way can he be sure that
the thirsty horses in his engine are doing their job.
Importance of canoe catch
Gurtner (FAO): In table 2 of the Estlander/Fujinami paper,
the figures quoted for canoe mechanization in Senegal need
an adjustment, in as much as the total number of canoes in
service is about 5,500, of which approximately 2,500 to 3,000
are mechanized with outboard motors. These canoes account
for about 90 per cent of the annual catch of the country, which
in turn amounts to about 90,000 tons. The conditions under
which this outboard mechanized fishery works are almost
identical to the o^es mentioned by Stoneman. Mechanizing of
Senegal's canoes with outboard motors began before FAO
was materially involved in assisting other countries in similar
work. This is an indication that not only FAO but also other
people consider outboard mechanization to be generally
beneficial to canoe fisheries.
One important reason why this is so can be found in an
inherent structural weakness of dug-out canoes. The section
in the stern of the canoes, which would normally take the
stern tube if an inboard engine were installed, consists almost
entirely of heart wood of very low strength. Apart from making
it difficult to fix a stern tube in this section, vibration set up
by a stern tube would probably destroy the dug-out canoe
very quickly.
Tito (Belgium): Estlander's paper is important and many
problems can be solved if his advice is followed. Each type of
engine has its purpose and sometimes an outboard is the only
reasonable answer, but one should naturally use the inboard
diesel where it is more economical. In the year 1907, a four-
stroke engine with a driveshaft over the stern was first
introduced by a Frenchman.
Traung (FAO): Yes, outboard versus inboard is not really a
correct way to pose the problem. It is really when outboards
and when inboards, because sometimes one has to use out-
boards and sometimes inboards. Experienced technicians can
be of much help to investigate special cases and give advice.
Problems with outboards
Stoneman (Uganda): General observations on outboards in
use in Uganda:
• Of some 6,000 fishing boats and canoes in Uganda up
to 30ft (9m) long, 1,500 are powered by outboards
between 5 to 20 hp. Annual catch is worth £2.8 million
($8 million)
• The reason for overwhelming numbers of outboards
primarily, they are cheap and simple. Craft are beached
each night. Operation life of motors is two to three years,
after which the engines are thrown away. Many owners
have two motors, one in use, one under repair
• Almost all maintenance is by unskilled and heavy-handed
ex-cycle repairers
• There are many failings with the engines. Nuts and bolts
vibrate loose. Propeller blades get knocked off. Power
head casings break. Lower ends drop off. Recoil starters
pull out. Water pumps fail. Manufacturers say this is due
to poor operators and poor maintenance. This is true,
but this situation cannot be changed for many years. If
the men cannot be trained to use the engines correctly,
engine manufacturers must produce engines which can
stand this kind of abuse. This can be done
• The above principle should be applied to much of the
previous discussion and to assist the developing countries.
It is no use suggesting ideal solutions to the problems if
it is clear that they will never be implemented. Designers
must find out by personal experience what is within our
power and design their product accordingly
Nickum (USA): A word to outboard manufacturers. There is
a need for heavy-duty motors and better hydrodynamic
qualities around the shaft strut and propeller. Lower effi-
ciency can sometimes be accepted in pleasure boats use, but
for larger installations and commercial use more work should
be done on efficiency of flow around the shaft.
Specialized types developed
Watase (Japan): Before 1957, there was little demand for
outboards in Japan, except for racing outboards. Accordingly,
the outboard industry consisted of mainly small enterprises
which manufactured small quantities of racing outboards.
Since 1958 the demand, thanks to motorization of fishing boats
and the leisure boom, has increased. As a result one large
enterprise after another pushed into the field of outboards
and gradually the expansion of production scale was done.
Total production of outboards in Japan was 2,900 units in
1957, In 1964 it was 17,800 units. The percentage of increase of
production showed over 600 per cent in 1964, compared with
1957. This is because the motorization of fishing boats was
urged according to the modernization of fishing in Japan.
Therefore, the main range and majority of outboards in
Japan is lower power motors, that is, below 10 hp.
One outboard runs on kerosene and is suitable for the
conditions of fishing village economy. The development of
[388]
such kerosene engines became a main factor to show the
marvellous increase of production, and also this kerosene
engine is enjoying a good reputation in overseas* markets.
Experience in Zambia
Heath (Zambia): Estlander and Fujinami's paper is a very use-
ful reference for the planning of work in developing countries.
He made a few points on the experience of the use of several
hundred outboards in Zambia. His remarks were extracted
from the report of the marine engine instructor to Zambia. It
has been found in the central African lakes of Zambia that
the multi-cylinder outboard of JOhp and over are far too
uneconomical both for reasons of fuel cost, 37 per cent of the
earnings as compared to 21 per cent for the 5 hp model, and
also because of mechanical failure. They had decided not to
pursue the large outboards further, but of changing to 8J hp
inboard air-cooled diesels. The lower-powered simple types
of outboards are satisfactory. Their main weakness is in the
bottom gear. The advent of nylon nets with great fibre strength
has caused the oil seals to be pushed in with a consequent loss
of gear box oil when nets become wrapped round the propeller
shaft. This is a common enough occurrence at night, when
passing over hundreds of surface-set nets. Non-adjustable
carburetor jets are very necessary, for incorrect adjustment of
jets with a petrol-oil lubrication system can cause complete
failure of the engine.
The Government had subsidized the mechanical main-
tenance for two years before the decision was made to depart
from outboards of over lOhp. Heath suggested that when
engines of lOhp and up are required, it might be better to
consider new boats designed for inboard engines with out-
board drives. Gillmer and Gulbrandsen's paper will help
considerably in experimental work using wells, but using
inboard engines instead of outboards.
Valuable tests recorded
Fraser (FAO): The tests Gulbrandsen undertook under such
primitive conditions were quite an achievement. He sent also
back to Rome some more tests carried out with four different
outboards, transom installed on a plastic multi-purpose boat
designed by Estlander to be used as a beachboat. The measure-
ments as in Gulbrandsen's paper were motor revolutions, fuel
consumption and speed. The engines were labelled "heavy-
duty" by the makers. Well, even without any deep investigation
it was obvious that one motor was vastly superior to the other
three in these specific conditions, and it was significant that
none of the motors, even the best one, was capable of reaching
the actual design revolutions. The consumption speed curves
at the low displacement of about 1.1 ton indicated that speeds
were somewhere between 6£ and 7 knots.
Now, referring to the consumption: taking the best motor,
as compared with the other three; at 6} knots the consumption
of the best engine was 0.78 Imp gal/hr (3.6 1/hr) and the next
one was 0.93 Imp gal/hr (4.2 1/hr) a difference of some 1 6 per
cent. At 7 knots it was J.I 9 Imp gal/hr (5.4 1/hr) for the best
against 1 .26 Imp gal/hr (5.8 1/hr) for the next, a difference of
something like 20 per cent. In countries like Western Europe
and developed ones, this doesn't seem perhaps very significant,
but it should be remembered that these motors are to be used
in areas where the financial resources are extremely limited
and that fishing projects are just trying to get off the ground,
and this kind of thing would be completely disastrous,
especially with the very high cost of fuel.
The actual motor units themselves were very similar, so a
close inspection of the propeller design was made to find the
differences. A 1 5 per cent reduction of the total hp was assumed
to take place between the engines and the propellers. A range
of wake speeds was assumed to find the wake speed to carry
out really reasonable analysis, but when these were plotted
on the Bp-delta charts, for the .5 and .65 blade area ratios,
only one intersection was obtained and that for the best motor
between the pitch diameter ratio line and the Bp-delta curve.
A resort was made to apparent slip against advance coefficient.
This was quite significant but it roughly came to the slip
values varied from .2 to .7 for the same design and the K values
for all the advance coefficients were from ,44 to .54 over a
range tested for the reasonably propulsion units, and .34 and
.40 on the ones that didn't appear so good. As these coefficients
are based on the speed of the boat itself and not on the wake
speed, there would be a further reduction of 20 per cent on
this. It doesn't matter what kind of efficiency charts one would
use, one would get absolutely ridiculous efficiencies for these
propellers. The best one has the largest propeller diameter.
Therefore to decrease the Bp in order to get into a reasonable
efficiency area, the only logical change would be reduce the
revolutions.
This has been said many many times by many many people
but it is still ignored for some reason or other. To satisfy the
design conditions for which these particular propellers were
designed, it is estimated that the actual speed of the vessel
should be something like 15 knots or more, which is nothing
like to 6 the 8 knots that they were designed for. Better pro-
peller designs, particularly at lower revolutions, maybe some-
where around J,000rpm range, should be made for this
particular type of heavy-duty work. Selman has argued for
inboard installations because of the superior propeller
efficiencies, so the outboard people know what they are up
against. Jt is not for pleasure that these developing countries
fish — perhaps it is a matter of survival and heavy-duty out-
boards can help make this survival possible.
Difficult conditions met
Borgenstam (Sweden): Estlander's and Fujinami's paper gives
a vivid impression of the difficult conditions under which
outboards have to operate in fishing boats and of the many
respects in which existing engines fail to meet the specific
demands of the fishing. Their list of requirements in the
Recommendation chapter will certainly be interesting reading
to engine makers. However, it must be realized that the
overwhelming demand for outboards comes from the pleasure
boat owners and also that the outboard is a pronounced mass
product, which has been subjected to extensive standardization
and rationalizing both in design and manufacture. It is then
natural that the design development has been dictated almost
entirely by the pleasure craft demand. As far as the upper
part of the outboard (engine head) is concerned, the fisherman
can benefit from the modern pleasure boat development.
Engines have become lighter, more efficiently enclosed, better
protected against water and spray, easier to start and handle.
Also their flexibility and reliability have been enormously
improved in the last ten years.
For the lower part, however, the situation is the opposite.
Bronze gear housings with generous dimensions have given
way to die cast aluminium housings with highly stressed gears
and a good streamlining which is of little value at low speed.
Small high-revving aluminium propellers have replaced the
big slow-running bronze propellers in order to suit the
demands of the 20-35 knots speed range at which most
pleasure craft are used.
For these reasons there seems little reason to try to influence
the makers to modify the engine head, but there is good reason
to encourage the makers to develop special lower units for the
fishing requirements. The cost will be appreciably higher, but
the outboard is still so competitive in price and has so many
[389]
other advantages for small boats, that the effort might well be
worthwhile.
Some adverse points
Vibrans (USA): As has already been pointed out four factors
stand against the outboard:
1 . In the present state of development, its fuel economy is
not very good
2. The two-cycle engines require a mixture of lubricating oil
and gasoline which is inconvenient to mix, and if not in
the proper proportions can affect engine performance
and life
3. The propeller speed is too high for fishing
4. The aluminium alloy in the underwater units is short-
lived with continuous immersion in salt water
Van Donkelaar (Belgium): Commented on Vibran's statement
concerning corrosion on outboard motors. Certain makes have
been poor in this respect. However, now many outboards are
superior to other means of propulsion. Aluminium dye cast-
ings get a chrome-conversion coating and motors are washed
with a special process using dionized water. Engines after this
treatment have stood up to at least 1 ,000 hours of salt spraying
testing.
Further comment on Stoneman's remarks of engine life.
No engine in the world is so badly treated as an outboard.
These engines are often used at full throttle far too often during
long periods of running. At 80 per cent of its power, the motor
would almost double its life. Therefore an arrangement at the
throttle control, giving the operator a positive "feel" when
entering the high fuel consumption speed, would be desirable.
On economy of outboards in the last few years, much
research has been done on this and modern engines have
improved carburation and better ignition timing. The fuel
economy comes close to that of a four-stroke engine.
There is also current research on the hydrodynamic
properties of lower units and propellers. Nylon propellers
have been tried but found to have less efficiency than tradi-
tional propellers, probably because of flexing of the blades.
Placing the outboard
K varan (FAO): The main problem with the installation of an
outboard is to decide where to place the motor rather than
how to do so. Generally speaking, the logical location is at
the stern, but in the case of many local craft this mounting is
not feasible. Excessive overhang and freeboard, coupled with
flimsy construction may make it impossible to fit the engine
there. In small canoes, the trim can be disturbed too much by
the weight of the engine and operator if they are located too
far aft.
In surf boats or boats operating in rough seas, stern mount-
ing may result in the propeller being lifted clear of the water
or close to the surface when meeting waves, causing trouble
due to shearpin breakage, premature failure of the propeller
bonding to the shock absorber and to excessive airation of the
propeller. Airation is due to air being sucked into the propeller
stream when the propeller breaks surface or comes close to
doing so, and can result in almost complete loss of thrust for
many seconds at a time. This is obviously an undesirable
condition for a craft struggling against breakers, doubly so,
if the outboard is also depended on for steering.
Relocating the engine farther forward does not always
provide a solution to the airation problem, and can indeed
aggravate it if the propeller is close to the hull. In such cases
the solution must be found by submerging the propeller
deeper or running the propeller at a slower speed.
Both these solutions may mean that the engine originally
selected will have to be replaced by one with a longer shaft
extension, a lower rpm or a greater reduction ratio.
Stern mounting of an outboard may be unacceptable on
aesthetical grounds. In double-ended dug-out canoes, for
example, there is often a substantial block of wood at the bow
and stern which is not cut away from the inside, as doing so
would only create a small narrow slot in the prow or stern,
and by slicing off the stern block one can make a small tran-
som, which can easily be extended upwards by a crossboard
which would take the motor clamp. Very few owners are
prepared to mutilate their canoes in this manner, any more
than the owner of a pure bred collie or pointer would agree
to docking his dog's tail.
Side mounting
Next to stern mounting, side mounting is the most popular
way of fitting motors to unorthodox hull shapes. This can be
done by mounting the motor itself sideways, with the clamps
more or less in a fore-and-aft position, or by erecting a cross
piece athwartships on which the motor is hung. The former
method is suitable for motors which can be swivelled com-
pletely around, but in its simplest form many involve using
the motor permanently tilted to a side, which is undesirable
for an engine-mounted fuel tank and for some types of
carburettors. The farther aft the engine is the easier steering
will be. On an outrigger, mounting the engine on the outrigger
side of the hull will also aid steering considerably. This may
not always be acceptable to the fishermen, however, if it
interferes with the operation of fishing gear.
The sensitivity of the steering to the motor location depends
on the inherent course holding qualities of the craft. Keel
boats are much less sensitive in this respect than dug-outs or
raft type craft. Power poles or long tails are outboards which
have a long shaft directly driven from the engine crank shaft,
without the usual angle drive of conventional outboards.
These engines have proved extremely useful on many types of
river and backwater craft, but steering difficulties make them
hard to handle on dug-outs and rafts even when mounted at
the stern, the craft tending to stay on their original course,
moving sideways instead of responding to the tiller.
One of the advantages of outboards is that they need not
alter the essential nature of the craft on to which they are
fitted. The Ceylon oru, an outrigger-type dug-out with built-
up sides illustrates this point. The oru is a sailing boat designed
for a large spread of canvas on a very narrow hull, the out-
rigger serving as a counterbalance while sailing is always kept
on the windward side. At high speed the outrigger may be
lifted clear of the water and is then weighted down by a man
balancing on the outrigger poles or on the outrigger itself.
As the outrigger is permanently fastened to the main hull, it is
necessary to reverse the fore and aft ends when tacking, in
order that the outrigger remains to the windward. If an
engine is installed at one end of such a craft, it will at times be
at the stern and at times at the bow. The installation of an
inboard engine calls for a rudder mounting as well, because
the original steering oar does not function properly once a
propeller has been installed. This means that the craft has
completely lost its reversible character and can be sailed on one
tack only.
A special problem
At first it appeared that installation of an outboard amid-
ships would provide the ideal solution; the engine could be
reversed or swivelled as required and the motor could act as
an auxiliary regardless of which end was forward. Again
practical difficulties appeared and the steering was so bad with
the engine mounted amidships that keeping on course required
continuous and strenuous efforts on the part of the helmsman.
[390]
The final solution was to mount the engine near one end and
sacrifice the possibility of using the engine when sailing with
the motor at the bow. Two engines would provide a complete
solution— it is not practicable to shift one engine from one
mounting to another at sea in these long, narrow boats— but
in actual practice it was found that the engine is used almost
entirely as an alternative propulsion, rather than as an
auxiliary to the sail.
Catamarans and teppams, rafts consisting of four to five
logs lashed together, are another example of craft which
retain their essential character when fitted with outboards. In
this case, the desirable features are extremely low freeboard
to minimize drift when fishing with a short string of drift nets,
and the ability to pass over shallow reefs and land on a rough
shore or in heavy surf. Retractable propellers have so far at
least not been able to meet the requirements nearly so easily
as outboards, but further developments in inboard and
outboard drives may change this situation.
Outboards have been mounted in wells in the boat, but this
installation calls for careful consideration of the location
and design of the well, as the flow pattern and pressure
distribution under the boat is very variable, and is disturbed
by the presence of the well of the motor. The main advantages
of a well are ease of handling the motor, freedom from
obstruction on the gunwale and good submergence of the
propeller. If the outboard is to be retractable by tilting, the
well tends to become long and reduces the space in what is
normally a cramped boat to begin with. As the well is central,
it lends itself somewhat more readily to use in dug-outs than
in craft built up on a central keel.
Variations of outboards
Vibrans (USA): Another type of drive should be considered.
This is a small single-cylinder four-stroke air-cooled engine
with V-belt drive to the propeller shaft. This engine type is
used on lawn mowers and is available in size up to about 20 hp.
Under much misuse they still continue to survive and operate
reliably. Fuel tank, exhaust silencer and pipe are all engine
mounted, and as such should be suitable for small open boat
installation. The V-belt drive with sheaves will give necessary
reduction and also tolerate a measure of misalignment. Stepped
cone sheaves could be provided to permit change of propeller
speed whenever it was required to suit some particular operat-
ing condition. Vibrans suggested consideration of this type of
mechanization for such craft as the canoes from Ghana. The
inboard/outboard Z-type installation tried on a Ghana canoe
was impressive, but represented more power and cost than
can be justified. With the installation of the small air-cooled
engine as described, no well need be provided. With the V-belt
drive much flexibility is possible. The cost of the entire instal-
lation of a 5 hp air-cooled engine, driveshaft and propeller
would be under £100 ($300).
Traung (FAO): In Thailand, a four-stroke engine is used to
direct drive the propeller as explained earlier by Kvaran. It is
called the "long-tail" engine. The engine is mounted inboard
on a swivel mounting, while the propeller shaft protrudes over
the stern and into the water. Installations may be from 5 to
30 hp and they are ideally suited for the mechanization of long
canoes. Kvaran's plan to introduce this type of installation in
Ceylon never materialized, but if it had, it might have given
the outboard manufacturers a fright. Power units cost only
about £70 ($200).
Noel (UK): A type of "long-tail" engine as referred to by
Traung was produced until quite recently by a maker of lawn
mowers in UK. It was about 3 hp and cost between £30 to £40
(S85 to $110). If persuaded, they might take up such manu-
facture again.
Author's reply
Fujinami (FAO): There have been so many interesting com-
ments on Estlandcr's and his paper that he wanted to classify
them into a few groups.
Selman, Kvaran, Fraser and Gulbrandsen mentioned the
unsuitable size and rpm of the propeller and the need of
heavy-duty outboards, Fujinami agreed with these comments.
The pleasure boat was the origin of this engine and initially
one had to accept what was offered, but this must be radically
changed in the future.
Mendis, Kvaran, Plosso and Gurtner commented on the
difficulties of mechanization due to the construction of
indigenous craft in developing countries. Twenty years ago
when Fujinami started to work with the Japanese fisheries he
was shocked by the small size of the individual boats he had
to deal with. Some eight years ago, when he joined FAO, the
same situation occurred. One must have very clear ideas of
what types of vessels are used in developing countries. There
is a limit of vessel size and engine output for outboard
mechanization. Where a very large hp is required, an inboard
would be more advantageous, and to do this the whole design
of the boat must be changed and this is not easy because of the
lack of technicians and craftsmen. The outboard is the first
step in mechanization and most vessels in these papers are in
this stage. When the second step is accepted, as mentioned,
plastic construction would be a good idea especially in tropical
conditions.
The third group of people, namely Selman, Vibrans, Heath,
Stoneman and Ferrer, commented on economy of outboard
installation. The economics of outboards compared with
inboard engines are a matter of the size and shape of the
vessels, the availability of persons with mechanical knowledge
and also of convenient maintenance especially in respect of
the tests between the fishing station and the maintenance shop.
In this respect, the outboard has considerable advantages in
that it can be more readily transported. Another point of
favour of outboard installation rather than inboard is the
lower initial costs, which are probably more within the reach
of the fishermen.
A fourth group, namely Vibrans, Noel and Plosso, com-
mented on inboard-outboard engines. The idea of an inboard-
outboard with an extended shaft is widely used and is a
reasonable proposition. This gives hints to inboard engine
makers how to improve their engines so that they can be
installed on indigenous craft.
Fujinami was glad to hear that Tito— being a representative
of the makers— considers this paper a useful guide to outboard
mechanization based on the long experience of Kstlander in
this field.
PROBLEMS WITH INBOARD ENGINES
O'Meallain (Ireland): Engine manufacturers have not fully
appreciated the necessity for their:
• advising objectively on suitability of installation,
taking into account the size and purpose of a vessel
• co-operating in the collection and analysis of data to
enable satisfactory advice to be given. Fishermen lack
the time to collect data, and even large fishing enter-
prises could find the burden of doing so quite onerous.
Engine manufacturers should endeavour to assist in
this
Measures should be taken frequently to check alignment.
More instances of faulty alignment may exist than is generally
realized, resulting in undue wear and even in serious mechani-
cal breakdown. A suggestion, which he had made many years
ago that more use should be made of flexible coupling did not
[391]
at the time find a ready welcome from some engine manu-
facturers, who raised questions about critical speeds.
Regular inspection of engines and mechanical equipment
should be carried out. It is understandable that fishermen do
not like to put their boats out of service more than absolutely
necessary, but where the state has a financial interest in
fishing fleets by way of loan schemes or otherwise, some form
of compulsory inspection could be introduced. The fisherman
soon comes to recognize the advantages of timely inspection
by expert personnel.
Importance of inspection
Rebollo (Spain): Referring to O'Meallain's statement, where
he had expressed the opinion that engine inspections should be
made compulsory, Rebollo said that in Spain a complete
inspection is compulsory for all merchant craft, including
fishing boats every four years, and this covers an inspection
of the engines, whether or not State subsidies were obtained
for the construction of the craft. In addition, a less detailed
inspection is conducted each year. Where fishing craft are
concerned, the inspection is carried out at a time of the year
best suited to the owner of the boat in question. The inspection
includes testing of the engine and of all fire-fighting, life-
saving and other equipment, as well as an examination of the
condition of the hull, to ascertain whether these comply with
the standards laid down by the Government.
Apart from engines coupled direct to the propeller, there is
a growing tendency to instal engines with hydraulically-
operated reduction and reversing gear which, in addition to
making for lighter engines, offer greater propeller efficiency.
In either case, what attracts fishing boat owners is the improved
handling, with bridge-mounted controls. One system that has
not yet gained popularity in Spain, however, is the use of
controllable pitch propeller. It is not sufficiently understood
that the improved propeller performance in every case makes
for lower fuel consumption or higher speed or towing power.
Advantages such as those listed have to be bought with higher
installation and maintenance costs. There has not been suffi-
cient experience of the economics of this system, although
there is no doubt that it represents a technical advance.
Stiff Japanese standard
Oguri (Japan): The requirements for engines for fishing boats
designed for various fishing methods along the Japanese coast-
line are quite hard and severe in many respects. For instance,
in certain fishing, rather a high speed is required. But on the
other hand, in other cases it is necessary to have either a
strong pulling force or the possibility to operate the boat for
a long time at a low speed and with light loads. Furthermore,
even at a temperature of 32°F (0°C) it is always required to
start the engine without a cartridge or heating plug.
In addition to these requirements, it is naturally indis-
pensable to reduce the running costs of the engine and this is
the reason why heavy oil is mainly used for diesels for small
fishing boats in Japan. Since the capacity and durability of
engines depend to a great extent on the fuel used, it is impor-
tant as well to study how to improve fuel. In Japan they had
been keeping close co-operation with oil producers and had
been trying to find good but cheap fuel for fishing boats. Of
course, fuel cost is to a certain extent connected with the tax
problem too.
Oguri believed that this fuel problem is as important as the
manufacturing of less expensive and durable engines and if
one succeeds to discover economical fuel, that will very much
reduce the running cost of boats.
Tyrrell (Ireland): Two-stroke engines possess many desirable
features for fishing vessels, but Irish experience of two-stroke
diesels up to 600 hp in fishing vessels and coasters is that no
one is efficiently scavenged; all require a great deal more
maintenance and cleaning than four-stroke types. One
particular eight-cylinder engine has to have a piston drawn
in rotation for cleaning after every passage.
It has been said by some authorities that the provision of
exhaust valves on two-stroke engines would ensure much
cleaner running, and it would be of considerable interest to
hear the views of the makers of such engines on this apparently
difficult problem.
Valuable points listed
Sinclair (UK): Borgenstam's paper will especially help
developing countries. He commented :
• Design is based on free running because this is the
easiest proof of contract conditions
• Insufficient stress is made of troubles associated with
electrical systems of petrol engines. If small engines are
being considered, magneto ignition may be the best
solution but fuel cost differential in UK at least is not
great
• Supply of local material and lack of trained metal
workers dictates that wooden engine bearers are used
— wood bearers require that frequent alignment of
stern gear is carried out. It follows that wherever
possible, metal bearers should be incorporated
• Access to machinery by cutting bearers is depreciated
because frequently bearers materially contribute to
structural fore and aft strength. If manufacturers
produce engines with inaccessible parts, their products
should not be incorporated in fishing vessels
• Installation must be in accordance with good engineer-
ing practice. Holding down bolts (not "French" or
coach screws) should be a close fit in feet. Steel liners
should be used on wood bearers and jacking and
locking arrangements incorporated in the engine. This
greatly facilitates maintenance alignments
• Flexible mountings are advantageous but they demand
flexible couplings to shaft and to all engine connections
and they tend to lead to the acceptance of misalignment
with consequent bad results
• For shafting, monel is mentioned with particular
regard to anti-corrosive properties. Borgenstam had
omitted to mention its greater strength characteristics
which enable smaller shafting, stern tube, etc., to be
used with therefore practically no increase in cost over
the usual mild steel or bronze shafting. This is good to
bear in mind on up-rated re-engining or first instal-
lation because a smaller stern post can be successfully
utilized
• On lubrication for wet sump engines, the angle of
installation is not always the same as the running angle
and this must be borne in mind. Dipsticks must be
graduated for the angle used
• Exhaust for diesel installation can be of rubber
(reinforced), water injected. Material cost is high but
cheaper labour cost more than balances it out
• No mention of air-cooled engines is made. They are
extremely easy to instal with no water system or hull
perforations. Adequate air supply and exhaust is a
paramount requirement. Air-cooled engines have been
worked successfully in tropical areas
• Fresh water cooling is preferred because of corrosion
in the engine by salt. Keel coolers are simplest and
don't take room in the engine room. If bilge keels are
fitted, they provide adequate protection and in any
case damage can be met by emergency salt water in the
system. Strainers should be in a standpipe and capable
of clearing without shutting the seacock
392]
• The term "corrosion" used in the text under "Cooling"
presumably includes cavitation and erosion and whilst
soluble oil additives help to cure this, installers can
help by ensuring fair runs of pipes without variations
in bore, or restrictors, and thus preventing at least some
aeration
• In the fuel system no mention is made of a fuel return
system for diesel engines. This must be adequate and
in the range of engines under consideration full bore
equivalent to the suction pipes is recommended
• In controls, no mention is made of "stop". This should
always be led to the control position for emergency
use
• No mention is made of multi-engine installations. It
may be that some maintenance problems in developing
countries may be solved by maintenance by replace-
ment with all major maintenance work carried out
ashore
• No mention is made also of the use of V-drives.
Reduction gears are accepted as normal and many
naval architects could find the use of V-drives of
assistance in minimizing engine room space and in
keeping the CG aft
• Water can be a reasonable and easily accessible fire-
fighting medium
Scottish experience
Sutherland (UK): Congratulated Borgenstam and Kvaran on
their papers. With the new and improved methods of fishing,
the hp requirements of the Scottish Inshore Fishing Fleet has
doubled and, in some cases tripled during an approximate
period of ten years, and it is unfortunate that they have no
definite data on which to base the hp requirements for any
particular vessel working with modern fishing gear and using
modern techniques. Some excellent work has been carried out
by Hatfield and it is hoped that such work will be continued.
These increases in hp have presented certain problems and
Sutherland confined himself to the problem of engine bearers
and the methods used in Scotland to overcome this difficulty.
About ten years ago, it was found that considerable trouble
with the alignment of engines was due to several causes, these
being as follows :
• Engine bearers were too short
• Engine bearers were insufficiently supported
• Drive bolts were being used to attach the bearers to
the sawn frames
• Coach screws (or French screws) were used as engine-
holding-down bolts
• The practice of some engine manufacturers in having
the reverse reduction gear box feet on a much lower
plane than those attached to the engine, which involved
the cutting down of the wooden bearers until the
gearbox feet were almost resting on the frames
To correct these faults and also keep the probable increase
in hp in mind, the following regulations were made: Engine
bearers of oak had to be checked over every frame and had to
have a minimum length of two and a half times the distance
between the forward holding-down bolts and the gearbox
coupling. The bearers had to be screw-bolted through the
frames before the hull planking was fitted and side and centre
oak chocks, fastened to the bearers by angle irons and through
bolts had also to be fitted. The side chocks, which also formed
the supports for the flooring were to be fitted at every second
frame and a minimum of two centre chocks were required.
The engine bearers, due to the new required length, projected
into the fishroom for about five or six frame spaces, but due
to the inclination of the engine, these bearers could be reduced
in height to the level of the flooring in the fishroom with no
great impairment in strength.
Placing of bearers
In vessels of over 70 ft (21 m), these engine bearers are
generally carried as far forward as possible, acting as sister
keelsons to the centre keelson. However, with the more rapid
increase in engine hp in the last two or three years, it has been
found that a much stronger and more permanent job can be
done in steel. Jn the smaller craft up to 36 ft (1 1 m), steel H
beams are mounted directly on to the floors and in the medium
size range 40 to 60 ft (12 to 18 m), the H beams arc mounted
on to oak bearers of greatly reduced depth. In the larger size
of vessels in the 70 to 80 ft (21 to 24 m) range, steel bearers
are fabricated on to a longitudinal base plate through-fastened
to the frames. Transverse plate brackets arc welded to the
fabricated engine seats and through-bolted to the frames.
In the three years since fitting steel bearers, there has been
a marked reduction in shaft and stern tube troubles and
vibration has been definitely reduced.
Referring to the different levels of the mounting feet on
engines, the manufacturers were approached and asked to
alter the design of the gearbox and, probably due to the fact
that this amendment would not affect the design of the engine
itself, built mainly as an automotive engine, the necessary
alteration in design was made.
Referring to the last sentence in the chapter on engine
bearers of Borgenstam's paper, where he suggests the use of
wedge-shaped rectangular washers with oblong holes to
assist in lining up, it is common practice in the UK for the
engine-mounting feet to have an extra screwed hole fitted in
which jacking screws can be fitted.
Coping with fire
Turning to the chapter on fire extinguishing, these items
have now, of course, been covered in the UK by the new fire
fighting regulations which came into force on 26 May 1965.
Sutherland would add one other potential danger to Borgen-
stam's list: where sight glasses are fitted to the fuel tanks, self-
closing cocks should be fitted to ensure that the contents of
the tanks cannot run into the bilges in case of accidental
fracture of the sight glass. Again, where a smothering gas
system is used, a battery-driven fan with the control switch
in the wheelhouse should be fitted to the engine room to assist
in clearing the gas after the fire has been extinguished.
Referring to K varan's paper, Sutherland could understand
the difficulties which faced Kvaran and would like to pay
tribute to him for his excellent work in Ceylon. In Sutherland's
opinion, one of the greatest troubles experienced in giving
technical aid to the fishermen in developing countries is the
lack of trained service engineers in these countries. It has been
Sutherland's experience that modern fishing boats built to
FAO designs had been lying on the beaches around India for
lack of spares and maintenance and, in many cases in which
spares were unavailable, cannibalization had taken place
nullifying much of the good work done by FAO experts in the
field.
Dickson had stressed the importance of training fishermen
in the developing countries and Sutherland endorsed this view,
although they obviously had different objects in mind.
Sutherland would like to see more training colleges for service
engineers and maintenance men and for training fishermen in
the running care and maintenance of his engine.
As an illustration of this lack, Sutherland found that several
fishermen in a fishing village in India had removed the rubber
outer stern bearing in recently-acquired fishing boats. On
questioning it was found that due to misalignment of the
engine shafting, the inner packing of the stern tube had wore
[393]
and water began to pour into the boat. The local service
engineer (from the nearest garage) had advised removal of
the outer rubber bearing "because it let the water in". His cure
was then to hammer in a rough-cut soft wooden bush which
immediately swelled on to the shaft and required renewal
every three or four weeks. Sutherland had not decided whether
this service man was inexperienced, or whether he was a very
good business man.
Timing of overhauls
Campion (UK): Congratulated Borgenstam on his comprehen-
sive paper. The boats of the Scottish herring fleet are between
SO and 80 ft (15 to 24 m) in length with engines ranging from
90 to 320 hp. (One boat of 75 ft (23 m) had 380 hp.) The
majority of these engines are of 1 50 hp or more and maximum
rpm are between 900 and 1,800. They are in the main, marine
versions of automotive types.
Borgenstam had suggested that, where boats are logging as
much as 4,000 hours annually, a top overhaul can possibly be
accepted in the first year's running. Experience with Scottish
herring boats had shown that with new engines, logging similar
hours annually, it is seldom necessary to lift the cylinder head
before two years, and then only for checking piston clearances
and liner wear. Cylinder lines are renewed on average after
five or six years, but longer periods are quite common. The
normal procedure is to lift the head at two years and depending
on the wear readings, either annually or every two years
thereafter.
The incident of crankshaft or main bearing failure is very
small and there is therefore seldom need to strip the engine.
In such circumstances, underslung crankshafts are quite
acceptable. Serious engine failures can often be attributed to
neglect by the motor mechanic on board to properly carry
out the engine manufacturer's running instructions regarding
oil changes, etc. Tn developing countries, and for that matter in
developed countries, too much attention cannot be paid to
training the operators in the proper running of the engine.
Where boats are owned by fishermen who work on them, most
of the shares are usually held by the skipper, but a small share
is often given to the motor mechanic, and this gives him some
incentive to look after the engine, which is in fact his own
property.
A point not mentioned by Borgenstam is the need for an
adequate air supply to the engine room. The importance of
proper ventilation cannot be overstressed and this is parti-
cularly important with turbo-charged engines. In fact, some
makers specify that a separate trunked supply shall be led to
the air intake. The aim should be to cool the engine room as
uniformly as possible and to achieve this, care should be taken
to avoid short circuits and to ensure that the hot air can
escape. A supply should be led to a position near the floor
plates, well away from the exhaust so that the cold air will
sweep up across the engine. Better results can often be
achieved with electrically-driven fans which, in case of fire,
can be switched on or off from outside the engine room. One
British engine manufacturer includes electric vent fans as part
of the standard engine equipment.
Economize weight and space
Grenningsaeter (Norway): More economy in weight and space
is of importance to the operator of medium- and high-
powered smaller types of fishing vessels, whether concerning
the main powerplant or the auxiliary. It would be desirable if
a suitable propulsion unit, capable of taking advantage of the
foreseen improved gas turbine, could be developed. Two
likely ways of doing this is to improve the weight/power/rpm
properties of an electrical propulsion motor, and/or to
improve and enlarge the high-pressure hydraulic motor as a
propulsion unit.
A propulsion unit consisting of a high pressure hydraulic
motor capable of taking its power from a direct gas turbine-
driven pump of 300 hp is now being studied in Sweden. The
300 rpm propulsion units is estimated to weigh some 1,100 Ib
(500 kg). A gas turbine of similar horsepower weighs about
90 to 100 Ib (40 to 50 kg). If and when gas turbines become
more fuel-saving, such a unit would be an economizer in space
and weight and could be tucked away on and under the rudder
flat and in the forepeak.
As for auxiliaries, Gr0nningsaeter was thinking of inter-
mittent requirements, the example of the electric power
industry could be followed with advantage on trawlers even
today.
A gas turbine with a hydraulic pump of high pressure would
be instantly available and provide flexible power for the winch
or if electric transmission is used also for booster power for
deep-freezing units in shorter spells. Such units now have an
overhauling frequency of 4,000 hours and would thus be
troublefree for several years as booster power. They will also
be savers of space and weight in the engine room.
Gr0nningsaeter had been a captain of a ship with diesel
electric installations for ten years. The installation was
designed in USA and built in the UK. During all that time he
never carried an electrician on board and had no regrets for
not having done so.
Value of air-cooling
Rawlings (UK): Congratulated Kvaran and Borgenstam on
having a vivid awareness of the many problems associated
with the engineering of small fishing craft, particularly indi-
genous vessels. Many people do not fully appreciate how much
more difficult it is to correctly engine small craft rather than
the larger types of vessel. This is because of the much narrower
margins within which it is necessary to work — margins of
weight distribution, stability, trim, deck space and cargo space
without, of course, forgetting performance. In the two papers
under discussion, account has been taken only of what might
be called conventional engines and methods. In countries
where small-scale mechanization must be undertaken,
particularly where the craft are of the indigenous type and
where one must therefore presume that fewer of the traditional
biases exist, there seems little justification for perpetuating
the older types of machinery without first of all examining the
possibility of the new. Rawlings was referring particularly to
air-cooled engines, of which he could speak without prejudice
since his company manufactures identical versions of air-
cooled and water-cooled engines of similar powers. The pros
and cons of conventional water-cooling methods are dealt with
very fully by Kvaran and Borgenstam, i.e. direct cooling,
indirect cooling (or freshwater cooling) and keel cooling,
but the small type of high-speed air-cooled marine diesel
engine, below about 120 hp, is here to stay. The smaller types
of such an engine could be fitted successfully in most of the
craft with which Kvaran is presumably concerned. To men-
tion only four points in favour of the air-cooled engines,
these are :
• Because of its in-built controlled cooling system, it
very quickly reaches and maintains its maximum and
most efficient thermal running condition, thus lessening
wear rates and opening-up periods
• Overall maintenance is already well proved to be
considerably less than with an equivalent water-cooled
engine
• Corrosion is non-existent
[394]
• Provided the makers' installation recommendations
are sought and followed, then the whole of the
machinery installation can be done more cheaply
In conclusion, some of the most successful air-cooled
installations have been applied to many fishing craft operating
in tropical waters and in developing countries. This is only
because the natural ventilation is made suitable and the com-
bined cooling and exhaust gas outlet is effectively placed. That
is not to say that some of the earlier tropical installations did
other than present difficulties, but by experience in modifica-
tions that were subsequently made, then considerable headway
has been achieved in the vessels that followed during the past
two to two and a half years. These vessels are now completely
successful. Even more can be achieved in this direction, just
as soon as the owners, the naval architects and the engineers
can get together at the very beginning of a project.
Low speeds have merit
Akasaka (Japan): Borgenstam stated "in the higher power
bracket, above about 25 hp and up to about 300 hp, the
market is dominated by automotive-type diesels". Akasaka
wanted to comment on the situation in Japan. For fishing
boats in the range of 200 to 300 hp they commonly use four-
cycle engines having 350 to 450 rpm, piston speeds of 16 to
20 ft/sec (5 to 6 m/sec) and effective mean pressures of
115 to 1701b/in2 (8 to 12 kg/cm2). This kind of engine is
exported to Korea, Formosa and South-East Asian countries.
This is because of the reason that low-speed engines have
many advantages in operation and maintenance costs, dura-
bility and reliability, etc. These features match quite well the
situation of the earlier mentioned countries, \kasaka thought
there should be similar situations in other parts of the world.
Further he pointed out that by raising the mean pressure
values the dimension of low-speed engines will become smaller.
In Japan they are trying to follow this line and expect very
positive results.
Menace of the status symbol
Loevinsohn (Canada) : Borgenstam must be complimented on
a very interesting paper to which Loevinsohn would like to
add two thoughts:
The first refers to the matter of uneconomical hp ratings
which were referred to by several authors of the papers on
Techno-Socio-Economic Boat Problems and also during the
subsequent discussion. Many have been very concerned about
the dangers to individual owners and the fishing industry as a
whole, resulting from engine power choices dictated not by
actual needs, but by a desire to outdo others. When the engine
power choice becomes a status symbol, the economic health
of the industry is clearly threatened.
Loevinsohn could not absolve all naval architects, ship-
builders and engine suppliers from too easy an acquiescence
to unjustified demands for higher power ratings, and would
like to add his plea, directed especially at friends in the engine
industry, for sound economic thinking and greater respon-
sibility on the part of the sales organizations. This also applies,
of course, to a realistic engine selection with respect to engine
speeds for given applications. Peak ratings are frequently
quoted with unfortunate results, where only continuous
ratings should be used and when owners say that they want
horses and not ponies, there is clearly room for improvement.
The second point refers to the matter of air cooling, Loevin-
sohn was somewhat taken aback that nothing was said about
the high state of development of air-cooled diesel engines at a
conference which emphasizes smaller fishing vessels. Especially
for the developing countries this is a very important matter.
Borgenstam dealt quite thoroughly with the many problems
associated with liquid cooling systems. He might have added
that a very high percentage of engine repairs and breakdowns
can be blamed on cooling troubles, either the ones he referred
to or simply incorrect handling of valves or faulty cooling
system maintenance.
Some assured benefits
An air-cooled engine does require care in the design stage of
the vessel, so that adequate air is brought in for cooling and the
discharged cooling air carried away without risking a "cooling
air short-circuit". Where noise control is of significance, it can
normally be accomplished easily at low cost, but it must be
properly planned. But once this has been done— and ignorance
of or indifference to these two points may be blamed for the
occasional unhappy experience despite the use of high-quality
engines, one can offer the owners :
• Engines without pumps, piping, valves, heat-
exchangers or keel coolers. No more cooling system
maintenance problems
• Freedom from overheating on the one hand and freeze-
up on the other. No more cracked blocks or warped
heads
• Elimination of the danger of clogged cooling water
intakes and of cooling system corrosion
• More rapid attainment of ideal operating temperature
and therefore much lower wear. 20,000 and 30,000
operating hours before top overhaul are quite frequent,
even on very small engines
• Easy accessibility and replacement of pistons, rings,
cylinders, etc., from the top, without raising the engine
or dropping the oilpan and without having to remove
large head castings
• Excellent behaviour under partial-load conditions,
with the higher operating temperatures counteracting
carbon accumulation
• The possibility of operating the engine when the boat is
not in the water
• The availability of warm, clean, uncontaminated
discharged cooling air for heating the wheel house or
accommodation
Kettering, the great American inventor, said "What you
leave ofT won't give you any trouble" and this most emphati-
cally applies to even the best liquid cooling system.
Reliable, high-quality air-cooled diesel engines arc available
not, as indicated by a previous contributor, only up to around
100 hp, but actually up to 250 hp at the continuous rating for
heavy-duty marine applications, at a weight per hp of as little
as 12.6 Ib (5.7 kg). The smallest models run at 2,500 rpm;
from 20 to 60 hp they run at 2,000 rpm and the larger
models run at 1,800 rpm for main propulsion applications.
Jn view of the excellent service these air-cooled marine
diesel engines have given as propulsion engines in the Canadian
Arctic as well as in the tropics, Loevinsohn would like to
express the hope that the next technical meeting on fishing
boats will deal extensively with this subject, which is of
enormous interest to all those who are searching for reliable,
simple, high-performance and economical power plants which
combine these usually mutually exclusive attributes to the
advantage of owners who are prepared to look ahead without
prejudice.
While Loevinsohn stressed particularly the use of air-cooled
diesel engines for propulsion of fishing vessels, including their
obvious advantage for right-angle drive units, such as the
widely used "Schottel" drives, they can, of course, be used to
equal advantage for driving winches, hydraulic pumps,
generators and other auxiliaries.
In conclusion, Loevinsohn said that the very interesting
[395]
remarks of H0gsgaard with reference to the difficulties
experienced with two-cycle engines, forced to operate for
longer periods under partial load conditions, should receive
the most careful attention of all those concerned with the
selection of power plants which are not only low in first cost
and compact in design but, above all, absolutely safe in
operation under all foreseeable conditions and economical in
long-term operation. Overall economy does, of course, not
consist of fuel economy only. Anything which increases
maintenance requirements and repair frequency is bound to
reduce the time the vessel will be engaged in its prime activity,
i.e. fishing, and should, accordingly, be considered unattrac-
tive for use in fishing vessels.
High speed and diminishing returns
Selman (UK): Borgenstam has emphasized the folly of
overpowering small fishing boats ; to use a phrase the pursuit
of higher speed follows a law of diminishing returns. The
temptation to seek higher speed is real, since a speed of just
over 7 knots for a 36 ft (1 1 m) craft in terms of miles per gallon
of fuel, represents the higher limit beyond which it seldom pays
to go. Contemporary practice with large trawlers where speed
is generally of greater importance than with small craft
confirms this. Even 7 knots may be considered too high when
it is realized that a drop of half a knot may reduce the power
requirement by 40 per cent. At such speeds, weight is not of
paramount importance, but such parameters as prismatic
coefficient and angle of entrance determine power requirement
which may vary as much as 30 per cent between forms of same
dimensions and weight.
As Borgenstam so rightly said, only a controllable pitch
propeller can provide the total power available in all con-
ditions, since free-running and trawling speeds require a
different pitch, but a word of warning here; the largest
efficiency diameter should be used and the operator should be
aware of the manufacturer's natural inclination to sell him
with a standard diameter.
One limitation of a diesel is its inability to run slower than
a third of its maximum revolutions and here the use of a
controllable pitch propeller will not only remove this but give
control of speed in all circumstances from maximum to zero.
Precautions are required to ensure that it is not possible in any
circumstances by increasing pitch to overload the engine.
In recent years, all engine designers have endeavoured to
increase revolutions and by reducing torque reduce weight and
size of engines. The danger is obvious and so little advance in
piston speed has occurred, and as revolutions have increased,
so stroke has decreased resulting in the square or under square
engine.
Selman did not share the importance that Borgenstam
attached to length of engine, if this meant reducing water
jackets and the over-shortening of power take-offs or skimping
reverse gears.
To avoid vibration
Borgenstam dismissed vibration in a sentence but much
can be done to avoid its incidence. It is always an unpleasant
phenomenon when it occurs. For instance, Selman would
always hesitate to associate a four-cylinder engine with a
four-bladed propeller or a three-bladed propeller with a three-
or six-cylinder engine. More attention should be paid to the
fore and aft position of the propeller in the aperture and the
very thick deadwoods commonly employed in wooden craft
make it desirable to place the propeller further aft than in the
case of a metal craft. In Selman's opinion the minimum
distance should be twice the thickness of the deadwood or a
propeller radius whichever is the larger and that the deadwood
should be tapered to an inclusive angle of 40 degrees. If these
precautions are neglected then there is a real danger of vibra-
tion and reduction of revolutions attainable at full power.
In Selman's opinion, all engines should have an honest
smoke-free maximum rating at which the engine can run
continuously without nursing. Apart from outboard engines,
Selman did not argue the relative advantages of petrol and
diesel engines, since few today would consider the use of the
petrol engine. The outboard engine which has figured so large
in FAO policy is not mentioned by Borgenstam.
Borgenstam says "bearers have to be built up only to meet
the feet". Selman holds the opinion that all wooden craft
should have engine bearers which are only part of continuous
fore and aft girders which extend the whole length of the boat
and to which the floors are attached. Should the engine be
placed so far aft that the immediate engine beds have little
depth, these should be secured to the sides of the deeper
continuous fore and afters. Such an arrangement is seldom
adopted and more often than not the engine beds are no
longer than the engine itself. The engine is generally the
heaviest single unit in the boat and deserves better support
than usually accorded it. Some wooden Swedish craft have
steel engine beds built as an integral whole to steel floors. As
Borgenstam says, most small engines have four to six feet and
holding-down bolts, and even if oak bearers are used for
supporting the engine, frequent realignment will be required
unless the bearers are surfaced by a steel plate to compensate
for the deficient bearing strength of timber.
Most manufacturers of marine engines quote a horsepower
which if described as bhp or shp is the horsepower at the out-
put shaft, since the engines are tested complete with reverse
and reduction gear.
While admitting the merits of monel, Selman could not
imagine any fisherman paying for this expensive material
especially since classification societies require such low stresses
for bronze shafts. Selman regretted that his experience was
contrary to that of Borgenstam in that rubber stern tube
bearings are seldom used. Selman wished Borgenstam's were
true. Their lubrication, in Selman's opinion, can best be
achieved by attaching the discharge from the engines salt water
pump to the forward end of the tube.
Borgenstam's comments under the Exhaust System heading
are, Selman thought, unduly influenced by naval service
practice. For instance, a dry exhaust pipe for a fisherman
would surely not mean a jacketed one. Selman had never
succeeded in persuading owners of luxury yachts to adopt such
and accept the expense in spite of the fact that fires in accom-
modation are frequently caused by overheated exhaust pipes.
Likewise aluminium jacketed exhaust manifolds can, Selman
thought, be dismissed. If a silencer is adopted, this should not
be of the absorbent type in the case of a diesel, as such will
inevitably accumulate oil and catch fire. A silencer similar to
the Maxim and a wet exhaust is more practical and efficient,
but probably still too expensive.
Pumps for sumps
Selman agreed with Borgenstam that a small engine suitable
for an open boat should preferably have a wet sump and if
fresh-water cooled, a combined heat exchanger and header
tank mounted on the engine. If, however, any sort of closed
engine room is part of the design, then there is much to be
said for a dry sump, especially for long periods of continuous
service together with separate header tank, oil cooler and
heat exchanger. The engine room space will lend itself to a
clean and simple layout; all pipe runs can be clearly seen and
removed from the engine. Salt water cooling has a history of
trouble, cracked cylinders and corroded liners, and should
not be accepted.
Gear type pumps are in general the most efficient if
[396]
properly designed for the salt water system, a centrifugal
for the fresh water system. Since the raw water pump is the
Achille's heel of a marine engine, it is natural that the rubber-
vaned impellor type should find general favour. It is cheap and
expendable, but if left idle for any length of time, the impeller
vanes on the cam side develop a permanent set and must be
replaced.
For boats operating in muddy water, Selman regarded keel
or tank cooling as essential, otherwise if a fine gauge filter is
used, this may need cleaning every few hours, or if a coarse
strainer is used, then the heat exchanger silts up, and in either
case, short term neglect may crack cylinders. Twin strainers
are essential allowing one to be cleaned while underway. If
keel coolers are damaged, it is not disastrous if these are
fractured, but in any case, it is not difficult to provide sufficient
protection either by the centre or bilge keels.
The difference between a petrol and diesel engine is not
sufficiently defined for fuel tank installation. When Selman
designed and constructed petrol-driven naval craft, the prac-
tice of syphon feed from tank to engine was commonly
adopted as a precaution against a fuel pipe being shot away.
This works fine when an engine has a carburettor which frees
all air and vapour but would be disastrous if petrol injection
should be adopted. The same would, in Selman's opinion,
adversely affect a diesel.
With fire extinguisher systems here again most of the
comment is inapplicable to dicsels. Most of the precautions
mentioned, Selman had in the past used with good effect and
would only add that the rigid removal of all unnecessary
clutter of inflammable material and b»lges cleared of oil would
do much to isolate any fire aboard. A clean ship is a good fire
insurance.
Engine room ventilation
Nothing has been said about engine room ventilation,
Selman regarded a sufficient supply of fresh cool air as
important as a good fuel supply and from his experience the
provision of this is perhaps the commonest fault in small boat
design, whether in an engine room of a larger craft or closed
cover in an open boat.
In an engine room, two large vents should provide inlets for
fresh air at the after end of the engine room and be lead up
from a low level adjacent to the air intake to an unobstructed
position on deck. In addition, two vents of similar size should
be sited at the forward end of the engine room and continue
from a high deck head level to a protected point above the
deck. If diameter of vents is restricted, then fans should be
used. Likewise the box casing over an engine should provide
an adequate inlet adjacent to the engine's air intake, taking
this latter to the top of the casing if possible and providing an
ample number of holes along the casing top for discharge of
hot air.
Borgenstam omitted reference to outboard petrol engines
which are now used to propel traditional and sometimes
primitive craft. Their lightness and high speed has reduced
their first cost to a minimum but Selman surmised that their
maintenance is expensive, their service life short and their fuel
cost excessive. It has been said if a poor fisherman can only
afford the cheapest, it is no use offering him something more
efficient. However, their adoption has brought a measure of
prosperity and Selman suggested due consideration now be
given to the merits of the cheapest form of diesel, namely the
air-cooled engine to which Borgenstam has not referred. The
air-cooled engine is free of all water pump troubles and needs
no heat exchangers. It is usually a wet sump type and is more
simple an engine than an outboard and although dearer, is
more economical and robust.
One basic precaution governs its performance, namely to
make sure that the hot air discharge is not sucked back into
the inlet fan. Some engine makers provide in their literature
comprehensive guidance how this can be simply achieved,
whether the engine be installed in an open boat or in a large
vessel. Normal ventilation precautions and provision for air
intakes should be followed as for petrol or diesels of the water-
cooled variety, but the hot air discharge must be ducted away
to the atmosphere. Great numbers of these engines are in
service in all parts of the world from the tropics to the Arctic,
where freedom from the troubles of frozen jacket water is a
boon.
Responsibility of suppliers
Devara (India): He observed in Dakar, Senegal, that suppliers
of marine engines are taking full responsibility for alignment
work, fitting various connections and giving a trial run. This
is a working procedure which can well be followed by all
marine manufacturers and their agents, in their own interests.
The engine suppliers must arrange for periodical checking of
engine maintenance and also make service facilities available
within easy reach of all the users. This goes a long way in
establishing a good name, but also better business for engine
suppliers.
Corrosion through rubber contacts
Verweij (Netherlands): Borgenstam mentioned stainless steel
as a suitable material for the propeller shaft. Verweij had some
bad experience with stainless steel shafts used in combination
with a rubber stcrnbearing. The portion of the shaft which
came into contact with this rubber bearing started to corrode
rapidly. In general, stainless steel is only stainless as long as it
is polished. In way of the rubber bearing, especially if there is
sand in the water the polished surface is attacked and can
corrode. Verweij had had many favourable experiences with
propeller shafts of Tobin bronze. This material is much less
expensive than monel and shows excellent mechanical
characteristics.
If possible he would always adopt flexible mountings of
engines since this reduces vibration drastically and makes life
aboard much more comfortable. Fishermen will surely
appreciate this.
Verweij agreed with Borgenstam that a completely flexible
system, i.e. rubber stern bearing, flexibly mounted gland,
flexible coupling and flexibly mounted engine, can, in practice,
be quite successful. However, there are several requirements
to be fulfilled:
• The flexible coupling must be of a type which can
absorb the thrust with the boat going both ahead or
astern
• The flexible mounts of the engine must be rather stiff
so as to prevent too great movements of the engine
• The engine seating, or rather, the whole afterbody of the
ship, should be stiff enough
• The propeller shaft should be reasonably well aligned
by using a fixed coupling first which is replaced by the
flexible coupling after having aligned shafts and engine
Many modern engines require good accessibility to their
lower part. With wooden engine bearers this may present a
problem. However, to expect engine builders to alter their
designs in such a way that no access to the bottom of the
engine is needed seems rather optimistic. In the case of boats
built of FRP, there are no problems in this case. With a proper
choice of the glass reinforcement of the bearers and especially
by using a sufficient quantity of unidirectional reinforcement
in the upper part, the bearers can be made in such a way that
a maximum accessibility of the engine is obtained and yet be
[397]
FRP Engine bearers
Recess for keel cooling pipes in FRP hull
Fig 12. Engine bearers and keel cooling system of FRP boats
strong enough. See fig 12. With a boat made of FRP, it is
quite easy to get a much better prevention of damage by
placing the cooling pipes in a recess in the hull as per sketch.
Multi-engine installations
Lindgren (Sweden): During the last decades, the nearly
explosion-like growth of road transport has made available
for other fields prime movers of various kinds, manufactured
in large series and offering a well-developed spare parts and
service network. The advantages of these engines obviously
lead to using two or more of them in parallel in cases where
the hp requirement cannot be met by a single one. However,
the idea of multiple-engine installations is, by no means, a
new one. In a paper delivered before the Institution of
Mechanical Engineers in 1933, Ricardo (1933) proposed a
diesel-electric main propulsion arrangement, composed of
about 75 small, high-speed diesels in the lOOhp bracket.
Most of the papers presented at the symposium organized in
Grimsby in 1962 by the Internal Combustion Engines Group
of the Institution of Mechanical Engineers on the use of high-
speed diesels in deep-sea fishing vessels, devoted some space
to the problems connected with multi-engine installations.
As regards the high-speed diesel of the automotive type as
such, Borgenstam has pointed out certain advantages, viz..
the low initial cost per hp and the widely spread network of
spare parts depots and service workshops, which though
originally built for road transport can be used as well for the
marinized engines.
The long production series of the modern high-speed diesels
make it economically possible to invest great sums in research
and development, to secure increased reliability and economy
in service as well as in accurate machine tools, jigs and fixtures,
permitting close manufacturing tolerances to be kept, which
in turn lead to improved engine performance and a complete
interchangeability of spare parts without hand fitting. The
latter should be of a special value in the less industrialized
countries.
Borgenstam has pointed out certain properties of the high-
speed diesel in connection with service and overhaul. In the
road transport business, regular maintenance and eventually
"overhaul by replacement** is by now a recognized method.
Lindgren liked to emphasize particularly that the same method
should also be applied to the same type of engine used for
marine purposes. If properly applied, it should reduce the
length of time during which the vessel is held up in port while
the engines are being serviced; it would also reduce the cost of
labour by transferring most of the work to a well-organized
factory.
Economy of replacement technique
However, if, instead of overhauling the engines on board
ship, the system of replacing those due for overhaul by factory-
reconditioned units is to give all the expected advantages, the
installation itself must be made accordingly. It means that
all the attachments, couplings, etc., of the engines, should be
as easily disconnectable as possible, the necessary dismantling
of the adjoining equipment should be reduced to the very
minimum and, last but not least, ample openings and the
necessary lifting gear should be provided in the ship itself. A
standardization of the ancillary equipment would of course
also help in introducing and in running the system. Lindgren
believed that a still closer collaboration on the above points
between the engine manufacturers and the shipbuilders would
be of great value.
He fully agreed with Borgenstam's statement that the crank-
shaft and its bearings should not be overhauled or repaired
on board; thus it may seem to be of no great importance
whether the oil pan can be lowered or not. Incidentally, after
a possible seizure, the replacement of, say, one piston and the
corresponding cylinder liner can be performed with the engine
on its bearers, if the oil pan can be sufficiently lowered.
Lindgren was confident that in several cases this can be
attained once the boat designers are aware of the problem.
The advantages of the high-speed diesels over the low-speed
engines as regards reduced first cost, bulk, weight, etc., in
single engine installations, also hold good for multi-engine
installations in higher hp brackets, even when the arrangement
for transmission of power from the engines to the single
propeller shaft are taken into consideration. Another argu-
ment in favour of the high-speed multi-engine installation is
the varying load demand on the propulsion machinery in a
fishing vessel. When full power is not needed, one or more
of the engines can be disengaged and stopped, allowing the
other engines to operate closer to the ideal load, efficiency and
temperature conditions. Furthermore, they could then be
arranged to cope separately with the independent demands of
the propeller, winch and other auxiliary loads. If one engine
should break down, it would be disengaged, possibly by
automatic devices, and the vessel would still have power to
carry on at somewhat reduced speed.
Transmission of power
When choosing a system for transmitting power from the
engines to the single propeller shaft a variety of transmission
possibilities are possible. The mechanical types range from
mechanically- or hydraulically-operated gearboxes with flex-
ible or fluid couplings, to the simplest of them all, the belt
drive. The mechanically independent drives can be either
diesel-electric or diesel-hydraulic.
Diesel-electric propulsion has the advantage of flexibility in
installation and in use; it allows the diesels, generators and
propulsion motors to be located in the best suitable way for
the working arrangements on board ship. The fact that the
system has not been, as yet, put to a greater use is due, no
doubt, to the high initial cost involved, as compared with
other systems. This drawback still remains, but as ships
become more and more complicated, their auxiliary load
amounting gradually to a higher percentage of the propulsive
load, the cost gap may in time get narrower. Another factor
which must be taken into consideration, especially in the less
industrialized countries, is the still higher scarcity of experi-
enced electricians than of diesel mechanics. Furthermore,
there are certain dangers involved in the use of high currents,
at least in wooden ships, where earthing arrangements are
rather unsatisfactory.
[398]
The hydraulic transmission of propulsion power offers the
same flexibility as the electric system and lends itself well to
multiple engine installations. If successfully integrated with all
the auxiliary drives on board, it may well be considered for
future use; the idea has been extensively discussed for some
years now, but for the time being, it has not gained any
acceptance. That may be due to the high initial cost, or to a
low average efficiency, or again to the fact that apparently
there are as yet no hydraulic pumps and motors of really
suitable capacity and speed available on the market. With the
rapid progress taking place within the technology of
hydraulics, the diesel-hydraulic transmission for multi-
engined vessels may well be a reality in a not too distant
future.
The established transmission system for multi-engine
installations is to have a mechanical gearbox with mechani-
cally or hydraulically operated clutches to engage or disengage
the engines, and a speed reduction from a comparatively high
engine speed to a propeller speed giving a fair propeller
efficiency. The gears must be machined with utmost accuracy
in order to avoid excessive noise, and they become rather
expensive, in any case when more than two engines arc
concerned.
Torsional vibrations can cause difficulties, and on that
account rigid couplings cannot generally be used between the
engines and the gear. To isolate completely the engines from
the gear, thus avoiding practically transmission of torsional
vibrations, hydraulic couplings have been used in the drive
train from the engine to the gear; if of the variable fill type,
they would also allow disconnection of the engine and may
thus obviate the need for separate clutches.
With the advent of couplings, using rubber as the flexible
and damping element, a new, less expensive medium has
become available for limitation of the torsional vibrations to
acceptable intensity. Provided that the dynamic torsional
stiffness of the flexible coupling is chosen in the right way to
make the unavoidable criticals fall outside the intended speed
range of the machinery, a thing which can generally be
accomplished with the units available on the market, all
experience shows that the system well satisfies the demands on
a marine propulsion machinery.
V-belt transmissions
In Sweden, for about 15 years, V-bclt transmissions have
been in extensive use in three- and four-engine ferries; those
transmissions have done very well, the belt life being 30,000 to
40,000 hours. A ferry which was put into service in June 1965
has a propulsion machinery consisting of six high-speed
diesels, driving a single-propeller shaft by V-belt transmissions.
A fair number of tugboats and fishing vessels with twin-
engine machinery are also in service.
Previously, such V-belt transmissions were rather bulky,
due, in those days, to the limited transmission capacity of the
belts, their comparatively large cross section and the attending
restrictions on the minimum pulley diameter. However, with
the introduction of the modern high-capacity V-belts, the
transmission capacity per belt has been increased, while the
width of the belt and the minimum pulley diameter has been
reduced; all these factors contribute to a less bulky trans-
mission. At the same time, the belts are resistant to oil and
water and specially prepared to prevent sparks from the
generated static electricity. If, after an initial service period of
25 to 50 hours, the belts are re-tensioned, in accordance with
the recommendation of the belt manufacturers, the correct
tension of the belt will be maintained for an astonishingly long
time.
A straight V-belt drive consists normally of a driving pulley
with a diameter of 8 to 10 in (200 to 250 mm), from which a
propeller shaft is driven with a reduction of about 5:1.
Thus, the driven pulley on the propeller shaft will have a
diameter of 40 to 50 in (1,000 to 1,250 mm) and its applica-
tion causes sometimes certain difficulties on installation. In
such cases, V-belt drives with only a slight speed reduction,
or no reduction at all, have been used in conjunction with a
reduction gear, driving the propeller shaft. That of course
infers that the inherent simplicity of a straight V-belt drive
has been lost to some extent.
The flexibility of the V-belts has the same effect as the
flexible coupling in the gear drives and isolates the engines
effectively, so that no dangerous torsional vibrations appear.
In order to distribute evenly the load over all the belts, the
pulley grooves must be manufactured to close tolerances,
and the V-belt lengths, in each belt set, must also be matched
to close tolerance; however, nowadays all this is well known
amongst the manufacturers concerned. From the installation
point of view, it is important that the pulley shafts are closely
parallel and that they are maintained as such when the belt
tension is adjusted.
Flat and combination belts
Instead of V-belts, in some cases, flat belts have also been
used, viz. 0 type of belt consisting of a high-strength load-
carrying nylon member, combined with friction layers of
chrome leather. Like the modern V-belts, they arc oil-resistant
and do not generate static electricity. They can be glued on
board to the length required, thus allowing them independent
lengths, free from the existing standards; this can certainly be
of an installational advantage. If originally tensioned in
accordance with the recommendations of the manufacturers,
they are not supposed to need re-tensioning while in service.
Lately, a belt combining the characteristics of flat and V-belt
has also been in use. It is composed of an uninterrupted high
strength member of synthetic cords across its entire width,
built into a single endless synthetic rubber belt, with a series
of parallel longitudinal V-ribs forming its driving face. In this
way the difficulty of matching the belt length in a V-belt set
has been by-passed.
Both the latter belt types have about the same qualities as
the modern V-belt, regarding power transmission capacity,
small pulleys, isolation of torsional vibrations, etc.
In a multiple-engine drive, irrespective of the type of
transmission, whether gear or belts, certain attention must be
paid to the load distribution between the engines involved.
The governor, which is normally installed on a high-speed
diesel and which well fulfills its duties in a single-engine
installation, may have to be specially adjusted to give trouble-
free service in a multi-engine installation. Such an adjustment,
once the need for it has been recognized, can easily be carried
out by an experienced diesel equipment workshop. Further-
more, the engine control equipment on board must be built,
having the even load distribution in mind, that is to say, a
certain movement of the engine control lever on the bridge
must be accompanied by equal movements of the governor
levers of all the engines involved.
Some teething troubles
The high-speed diesels of the automotive type, in their
marine version, have been experiencing some "teething
troubles" in their use a propulsion machinery in multiple-
engine installations; however, it is only fair to say that the
difficulties concerned have not actually affected the basic
engine as such. On the other hand, the "marine" equipment
has, to some extent, been affected in so far as its resistance to
sea water is concerned. However, the bulk of the operational
disturbances can be attributed to the inadequate instructions
[399]
covering the properties of the new equipment and issued by
the engine and equipment manufacturers to the building
yards, as well as to the equally inadequate directions received
by the crews, or simply to the inobservance by them of the
said directions.
Overrating of the amount of misalignment a flexible coup-
ling or a belt transmission can put up with, underrating of the
demands upon the engine control equipment to bring about
an even load distribution and a good co-operation between the
engines, negligence in the piping work giving uneven cooling
water distribution from the common intake to the engines, or
finally in the ventilation of the machine room causing a too
high ambient temperature, are some of the installation
deficiencies which have given rise to service disturbances.
Prolonged running with really high torque, at speeds as low
as 800 rpm (possible on using a controllable pitch propeller)
with a turbo-charged engine, provided with a turbo-charger
matched for a speed range from 1 ,500 rpm and upwards, is
an operational defect, which has caused engine trouble. On
the other hand, there are engines of the same type which have
given a virtually trouble-free service as propulsion engines in
fishing and canal boats, during more than 20,000 hours with-
out need for a main overhaul. It can then be stated, without
fear of contradiction, that when properly installed, regularly
maintained and appropriately run, a high-speed dicsel of the
automotive type will give excellent results in service afloat
both in single and multiple engine installations.
Exhaust systems
Kilgore (USA): Borgenstam stated that wet systems are more
common than dry. This is simple when the engine is aft. In
the USA, Mexico and Canada, however, the forward location
is much preferred for small boats, because of the fisherman's
desire for deck space in the stern. The only feasible wet exhaust
is then out the side, but this obviously will not work unless it
is extremely expensive. The result is that the wet system is
rarely seen.
Kilgore believed that the record will show more cases of
carbon monoxide poisoning from wet systems than from dry.
There may be no better reason for this than the greater length
inside the boat of the wet exhaust pipe and its location through
poorly ventilated spaces. In any case, this danger is very serious
with gas engines.
Borgenstam's remark about excessive power cannot be too
much emphasized. Although this is not a new observation,
naval architects continue to call it to attention, but all over
the world the engines in small craft continue to become more
and more monstrous. This has come about :
• Because of the availability of cheap, high speed, low
torque, heat wasting automotive engines
• Because of man's compulsion to go faster
This is going to be especially debilitating in countries where
fish bring low prices and oil costs dearly. It is necessary to
continue crying in the wilderness, whether or not it will do
any good.
Cooling systems
Montalvo (Peru): Borgenstam mentioned an external engine
cooling system, namely the keel cooler and went on to say that
engine manufacturers are not entirely happy about this, since
neither the layout nor the execution of the cooling system is
under their control and also by reason of the mechanical
drawbacks of tubing fitted on to the outside of the hull.
As regards the three methods of engine cooling used in Peru,
the following remarks are pertinent :
• The conventional method gives rise to the following
problems:
the maintenance of sea-water pump, tubing and heat
exchanger is fouled by the abundant scales rubbed off
the anchovy caught in the net;
heating, sometimes up to seizing point, of the engine,
due to failure of the cooling system, especially as a
result of repeated damage to the impellers;
the high content of hydrogen sulphide in Peruvian
waters, due partly to the presence of anchovy waste,
which renders pump, tubing and exchanger main-
tenance a tiresome business
• Keel coolers mounted as an integral part of the hull
have obviated the disadvantages of the conventional
type, but have in their turn given rise to a serious
problem — the formation of oxides at inaccessible
points
• Externally mounted keel coolers have solved the prob-
lem: there is no pump, no heat exchanger, and no
trouble from scales, oxides, or other sources.
Tubing requirement is in the ratio of .5ft2 (0.046m2)
surface area per engine hp; the material used is 70 per cent
coppernickel. The drawbacks of the system, such as the gal-
vanic action of the coppernickel, have been overcome by the
application of protective anodes, and no mechanical troubles
arise. About 1 ,000 Peruvian fishing boats use this system, with
excellent results. The trend is to instal keell coolers on all
boats, even up to 500 hp ratings.
Bryncr (USA): In answer to Montalvo's query re oxidation of
coolers built into skin of steel hulls, he stated that the use of a
corrosion inhibitor in the cooling water can eliminate
deterioration within the water passages in closed cooling
systems. Most engine manufacturers will be glad to recom-
mend the best type of inhibitor for use with their engines.
Fire fighting
Thomson (UK): Regretted having to be quite at variance with
one point in an otherwise good paper. Referring to fire extin-
guishing Borgenstam said "In the case of a fire on the fuel ,
there is little to be done with water. It might just make things
worse by spreading the fire". Indeed it might, but there is quite
a lot that can be done by the intelligent use of water. Some time
ago, Thomson was confronted with the task of extinguishing
a small fire on diesel oil on an open tray, the fire covering an
area of some 15ft2 (1.4m2). Using a 2-gal (101) portable
water extinguisher with the nozzle at "spray" setting, Thom-
son swept this fire off the tray in about 10 sec. Some time
later, he tackled a larger oil fire. This time the fire area would
be about 250 ft2 (23 m2), over a layer of diesel oil on water
with flames rising 20 ft (6 m) or so above its surface. After
sweeping the surface of this fire very vigorously with a strong
horizontal spray for about 30 sec the flames were extinguished.
Yet again Thomson had the experience of extinguishing an
oil fire from above the flames. Positioned in a totally dark
"tween decks'*, he played a spray nozzle through a hatchway
and, in about 15 sec, extinguished the flames, emanating
from a large tray of burning oil in the space 10 ft (3 m) below,
which were emerging through the hatchway.
His point was this: there are several effective ways of
extinguishing an oil fire. It may, however, be too late to
blanket the flames with fabric as suggested by Borgenstam;
the handiest small portable extinguisher may be at the seat of
the fire or be too small for the size of the fire; there is just the
possibility that a CO2 gas system may be ineffectually applied.
It would be a great pity if fishermen were restrained from
using the millions of gallons of water around them by a
[400]
warning that it was unsuitable for oil fires. Water is, in
general, associated with fire-fighting and this is a psycho-
logical factor. On small vessels a hand pump with which a
fisherman is familiar is, perhaps more likely to be maintained
in good working condition than extinguishers or a system
with which practice is seldom likely to be gained.
Provided emphasis is placed on the need for a spray and a
shrouding action in application, there is no need to rule out
the use of water. Thomson's experiences were acquired under
a system of fire-fighting training which is in operation in the
UK for officers of the merchant navy.
Townsend (USA): BorgenstanVs paper presented a fine
summary of practical features of the mechanical installations
aboard fishing vessels, and is one of the few papers that
touches on fire prevention and extinguishing; accordingly, it
is felt that it is not only in order, but necessary, to suggest
that the efforts of the US National Fire Protection Association
(USA) be mentioned as very appropriate reference material
not only for this paper, but for all those designing, building
or inspecting fishing vessels.
Specifically, NFPA Publication No. 302 (Motor Craft,
1964) treats with fuel tanks and systems, exhaust and cooling
systems, electrical installations, fire extinguishing equipment,
lightning protection, cooking, heating and auxiliary appli-
ances and operation and maintenance.
Rules in Norway
Strande (Norway): In connection with the implementation of
the SOLAS 1960 it was found desirable also to set up new rules
influenced by the new convention requirements, for the fire-
fighting and fire protection of fishing vessels. These rules
apply to vessels of all sizes and arc principally divided into
three parts, viz. one for vessels of 500 GT and above, the
second covering vessels less than 500 and above 25 GT and
the last covering vessels less than 25 GT.
The rules for vessels of 500 GT and above have in the first
place all requirements for the materials of hull, superstructure,
watertight bulkheads, engine and boiler casings, deck and
deck houses. They are to be built of steel or equivalent
material.
The partition bulkheads, doors in alley ways, staircases,
etc., must be built of fire-retarding material. Paints and
deck coverings must be of certain fire-retarding types. Regard-
ing the fire-fighting equipment all vessels of 500 GT and above
must have two separate fire pumps and vessels above 1 ,000 GT
are in addition required to have an independent emergency
fire pump placed outside the engine room.
There are specific requirements for the capacity of pumps,
the fire line, valves, hoses, types of nozzles, sprayers, etc. An
international coupling for shore connection to the fire line
has also to be fitted. The engine and boiler room must be
protected by a permanent fire extinguishing system that can
either be a fog nozzle arrangement in connection with a
separate automatic independently-driven pump or a total
flooding system with carbon dioxide (CO2). There must in
addition be fire hoses and portable fire extinguishers in engine
and boiler rooms. It might be mentioned that there arc certain
requirements to shut off valves in fuel lines and fire dampers
in ventilation channels as well as emergency stops of venti-
lation fans and fuel pumps.
In the accommodation, the rules have specific requirements
to number of fire valves with hoses and portable fire extin-
guishers. Portable equipment such as breathing apparatus,
safety lamps, electrical drill, life line and fire axes must also
be on board.
The rules give definite instructions regarding fire drill and
maintenance of the fire-fighting equipment. Drawings showing
the fire equipment, means of escape, fire alarms, description
of the fire-fighting systems, position of portable fire extin-
guishers, fire hoses, etc., have to be put up in a central
position on board. The rules for vessels of 500 GT and above
are principally up to the standards of the SOLAS 1960 with
respect to fire fighting, except that there are no requirements
for permanent fire extinguishing systems in the cargo holds.
Insulation requirements
The rules for vessels less than 500 but above 25 GT have
certain specifications as regards insulation of engine and
boiler rooms, galleys, etc., if the vessels are built of wood.
Regarding materials in the accommodation, paints and deck
coverings the rules are practically the same as those for the
larger vessels.
As some of the smaller vessels may be built of wood, the
rules contain more details concerning insulation of heaters
and stoves, funnels and exhaust pipes.
Vessels of less than 500 GT must have at least one indepen-
dent fire pump, but for vessels less than 100 GT this
pump may be driven by the main engine and for vessels
between 50 and 25 GT equivalent fire-fighting equipment
may be accepted in lieu of power-driven pump. There
are in the same way as for the larger vessels requirements to
the fire lines, hoses, valves, no//les and sprayers. There must
be at least one valve attached in the engine room. Vessels of
less than 200 GT may have this valve placed at the entrance
to the engine room. If there is a separate auxiliary engine
room, for example, in connection with the preservation of the
catch, extra lire valves must be fitted. Requirements to fuel
shut-ofT valve, fire dampers in ventilation channels, emergency
stops are as for the larger vessels. Portable extinguishers and
fire axes have to be placed in engine room and accommoda-
tion. Number, type and size are specified.
The rules for fire fighting on vessels of less than 25 GT are
common for fishing vessels and other small vessels except
those required to have passenger certificates. The rules have
as for the larger vessel requirements regarding insulation of
engine room, heaters and stoves, funnels and exhaust pipes.
There are specific and separate rules for installation of gas
stoves and cookers using propane or other light hydrocarbons
as fuel on board. Such equipment is extensively used in
smaller vessels, but the rules must of course be complied with
by all vessels using such devices. Vessels of less than 25 GT
are required to have at least one fire extinguisher of 13 Ib
(6 kg) if the vessel is decked. If the vessel is not decked, an
extinguisher may be required. An adequate number of fire
buckets is to be on board. The above fire regulations came
into force on 26th May 1965.
Stern tubes
Breekveldt (New Zealand) : A fishing boat with the engine room
forward requires a long shafting arrangement. If the stern tube
is kept to a minimum length, the stuffing box will be located
in the fishhold or (more favourably) in another designated
space aft of the fishhold. The bare part of the shaft below the
insulation of the hold must be covered over somehow.
Maintenance of the shaft and attention to the stuffing box can
prove difficult with the short stern tube.
Breekveldt had had experience with long stern tubes in
steel vessels. The stern tube is extending below the fishhold
to the aft bulkhead of the engine room. The stuffing box is
now located in the engine room, facilitating regular attention.
The long span between the stern bearing and the stuffing box
usually requires an intermediate bearing. The long stern tube
is therefore underbroken and a box-type container is con-
structed which is linked up (oiltight) with the fore and aft parts
[401]
13. Construction of long stern tube- in steel vessels which have moulded garboards
Fig 14. Construction of long stern tube in steel vessels which have a parallel sided skeg
9
— W
ween ^eplate of intermediate bearing andfounda-
Oiight partition In skeg
Fig 15. Detail arrangement of propeller and propeller shaft in steel vessels which have a parallel sided skeg
1) Stern tube Key to fig 13t 14 and 15
2) Extended skeg y)
$\ ?£XJ0 acc<;mmodate the intermediate bearing and shaft
4) &najt coupling
5) Intermediate bearing t?\ cf A • -/*. x
5a) Bearing housing t» ^fern Deonng (pronze)
5b) Bearing material (ferrobestos) ^ ^SSS^^^^^fff^"* ««0
6) Inspection lid
38BW*"— -- asagr*
of the stern tube. An inspection plate is mounted on the top of
this box. The lubrication of the bearings is by means of oil
and to this end the whole tube and box are filled and fed by a
small header tank. This tank is mounted just below the deck
in either the engine room or the aftpeak space. A sealing ring
is fitted between the propeller and stern boss. The arrange-
ment is shown in fig 13.
In boats up to an overall length of 47 ft (14.3 m) it has been
possible to employ shafts of 20 ft (6 m) length or shorter.
The maximum available stock length of shafts is usually
20 ft (6 m). In boats with an overall length of between 47 ft
(14.3m) and 52ft (15.9m), it still proved worthwhile to
especially import full length shafts. In longer vessels with the
engine room forward, it became necessary to incorporate a
coupling which because of its size must also be located in the
box-like structure used for the intermediate bearing.
In boats which do not have moulded garboards, but which
have a parallel-sided skeg, it was found easier to extend the
skeg inside the hull and utilize the top part of the skeg as
stern tube. A fully oiltight division is then welded just below
the shaft line. Care must be taken that the transverse floor-
plates are matched with similar plates inside the skeg and that
these are welded appropriately to cope with transverse stresses.
Shafts with diameters up to 3.5 in (90mm) and without
liners, can be accommodated satisfactorily inside a skeg with
an internal width of 6 in (150 mm). Jt is just possible to locate
an intermediate bearing inside this width, but it is of course
necessary to put the fastening flanges of the inspection plate
outwards from the skeg.
If a coupling is necessary, then one must resort to a similar
box as previously described. In this arrangement the whole top
of the skeg is oilfilled. It is illustrated in tig 14 and parts of it
are detailed in fig 15. The photographs in fig 16 and 17 show
this type of arrangement for a 60 ft (18 m) vessel before the
framing is completed.
Fig 16 & 17. A long stern tube boat under construction
Just before the closing of the top part of the skeg, all slag,
dirt and loose rust must be removed. Before filling up with
oil and going into operation of the vessel, the tube is flushed
out. A drainplug must therefore be provided on the lower end
near the boss. See fig 15. The oil-lubricated stern gear arrange-
ments have given trouble-free service. Breekveldt's experience
dated back seven years, but there is every indication that at
least ten years can be expected without maintenance, other
than the normal attention to the stuffing box and the yearly
oil changes.
A suitable oil seal at the propeller end is a bron/e ring with
white metal facing which is driven by three stainless steel pins.
These pins are tapped into the propeller boss. The sealing ring
can slide over these pins in fore and aft direction and is
pressed against a flange which is part of the stern bearing.
Pressure is applied by a 1 > 0.75 in (25 > 18mm) soft
rubber ring which is given 0.19 in (5 mm) compression during
assembling. There must be room for the rubber to expand in
the other direction and therefore the housing of the sealing
ring must be chamfered. The rubber ring is cut from sheet
rubber 1 in (25 mm) thick.
Oil grooves in the bearing surfaces and the face of the
sealing ring provide the required lubrification. The oil used is
water soluble oil of grade 30. A suction pipe from which the
oil can be occasionally pumped out is advisable so that
maintenance of this kind is independent of the slipping of the
vessel.
The intermediate bearing is better made up, to save space.
It can consist of a bronze or ferrobestos bush in a housing of
mild steel heavy wall tube welded to a fastening flange. See
fig 15. The material of the shaft most frequently used in
conjunction with this arrangement has been mild steel. It is
virtually not exposed to the sea water.
If in one length, the shaft itself can be used (before the
tapers are cut) for the boring and facing of the boss and
reinforcing plate in the engine room bulkhead (to take the
stufling box). For this procedure the intermediate bearing is
first located in its true position to provide the necessary
support during this operation.
Fixed-pitch propellers
Bryner (USA): Experience in working with builders of
traditional fishing boats has shown the desirability of some
sort of guidelines for the determination of minimum propeller
sizes which are required to produce consistently acceptable
results. Propellers are all too frequently selected without
proper relationship to factors governing performance require-
ments. Those who are technically qualified to make propeller
calculations are often consulted after the hull nears completion
and shaft centreline, propeller aperture si/e and hull clearance
are irrevocably fixed. When these conditions occur, and the
largest propeller which can be fitted is too small, technical
competence is often incapable of circumventing the
inadequacies created by these limitations without resorting to
costly reconstruction of the hull. Without hull correction, a
propeller, which is too small to operate effectively, must be
employed. This type of performance limitation penalizes the
boat owner for as long as corrections are not made. He pays
for a larger engine than resulting performance requires. He
pays for fuel and maintenance at a rate for high brake hp
input while getting low effective hp output. He continues to
lose revenue so long as trip time required to bring home any
given quantity of fish is longer than it needs to be.
The current trend in powering fishing boats points towards
increased power. It is, therefore, becoming more important to
achieve the proper matching of engine and propeller to
produce required results. The following system provides a
[403]
simplified method for determining minimum propeller require-
ments for any combination of shaft power between 20 and
1,200 hp and speed of advance (Va) 0 to 30 knots, disc area
ratios (DAR) from 0.30 to 0.90.
First it is necessary to establish the shp which will be
employed and the proper Va value for the hull. Va should
always be selected for the speed at which the most important
work is to be done where full power is applied. Methods for
determining Va are available to many. Where such data is
not available, the following conversion factors may be applied
to boat speed for a rough approximation of Va.
Single screw
Twin screw
Fine hull
0.85
0.92
Moderate hull
0.82
0.89
Full hull
0.78
0.85
Very full hull
0.73
0.80
Planing hull
0.92
0.94
Estimated boat speed in knots for which the propeller require-
ments are to be established, must be multiplied by the
appropriate factor. The result gives Va to be used in the
nomographs.
Once Va is established, it is only necessary to connect a
straight line from shp to Va in fig 18 to determine developed
blade area required to adequately carry the load. The blade
area required is read directly on the centre scale.
SHP
laoo
1100
1000
000
HOI)
700
(100
80
70
DEVELOPED
BLADE AREA
10 000
H 000
1)00
000
3,000
2,000
1 ,liOO
1,000
HOO
600
:>oo
•100
woo
150
00
50
•10
0.0 nT
5.0
1.0
O.W
0.4
0.3
0.2
0.15
1000 cm-'
HOO
COU
500
400
- 100
80
60
Fig 18. Nomograph for the determination of minimum blade area
when shp and Va are known. To use, connect the selected values for
shp ana Va with a straight line. Read blade area where this line
intersects centre scale.
DEVELOPED
BLADE AREA
10,000
8,000 -=
C,000 -^
HIAMFTFR
DIAMETER
4,000 -
3,000 -
2,000 ~
1,500
1,000 -
HOO -
600 -
400
300
200 -
130
10O -
80 —
40
30
10
-4.0
-3.0
-2.0
-1.3
-1.0
0.8
O.ti
0.4
0.3
0.2
0.15
1000 t
800
GOO
400
301)
DISC AREA
RATIO
0.9 ,
0.7 _j
0.0 .
v common 3-blndc-
(nro|jullnr
0.9
1.0
1.2
1.4
J .0
1.8
2.0
50
60
Fig 19. Nomograph for the determination of minimum diameter when
blade area and disc area ratio are known, or, alternatively, for
determination of disc area ratio when blade area and diameter are
known. To use, connect a straight line from the determined value of
blade area, through the selected value for disc area ratio, to the dia-
meter scale. Alternatively, connect a straight line between blade area
and diameter, then read disc area ratio where the line intersects this
scale.
The value for blade area is then carried to the second nomo-
graph (fig 19) to determine required propeller diameter, based
on disc area ratio to be used. Here, a straight line is extended
from the correct point on the blade area scale, through a
selected disc area ratio. This line will intersect the diameter
scale to indicate the minimum diameter for the disc area ratio
which will provide the minimum required blade area.
Commonly used disc area ratios are 0.50 for many three-
blade propellers, 0.55 to 0.68 for common four-blade
propellers. Where diameters become too large for using
common propeller types, a straight line may be connected
from blade area to diameter, to determine the required disc
area ratio. This will usually need to be done where special
propellers are required.
The next step, after determining propeller diameter, is to
determine propeller rpm. The nomograph (fig 20) for this
determination bears a familiar resemblance to that often used
incorrectly to determine propeller diameter from shp and rpm.
When used to determine diameter, the result does not indicate
whether this diameter is capable of handling the load. For
this reason it should be used last to determine rpm, after the
diameter and blade area requirements are established.
To use this nomograph, a straight line is run from the
proper point on the shp scale through a point on the diameter
scale corresponding to the selected diameter. This line will
[404]
intersect the rpm scale to read directly a nominal rpm for
three-blade and four-blade propellers.
The nominal rpm, determined by this nomograph, will
tolerate a rather wide range of variance. The indicated rpm
value can usually be varied from a 10 per cent increase to 25
per cent reduction in rotative speed and still produce an
acceptable propeller. The smaller "plus" tolerance avoids
approaching excessive tip speeds, while the wide range makes
it possible to adjust rpm to accept commercially available
standard reduction gear ratios.
SHP
RPM
1200
1000
t>uo
500
400
joo
80
60
DIAMETER
3-BLAPE
in
ISO
100
90
80
70
60
50
10
9
8
7
4.0
3.5
3.0
2.5
1.0
0.0
0.8
0.7
0.0
0.3
0.25
0.2
500-
OOC
700
MOO
yuo
1000
Con
700
800
Fig 20. Nomograph for determination of propeller rpm when shaft
hp and propeller diameter are known. To use, connect values for shp
and propeller diameter with a straight line. Read rpm on either
the three-blade or four-blade propeller scale according to the number
of blades used. Rpm obtained may be increased up to 10 per ceni, or
reduced up to 25 per cent to adjust propeller speed to standard engine
speeds and standard reduction gear ratios.
Once diameter and rpm are determined, a builder is able to
provide an aperture for a propeller which will provide, at
least, reasonably good performance. Increased performance,
above this established minimum, can nearly always be obtained
by increasing propeller diameter. It is only necessary to make
the adjustment on the third nomograph (fig 20) and reduce
nominal rpm by an appropriate amount.
It must be kept in mind that blade area is required to carry
the load, but it is diameter which determines how efficiently
the propeller will work. Propeller diameters, larger than the
minimum determined by this system, will nearly always
produce higher efficiencies.
Checking the system, involving many examples over a wide
variety of conditions, has demonstrated the practicability of
its use. Calculations by other methods bear out the basic
correctness of this system. It requires the employment of a
person technically qualified to calculate the final selection of
a propeller, but the builder and the boat owner can now be
assured that such a person is provided with dimensional
limits which are adequate to provide favourable conditions
for good performance.
Company thanked
Traung (FAO): Bryner's nomographs are very interesting and
Traung would like to convey the thanks of the naval architects
to Bryner's company for his latest addition enabling simple
propeller selection to be made. The propeller calculator issued
by Bryner's firm some five or six years ago has been extremely
helpful in this field.
One of the reasons why several naval architects have
difficulties in matching their hulls with the engines is that they
have no instrument with which to easily measure the hp of the
engine. Marine engineers are able to measure hp by means of
strain gauges, exhaust gas temperatures, etc. But what naval
architects need is a simple instrument with which the fishermen
can easily determine the number of hp he is taking out of the
engine. FAO has tried several fuel flow-meters but it was
common that they never worked. However, even on small
aeroplanes there are flow-meters where one can read exactly
what power is being used, for example, during take-off. Why
do not marine engine manufacturers make such an instru-
ment?
Bryner (USA): In answer to Traung he said that his company
and he himself had investigated the possibility of using flow-
meters of the instant flow-rate reading type. It was found that
these do exist, but they are sensitive to fuel viscosity. They are,
therefore, accurate only it' fuel viscosity through the meter can
be controlled. Viscosity of fuels used and variations in fuel
temperature, due to operating and storage conditions, makes
this impractical at this time. Research is in progress. Gasoline
viscosity is quite constant over normal temperature ranges
and such meters are available for use with gasoline engines.
To measure engine power
Hatfield (UK): Rough methods of measuring engine power
in situ are by fuel rack position and by engine temperature,
but where an accuracy better than ^10 per cent is required,
it has been found necessary to measure power by fitting
electrical strain gauges to the propeller shaft.
Engine makers, or at least the bigger firms, can do this with
the aid of their own electronic engineers, for the cost of
materials and wages only. Smaller firms can commission one
of a number of specialist firms to strain gauge propeller shafts,
at a cost of somewhere near £200 ($580) per ship. The read-
out equipment could be purchased at a cost of about £125
($350) to be used indefinitely on any ship.
A system such as this, on a normal uncalibratcd shaft, would
give an accuracy guaranteed better than ±4 per cent, provided
the shaft diameter were measured accurately and the material
specification were known. Instruments to read fuel flow direct
are available on the UK and American market.
Since there seems to be a demand for it, the White Fish
Authority will publish a technical bulletin on strain gauge
torsionmeters, giving full technical details and naming
appropriate manufacturers.
Controllable pitch propellers
Itazawa (Japan): Was very much impressed to see that most
of the Swedish fishing boats had controllable pitch propellers.
The use of the controllable pitch propellor to a great extent
[405]
leads to the automation of fishing boats minimizing crew,
increasing efficiency and improving labour conditions.
In Japan it was quite seldom ten years ago that controllable
pitch propellers were used. However, thanks to the suggestion
of Fujinami, the number of boats with these propellers has
rapidly increased. Now the advantages are highly estimated
among people concerned. Itazawa hoped that the further
study to combine the main engine in a most efficient way
with the reduction gear and the controllable pitch propeller
will surely bring down the operation cost of fishing boats.
Campion (UK): Where power requirements for fishing are
low, as in herring drifting and ring netting, the free-running
requirements govern the power of the engine fitted and a fixed
pitch propeller designed to give its best performance at high
speed is no doubt the best answer. However, increasing interest
is being shown by Scottish fishermen in pair trawling for
herring, and although there is some difference in opinion
regarding the engine power necessary for this type of fishing,
indications are that considerably more power than is necessary
for free-running will be required for pair trawling, particularly
if this method of fishing is to be pursued in water over 60 fm
(110m) for more than a very few months each year. There,
surely, is a good argument for fitting controllable pitch
propellers. Although generally accepted in Scandinavia, they
have not proved popular with Scottish inshore fishermen.
However, some recently completed boats have been fitted
with controllable pitch propellers and, once their operation is
understood, owner/skippers arc realizing their value.
CP propellers essential
Hegsgaard (Denmark): In Scandinavia the controllable pitch
propeller has been considered for a very long time one of the
essentials to the fishing boat propulsion system and such a
propeller was exhibited in Sweden as far back as 1904.
The fixed pitch propeller is rarely used and can be compared
with the controllable pitch propeller, as say a car engine with
one gear as against an infinite number of easily changeable
gears. With a controllable pitch propeller, it is possible to set
the correct pitch for any condition at revolutions and hp most
suitable for the engine. This means that good efficiency can
be obtained in the widely different conditions prevalent in
fishing procedure, i.e. trawling or free-running.
In adverse conditions in the North Atlantic, the general
procedure is to turn the stern of the vessel into the oncoming
seas with the propeller idling. Should these conditions exist
for a long period for a ship with a fixed pitch propeller then
difficulties can arise with the engines on account of the very
low rpm. These can lead to engine stop so that the ship is
transversed and will be wrecked. With a controllable pitch
propeller, the pitch could have been reduced and the engine
operated with such rpm that it could be kept running as long
as there is fuel in the tanks.
Noel (UK): He had once been instrumental in testing a 13 in
(330mm) diameter nylon propeller on an 18ft (5.5m)
lobster boat, working from the beach and being driven on to
stony shingle, many times a day in the summer when carrying
trippers. After 12 months' use it was still unmarked.
Nylon propellers
Hegsgaard (Denmark): The first nylon propeller in the world
was made in Denmark for use for a Swedish outboard motor.
Tests were carried out with this motor in water in which there
was much drift-wood. The propeller suffered no damage. The
boat was run on to a stone beach and again there was no
damage to the propeller.
It is a difficult operation to cast nylon and it should be done
at pressure of l,3001b/in2 (90 kg/cm2). The best dyes for
casting are of manganese bronze. Early castings were foun
to have negligible moisture content. A better strength an
flexibility are obtained when the moisture content is highei
H0gsgaard had also tried treating in a hot oil bath to improv
flexibility. However, a yellow skin which formed on the surfac
of the nylon caused surface cracking which produced brittle
ness and fracture. Nylon propellers have been used in quantit;
on German amphibious cars. However, for marine use, it i
necessary to have a new type of nylon with more flexibilit;
and higher tensile strength before continuing production.
Manoeuvring
Bruce (Sweden): Manoeuvrability is a very important topic
However, the field is enormous and it is only possible to trea
a small portion, limiting the discussion to controllable pitcl
propellers and hydraulic steering gears. In order to save time
and even more to create safety, the possibility of rapic
manoeuvres is very important and must be well considerec
when planning an installation. Just as important is thai
manoeuvrability should be available under all conditions,
at any speed of the boat and propeller. The two requirements
call for rather big pumps and oil pressures high enough tc
guarantee the manoeuvres.
Turning for a while to propellers only, it is not practical tc
have a big pump working at full pressure all the time, creating
a high oil temperature and wasting fuel oil. To avoid that,
various methods have come into use. One method used quite
frequently consists in having a servo-valve with negative
overlap, that is the lands of the valve spool are ground in such
a manner that when the valve is in mid-position, oil can leak
through the valve from pump to tank and thus the pump
pressure will be exactly what is needed to hold the propeller in
place. Unfortunately the pitch can change a considerable
amount, should the torque on the blades for any reason change
direction and an unstable propeller can also start fluttering.
One system developed and used by one propeller maker,
employs two pumps, different in size and a special valve. This
valve in fact is a combination of two valves with different ways
of acting. In mid-position the valve gives free passage from the
big pump to tank, whereas the passage for the little pump is
closed. The positive overlap for the little pump is about
1/250 in (O.I mm) in each direction and for the big pump
0.1 2 in (3mm). For fine adjustments and slow manoeuvres
only the little pump comes into action, while big pump still
idling. In neutral position, the piston of the servo cylinder is
locked without backlash. When a quick manoeuvre is nearly
finished, the speed of the piston slows down and the piston
creeps to the final position, only moved by the little pump and
no overriding can occur.
Most fishing boats have still the bridge control for engine
governor and propeller separate, but there is a trend to
combine them to a one lever system in order to facilitate the
work for the captain. One must remember that the one lever
system is dangerous for the engine unless there is some kind
of load control. Some engines can give the maximum torque
for a wide range of rpm. For those engines it is simple to
arrange an alarm system giving a warning when full torque
is used below a predetermined engine speed. But the system
is not an automatic pitch adjustment.
If the engine is equipped with a hydraulic governor with
load control pilot valve, a not too complicated method to
adjust the pitch automatically to suit the engine can be used.
But here the simple hydraulic system for propeller manoeuvr-
ing with negative overlap can cause hunting so that the engine
speed rapidly moves up and down. The two-pump system has
given excellent results as the slow final pitch adjustment and
the lack of backlash give the engine governor a possibility to
work in a satisfactory manner.
[406]
A fishing boat should have a quick acting steering gear for
all intricate manoeuvres, but a quick steering gear is a nuisance
when steaming, unless the steering gear is arranged for sym-
pathetic steering. This means that it should act like power
steering on a truck, and move slowly or rapidly, according to
circumstances. Unfortunately that type of steering gear costs
more, but it puts much less strain on the helmsman.
The majority of steering gears give below and up to two by
45 degrees rudder movement. However, it has been shown
that it is a great advantage to use bigger rudder angles, when
manoeuvring at zero and near zero speed. Rudder angles of
65 to 70 degrees have been in use a long time for river cargo
ships and a number of captains of harbour tugboats praise
the bigger rudder angles. For fishing boats they are in use in
Holland and Norway and the least that can be said is that
they give full satisfaction.
Two engines tried
MacLear (USA): Recently a 60ft (18m) open boat had
installed two outboard motors, one in the bow and one in the
stern. This was done for manoeuvrability and reliability. On
trials it did 14 knots and the manoeuvrability was excellent.
Referring to the extended shaft outboard, the normal exten-
sion is some 7 in (18 cm) but he had on odd occasions had to
add up to six extensions. In order to keep the extended out-
board from bending and causing gear wear, he had to support
the stock in three directions with wire.
Many devices used
Wanzer (USA): A cursory count of the references to the
need for better manoeuvrability and manoeuvring devices
contained in a single FAO document (Traung and Fujinami,
1961) discloses that 37 individuals mentioned the matter at
least 83 times. Innumerable publications confirm interest in
manoeuvring and positioning equipment.
Several manoeuvring units are in wide use today, each
offering peculiar advantages in special situations. Bow
thrusters with or without controllable pitch propellers, nozzle
rudders, active rudders, vertical-axis propellers, hydrojets
and steerable right-angle drive units, are some of the schemes
already employed. But, despite the fact that thousands of
installations of all sorts have been made, there is a paucity of
reliable published trial data which depict performance under
service conditions.
Obviously, if main propulsion, steering and manoeuvring
capabilities can be combined in a single unit completely
controllable from the wheelhouse, eliminating the need for the
usual steering engines, rudders, tailshafts and struts, and
without costly sacrifice in performance, so much the better.
The purpose of this contribution is to present hitherto
unpublished trial data on right-angle drive units.
Right-angle drive units are not new. During the past quarter-
century over 6,000 units, ranging in size from 40 to over
1 ,000 hp, have been built and put into world-wide service.
Recent applications include those made in the research vessels
Prospector, Rockeater, Discoverer (drilling rig), Caldrill,
Cuss /, Eureka, Monob /, Albatross IV, Josiah Williard Gibbs,
Surveyor, Redwood, Oceanographer and Discoverer (survey
ship).
Japanese techniques
Osaka Shipbuilding Company, of Osaka, Japan, builds
about ten tugs each year. A variety of propulsion systems has
been used to meet particular requirements, Tugs have been
built with controllable pitch propellers and spade rudders,
with controllable pitch propellers and nozzle rudders, with
vertical-axis propellers and with steerable right-angle drive
Type of Propulsion
Controllable -Pitch
Propellers and
Twin Spade
Rudders
Controllable-Pitch
Propellers and
Kort Rudders
Volth-Schnolder
Prop* liars
Riffht-aagi* drive units
( Harbormasters )
and
Kort Nozzles
General Outline
1 pr1-! f^*=*L- -fccy>
JL
<p-S p— -—V-eap
. ^rJ^L
S^- 'J^
jT^ — \3~
•%FT —^r
^Ttrp J^
*" ^ —
UP jy ^
Relative size of tug
Big
Big
Medium
Small
Approximate Engine RPM
400
400
500 - 600
750
Thrust (Pulling)
Towing Thrust Power
25.3 - 27.5 1b /&HP
30.8 - 35.2 Ib/SHP
22.0 • 24.2 Ib /SHP
33.0 - 37.4 Ib/SHP
Main fngliM fUP
(11.5 - |2-5 Kg /$HP
(14.0 - 16.0 kg /SHP)
(10.0 . 11.0 kg /SHP)
flC.O . 17. O k« /SMP)
Tewing Force When Backing,
As a Percentage of Ahead
Towing Force
30%
30 - 60%
90%
100%
Time Required for en
Emergency Stop, In Seconds
39
20
18
10
Tfne Required From Full Ahee
To Full At tern, 1n
Seconds
1
10
10
7
7.5
Arc Over Which Steering
Force Can Be Exerted,
1n Degrees
70°
70°
360*
360°
Steering Tie* Over
Fytl Are Listed Above,
In Seconds
15 - 30
15 - 30
15
15
Tine Required for 360°
Turn, In Seconds
65 - 70
45 • 50
35 • 45
20 • 25
Turning RadlttB 1n
Hull Lengths (L)
3 - 5L
1.5 -2.01
1.0 - 1.3L
1.0 . I.3L
Fig 2L Comparative twin screw tugboat performance
[407]
units and nozzles. Complete sea trials have been conducted
for the first ship of each type built, plus less extensive trials of
sister ships, all intended to supplement and confirm model
test data used as the basis of design and specifications.
From actual experience the shipbuilders have tabulated the
comparative data shown in fig 21. Only two right-angle drive
unit-equipped tugboats — Seiko Maru and Yuho Maru — have
been built to date, but otherwise fig 21 reflects wide experience.
Outline drawings of Seiho Maru are shown in fig 22. Her
dimensions are given in table 7. Model tests were conducted
at Osaka University. Fig 23 was taken on 10th October 1964,
while she was conducting turning trials. Kort nozzles and
four-bladed fixed-pitch propellers were manufactured and
installed by the shipbuilders. Four-cycle, single-acting, turbo-
INBOARD PROFILE
STERN VIEW
Fig 22. Propulsion layout of Seiho Maru
charged 500 hp 750 rpm diesels were installed. Fig 24 is
photograph of Seiho Maru while building, showing tl
complete installation.
The propulsive force of each drive unit can be directed i
any desired angle. The two propellers can be operated eithc
simultaneously or independently from a one-man contrc
stand in the whcelhouse.
Fig 24. Stern view of Seiho Maru
Trials of Seiho Maru were held off Kobe Port, Japan, or
10th October 1964. The weather was fine, sea condition calm,
wind light and a depth of water on the trial course about 50 ft
(15 m). More recently, less comprehensive trials of Yuho Man
were held in the same area, whose limited trial data confirm
the results of Seiho Maru trials.
Ahead and astern bollard pull tests were conducted at the
builders* fitting-out quay (please see table 8). The weather was
cloudy and the sea calm. An adverse wind, about two points
on the longitudinal centre-line of the tug, at a speed of about
9.7 knots (5 m/s) may have affected measured performance.
During the tests, Seiho Maru was trimmed 10 in (0.25 m) by
the stern and her mean draft was 1 1 ft 48 in (3.47 m), corre-
sponding to a displacement of 163.3 tons (166 ton).
TABLE 7
Coastal tug Seiho Maru
Dimensions
Length overall 65 ft 9 g in (20.05 m)
. Length between perpendiculars . . 63 ft 1 1f in (19.5 m)
Breadth (moulded) . . . . 26 ft 3 in (8.0 m)
Breadth at waterline . . . . 25 ft 88 in (7.84 m)
Depth (moulded) 9 ft 6i in (2.9 m)
Draft (moulded), designed . . . 5 ft 102 in (1.8 m)
Draft (maximum), designed . . . 11 ft 3| in (3.45 m)
Displacement 162.4 tons (165 ton)
Displacement, light .... 142.7 tons (145 ton)
Gross tonnage 99.64
Net tonnage 31.56
Fig 23. Turning trial of Seiho Maru
Officers
Crew .
Spare .
Total .
Midship section .
Block
Prismatic .
Waterplane .
Tons/inch immersion
Wetted surface area
Propeller immersion
Accommodation
Coefficients, etc.
0.845
0.580
0.686
0.816
3. 199 (1.28 ton/cm)
2214.4 ft' (205.8 m»)
193.1% diameter
[408]
TABLE 8
Bollard
pull tests
Engine order
Mean propeller
rpm
Total hp
Rope tension
Bollard pull
1/4 ahead
187.8
286.1
1 4,333 Ib (6,500 kg)
50.1 Ib/hp (22.8 kg/hp)
2/4 ahead
233.4
505.0
22,271 lh(10,100kg)
44.11b/hp(20.1 kg/hp)
3/4 ahead
263.9
722.2
30,539 lb( 13,850 kg)
42.3 lb/hp( 19.2 kg/hp)
4/4 ahead
297.1
1,021.4
38,588 lb( 17,500 kg)
37.8 lb/hp( 17.2 kg/hp)
Overload
304.4
1,103.9
40,793 lb( 18,500 kg)
37.0 lb/Jip( 16.8 kg/hp)
4/4 astern
297.0
1,038.5
37,044 lb( 16,800 kg)
35.7 lb/hp( 16.2 kg/hp)
Engine order
Average total
hp
TABLE 9
Speed trials
Average propeller
rpm
Average speed Speed-Length ratio
(knots) y/VL
1/4 ahead
192.4
194.2
6.935 0.867
2/4 ahead
385.3
251.3
8.576
.072
3/4 ahead
554.6
289.8
9.733
.217
4/4 ahead
756.9
316.3
10.473
.309
Overload
818.0
325.5
10.694
.337
2/4 astern
371.8
251.4
8.671 .084
TABLE 10
Turning trials
Initial 360{> turn
Steady turning
Helm angle
.?5C 60° 90'
90°
Right
Left
Right
Left
Right
Left
Right
Left
Time required to complete right-angle drive unit positioning,
in sec
9.5
14.3
8.6
5.9
5.7
6.3
—
—
Elapsed time to complete a 360° turn, in sec.
Maximum heel recorded, in degrees
33.6
9(P)
40.2
8(S)
25.0
8(S)
28.8
6 (P & S)
27.3
8(S)
25.4
8(P)
21.3
6(S)
20.6
6(P)
To determine the minimum speed obtainable with both
engines operating ahead at the lowest engine speed, each of
two sets of observers made ten measurements of the time
required to transverse a distance of 44.72 ft (13.63 m). Under
these conditions, the Seiko Maru averaged 3.07 knots with a
total of 31 shaft hp, the mean propeller rpm being 91.8. Lower
ship speeds could obviously have been obtained with both
engines running by rotating one unit so as to oppose the thrust
of the other and adjusting propeller rpm to suit desires.
Other speed trials were made over a course of 4,642.6 ft
(1,415m) at a mean draft of 11 ft 3i in (3.442m), with a
1ft l£in (0.338m) trim by the stern. Displacement was
161.4 tons (164.0 ton). Runs in opposite directions were
averaged for all ahead speeds in order to cancel out wind and
current effects. A single measurement was made of speed
astern, with an adverse current and a favouring wind. Table 9
summarizes speed trial results.
Trials were made of several different methods of stopping.
On one test, with the tug making full-speed ahead, main
engines were ordered stopped and the drive unit kept in the
ahead position. Seiko Maru came to a stop in 104.8 sec,
travelling about 460 ft (about 140 m). On a second test, both
units were turned through 180 degrees, the engines continuing
to make rpm. Seiko Maru was dead in the water in 9.6 sec,
having run about 66 ft (about 20 m). A final test was made
with the tug at three-quarters-speed ahead (680 engine rpm).
With engines continuing to run at the same speed, the two
units were turned 90 degrees (abeam) in opposite directions,
to oppose each other's thrust. Seiko Maru came to a stop in
10.1 sec, with the same run of about 66 ft (about 20 m).
Turning trials were made to starboard and to port at fuil
engine speed (750 rpm), using drive unit helm angles of 35,
60 and 90 degrees, both units being used simultaneously for
steering. In many multiple installations, especially when less
stringent turning requirements prevail, a single unit is used
for steering, and speed along course over the ground is not so
severely reduced during the turning manoeuvre. The results
of turning trials are reported in table 10.
Author's replies
Borgenstam (Sweden): The discussion has confirmed that to
solve the problem of mechanization of fishing vessels in
remote countries, it is not possible just to copy the existing
machinery plants. Conditions vary widely and even in
developed countries, one is undergoing a revolution in
technical respect. Old traditional ideas are being revised.
Opinions vary as to what the ultimate solution will be.
In the long run it seems that the marinized automotive
engine will most probably capture the market in the power
bracket below about 300 hp. This will take some time because
its successful operation requires a land-based service organiza-
tion to be built up and the philosophy of repair by replace-
ment to be established in the minds of ship designers and
users. The engine makers must assist to this purpose and they
must not expect too much from the side of the fishermen
themselves, who are seldom trained in this way of thinking.
Naval architects must also become better acquainted with the
characteristics of the automotive engine and design so that it
can be properly maintained and also removed from the engine
room completely when necessary. Machinery installations in
fishing craft have hitherto mostly been influenced by con-
ventional shipbuilding standards, but should also benefit from
[409]
the experience gained in the pleasure craft field. The future,
whatever the outcome, will certainly be most interesting to all
concerned with these questions.
Answering Traung: torquemeters for measuring of shaft
power are available and can be employed for experimental
purposes. Flowmeters in the fuel lines have been used in
Swedish MTB's as an additional check on the actual engine
output and have given good service.
Replying to Sinclair: Proper alignment of shafting is easy
enough, but as a matter of experience, correct alignment
would in practice seem to be the exception rather than the
rule, An elastic coupling is no excuse for misalignment but
can save the plant from expensive failures in case of mis-
alignments or movements of the hull. Such couplings are
usually considered only for an elastically-mounted engine, but
they are a recommendable safety device also when the engine
is on solid mountings.
Rubber exhaust pipes have been used in pleasure boats
with positive result, but of course it requires a wet system.
Keel cooling can often work with good result, but the reason
why engine manufacturers do not seem to favour them is that
they do not have control over their dimensioning and
installation.
To Campion on the question of life between overhauls:
while many engines might run for four to five years without
any need of replacement, it is quite often necessary to make a
major repair or overhaul after much shorter period of
operation. Selman and several other speakers have had bad
experience of rubber shaft bearings and would rather favour
white metal-lined bronze bushes. Rubber bearings are used
extensively in Sweden, both in pleasure boats and in naval
craft and have given good service. In remote countries their
replaceability might be less good, whereas a white metal
bearing can more easily be repaired with local resources.
HYDRAULIC DECK MACHINERY
Nakajima (Japan): Congratulated Vi brans and Bruttinger on
their paper. Nakajima designed hydraulic coupling and vulcan
gear about 20 years ago and so he was very interested in the
development of hydraulics for fishing boats. During the last
15 years, he has been studying this subject as a member of
a fishing machinery committee of the Japan Machinery
Association and he was pleased to see that the installation
of hydraulic equipment on fishing boats has remarkably
increased. He is specialized in the hydraulic equipment for
tuna liners and salmon boats, which were placed in practical
use about six years ago.
Equipment requires special control depending on fishing
gear, weather and fish conditions and the way of operating
boats. Nakajima is also studying the automatic regulation
system for speed and tension control, especially about
absorbing overtension or shock caused by longline. The auto-
tension system today available is not sufficient and should be
improved to prevent the flow out of fishing gear and saving
crew labour. Regarding the pressure of hydraulic equipment
which has been very much discussed, he thought it has to be
judged case by case, considering economy, safety and main-
tenance, etc. For boats less than 100 GT it is recommendable
to use hydraulic equipment not only for deck machinery but
also for propellers, and that will, he believed, raise the fishing
efficiency as well as that of operating boats.
Colvin (USA): Vibrans' and Bruttinger's paper is extremely
important for the development of hydraulic deck machinery.
It would seem that an area where hydraulic deck machinery
could be advantageous would be in those localities where
sailing vessels are still the prime vessel used for fishing. On
the Chesapeake Bay, the oyster dredges in Maryland are
operated from automobile engines as are the crab dredges on
the lower end of the Bay. This is primarily due to the unlimited
supply of wrecked automobiles. In areas where automobiles
are scarce, it would seem that with the small prime movers, an
economical hydraulic system could be used for a very minimal
cost. Colvin wondered if Vibrans and Bruttinger had any
occasion to investigate a small compact unit such as this for
use aboard sailing vessels.
Hydrostatic system?
Hatfield (UK): Complimented Vibrans and Bruttinger on a
very useful survey of hydraulic deck machinery. However, he
was surprised that they think so little of the possibilities of the
closed loop high pressure, or hydrostatic system in view of its
great advantages in efficiency, compactness and control
flexibility.
He quoted : "The closed loop system has limited application
to vessels under 100 GT. Most piston equipment is designed
to transmit powers greater than necessary for these boats.
Also the precision required for this type of equipment makes
the cost prohibitive. The requirements for a pump for each
hydraulically-powered deck machine increases the cost over a
system where one pump can supply several motors." This
statement completely ignores a whole field of work done by
Firth of NEL in the UK, and its subsequent wide com-
mercialization.
Regarding cost, this is of course dependent on availability
and would certainly be high if units had to be especially
produced. But it so happens that at least two firms produce a
whole range of high-pressure commercial pumps and motors,
of powers and torques ideally suited to powering the winch
of any 40 to 80 ft (12 to 24 m) seiner or trawler. These units
are so cheap that the complete hydraulic system including
tank, pipes, controls, boost pump, etc., is actually cheaper
than the present mechanical array of shafts, belts and gears.
Hatfield much preferred not to speak except in cases where he
could show hard tacts arising from service experience. This
is not so in this case, as the UK has been slow in applying
hydraulic to its fishing industry, to its own detriment.
However, the above-mentioned system is at present being
designed by the White Fish Authority into a 70 ft (21 m) seine
netter with a view to early sea trials. Hatfield thought that will
be found well worthwhile.
Some comparative experiences
Lerch (USA): Vibrans and Bruttinger have provided a very
interesting comparison between various transmission systems
for hauling fishing gear on small vessels. Most small vessels
have relatively little choice in the selection of transmission
systems because of such factors as location of the driving
device, local practice, local supply of materials as contrasted
with imported systems (sometimes under heavy financial
penalties imposed by duties) and/or lack of maintenance and
repair facilities.
It had been Lerch's experience that the transmission of
relatively high hp such as driving a main fishing winch, when
the transmission system is simple and direct, is least expensive
in installation and operating cost for mechanical system con-
sisting of chains, sprockets and line shaft or leather belts and
shafting. However, as soon as one attempts to drive remotely-
located equipment, such as auxiliary winches, vang winches,
anchor winches, portable devices such as powered blocks or net
haulers, a mechanical system may not only become extremely
more expensive but, in such cases as portable equipment,
completely impractical. Lerch agreed wholeheartedly with
Vibrans and Bruttinger concerning safety and control—both
of which are superior and much less costly with hydraulics
over other practical solutions for small fishing boats.
[410]
Power source
TABLE 11
Comparison of various power sources
Average Proportion*
weight/hp
in*lhp
Crew (long periods) (£355 or $l,000/year)
Crew (30 min) (£355 or $l,000/year)
1,800
300
250,000
62,500
4,300
715
12,000
2,000
High-speed diesels
27
350 400
18
50
1,800 rpm electric motors
25
1,500
9-16
25-45
Low-pressure hydraulic motors
11
800
14
40
Air motors — tolOhp .
8
315
33
95
Medium-pressure hydraulic motors
low hp (to 10) .
2
15
4
10
high hp (to 60) ... . l
7
1
4
TABLE 12
Comparison of air and hydraulic winch drives (winch: worm gear, 36
Driving motor Air
Motor weight . . 72 Ib (32.7 kg)
£210 ($580)
£37 ($105)
6.2
15 10
Motor cost
Valve cost
Rated hp
Dimensions (approx.)
13ft
1 reduction)
Hydraulic
21 Ib (9.5 kg)
£47 ($131)
£9 ($24.50)
7.8
6 -4 5ft
(380 ... 250 330mm) (150 - 100 - 125mm)
Table 1 1 compares the approximate weight, size and cost of
various power sources found on small fishing vessels and is
offered somewhat as an extension of Vibrans' and Bruttinger's
table 2. Comparisons of relative values are subject to a great
deal of individual controversy based on the reader's personal
experience and availability of materials. They do, however,
help to illustrate the desirability and general economical
superiority of hydraulic systems for the transmission of
medium powers, say from 5 to 50 hp, for powering miscel-
laneous gear on fishing vessels.
On a rolling fishing vessel most deck-mounted gear operates
under water at one time or another. Hydraulic motors have
proved to be the most satisfactory drives for rotating equip-
ment which will operate fully submerged. These can be close-
coupled to the machinery with watertight gaskets and thus
exclude all water from any rotating parts.
A comparison of air and hydraulically powered winches is
shown in fig 25 and 26 and table 12. Fig 25 is an air-powered
winch for mounting on an oil tanker where air was available
and explosion hazards existed. This is a modification of a
standard hydraulically driven winch, fig 26, shown installed
on a new tuna purse seine vessel and used for vanging the
main boom. It can be seen that the hydraulic drive is simpler
and more compact, and correspondingly less expensive.
Fig 25. An air powered winch for mounting on an oil tanker where
air is available and explosion hazards exist
Fig 26. Two hydraulically powered winches on a tuna purse seiner
McNeely (USA): Vibrans and Bruttinger have graphically
illustrated principles of modern hydraulics as related to
fishing vessels. Their paper will make excellent reference
material. The obvious intricacies portrayed in the paper
might, however, discourage rather than encourage the greater
use of hydraulics for fear of costly failure of delicate equip-
ment. Modern hydraulic engineering has provided excellent
equipment with a history of trouble-free operation. Docu-
mentation is needed of the reliability and ease of use by
inexperienced fishermen.
Practical evolution on tuna vessels
Izui (Japan): During the past 40 years the improvement in
performance of tuna longline haulers has been most remark-
[411]
able from four-stage-speed-control type to no-stage-speed-
control type, from driving shaft type to hydraulic type.
Japanese-type line haulers have been used in Formosa, Korea,
Hawaii, Africa and South America.
A 100 years ago the longline fishing boats in Japan were
not more than 6 ft (1.8 m) in width, the fishing gear being four
or five sets of line with 15 or 16 fish-hooks, operating in
coastal water two to three miles from shore. Fishing boats
became larger at the end of the nineteenth century and operated
in water 30 to 40 miles offshore . The introduction of powered
fishing boats in 1907 invited a marked progress in the fishing
boat building and related fishing techniques, which in turn
opened a way for unlimited expansion of the tuna longline
fishery.
In the old days the storage of tuna was either salting or
drying. The introduction of ice enabled the fishing operation
to stretch longer and also made possible the transportation
of tuna a longer distance. And the use of refrigerating machine
aboard fishing boats made it far profitable for tuna fishing.
In the early days of tuna longline fishing the loss of many
fishing boats at sea was inevitable because there was no
navigating instrument and weather forecasting was made only
by experience and sense. And of course there was no wireless.
A young widow of fishermen who never returned, stood on
shore praying to God that he was alive somewhere and would
return some day, brought tears to many onlookers, and once
the tuna longline fishing was called "widow-making fishing'*.
A line hauler for tuna was invented in 1923 to improve such
hard working conditions of fishermen. The specifications and
principal particulars for the standard line haulers are shown
in tables 13, 14 and fig 27.
Fig 27. A standard line hauler
TABLE 13
Specification
Model
Type
Height
Weight
Shaft
Winding speed
Required
Boat size
in (mm)
lb(kg)
rpm
ftjmin (m(miri)
hp
Special
6
59.2
885
250
high 690 (210)
10
Over 90 GT
(1,504)
(402)
low 460(140)
Large (standard) ....
4
55.3
(1,406)
620
(282)
250
high 590 (180)
low 384(120)
7.5
Over 30 GT
Large (lower) ....
3
49.5
616
250
high 590 (180)
7.5
Over 20 GT
(1,258)
(280)
low 394(120)
Medium
2
45.5
407
230
25 (75)
5
Over 10 GT
(1.155)
(185)
Small
1
32.0
233
200
21 (63)
2
Less than
(812)
(106)
10 GT
TABLE 14
Particulars (units: in (mm))
Type A
B
C
D
E
F
G
H
/
6 14.0
59.2
52.7
39.4
16.7
16.7
12.0
1.75
6.0
(356)
(1504)
(1337)
(1000)
(425)
(425)
(305)
(44.4)
(152)
4 13.3
55.3
49.3
38.8
14.4
14.0
10.2
1.5
4.5
(338)
(1406)
(1250)
(985)
(367)
(357)
(260)
(38.2)
(114)
3 13.3
49.5
43.4
33.0
14.4
14.0
10.2
1.5
4.5
(338)
(1258)
(1102)
(837)
(367)
(357)
(260)
(38.2)
(114)
2 10.5
45.5
40.5
31.1
13.5
7.2
9.4
1.1
4.0
(268)
(1155)
(1028)
(790)
(342)
(184)
(23o8)
(280)
(127)
1 8.3
32.0
28.1
19.4
11.3
6.0
7.8
1.0
4.5
(210)
(812)
(714)
(493)
(286)
(162)
(198)
(25.4)
(114)
Type J
K
L
M
N
0
P
Q
R
6 1.3
1.2
0.98
16.0
18.0
6.2
10.2
15.2
9.5
(32)
(30)
(25)
(406)
(457)
(157)
(260)
(286)
(240)
4 0.98
0.98
0.86
13.8
16.0
6.2
8.5
13.2
9.4
(25)
(25)
(22)
(350)
(406)
(157)
(216)
(33.5)
(238)
3 0.98
0.98
0.86
13.8
16.0
6.2
8.5
13.2
9.4
(25)
(25)
(22)
(250)
(406)
(157)
(216)
(33.5)
(239)
2 0.98
0.86
0.98
13.8
15.5
6.2
6.5
10.0
7.0
(25)
(22)
(25)
(250)
(294)
(157)
(165)
<%$
(178)
0.75
0.86
0.98
11.0
12.5
0.5
5.1
8.0
5.9
(19)
(22)
(25)
(279)
(318)
(12.7)
(130)
(201)
(150)
[412]
Particulars
TABLE 15
Particulars of pumps and motors for No. 6 type line hauler
High pressure
Low pressure
Type
Rpm
Pressure
Delivery volume
Oil pump
Plunger
1,450
2,100 lb/ina
(150 kg/cm*)
14 ft'/min
Oil motor
Plunger
Up to 400
2,100 Ib/in*
(150 kg/cm2)
57 fts/min
0/7 pump
Vane
370
284-355 lb/ina
(20-25 kg/cm2)
UJ ff3/mir»
Oil motor
Vane
Up to 330
284-355 lb/in8
(20 25 kg/cm2)
Input and torque .
Diameter of suction and delivery
Weight
(0.4 m'/min)
10-15 hp
0.75 in
(19 mm)
60 Ib
(27 kg)
(0.75 m8/min)
280 Ib ft
(39 kg m)
0.51 in
(13mm)
110 Ib
(50kg)
(0.315mVmin)
10-15 hp
2 in
(50 mm)
308 Ib
(140kg)
130-190 Ib ft
(18 26kg m)
2 in
(50 mm)
264 Ib
(120 kg)
MYO CYL.
/v s ^ / sss/ss/s
\. I
Fig 28. High pressure type hydraulic line hauler
When a line hauler is driven mechanically, by the main
engine, it cannot be operated at the right rpm as the rpm of the
main engine is subject to the change in boat speed. Lack of
deck space causes difficulties, and therefore the main engine
driving system has been changed to driving by motor installed
in electric motor room, then, again it has been changed to
electric motor-direct drive system. In the case of direct-motor
drive, planetary gear or chain reduction gear is installed for
reduction of rpm.
Hydraulic line hauler is classified into three categories: high
pressure type (more than J,7001b/in8 (120 kg/cm2)) (table
15, fig 28), medium pressure type (around 1,1 00 lb/in2
(80 kg/cm2)) and low pressure type (less than 700 lb/in2
(50 kg/cm2)) (table 15, fig 29) by the characteristics of
hydraulic pump and motor. A hydraulic line hauler can change
its speed quickly or be stopped by friction clutch against the
resistance of waves or fish or entangled long line.
Fig 28 shows the piping arrangement of this system as used
[413]
Fig 29. Layout and specifications of low pressure hydraulic line hauler
1. 15kw electric motor for hydraulic pump 5.6. 830 ft I win (252 m/min) 300 rpm hydraulic line hauler
2. 350 rpm hydraulic pump 7.8. 3.5t x 36 ft/min (II m/min) hydraulic windlass and It x
3.4. .08t x 92 ft/min (28ml min) hydraulic cargo winch min (12 m/min) winch
39 ft I
in Shinnan Maru No. 21 (111 GT). During the navigation it
does not require the operation of auxiliary engine and during
loading and unloading only the auxiliary engine will suffice.
Moreover, it can be driven by pump either from the main or
auxiliary engine and a small variation of rpm of the main
engine can be adjusted by discharge control valve that it is
possible to maintain the rpm of generator and refrigerator
constantly.
The float-line hauler is installed to pick up the float line
and the hauling speed is 280 ft/min (86.4 m/min), hauling
load is 1,750 Ib (800kg) and electric motor 2 hp, 220V,
1,900 rpm. The fish-hauling machine is designed to haul fish
easily. The hauling speed is 95 ft/min (28 m/min) and hauling
load is IJOOlb (500kg). This can be used as a windlass for
small tuna fishing boats. Branch line hauling roller can be
doubly attached to roller of line hauler, making possible the
hauling of the branch line at the same speed as the main line.
Baby haulers used
Baby haulers are used for small coastal fishing boats of 1 to
5 GT in which two fishermen operate with 50 baskets (one
basket = 623 ft (190 m)) or four fishermen with 70 baskets
and line is hauled at 165 ft/min (50 m/min). In the case of 50
baskets, it requires an hour for casting and three hours for
hauling. The machine weight is 62 Ib (28 kg).
The raising of hauling speed as much as possible to shorten
the working hours is desirable. At present the number of long-
line baskets has increased to 400 to 450 per boat with the total
length of long line being over 54 nautical miles (100 km). The
hauling speed is 200 ft/min (60 m/min) for the small type and
650 to 820 ft/min (200 to 250 m/min) for the large type. The
hauling speed has to be lowered in accordance with the
conditions of sea and fishing gear and angling ratio. As the
number of revolutions is fixed in the electric motor direct-
driven type, four-stage-reduction type and, later, no-stage-
speed-change type have been designed. A very slow speed is
necessary when lines are entangled. A sliding operation of
friction clutch is needed, but further on higher resistance
material for clutch disc and durable reduction gear structure is
desirable. The hauling speed should be so designed that it
does not give too much on long line and it can control slowing
and accelerating, depending on the movement of fish caught.
Hydraulic operation of line haulers makes possible the
change of hauling speed easily and ensures a proper speed, so
a great progress has been witnessed in the last several years.
In the hydraulic, there is a problem of high and low pressure,
but it should be judged from the standpoint of dependability
and safety, economy, maintenance of efficiency, convenience
in handling and installing and reduction in labour and working
hours. Because the operating speed of fishing machinery is so
slow, a major portion thereof is of low speed type. However,
with the development of geared engine, the trend is towards a
higher speed.
The main line is stretched a little below the sea surface and
[414]
it is subject to the heavy moving load by the resistance from
branch buoy lines, by the weight and amount of hooked fish,
as well as by the pitching, roiling motion and speed of the boat.
In order to haul the line safely with minimum tension and to
select line hauling angle for minimum resistance, research on
automatic operation of boats and automatic disposal of buoy
lines and branch lines are necessary.
Productivity can be ensured by maximum catch with mini-
mum labour. The line-hauling operation for tuna takes 8 to
12 hours and often it requires as long as 18 hours from line
casting to hauling. The navigation during this period is not
so easy. Unskilled navigation often invites loss, cut or
entanglement of line and the search of missing line and
straightening of entangled lines give a heavy burden on
fishermen.
Problem on small craft
Dugon (UK): On small fishing boats it is not often possible to
instal an electrically operated capstan or winch, as there is
insufficient generating capacity. The alternative drive for deck
machinery is mechanical or hydraulic. The control available
with a fixed or variable delivery pump system gives excellent
control, from "inching" to full speed in either direction, and is
comparable to that obtained by electric drives.
For economic reasons on small fishing boats, fixed delivery
pumps are normally used and as the hauling speed of the main
engine does not usually vary, this economic hydraulic system
is the best choice for this si/e of boat.
The basic power unit as illustrated at fig 1 9 of Vibrans' paper
is believed to be economical, and simple and cheap to instal.
However, if a standard automotive power steering unit is
used, this has certain limitations as to speed and drive,
especially with slow revving engines and the flow of hydraulic
fluid limits the si/e of winch or capstan which can be driven
from such a pump unit.
On small fishing vessels using hydraulic trawl winches it is
of great assistance to the fisherman to have an adjustable
relief valve and possibly a pressure gauge so that the maximum
pull of the winch can be adjusted to suit the type of fishing
and the state of the warps and nets.
Author's reply
Vibrans (USA): Three previous papers on hydraulics have
been presented at FAO meetings. These are: Hydraulic Deck
Equipment (Huse, 1955), Hydraulic Deck Equipment for
Research Vessels (Huse, 1961) and The Application of
Hydraulic Power to Fishing Gear (Lerch, 1964). The two first
give a thorough description of Scandinavian low pressure
systems developed for fishing boats and the last describes the
higher pressure system using equipment typical of that found
in numerous industrial applications. Both discuss fisheries in
Europe and America.
Aside from reviewing known hydraulic techniques, Vibrans
wished together with his co-author, to contribute an idea
useful to developing fisheries and this prompted the scheme of
the basic drive unit adaptable to several driven devices. It was
felt that an inexpensive drive could be made from a standard
industrial, shaft-mounted speed reducer with hydraulic motor,
close coupled to the input and a driving plate mounted on the
output.
Hatfield supported the closed loop or hydrostatic system for
deck machinery power and Vibrans agreed with the desirability
of variable displacement pumps in providing a system with
infinite speed control. Under current circumstances, he
believed his statement correct about the much higher cost of
closed loop hydraulic system for the deck machinery power
needed on fishing boats under 100 GT. He was acquainted
with some excellent high torque, slow speed, fixed displace-
ment piston-type motors, which are competitive in cost to
vane motors of equal output. Except in a properly designed
(and expensive) closed loop system these piston motors
cannot be used where overhauling might occur. The resulting
vacuum in the pump would hold the pistons away from the
driving cam, allowing the motor to run away, perhaps damag-
ing the motor components.
Lerch's comments were valuable, especially table 1 1 com-
paring the costs of supply "muscle" to fishing operations.
This material adds some useful data to this paper. While
agreeing with most of Dugon's comments, Vibrans believed
the basic system described in the paper did not need provision
for manual pressure adjustment or a pressure gauge. The
operator of small deck machinery is interested only in "does
it work".
The virtue of the automotive power steering pump aside
from its low cost, is its almost uniform delivery irrespective of
input rpm. Manual adjustment is not necessary as the built-in
flow control valve automatically recirculates the fluid pumped
in excess of the rated quantity. The curves in fig 30 illustrate
typical performance of a popular US built automotive steering
unit which is a type suited to the basic system.
Fig 30. Typical composite delivery characteristics
FISH KEEPING ON SMALL CRAFT
Ranken (Spain): The main purpose of every fishing vessel is
to land the maximum quantity of fish with the minimum
expenditure of labour and commanding the best possible
price. The vessel must therefore be built not only to catch fish
as efficiently as possible, but also to preserve its quality in a
state as close as possible to that at the time of death.
Fish handling on board large vessels has been revolutionized
in the past 20 years by the introduction of the shelter deck
stern trawler, in which fish preparation and processing can be
completely separated from the catching operations, net
handling, mending, etc. This separation, however, becomes
increasingly difficult the smaller the size of the vessel, and the
best that is possible is to provide as much working space as
possible in the hope of achieving a fair measure of segregation
of the catch from the gear.
In the smallest vessels, no fish preparation is done on board
since labour is insufficient and the time at sea is in any case
very short. Some measure of preparation and washing is
however done, depending on variety, the larger the vessel and
longer the voyage. In all handling offish in the fresh state, the
maximum amount of care possible should be taken over
hygiene and in this respect the boat designers have their part
to play in using hygienic materials like aluminium alloys and
in providing liberal supplies of clean sea water for washing
the fish and the working spaces. Good and unobstructed
drainage is also important to avoid accumulations of decaying
material.
[415]
Equal attention to hygiene is necessary in the fish holds and
aluminium alloys for stanchions, pound boards and linings
are undoubtedly a worthwhile investment. Where boxing is
used, aluminium boxes are probably more durable than plastic
ones, although there has been good experience with the latter
in some French ports. The possibility of using aluminium for
chilled water tanks is also worth considering, though steel
tanks are satisfactory if properly cleaned and preserved
between voyages.
Importance of ice
The primary method of preserving fresh fish is in melting
ice and the proportion required varies from about 50 per cent
by weight in the Arctic distant water fisheries to 100 per cent
in tropical waters. The quantity of ice required can be reduced
by improved insulation of the fishroom to reduce the rate of
heat leakage, with or without the assistance of a small
refrigerating plant to remove this heat. The actual cooling of
the fish must however be done by the ice, which also provides
melt water to keep the fish surfaces clean and moist. With good
icing it is possible to obtain even fish temperatures between
32 and 34° F (0 and 1.1° Qf and some fish will reach an
equilibrium at about 31° F (- 0.5° C). For white fish the maxi-
mum time in ice is about 16 days and the figures given by
Chigusa presumably apply only to tuna and similar varieties.
If sufficient cooling is done by refrigeration to assist the ice,
some freezing will certainly occur. This may be acceptable as
in the Portuguese fisheries, where so-called "superchilling"
to 28.4° F (-- 2° C) is standard practice and allows Mauritanian
ash to be landed in good condition certainly up to 25 days old
and perhaps up to 35 days. This method, however, requires
more refrigeration than would be acceptable in most very
small boats and is not therefore considered applicable to
vessels below about 130 ft (40 m). Where superchilling is not
acceptable, the cooling system must be arranged to avoid
contact between the fish and the cold pipes, since the latter
must of necessity work at temperatures far below the freezing
point of fish. Normal practice has been to use grids on the
deckhead only with, in some older steam vessels, further grids
buried in the insulation of the bulkhead adjacent to the boiler
room. In part-freezer vessels, such as Lord Nelson, no trouble
has been experienced with freezing of wet fish adjacent to the
frozen fish hold, since the fish is always properly iced.
A difference in practice
The stowage rates given by Chigusa do not correspond with
British practice where 32 lb/ft3 (510kg/m3) is standard for
bulking on account of the high proportion of ice used. On
the other hand the normal figure for chilled sea water is
45 lb/ft3 (720 kg/m3). However, it is thought that Chigusa's
figure of 32 to 37 lb/ft3 (510 to 600 kg/m3) for tuna is prefer-
able for brine freezing to the normal US figure of 45 to
50 lb/ft3 (720 to 800 kg/m3); this latter figure is also quoted
by Doke and Chigusa (1960).
Chilled sea water is of course a well proven method in the
USA and Canadian West Coast salmon and halibut fisheries
up to about 16 days and Chigusa confirmed its suitability for
tuna. The method has not found much application elsewhere,
presumably due to the ready availability of cheap ice from
shore as compared with the comparatively large refrigeration
plant needed on board to cool the sea water and fish. Hygiene
is also a considerable problem.
In all vessels the hatch sizes should be kept as small as
possible to reduce the inflow of warm air, but large enough
for the rapid discharge of the fish without damage. Some
designs of small vessels are bad in this respect making
preservation difficult.
In some small ships the refrigerating compressors have been
coupled to or belt-driven from the main engine, sometimes
using a magnetic coupling, thermostatically controlled. Other
vessels have used electric motors obtaining power from a
battery. There may well be cases where a thermostatically
controlled hydraulic drive obtaining pressure from a pump
driven by the main engine would be attractive, especially if
the pump also drove the winch and perhaps other auxiliaries.
For wet fishing vessels there appears to be very little in
favour of using ammonia as the refrigerant and Refrigerant 12
seems a better and safer choice. The problem of leaks can be
largely overcome and for the most part smaller compressors
can be used running at higher speeds. No difficulty is
experienced with Refrigerant 12 condensers and other items
may also be easier.
Varied methods for different fish
Freezing on board small vessels is limited to certain
fisheries and the methods used depend on the varieties of fish
involved. Brine freezing is limited to tuna, sardines and
possibly shrimps. Blast freezers occupy too much space in
relation to hold capacity, but so-called sharp freezers are
possible in some cases, such as lobster and tuna boats. Plate
freezers especially of the vertical type may well be the best
choice in small ships to save space. Frozen produce will last
almost indefinitely at -13° F (-25° C) or below, but higher
temperatures are not recommended for any variety even for
short-term storage.
If freezing is adopted it should be the aim to land a product
which, on thawing, competes fully with really fresh fish. This
is now easy with modern methods, but careful handling and
even temperatures are still essential at all stages.
The cooling surfaces quoted by Kazama (in his paper on tuna
longliners in the last section of this book) from the Japanese
Government Fishing Boat Inspection Regulation for semi-
blast freezers appear very small in relation to the cooling loads
stated, unless much higher heat transfer coefficients are
achieved than one would normally expect; the cooling loads
themselves do however appear very high in relation to freezing
capacity. On the other hand, the surfaces specified for the
holds seem unduly high in relation to cooling load; the loads
themselves are also high unless a lot of product cooling is done
in the hold. It would be valuable to have Kazama's comments
on these points.
It is interesting to hear that Japanese owners still continue
to prefer ammonia to the safer refrigerants. This is in line
with USSR, Polish, USA, Greek, Italian and other experience.
It would be valuable to have Kazama's or Chigusa's comments
on whether there have been any accidents with ammonia and
directly attributable to it. A recent explosion in a small
Spanish fishing vessel caused initially by a serious leak
followed by an electrical spark, draws attention once again to
the hazards, especially as a fatality resulted.
West European experience is now centred on Refrigerant 12
or Refrigerant 22 systems, often with pump circulation
through the freezers, and sometimes combined with brine in
the holds of the larger vessels. Two small ships now building
for octopus freezing employ Refrigerant 22 pump circulation
through the holds as well as through the freezers.
With a few notable exceptions like tuna, shrimps, lobster
and octopus, freezing at sea does not appear to be an economic
proposition in small vessels much below about 130 ft (40 m),
on account of the large amount of space occupied by the
refrigerating machinery to the detriment of hold capacity.
Brine or blast freezing?
Gianesi (Italy): Kazama's paper posed the question of which
freezing system — salt brine or air blast — is to be preferred on
[416]
-* i i I M I I 1 I
M •> II' ! i I *-f- ! i 1 i I i - 1 -Mill! ' *"•* -+
30 30 40 45 50 55 60 65
70
75
80 85
V
V
I
"~*^ T^Tr**'T<v<?*'fl'*r*
FREEZER 1
FREEZER 2
27'- II" (8.50m)
^
PRECOOLING "L
ROOM
H-O^- (fi'^h
31'- 2" (9.50m)
. Layout of pre-cooling room, freezing room and fish hold
[417]
board of tuna longliners, both from the point of view of the
product's quality as well as regarding the necessity of reducing
manual labour. There is no doubt that the increasing market
requirements, together with the experienced reduction of the
catching rate and consequent increase in the length of fishing
trips and expenses, bring to a paramount importance the
necessity of reducing manual labour on board and of obtaining
the best frozen product.
As reported by Kazama, freezing by brine immersion is a
simple process and requires little work, but it is not considered
the best system from the point of view of quality and market
price; with this system there is no way of substantial improve-
ments without a corresponding increase of processing expenses
for protecting the product.
The more frequently used semi-air blast freezing system on
shelves gives better quality products but requires a heavy
manpower. This system with the increasing claims of crews
could create some organization difficulties. However, at
present the answer to Kazama's question can be given by the
results obtained in the manpower savings and product quality
by the air-blast freezing plant that was installed some time ago
on Marefish of 1,650 GT.
The installations on the Marefish were conceived according
to its operational requirements as mothership, with a freezing
capacity of 40 tons daily of tuna ; they can, however, be pro-
portioned without any difficulty for smaller capacities as well
as for medium-sized tuna longliners of 500 tons. They consist
(fig 31) of a pre-cooling room on the working deck, of two
(or more) blast freezers following the pre-cooling room, of a
conveying system of the tuna to be frozen from the pre-
cooling room to the freezers and from there to the hatches of
the holds and finally of a two-stage refrigerating plant capable
of obtaining freezing temperatures of -40° to -50° F (-40°
to -45° C).
It is a peculiarity of the system that the tuna are pre-cooled
and frozen in air streams which allow a radical reduction of
labour and, more important, a substantial improvement of
the product's quality. In fact, the complete process from the
time the tuna beheaded and gutted are brought in the pre-
cooling room until the moment they are unloaded in the
refrigerated holds, they move suspended on rails, thus
reducing the number of people required to operate the process.
It also eliminates heavy work and the tiring necessity to load
and unload the tuna on the shelves: the latter are eliminated
and replaced by low temperature air coolers; the freezers are
free of the present heavy structures, thus being much cleaner
and clearer; the refrigerant charge is reduced and defrosting
is easier.
The said system is particularly suitable for longliners; tuna
are hung singularly or in groups, depending on the size. The
hanging system is very simple and does not bring any damage
to the fish or alteration to the skin. Tuna is frozen round and
uniformly and it was noted that its meat was clearer, a thing
which is appreciated on the market. This is obviously due to
the fact that products are processed in a vertical position.
The space required by the freezers is not larger than neces-
sary with a semi-air blast system on the basis of equal daily
capacity. The volume of the Marefish freezers is about
9,000ft3 (250m3) against the 11,200ft3 (317m3) indicated
for the same capacity in table 4 in Kazama's paper.
An ante-room or pre-cooling room is necessary, but not
strictly of the dimensions shown in fig 26 of Kazama's paper.
Its size should be proportioned to the average catch rate and
should give enough space for the rails providing the necessity
to allow an easy conveyance to the freezer and a quick unload-
ing in the holds.
The described freezing system reaches its final working
temperatures of -40° to -50° F (-40° to -45° C), i.e. well
lower than the ones usually reached with the semi-air blast
system and requires a well calculated air flow which could
result bigger than the one usually applied in the shelves.
However, regarding working temperatures, Kazama seems to
agree, too, that also in the semi-air blast systems, lower
temperatures should be obtained to improve the quality of
frozen tuna products. Obviously, these temperatures require
thicker insulations and a two-stage refrigeration plant.
There are no difficulties both on the installation and opera-
tional points of view to realize these plants with ammonia or
Freon 22 systems, if requested.
Fig 32 shows the Marefish compressor room. Besides, the
two-stage system has a higher efficiency which offsets the
larger ventilating power eventually required.
Fig 32. Compressor room of Marefish
Freezing times do not present substantial differences with
the semi-air blast freezers (Gianesi, 1963) and depend
obviously on the size of tuna. For example, with tuna of
175/220 Ib (80/100 kg) freezing times were 18/20hr on pro-
ducts not pre-cooled and 12/14 hr on pre-cooled ones, which
substantially agrees with theoretical calculations (Levy, 1958).
It has been noted that a well proportioned pre-cooling room
assures to the installation a production flexibility which could
be appreciated in case of unusual loading conditions. There-
fore, it could be said that the experiments and the fishing trips
made to date have proved the reliability of the described
freezing system, both as regards labour reduction as well as
the quality of the product obtained which was truly appreciated
on the market. As a result, some new fishing vessels and a new
group of tuna longliners of 600 GT (see fig 33), presently
being built with refrigerating plants in Italy, will be equipped
with the said freezing system.
Ando (Japan): Thanked Gianesi for his discussion. The
explanation about two-stage systems of freezing applied in
1,650GT ships is very useful to shipbuilders in Japan,
especially applying to middle tuna ships such as 600 GT is
very interesting and Ando hoped Gianesi will show him the
details of the ship.
[418]
Fig 33. One of the new 600 GT tuna longlinerx equipped with
air-blast freezer systems
Well established Canadian method
Harrison (Canada): The use of refrigerated sea water as a
cooling medium for salmon has become well established in
British Columbia in the transportation of salmon from the
fishing grounds to the canneries. The vessels so equipped are
known locally as "packers" and the sole function is to trans-
port or "pack" the fish from collecting points on the grounds
to the canneries. This change has come very suddenly. The
technique was experimented with on a commercial scale in
1955. However, it was not until 1961, with the conversion of
the vessel Western Express that the usefulness of this system
was commercially demonstrated. This vessel established a
pattern for all future installations in so far as the refrigeration
and mechanical equipment is concerned.
Refrigerated sea water is primarily a substitute for ice. The
means of employing it is extremely simple. The fish are held
in watertight tanks built into the vessel. The tanks are flooded
with sea water and the sea water is recirculated through heat
exchangers maintaining a temperature within T F (0.5° C) of
the freezing point of sea water. The water is not normally
changed throughout the holding period.
Although there are some improvements in quality of fish
possible with this technique over the best of icing practices, its
main advantage lies in the rapid application of refrigeration
to large quantities of fish. Loads of the order of .5 million Ib
(225 tons) may be taken aboard in a single day by a crew of
six men. Because this is its main advantage, the technique has
found little other application in the British Columbia fishing
industry. It has been used successfully in the halibut fishery,
but here the problems of the more sophisticated equipment
offset any other practical gains.
The use of this system will perhaps always be restricted to
applications where the main problem is the immediate
refrigeration of large quantities of fish. It is now used in the
California sardine fishery, the US Atlantic Menhaden fishery
and in the US tuna fishery, where refrigerated sea water has
always been the first, or chilling, stage of brine freezing.
The packer is capable of carrying from 150,000 to 500,000 Ib
(70 to 225 tons) of fish. The vessels have all been conversions
of former small naval craft. All are of wooden construction.
The holds are divided in three to six tanks. Longitudinal bulk-
heads are avoided because of difficulties in unloading narrow
tanks, however, they became mandatory in larger vessels.
Equipment described
The first step in tank construction is the rearrangement of
piping, wiring and mechanical apparatus in the hold, to either
make future access unnecessary, or available via removable
access panels. Bituminous paints are applied to all existing
structure. Framing follows this preparation. It is in general
simply the application of furring strips to the complete hold to
clear bolthcads, brackets and piping; and to provide nailing
surface for all plywood edges.
Vertical bulkheads are installed usually framed up from
2 x 8 in (50 x 200 mm) studs with cross blocking to pro-
vide nailing surface. Laminated solid bulkheads have also
been used, built up from 2 x 4 in (50 x 100mm) material.
Although more material is required, lower grades can be used.
With this construction the problem of nailing surface is simply
solved and a substantial saving of hold volume results.
Plywood is next applied usually in two layers of marine
grade Douglas fir plywood in J or i in (10 or 12 mm) thick-
ness depending on curvatures encountered. The reverse sides
of the first layer are pre-painted and set in with bedding
compounds. The sheets are then nailed to the framing with
galvanized nails. The second layer of plywood is glued to the
first with urea-formaldehyde glue. All butt joints are staggered
with relation to those of the first layer. Special attention is paid
to the gluing of joints. Nailing of this layer is with monel or
everdure ring-nails. Fibreglass and polyester resin is applied
to all corners and in many installations the whole plywood
surface. Where fibreglass has not been used, thiokol paints
have been used as the final coating. Both treatments have
given excellent results to date.
Before dealing with refrigeration equipment, the require-
ments of the refrigeration system will be set out. First, the task
at hand is the cooling of large quantities of fish from high
temperature, 70f F (2T C) to near the freezing point of sea
water, 28.5U F (-2° C). It is necessary and difficult, to think
of cooling and not the maintaining of low temperature as the
refrigerations task. The quantity of refrigeration required for
cooling is about 20 times that required for the daily main-
tenance of temperature.
Because of this comparatively small refrigeration load for
offsetting the heat leak, insulation is dispensed with as the cost
and complications of insulating wooden vessels, so as not to
encourage rot, are not warranted. Neither is there any need
to insulate to limit temperature fluctuation; as the thermal
inertia of the large mass of fish and water is so great that in
practice, temperature rise of a tank at holding temperature
would be only about 1°F (0.5° C) per 24 hours with the
refrigeration not operating. The ratio of refrigeration capacity
to fish carrying capacity has become established at about one
ton of refrigeration to four tons of fish. The other require-
ments of the refrigeration system are that it be compact, simple
to operate and dependable.
Source of power
High speed, lightweight diescls have been used as the source
of motive power for all installations for many reasons. First,
perhaps, is that diesel fuel is already aboard for the main
engine. Engines of the size required here, about 50 hp, are
common, cheap and compact for their size. The engineers on
these vessels are quite familiar with diesels whereas electric
motors which are usually employed in marine refrigeration are
outside of their competence. Efficiency is also a consideration
as opposed to electric drive, not in so far as fuel costs are
concerned, but because of the cost of equipment, whereby a
diesel driving an alternator would have to be much larger to
offset the losses in a motor generator system. The power
characteristics of diesel lend themselves to this application, as
they can provide high starting torque and cope with overloads
of a few hours' duration.
The mechanical and refrigeration equipment selections and
arrangement have become almost standardized for both
[419]
02
refrigerated sea water and brine spray freezing or combination
applications. The heart of the unit is the compressor which is
V-belt driven from the diesel, the only other mechanical units
are the sea water circulating pump and the condenser cooling
water pump.
The compressor is a four-cylinder, l,800rpm, 30-ton unit.
It was most fortunate for this development that compressors
of this type had been developed for the needs of the air-
conditioning industry, just prior to it. The machines give a
very high refrigeration output for their size and were designed
primarily for operating in the same temperature range. Their
general use in air conditioning has also made them and their
replacement parts readily available. In the same way, servicing
facilities and personnel are to be found in cities everywhere.
This type of compressor is equipped for either V-belt pulley
or axial drive, most units being driven by V-belts. V-belt
drives permit a greater choice of location in ships' engine
rooms. This factor is important with ships in British Columbia.
Most installations have been in existing vessels where little
space is not already occupied. In new constructions here it
has been equally important as the emphasis in design has been
for a maximum hold space, leaving a minimum engine room to
accommodate an ever-increasing array of equipment.
Although the V-belt drive is not insensitive to misalignment,
it is less critical than with an axial drive. This is perhaps
unimportant in the initial installation. However, it is a factor
in realignment later following repairs or moving of the
equipment which may be done at sea or by less skilled workers.
Specially designed chiller
The chiller used to cool the sea water had been designed
expressly for this service by Harrison and his collaborators at
the Vancouver Technological Station of the Fisheries Research
Board of Canada. It is basically a dry expansion shell and tube
heat exchanger of the type now commonly used in air con-
ditioning, but with important changes for this service. Here it
must operate with the refrigerant in the tubes, below the
freezing point, and cool water to freezing point, while entering
at a temperature only 1" F (0.5° C) above freezing. Further-
more the exchanger must pass water heavily contaminated
with blood, slime, scales and other debris.
In the installation described, the chiller is comprised of
seven identical elements. Each element has a 10ft x 6 in
(3m x 150mm) diameter shell of polythene pipe. This
material was selected for its low cost, availability, resistance
to sea water corrosion and its ability to yield without rupture
should the heat exchanger inadvertently freeze up. The tube
bundle consists of twenty-four $ in (16 mm) diameter copper
tubes arranged in six refrigerant circuits of four 9.5 ft (2.9 m)
tubes each connected by U bends. The spacing between tubes
is | in (9.5 mm). Semi-circular baffles of sheet brass are spaced
at 6 in (150 mm) intervals.
All refrigerant connections are made at one end of the
chiller to enable removal of the shell without disconnecting
refrigerant lines.
It should be noted that copper tubes have been used here,
despite not being highly regarded as a heat exchanger tube
material for marine service. The original of these chiller
elements is still in service after ten years. It appears that the
low temperature accounts for the resistance to sea water
corrosion.
Each chiller element has one thermal expansion valve with a
six-orifice distributor for metering refrigerant circuits.
Refrigerant isolating valves have been used on each chiller
element for the purpose of isolating a faulty chiller from the
system. The system will operate quite well with one or even
two chillers not operating. However, experience has shown the
chillers to be more reliable than the valves; and it is believed
that any future installation should be without isolating valves
on individual chiller elements.
The chillers are racked horizontally one above the other,
usually on an outside deck house bulkhead. Sea water connec-
tions between the chillers and inlet and outlet manifolds are
made with automobile radiator hose and clamps to provide
the required union.
Circulating pump
The circulating pump used is a 3-in (75 mm) all iron open
impeller centrifugal pump delivering 500gal/min (415 Imp
gal/min, 1 ,900 1/min) at 40 ft (1 2 m) head using 10 hp. The pump
is located when possible below the level of the tanks to
eliminate priming problems. When this is not possible, hand-
operated diaphragm primers are used.
Where possible pumps are V-belt driven from the com-
pressor engine without a clutch. This economical arrangement
is dependable and foolproof as the pump will always be in
operation when the compressor is operating. Where such a
drive cannot be used because of engine room limitations,
electric drives are employed. Vertical electric pumps are used
as they simplify making suction connections at the lowest
possible level in the ship and require a minimum of floor
space.
Starting point of the circulation system is the suction screen
in the hold. This must be very substantial to withstand the
pressure of the fish and the total surface must be very large
since it is blocked off by the fish themselves, leaving a very
small proportion in operation. They are located across the
corners of floor and bulkhead in most cases or covering a floor
gutter, or both if possible. About 1 ft2 per l,0001b (0.1 m2
per 500 kg) of fish capacity is required.
A section of screen is also extended from the main screen up
a vertical bulkhead to provide a suction pressure relief and
water bypass to guarantee water flow to the chillers in event
of blockage. This is necessary as the vacuum which can be
induced by the pump can give even greater pressures on the
screens than the effect of the weight of fish. Screen material is
usually galvanized, expanded metal from 12 gauge stock with
J in (19mm) nominal mesh. Supporting of the screen must
be adequate to support the drained weight of the tank full of
fish.
Some trouble with screens
Screens have been the only source of serious trouble in
refrigerated sea water systems. One solution is to arrange for
the reversing of circulation, that is from bottom to top.
Unfortunately, it is necessary to have top to bottom circula-
tion to permit operation with part full tanks which is practised
during loading in protected waters. Reversible piping is too
costly except for small vessels, where it has been used with
good results.
A new technique has been tried in the past year with
excellent results. Suction screen was applied to one vertical
bulkhead only, covering the whole bulkhead except for about
3ft (0.9m) at the bottom. Water is admitted through a
perforated distributor pipe along the bottom of the tank. In
this system, the effect is that the fish will plug this screen
forcing the flow up through the fish and over the top, then
through the screen and down the bulkhead to the pump suction
pipe. The water does not short circuit through the screen as
might be expected and temperatures throughout the tank have
been uniform.
The major consideration in piping is sanitation. All piping
should be arranged to eliminate pockets where debris can
accumulate and the circuit should be such that all lines can
be flushed overboard from the sea cock. This is not always
[420]
possible because access for valves is sometimes only in the
engine room, necessitating lines to the tank which cannot be
flushed. Provision should also be made for valving all piping
into a closed loop and providing for the injection of cleaning
and disinfecting materials which can be circulated in the sea
water cooling and distribution system. In this way, heavy
concentrations of these materials can be used, which can
search out the crevices in the system.
Polythene pipe is preferred regarding corrosion, sanitation
and thermal conductivity. However, as most piping is exposed
to mechanical damage, little can be used, thus galvanized iron
pipe becomes the usual material. Butterfly valves are preferred
for all sea water valving, because of their compactness, clean
lines and simple operation,
Pipes and filters
Filters should be employed in the system to protect the
chiller from debris. As the space between chiller lubes is 8 in
(9.5 mm) filter mesh must not exceed this. About 5 to 10ft2
(0.5 to 1 m2) of filter screen must be used. Arrangement must
be made for backflushing overboard by means of reverse flow
valving or by reversing the screen.
A marine, cleanable, shell and tube condenser is used. Tubes
are cupro-nickcl. Water passes through the tubes, which can
be cleaned by removal of the water heads. The outside or
refrigerant side of the tubes is finned, resulting in a very
compact condenser, dimensions being 8 in (200 mm) diameter
by 9ft (2.75m) long. This represents one of the major
advantages of the use of freon refrigerants over ammonia in
marine applications.
A straight centrifugal pump is used where no problem of
priming is encountered. Where a self-priming pump is used,
rotary, rubber-impeller pumps have been used with excellent
results. Water requirements are about 70gal/min (60 Imp
gal/min, 265 1/min) at 40 ft (1 2 m) head. The preferred drive for
condenser pumps is directly by V-belt from the diesel. In this
way cooling water through the condenser is started ahead of
engagement of the compressor, clearing the condenser of warm
water. Electric motors are used where a remote location of the
pump is desirable.
Manual rather than automatic control is employed. As the
refrigeration system tends to operate for long periods of time
under only gradually changing conditions of load, automatic
operation is not desirable. Temperature is maintained by the
manual starting and stopping of the compressor. The only
operation required during running is control of condenser
water to maintain condenser refrigerant pressure within the
required limits. This is done by throttling waterflow from a
centrifugal pump, or by-passing water round the condenser
in the case of rotary pumps.
Automatic alarm devices are employed to warn of low
refrigerant suction pressure, high refrigerant condensing
pressure, low compressor oil pressure and high pump sea
water pressure. These are preferably tied to the engine oil
pressure and cooling water temperature alarms and shut
down. Signal lights are employed to indicate the cause of
shutdown. In this way, temperature of the sea water is auto-
matically, although indirectly, controlled in so far as reaching
the low temperature is concerned. The restarting of the equip-
ment when again required is always a manual operation.
This same equipment is used without changes of any kind
in the brine spray freezing of tuna. The only differences in
operation being that the sea water is fortified with salt to
permit its being cooled to about 20° F (— T C) and the brine
inlet is arranged to provide a spray throughout the hold by
means of perforated piping on the deckhead. Units of this
size have been found satisfactory for vessels carrying about
120 tons of tuna.
This equipment is well suited to fishing vessels as there is
no refrigeration equipment located in the holds and the
compactness of the equipment presents few problems in
locating it in the vessel. Recently much of new construction of
larger fishing vessels in British Columbia has been of vessels
with this equipment for use as combination refrigerated sea
water packers and brine spray freezers.
McNeely (USA): Chigusa has contributed a most valuable
paper which will be useful to small boat operators throughout
the world, in particular those in tropical or semi-tropical
latitudes. Refrigerated small vessels might be feasible,
however, only when high-valued fish, such as tuna, are taken.
Sapre (India): In Gujarat State, India, most of the prime fish
caught is sent to Bombay which is about 200 miles by sea.
The fish is sent in iced condition by fish carrier vessels which
have insulated fish holds. It is likely that refrigerated holds
may be needed in the future.
Chigusa's paper explains various refrigeration systems in
small fishing boats. It would be very useful if the type and
voltage of electric supply used is given. It is also essential to
know the costs of the refrigeration units, particularly in
respect of 20- and 40-ton vessels.
Catch, transport and market
Waterman (UK): A fishing vessel has three duties to perform:
• To convey crew and gear safely, speedily and in com-
fort from port to the fishing grounds and back again
• To make the task of working the chosen gear as easy
and efficient as possible
• To store and transport the catch from the grounds to
the port
This last function is as important as the first two, and
cannot be divorced from them when the vessel is being
planned. In developing countries fishermen and craftsmen are
learning new skills. More often than not, the picture that is
conjured up is one of warm water, blazing hot sun, primitive
communications and distant markets; it is essential to bear
in mind the quality of the catch and its preservation from the
moment that a new fishery or a new vessel is first conceived.
Preservation is not solely the province of those who are
fish technologists; care of the catch is very much the concern
of every naval architect, builder and vessel owner. Questions
such as "how much insulation, if any?", "what method of
storage?**, "what refrigeration system?'*, "shall I carry ice?"
must all at least be posed and, in most cases answered before
a single line is drawn and certainly before the keel of a boat is
laid.
On the method of handling and storage and the means of
preservation, this will depend on not only the equipment of
the vessel, but also the basic specifications of the ship itself;
proper division of available space between engine room and
revenue-earning capacity; power demand of chilling or
freezing plant, form of the hull to make the best use of the
space available; shape and size of hatches for efficient stowage
and discharge, etc.
What materials are most suitable for fishroom construction,
what mechanical handling aids are justified, how big must the
vessel be before refinements of this kind are economically
justifiable? How long do trout, tilapia or turtles keep in ice
compared with their shelf life at 80° F (27° C) in the shade?
How much space will they occupy ?
It is not good enough for a prospective vessel owner to pick
a method of preservation with a pin and then for the builder
to think up a little something that might do.
Waterman wanted to quote from a typical, but apocryphal
letter: "Dear Sir, I am recently purchasing a magnificent new
[421]
fishing vessel. I shall catch plenty big tuna and want to put in
ship a freezing plant, cold store and offal reduction plant;
please advise me on best equipment to buy for very good
keeping of fish. P.S. My boat is 40 ft (12 m) long and has a
very fine sail." This letter is not so ridiculous as it sounds, and
at least the writer had the initiative to ask for advice before
plunging recklessly.
Seriously though, Waterman wanted to appeal for more
co-operation, at a very early stage, in all fishery development,
between designers, builders, engineers, operators and fisheries
technologists, so that vessels are built to fulfil their three
functions as efficiently as possible; there is no need for high-
speed, soundly-built offal producers. After all, someone's got
to eat that fish caught, and although good quality may not
always mean more money, it usually helps!
Spanish experience
Gueroult (France): Chigusa's interesting paper stated that fish
can be kept fresh in chilled water as much as 30 days. Trials
on the Spanish and African coasts point to a period of
approximately eight days. Thus these are results from
experimental findings in two widely differing cases. The length
of trip and operational range of a fishing boat are governed
by the time the catch will keep. The specifications of a boat
are so dependent on the range that there must be an agreement
on the matter of "keeping time" so that there must be an
explanation of the differences they record. It is possible that
cold-water and tropical fish do not keep for the same length
of time.
Nickum (USA) : Referring to Chigusa's paper, the fish capacity
is given at 32 to 37 lb/ft3 (510 to 600 kg/m3). The storage
capacity for tuna in the USA is somewhat more of the order
of 50 lb/ft3 (800 kg/m3). But this may be because the product
goes straight to the canneries and fish appearance is not vital.
Fujinami (FAO): Gueroult mentioned that the duration of a
trip to be able to preserve fish is quite different in Europe and
Japan. In Europe the maximum duration is eight days in
comparison to 30/40 days for Japanese tuna boats, and this
may be because of the difference of quality of fish required in
the market.
The Japanese market requires extremely high-quality fish,
especially tuna fish, as they wish to eat it raw. In Rome, it is
often difficult to find high-quality tuna to eat raw.
Fujinami had discussed the matter which Chigusa and they
could not understand why such a big difference of possible
duration is possible. This problem should be further studied
to find the real reasons.
Author's reply
Chigusa (Japan): Long voyage is necessary for Japanese
fishing vessels because the fishing grounds are distant and it is
difficult to understand for Japanese, why the duration of a
fishing trip of European fishing vessels is so short. If a freezing
hold and a normal refrigerated hold exists together, fish in the
normal refrigerated hold are half frozen and deteriorated.
The hold used for both fuel oil and fish can be cleaned easily
by washing the hold with sea water so that it can be used as a
fish hold after being used as a fuel tank. Fish can be kept fresh
for 40 days in chilled sea water.
[422]
PART V
DESIGN OF SMALL BOATS
Developable Hull Surfaces . . , Ullmann Kilgorc Arctic Fishing Vessels and their Development
Kjeld K Rasmussen
Dug-out Canoes and other Indigenous Small Craft ^ ^ . WT „ ,„ . . ^ .. „ f
A J Thomas The Advantages and Uses of High-speed Fishing Craft
John Brandlmayr
Fishing Boats for Developing Fisheries . . P Gunner Discussion
Developable Hull Surfaces
by Ullmann Kilgore
Surfaces de coque d£vcloppablcs
Du point de vue tant de I'economie d'utilisation quc du rendement,
les bateaux de pdche modernes doivent etre a coque metalliquc,
mais ce mode de construction demande un outillage couteux ct
cntraine de gros frais de main-d'oeuvre, a moins que la surface dc la
coque ne soit developpable. La communication expose, au moyen
de th6oremes originaux, les proprietes fondamentalcs des surfaces
developpables, en vue d'etablir des methodes graphiques simples.
Celles-ci sont valables en principe pour toutcs les surfaces develop-
pables, et ne dependent pas de la nature particuliere de tellc on telle
categoric de surfaces.
Superficies desarrollables de cascos
A efectos dc economia y cficacia las embarcacioncs pesqueras
modernas deben construirsc de materiales de chapa, pero tal
construccion exigc hcrramicntas y mano de obra costosas, a mcnos
que el casco sea desarrollable. Fn este trabajo, so exponcn las
propicdadcs fundamentalcs de las superficies desarrollables dem-
ostradas por teoremas matematicos originates, con el (in de propor-
cionar metodos grah'cos sencillos. tstos mclodos son aplicables en
general a todas las superficies dcsarrollablcs y no dependen de la
naturaleza especial dc las distintas clascs de superficies.
THE heavy capital investment in engines, rigging
and gear, characterizing the modern fishing craft, is
not compatible with the uncertain quality or un-
predictable life of a wooden hull. The engineer's (and
the banker's) demand for predictable performance dis-
courages the construction of wooden hulls even where
durable woods have not become expensive or unobtain-
able. The hull of continuous, homogeneous, testable
sheet material is inherently stronger and lighter than the
structure of small pieces of wood. If a skin of sheet
material can be designed for low labour cost in con-
struction, simple tools, and economy in repair, its
engineering superiority and eventual economic advantage
make it at once preferable to planks.
To enjoy the initial advantage of low labour cost in
construction and repair, the skin must be developable.
Construction must not demand expensive tools nor rare
skills. At the same time, the hydrodynamic performance
of the hull must be competitive with that of the best
shape possible in wood construction. While a large
number of model tests have shown that hard-chined
hulls can be designed to have not significantly higher
resistance than round-bottom hulls, the designer must
be able to control the shape within close limits. He must
be able to produce a hull of predetermined appearance
and characteristics, and must not be forced to accept
whatever happens when the material bends. Hence his
knowledge of the medium of his art must be intimate and
certain.
As ordinarily practised, the method of matching
developable surfaces to acceptable curves is a tedious
procedure. The method is based on the notion that any
developable surface must be either conical or cylindrical,
that any one of several cone-cylinder combinations will
fit if only they can be found, and that the task is the
simple one of trying a succession of surfaces until one is
found to fit approximately. The exact fit cannot be found
in this manner and so the designer's usual solution is to
alter the original curves to fit the surfaces haphazardly
accepted. He cuts the suit to fit the cloth. Preliminary
design becomes only a rough approximation. Rather
than exactly choosing volumes, centres, parameters and
desired forms for hydrodynamic and aesthetic reasons,
the designer determines the results after the drafting is
finished, then either accepts what chance has provided or
starts over again.
A method for direct generation of developable sur-
faces from given beginnings is therefore needed. In hull
design, these beginnings must consist of pairs of space
curves: chine and profile outline of intersection of hull
with centre-line, chine and deck edge, or two chines. The
location and shape of these curves, it is presumed, are
chosen carefully to suit displacement, appearance, and
hydrodynamic efficiency. The method should provide
surfaces to fit these curves, rather than to require altera-
tion of the curves to fit surfaces. This is to say that the
boundary curves adopted at the beginning of design
should appear as much as possible unaltered in the
finished drawing. Furthermore, the required method
should be based on universal properties of developable
surfaces, since the draughtsman cannot know in advance
whether or not the surface to fit his curves is conical,
cylindrical, convolute, or whatever.
FUNDAMENTAL PRINCIPLES
A draughtsman is not required to be a mathematician.
He must trust, nevertheless, the validity of the methods
he is using, and the command of his skill will be enhanced
if he understands why his methods are valid. The
graphical methods derived from the following theoretical
considerations could be executed without having read
this section; however, it might be profitable to consider
at least the definitions and theorems. Some of the
theorems on developable surfaces are impossible to
handle by Euclidian geometry, and so resort is made to
methods of differential geometry.
Ruled surface
Definition: A ruled surface is the locus of a line, called a
generator, whose direction is determined by successive
values of a parameter, moving continuously along a
[425]
curve (a directrix) and intersecting that directrix at an
angle other than zero.
Tangency
Definition: If a plane T and a surface S coinciding at a
point P, have a common normal through P, then T is
said to be tangential to 5* at P. By extension, if T and S
coincide at a succession of points determining a curve C
(or a line) and if the common normals to T and S at
each of these points on C are all parallel, then T is
said to be tangential to S along C. It is evident that the
normals to S and T will also be normal to C and to all
other curves or lines in either S or T that touch C.
Developable surface
Definition: A developable surface is a ruled surface
having the same tangential plane on one and the same
generator (Kreysig).
Remarks— deductions from definitions
From the definition of a ruled surface, it is evident that
the directrix must lie in the surface. From the definitions
of tangency and that of a developable surface, we
observe that each plane tangential to the surface must
also be tangential to the directrix, or for that matter to
any other curves in the surface that intersect the genera-
tors. A corollary observation is that if a plane be laid
tangential to a developable surface at any point, its
tangency will be along a line. This line is sometimes
called an element of the surface, but it is preferable to
call it a ruling of the surface, thus emphasizing the
membership of developable surfaces in the larger class
of ruled surfaces. The continuity of these rulings shows
that a developable surface may be brought into isometric
correspondence with a plane, meaning that every dimen-
sion of the surface may be mapped directly on a single
plane. Such a surface may be described algebraically by
writing the equation of a one-parameter family of planes,
excluding planes parallel to each other. Graphically, the
surface may be described by drawing a directrix and a
sufficient number of rulings (generators). Where more
than one space curve is known to lie in the surface, any
one or all can be used as a directrix. Planes tangential
to a surface will be tangential to these curves. It is known
axiomatically that any plane may be rendered graphically
by two intersecting lines or by two parallel lines.
Existence of a developable surface
Remarks: Given two space curves, C and A the possi-
bility of constructing a developable surface containing
both curves is the first step. Many ruled surfaces con-
taining both curves may exist, but no developable surface
may be possible. The only theorem providing a test for
the existence of a developable surface containing C and D
is very involved, and no simple statement is available to
provide an easy test. If in each projection of C and D on
the planes of a Cartesian system, their curvatures have
constantly the same sign, then the existence of the
desired developable surface is obvious by inspection, but
this is not a necessary condition. The draughtsman must
rely on experience and sometimes on trial.
Uniqueness
Theorem 1 : If two space curves lie in any developable
surface, they lie in one and only one such
surface
The proof of this theorem is as follows: Let C and A
having arc lengths s and a respectively, be two space
curves of allowable type, i.e. such as may lie in some (at
least one) developable surface. We eliminate the trivial
case of lines or points and agree that C and D are not
coplanar. Adopt the hypothesis that the theorem is not
true, i.e. more than one developable surface does exist
containing both C and D.
At a point Pj on C construct a plane TY , tangential to C
and let 7\ be tangential to D at Ql9 which is possible
by the hypothesis that C and D lie in at least one develop-
able surface. A line from Pl to d will now lie in Ti.
Denote the unit direction of this line by S(Pl , d)- Let the
unit tangent vectors to C and D be fc and fD. Now if the
unit normal to TI is Al%
,. d) - h = WCi) x f(Pl9 d)
Moving along D a distance A<r from Ql9 suppose another
plane T2 is tangential to D at Q29 and suppose T2
tangential to C at Pj. This is possible under the hypo-
thesis that C and D lie in more than one developable
surface. The normal to T2 is A2. Now
tc(Pi) x W,, d) - *a « WCi) x e(P^ d)
But, since both 7\ and T2 are tangential by hypothesis to
CatP,,
<i x A2 = fc(Px)
This, however, is equivalent to the statement that
i, d) x «d) x KP19 Q2) - fc(Pt) -
19 C2) x ^(d) x t(pl9 d),
which is absurd and this completes the proof.
Parallelism of tangents to parallel plane curves
Theorem 2: If two or more plane curves in S9 a develop-
able surface, are determined by the inter-
section of S with two or more parallel
planes, none of which contains any ruling of
S, the tangents to all such plane curves at
their respective intersections with any ruling
of S are parallel
The proof of this theorem is as follows: Let parallel
planes Rl and R2 . . . Rn intersect 5, a developable
surface, in the allowable manner, cutting plane curves
DI . . . Dn. If S is continuous, it may have a tangential
plane Tt along any ruling Lh and in S every curve Df
having a point on LI has a tangent lying in TV The plane
curves Dl...Dn cut in S by Rlt..Rn have such tangents,
'n • • • *•!» at ^eir intersections with L,. Now both tlt
and r2| lie in Ti9 but they also lie respectively in R^ and
R2 and thus are identical with the lines of intersection of
a plane T{ with two parallel planes. Consequently they
must appear parallel in every view.
Dimensions of co-ordinates
Remarks: It is well known from the theory of conformal
mapping that, after a function has been transformed to a
[426]
new co-ordinate system, the results of operations per-
formed in the new system may be mapped back into
the original system without loss of the same validity
that would have prevailed if the operations had all been
performed in the original system. In particular, if the
original system is simple Cartesian and if the transformed
system is no more than a linear transformation of one
dimension in the co-ordinate system, the effect is similar
to that of looking at the drawing through spectacles
which distort distances along one axis.
Approximations
Remarks: The essential procedure in graphically describ-
ing a developable surface is to describe the planes that
lie tangential to the surface. In many cases these tan-
gential planes can be located directly and exactly, but in
others the exact location becomes so laborious that
approximation becomes preferable. For this purpose we
take advantage of the similarity between a short segment
of a ship's curve and its osculating circle: a tangent to
the curve at the midpoint of a short segment will be
parallel to the chord between the ends of the segment.
Thus if a plane intersects a curve at two points not far
apart, the plane when rotated slightly will be tangential
midway between the two points.
GRAPHICAL APPLICATION OF
FUNDAMENTAL THEOREMS
In the foregoing section some of the fundamental
properties of all developable surfaces have been enumer-
ated. They will now be used for practical drawing
development. The important properties arc as follows:
• A developable surface may be depicted graphically
by drawing the family of planes that arc tangential
to it
• Any tangential plane to the surface is also tan-
gential to any curve lying in the surface and inter-
secting the line of tangency, or ruling
• Any plane found to be tangential to the surface
at any point is unique
These properties, as far as drawing is concerned, suggest
the following constructional approaches:
• Planes tangential to the surface should be found
• These planes are best found by using given curves
already known to line in the desired surface, such
as chine, sheer and profile centre-line outline
• If any plane can be found to be tangential at a
particular point, it is the unique plane tangential
at that point and may be used with confidence.
The best means of illustration is a practical example, so
the following gives the general procedure for the develop-
ment of planes applicable to a line drawing of a vessel
with the following particulars.
Lwl . 39.5 ft (12m)
A .... 15.57 tons
C^ . 0.59
F. B . . . . 0.53 Lwl
A preliminary hull design is drawn meeting these
requirements, and with straight line sections (fig 1).
Fig 1. The preliminary body plan
Sheet materials can hardly ever be applied to a hull of
straight line sections and so these sections must become
suitably curved. The designer, with practice, will learn
how to make allowances for this curvature in the pre-
liminary design stage, so as finally to give the required
hull parameters.
The sides of the boat above the chine are not as easy
to develop as the bottom below it. In fig 2 the hull
drawing has been laid out foreshortened longitudinally
in half breadth and profile. This is done as the main
method of constructional drawing and consists of
locating various points by drawing tangents to curves at
these points.
The side surface of the boat above the chine is
obviously contained by two required curves, the sheer
and chine lines, but some doubt exists at present whether
a developable surface can be fitted to the straight stem
line. As the sheer and chine lines are not simple curves,
we cannot develop the surface by the more simple
method that will be utilized on the bottom. The approach
used is that a tangent is drawn to one curve and the
plane generated is then swung until it comes into tan-
gency with the other known curve. This is not difficult,
as is shown below :
• Take a point P at the bow on the chine and in
both the half breadth and profile draw the tan-
gents to the chine line passing through P
• From this tangent draw any line AB intersecting
the sheer line in B at a reasonable intersection
angle in profile and half breadth view
• At suitable short intervals from this line, i.e. at
C and E, draw the same lines parallel to AB in
the profile and the half beam
• At the intersection of the lines through C and £
and the sheer line in the half breadth view are
the points D and F
• Transfer these points to the profile giving curve
BDF
• Define the point Q where the curve BDF cuts the
sheer line
• Take the point P at the midpoint of BQ
• Join P and P' giving the line of tangency (ruling)
of the plane PAB with the side surface of the
vessel
[427]
An explanation of the above is as follows: The line
ACE is the tangent to the chine line at P in both views.
Therefore PAB gives a plane that is tangential to the
chine and cuts the sheer line. If in profile this plane cuts
the sheer line again at a second point adjacent to B, the
plane must be almost tangential to the sheer line. To
find this second point, we suppose the sheer line in the
half breadth to be the edge view of a cylinder. This
cylinder cuts the plane PAB and because AB, CD and
£Flie in the plane PAB, the cylinder must cut them in the
points B9 D and F and these lie, as already stated, on the
sheer line in half breadth. Therefore the curve BDF in
profile shows the intersection of the cylinder with plane
PAB and coincides with the sheer line at B and the
second point Q.
Now, if PAB is rotated about PA it would become
completely tangential to the sheer line approximately at
the midpoint of BC at Pf (osculating circle). The line
PP' is therefore a line of tangency of a plane with the
surface of the boat.
Another similar operation is illustrated farther aft.
This time the initial tangent line is taken on the edge of
deck rather than on the chine. The sequence is the same
as before: beginning at P, a tangent line to A; from A,
on the tangent line, to B on the chine; parallel lines CD
and EF to the chine in half breadth plane. In profile, the
lines are drawn initially from C and E parallel to AB
without knowing where D and F occur on them. The
locations of D and F in the profile view must be located
by projecting them upwards from the lines in the half
breadth view. The curve BDF is the intersection of a
cylindrical surface (of which the chine in this case is the
edge view in half breadth) with plane PAB. This curve
intersects the chine at B and F, and therefore a slight
rotation of PAB will bring it into tangency about mid-
way between B and F, at P'. The line PP' is a line of
tangency of a plane with the surface of the boat, shown
as ruling number 9.
The rest of the rulings on the side surface, shown in
heavy lines and numbered 1 through 13, were obtained
by the same manner. Finding all of them took the author
two hours. The draughtsman must acquire a feeling for
the surface he is working on. Once he visualizes it, the
work is rapid and economical. It should be noted that
development of the planes was commenced in the half
breadth view. It could have been started in the profile
view, letting the sheer or chine in that view represent the
edge view of the cylinder, but then the cylinder would
have intersected the plane almost perpendicularly, and
the curve of intersection when projected on half breadth
would not be so well defined. With experience, the
draughtsman will select the view where the plane will be
Fig 2. Development of sides
[428]
3. Development of bottom by inter sect ing tangents
intersected at the most acute angle for commencement.
Sometimes the two points of intersection of the plane
with the given line will be too far apart, in which case
it will be necessary to refine the accuracy by drawing a
new plane closer to the point of tangency. Jt is always
advisable to keep superfluous lines off the main drawing;
lay a piece of tracing paper over the drawing and do all
the construction on that. Do not waste time or add to the
work by erasing and working on a blurred drawing.
Development of the bottom is much simpler because
the centre-line curve lies entirely within a plane. Because
of the foreshortening of the drawing, the resultant
curvature of the lines makes points of tangency easier
to find. The development of the surface near the bow is
shown in fig 3. Ruling 2 is used as the example. The
graphical construction is as follows:
• In half breadth draw tangent to chine line at P
and project it forward to intersect with the centre-
line plane at A
% Transfer the point P to the profile and draw the
tangent to the profile chine line through P
• Transfer point A from half breadth to extended
tangent line through P in profile giving the
point B
• Through B draw tangent line to bow profile
obtaining point C, giving the plane PBC
The explanation is as follows: The intersection of the
tangent with the centre-line at A in the half breadth
must be in the same plane as the point B in profile. The
line from B locates C and is tangential to stem profile.
So the tangential plane is complete in PBC, because it is
the plane tangential to two curves lying in a developable
surface. Line PC is the unique line of tangency of PBC
with the surface. Hence PC is ruling number 2. Rulings
number 1, 3 and 4 are determined by the same method,
[429]
Beyond Station 4, a tangent to the chine will run off
the drawing-board before it intersects the centre-line, so
that from this point a third method of development
must be employed. The method used is as follows
(fig 4):
• Draw a line parallel with the centre-line tangential
to the chine line giving the point P in the half
breadth
• Transfer this point to the profile and draw the
tangent to the chine line through P
• Still in profile, draw a line parallel to this
tangent line to the chine, but tangential to the
centre-line outline giving the point A
• Join PA which is the ruling of the surface number 5
This is based on the theorem of parallel tangents
already stated. Therefore, by the theorem, the tangent to
the chine at a ruling of the surface through P, in the
profile view, will be parallel to the centre-line outline
curve at the intersection of that ruling with the centre-line
outline.
Now referring to fig 1, note that bottom sections 8, 9
and 10 are parallel in the body plan. They are also
parallel in all other views, and therefore they define a
cylindrical surface. Hence we do not have to develop the
bottom abaft Station 8 : this is already done.
To obtain the rulings 6 to 9, the following procedure
is adopted:
• Transfer the buttock lines 1, 2 and 3 to the profile
by using the height intersection from the body
sections, for sections 8, 9 and 10. Transfer the
intersections of the buttocks and rulings 1 , 2, 3,
4 and 5 in the half breadth to the profile. Fit a
spline to these points precisely, and draw the
buttock lines in profile
Fig 4. Use of parallel tangents
• Draw parallel tangents to the buttocks and centre-
line profile line in profile, the points of tangency
give the rulings
• Check all points lie on straight lines in both
views. This gives the points BB'9 etc., and the
rulings 6, 7 and 8
This again is dependent on the parallel tangent
theorem as buttocks and centre-line profile represent
parallel planes. The gap between Station 8 and ruling
number 5 is considerable, but the spline is held on at
least three points at each side of the gap. It will pretty
accurately describe the only fair line that can be drawn
between these points. The balance of the bottom, abaft
Station 8, of course, has already been found to consist of
straight, parallel frames.
Developing the bottom requires half an hour. If it
had been necessary, the same method could have been
used on the bottom as on the sides, but faster and more
accurate methods were available. The final lines are
shown in the body plan, fig 5. This was obtained by
transferring the new buttock lines on the stations from
the profile and halfbeam shown in fig 4. The sections in
the sides of the forward part of the boat are so nearly
straight that the very slight curvature in them cannot be
shown with the small scale on which these drawings were
done. Almost any material, metal or otherwise, will have
sufficient plasticity to accommodate slight deformation.
The development of the bulwarks is not shown. In this
case the top of rail is drawn at a constant distance from
the deck, and the bulwarks could be rapidly and accur-
ately developed by the method of parallel tangents,
since over short distances the sheer and bulwark lines in
profile can be considered straight lines.
Fig 5. Final body plan
The displacement, prismatic coefficient and the position
of the longitudinal centre of buoyancy have been altered,
though not a great deal. If the exact specified particulars
are desired, the designer should make provision in the
preliminary plan for these predictable changes. The lines
of chine, sheer and outline are exactly the same as
originally proposed.
APPLICATION OF FUNDAMENTALS IN
CONSTRUCTION
The early automobiles were equipped with whip sockets.
Structures are still designed for reinforced concrete as
if they were to be built of masonry and the frames of
boats as if they were to be planked with wood. In the
[430]
case of steel or aluminium hulls with developable sur-
faces, at least the ancient notion that a boat is supposed
to have a backbone and ribs like any other real animal
would be best forgotten.
A metal hull with developable surfaces can be built
almost entirely with straight frame members. It is true
that hardly any of these members will be perpendicular
to the keel, but there is no engineering reason why a
stiffener on a plate should be perpendicular to its land-
ings if it is firmly fixed. Welding has ended any practical
reason for right angles. A hard-chined boat can be built
with no forming or bending required on any part except
chine bars, stem bars and perhaps deck beams (even
these can be longitudinal). Although chine bars are often
omitted when perpendicular or longitudinal framing is
used, they would be necessary for landing of canted
frames.
Such hulls require the minimum of lofting and tem-
plate making. They require no expensive furnaces nor
heavy tools. High skill in metal working is not needed.
A shipwright and a welder will do a perfect job. The
appearance and the efficiency of their product will
depend solely on the art and skill of the designer in
working with a special medium, for the design of develop-
able surfaces is not merely a matter of knowing how to
fit surfaces to curves. Just as the sculptor trained for
stone is not sure of success in wood, so the naval archi-
tect accustomed to traditional methods is not necessarily
sure of success with developable surfaces before he has
mastered his medium.
CONCLUSION
In the development of the hull here used as an example,
no presuppositions were made as to the nature of the
surfaces. It was not supposed that the surfaces were
conical, nor of any particular class. True, a part of the
bottom at the stern was seen to be cylindrical, but this
was not a presupposition. We have spent no time
hunting for some apex of some unknown and undefinable
cone which probably was non-cxistant. Most boat sur-
faces are convolute and hence have no apex.
The properties exploited are those applicable to all
developable surfaces. If the proofs of these properties
are anywhere deficient in mathematical rigour, they can
be defended by the assertion that their inadequacy in
practical work is an extremely remote possibility and are
certain enough for the naval architect to use them with
confidence.
Acknowledgment
Dr. Finn C. Miehelson, Professor of Naval Architecture at the
University of Michigan, has participated in the evolution of the ideas
contained in this paper by many stimulating discussions and has
consistently encouraged the pursuit. Some of the solutions were
originally proposed by him. Mr. David Eraser, Naval Architect on
the FAO staff, on loan from NPL, has supplied valuable assistance
in the clear presentation of a somewhat recondite subject.
[431]
Dug-out Canoes and other
Indigenous Small Craft
by A. J. Thomas
Pirogues monoxyles ct autres embarcations autochtones
L'auteur apportedcsdonn6es historiques et sociologiqucs pcrmettant
au lecteur de bien comprendre les divers factcurs d'ordre technique,
social et economique qui intcrviennent dans tout effort demecanisa-
tion des pirogues monoxyles et autres embarcations autochtones.
II est procedc a unc comparaison d'ordre general cntrc la mecanisa-
tion dcs bateaux indigenes actuels et Introduction dc bailments
modernes perfectionnes dans des societcs primitives. Apres avoir
passe en revue les inconvcnienls et les avantages dcs bateaux
autochtones, 1'autcur present e des directives generates pour leur
mdcanisation, illustrees par plusieurs excmplcs concrets.
Las piraguas mon6xilas y otras pequenas embarcacioncs indigenas
Una exposici6n dc los antecedentes historicos y sociales de estas
embarcaciones sirve de introducci6n al trabajo y conduce al lector a
traves de una completa aprcciacion de los diversos factores tccnicos,
sociales y economicos inherenles a todo intento de mecanizacion, Se
establece una comparaci6n general entre la mccani/acion de las
actuales embarcaciones indigenas y la introduccion de otras
modcrnas y mejor acabadas, en las comunidades mas primitivas.
Se enumeran y analizan las vcntajas e inconvenientcs de las embarca-
ciones indigenas y so ofrecen, por ultimo, oricntaciones generales
para su mccanizacion, ilustradas con varios ejemplos pricticos ya
realizados.
A great deal of study has been undertaken by naval
architects, marine engineers and other technicians,
of fishing craft of the types and si/es used in
developed countries. During the past decade FAO has
also undertaken a number of missions to developing
countries in order to improve the designs of fishing ves-
sels, with the result that a large number of improved
boats has been built and much valuable experience has
been gained. In contrast to this, very little attention has
been given to the considerable numbers of varying types
of small fishing craft which are mostly used by fishermen
in developing countries, although it is believed that these
craft greatly out-numbered the larger craft in the fish-
eries of developed countries. Tn the past, there was a ten-
dency among technicians accustomed to larger craft, to
regard these small craft as "relics of the past" without a
full appreciation of the social, economic, technological
and other factors involved.
Whilst one of the long-term solutions to the problem
of increasing production of fish in many developing
countries may be found in a fleet of well-designed dicsel-
powered fishing boats, such a programme is often beyond
the resources of many developing nations. Moreover,
since there is mounting evidence that the outboard engine
is playing a significant part in increasing the mobility of
small craft and thus expanding the productivity of the
small-boat fishermen, it is believed that a re-examination
of the problem is justified, bearing in mind that, among
other things, the outboard engine possesses the lowest
weight-for-horse-power ratio of any kind of marine
power and that the outboard-engine horsepower costs
less than diesel horsepower.
HISTORICAL BACKGROUND OF INDIGENOUS
SMALL CRAFT
Whilst it is not intended, except where appropriate, to
examine the early historical background surrounding the
development of the various types of small craft operated
in many developing countries, it is nevertheless true to say
that large numbers of these craft were developed out of
the historical and sometimes geographical circumstances
surrounding the countries in which they arc found. Very
often, therefore, they are intimately associated with the
traditional art of the country and thus involve the implica-
tions of long tradition. Moreover, their existence is also
often related to the socio-economic condition of the
fishermen. It is against this background that a critical
analysis of these craft should be undertaken. This implies
that in trying initially to improve the productivity of the
vast numbers of small-boat fishermen to be found in
developing countries, it is necessary that attention should
be given to two main considerations. These are: (a)
whether the traditional craft whose behaviour, economics
and functional adaptability are so well understood by the
fishermen should be replaced by a more modern design
whose behaviour and economics under certain given
conditions are understood by the designer or other tech-
nician (but not by the fishermen) or(b) whether improve-
ments which would not seriously alter the behaviour or
functional adaptability of the traditional craft, but would
increase its efficiency, should be undertaken. Tn order to
answer either question it is necessary that close examina-
tion should be made of the social, economic, tech-
nological and other factors involved in the operations of
these small craft.
DISADVANTAGES OF INDIGENOUS
SMALL CRAFT
Generally speaking, these small, open craft possess
serious and often unalterable limitations but they also
possess many advantages and it is believed that their limi-
tations can often be out-weighed by the advantages. The
following are some of the limitations which characterize
these small craft:
[432]
• They are open and therefore not adaptable to
sleeping or cooking arrangements
• The crew are exposed to sun and rain
• Not adaptable to the use of large and heavy fishing
gear
• Not usually adaptable to most kinds of mechani-
cally operated fishing equipment
• Many, especially dug-out canoes, are much less
durable than plank-built wooden craft since, in the
case of the latter, planks can be replaced when
necessary. The life of the former depends on the
wood from which it is constructed
• Operations are sometimes limited by weather con-
ditions that would not affect larger, decked craft
• Not normally adaptable to automatic bailing
equipment
• Being open, they must usually return to base daily
• Fish-holding capacity is very limited
ADVANTAGES OF INDIGENOUS SMALL
CRAFT
On the other hand the following are some of the advan-
tages of these craft:
• The total capitalization for equipping them for
fishing is low and the capitalization per worker is
correspondingly low. This is important in develop-
ing countries with limited capital resources. In
Jamaica, a dug-out canoe of 28 ft L < 5 ft B (8.6 x
1.5 m) fitted with an 18 hp outboard engine and
using mobile fish traps and hook and line, might
represent a total capital outlay of £450 (US$1, 260).
If a crew of four is required, the capitalization per
worker would be approximately £113 (US$316).
The gross turnover can be calculated at £1,000
(US$2,800) per annum or an average of £250
(US$700) per worker per annum. With a slightly
larger craft and a correspondingly higher total
and per-worker capitalization, the gross turnover
may be twice as good. The gross income will vary
according to the skill of the fishermen, the bio-
logical condition of the fisheries and other factors.
This income should be compared with the average
income per capita of the population in comparable
employment in the country. In Gambia, a part
dug-out, part planked canoe of 28 ft Lx5.5 ft B
(8.6x1. 7m) fitted with a 5J hp outboard engine
and using beach seine, represents a total capitaliza-
tion of £230 (US$644). With a crew of six the
capitalization per worker is £38 (US$106). The
gross turnover is calculated at £800 (US$2,240)
per annum or an average earning of £1 33 (US$372)
per worker per annum. This is considerably higher
than the annual earning of the average farmer in
Gambia. The estimated income per capita of the
population is estimated as under £30 (US$84). It
should be emphasized, however, that in both exam-
ples given, division of earnings is not allocated
evenly as between the boat/engine/net owner
and the crew. The former retains a much higher
proportion than that paid to individual members
of the crew as payment of fuel and as compensation
for having provided the boat, the engine and some-
times the gear
These craft require no harbour or special installa-
tions, often a financial strain upon the resources
of developing countries, but are hauled up the
beaches along the coast
Fishermen often live in the proximity of the coast
adjacent to berthing areas and therefore remain
in rural surroundings instead of invading towns
and causing housing and other social problems
Dispersal of small boats along the coast enables
widespread fish supplies, often without the ad-
ditional cost of road transport increasing the cost
of distribution
Require no slipways for servicing and arc there-
fore inexpensive to maintain. Dug-out canoes
require no caulking
Local skills and often local materials are used in
their construction, thus providing local employment
The cost of small boats is very often within the
means of individual fishermen, satisfy their pride
of ownership and desire for self-employment. The
limited capital involved permits large numbers of
fishermen to eventually become boat/engine owners
Large numbers of small boats enable fishing plat-
forms to be dispersed over wide areas. This is of
special advantage where fish are widely dispersed
in small shoals
In many countries the construction of small boats
is such that they remain afloat when capsized.
Thus, in the mind of the fisherman, his small boat
is his "life raft"
As planing craft, small boats arc able to operate
in very shallow water areas
Constitute a cheap form of water-transport
through shallow creeks and rivers in the absence
of roads, the construction of which often places a
strain upon the resources of many developing
countries, or where the economic justification for
construction of roads is in doubt
Arc often indispensable in places inundated by
floods
Can be propelled by oars in cases of engine failure
Construction of these small wooden craft requires
no centralized boat-yard or expensive equipment.
They are often constructed on the sea-beach
Are adaptable to various types of fishing gear, e.g.
hook and line, longline, multiple-trolling rig, gill-
net, cast net, beach seine, fish traps and small
shrimp trawl
When not in operation, they require no hurricane
shelter in areas which are subject to such pheno-
mena. In such an emergency they can be weighted
with sand or hauled into a safe area
Very often large numbers in a given country can
be adapted to an outboard engine, that is an inex-
pensive "mobile" engine and does not require
installation of engine-bed, stern tube, etc
Since generally they are taken out of the water
daily, much of the damage to which they would
otherwise be subjected through marine borers is
avoided
[433]
• The hull can be constructed by hollowing it out of
a tree trunk as is the case in Jamaica, Ghana and
certain other parts of Africa, wholly out of planks
or part out of a tree trunk and part of planks as in
Senegal and Gambia in West Africa and elsewhere
• Well-constructed small boats when motorized can
attain good operational range. In Jamaica, dug-out
canoes, which have been adapted to motorization
and improved in size as a result of mechanical pro-
pulsion, often undertake round trips of 120 miles
at right angles to the coast
• Enable fishermen, long accustomed to daily con-
tact with family and friends, to maintain this
tradition
EXAMPLES OF IMPROVEMENTS IN
INDIGENOUS SMALL CRAFT
An example of the improvement in the mobility of small
craft and the consequent improvement in the economic
and social status of the fishermen, without seriously
altering the structure of the traditional craft, its be-
haviour or functional adaptability, is provided by the case
covers an area much larger than the hole. It is strength-
ened by a false thwart resting (unlike the other main
thwarts) on top of the built-up keel. The forward section
of the box extends through the hole in the keel to its full
depth whilst the sides and after sections of the box rest
on the top of the built-up keel. The engine is clamped on
to the forward sections of the box with the steering/
throttle handle pointing toward the bow. The propeller
is thus under the boat. One disadvantage, where the hole
is too small to permit the tilting of the engine shaft out
of the water, is that the engine must be removed before
launching and landing in order to avoid damage to the
propeller.
Another example of the adaptation is provided in the
case of the dug-out canoe in Jamaica. The Jamaican canoe
is hollowed out of the trunk of the "silk cotton" and less
frequently out of the trunk of the "guango", both of
which grow there. It has been constructed in Jamaica for
many centuries originally by the indigenous people, the
Arawak Indians. It was also used by the warlike Carib
Indians as a means of transport as they moved from
island to island in the capture of the Lesser Antilles and
from there to make raids upon the Arawak Indians in
Fig 1. Senegalese/ Gambian canoe showing well constructed inside the craft to hold the outboard engine
Fig 2. Traditional Jamaican dug-out canoe showing shape of bow and stern before introduction of
mechanical power
of the Senegalese, and to much more limited extent in the
case of the Gambian canoe operating on the Atlantic
coast, both of which are structurally similar. In both cases
the outboard engine has been adapted to the craft.
This craft can be briefly described as partly dug-out and
partly planked. The dug-out portion represents the keel
which is of heavy hardwood, the height of which is raised
by the addition of one and sometimes two planks of
lighter wood slanting outwards. The height and width are
further increased by planks of light wood, still slanting
further outwards and overlapping the top of the built-up
keel. This results in a flange along the full length of the
outer sides of the craft. The structure is supported by
thwarts extending from one gunwale to the other and
covered by a capping. In order to adapt the outboard
engine to the craft, a well has been constructed inside.
This has been accomplished by cutting, near the stern, a
rectangular hole through the keel and constructing a
rectangular box directly above the hole, (fig 1). This box
Jamaica before Christopher Columbus had discovered
and taken possession of it. In early times this craft varied
greatly in size. Some were constructed for one person only,
whilst others were made to carry forty, fifty or more.
Columbus saw one in Jamaica, 92 ft L x 8 ft B (29 x 2.5 m)
(Black, 1958).
Traditionally, the Jamaican canoe was constructed
with bow and stern fine somewhat similar in shape to the
Montague whaler used by the British Navy (fig 2) and
was propelled by sails and oars. Generally, in more mod-
ern times the length of the canoes ranged to about 28 ft
(8.6 m), most being below that length. The extreme
width rarely, if ever, exceeded 4 ft (1.2 m).
In the initial stages in attempting to improve the status
of the fishermen, it was considered inadvisable to remove
them from their small traditional craft but rather to
improve its mobility and operational range and reduce
the fatigue to which the oar-pulling fishermen were sub-
jected. The reasons for adapting the outboards as a
[434]
"mobile" unit to the craft are discussed elsewhere
(Thomas, 1960). It was determined that the outboard
could be attached most appropriately to the stern of the
canoe and some crude adaptations were made to accommo-
date the engine. This led to the consideration of a transom
stern. But due to the texture of the silk cotton wood, it
was decided that hardwood would be more resistant to
the weight and the vibration of the engine. A transom
stern of hardwood was therefore adapted (fig 3). This
was constructed of a thick plank and moulded to fit
fishermen and builders of change and progress. As a direct
result of the influence of mechanical propulsion, the
structure of the Jamaican canoe was modified to embrace
the conventional lines of a more modern fishing boat
(fig 3). It thus became more suitable for planing speeds.
The freedom from dependence upon man and wind power
resulted in the construction of canoes of greater dimen-
sions, use of improved fishing gear and techniques which
were not possible before the introduction of mechanical
power. The cumulative results of the improvements, the
Fig 3. Showing transom atcrn being a modification in shape of hull as a result of introduction
of outboard power
between the sides of the canoe in such a manner as to be
flush with the stern end. The adapted transom board was
fastened and further strengthened by means of a strong
metal bar fitted just below the gunwale and passing from
one side of the canoe to the other near the transom.
Sometimes "knees" of metal, bolted to the transom and
the outer sides of the canoe near to the gunwales, added
further strength to the adapted transom.
The adaptation described was successful and resulted in
the transom stern, to accommodate the outboard engine,
becoming a permanent feature in the construction of
canoes. This was regarded as a mental acceptance by the
programmes of training of fishermen and making credit
facilities available to them from public funds are
described elsewhere (Thomas, 1960).
It may be of interest to state a further development
from the improvements described. Private Jamaican
financial and engineering interests have established in
Jamaica a factory which constructs the improved type of
canoe from fibreglass. The bilge of this craft is fitted with
styrofoam to ensure floatation when capsized. Thus, a
new industry has been created to the benefit of the
economy of Jamaica.
1435]
Fishing Boats for Developing Fisheries
by P. Gurtner
Types de bateaux destines aux pays dont les peches sont en voie de
dtveloppement
La communication passe en revue l'activit£ de la FAO durant les
15 dernieres annees en matiere de conception des bateaux de
peche; elle est illustree par 32 dessins representant divers types de
pctits bailments en bois, utilises principalement en Extreme Orient
et en Afrique.
L'auteur fournit des donnees sur les plans et les performances,
ainsi que des renseignements connexes: resultats d'cssais au bassin,
essais de modeles en vraie grandeur, predictions de la puissance
effective, etablics au moycn d'un ordinateur, poids, et couts. II
signale que Ton dispose de tres peu de renseignements sur les
bateaux de petite taille, et exprime 1'espoir que les donndes fournies
ici encouragent le rassemblement ct 1'intcrprdtation d'une docu-
mentation compldmcntaire. Dans un bref resume de Texp^rience
de la FAO sont examinees les mesures recommand6es en vue d'une
expansion coherente des flottilles de peche cotierc dans les pays
ou rindustrie halieutique est en voic de develop pement.
Embarcaciones de pesca para las pesquerias en vias de desarrollo
Se examinan las actividades de la FAO en el desarrollo de diseno de
embarcaciones de pesca durante Jos quince aftos ullimos; 32
dibujos ilustran numerosos tipos de pequefias embarcaciones
pesqueras de madera, principalmente en el Lejano Orientc y
Africa.
Se dan los datos de disefto y comportamiento asf como informa-
ci6n afin sobre los resultados de las pruebas en el canal hidrodi-
ndmico, ensayos a escala normal y prediccioncs de las calculadoras
sobre la potencia cfectiva, pesos y costos. Se pone de relieve la
limitadisima information de que se dispone acerca de las pequefias
embarcaciones; los datos prescntados deben actuar como estimulo
para un nuevo acopio e interpretacidn de tales datos. Las medidas
recomendadas para el desarrollo integrado de las flotas de
bajura en las pesquerias en desarrollo figuran en un corto resumen
dc las experiencias obtenidas por la FAO en esta csfera.
MANY countries in Africa, Asia and Latin
America have made considerable development
efforts during the last 15 years to create larger,
more efficient inshore fishing fleets. This necessitated
technical assistance from outside to overcome the lack of
qualified and experienced technical personnel required
for an effective development of fishing boats, gear,
fishing methods and disposal of catches.
FAO has been actively assisting countries requesting
specialized assistance in the field of fishing boat design.
Table 1 lists the main boat development projects under-
taken by FAO. These projects generally have followed a
similar pattern, initially in obtaining detailed knowledge
of local boats engaged in fishing, then simultaneously
trying to improve on these boats by introducing small
changes in hull form and construction, and more
efficient fishing gear and methods, and finally by develop-
ing new boat designs, specifically suited to local fishing
requirements and the capabilities of local boatbuilding
industries. Parallel with the improvement of local boat
types and the introduction of new types, it was often
necessary to conduct training courses for local fisheries
officers and boatbuilders. The obvious aim of such
schemes was to ensure that the work of a technical
assistance mission would be continued under the guidance
of local personnel, once the mission itself had concluded
its operation.
Similar development work was undertaken in many
cases by governments without direct foreign assistance,
and in other cases bilateral aid missions have contributed
by providing material aid and/or expert assistance in the
field of fishing boat construction.
Fig 1 to 23 and 25 to 32 show a number of boat
designs developed by FAO naval architects serving on
technical assistance projects during the 15-year period,
while fig 24 and 33 represent two noteworthy examples
of unassisted government work. It is not the purpose of
this paper to report in detail how each of the projects
was planned and executed; the reports issued by FAO
and based on the work of the project staff contain the
relevant details on policy and administrative matters.
It is intended to show some examples of what has been
achieved. It should be noted that technical assistance
work is often conducted under very trying conditions,
and that the naval architect charged with the task of
developing modern boat designs for a fishery that often
has evolved directly from the dug-out to the fully
mechanized modern fishing vessel, faces very different
obstacles from those encountered by his colleagues in
highly developed countries.
Very little factual information exists— apart from
design particulars— regarding the boats presented. This
is very unfortunate, but is explained by the fact that the
designers of these boats rarely had the possibility of
closely following the construction of the boats and later
their performance under operational conditions. It is
hoped that in the future it will be possible to collect and
disseminate more information on weights, stability and
performance of boats introduced in developing fisheries
nations. This information would greatly facilitate the
work of boat designers who suffer from an immense
lack of applicable reference material in such countries.
Apart from the account of FAO's work this paper
should be considered as a stimulus to greater future
efforts in collecting reliable data on boat construction
and performance as an aid to designers.
PRESENTATION OF BOAT DESIGNS
The following boats are shown with representative
drawings, and table 2 gives their main particulars:
[436]
TABLE 1
Main boat development projects undertaken by FAO experts
Country
Expert
Subject
*••*(•)
FAO
Report No
Turkey
H.I. Chapelle
Survey of existing fleet and design
of new types
1956/57
706
We«t Pakistan
H. MagnusBon
Survey of local fleet
1953
403
C.S. Ohlason
Design of modern vessel s based on looal
types
1953
403
India
P.B. Ziener
Survey of existing boats, mechanisation
introduction of modern designs
1953/58
945
K.K. Rasmus sen
as Ziener
1956/57
945
P. Gartner
Introduction of modern designs, training
organisation of fishing boat service
•
1958/61
1096, 153J
A. Sutherland
Organization of marine engineering
service, training
1961/62
1710
Ceylon
E. Kyaran
Mechanisation, organization of marine
engineering service, training
1953/65
IblB
E. Est lander
P. Ki'Oops
Outboard mechanization, boatbuilding
Introduction of modern designs
(emphasis on steel vessels)
1959/62
1965
1963/65
2004
mi
Thailand
P.S. Hatfield
Study of local fleet, introduction of
modern trawler design
1963
1846
Stfnlgal
P. Ourtner
Introduction of modern boat types,
boatbuilding traing
1962/64
in prep.
J.P. tycon
Boatbuilding training
1962/65
in prep.
(/. Oulbrandaen
Boat design and construction
1964/65
Nigeria
R. Anderson
C.S. Ohlsson
Study of boatbuilding possibilities
Lake Chad
1963
1711
J.F. Tyson
Short term investigation of boat
building possibilities
1965
in prep.
Peru/Ecuador
P. Knoops
Research vessel construction
1961/63
West Indies
K.K. Rasmus sen
Introduction of modern boat design
1960/61
1409
24 ft (7.3 m) beach landing boat BB-59 (fig 1)
Developed specifically for limited surf landing operations
in India. Extensive tests were conducted with different
designs and BB-59 embodies the conclusions (FAO
Reports Nos 945, 1096, 1535). The boat proved success-
ful on subsequent trials, but no further attempts were
made in India to introduce this type in large numbers.
Considerable interest was shown in the design in USA
and Latin America as a consequence of its publication
in fishing Boats of the World; 2.
25 ft (7.6 m) open fishing boat (fig 2 and 3)
The third version in the development of a small, open
boat for inshore fishing in India, this design followed
[437
earlier types of 24 ft (7.3 m) and 25 ft (7.6 m). About
150 boats were built and operate mainly for gillnet
fishing and shrimp trawling (FAO Reports Nos 945,
1096, 1535).
27 ft (8 m) fishing boat £26 (fig 4 and 5)
This boat was developed in Ceylon for inshore fishing
with gillnets. Many boats were built during the last few
years and they continue to be an important part of the
fleet (FAO Report No. 2217).
30 ft (9.15 m) open fishing boat (fig 6 and 7)
The lines and construction drawing in fig 6 show the
boat as originally conceived. It served as an inshore
boat for gillnet fishing, with considerably larger capacity
than the 24ft (7.3m) and 25ft (7.6m) boats; its con-
struction was simple and complied with local practice.
The same basic boat was later produced in a half-decked
version, fig 7, for trawling and gillnetting. Subsequently,
the lines were redrawn with increased sheer forward,
rake to the keel, and beam, and boats of this type are
now being built as fully decked, small trawlers through-
out South India. It is estimated that about 450 boats of
this type are in operation (FAO Reports Nos 945, 1096).
32 ft (9.75 m) fishing boat £32 (fig 8)
Designed recently for longlining operations in Ceylon,
this is a further example in the development chain from
very small, open to fully decked, mechanized boats
(FAO Report No. 2217). One boat to this design has
been built in Uganda.
32 ft (9.75 m) shrimp trawler (fig 9 to 11)
The small shrimp trawler shown marked the end of a
development started in 1956 on the Indian east coast.
Only one boat was built to the original drawings. Sub-
sequent 32 ft (9.75 m) models were constructed mainly
in Kerala on the west coast where about 45 of these
boats are fishing now (FAO Reports Nos 945, 1096,
1535). The original idea of developing a 32ft (9.75m)
multi-purpose boat was dropped, but the boat presented
here was the result.
32 ft (9.75 m) fishing boat (fig 12 and 13)
The success of the 32ft (9.75m) shrimp trawlers in
Kerala created considerable interest in a boat of similar
dimensions, but specifically suited for fishing methods
other than trawling. New lines were drawn, giving the
boat a more marked forefoot, essential for drifting. An
aft engine installation was chosen to suit line and gillnet
fishing. The boom in shrimping on the Indian west coast
caused the original interest in this design to fade; on the
east coast it was considered to be too costly for the line
and gillnet fisheries.
36 ft (11 m) shrimp trawler (fig 14 to 16)
The development of the shrimp processing industry in
Kerala in 1959 to 1960 created a demand for a larger
shrimp trawler to supply the freezing and canning
plants. Originally it was felt that a boat of about 40 ft
(12.2m) would be required (FAO Report No 1096).
Later it was found that the 36ft (11 m) design would
meet the requirements of the industry and would allow
a better utilization of the vessel on the nearby Cochin
shrimping grounds. Some 15 to 20 boats of this type
now operate along the Kerala and Mysore coast. The
boat is as yet too expensive for the fisherman-owner.
Processing firms, operating with a large profit margin
because of the high world market price, find it possible
to invest in these boats.
38 ft (11.6 m) trawler (fig 17)
In Ceylon an FAO naval architect proposed this design
of a chine hull to investigate the possibility of reducing
the excessively high building costs. It now appears that
no wooden vessel of this type will be constructed. The
design is being reissued for steel construction in view of
the increasing building capacity for steel vessels in
Ceylon. The layout of the boat is similar to that of fig 15
with the exception of the fish hold, which will be arranged
for carrying live bait for tuna fishing. The hold space
will be sub-divided into tanks with pumping facilities
for circulating sea water, and for storing of fish in
chilled sea water.
42 ft (12.8 m) fishing boat (fig 18 and 19)
This originated as a vessel to be used for resources assess-
ment off the coast of Orissa State in eastern India. The
design should be well suited as a small trawler for
commercial operations, for both stern or side trawling.
Several boats of this type were built in Orissa during
1964 and 1965 but no records of their performance are
yet available.
42.6 ft (13 m) handline fishing boat (fig 20 and 21)
This is an example of the introduction of a new boat
into a fishery previously entirely conducted from canoes.
No intermediate development steps were taken. To
facilitate this large change a training course for boat-
builders was organized before the boat could be intro-
duced. The drawings show the second, improved version
of a handline fishing boat introduced in Senegal. It is
noteworthy that boatbuilders could be trained from
house carpenter stock in as short a period as about a
year. Two boats were built during the first course, while
two more 42.6ft (13m) boats and one 52.5ft (16m)
purse seiner (fig 30 and 31) are under construction with
the second and third group of trainees. It is estimated
that henceforth some 10 to 1 5 boats will be built annually.
42.6 ft (13 m) trawler (fig 22)
The success of the handline fishing boat (fig 20 and 21)
sparked considerable interest in small boat development
in Senegal and the same lines were used for the construc-
tion of a prototype trawler. The boat will be primarily
used for shrimp trawling and for training fishermen at
the Dakar school of fisheries.
42.6 ft (13m) seiner (fig 23)
One of the first design development projects undertaken
by FAO concerned the survey of the then existing
Turkish fishing fleet and the preparation of a number
of designs of improved local type boats such as the
42.6 ft (13 m) seiner shown. It is conceived for construc-
tion to local building standards by established boatyards.
It does not therefore depart substantially in shape and
outward appearance from traditional types. The con-
struction, however, is considerably altered and modern-
ized.
39.5 ft (12 m) shrimp trawler (fig 24)
This constitutes a noteworthy example of the develop-
ment of a modern, mechanized inshore fishing vessel in
Taiwan. It is a combination of the traditional Taiwanese/
Japanese boat and the modern USA west coast com-
bination boat. The stern shape is a concession to the
local builders who traditionally build flat cruiser sterns,
[438]
TABLE 2
Main particulars of boats presented in fig 1 to 33
^\ Boa*
Bat a ite»\^^
HB-59
HTDI1
tit 1
25 ft
XIDIA
fi« 2/3
E 26
CEYLON
f 1« 4/5
30 ft
IKDU
fi« 6/7
B 32
CBYLON
f iff 8
32 ft MkZV
XVDXA
fl« 9/11
32 ft Mkl
ZIDZA
fig 12/13
36 ftNklZI
ZKD1A
fig 14/16
38 ft
CBTLOI
fig 17
Loa ft
•
24
7.32
25
7.63
27.5
8.39
30
9.12
32.12
9.8
32
9.76
32
9.76
36
10,97
38.08
11.63
Lvl ft
m
20.37
6.2
23
7.02
24.75
7.54
28
8.52
31.33
9.55
28.17
8.58
29.25
8.89
33.25
10.13
35.1
10.71
B max ft
•
7.54
2.3
7.17
2.18
8.33
2.54
8.17
2.48
9.75
2.97
9.5
2.9
9.5
2.9
[,,,
3.5
12
3.66
Bwl ft
•
6.06
1.85
7
2.13
7.5
2.2?
7.58
2.31
8.5
2.59
9.38
2.86
9.38
2.86
10.83
3.31
11.79
3.6
D ft
M
3.25
abt.
.99
3.55
1.08
4
1.22
4.08
1.24
4.58
1.43
4.17
1.27
4.13
1.26
5.35
1.64
5.38
1.64
d mean ft
m
1.33
.56
1.67
•51
1.67
• 51
2
.61
2.17
.66
2.5
„. /76 -
2.5
_ :_76 _
3.25
•99
3.67
1.12
d max aft ft
HI
1.83
.56
2.5
.76
2.25
.69
2.83
.86
3
.92
3.5 "
1.07
3.25
•99
4.42
1.35
5
1.53
F nin ft
•
1.8
abt.
.55
1.75
.53
2.25
.69
2.08
.63
1.08
.33
1.5
.46
1.5
.46
.61
1.71
•52
V»l °u ft
ou m
A light
abt. 1*3
ton§
9B
2.77
114
3.22
161
4.56
217
6.14
255
7.24
262
7.43
428
12.22
621
17.55
Flahhold ou ft
capacity
ou m
-
-
not
•pacified
-
130
3.7
200
5.7
240
6.8
350
9.9
Fb hp
10 - 15
10 - 15
15-20
20 - 30
24
40
30
60 - 70
50 ~ 70
Engine *ake
Paraont
Fetter
Bukh
Yanmar
Litter
Fetter
Fetter
Lister Bukh
Tanmar
Lister
Fetter
Huston
Ferkins
Huston
Kirloskar
Lister
Huston
Bukh
Fuel oil lap gal
1
10
abt.
45
10
45
not
specified
not
specified
not
specified
117
530
100
450
220
1000
265
1200
Fr« eh Imp gal
water
1
-
-
*
-
not
specified
29
130
25
115
60
270
133 j
600
Insulation
™
insulated
fiah box
part of
hold epaoe
-
•
expanded
plastic
foam
expanded
plastio foas
reoomiended
expanded
plastic
foaa
not
specified
Accommodation
.
_
.
-
-
-
-
2-3
4
Deck machinery
-
-
Vertical
gurdy
Trawl winch
vert, gurty
neoh. drive
Vertical
line-
hauler
Trawl winch
meoh. drive
Vert, curdy
•eoh. drive
Trawl winch
•eoh. drive
Trawl winch
meoh. drive
Purpose
Boaoh fi-
shing (turf
landinc)
Oillnet
Shrimp
trawl
Oillnet
Trawl
Oillnet
Lonffline
Oillnet
Shrimp
trawl
Oillnet
Shrimp
trawl
Trawl
while the layout is modern and well suited to shrimp or
bottom fish trawling in limited depths of water around
the island of Taiwan. The design is by a Taiwanese naval
architect on the staff of the Provincial Directorate of
Fisheries in Taipei.
49 ft (15 m) trawler-drifter (fig 25 to 27)
The design was produced under the guidance of an FAO
naval architect by a participant at a training centre
directed by FAO for small boat design in India. At the
time it filled the gap between traditional boat types and
modern off-shore trawlers in the states of Gujarat and
Maharastra on the Indian west coast, where an im-
portant continental shelf exists off the major distribution
centres of Veraval and Bombay. The boat is of heavy
construction suitable for locally grown timbers — and
some hulls were built in 1961 to 1963 by a co-operative
boatyard at Satpati, The cost of the vessels was too high
(£8,600-824,000) to make them suitable for independent
skipper/owners, but those built are very successfully
operated by the state directorates of fishery in Gujarat
and Bombay and a fishermen's co-operative.
[439]
TABLE 2— continued
^v. Boat
Data it*»\.
42 ft
IVDIA
fi« 18/19
13 m
SERQAL
fig 20/21
13 »
TDRKSY
fif 23
12 *
TAXVAF
f i« 24
49 ft
XXDU
fig 25/27
16 »
THAILAND
fig 26/29
16 *
SBFEOAL
fig 30/31
18 m
TUKKDY
fi« 32
66 ft
Bova KOIO
fig 33
X*a ft
m
42
12.6
42.6
13
43.2
13.18
44.33
13.5
49
14.94
52.32
15.95
52.33
16
60.55
18.48
66
20.1
Lvl ft
n
38.38
11.7
39.35
12
38.9
11.87
40.33
12.3
45
13.72
47.92
14.61
48.71
14.85
53
16.16
59.5
18.15
B »ax ft
m
13
3.96
12.47
3.8
12.6
3.84
12.75
3.89
13.5
4.11
13.05
3.98
15.42
4.7
18.37
5.6
20
6.1
Bwl ft
«
12.92
3.94
12.14
3.7
11.29
3.44
12.75
3.89
13.12
4
12.35
3,77
15-42
4.7
16.7
5.08
20
6.1
9 ft
A
6.42
1.96
5.74
1.75
5.11
1.56
5.57
1.7
6.2?
1.92
6.62
2.05
8.2
2.5
7.21
2.2
8
2.44
d MOM ft
m
4
1.22
3.61
1.1
3.15
.96
4.29
1.3
4.25
1.3
3.96
1.2
5.5
1.68
4.16
1.27
5.5
1.68
d nax aft ft
m
5
1.52
4.92
1.5
4.26
1.3
5-75
1.76
5.33
1.63
5.44
1.66
6.63
2.02
6.07
1.85
7
2.13
F min ft
M
2.25
.68
1.97
.6
1.87
•57
1.46
.44
1.75
•53
2.65
.81
2.38
•75
2.1
.64
2.5
.76
V»l ou ft
OH Bl
780
22.1
670
19
654
18.55
1130
abt.
32
1050
29.7
1093
31
1395
49.2
1490
42.1
2700
76.5
Fishhold ou ft
oapaoity
ou •
180
5.1
423
12
not
epeoified
285
abt.
8
520
14.7
918
26
805
22.8
565
abt.
16
700
19.8
Pb hp
90
60 - 75
30 - 50
60
80 - 100
90
120 - 150
150 - 200
200
Ingine make
Kelvin T3
Baudouin
nc
Deute
Yannar
Daiya
Lister
Kelvin T3
Cunnine
Baudouin
IK
Deuts
Gardner
Fuel oil Xapgal
1
340
1530
310
1400
132
600
660
abt.
3000
440
2000
670
3040
970
4400
440
abt,
2000
2200
abt.
10000
Freeh lapgaJL
water
1
110
500
88
400
61
275
185
850
150
680
83.5
380
286
1300
220
abt.
1000
440
abt.
2000
Insulation
expanded
plaetio
foam
expanded
plastic
foam
™
Deokhead
3idee
only
expanded
plastio
foan
Bulkheads
expanded
plastto foam
expanded
plastio
foan
~
expanded
plastic
foam
lOOONROdatiOB
6
6
2
6
6
7
11
2. 4
6
Deofc Machinery
Trawl vinob
vert, gurdy
neon. driTe
Vincb or
gurdy pos-
sible
Warping
druse
Travl vinoh
•eoh. drire
Trawl winoh
vert, gurdy
•teoh. drive
hravl winoh
combin-
ation)
Purse vinoh
Power blook
hydr. drive
Travl vinob
neoh. drive
Travl vinoh
me oh. drive
Purpose
Trawl
Oillaet
Research
Bandline
Seining
Trawl
Trawl
Oillnet
Trawl
Purse seine
Purse seine
Trawl
Travl
52.5 ft (16 m) stern trawler (fig 28 and 29)
Designed by an FAO naval architect on duty in Thailand
in 1961, boats of this type should prove a valuable
addition to the Thai inshore trawler fleet. While the
scantlings are comparatively light, they are heavier than
those of present built boats and that has prevented the
design from being built.
52.5 ft (16 m) purse seiner (fig 30 and 31)
When the success of the first boatbuilding training
course in Senegal became apparent, the Government
Fisheries Service decided, in consultation with the FAO
naval architect and boatbuilder, that the second course
should build a larger boat suitable for the sardine
fishery off the coast of Senegal. Limitations imposed by
the capacity of the yard restricted the vessel to 52.5 ft
(16m) length overall. The prototype of this boat is now
nearing completion and is scheduled to be commissioned
early in 1967. It will serve as demonstration and training
vessel under an FAO master fisherman. The boat is
designed to operate a sardine purse seine with an
hydraulic purse winch and a power block. The catch
will be stored in four insulated tanks in chilled sea
water.
[440]
59 ft (18 m) trawler (fig 32)
Similar to the boat shown in fig 23, this design was
prepared by an FAO naval architect in Turkey in 1957
with the same objectives in view as for the 42.6 ft (13 m)
seiner.
66 ft (20 m) trawler (fig 33)
This represents the final link in a long development chain
in Hong Kong. It is hoped that this boat will finally
convince the Hong Kong fishermen of the advantages
of modern designs over the traditional 'junk'. It is a
single boat otter trawler and should play a major role
in changing the trawl fishery from an inshore to an
offshore one, to supply more and higher quality fish to
the insatiable Hong Kong market. The design was
prepared by a Chinese naval architect on the staff of
the Hong Kong Department of Fisheries. The first boat
to this design is now under construction for a private
fisherman aided by a Government subsidy scheme;
therefore, no trial results are available.
PERFORMANCE
Current work undertaken by Doust and Traung (page 123
and 139) in utilizing computer techniques for the pre-
diction of ship resistance for smaller vcbsels made it
possible to investigate the applicability of these techniques
to performance prediction for some of the boats shown
in fig 1 to 33. Table 3 gives the parameter for these boats.
It was found that the regression equation now available
for this work could only be applied with accuracy for
three of the selected boats (fig 18, 20 and 25). The
parameters of the others were outside the range of the
initial parameter data, and the results of an investigation
outside this range might well be incorrect. Fig 34 shows
the three EHP predictions obtained from the computer
and a comparison with model test results and full scale
trial results for the 49ft (15m) trawler/drifter (fig 25)
and the 42.6ft (13m) handline fishing boat (fig 20)
respectively. No comparison material is available as
yet for the 42 ft (12.8 m) fishing boat (fig 18).
49 ft (15 m) trawler/drifter
The original Kharagpur model test results were corrected
at NPL to make them comparable to the values obtained
from the computer programme. This involved re-
calculating the model test results to the same basis of
infinite water and to allow for the effect of blockage due
to the use of very small models. The agreement between
computed and measured results is good, and in line with
general experience when using these techniques.
42.6 ft (13 m) handline fishing boat
In the lower speed ranges the computed EHP bears little
relation to the EHP obtained from full scale trials.
From about V/N/L=1.175 upwards the trend of the
curves is similar. The trial i!HP values are based on an
assumed efficiency of 50 per cent and are furthermore
subject tr, error due to the difficulty of correctly evaluat-
ing BMP at different engine rpm. It has been found from
other efforts to determine BHP from fuel consumption
measurements that this gave too high values at low
engine loading, and it is felt that full scale trial results
would only be reliable and comparable to computed
EHP if based on torsion meter readings. The correlation
is further complicated by the fact that the trial EHP
applies to L/V* = 4.97 while the computed EHP applies
to 4.45.
The main conclusions that can be drawn from the
comparison arc:
• An extensive programme of model testing is
required to extend to very small boats the range
of applicability of the regression equation used
(continued on page 474)
TABLE 3
Design parameters for computer analysis
L
A
L
Vtt
L
B
B
T
Cm
Cp
LCB
1/20C°e
fecx?
CX°BS
Trim
32 ft CEYLON fig 8
28.90
3.60
5-89
3.73
4.70
.534
.639
-2.09
22
54
9
0.026
32 ft INDIA fig 9
28.167
7.23
4.45
3.00
3.75
.675
.569
-3.59
22
51
14.5
0.036
36 ft INDIA fig 14
33-25
11.9
4-45
3.07
3.30
.606
.581
-1.65
25.5
52
15
0.040
42 ft INDIA fig 18
38.38
23-1
4.06
2.97
3.23
.677
.602
-1.75
29
57
18
0.039
13 m SENEGAL fig 20
39-37
19-65
4.45
3.20
3.24
.670
• 552
-1.50
26
40
16
0.043
49 ft INDIA fig 25
45-00
30.1
4.43
3-41
3.10
.700
• 595
-1.19
25
55
17
0.038
16 m THAILAND fig 28
47.93
31.2
4.65
3.88
3.14
.790
.578
-3.17
20
53
12
0.042
16 m SENEGAL fig 30
46.26
38.15
4.2
3.03
3.26
.694
.580
-2.61
24
57
16
0.069
66 ft HONG fig 33
KONG
59-5
77-2
4.28
2.98
3.64
.732
.563
40.24
22
47
15
0.037
[441]
LAYOUT
ffc'i"' !
f
IHJL
•^SC
nh
— U. "-
cohort™,!.
EnQin* uodtf
p. "~ -7 -3
S2J
-ic^^
:--: ---—
-1
SS?^±!
_— -'/
(7J w) beach/ surf boat
Fig 2. 25ft (7.6 m) open fishing boat
rr" - rr:"^^ .- .-, * ,
' 'I ' ;i , 'i
. 25 // (7.6 w) openfiahint; boat
4 a «
Fig 4. 27 ft (8 w) fishing boat E 26
•IA 9 9ut
[443]
ti_ . __ _1_'" » \ -- ••% '•>
. - - v 1-. _ : .-.i /'IA'~r'"**' " '»;"*" 'TOP OF DECK , j<.
• . i •* iv ','.'. '!' " _Ilr'
WITH 3 TONS LOAD
Fig 5. .?0// (9.7^ w) Madras fishing boat
F4441
Fig 7. SOft (9.14 m) fishing boat. Layout as trawler/gillnctler
[445]
[446]
i \ : ! I •!/ J.I '
, .H ,, Uj— .HT-^ ••/:/ •• i
5!
OS'
[447]
q 2
I±E
4 C
T - 1 i
0 0.5 I.O 1.5 2.0 2.5
!
I
/*£,
111
Ji
. _»
"""'I I "_ ~
i \ r " : •
l-\ — -+-- —
UJ \- ---"
^— • •'-- . — ,
_ ^
L/"
I A
IL 1- -
F/^ 10. 32ft (9.75 in) frtfH'fer Mk IV
[448]
[449]
[450]
1 K :VN V
HH-v-t
1 \
..-> u.
AC.
Fig 13. 32ft (9.75 m) fishing boat Mk I
[451]
P2
4s
I-
I
[452]
I
2
[453
75(6). P/a/? arrangement of 36 ft (11 m) shrimp trawler Mk HI. Scale also applies to fig 15(a)
[454]
» '// ;/ .'':' / / / . 1 E'xf 1 "'
' HU-__ ^^.,
T!f I
1
^£S---UEi- t
n
[455]
Fig 17. 38ft (11.6 m) trawler— Ceylon
^, 42 /r (/.? m) fishing vessel
456]
Profile
Hinged platform
LT^T
m winch
!T.
Bottl. rack
fciidlA-^
0«sk
lEchfi
Berth
\
I~T:
Li
Deck layout
Under deck
Fig 19. 42 ft (13 m) fishing vessel
[457]
I IK2 2 21/z 3 4 5 6 7
F/*r 20. 42 // (/J m) handline boat— Senegal Mk //////
8 8X2 9 9fc 10
riiirijL
US
iJJjLi
ill! IT!' HIT 7TD'
$XJ-jj
27. 42 // (7J m) handline boat— Senegal Mk III
[458]
51
S--JTm— IT--- 4 r-"-3"-^"-- -"-- Hii-
r:^-v-:l-l 1 irT^-r --T-
r-JLTflr- : n-i-Tr^ •:.-*-. liL 'i ., .
F/y 22. 42 /» (7J /w) trawler— Senegal Mk III III
[459]
Soalft FMtt-1— J I , t~ » f , I T I
««0lt Mtt^lT J^-^J-^.'-j^ £
/j? 2>?. ^2/r (13 m.) seiner— Turkey
[460]
PI III lilt
X
. . .- -
/ i -,f— r^- ^..-'--""
^, _. . _/ 1 ^,^_-_-r.-i: _ __
i AP .", I "2 " 9
-1--
(72 w) trawler — Taiwan
[461]
I 4SM (14 94m >
4Sft (1372m)
*
s
1«P-*3
S-;fS?
'K
/fl
B'«<>l£-5*=---~rq
;=•="•• "VL^-""-— -*
:.-•];,..
~.-T7j
r^_^_
r---"""i
^-=^r-^=—
i
__^- ___ 4^ _
!
p-'-l^
~.*~-- ._*"•--- *"~-f
"--..._"-— .^---i
-•Jt"
'1
-'t:::5i
tT,_ i
i 1
. -. ii —
.. i ._ j±
Fig 25. 49ft (15 m) drifter-trawler
[462]
Profile
j i
3 4
K>
Originally proposed layout
o 2 4 c e 10 12
• v "^" T '
I b«om spoc« for'
Layout proposed by GIFT Gear Brooch
Under deck
Fig 26. 49ft (75 m) drifter-trawler
[463]
•a i li-
"|7^. j[.j..li._
/
i : !| I i
:'^±u:iiL.Ar=ih!,:fifJ- -..4.1.3...^
1 I
il
BEAMS, CARLINS
f& 27. 49 ft (15 m) drifter-trawler
[464]
[465]
rig 29. 52ft (16 m) stem trawler
fe-
K^ 30. 52 ft (16 m) purse-seiner-Senegal
[466]
52ft (16 m) purse-seiner
[467]
£
I
|
?
QO
[468]
Hg 33. 66ft (20 m) stern trawler— Hong Kong
[469]
EHP
EHP from computer
EHP from trials assuming m*
EHP from tank test at Kharagpur ( India)
/42ft IND
' FIG 18 /
13m SEN
FIG 20
Speed in knots for Lwl
10
1.0 L05 I.I
Fig 34. EHP predictions
1.25
V/VT
[470]
Mock el lines
Suggested range of
good stability
8 16
Fig 35. Rolling period ax a stability criterion
GM«(f
Tender limit for B» 2m
Tender limit for B-4m
Tender limit for B«6m
Fig 36, CM as a function ofT^/B(m)
[471]
USAS
35000-9000
20000
7000
tsooo
5500 --
10000
3500
500C
1600
O Actual cost
O Estimated cost
Joi
Japan
Ghana
Shrimp trawlers/
"(India) ~
Australian boat*
//
/Handline boats
" (Senegal)
.Purse seiners
f (Senegal)
(fig 29
20
3O
40
-P-
Loo ft
Fig 37. Cost trends for wooden boats
m
[472]
£, isLooo
USA S 4OOOO
.?#. Weight and cost relative to LI V
[473
in the computer work. This testing programme
must comprise boats of widely differing charac-
teristics of the parameters that exert a major
influence on the performance of a hull
• Full scale ship trials for the models tested and
computer analysis are essential to obtain a clear
indication of the magnitude of correlation factors
that might be required to allow computer pre-
dictions for very small boats to be used in the
design stage. Exact power determination with the
help of torsion meters is essential. Trials must be
run at A, L/V* and trim values corresponding
closely to those used for the respective computer
analysis— and model tests
STABILITY
Very little is known on the minimum permissible stability
of small, wooden fishing boats. It is of importance to
ensure that these boats have comfortable motions but
retain sufficient stability to satisfy the requirements of
safety in extreme weather and loading conditions. A
minimum stability criterion for small fishing boats has
not yet been formulated but the adoption of Rahola's
criterion for static and dynamical stability has been
suggested repeatedly. Small boat stability is often
assessed by various rule of thumb methods, perhaps the
most well known being that the period of roll should be
about equal to the boat's beam in metres. This should
satisfy the need for comfortable motions together with
sufficient stability. In fig 35, actual rolling periods for a
number of small wooden boats are plotted on the basis
of beam; for comparison the lines given by MOckel
(1960) are shown. All the plots, with one exception,
represent boats fulfilling Rahola's criterion. The boats
are in a range having length-beam ratios of 3.0 to 4.0
and length-displacement ratios of 4.0 to 4.6 and most
are among those shown in fig 1 to 33.
Traung (page 139) shows that the minimum permissible
GM to fulfil Rahola's criterion increases with length
(maintaining L/B and L/V* constant). This indicates that
M0ckel's lines for large trawlers could result in an un-
necessarily high GM if applied to much smaller boats.
The suggested range of good stability shown in fig 35
substantiates this view on the basis of practical experience.
Freeboard is not considered in fig 35, but naturally
plays an important role in minimum stability determina-
tion as shown by Jablonski (1960) and Traung (page 139).
A diagram that could be applied to check stability on
small boats is shown in fig 36. It is based on the Weiss
jg
formula GM«(f=)2 (metric units) and together with
fig 35 serves to indicate more clearly the limits of the
experience rule T^wB in m for safe GM. By using the
limiting lines suggested in fig 35 it is possible to define
T^/B values for safe stability, with a corresponding
range of GM values depending on f, for any particular
beam. Such ratios are shown for B«6.5ft (2m),
B«13ft (4m), and B«20ft (6m). The respective
"tender" limiting line indicates safe GM for rolling
periods below 2.5, 4.4 and 6.3 sec respectively. GM
values are plotted against beam for f=0.78 and 0.82.
It would appear safe, therefore, to suggest that small
boats of normal proportions up to a beam of 20 ft (6 m)
are satisfactory from a stability point of view if they have
a rolling period of less than LIB in m. To substantiate
this statement, it is necessary to see which minimum
freeboard this would produce. Rolling periods below B
in m should be avoided for the type of boats under
discussion, as they would result in decidedly stiff motions.
Again, this depends naturally on freeboard, which is not
included in this analysis as most of the boats presented
have ample freeboard even in the full load condition.
From the available reliable data of B, T^ and actual
GM of small wooden boats, it is not possible to deduce
generally applicable values of f for different loading
conditions. A careful investigation of the stability
properties of a large number of boats is necessary to
obtain a clear indication of f values to be applied for
specific loading conditions and the appropriate ranges
of parameters such as L/B and L/V*. The minimum
permissible GM to satisfy an acceptable criterion of safe
stability should be investigated for the same range of
these parameters and also for a parameter expressing
freeboard in terms of beam. This latter could be related
to the actual loading conditions of fishing vessels. The
results would allow conclusions regarding the permissible
GM and T^ for fishing boats to be drawn, and presented
in a form similar to those of coastal cargo vessels given
byThode(1965).
Of all known methods of checking the stability of
ships, the application of the Weiss formula appears to
be the simplest and easiest, provided that reasonably
accurate f values can be established to cover the range
of loading conditions occurring for any given type of
ship.
WEIGHT-COST DATA
There is an astonishing lack of reliable data of actual
construction weights for wooden boats in most countries
but particularly in those having a relatively new boat-
building industry. It is almost impossible for the designer
to find reference material that will allow him to judge
with some degree of accuracy the light weight of a new
proposed vessel. In general FAO naval architects suffer
from this difficulty in obtaining suitable data from small
boatyards because such yards are not used to keeping
careful records. In many cases boats to their design were
built in remote areas or after their departure. It is often
as difficult to obtain reliable draft readings of the finished
boat, together with a careful summary of weights on
board, to allow a calculation of light weight to be made
on the basis of available hydrostatic curves. The technical
assistance mission to Senegal operated under much
better conditions in this respect. The combination of
boat design and boatbuilding training in a small boat-
yard under the active control of the naval architect and
boatbuilder from FAO made it possible to collect
reliable data of weights and costs of the boats built.
Table 4 gives the material and labour requirements
for five representative boats, four of which were built in
India and one in Senegal. The 42 ft (12.8 m) fishing boat
from India and the 42.6ft (13m) handline boat from
[474]
TABLE 4
Basic construction material and labour requirements
ITEM
fig 2/3
25 ft IND
fiff 9/11
32 ft IND
fig 14/16
36 ft INT
fl« 18/19
42 ft IND
fig 20/21
13 • SEN
Boat building timber ou ft
180
700
1050
1400
1100
(logs) ou a
5
20
30
40
31
Copper rod and nails Ibs
110
400
500
660
galv.iroa
440
washers, nuts kg
50
182
227
300
oa 200
Spikes and nails Ibs
65
110
130
200
leg
30
50
59
90
Screws gross
18
75
100
150
inol.
above
Copper sheet sq ft
150
400
500
620
645
sq m
14
37
47
58
60
Paint, glue Imp. gal
17
25
3b
45
55
1
72
114
160
205
250
Insulation material sq ft
250
300
350
480
(expanded plastic foam) sq m
23
28
32.5
45
Labour man days
( ino luding installat ion
of machinery and equipment)
500
1200
1700
2200
850
Senegal are very similar, not differing substantially in
main dimensions. The lower requirement for boat-
building timber in logs for the Senegal boat is explained
by the better utilization of the logs due to careful planning
and the fullest use of power tools, resulting in a con-
siderable reduction of waste. The same applies to the
labour requirements, the Senegal boat requiring only
38.5 per cent of the man days needed to build the 42 ft
(12.8m) boat in India.
The detailed weight breakdown for the 42.6 ft (13 m)
handline boat is given in table 5 as an example of the
degree of accuracy that can be obtained if careful records
are kept.
Table 6 gives a cost analysis for six boats. It lists sep-
arately hull costs, the cost of insulation, electrical fittings,
equipment, labour, and overheads and profit, but
excludes the cost of main propulsion machinery. It is
seen that hull costs as a percentage of total cost decrease
substantially with increasing size and complexity of the
boat. Cost of insulation clearly depends mainly on the
price of insulation material, which is very high in India,
while electrical installations remain quite constant.
Equipment costs naturally increase considerably with
boat size due to increased complexity of equipment. In
the case of the Indian boats profit and overheads indi-
cate that the construction of bigger boats is less attractive
for the small boatyards concerned. This may be largely
due to the lack of work planning, and would also
substantiate the view that bigger boats tend to require
larger margins in cost estimation due to an increase in
unforeseen complications. The labour cost provides
interesting insight into the large variations existing
between different countries. If the man day requirements
in table 4 are compared, it is seen that the 850 man days
needed to build the 42.6 ft (13 m) Senegal boat represent
27.7 per cent of the total cost of the boat, while the
1,700 man days required for the construction of the
36 ft shrimp trawler in India represent only 13.5 per cent.
The cost per man day of labour in Senegal is four times
higher than in India. In the cost comparison, it is seen
clearly that even with high labour costs it is possible
to keep the overall cost down to a reasonable level,
provided fullest use is made of pre-planning, labour-saving
methods and tools. Conversely, low unit labour cost
does not guarantee low total costs.
The problem of realistically assessing costs of boats is
especially grave in developing fisheries as the basic
data for comparison is largely missing. On the other
hand, it is of importance to provide safe guide lines to
those concerned with economic planning. Only too often
;475]
are boat costs assessed unrealistically. Fig 37 gives the
costs of a number of boats in relation to their overall
length. It is impossible to extrapolate from this an
average relation that could be valid on a world wide
basis. Too many geographical and other factors would
not permit this. Fig 37 indicates, however, that the boat
prices plotted fall into a reasonably well defined area.
The spread in costs for a given length is determined by
the type of construction adopted, applicable labour
costs and to a large extent by the type, and amount of
equipment installed. It is interesting to note that this
spread is about 100 per cent throughout the range for
length and types shown. Costs of main propulsion
engines are omitted throughout since they fluctuate
widely due to tariff restrictions, freight charges and the
like.
Fig 38 is an attempt to show boat costs in relation to
weight with L/V* in the light condition as a parameter.
It is seen that considerably more reliable data is required
TABLE 5
Weight estimate for 42.6 ft (13 m) handline fishing boat
GROUP
WEIGHT
ITEM
Ibs
*«
A
HULL STRUCTURE
A 1
Backbone
WO
704
Worm shoe
66
30
Transom knee
56
?6
Stem knees
44
20
A 2
Planking
4000
1020
Transom and frame
286
130
Butt blocks
110
50
A 3
Bilge stringers
725
330
Clamps
?85
130
Clamp forward
76
35
A 4
Frame o and floors
3240
1473
A 5
Bulkhead
81
37
Double bulkhead
LM2
110
Double bulkhead
L'10
96
Bulkhead
81
37
A 6
Deck beams
1160
527
Deck planking
1710
780
Girders
415
188
Brackets
198
90
Blocking
42
19
Tie rods
20
9
A 8
Engine stringer
242
110
Sngine bed
?B6
130
A13
Rubbing strake
185
84
A14
Bulwark oap and lining
620
280
Sub total
15950
7245
A 15
Fastenings (5c/t)
796
361
Total A
16746
76U7
fe
SUPERSTRUCTURE
» 1
Aft cabin
529
240
'iVheelhouse
815
370
Engine room entrance
143
65
B 3
Coaming and hatch
154
70
Entrance forwd. cabin
115
52
Aft platform
97
44
Total B
1853
841
to indicate whether such a presentation could be usefully
adopted. However, as far as the boats plotted in the
vicinity of L/V*=4.5 and 5.25 to 5.5 are concerned, a
good representation of their costs is obtained by the
respective cost lines.
Diagrams of this type must be used with great caution
and require a good understanding of cost trends in
general and local trends in particular. It is suggested
that such parameter diagrams could be employed in the
planning stage of fleet development, if they were pre-
pared on a regional basis. To simplify the presentation,
a base of L x B x D might be used and costs could be
plotted per unit volume. The resulting parameter lines
would then be straight lines. It is feared, however, that
the error in extrapolations would be considerably
larger than with the suggested parameter presentation
shown in fig 38.
The lack of reliable data makes it imperative to con-
sider the presentations under Performance, Stability and
Weight-Cost Data as indicative only of work to be
expanded in the future. Whether this work can be
TABLE 5— continued
QBOUF
WEIGHT
ITEM
Ibs
Kg
C
JOINER WORK
Aft cabin berths
172
78
flooring
110
50
lining, etc.
44
20
Forwd. cabin berths
flH
40
flooring
66
30
lining etc.
44
:.'0
Fish hold lining
507
230
Insulation
44
?0
Hold partition.'!
331
150
Ladder
15
7
Engine room flooring
66
30
.Steel brackets
31
14
Ladder
31
14
Sub total
155?
703
Faistenin«n (^)
84
38
Total C
lo 36
741
D
HULL FITTINGS AND EQUIPMENT
D 1
Windows, portholeo
33
15
H 3
Fuel tanks (incl. b locks j
8HO
400
Water tanks
13''
60
D 4
Hudder and ntook
166
7!;
Ste«rin£ arrangement
lib
:iO
Chain, pij>«, jnjlloy:.;
110
50
fi 6
Bitt forwa.
<L£
10
JJitts aft
ib
tt
Chain locker
22
10
Ventilators
33
15
Hub total
1483
673
Fastenings (5/*)
66
30
Total D
1549
703
E
RIGGING
E 1
Liaat
176
80
£ 2
Standing rigging
44
20
Total E
220
100
[476]
TABLE 5— continued
OROOP
i mi
WEIGHT
Ibs
kg
?
MACHINERY, PIPING
F 1
Main engine and gear
2400
1090
F 3
Shaft and couplings
Stern tube
132
66
60
30
F 4
Propeller
90
41
F 6
Eihautt line
77
35
F 7
Controlo and instrunente
33
15
F 8
Cooling system
33
15
F 9
Fuel line
11
5
F10
0
Air bottle and fixing
110
50
Total F
2960
1341
SHIP STSTB4
0 8
H
Galley box, gas bottle
154
70
ILSCTRXCAL
H 1
Switchboard
22
10
H 2
Batteries
88
40
H 5
I
Wiring and lights
22
10
Total E
132
60
OUTFIT
I 1
Anchor
Chain
Rope
117
430
66
53
195
30
I 4
Tools and spares
88
40
I 6
Navigation equipment
44
20
I 9
Bedding etc.
176
80
Total I
922
418
SUMMARY
A
HULL STRUCTURE
16746
7607
B
SUPERSTRUCTURE
1853
841
C
JOINER WORK
1636
741
D
HULL FITTING EQUIPMENT
1549
703
X
RI GOING
220
100
F
11ACEINSRT
2960
1341
0
SHIP SYSTEM
154
70
H
ELECTRICAL
132
60
I
OUTFIT
922
418
J
SOAKAGE, BILGE (5 % of A -»• B + C)
1013
459
K
COPPER
815
370
L
PAINT (3 £ of A 4 B + C)
606
275
TOTAL
28606
12985
Llf ht weight from weight estimate —
Light weight from trial records •»
Error in weight estimate =
12.75 tons (12985 kg)
12.23 tons (1 2450 kg)
4%
undertaken or not depends to a large extent on relevant
data being submitted for evaluation.
In view of its importance and established place in big
ship design, the further development of the computer
analysis technique is required to make this aid to design
available also to the designer of small boats. Of utmost
urgency in this connection is the widening of the range
of the parameters through comprehensive model testing
programmes.
Considerable uncertainty exists regarding the required
stability of small fishing boats. The formulation of a
simple criterion to assess minimum stability require-
ments in the design stage for the widest possible range
of boats is of utmost importance, as is the establishment
of a simple and accurate method of stability assessment
for existing boats.
More attention should be paid to the collection and
evaluation of data on weight and cost of small boats in
order to be able to prepare graphical guides for the pre-
asscssment of boat costs in connection with the develop-
ment of inshore fleets.
THE PLACE OF BOAT DESIGN
IN FISHERIES DEVELOPMENT
Of the multitude of factors that point to the necessity of
a planned approach in boat and fleet development, the
following are of special interest:
• Boatbuilding has always been a traditional
industry. In many parts of the world boatbuilding
practices have stagnated and have not progressed
with general technological development
• The scientific approach in naval architecture is
comparatively new as is its growing influence on
the design of fishing vessels. Earlier evolution of
new types of vessels was by trial and error
• The traditional boatbuildcr cannot predict the
performance and behaviour of a new boat if its
conception departs substantially from the accep-
ted and familiar. He is, therefore, reluctant to try
radically new ideas. Modern naval architecture
provides the designer with the theories required
to predict performance and behaviour of new
boats
The application of these theories and the use of
advanced computing techniques for hydrostatic, stability
and performance calculations make fleet development
possible with predictable results.
Four phases of development are generally apparent :
Mechanization of indigenous craft (canoes, log rafts,
simple planked boats)
By fitting outboard or inboard propulsion motors.
Design adaptation of indigenous craft
By introducing small changes in shape and construction
to adapt the craft to modern fishing techniques. Transi-
tion from man power or wind propulsion to power boat.
[477]
TABLE 6
Cost of boats in India and Senegal (excluding main propulsion machinery)
BOAT
fig 2/3
25 ft IKD
fig 7
30 ft IKD
fig 9/11
32 ft IMD
fig 14/16
36 ft IHL
fig 20/21
13 m SEN
fig 30/31
16 • SEI
ITEM
$
*of
Total
$
#of
Total
I
*of
Total
$
«of
Total
$
* of
Total
1
for
Total
Hull (tinter, fastenings
oopptr »h««t, paint)
900
50
1790
58.7
3900
48.1
5780
43.7
4110
35-5
8370
28
Insulation
525
6.48
1050
7.9
205
1.77
510
1.7
Eltctriotl fittings
315
3.9
525
3-97
310
2.68
1020
3.4
Equipment (inol. dtofc
•achintry)
420
13.75
1680
20.7
2950
22.23
2500
21.6
7850
26.3
Labour
630
35
525
17.2
1050
13.0
1790
13.5
3200
27.7
6520
21.85
Orarhaad and profits
270
15
315
10.35
630
7.82
1155
8.7
1260
10.75
5600
18.75
Total
1800
100
3050
100
8100
100
13250
100
11585
100
23870
100
Introduction of foreign boat types
Extremely tempting in cases where design adaptation of
indigenous craft cannot be made or where economic
reasons render an immediate fleet expansion essential.
Reasons against the application of this phase are:
• Financing generally requires foreign exchange
and newly developing fisheries with little or no
export potential find it difficult to recover the
foreign exchange invested
• Operation of whole fleets of foreign boats can
create maintenance problems. The development
of maintenance facilities often lags considerably
behind if fleet development is too forced
• Wooden fishing boats up to 50ft (15m) length
can be built in nearly all countries with potentially
important fisheries. The development of an
indigenous boatbuilding industry should not be
prevented by limiting fleet development to import-
ing foreign boats. The chapter headed Weight-
Cost Data shows that local boatbuilding prices
need not be higher than abroad
Main factors in favour of this phase are:
• To provide ships for large scale off-shore opera-
tions in countries without a specialized ship-
building industry
• To provide ships for special duties such as
experimental and/or exploratory fishing, research,
fishery protection, fishery assistance
Most developing countries lack the facilities to build
such ships locally.
Development of national or regional boat types
This is highly recommended as it allows fishing fleets to
develop in close association with general expansion of
industries in any one country or region. Employment
created in this way could be a considerable economic
advantage, and the advantage of the possible creation of
auxiliary industries should not be neglected.
This ultimate phase must be directly connected to
general fisheries development and requires qualified
technical personnel closely associated with or attached
to the Fisheries Administration. Design development
costs will normally have to be borne by governments;
the fishing industry could in a later stage participate in
sharing such costs, when the development work starts to
provide sufficient capital resources.
It is essential that the government organization
charged with boat development is not considered a
competitor of private enterprise, but that it acts as a
catalyst, adviser, and correlator.
No quick results can be expected during this phase.
Much in development work remains experimental, but
the application of specialized experience in fishing boat
naval architecture and progressive use of the new com-
puting techniques will reduce the amount of experimenta-
tion.
The development of national or regional boat types
requires careful scrutiny of a wide field of influencing
factors, among which :
• Geography and hydrography of the area of
operation, including information on weather and
sea conditions, prevailing winds, situation and
adequacy of harbours and shelters
• The local fishing industry has to be studied in
view of the comparatively large investment value
represented by boats in the economic framework
of the industry
• A resources appraisal should be undertaken to
judge the economic feasibility of large scale
boatbuilding programmes in the framework of
fisheries development in general
[478]
• An assessment of the local boatbuilding potential
is essential
Information required extends to the potential capacity
of the yards, accepted construction methods, availability
of skilled, semi-skilled and unskilled labour, basic con-
struction materials (timber, metal and alloys, fastenings,
insulation material, paints and glues, electrical equipment)
as well as of generally imported equipment (engines,
deck machinery, electronic equipment) to obtain an
accurate picture of possible bottlenecks in supplies that
could seriously disrupt production of the yards.
Design development procedure
A specialized fishing boat naval architect with supporting
staff should be included in any group concerned with the
planned development of fisheries.
A government desiring to develop its inshore fishing
fleet in the framework of a national development plan
will find three main possibilities of obtaining the nec-
essary technical knowledge and assistance :
• Securing the services of a local naval architect
specialized in fishing boat, or at least small boat
design
• Engaging an expatriate naval architect either as
an expatriate officer or as a consultant
• Requesting expert assistance through the United
Nations Development Programme, or other
international, bi-latcral, or private aid machinery
From experience the iirst approach is rarely possible
in developing countries because of an acute shortage of
technically qualified personnel. The second is not often
resorted to by governments, while in past years many
boat designs and fleet development projects were actively
assisted by UN technical assistance personnel (table 1).
Apart from securing technically qualified personnel
for design development (and possibly to direct boat
construction programmes), any Fisheries Administration
called upon to undertake such activities will have to
create the technical services indispensable for their
success. The establishment of a specific Fishing Boat
Office would be a pre-requisite for success. Such an
office should group together technicians from the three
main fields of activity:
• Boat design
• Boatbuilding
• Marine engineering
The work programme of a Fishing Boat Office should
list:
Survey of existing boats
Determination of requirements for new boats
Preparation and distribution of designs
Construction supervision
Recommendation concerning marine engines, pro-
pellers, deck machinery and electronic equipment
Provision of free advice to private enterprise regard-
ing boats and equipment
Provision of information to the boatbuilding, and
equipment manufacturing industry regarding
development trends and future requirements
Staff training
Where necessary, training of outside personnel
Advice regarding legislation affecting boat develop-
ment, such as scantlings regulations, construction
standards, equipment rules, measurement rules,
registration, and loan and subsidy regulations.
The extent to which this long list of activities can be
implemented depends mainly on the availability of staff'.
In many cases it would be necessary to start very modestly
and to expand the scope of activities as general
fisheries development gains momentum. The important
thing is to refrain from formulating rigid, long-term work
programmes, but to organize the work according to the
needs of the fishing industry which should be based on
information supported by serious scientific investigations
at least in such cases where a new resource suddenly
creates large investment and production possibilities.
[479]
Arctic Fishing Vessels and their
Development
by Kjeld K. Rasmussen
Les bateaux de pgche arctique et leur developpement
Bref expose sur Involution des bateaux de peche groenlandais
d'une jauge brute inferieure £ 20 tonneaux, avec historiquc des
divers types de bailments, faisant ressortir le developpemcnt
rapide qui s'est manifesto depuis la Scconde Guerre mondiale. La
communication renferme des notes sur la stabilite, les precedes de
construction* les materiaux employes et la protection contre les
glaces.
II est permis de tirer des conclusions generates touchant un mode
efficace de ddveloppement visant a realiser des plans optimises des
points de vue de la technique et dc reconomie, dans des conditions
d'ordre administratif analogues a cellos de la situation etudiee, ou
la programmation, le dessin et la construction des bailments ont lieu
au Danemark, c'est-£-dire loin de la zone d'operations.
L'existence d'une "generation" dc bateaux normalises presente
un grand interet, et 1'auteur suggere unc methode mettant a profit
les caracteristiques des batiments de chaque g6n6ration pour
amdliorer la conception des futures unites. Pour faire de vgritables
prpgres, il est indispensable de disposer tant de donnees dignes de
foi sur les plans et les essais que de resultats de 1'observation du
rendement des bateaux en service. L'auteur propose de faire
remplir un questionnaire par les usagers, et conclut en 6numerant
les avantages que presente I'appui des pouvoirs publics.
Los barcos pesqueros del Artico y su desarrollo
Se presenta una breve resefia del desarrollo de las embarcaciones
pesqueras en Grocnlandia para barcos menores de 20 toneladas
brutas, acompafiada de una breve rescfta cronologica de los
distintos tipos, atendidndose principalmente al veloz desarrollo
aicanzado en el periodo de la segunda guerra mundial. Contiene
notas sobre estabilidad, construction, materiales y proteccidn
contra el hielo.
Deben formularse algunas conclusions generates en cuanto al
procedimiento para un desarrollo eficaz que tienda a idear t£cnica y
econ6micamente discftos 6ptimos en condiciones administrates
similares a las que se dan en esta circunstancia, en donde la planifica-
ci6n, disefto y construction se lleva a cabo en Dinamarca, cs decir
en un lugar alejado de la zona de operation.
Se exponen las ventajas de una generation de embarcaciones
normalizadas y se sugiere un metodo por el cual cada una de las
generaciones se utiliza para mejorar el disefto siguiente. Se explica
que no se puede llevar a cabo ningun progreso efectivo sin datos de
disefio y pcrfiles, por un lado, y de observaci6n del funcionamiento
de los barcos en servicio, por otro. Se propone que el personal que
los explota rellene un cuestionario. Por ultimo, se hacen constar
las ventajas de la ayuda oficial.
BOAT development is depicted as being de-
pendent on the combined effect of such factors
<as capital available for boatbuilding, develop-
ment in fishing techniques and the fisheries products
demanded. Greenland fisheries started with a very simple
combination of these factors but has developed into a
rather complex structure of boat types, fishing techniques
and shore installations.
BOAT DEVELOPMENT IN GREENLAND
First phase, pre-1945
The development from the beginning had strong govern-
mental guidance and support. Before World War II
only the Danish government owned and operated
mechanized, decked fishing boats below 20 GT. The local
fishing was from kayaks and dories in fjords and sheltered
areas. The government activity was in the form of ex-
ploratory fishing for cod, halibut, Greenland halibut
and shrimp. In this way a foundation was laid, knowledge
gained of fishing grounds and the structure of shore
installations developed, ready for the great expansion
of the post-war period.
Second phase, 1945 to 1952
Privately owned mechanized boats were introduced,
being initially 18 ft to 22 ft (5.5 to 6.7 m) open boats, but
gradually increased in size to 22 to 26 ft (6.7 to 8 m),
decked and partly decked. Salted cod played a pre-
dominant role, and the boats were primarily concerned in
providing inshore line fishermen with more seaworthy
boats, with some accommodation forward in the larger
vessels,
Methods of fishing were handlining and set nets. The
landings were delivered to numerous small salting
plants along the coast.
The boats were usually designed and built by yards in
Denmark. Some, however, were built in small boat yards
in Greenland or by the fishermen themselves. The tradi-
tional procedure where the hunter built his own kayak
had not completely disappeared.
Third phase, 1952 to 1962
The inshore cod fishery became more and more pros-
perous and the first filleting plants for frozen fish products
were put into operation. A standard handline cod
fishing vessel of 10 GT 30 ft (9.1 m) length was intro-
duced. It was designed by Mr. Slaaby Larsen, a Copen-
hagen naval architect. The boat was decked, had ample
accommodation forward, was fairly seaworthy, and
became very popular. The hull was slightly modified
over the years with a fuller deckline forward and aft,
with a rounded forefoot which was essential for hull
protection when hitting rocks, and later a raking stern
was introduced for better deck space aft.
During this period very profitable shrimp fishing
[480]
grounds were discovered in Disko Bay in North Green-
land, introducing an immediate demand for vessels for
shrimp trawling. Previously shrimp trawling had been
done exclusively by a few Government-owned 1 5 to 20
GT boats in Southern Greenland.
After 1958 an increasing number of boats of 17 to 24
GT was ordered by fishermen in Greenland encouraged
by subsidies, favourable loans and good prices for shrimp
landings. The boats were almost all of the normal
Danish fishing boat type with slight modifications in the
general and deck arrangements. All were side trawlers
with mechanically driven trawl winches and line haulers,
because these vessels were designed to fish cod and
catfish when not shrimp trawling. Some were also
fitted with harpoon guns for hunting small whales.
These boats were built with lines developed by each
building yard, with only general arrangement and speci-
fication being provided by the purchaser, the Royal
Greenland Trade Department (RGTD).
The good prices for shrimp made it possible for
private fishermen to afford the larger boats. Many were
of the opinion that these vessels were not used enough for
cod fishing, this being a less profitable employment even
when shrimping at times had to be restricted because
the processing plants could not handle the landings of all
the boats. The loans and subsidies were given without
conditions as far as landings were concerned, so the
fishermen could only be urged to fish for cod rather than
shrimps. The vessels were not provided with a longline
chute aft, but only with a line hauler amidships, so
normal longlining was not possible, cod being taken by
handlines and line gurdy or by set nets early in the
season.
Some vessels occasionally hunted small whales so the
pattern of fishing was mixed, and not altogether bene-
ficial for a constant delivery to the shore installations for
frozen fish products. With the extremely high cost of
harbour and quay construction and the expensive
freezing and filleting plants, it was a point of argument
whether each of the mainly state-owned factories should
have a number of fishing boats contracted to obtain
steady deliveries. The idea was postponed until larger
government-owned or controlled boats could be built, as
these would be better suited and more independent of
weather conditions during most of the year.
With the big demand for boats, built at many different
yards in Denmark, it soon became necessary to have
standard drawings for the larger boats to ensure uni-
formity and high standard of hull form and general
arrangement, also detailed technical specifications to
ease administration and inspection work, during con-
struction.
Fourth phase, 1962 and onwards
In 1962, therefore, standard drawings and detailed
specifications were compiled for a 16- and a 20-GT
vessel, the 10 GT type already standardized, the 16 GT
type designed by the RGTD technical staff and the
20 GT type by the author. Since 1962, these three boat
types have been produced with virtually no modification
except for variations in choice of main engine and small
changes in accommodation and deck arrangement.
The 20 GT design was to be fractionally below this gross
tonnage because for vessels above this figure the Danish
Ship Inspection requires that skippers should have
passed an appropriate navigation examination and that
the vessel passes periodical surveys of hull maintenance
and repair, equipment and engines. From the Danish
Fig 1. Loading a 20-GT standard vessel
[481]
Fig 2. 20-GT standard vessel lines plan
Main data for 20-G7 vessels
Boa
Lwl
L max on frames
D mould
Displacement in salt water to Lwl 42.45 ton
LCB
Cp
iae
at
0.26 ft (0.080 m) aft
0.581
34.5°
Inches
47 ft 5 in (14.45 m)
42 ft 0 in (12.80 m)
14 ft 9 in (4.50 m)
6ft 11 in (2.12m)
Scantlings for the 20-GT fishing vessel
Keel
Stem
Frames, double sawn
Frame spacing
Keelson
Side keelsons in engine room
Covering board
Inner covering board
Shelf
Clamp strake
Bilge stringers, 2 off
Inner planking
Garboard strake
Ordinary planking
Deck beams
Deck planking
official point of view this would have been advantageous loans and subsidies; owners, however, wanted their boats
as they had invested money in the vessels in the form of to be just below the regulation limit because, due to
[482]
oak
TixllJ
185x300
99
7ixl5i
315x390
»>
3|x4|to6i
95x110 to
155
99
18£
480
99
5?x6£
150x175
»»
5*x7i
130x185
»»
2
50
99
2x7^
50x200
99
2ix9*
55x235
99
I*x8i
45x210
99
2x7*
50x185
larch
If
35
oak or beech
2*
60
»» 99 99
2
50
below wl
oak
4|x4Jto5
120x105 to
130
pine
2
50
J. 20-GT standard vessel. General arrangement
[483]
Q2
Fig 5. J6-GT fishing craft
[485]
LOA • 44ft lOn (13.7m)
LWL • 40f! 8m (124m)
_ B/2*«f 110m (225m) .j
7
•' i • '••>' : 5
. ,,.... ,--n ..»-
1-.-U
I j - '
_ .. . .j
0 I 2
r«.-r — *.,- - ,. ., * (+.
02468
ct I - i
:
. 45-ft (23.7-m) vessel. Preliminary lines plan
previous laxity in the enforcement of the regulations,
some of the individually built boats, of even 23 to 24 GT,
had been measured down. Fig 1 shows the loading of a
20-GT vessel weighing about 40 tons. This was one of the
32-ft fishing boats shipped to Greenland in May 1965,
all in one big carrier. Of the 32 vessels, twelve were of the
10 GT type, ten of the 16 GT type and ten of the 20 GT
type. The smaller boats were placed in the hold and the
bigger on the deck. Fig 2 and 3 show the line plan and
general arrangement of this type of vessel. Fig 4 and 5
show the general arrangement of the 10 GT and 16 GT
types.
The following boats have been sent to Greenland during
the last few years:
1961
1962
1963
1964
1965
10 GT
5
25
10
10
15
16 GT
5
12
11
6
10
20 GT
4
10
5
6
10
Larger vessels
For years there has been discussion urging the construc-
tion of larger boats for cod fishing on the banks outside
Greenland waters in the Davis Strait, as the major fishery
nations were already taking big catches there with their
much larger vessels. With the partial disappearance of
cod from the inshore waters it was thought imperative to
build bigger vessels. A programme for such vessels spon-
sored by the Danish Government was launched in 1964.
It is not described here as it is considered outside the
scope of this paper which deals only with boats of up to
20 GT.
Further refinement of smaller types
A revision of the plans and the development of a second
generation of the three standard type vessels was post-
poned because a decline in the cod fisheries since 1963
gave rise to speculation as to whether the smaller
vessels were a good proposition. However, by the
beginning of 1965 when proposals for larger vessels were
submitted, new proposals for boats under 20 GT were
also included. These proposals were sent to Greenland
for comment by representatives of the fishermen, local
plant managers, loan board, etc. Only after receipt of
such comments will the detailed design work begin.
This procedure has already established a better and
closer contact between the planning administration in
Copenhagen and the fishermen in Greenland. Previously
the physical distance between the naval architect in
[486]
Fig 7. 45-ft (7J.7-/w) proposed vessel. General arrangement
;487]
LOA -- 3? ft OinL975m)
.LWL = 39ft Oin(886m)
Fig. ti. 32-ft (9.75-m) v^wr/. Preliminary lines plan
Copenhagen and the prospective boat owner in Green-
land has at times been too far.
Two types of vessels, a 45-ft (13.7-m) and a 32-ft
(9.75-m) vessel, are described below for the development
of smaller boat types for Greenland, being the author's
entry in the current discussion.
The proposed 45-ft (13.7-m) vessel is thought to
measure just under the 20-GT limit. The main emphasis
is placed on spacious accommodation for the crew of
four, and the introduction in Greenland of a working
deck aft. Although fishing trips with the vessel will
seldom exceed 24 hours, the crew must be comfortably
accommodated since often they will be away from their
home port for many weeks and have to live on board.
Fig 6 and 7 show the lines and general arrangement of
the proposed 45-ft vessel. The version shown is a shrimp
trawler, but an additional arrangement can be made for
longlining. Another possibility would be to operate the
vessel for seal hunting in the season, carrying kayaks on
the deck to and from the hunting grounds, and using the
vessel as a carrier of the catch.
By having the accommodation and the engine room
adjacent, the problem of heating can be solved by
placing the traditional small oil burner in the engine room,
installing a coil for water circulation and having radiators
placed in the accommodation and wheel house. Cooking
will be done on bottled gas burners. In the existing
standard types the oil burners have to be placed in the
accommodation itself where they often obstruct good
planning.
An engine of about 90 to 100 hp in the rpm range
of 1,500 to 1,800 and with 3:1 reduction is envisaged.
This is a departure from the traditional heavy duty
engines, and this solution is chosen to reduce initial cost
for the engine, for the sake of compactness and to
reduce displacement. This engine is estimated to give
a service speed of about 8 knots.
Main data for proposed 45-ft type
Loa 44 ft 10 in (13.7m)
Lwl 40 ft 8 in (12.40 m)
B max on planking 13 ft 8 in (4.50 m)
D 6 ft 8 in (2.05 m)
Displacement in salt water to Lwl 30.45 ton
LCB at „ 0.53 ft (0.1 63m) aft
Cp „ „ 0.575
K „ „ 29.5°
488]
I'ig 9. 3 2' ft (9,75-rn) proposed vessel. General arrangement
A 32-ft (9.75-m) launch is also thought to be adaptable
for various arrangements as to form and size of hold.
Fig 8 and 9 show proposed lines and general arrange-
ments. The main idea is to have a self-bailing working
deck aft, where the crew have good protection. The ver-
sion shown is a longliner with the hold in the form of a
box on the working deck, with any additional catch stored
in pounds. Accommodation for a crew of three is built
into the wheel house. The main engine would be in the
40 hp, 1,500 to 1,800 rpm range with 2:1 reduction,
which should give a service speed of about 7.5 knots.
Main data for proposed 32-ft type
Loa 32 ft 0 in (9.75 m)
Lwl (WL 3) 29 ft 0 in (8.86 m)
B max on planking 11 ft 4 in (3.46 m)
D 4 ft 7 in (1.40m)
Displacement in salt water to Lwl 8.025 ton
LCB at „ 0.1 4 ft (0.0425m) aft
Cp „ „ 0.590
K „ „ 28.0°
The two new types proposed would be constructed of
wood, preferably with keel, stem frames and beams of
laminated members, although heavy steam bent timbers
may prove the best solution as frames for the 32-ft
(9.75-m) type.
Special regard should be given to strengthening the
parts of the hull most exposed to impact from ice and
rocks, i.e. the foreship. By using laminated members and
[489
/''iff 10. Hydrostatic curves for the 20-GT standard vessel
lighter engines a reduction in the light displacement of
the vessels can be achieved, l-or both of the proposed
types ballast should be carried in the form of iron and
not in the form of costly boat-building timber, as
previously practised.
STABILITY
Since 1962, even before it became compulsory for all
Danish fishing vessels above 20 GT gross to have a proper
stability analysis made, with cross curves of stability
and an inclination test, all vessels sent to Greenland
that were approaching 20 GT or above were analysed.
The computer program developed at the Danish Ship-
-,0.3-r
,8- ;
Fig 11. Statical and dynamical stability curves for the 20-GT
standard vessel in light condition
building Research Institute was used to ensure uniformity
in results. Fig 10 and 11 show the result of such an
analysis.
CONSTRUCTION CHARACTERISTICS
The scantlings have been almost exclusively those given
in the official rules for Danish fishing vessels, and so the
vessels for Greenland have not been built heavier than
the equivalent Danish vessels. It should, of course, be
remembered that Danish scantlings are excessively
heavy, and experience has shown that they are certainly
not too light for use in Greenland. The typical relation
between length in the waterline and light displacement
is shown in fig 12.
In the opinion of the author they may even be reduced,
and possibly a corresponding reduction made in the
official Danish scantlings. Some smaller coastal vessels
of wood sent to Greenland about thirty years ago and
still in operation have, reportedly, much lighter scantlings
than equivalent modern vessels sent to Greenland.
Construction materials have been almost exclusively
white oak with the occasional use of beech for keels and
keelson and for part of the bottom planking. For the
small vessels pine and larch have been used for outside
planking. Decks have been of pine. In the very dry
climate, difficulties have been experienced in keeping the
deck seams tight but in the last few years good results
have been achieved by using rubber caulk in all deck
seams.
A «t~-
ton*
(metric)
50
SPARE PARTS
The storage of spare parts in Greenland for standardized
engines and equipment is well organized. Practically all
workshops and repair yards are government owned, and
they each have a store of spares so that the entire coast-
line is covered according to a central plan.
ICE PROTECTION
Hulls have to be well protected against chafing from ice.
Initially, sheets of galvanized iron were used, nailed to
the planking. Later, sheets of sea water-resistant alu-
minium proved a better solution because it was corrosion
that eroded the galvanized sheets, and not deterioration
due to ice chafing. A considerable area of the bottom is
sheeted because pieces of floating ice are dragged along
it. The sheets are nailed to planking starting from aft with
about 2 in (50 mm) overlap and thickness of 0.04 to
0.08 in (1 to 2 mm).
Ice protection by wood has not been used except 10
give 'the clinker vessels, sent to Greenland, a smooth
surface for securing the metal sheets. This partly accounts
for the very few clinker-built vessels dispatched to
Greenland. Various experimental attempts have been
made for the protection of propellers, but for the small
vessels described, the idea has been abandoned almost
completely because the protection was of such a form
that when the boats went astern bits of ice were virtually
packed around the propellers. There was also a consider-
able loss of speed. As practically all fishing vessels in
Greenland have controllable pitch propellers, damaged
blades can be easily replaced.
The stem is protected by heavy galvanized iron bars
above water, the stem and forefoot by a channel
construction below. This, combined with a well rounded
forefoot, gives added protection to the hull when hitting
rocks, which happens several times a year. A reasonable
rake of the stem gives better performance in ice conditions.
The factors above largely fix the whole shape of the
fore end and this may be considered contrary to what
Scale for LWL.
Fig 12. Curve of light displacement for standard vessels
[490]
some designers find is necessary for the shape of the
foreship where over-icing is to be prevented. Icing on
these vessels has not been experienced to a great degree,
however, because operations are reduced during winter,
length of trips are limited, and the shore always close at
hand.
HEATING AND INSULATION IN
ACCOMMODATION
Heating the accommodation is important. Normally,
small oil burners of the type used in Danish fishing
vessels are installed. Previously small coal heating/cook-
ing stoves were used. With the introduction of gas for
cooking and oil burners for heating, the existing coal
stores have often obstructed good accommodation
planning. Various methods, with hot-air circulation or
radiators with hot-water circulation from central
heating plant, have been tried, not so much in fishing
boats but in numerous government-owned special
purpose vessels. For cheapness and simplicity the small
oil burner has not been surpassed and, therefore, is still
used.
Living rooms are generally insulated between deck
beams and along the inner planking of the hull. Material
is mineral wool in thicknesses from 14 to 2 in (38 to
51 mm).
LOANS AND SUBSIDIES
Danish citizens permanently residing in Greenland may
obtain a loan and/or subsidy for the purchase of fishing
vessels under the following conditions: For vessels
measuring 10 GT and below, loans are given up to 85 per
cent of the total cost of the vessel delivered in Greenland,
to be paid back over 10 years at 4 per cent p.a. No
subsidy is given. For vessels above 10 GT a subsidy is
given up to 20 per cent of the total cost of the vessel and
loan for the difference between the subsidy and 90 per
cent of the total cost of the vessel delivered in Greenland.
Normally 20 per cent subsidy and 70 per cent loan is
given. Loans to be paid back over 1 5 years at 4 per cent
p.a.
CENTRALIZED PLANNING OF FISHING
BOAT DEVELOPMENT
The foregoing, apart from being a general report on the
development of fishing vessels in the vicinity of Green-
land, has been to provide the background for general
conclusions on the most efficient relations between the
fishermen and the development planning body when
separated by considerable distances; also on how the
most successful vessels may be produced at any particular
moment.
In this particular case, it must be borne in mind that
the centralized planning authority controls the organiza-
tion and administration of the development programme
for an entire area for a considerable period.
The following is developed from the author's ex-
perience in the particular field, as a department naval
architect and finally as a consultant, jn this and associated
fields.
The ideas proposed are not in practical use but the
general proposal is to reduce the physical and technical
distance between the fishermen and the controlling body
by the intermediate links of masterfisherman, gear
technologist, department naval architect and the con-
sultant.
THE DEPARTMENT NAVAL ARCHITECT
Such a person may have had an education in naval
architecture mostly founded on large ship design, and
his knowledge of fishing boat architecture must stem from
his own studies. It would be advantageous to all interested
parties if he could be posted to the operating area when
boat development is still at the initial stage of small boats,
which will enable him to follow the technological
development of the fisheries in that particular area and
apply his basic knowledge in design theory and con-
struction methods gradually as the requirements for
bigger and more complex vessels increase.
On the other hand he could come from boatbuilding,
having had some extra tuition in fishing boat architecture.
This combination will often prove to be a very good
solution and the only one possible in many cases.
Naturally any keen person with some engineering
education or a degree in science may also be given
additional education and prove to be a useful department
naval architect.
START OF BOAT DEVELOPMENT
It is rather obvious that the first proposals for boats, in a
developing area, must come from the planning personnel
and not from the fishermen, unless the local non-
mechanized lishing boats are easily mechanized and
improved so that they can be taken as a basis on which to
work. In this case the fishermen may be useful to some
extent. The idea of using local craft as a basis for boat
development is difficult, because while it may be assumed
that the modification of a local type is an initial step that
a fisherman will accept, in most cases it is difficult to
attempt to modify a local craft incorporating modern
design features of hull form, adequate accommodation
and cargo space and an effective fish deck arrangement.
On the contrary it has generally been proved that
fishermen do not mind relinquishing their local tradi-
tional types and accepting a modern functional and well
planned design, if such a boat will catch more fish and
increase his net income.
DEVELOPMENT UNDER WAV
Jt is assumed that boat development is well under way
and larger and more complex vessels are planned. So far
the department naval architect has been able to cope with
the design work alone, even with the gradually increasing
volume of correspondence, relevant and irrelevant,
specifications, etc. that are considered as part of his work.
A stage is reached when the situation requires more
help in handling the more complex boat designs, especially
if a standard design is to be developed where the extra
care needed will require more work.
491
The fact is that the department must be expanded
with a larger staff, that several boatyards are approached
or a consultant employed for specific work. If the depart-
ment is expanded, Parkinson's Law will most probably
come into effect and soon the staff will do design and
drawing work only occasionally, employing most of their
time in administration and consultations with equipment
manufacturers and boatbuilders.
If a boatyard, which has a design or will produce the
required design for a specific purpose, is approached,
the department is more or less dependent on that one
boatyard since one builder will not normally allow other
yards to construct his design. But given a boatyard with
sufficient capacity and the right prices, this arrangement
is definitely feasible.
Co-operation with a consulting naval architect,
however, will in many cases be the best arrangement from
the department's point of view. A consultant specializing
in fishing and related vessels has the latest research in this
field at hand, and is a good medium for contact with a
research institution where he can advise on tests to be
performed either by models or full scale. The con-
sultant is, moreover, only paid for actual work done and
he works to a specified time deadline that he must do his
utmost to maintain if he intends to stay in business.
The department naval architect, for his part, should
know the requirements of his department and have the
most direct contact possible with the fishermen, gear
technologists, fisheries biologists, loan board and
national ship inspection. He also understands the same
technical terminology as the consultant.
DECISIVE FACTORS IN DEVELOPMENT
It must be emphasized that factors, such as specific
fishing techniques for the area, availability of different
species of fish at certain seasons, distance to fishing
grounds, policy of loan and subsidy for procurement of
vessels and gear, naturally are all very decisive when
selecting the size and type of boat. Furthermore, decisive
factors valid when one type is planned may be completely
different only a few years later. Within one set of factors
there may have to be modifications in the light of per-
formances of vessels already in service.
REPORTS ON MODIFICATIONS
Reports on essential modifications should come from the
fishing grounds, the fishermen, those who maintain the
boats at the location, or management of shore installa-
tions, etc. Typical reports may be on a deficiency in
seaworthiness, speed, deck space, gear, hold space,
crew's accommodation, etc. These are the design factors
the naval architect should correct and incorporate when
planning what may be termed as the second generation
of boats. How does the department naval architect, in his
often distant headquarters, manage to obtain such
reports, in clear language, giving relevant concise
information with the application of a boat designer's
terminology ?
It is imperative to have as full information as possible
about the boat at the design and trial stage, such as
hydrostatic curves, cross curves of stability, results of
inclination tests, capacities of hold and fuel tanks, a hp
against speed curve for the full-sized ship, propeller
calculations, etc. Only with such essential background
material can there be any real hope of analysing and
interpreting the gathered information correctly. Such
material has until now only been available for much
larger vessels but, when many boats are to be built to one
standardized design, it is considered important to carry
out many more calculations for boats in the 20-GT range.
Reports should be collected as a combination of
design and trial data, on-the-spot observations by the
department naval architect or his staff and a systematical
collection of reliable data for the vessels in actual
operation.
When fishermen, who have only used primitive craft,
are beginning to acquire larger mechanized and decked
vessels, it takes some time before they can form an
articulate criticism in technical terms, so that an im-
proved second generation of standard boats can be
planned and designed. In fact, this even seems difficult
for many fishermen in highly developed fishing countries
but it is believed that fishermen can be educated and
encouraged to give the required information about the
behaviour of their boats. The completion of question-
naires with the aid of local fisheries officers, shore plant
managers, or the personnel from workshops and repair
yards is one solution.
The main scope of the questionnaires should be to
form a supplement as close as possible to the design
and trial data already at hand. The questions for the
smaller should be fewer and less comprehensive than for
the larger types, and then again the degree to which
information is collected should not be higher than
justified by the amount of design data available or its
eventual use.
The main object must be to work systematically and
apply a step-by-step development in the technique of
gathering and using the collected information.
STANDARDIZATION
Standardization means the construction of a number of
boats from the same set of drawings. One may have a
different size of engine and a different arrangement on
deck and still call it a standard boat. The advantages of
producing a number of boats from one design are many.
Primarily, it is economically possible to carry out more
detailed calculations ensuring a better design, to carry
out model testing, stability investigations, etc., than
when a design for only one or two boats is made. More
detailed drawings can also be done and this ensures a
better end product.
Construction costs for standardized vessels may be
higher or lower, depending on whether a few yards are
building many vessels in succession or smaller yards are
building only one or two. These costs may be reduced,
however, even if built in smaller yards. One way is
prefabrication of sectional elements by gluing and
assembling these elements at a central laminating plant.
This method assures a uniform good quality of all the
important construction members and, by pressure
[492]
treating the wood laminates prior to gluing, a very
effective protection is achieved against fungi attack.
Standardization also facilitates inspection work during
construction. In collecting data for planning the next
generation of boats it is also probable that more reliable
information will be obtained with many owners operating
the same type of boats.
Standardization of hull construction has, of course,
reached only an intermediate stage. Engine make and
preferably engine size, gear and equipment should be
standardized as much as possible, and a stock of spare
parts and replacement parts should be maintained at key
points in the operational area. An untold number of
valuable fishing hours have been lost because spares
were not available at reasonable distances from the
landing places.
For the type of fishery development dealt with here
it is only natural that the stocks of spares are financed by
the government and stored in association with govern-
mental workshops. If the maintenance yards and work-
shops are privately owned it could hardly be expected
that they should maintain stocks of the rather extensive
range of spares necessary if the arrangement is to be
efficient.
Standardization does not mean that such a design
can be built until it is forced to be changed by the
overwhelming demands from fishermen, or their repre-
sentatives, to produce something superior. The correct
procedure must be, as soon as one design is launched,
to start immediately preparing the possible changes so
that the next generation design can improve on it; after a
reasonable period of time, when the amount of
systematically collected data has reached the appropriate
level for reliable decisions to be taken, the revised
design should be finalized. The proposals for such second
generations of boats should include various alternatives.
An excellent idea would be to construct perspective
sketches drawn with the proposals viewed from various
angles. This will demonstrate more clearly the appearance
of the boat for those who are not used to considering
normal projection design plans.
All the material prepared should be submitted to the
operational area for comment and suggestions by fisher-
men or their representatives. All administrative organiza-
tions who are involved in the approval of the design, such
as loan board, ship inspection, insurance companies,
should also have the plans. Only after having taken all
the proposed alterations into consideration should the
actual detail design work start.
Where development of fishing is done with govern-
mental support, approximately as outlined above, the
technical achievements obtained in the process should
not be retained as the secrets of the particular govern-
ment depaitments but should be made available for the
benefit of the private sector of fishing boat development.
Such material should include reports on experiments
with improved and more modern building materials, new
techniques in construction and should add material to
the current debate on improved stability, seakindliness
and economical operation.
Acknowledgment
The Royal Greenland Trade Department kindly cooperated in the
preparation of this paper by permitting the publication of standard
drawings for 10-GT and 16-GT vessels.
[493]
The Advantages and Uses of
High-speed Fishing Craft
by John Brandlmayr
A vantages et utilisations des bateaux de pfehe rapides
L'auteur examine les batiments de pcche a grande vitcssc d'une
longueur comprise entre 30 pieds (9,15 m) et 40 pieds (12,20 m), et
fournit des donnees reposant sur une 6tude de la pechc aux filets
maillants dans le Pacifiquc Nord-Ouest couvrant la periode
1955-1965,
Les batiments de cc type, d'une vitesse maximale de 10 a 20
milles a I'heure (alors que les anciens bateaux ne depassent pas 8
milles a I'heure) sont assez prises, bicn que le gros de la flottille du
Pacifique Nord-Ouest appartienne a la categoric des bateaux plus
lents. On estime qu'un fond en "V" relativement 6troit est celui qui
convicnt le mieux. Parmi Jes mat6riaux de construction adoptes
figure le contre-plaque rcvctu de polyester renforce de fibres de
vcrre, les alliages d'aluminium, ou le plastique renforce moulc d'un
seul tenant. Les batiments rapides construits en bois selon le
schema classiquc (membrures, lisscs ct borde) ou en acier sont dans
Pensemble trop lourds pour les fins recherchecs. La plupart des
bateaux a grande vitesse sont 6quipes de motcurs a essence, les
diesels n'ayant eu qu'un succcs limite.
Le principal avantagc des batiments rapides semble resider dans
le fait qu'ils permettent de raccourcir d'un tiers la duree des sorties
tout en consommant & peu pres la meme quantity de carburant.
Ventajas y aplicaciones de los pesqueros r&pidos
Se estudian pesqueros rtpidos con esloras de 30 a 40 pies (9 a 12
metres). La informaci6n presentada se basa en la experiencia
adquirida con la pesca de enmalle en cl Pacifico noroccidental entre
losafios 1955 y 1965.
Barcos de estc tipo, con velocidades mdximas de 10 a 20 nudos,
gozan de cierto favor frente a otros mas antiguos que no pasan de
unos 8 nudos, aunque casi toda la flota del Pacifico noroccidental
es de embarcacioncs mas lentas. Los materiales dc construcci6n
admitidos son la plancha de contrachapado con rcvestimiento dc
pollster reforzado con fibra de vidrio, aleaciones de aluminio o
flora de vidrio moldeada, entcriza. Los barcos rapidos construidos
por el procedimiento ordinario de planchas y cuadernas, o con
acero, rcsultan gencralmente demasiado pesados para estos fines.
La mayoria de los barcos rapidos lie van motor dc gasolina, y los
diesel dan resultados Hmitados.
Las principals ventajas de los barcos rdpidos parecen consistir en
que hacen una singladura en las dos terceras partes del tiempo
empleado por los tipos normales mas antiguos, mientras que en la
misma distancia recorrida consumen, aproximadamente, igual
cantidad de combustible.
HIGH-SPEED fishing vessels of 30 ft (9.14 m) to
40 ft (12.19 m) in length have become well
established in the gillnet fisheries of Oregon,
Washington, British Columbia, and Alaska.
A number of different designers and builders have
been involved with this class of vessel but the author
will deal primarily with one basic hull form. This
particular form appears to be well adapted to speeds
from 10 to 20 knots and to be reasonably effective even
below 12 knots.
It is estimated that about 1,000 gillnettcrs of this
general type and speed are in service in 1965. A few more
highly powered, faster vessels have been built but since
no repetitive pattern of building them has been estab-
lished their construction is considered exploratory.
ADVANTAGES
High vessel speeds arc of greatest advantage in locations
where man-hour costs are high and where fishing is open
for short periods of time as in the North-American
Pacific Coast gillnet fishery.
Speed must be related to the value placed on the
fisherman's time and on the amortization of investment
in vessel and gear. The fact that there is a general but
very gradual increase in speed of fishing craft throughout
the world indicates the obvious desirability of speed. On
most fishing grounds there are now a few small vessels in
operation designed to operate at speeds 50 to 100 per
cent higher than their conventional counterparts. Cur-
rently the economics are against such craft in all but a
few applications. With rising values of labour and
improvement in boats it seems certain that before many
years extra high-speed craft will become increasingly
important. Possibly the hull type described in this paper
may be used for a significant part of the world's fishing
fleet under 50 ft in length and applications may even be
found for larger similar hulls.
Planing hulls have long been in common use for
yachts, military and some commercial craft. Limited
knowledge and poor control of construction has plagued
the development of planing hulls so that actual per-
formance is often far short of that anticipated. This
difficulty is most pronounced in the case of relatively
heavy vessels with marginal power. Fishing vessel
adaptations invariably fall into this category. The
problem is aggravated by the fact that builders and
operators do not realize the importance of weight nor of
efficient propulsion and designers tend to calculate for
ideal conditions.
HULL FORM AND POWER
To achieve a high speed in the light condition it is
necessary to build a hull of suitable form and power
and to keep the operational weight to a considerably
lower value than permissible with conventional craft.
The vessels must still be able to carry a load of fish
;494]
4» ; .
7. TV/y/oi/ lines of a 36-ft (11-m) gillnetter
nearly equal to conventional craft and to return home
at a lower but still economical speed with this load of
fish. The speed when fully loaded may be about the
same as for a conventional vessel. A planing hull can
only offer substantially higher speeds when carrying no
load or a light load. In the case of Pacific Coast gill-
netters it is important to reach the fishing grounds
quickly and to move at high speed with a light load. A
full load is rarely carried.
A final primary requirement is that the vessels must
be seaworthy in light and loaded conditions although
speed would be reduced to suit the weather conditions.
A typical hull form is illustrated by the 36-ft (10.97-m)
gillnetter (fig 1). This general form and proportion has
been used since 1959 and compares favourably in
service with others on the basis of low resistance through
the 10 to 20 knot speed range, sea-kindliness and sea-
worthiness. The form was based on previous gillnetter
hulls first built in 1955 and is similar to that used for low-
powered planing pleasure boats.
Length overall
Length designed waterline .
Beam overall .
Beam at waterline .
Volume of displacement at
waterline
Displacement at waterline .
Longitudinal centre of
buoyancy .
Loa
Lwl
B
Bwl
V
A
36 ft 0 in
32 ft 8 in
1 1 ft 0 in
9 ft 4i in
(10.97 m)
(9.96 m)
(3.35 m)
(2.86 m)
197ft3 (5.58m3)
5.6 ton salt water
FB 56.5% Lwl
This particular form is well regarded by most fisher-
men who have had experience with it. They feel that
fish-carrying capacity is adequate and have found con-
struction costs about the same as for slower conventional
craft.
The form is characterized by fine forward sections to
minimize pounding and flat after sections for most
efficient planing with a comparatively heavy planing
hull and limited power. This hull is narrower than most
planing forms since it is designed for a wide speed
range that might be considered at the bottom of the
planing range and down into the upper part of the dis-
placement range.
Alton (1959), Ashton (1949), Clement and Blount
(1963), Lord (1963), Murray (1950), Saunders (1957)
and Savitsky (1964) have presented important model test
data which were studied by the author and his design
associates and which have assisted in gaining an under-
standing of planing hulls. The form shown did not
originate directly from this data but evolved from a
process of selection by user preference.
It is probable that slightly more rise of floor aft and
slightly fuller sections forward would produce a better
hull. The author's firm has been developing data for a
standard series of hulls expressed in dimensionless units
with corresponding performance values for a wide range
of sizes and displacement conditions. It is hoped that
quick performance predictions can thereby be made
with a higher degree of reliability than is at present
available.
PERFORMANCE DATA
Performance data under service conditions have been
gathered for the published hull form and expressed in a
speed, power and weight diagram. In all cases a single
engine turned a propeller set in a wood or metal skeg,
with the stern bearing supported by a strut and with a
shoe extending from the skeg to the bottom of the rudder.
Reported and observed performance varied by plus or
minus 20 per cent. This great variation is chiefly attri-
buted to the considerable effect of variations in all the
factors that influence performance and is partly due to
the inexact method of gathering operational information.
Power available
20,000
izpoo
70 140 210
Power • B H P
280
fig. 2 Mean performance record of
a group of 36-ft gillnetters
BMP
The most reliable figure is the top speed at full power
in the light condition. The remaining portions of the
curves are very approximate but serve to illustrate the
character of this form and propulsion system under
various load (displacement) conditions. Fig 2 illustrates
the mean of available performance records. The mean
performance has been checked against data from other
published sources and correlation has been found within
12 per cent.
Using the 5.36 tons (12,000 Ib) curve which represents
the light condition the speed power curve rises in typical
fashion up to 11.6 knots at 140 hp. At this point the
dynamic lift of the hull is very pronounced but the spray
rail clears the water from the topsides, although the
water closes back on to the topsides for the after 3 ft
(0.91 m). The transom breaks clear along the bottom.
The slope of the speed power curve is reduced in this
area and above this speed is typical of planing hull
forms. At 280 hp the curve rises to 1 8 knots.
With increasing weight on board, the transition from
displacement to planing characteristics occurs at higher
power outputs until at 7.15 to 8.05 tons (16,000 to
18,000 Ib) the transition is barely discernible.
Running trim aft throughout the speed range is about
14° to 2° relative to static trim and is at its maximum
just before the spray rails clear. None of the hulls were
observed with more than 3^° of trim at this speed and
all tended to flatten out again at higher speeds.
The curves are based on the following figures:
A ions (Ib)
5.36 (12,000)
6.24 (14,000)
7.14 (16,000)
8.04 (18,000)
8.93 (20,000)
tons (Ib)
5.36 (12,000)
6.24 (14,000)
7.14 (16,000)
8.04 (18,000)
8.93 (20,000)
70/7/7
8.0 knots
7.2 „
6.5 „
5.9 „
5.5 „
210 hp
15.2 knots
13.9 „
12.2 „
11.0 „
10.3 „
11.6 knots
10.4 „
9.4 „
8.7 „
8.3 „
280 hp
18.0 knots
16.9 „
15.5 „
13.3 „
11.9 „
Of course with a propeller designed for best light load
performance the available engine power gradually falls
off when the hull is more heavily loaded and top speeds
are lower.
During trials of these hulls it was the author's impres-
sion that a considerable increase in speed occurred for a
small increase in power once the spray rails started to
clear the water from the topsides, but not as pronounced
as anticipated.
The spray rail shown in fig 1 and in fig 3 is not satis-
factory. A good rail should act as a wave deflector and
should extend from about 1.5 ft (0.46 m) aft of station 0
to 1.5 ft (0.46 m) aft of station 9 and its lower surface
should be 2 in (50.80 mm) wide and horizontal and
[496]
should be in line with the chine. A sharp reverse in the
spray rail will break spray into a fine wet mist. Omission
of a spray rail will allow the bow wave to flow up the
topsides and greatly increase resistance, thereby reducing
speed.
Fig 3. Plywood gillnetter
Leonard Alton, owner and skipper, reported in 1959,
on approximately the following lines, the comments of a
skipper on the boats under consideration :
• They were built primarily for speed and this will
be of great interest to other fishermen. A run from
Nanaimo to the Fraser lightship was timed on a
calm day with all fishing equipment on board and
fuel tanks half full and the average cruising speed
was 15.1 knots. The vessel was powered by a
converted car engine rated at 380 hp for car use.
Converted for marine use with a 2.5 : 1 trans-
mission, it produced about 300 hp. The engine
was run at 3,100 rpm, but when increased to the
full 4,400 rpm the boat would plane at 20 knots.
Propeller was 23 in (585 mm) diam and 20 in
(508 mm) pitch
• For high speed the displacement must be small
and, with more than 70-80 salmon aboard, the
boats perform as a normal displacement type gill-
netter but had carried 3,700 Ib (1,678.3 kg) at 10
knots
• It was a good sea-boat in the west-coast fishery
conditions, having a shorter period of roll, and
the lower beam probably accounts for the fact
that, although 99 per cent of the San Juan gillnet
fleet use stabilizers, they were unnecessary for this
vessel
• At planing speeds in heavy seas there was some
pounding but this only happened in short choppy
waves. At higher powers this was eased and in a
long swell the vessel ran smoothly
• The higher speed shortens the voyage time and
it is possible to overcome strong tides instead of
waiting
• The wide beam also provides ample room not
only around the net and in the afterwell, which
makes for easy handling and accessibility to the
catch, but for good net and steering layout
CONSTRUCTION METHODS
Wooden
While some well-built conventional frame and plank
wooden vessels operate at the speeds in question, it is
the author's opinion that more sophisticated materials
and methods of construction arc required. Standards of
high strength and light weight are so severe that ship-
yards accustomed to conventional craft can rarely meet
them until they have built several boats. The initial
>AWN FMAML
FLOO*%» I '•' YELLOW
Fig 4. Typical section for ply woodlfibreglass construction
[497]
results are either too heavy, in which case performance
suffers greatly, or the structure fails to withstand the
stresses imposed.
Composite plywood and fibreglass
Carefully built craft designed with light wooden web
frames and closely spaced longitudinal stringers planked
with full-length marine plywood and sheathed with
fibreglass provide a high strength to weight ratio as
well as the ability to resist abrasion and other service
deterioration. Using these materials boats can be
economically built either individually or in small num-
bers. A typical structure of this type is shown in fig 4 and
fig 5. It represents the lightest construction found to be
Fig 5. Plywood hull under construction
reasonably serviceable and most 32-ft (9.75-m) to 40-ft
(12.19-m) hulls have a slightly heavier structure particu-
larly with respect to the transverse and longitudinal
framing.
With regard to durability of this comparatively recent
method of construction, we have personal knowledge of a
gillnetter in use for over ten years. Her owner recently
reported that, although she had been used continuously,
the boat was still in apparently very good condition and
that the bilges were dry. This particular boat is illustrated
by fig 6.
Moulded fibreglass
Moulded solid fibreglass shows great promise when the
design and fabrication is competently handled. Quantity
production is essential for reasonable building costs and
about 20 vessels should be the minimum quantity.
Design and construction techniques have been well
developed and published but there has been a tendency
to underestimate the skills required.
Fig 7. An American aluminium alloy gillnetter
Aluminium
Aluminium alloys are the logical answer for a high
strength to weight ratio. Again skilled handling of the
design and construction is essential as is quantity pro-
duction. Fig 7 and fig 8 show a welded aluminium gill-
netter built by Marine Construction & Design Co.,
Seattle. Costs of construction and minor problems in
maintenance have interrupted continuous building in the
North-west Pacific. More experience with this material
should lead to its increased use. It should certainly be
considered by any group able to undertake a long-term
programme of development and construction.
Fig 6. A 34-ft plywood gillnetter built in 1955 and still in use
Fig 8. Two American aluminium alloy gillnetters
Steel
Steel is not suitable for construction of this class of
small high-speed craft, except possibly in some of the
best equipped shipyards working with high-strength
alloys. The few vessels built in steel have been too heavy
and, in general, shipyards have been unable to adjust to
the strength to weight standards required nor to follow
designers specifications. Costs of very light steel work
have also been higher than for other materials.
POWER CHOICE
Light, high-speed gasoline engines are the normal power
choice. A typical power plant is a single engine of about
425 in3 (0.007 m3) piston displacement producing 280
hp at 4,000 rpm and equipped with a 2.5 to 1 reduction
[498]
gear. This unit weighs approximately .446 tons (454
kg). Some fishermen are very careful in the tuning and
maintenance of their engines and these men are best
able to utilize the performance potential of fast boats.
A few installations of high-speed diesels have been
satisfactory but due to excessive weight and lack of
power, diesels, on the whole, have been unsuccessful.
It is felt that with the further development of hull
forms and light structures fast diesel powered craft will
gradually find a place. If the builders can meet the
designer's specifications, a new boat designed by the
author's firm should provide a practical fast diesel gill-
netter. However, its initial cost will be somewhat higher
than other types. It is possible that the overall economics
of operation will be better than for either the fast gasoline
engine-powered boats or the slow diesel-powered boats.
ECONOMICS
The author does not feel qualified to discuss the opera-
tional economics of this type of fishing vessel or to com-
pare it with others. In fact the income and cost figures
are so vague and clouded by fishing limitations, regula-
tions and other factors that an economic study using
hypothetical examples is probably all that can be
accomplished. The authenticity of figures used for such
a study is questionable.
Some of the most aggressive and capable gill net
fishermen own the fast gillnettcrs and a statistical com-
parison could easily demonstrate greater earning
capacity. Possibly credit for this goes to the men to a
greater degree than to the boats.
Some comparisons can be made. Except for attempts
to produce fast diesel-powered boats the first costs are
about the same for good well-equipped gasoline engine-
powered planing units and equivalent displacement gill-
netters with the same gasoline engines or less powerful
diesels. Carrying capacity is not important and the
maximum is practically never used. Displacement types
have greater carrying capacity but this is no advantage
under current conditions.
The chief difference is that the modern displacement
gillnctter cruises at 8 knots while the planing counterpart
does 12 knots. There are claims of equal hourly fuel
consumption rates. A more conservative and frequently
demonstrated situation finds both types using about the
same quantity of fuel over a given distance but the
passage time is in the ratio of 3 to 2.
499]
Fishing with the aid of an outboard on Lake Maracaibo, Venezuela
[500]
: Design of small boats
IMPROVEMENTS OF CANOES
Stoneman (Uganda): In Uganda where fishing takes place on
13,000 square miles of fresh water, lakes, rivers and swamps,
of the 6,000 fishing craft in use, 40 per cent are still dugout
canoes. A programme of replacement by more modern types
of craft is being carried out, but due to the long life of some
dugouts, the relatively high cost of replacements and the
restricted building capacity for improved boats in Uganda,
the dugouts will be in use for many years to come. Dugout
canoes are still being made for some uses and are still pre-
ferred by some fishermen to more advanced craft.
In Uganda dugouts arc normally single hollowed logs of
hardwood, many species being utilized, though palm tree
logs (highly unsuitable in many ways) may be used if nothing
Fig /. Typical dugouts on River Nile
else is available. On sheltered rivers, small lakes and swamps,
small canoes up to 20 ft (6 m) long with 18 in (.45 m) beam
and 1 ft (.3 m) depth are used, often very roughly finished,
although this type is highly developed on the Albert Nile
River, fig 1. Here the fishermen may live in their canoes for
days at a time, the craft having a clay fire hearth amidships,
papyrus mat resting on the gunwhales for shelter at night,
and forked-stick outriggers to carry poles, paddles, hippo-
potamus and crocodile spears and so forth. These canoes too
are exceptionally long-lived, many still in good condition
having been passed down from father to son until the age
(certainly over 50 years) has been forgotten. On the open
lakes, Albert, Kioga and Victoria, much larger canoes are
employed. These may be up to 40ft (12m) long with 3 ft
(0.9 m) beam. Skilfully handled, they can be used in rough
water carrying up to 1 ton of nets, gear, fish etc. At one time
it was common for such canoes to make 150-mile coasting
voyages, crossing 20-mile stretches of open lake under
paddles or poles. The longest dugout recorded from Uganda
was 70 ft (21.3 m) long and had a beam of 4.5 ft (1.4 m). This
exceptional canoe was used as a ferry. Such canoes are not
seen nowadays and the trees for their construction are no
longer available.
Method of making and cost
Many species of timber, depending on the availability are
used. Suitable trees, at one time free to canoe builders, arc
now hard to find, a royalty of £5 ($14) per tree is payable in
most instances to the Forest Department. Professional three-
man teams of diggers with specialized hand-forged tools
select and fell a tree and trim it roughly to the shape then
and there, while the timbci is still wet. It must then be trans-
ported to the lake side, as final trimming and hollowing out
Fig 2. Final hollowing out of 30 ft dugout beside Lake Albert
relies on floating the unfinished canoe at intervals to determine
the balance and stability. This three-man team will complete
a 30 ft (9 m) canoe in five to six weeks; the prospective owner
supplying them with food during this time (fig 2). When
complete, the side of the canoe will be under 1 in (2.5 cm)
thick and show considerable tumble-home as they follow
the curve of the original log. The bottom and ends are 2 in
(5 cm) thick, the end grain of the ends often splitting and
falling out even before the canoe is finished. This requires
repair work before it can be put into use. Most dugouts have
blunt "swim-head" bows and stern, but on Lake Victoria
roughly-shaped stems and canoe type sterns are carved out
of the solid. Here too the canoe may be widened by wedging
apart the gunwhales when the timber is still green.
A small 20 ft (6 m) canoe in a remote area may be as
cheap as £20 ($56), a price which has not changed for 30
years. The large 40 ft (12 m) type at a busy and, by Uganda
standards, efficient landing will still cost only £60 ($170).
These prices would be grossly uneconomic to the builder if
[501]
he attempted to cost his labour etc. on commercial lines, but
like many other primary costs in Uganda depend on the
factor of "nil opportunity cost" where the producer's time
and effort would not otherwise be utilized at all. While
acceptable in the undeveloped Ugandan economy, this type
of production makes it very difficult for other boatbuilders,
working on commercial lines with salaried employees, to
compete in price.
Despite its primitive appearance and connotation, the
dugout as used in Uganda has certain definite advantages.
First, cost is low and the life is long, 20 years at the minimum.
Maintenance can be and often is nil and the craft is almost
unbreakable. Even if swamped and capsized in surf the canoe
can be left to wash ashore and recovered undamaged at
leisure. The draught is small, rarely more than 6 in (0.15 m)
and the long, smooth gunwhales and hull, free of projections
of any kind, are ideal for the easy handling of gill and seine
nets. It can easily be beached, being rolled up on shore like
a log by two or three men. Against this, of course, the dugout
is extremely slow and inherently unstable, it demands skilled
handling even in calm water, and is most uncomfortable for
the occupants. The hull shape ensures that bilge water, gear,
fish and passengers all try to occupy the same space. Space
inside the hull is so limited that only the minimum amount of
attention to the gear or the catch can be carried out afloat.
The instability is perhaps the greatest single disadvantage
and leads to considerable loss of life annually on Ugandan
lakes through swampings and capsizings.
produce annually more than 35,000 tons of fish. With the
exception of Lake Tanganyika, it is largely a gillnet fishery in
shallow water. Craft used are the traditional dugout canoes
which in some fisheries, e.g. Lake Mweru, are quite seaworthy.
These craft are very variable in dimensions and in their
Fig 4. Typical lake canoes in Zambia
standard of construction; but generally are about 17 ft (5.2 m)
long, 2 ft (.61 m) wide and 17 in (.43 m) deep. A selection of
dugout canoes are illustrated in fig 4, There is some unspon-
sored development beyond the dugout on Lake Tanganyika,
where 18ft (5.6m) flat-bottomed fishing boats and 30 ft
(9.15m) flat-bottomed transport boats are made locally.
Fig 3. Large dugout converted to out hoard power on Lake Albert
It is difficult to visualize much improvement to the basic
dugout canoe. If a better type of craft is required, the fisher-
man turns to one of the modern, open, plank-built fishing
craft widely used in Uganda. Minor changes to the dugout,
such as floor boards, thwarts and so forth at once detract
from its basic and major advantage of simplicity and lack of
maintenance. Some few larger dugouts have been powered
with low hp outboard motors with slight success, fig 3* but
generally, once a fisherman has decided to get away from the
simple dugout he turns to one of the more advanced boats
straight away.
Zambia's lake canoes
Heath (Zambia): Zambia although situated in the middle of
Africa has large lakes, rivers, flood plains and swamps that
These craft show Arab influence and a feature of them is the
naturally-grown frames and knees cut from tree branches
crudely fashioned and fastened with wire nails — they are
unpainted yet reputedly last up to 1 5 years. On Lake Mweru,
"Chombos" up to 50ft (15.25m) in length were built and
operated by Greeks.
The demand for dugout canoes over the years, coincident
with the increased development of the fisheries, has resulted
in suitable trees becoming harder and harder to obtain;
the Mweru fishermen at one time were hauling dugouts 40
miles (63 km) to the Lake.
In 1954 a boatbuilding school was set up on Lake Mweru
under a Master Boatbuilder with the object of designing a
suitable craft to replace the dugout, which could be made by
locally-trained boatbuilders from local plank timber.
[502
Fig 5. 23 ft (7 w) banana boat in Zambia
CIFNCHF.D COPPIR NAILS
CLLNLMED fOPPCR NAILS.
TWO UETWEEN EACH TIMBER ithiN
COPPER NAl
XB« CLENCHED KEEL TO HOG
AT'JIN CENTRES
SPACING 9LOCKS
3INX3)NX^IN / M0(* 5iNX
FLANKING Vfc IN HARDWOOD
VflN SOFTWOOD
LTS 4 INK* IN
BOLTS 5lNX'/4IN MUSHROOM HEAD
KING PLANK 3m x UN
RISERS JIN XI IN FASTENED 2*1 IN I2^C/S SCREWS
THWARTS 12 IN X IN
RUiBINC STPAKt 2»*XI IN SCREWED AT TIMItM*
3INXl2^ C/S
4 SPACED IQIN CENTRE*
FORE AND AFT KNEES 2 IN SIDED
Fig 6. Construction drawing of Zambia banana boat
PLAN
Fig 7. Lines drawing of Zambia banana boat
[503]
In considering a suitable design as replacement for the
dugout the following factors had to be taken into account:
• The craft must be paddled; rowing had been tried
and was not accepted by fishermen and was of no
use in narrow swamp channels
• Craft must be such that an outboard could be used if
required
• Craft must be a good "sea boat" at the same time
manageable in narrow shallow swamp channels
• Craft must be simple in design, made from local
plank timber and constructed by locally-trained
craftsmen
• Craft must be serviceable without excessive main-
tenance
• Craft must take fisherman and up to three or four
crew and nets
To satisfy these requirements, the West-Ireland Curragh
appeared to have the greatest possibilities. This craft, built
traditionally as a wooden frame covered with heavy canvas,
is very seaworthy. Experimental craft were built of similar
shape, but planked both carvel and clinker, with different
amounts of fore and aft rocker and slightly varying dead rise.
Dimensions of 23 ft x 4 ft 5 in x 1 ft 10 in (7 x 1.35 x .56m)
moulded depth were chosen finally. Demonstration trips with
outboard powered craft to all fishing camps along Lake
Mweru were made, a favourable response being shown
immediately by orders. So was born the plank canoe, or as it
is commonly known in Zambia the "banana boat" so nick-
named because of the banana-like shape, fig 5.
Fig 9. 23 ft (7m) banana boat completed
Suitable locally-available timbers are — mulombwa (Ptero-
carpus angolensis) for planking and general construction—
mupapa (Afzelia quanzensis) timbers (steamed ribs). These
timbers are hardwoods and first-class boatbuilding timbers—
the latter lending itself to steaming. With one boatbuildcr and
two helpers/learners, a craft can be planked in six days and be
completed in three weeks. With regular maintenance and
Fig 8. 23ft (7 m) banana boat lifted off mould/ jig and
ribs steamed in
The lines and construction plans of the round-bilged canoe
are illustrated in fig 6 and 7. No machine tools are used in
construction. All plank joints are scarfed and scarfs staggered,
wedges are fitted under timbers in way of garboards, with
space left to form limber holes. All edges of timber are
chamfered or rounded to save snagging nets. The hull is
built upside down on moulds permanently fixed to the floor
or jig. When planked the hull is then lifted off, turned over
and the ribs are then steamed and bent in place. Fig 8, 9 and
10 give a good impression of the construction and set-up.
[504
Fig JO, Canoe constructed at Lake Kariba fisheries training
centre
painting a prototype has lasted ten years and it can be
expected to have a useful life for double this period.
Operating factors
Canoes used for fishing with 3 to 4 crew, carrying nets and
up to 500 Ib (230 kg) weight of fish, have a speed of 10 knots
with a 9.5 hp outboard and almost 7 knots with a 5 hp out-
rig 1L 23 ft (7 m) banana boat under load test with J2 men
board. Up to 1,500 Ib (680 kg) can be carried if the craft is
used for transporting goods, e.g. bundles of dried fish. Fig 1 1
is an illustration of a canoe with a load of 12 passengers.
Even allowing 120lb (55kg) per man the load is l,4401b
(650 kg) for a canoe weighing only 400 Ib (180 kg).
Although the round-bilge plank canoe has been in opera-
tion on Lake Mweru for a number of years, a few with out-
boards, details of their costs and earnings as fishing craft
have not been obtainable. However, the operations of crews
under and after training at the Fisheries Training Centre at
Sinazongwe on Lake Kariba, have been recorded in recent
times. From the data obtained over periods of 5 to 32 months'
fishing, average net profits have been of the order of £16
($45) per month, with units comprising a round-hilged canoe,
outboard of 3.9 to 5.5 hp, 25 nylon gillne's of 50 yards
(45.7 m), a fisherman and two crew. Of the total earnings of
the unit, 21.7 per cent was spent on petrol and oil, 22.7 per
cent on wages (including a wage for the owner), other
expenses 2.6 per cent, thus giving a profit of 53 per cent.
The catches of fish on Lake Kariba were not exceptional
being of the order of 20 Ib (9 kg) per 100 yards (91 m) of net.
Higher catches could give better profits. The capital costs of
a round-bilge canoe unit (boat, 5.5 hp engine and 25 nets) is
about £300 ($840) in Zambia, of which £1 10 ($310) represents
the cost of the canoe.
Fig 12. A flat bottom canoe for swamp and river
Several designs used
The round-bilge plank canoe (banana boat) is not the only
craft considered as replacement or an advancement on the
dugout in Zambia. A number of other designs have also been
tried with greater or lesser success. A dory type craft was
not acceptable because of the difficulties in paddling; a flat-
bottomed plank canoe, (ig 12 developed for poling in swamps,
was found less seaworthy than the round-bilge plank canoe
and with larger channels being developed, the latter craft is as
effective. An 18 ft (5.5 m) gillnel skiff of plywood construc-
tion has found little favour with many fishermen because of
the high cost of necessary maintenance, consequent on poor
quality local plywood and high running costs. Recently a
24 ft (7.3 m) beach boat (FAQ design BB 59) has been tried
with some success, although the plywood construction was
not entirely acceptable due to damage by chafing on rocks
and sand. However, a modification of a glass fibre sheathing
is expected to overcome this problem. The inboard-powered
beach boat, as an advance on canoe-type craft, is considered
to have possibilities in Zambia, particularly where a fair
carrying capacity is required over considerable distances.
Experimental craft of this type are also being constructed of
fibreglass.
Canoes in the Pacific
Powell (Cook Islands): There are probably more canoes used
as subsistence fishing craft in the Pacific than all other types
of craft combined. In Melanesia the single hulled dugout
canoe has and will probably always remain a popular type
of vessel in all villages which face the sea, a lake or a river.
In Micronesia and in Polynesia the canoe with an outrigger
is generally preferred. Where water is generally calm and the
prevailing wind is not strong, a single hull is more easily
paddled, and children growing up in village canoes, develop
the natural sense of balance which makes work possible in a
canoe.
In the atolls and high islands of Polynesia where much
fishing has to be done in the open sea, the outrigger canoe is
common. It has been suggested that the outrigger float
became necessary way back before recorded history where
canoes had to be made from logs which were too small in
diameter to make canoes with sufficient beam to be accept-
ably stable. This may be true, but it is interesting to note that
when the first European sawn lumber was introduced into the
Pacific, and it became possible to build canoes from planks,
the use of the outrigger persisted and the traditional beam
length ratio is maintained.
Polynesian fishermen who work in rough water prefer a
canoe with a beam sufficiently narrow that a man sitting on
the centre thwart fits comfortably into the canoe. It is then
possible to feel more control over a canoe which can be
505]
turned against the thrust of the paddle. A wide-beamed canoe
is more difficult to control, as one tends to slip from side to
side in rough water without being able to brace the outside of
the thighs against the inside of the planking.
Value of the outrigger
There is a very good reason, of course, for the preference
for the outrigger canoe where ocean fishing is practised.
The advantages are not always appreciated fully by strangers
to these islands. In the first place, the outrigger canoe is
certainly not an easy craft to handle even in a lagoon. Its
idiosyncrasies make it particularly perverse to anyone who
does not appreciate that it is very sensitive to trim fore and
aft. Polynesians, of course, have learned to use these seem-
ingly unhandy tendencies to the best advantage. Outrigger
canoes will always be preferable to open boats, when fishing
has to be done over the ocean where the bottom is much too
deep to make anchoring possible. These conditions exist in
most areas where tuna and large pelagic fish are sought.
An advantage under these conditions is that the outrigger
canoe with a reasonably heavy buoyant outrigger is more
stable than a small boat. One sits facing forward and in
consequence has a better view of the conditions which make
fishing at times hazardous. Where very deep lines are used
and it is necessary to keep a canoe vertically over the line in
strong winds and tide, it is possible to tuck the paddle under
the left arm and with a sculling motion keep the craft head
to wind and sea. Most fishing is done in depths where a line
length of between 50 and 250 fm (90 to 450 m) is used. The
yellowfin tuna, wahoo, marlin, castor oil fish and large
sharks are all heavy fish, They are all capable of breaking
the planking of a canoe and all are powerful enough to
cause a capsize if not handled with great skill. When a large
fish is finally hauled alongside, it is essential that the fish is
finally turning in the right direction before one starts to club
it. This has to be done at times while the canoe has to be
kept head to wind and sea. By day it is a hard means of
fishing. In a strong wind and sea on a dark night with no
help available should a capsize occur, it is indeed a type of
fishing which one needs to be apprenticed at a tender age.
Not beautiful— but they do the work!
The canoes almost universally used through the Cook
Islands are planked up with & in (8 mm) Douglas fir planking
and are built with grown frames cut from Hibiscus tiliacus.
The bottom is shaped double-ended from two 6 in (15cm)
or one 12 in (30cm) kauri board. The topsides flare out to
give the necessary sheer without recutting the top edge.
These canoes are frequently criticized as not being as beautiful,
as the fine craftsmanship which one finds in other Pacific
areas, but no-one who has worked with them offshore in a
high sea of a strong trade wind can doubt that they do stand
a surprising amount of rough water. The hull is something
like a Grand Banks dory scaled down.
It is common enough on rough days to find a group of
40 to 50 canoes working over a fishing area where they
remain invisible from one another as they rise and fall
behind the ocean swell. The trade wind freshens up during
the day and the numbers generally thin out and the better
fishermen with long experience remain on the ground, when
the tops of the seas are breaking over and the spray is driven
down wind. Under these conditions, handling a large heavy
fish is difficult. When a marlin is hooked, it is general for
someone to go to the fisherman's assistance and hold his
outrigger from either lifting or sinking too deep. A canoe
that broaches, rolls over and often breaks oft the float,
which makes it difficult to paddle ashore. Under these condi-
tions of strong wind and rough sea, fishermen will alter the
trim of the canoe by pushing all the heavy gear forward. As
the bow is depressed it holds less wind and the tendency to
become "hard mouthed*' and point up into the wind and
sea is a decided advantage. Any heavy fish caught are pushed
forward and the canoe is kept severely trimmed by the head.
When conditions become such that it is necessary to return
to shore, the reverse process is used and the trim is by the
stern. Under these conditions, the canoe will run down wind
with a minimum of effort. By contrast, an open boat must
be rowed with two oars which means that one must face aft.
The high sides of a boat make rowing in a rough sea much
harder work than paddling. While a rowing boat can be
rowed faster than a canoe can be paddled in smooth water,
the canoe scores every time when working to windward
against wind and tide.
One- or two-man canoe?
At one time two-man canoes were in favour and two men
could operate better than one man under some conditions.
It is interesting to note however that although the single-
hulled canoe with an outrigger float will stand a lot of rough
water as long as the trim is watched carefully, the two-man
canoes where the weight is carried more into the ends of the
hull is not such a good sea boat. The secret of the smaller
canoe appears to be that when the ends are light and the
weight is carried over the centre of buoyancy, the rocking
horse motion improves its scakeeping property. When landing
through surf, one is faced by the improvement in running
with the after end loaded, and in the danger of broaching
when the weight is carried centrally, which are conditions
which Pacific Islanders meet by long hard experience.
Where the temperature of the sea is high and flying spray
is not depressingly cold, one can, of course, face rough water
with much more confidence than the same conditions might
offer where grey skies, freezing spray and certain death from
a capsize would follow.
The single-man canoe much as it does the jobs for which
it is built very well, does not lend itself to commercial fishing
in many new ways. With the advent of outboards, larger
canoes are being built over the Pacific and the basic type has
been improved in many ways.
A large canoe has many advantages over a small boat when
handline fishing, trolling, lift netting and several other special
types of fishing are done commercially. In the first place, a
large canoe can be driven much faster than a small boat with
the same size of outboard. A small boat will not plane if it is
loaded heavily. To make it plane requires a large outboard
with a prohibitively high fuel consumption. If it is then
slowed down for safety reasons in rough water, it throws
spray aft which is difficult to avoid. When a strong wind
dries this salt spray in an operator's eyes, it is unpleasant. A
large canoe under these conditions will push along to wind-
ward with very little fuss at all. If the weight is concentrated
in the centre of the hull, it will, if well designed in the first
place, be quite a workable fishing craft.
How to fit outboards
Fitting outboards to canoes has always been something of
a compromise. The single-hulled canoe without an outrigger
has the big disadvantage that if it is built double-ended in the
conventional manner, fitting an outboard bracket offers some
problems of construction. Often the end is sawn off and a
small transom is fitted. One then has a type of craft where it
is difficult to get at the motor for any reason. The heavy
motor carried right on the stern is certainly in the wrong
place in rough water.
Attempts to fit motors through wells amidships are not al-
ways, if ever successful. Outboard motors fitted on the
[506]
quarter of a double-ended canoe without an outrigger float
have the big disadvantage that a canoe, like a boat, rolls in
rough water and the motor is alternatively working either
submerged too deep or with the propeller racing as the canoe
rolls away from it.
Fitting an outboard to an outrigger canoe is very much
simpler. The motor bracket can be designed to clamp about
two-thirds of the waterline aft. In this position it can still be
reached quite easily for running repairs; the weight of the
motor is in the place where the canoe can carry it best. As
the outrigger float stops the boat from any appreciable rolling,
the propeller works to its best depth. The bracket can be
made so that the motor will tilt up as needed. In canoes large
enough the motor can be bracketed by the after outrigger
cross arm which still leaves room to swing a paddle when
necessary without striking this spar.
A loose steering paddle can be used as in a sailing canoe or
a rudder hung on the stern with a deep blade can be steered
with either a yolk line or a solid yolk or bell crank bracket
attached and carried forward to the position of the outrigger.
With this arrangement, one man can operate the outboard and
steer the canoe quite comfortably.
The design of such a canoe can of course be varied without
limit to suit the type of fishing that is contemplated. For
instance, anyone wanting to use a canoe for trolling with
several lines where some rough water is expected, can increase
the height of the topsides, Some decking can be added, an
increased well combing if necessary, and many other refine-
ments that will make such a canoe quite a serviceable fishing
craft that is neither expensive nor iifficult to build. One
further advantage is that where fishing craft have to be used
without any harbour facilities, such a craft ha. quite shallow
draft and is easy to beach. If the canoe is made very large,
it is easy to haul ashore on wood or rubber rollers. Where
ample labour exists as in most fishing villages, the canoe is
very much easier to lift or drag ashore than is a boat of the
same overall weight. This is of course because the available
man power can be well spread out, where everyone gets a
good hold to push or lift. Boats under such circumstances
arc much more difficult to skid ashore as there is little place
to take a firm hold that is not too high to grip effectively.
Methods of handling
A hand winch, of course, simplifies things with all heavy
craft. When a fisherman operates with a limited crew under
conditions where it is advisable to drag the craft above high-
water mark, then the outrigger canoe is at a great advantage.
It is customary to lash together most Pacific canoes with
coconut fibre or sennit lashing. In the atolls this art of lashing
is well developed and some beautiful patterns are made. This
takes time and the lashings stay in place until they are finally
renewed. Metal is now replacing the sennit lashings. The big
advantage of metal over sennit is that metal bands can be
made into which all the cross arms or spars can be pushed on
a taper. This facilitates assembling a canoe and has the
advantage that such a canoe equipped with metal bands can
be taken apart quickly. The outboard can be lifted off then
the outrigger float can be removed quickly.
The two or three cross-arms can be slipped out of the
sockets and any light decking which might be carried over
these arms to hold nets or fishing gear can come off in one
or more pieces.
The main body of the canoe can now be either carried or
skidded ashore. When a hand winch is available, quite a large
canoe can be dragged up a beach above high water. It is
customary in most Pacific Islands to build a canoe house
where all the fishing gear is stowed in the roof away from hot
sunshine and torrential rain. This is a distinct advantage
over an open power boat with an inboard engine. Such a
craft left at permanent moorings can collect enough rain-
water in a few hours of a tropical deluge for the water to
creep up over the gearbox and engine sump. The thatched
roof of a canoe house is generally much preferable to a
"hard" roof, as the canoe, if a dugout, does not get the
severe drying out that occurs under corrugated iron.
In fishing communities where the change-over from sub-
sistence to a moneyed economy is still taking place, it is
frequently the case that labour is still not considered in terms
of a definite rate per day or hour. Under these conditions,
where much of the catch is distributed among the fisher-
men's families, it is an advantage at times to carry more men
that might seem at first to be economical to a western fisher-
man's concept of an economical number in a crew.
When handlining, the long canoe has the very superior
advantage over a shorter boat of the same displacement, in
than the handlines can be spaced further apart. This does
much to prevent the entangling of lines which is common
enough when many lines arc used from a boat in very deep
water.
Handling the sailing canoe
With most Bailing canoes, the outrigger is always carried
to windward and vvhcn tacking, the outrigger is still kept to
windward by the simple device of making the canoe double-
ended to the extent that the hull is steered alternatively from
either end. Several types of rigs have evolved which simplify
this type of sailing canoe. In Rarotonga many years ago a
sailing club was formed using the local dugout canoes and
the more conventional marconi rig was preferred to the
lateen sails. With a marconi rig of jib and mainsail, the
outrigger had to be used on one tack on the leeward side. It
was soon found that when racing in strong winds the out-
rigger float was buried under a press of sail with disastrous
results. Making larger solid outrigger floats with light buoy-
ant timber had its limits and the hollow dugout float decked
in was evolved. Making a hollow float from a dugout log
requires some skill and careful workmanship if it is to stay
watertight. Planking up a hollow outrigger float is generally
much easier although hard chine floats arc not as attractive-
looking as a well-shaped hollow outrigger adzed from a log.
In Polynesia there have traditionally been many ways of
attaching the float to the canoe. A variety of methods of
attachment nearly all have lashings of sennit. The total
assembly is always flexible. The flexibility of the outrigger
canoe is carried to the extreme in the canoes of the Society
Islands. These canoes are generally made so that the forward
spar is stiff and strong and is generally made of a local hard-
wood. In the sailing canoes, it is extended out across the
canoe to provide attachment for the rigging and also as a
precarious perch on which the crew can balance the buoyancy
of the solid outrigger float. The after end of the Society
Island canoes is then made of a very light flexible spar
which does very little more than space the after end of this
float. This has one advantage and that stems from the greater
flexibility that this arrangement gives the canoe, or in other
words, it increases the stability of the canoe to the extent
that as the outrigger is lifted into the air, the after end always
trails in the water. The stability is greatly increased in this
way, as it is quite difficult to capsize a canoe of this type
with the outrigger lifting from the water. Capsizes occur just
as easily in canoes when the float is submerged and if this
float is not buoyant enough as occurs with solid timber, it
is possible to capsize with the float driving under water.
Methods of attachment
The Society Island method of attachment is an improve-
507]
ment on the traditional Cook Islands method of using two
fairly stiff solid spars. However when one attempts to sail
with the solid spar to leeward, trouble develops as the fore
end of this float is driven under water. Once the fore end of
the float is submerged if the canoe is moving fast through
the water whether by power or sail, the submerged fore end
then drives in deeper and a capsize is almost inevitable.
Many years ago an answer to this problem was found by
combining the advantages of the Society Island flexible
attachment with a float made much more buoyant by being
hollow. These floats are generally made to be buoyant
enough to carry about 250 Ib (115kg) before they will
submerge. The hollow float is of course much lighter than the
solid float and when the stability is considered, it is general
to set the float about 6ft (1.8m) out for an 18ft (5.5m)
canoe. In a canoe of this type, it is possible for two men to
sit on the rail without it lifting the float from the water.
Finally the float was improved by making it such that the
centre of buoyancy was separated from the centre of gravity
by about 2 ft (0.6 m). The forward point of attachment was
then made between these two points. The forward cross spar
then carries all the strain of the weight and the buoyancy
when depressing the outrigger float. This means that it must
be quite substantial. The after spar has been made stiffer
than the Society Island canoes use and it is preferable to
combine a strand of wire along the edge of this spar so that
should it break for any reason, the front will not be separated
from the canoe.
With a hollow float of this type firmly attached, but with a
certain amount of flexibility still inherent in the whole
assembly, the canoe can be driven through rough water with
an outboard without the danger of capsizing from the float
either lifting or submerging. Bronze strip and rods welded or
silver soldered together simplify the method of attaching
the spars to both canoe and float. A cheaper job could be
made from galvanized mild steel.
Extra carrying capacity
Canoes of this type could be enlarged up to a much greater
size than are used at present. In many areas of the world where
large dugout canoes arc in common use, their ability to
carry nets and other gear can be very greatly improved by
attaching a hollow outrigger float. A large outrigger canoe
driven by an outboard attached about two-thirds of the
way aft from which all the spars and the float can be both
easily and quickly attached or dismantled. It could probably
be improvised in many areas of the world where outboards
cannot be used very successfully in rough water on the
traditional single-hulled canoe.
Strangely enough, a hollow float does not make the drag
that might be anticipated on one side of the canoe. Tradi-
tionally, Polynesian canoes have often been made with various
methods of counteracting the supposed drag on one side by
this float. When an outboard is attached to the hull on the
same side as the float, any drag to one side is counter-
balanced by the thrust of the propeller. It is no problem in
practice.
At the present time a canoe of 24 ft (7.3 m) is planned,
having a hollow outrigger float. Plywood and fibreglass will
be used for both the hull and the float and the canoe will be
kept to a fairly low freeboard so that it can be used on the
fishing ground with a Hawaiian Opelu lift net. This net is
used with ground bait which is released several fathoms
below the canoe. It is necessary to keep the canoe over the
net and bait and a long canoe which can be maintained
stationary over the gear by two men paddling is much
preferred to a boat which has to be either rowed or sculled.
Additional strengthening advisable
Anyone attempting to attach an outrigger to a dugout
canoe ought to add some framing to the points of attachment,
as the float can cause the hull to split down the grain if
provisions in the form of timbering or standing knees are
not added to strengthen the topsides. Motor brackets are not
difficult to design to suit both the motor bracket and the
topsides of the canoe. Bronze strip and rod is generally
easier to use than wood, although wooden brackets are
satisfactory if well designed and attached firmly. Where
dugout canoes can still be made from good timber at a
reasonable cost, they have some advantages over plywood
canoes, if they have to work over rough coral bottoms where
severe gouging and scratching of the bottom is an inevitable
part of the fishing operation. Plywood can be made much
lighter than dugout construction, no matter how well the
dugout is made. Moulded veneer with fibreglass covering is
perhaps the lightest and strongest construction of all, but it
needs good workmanship and is expensive if carried out by a
good yacht yard. The total cost of such a canoe, complete
with outrigger float and spars would be at least comparable
with a plywood dinghy. Adding an outboard to a conventional
outrigger fishing canoe greatly increases the chances of
swamping the canoe in rough water. At the same time, it
also decreases the chances of bailing the water out of a
swamped canoe.
An open dugout canoe can generally be freed from water
quite easily by rocking the canoe fore and aft. Once the water
inside has started to rush from end to end much of it can be
made to pour out of the ends until a certain amount of
buoyancy is regained. The rest of the water can then be
thrown out of a dugout by using a paddle which is shaped
something like the inside of the canoe al the ends. One then
uses the paddle as a shovel and this is quicker and easier than
bailing.
Well-made bailers
Sailing canoes are righted after a capsize by the occupants
taking all the gear under the cross arms. Then by standing
on the float and sinking it the added buoyancy lifts the hull
of the canoe high enough to make some of the water pour
out over the topsides. hrom then on, it depends on bailing.
When a deck is added to the ends of a canoe, it does a little
to keep spray from filling inside. It strengthens the canoe to
some extent and it makes it possible to keep a few things dry
below. It does help to stop the canoe from filling, but once
filled, it makes it much more difficult to bail water out. In a
sailing canoe or in one powered by outboard motor, it is
quite easy to fit a venturi bailer with a plug which drains
out every drip of water as long as it is possible to maintain any
speed over 3 or 4 knots.
In many areas of the Pacific, bailers made from local
timbers are used which generally fit the bottom of the canoe
fairly closely and do not scratch or score up the planking
after frequent use. These bailers are often well made and
designed so that they can be used to throw a lot of water
with a minimum of effort. Coconut shells sink, as do tins
and most plastic buckets. The island wooden bailer is a
useful piece of fishing gear.
Outboard problem when swamped
When outboards are attached to the traditional canoe they
then offer the problem of what to do with a swamped canoe.
The added cruising range which a motor gives also brings the
added risk of being swamped offshore at night. While the
wooden canoe has a natural buoyancy, it is seldom enough
to float an outboard and still leave enough freeboard to make
bailing possible. Generally an outboard will take a small
[508]
canoe which is filled straight to the bottom. One then has to
cast off the motor quickly and drop it in deep water unless
some provision is made beforehand. The better alternative
is to build some buoyancy chambers into a new canoe or
adding some foam plastic, inner tubes or some similar type
of light buoyant material well fastened in.
Foam plastic poured in place is probably the easiest
material to use where it is available at a reasonable price.
Plywood and fibreglass are other easy ways of building
buoyancy chambers into the canoe without greatly adding
to the overall weight.
In the Hawaiian Islands, most of the small boats carry live
wells which make it possible to keep small bait fish alive. Live
bait is regarded as a necessity when fishing some species.
The live well also improves the appearance of the fish which
have to be kept for a long time, often all night, without any
ice. Live bait wells are easy to build into a canoe, as the ends
can be made as permanent bulkheads right across the canoe. It
is important, however, that the well is either carried up to
the top of the gunwale or some plugs arc always kept
attached permanently to the canoe, so that in the event of
swamping it is possible to plug oft' the well section.
Evolution of centuries
The Polynesian canoes have probably taken thousands of
years to evolve into their present simple form, that do one
job in one locality well. In every island one can see limiting
factors which make a slight change an improvement. Poly-
nesians, like all fishermen in the world over, are just as
DECKING BULKHEADS PORM
LIVE BA'T WELL
OUTBOARD MOTOR
LOAD WATERLINL
MOTOR BRACKET
Fig 13. Section of outrigger canoe
conservative and just as reluctant to change from methods
handed down through generations of fishing families. But the
western world is already bringing materials that never existed
before and the inevitable change from a subsistence to a
moneyed economy is already spreading across the Pacific.
As this happens, the traditional paddling and sailing canoe
offers quite an interesting place from which to start to add a
power plant, mechanical gear haulers and all the factors
which are necessary to change fishing from a means to an
end into almost an end in itself.
Fig 13 shows the heights of the struts in proportion to the
canoe. The cross arms should be level when the canoe is fully
loaded. The outboard motor bracket can be made from
either wood or metal. It is preferable that the fore side of the
bracket contains a piece of wood or sheet metal as a spray
deflector. Fitting this will depend on the actual motor in use.
Wood or metal can be used for the outboard bracket. Wood
is easier in some areas where metal working facilities are not
readily available.
Steering the outrigger canoe
Fig 14 shows three alternative methods of steering an
outrigger canoe :
A shows a double-ended canoe with a straight stern post.
Rudder pintless and gudgeons arc attached to post and
rudder in the conventional way. This is simple, cheap and
strong. The rudder is linked to « tiller mounted inboard or a
"bell crank" or yolk lines can be used.
B shows a curved steering oar made out of cither laminated
timber or from a piece of grown hardwood. It is particularly
useful where it is necessary to stand up to steer when man-
oeuvring through rocks or lagoons full of coral. The oar
passes through a metal rowlock which is drilled and pinned
as shown.
C shows a rudder mounted on the port side of a rounded
stern canoe. The side mounting saves problems with the
curved stern post. The rudder is detachable and can be made
to tilt when desired. The whole rudder assembly can be made
of either wood or metal.
Fig 15 shows a typical small outrigger canoe fitted with an
outboard. This arrangement is suitable for canoes up to
about 25 ft (7.6 m). The decking can be made up in a variety
of ways depending on the work for which the canoe is used.
Light spars easily attached to the cross arms can be so made
that they carry fishing nets, traps, pots or any variety of gear
which does not depress the float too deeply. The spars made
of either light timber or bamboo can be covered in turn with
a woven mat of split cane, or a piece of heavy canvas, or
heavy fish netting. This gear should be made so that it is
easily detached so that the canoe does not have to be lifted
ashore as one unit. Spears, dip nets, gaffs can all be stowed
out of the way on this platform.
If the outrigger float is buoyant enough, it is a handy
place for working if some provision is made to stop the
outrigger float deck from being slippery when wet. The after
arm should be so made that if it becomes broken in use
LINKAGE TO TILLER
B
PIN THRU ROWLOCK
LINKAGE ROD TO TILLER
STRAIGHT STERNPOST
RUDDER ON PINTLES
AND GUDGEONS
CURVED STEERING OAR
PIN IS ESSENTIAL
CURVE GROWN OR LAMINATED
Fig 14. Alternatives for steering outrigger canoes
[509]
TILTING RUDDER MOUNTED OUTBOARD MOTOR
ON WOODEN OR METAL BRACKET
OUTRIGGER CANOE WHICH CAN
EASILY BE TAKEN APART FOR
STOWAGE OR PORTABILITY
HOLLOW FLOAT
LIGHT DECKING COVERED
WITH CANVAS OR NET
OR WOVEN CANE
BATTENS OR BAMBOO
FLEXIBLE CROSS
OUTBOARD MOTOR
Lt-HEAVY CROSS ARM
Fig 15. Arrangement of smaller outrigger canoe with outboard. Note position of outrigger
there is some attachment still remaining to the canoe. This
is easily done with a strand of wire along one edge. If the
after end comes adrift in rough water, it generally means the
float takes charge and does some serious damage.
Protective measures
Fig 16 shows a very large canoe fitted with an outrigger
and an outboard. As the float becomes bigger, it can be
carried closer to the canoe as the stability increases. A light
diagonal wire, as shown, takes the strain off the gunwales
of the canoe and adds some strength to the whole canoe.
This is especially desirable where the canoe is used at night
in amongst coral or rocks where the point of the float can
strike anything solid. It is advisable to round up the forefoot
of both the canoe and the float. Live bait and fish wells are
very desirable in most tropical areas. The tiller and linkage
as shown can be used to some advantage where it keeps
weight out of the ends of the canoe when beaching through
surf. The side mounted rudder can be detachable and can
tilt up. Decking on the ends of the canoe will be dictated
entirely by the local conditions.
In general, it is very advisable to finish the ends of all
spars and all exposed surfaces to a well-rounded edge to
avoid damage to light nylon nets. When damage still occurs,
a piece of canvas large enough to cover the working area,
will save a lot of labour net mending.
Traditionally, most Pacific canoes are tied together with
sennit made from coconut fibre. Some very beautiful lash-
ing patterns are possible and the sennit has the advantage that
it does not become loose through stretching with alternate
drying and soaking. Nylon braided line is now being used
where sennit is no longer made. Metal bands are not as
flexible as the traditional sennit, but do make the canoe
portable when it can be easily broken down into unit pieces
within the capacity of the available crew and local conditions.
Anyone not familiar with canoes in their area may well
find a choice between the type of canoe as illustrated and
described and a double canoe. The double canoe, or cata-
maran, as it is becoming known in yachting centres, is
regarded in this case as a craft where both hulls are the same
size and a deck is carried across between the two hulls. To
compare the two hulls is of course to point out the ad-
vantage and disadvantages. It is obvious that in some areas
one or other will be preferred, depending on the type of
fishing gear used. It is seldom that one type will do both jobs
equally well.
Respective advantages listed
Single-hulled canoes with outrigger: the advantages might
be as follows:
• Dugout canoes are traditional in an area and are a
readily acceptable type of craft
LIGHT DECK COVEREDWITH BASKET TYPE CANE NET OR CANVAS
RUDDE
^•^•^
~^^^
s^WlRE BRACE
>==£=
^M
V \
^.
^^—
-y-
T"^
\
\
\^ \
X N»
'-H
1 ~--:>
LIVE WELL TILLER MOTOR STRUT LIVE WELL
TO BRACKFT
Fig 16. General arrangement of large outrigger canoe with outboard
[510]
• If large timber is still available, local craftsmen can
make dugouts which already suit local conditions
• The dugout can be left thick below the waterline to
withstand coral
• When broken down, the single dugout canoe, if
heavy, can be skidded ashore to a boat shed
• A single motor will drive the canoe if mounted as
shown
• The long canoe is much to be preferred when line
fishing is done in deep water. The long canoe spreads
the lines further apart, which is a big advantage where
the lines are used in deep water
• Building a large canoe and a hollow outrigger is
generally cheaper than a catamaran
• Nets can be handled from the platform as shown, for
most types of net fishing
• Single-hulled outrigger canoes are generally far easier
to use with either paddles or sails, should the motor
break down
The advantages of a two-hulled canoe, the catamaran, are:
• Where nets such as ring, gill or barrage nets are used,
the catamaran has a fine wide platform between the
two hulls, which is advantageous for both hauling and
setting nets
• Light plywood hulls covered with fibreglass are easy
to build where this material is available at a reason-
able price
• One motor is not as satisfactory in a catamaran, as in
a single-hulled canoe
• Two outboards arc at* added safety factor
• If the hulls are left without decking, they might be
suitable for line fishing, but they are not either as easy
to keep up in a head wind and sea with paddles as is a
larger single hull
• The spread of the lines when hook fishing is not as
great
• Where possible to buy large American outboards
cheaply and keep them locally serviced, the double
plywood-built catamaran is a useful craft for many
purposes
• In isolated and backward parts of the world the large
modern outboard is still next to impossible to keep
serviced. Fuel is far too expensive for it to be practical
in most Pacific islands
The canoe builder's skill
Chipcpo (Tanzania): The tree which the canoe-maker uses is
a local wood which is called muninga or mupapa in East
Africa and mukwa in Zambia. These two countries use the
same wood for canoes. The canoe-maker can go into the
forest with two or four men to help him to fell the tree. First,
he can sec that the tree is free from kinks and hollows in the
side, by looking far off to see how the leaves look, then he
can give orders to fell the tree.
The canoe-maker has three axes to fell the tree and chop
off the branches. The second tool used is an adze — three big
ones and two small ones—the bigger ones help him to scoop
the hull and the smaller ones are used for finishing.
Fire and mud can be used after two or three months, when
he finds that the hull is quite dry. He starts to smear the hull
with mud inside and out and then he makes a fire inside and
when the hull is hot he starts using the spans to expand the
hull and make it into a good shape. The measurements which
the canoe maker uses is to stretch his hands eight or ten
times — giving him the length overall.
Not everyone in the community can make a canoe. This
skill is limited to a few groups of specialists. This means
then that a canoe maker occupies an important part in society.
From the forest to the river the canoe maker is very
worried. He is not sure of the stability of the hull and hides
himself near the river until he hears the joyful cries of tne
women shouting and clapping their hands. After the launch-
ing, three or four men start paddling very rapidly and then
you can see the hiding canoe maker jump for joy.
Eventually some of these canoes will be mechanized with
outboards and the experience gained by other developing
countries will be of much benefit to Tanzania.
Eskimo Practice
Frechet (Canada): The eskimos of Canada, who go fishing
at great distances from the shore, are normally accustomed
to carrying their kayak on their komatik (or dog sled) down
to the shore. Then they have to leave both komatik and dog
team and continue alone in the kayak to the place where they
intend to fish. Being made of skins, the kayak is rather fragile
and often tears on sharp edges of the ice. Clearly, something
had to be done about this.
In another part of Canada, the inhabitants of the islands in
the St. Lawrence river downstream from Quebec, have from
time immemorial, crossed the river which carries down a lot
of ice, in wooden canoes having greatly elongated extremities
to enable them to ride up over the floes. These canoes were
once built of massive oak and had steel runners that made it
easy to drag them over the ice, but they were very heavy.
Nowadays canoes are made of reinforced fibreglass and
also of aluminium. The aluminium canoe accordingly offers a
useful substitute to both the komatik and kayak. The eskimo
can keep his dogs near him and hitch them up to his canoe in
order to haul it over the ice.
Over the great stretches of frozen lake, the half-track
vehicle with skis fitted to the fore-carriage has become one of
the most widely used vehicles in fishing operations. It comes
in a number of sizes and can be used not only for standing
line fishing and gillnetting, but also for trapping.
Small craft, powered by air-cooled motors, are now being
produced in reinforced fibreglass. Among the new craft used
for fishing over the ice may be mentioned the many alumi-
nium boats propelled by air screws.
The greatest novelty of all, however, is an amphibious
vehicle (dimensions range between 13 and 20 ft (4 and 6 m)
with power units of between 60 and 80 hp) which has a series
of very fat balloon tyres in a line along each side. Vehicles of
the kind are capable of 60 miles/hr (100 km/hr) on ice and 8
knots on the water. Propulsion in water is obtained by con-
necting the engine to a hydraulic turbine providing a per-
formance akin to that of a propeller. In the intake duct
there is a knife-edged propeller-like device which crushes
small pieces of ice or cuts up aquatic plants. Such a vehicle,
therefore, can take any water conditions as well as offering
cross-country transport— oversleep mountain slopes, shingle,
mud, marsh and snow and ice, or other adverse conditions.
A Canadian project has been underway for several years: the
development of a free-piston engine capable of using fish oil
as fuel and particularly adaptable to fishing craft.
Modern materials displace old
Lee (UK): It is of considerable interest to note that glass
reinforced plastic craft are replacing the traditional dugouts
and other wooden craft. It would be useful to learn whether
there is any difficulty in hauling them over the beach and
whether the plastic is withstanding abrasion.
The use of styrofoam (expanded polystyrene?) is queried,
observing that this material breaks down in the presence of
gasoline and oil; expanded polyurcthanc or poly vinyl chloride
would be much better.
[511]
Stability
Zhnmer (Norway): Making a dugout canoe means a lot of
hard work and a lot of wasted wood and the final result is
rather inconvenient as a fishing boat. The way of making a
dugout is based on times when man did not know how to
make watertight connections between planks. The dugout is
something of the past and will disappear.
As a naval architect, Zimmer made some remarks about
dugout canoes. The tree trunk limits one to a circular amid-
ships section. Positive stability means that the centre of
gravity is below the metacentre, which is permanently in the
centre of the midship section circle. When a man is standing
up in the canoe the centre of gravity is higher than the meta-
centre, but because the weight of the man is acting where his
feet are touching the canoe, he has control of the canoe. The
strange thing is that, because of this, a man standing up in a
canoe can give better steadiness to a canoe than a man sitting
down and holding onto the rails of the canoe.
Zimmer had another experience with a plastic boat of
typical V-bottom boat midships section. The bottom of this
boat started flexing under speed. To correct this, the designer
put in a double bottom at about waterlinc level with poly-
styrene foam in between. When it started raining or a lot of
water collected in the boat, the centre of gravity was raised
to a point above metacentre; then the CM became negative
and the boat turned upside down.
Canoes will not disappear so soon
Traung (FAO) : Zimmer is probably not correct when he says
that dugout canoes are something of the past and will soon
disappear. For the next 50 to 100 years they will certainly
outnumber other fishing craft, because development is un-
fortunately not very fast.
Thomas, in his paper, as well as Stoneman, Heath, Powell
and Chipepo give very good accounts of dugout canoe con-
struction and, if this had been a meeting of ethnographers,
FAO would probably have invited contributions from a
great many other areas using dugouts as well. Perhaps some-
one could organize a dugout symposium one day.
canoes developed by such officers. Fig 17 is an example of
such activites, which certainly doesn't leave much to admire.
An example of what also is happening is the man who
wanted to make an 80 ft (24 m) dugout. He had found the
real dugouts of his community to be good surf-going craft
and he assumed that a larger version would keep the same
good qualities. He obtained a drawing of an 80 ft craft made
of aluminium, which was well fitted out with staterooms and
no less than two WCs. When asked about the scheme, the
FAO Fishing Vessel Section said it was "interesting", which
SBM E polite way of saying they did not agree to the idea. He
went to his Government with the letter, saying that FAO had
approved his project and then FAO had to explain the use
they made of the word "interesting".
While FAO Fishing Vessel Section does not believe in
building "dugout" canoes, of any other material than logs,
it has had good results with improving the stern as suggested
by Thomas and fitting canoes with outboards. If no logs are
available and boards, plastic or any substitutes must be used,
more boat-like forms are more economical and efficient.
New type canoes give increased safety
Heath (Zambia): In developing countries, the numbers of
dugout canoes run into hundreds of thousands — this is
acknowledged by FAO. The dugouts every year are the
cause of loss of life, yet in Zambia in the last ten years, there
has not been one capsize or drowning recorded from these
23 ft (7 m) round-bilged canoes. In many countries, trees
large enough for dugout building are becoming harder to
find. The answer is surely canoes built of planks.
If FAO is opposed to canoe development, what is its answer
to the problem of dugout replacement in subsistence fisheries,
as dory or dinghy form boats are not accepted by the in-
digenous peoples ?
In developing countries, the replacement of dugouts is a
very real problem, that is why the drawings of a proven canoe
were submitted for the benefit of others. The flat-bottomed
canoe design for rivers and swamp areas will certainly not be
suitable on the large lakes.
Fig 17. A dugout replacement made of mahogany planks at N'Guigmi, Lake Chad
Dugout canoes are made of both hard and soft woods.
When made of hard woods, there is naturally, as Zimmer
says, a lot of wasted wood, but when made of certain soft
woods as is the case when using cotton wood trees in Jamaica,
there are not many other competitive users for the wood.
This is not always realized. When using hard woods, one can
utilize the cubic content of a log much more economically by
sawing it up into boards and making boats like the banana
boat described by Heath. However, not being restricted to
the diameter of the log, it would require very little more
wood to make the craft with a more normal beam than the
4 ft 5 in (1.35 m) now used. A 7 ft (2.1 m) beam would give
a boat almost twice as large, with hardly any larger con-
sumption of wood or labour.
Expatriate fisheries officers in developing countries often
consider themselves experts of boat design and construction
and one can see shocking examples of planked "dugout"
Size needed for major progress
Von Brandt (Germany): Each fishing method requires a
minimum length of boat and a minimum horse power. Very
small boats are necessary for the so-called baby-trawls, as
used in the Philippines and some fishermen of Madagascar
use only two pieces of wood as a raft for handlining. But
these methods have no influence on the production of large
quantities of protein. This can be done by bigger gear, only
like large bottom trawls and purse-seines, which are not
adaptable from the indigenous craft as mentioned in Thomas*
paper. Therefore from this point of view, mechanization of
indigenous craft cannot be the final step and it is unfortunate
when some authors argue that the mechanization of canoes
and open boats is the best way for fishery development. This
leads only to a cul-de-sac.
Also for handling the fish onboard, a minimum space is
necessary. The small open sailing boats of the fishermen of
[512]
Sierra Leone can be found 20 miles offshore. They have two
stoves to smoke and dry the fish and some boxes to store
them in. To mechanize these boats would have only limited
success. In Germany, the fish processing people have some
doubt if even a vessel of 65 ft (20 m) is big enough to have all
the equipment necessary to guarantee the quality of the
catch required in the future. Also from this viewpoint, a
minimum size of boat is necessary and the mechanization of
small indigenous craft has no value.
Gurtner has mentioned in his excellent paper that four
steps of development are necessary for the mechanization of
indigenous craft to the development of national or regional
boat types. Von Brandt agreed with this idea. As explained
before, from the viewpoint of a gear technologist who has to
look for bigger catches and from the viewpoint of a fish
processor who has to look for better qualities, these very small
craft, such as canoes and open boats, have no place in a de-
veloped fishery with all their need for high productivity and
quality.
Even if small craft today have an important place in
developing fisheries, this situation must be overcome and not
stabilized.
NEED FOR TRAINING FISHERMEN
Sutherland (UK): Attention is repeatedly drawn to the prob-
lems facing developing countries and many possible solutions
suggested. Some of these are of real value and should be
borne in mind by FAO; others however showed little under-
standing of the difficulties which face the technician in the
field.
Thomas in his paper lists the various pros and cons of
indigenous fishing craft. A further point worthy of considera-
tion is the danger that if the building of modern fishing craft
outstrips the mechanization of local craft, there will be
insufficient trained fishermen and engineers to run these
modern vessels successfully.
The motorization of indigenous craft should be continued,
firstly because of the low cost and secondly as a means of
training fishermen to become familiar with mechanization.
Again the high cost of modern fishing vessels may create
anomalies whereby the fisherman may find himself working
as a crew member in company-owned vessels, instead of
owning his own indigenous craft. An illustration of this is
given in Gunner's paper where he states that new 36 ft (1 1 m)
shrimp trawlers were bought by processing firms. Sutherland
presumed that they were crewed by local men, whose chances
of saving sufficient money to obtain a modern craft would be
very low. On the other hand, the dramatic effects of fitting
outboards to indigenous boats in Ceylon was given in a
previous paper by Kvaran. He stated that the average daily
earnings of a fisherman in a catamaran was l/6d (20 cents) a
day and this was increased to 13/6d ($1.90) a day after an
outboard was fitted. With this increase of earnings, the
fisherman will eventually find the necessary capital to launch
out and become the owner of a new modern boat.
Most inshore fleets in European countries are economically
successful and this is almost certainly due to the vessels
being skipper-owned or collectively owned by the crew.
BEACH LANDING
Carey (New Zealand) : A fishing boat was fitted out some six or
seven years ago with wheels to aid beach landing, fig 18. It
has proved so successful that every boat in the area was soon
equipped with the same gear. When first fitted, trailer wheels
were used on a hinged A bracket made of 2 in (5 cm) pipe.
The hinges were just below deck level and bolted through
the gunwale. On the bar of the inverted A bracket, a lug was
welded and when the wheels were down this was engaged by
*«AME ABOUT IS TO JIN
TO SIMM) GALXANiltO P:l»l
Fig 18. New Zealand beach boat with wheels
a form of tower bolt attached to a support block firmly
bolted to the ship's side a few inches above the waterline. This
held the wheels firmly in the down position. When the boat
was afloat the tower bolt was released and the wheels folded
up by pulling a lanyard with which they were lashed in the
upward position. All this arrangement was forward of the
working area of the boat about 2/3 of the overall length
from forward.
These wheels did not carry the weight of the boat but
merely supported her on even keel while she is hauled up or
down the beach by means of a winch and wire rope, the rope
being attached to a stainless steel shoe running the full
length of the keel. The wire rope can be hooked on to the
forefoot or to the end of the heel which is supported by a V-
bracket to each side of the transom. The stainless steel shoe
is important as it does not rust or cut into the beach. The
wheels were arranged to clear the bottom of the keel by an
inch so that the weight of the boat was not thrown on them.
The idea works well although the beach at times got washed
clear of sand and punctures were common on the exposed
rocks. So solid rubber tyres were tried and these proved
satisfactory for a while until further deterioration of the
beach surface caused the wheels to collapse. Some of the
boats are now fitted with all-steel wheels with a 4 in (10cm)
wide steel tyre. The steel wheels are standing up to the batter-
ing, but the rough condition of the beach is now telling on the
hulls of the boats. It would seem that the original pneumatic
tyre is the best if the beach surface is good.
Operating Practice
The method of using the apparatus is as follows: As the
boat comes through the surf and grounds, both wheels are
lowered and one of the crew gets out on to the beach and
engages the lower bolt of the wheel bracket on the high side,
the other crew member then rolls the boat over on to that
wheel while the other lower bolt is engaged. The winch wire
is hooked in and the boat pulled up the beach. The wheels
are let down to support the boat. When ready for launching,
the winch wire is hooked in astern and the boat hauled out
until she is afloat. There arc variations of this technique to
suit the fishermen concerned.
It appears that the maximum height that the surf runs when
landings can safely be made is 4 to 5 ft (1 .2 to 1 .5 m), although
boats have landed under heavier surf conditions of up to
8 ft (2.4 m). This is not normal as they would not get off the
beach if a heavy surf were running and only occurs when a
wind and sea get up while they are fishing. The particular
place they land is between two reefs and great care has be to
taken not to breach as there is very little space to turn and
[513]
go out to sea again. The fishermen, however, claim that the
particular model of boat would land safely in heavier surf
conditions if more space were available, such as a long beach
with a true surf coming in, and some of these boats have had
to do just this when conditions have forced them to do so.
At the landing place in Nuggets Bay, the surf breaks
100 yards off shore in NE weather when the beach is then
exposed to the sea and wind.
Features of the coble
Towns (UK): The traditional inshore fishing boat of the NE
coast of England is the coble. Developed for launching from
exposed beaches and originally sailed, fig 19, they are now
built with inboard engines and are often built much larger.
The design has altered little — the same peculiarities of design
in relation to sailing ability, and the same construction are
still adhered to.
Fig 19. Model of a 27ft (8-2 m) coble showing the fine, deep
forefoot, deeply raked rudder and narrow stern
Some smaller versions of modified design and much lighter
construction have been built for pleasure fishing off open
beaches. From their performance in surf, it would seem that
larger boats of the same construction and following the same
modified design principles would make satisfactory beach
boats for commercial fishing. The displacement of these
smaller boats was distributed more towards the ends, fig 20,
reducing the forefoot, which caused broaching when running
in sailing cobles, and broadening the stern so that more
power could be used. The design problem of surf boats is
made much easier if the boat is made to launch and beach
bow to sea, so that each end performs its own particular
function, whether being beached or launched. If a boat is
designed to be beached and launched bow foremost, then the
logical conclusion would be almost identical ends, both of
which would be a compromise.
An inboard well for outboard motor was incorporated and
a tunnel, fig 21, so that, with the motor raised, the propeller
Hg 21. A 16ft (4-9 m) coble with tunnel
could work without touching the beach, so enabling power
to be used from the commencement of launching, fig 22 and
23. Weight was kept to the minimum, consistent with strength.
This simplified hauling up beaches. An outboard was also
preferred, because this could be removed to lessen the weight
of the boat for the same purpose. It is also thought that a
light boat is easier to handle in surf. Glued clinker plywood
construction was used with a system of including stringers
between the side planks at the landings, fig 24, where the
angle between planks was more than 30 degrees. This gave a
Fig 20. A 16 ft (4-9 m) coble showing sections general layout
and posit ion of motor well and tunnel
Fig 22. A 16 ft (4'9 m) coble* motor being started in shallow water
with engine raised xo that the propeller is entirety within the tunnel
wide bonding surface and incorporated all the stiffening
required; no floors or timbers were needed. With this method
an almost round-bilged boat can be built as easily as a hard
chine design, but much stronger for the same weight as the
width of the unsupported plywood panels is not great. The
amount of stiffening and the width of landing that can be
obtained is, within reason, unlimited.
Considerable tumble home was given to the sheer plank,
as on large cobles, as this adds very greatly to the general
stiffness of the boat. This plywood construction, with all
other timber laminated, has stood up very well to sand
beaching, but a more resilient form of construction might be
necessary for rock-strewn beaches. The building system
1514]
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^:^ii#!*' •-•'f%^:i''*'^ffi:*. '' ^*^ i?t" •*"*' ^ ^. ""'v •••*^|p®3P'- ;^ '• ••'•V<Pt' '
.•^i^' VWIP^ W'A-i^v* ^S5
' '
2.?. /4 76 /r (4-9
H'/7/r motor in working position
requires little boatbuilding skill and is suitable for repetitive
production. The basic principles of coble shape would seem
to merit much more study. With modifications to suit power
requirements, rather than sail, and a much lighter construc-
tion very useful surf boats could be developed.
Fig 24. Glued clinker plywood construction with built-in
stringers
Southern Californian surf boats
McKinley (USA): The 300 miles (480 km) stretch of flat hard
sand beach of the Pacific shore from Santa Barbara to the
Mexico-USA border has been used in the past ten years by a
rather unique trailer-launched outboard-powered surf boat
to fish for lobster and, where legal, to longline for shoal
water food fish very successfully.
In the early days the few boats that fished through the surf
were mostly open heavy skiffs powered with old automobile
engines (with a rare gasoline marine engine), a few had
small 1 5 to 25 hp outboards. These boats were wrestled with
great labour on and off primitive trailers towed behind old
passenger cars and were rowed through the surf until the
engines were started and then lumbered off toward the fishing
grounds to return later to the launching area, rowed back
through the surf to be hauled by main strength back on the
trailer again. The hulls which were heavy, wall sided, and
flat bottomed, with a planking thickness more suited to ice
breakers than surf boats, suffered from deep draft because an
inboard engine had to have a skeg to protect the propeller
and the whole thing was most unsatisfactory.
The advent of good marine plywoods and the improvement
in outboard engines both from a salt water compatability and
power output standpoint led to a swift evolution in hull
design so that a far lighter, yet stronger hull powered with a
far more reliable and higher powered engine came into
general use. There was still some problem with hull weight,
however, as the boat still required many ribs or frames and
strong keels to be able to withstand the shock of breaker
impact and of grounding hard on the bottom when landing
through the surf with a full load.
The introduction of a system of sheathing the entire
exterior of the hull with fibreglass cloth at last allowed a really
serious re-design of the whole boat with a drastic reduction in
frame weight and planking thickness due to the increased
shell stiffness the fibreglass imparted to the hull. A welcome
number of dividends also arrived when using fibreglass such
as a very greatly increased abrasion resistance, absolute
water lightness of the hull scams and joints, a very large
reduction in skin friction and best of all much reduced main-
tenance on the hull of the boat.
Along wilh this came light-weight transistorized fatho-
meters and voice radios that were completely self-contained.
Competition for markets brought prices down. The surf boat
and all its systems went through a rapid development in a
few years and the boats are now using powered pot or line
haulers, radios and depth finders that were only found in far
larger boats ten years ago. Equipment — "gurdy" or pot
hauler — located usually starboard slightly aft of amidship —
is a horizontal or vertical capstan driven by a 2} to 8 hp
single-cylinder air-cooled gasoline engine which sometimes
drives bilge pump too — engine protected by box.
The immense growth in pleasure boating (mostly out-
boards) led to great improvement in boat trailer design so
that shortly the slogan "one hand launching and loading*'
was no idle boast, fig 25.
Beaching and transport trailer— steel frame -two wheeled
with wide section large diameter auto wheels and tyres-
cradle fitted with one or more rollers and hand winch— tyre
sometimes partly deflated during launching and beaching for
better floatation on soft sand— reinflation for highway
towing by high pressure air bottle—special hubs on wheels
for water-tight bearing seals.
Tow truck usually i to J ton pick up type— four wheel
drive rare as expensive. Wheels split rim with oversize so
called "beach buggy" tyres front and rear — sometimes fitted
with front mounted winch driven from engine of truck via
transfer gear and dog clutch (rare). Trucks are usually very
old used models as salt water damage ruins them in two or
at the most three years. It is customary to swap winch,
wheels and engine from truck to truck as corrosion destroys
old one and it is junked and replaced.
Launch and beaching procedures are the same for lobster
or trot line fishing:
• The chosen site is one reasonably close to the operating
area that provides a smooth hard sand or gravel
approach from a road and is reasonably free of reefs
or rocks that may make launching and retrieving too
hazardous
• After the boat and gear has been made ready the truck
and trailer are backed into the surf until the surge will
lift the boat slightly free of the trailer
• The fisherman starts the already warmed engine and
as a surge nears engages the engine
• The beach man (or woman ) watches for the signa
from the boatman and as the surge arrives and the
[515]
R2
boat moves aft of the cradle he engages the truck
clutch and moves the truck and trailer clear of the
departing boat
Depending on whether it is a stern or bow first launch, the
boatman either backs into deeper water and then waiting the
next surge spins the boat at full power around until he is bow
on to the surf or else if launched bow first uses full power and
the next surge to find deeper water and position himself to
enter the breakers. As the breaker collapses the boat enters
with moderate speed the foam of its advance and then at full
power punches through the wave and into the slack water
beyond. Entering the slack power is again feathered to adjust
position and the surf passed using alternate bursts of the
throttle or idle to thread the rest of the surf system until
outside the surf line.
Returning again is greatly aided by the "walkie talkie" to
receive advice from the truck driver as to the area of the
least surf and the truck will position the trailer as an aiming
point for the boatman on the beach opposite this area.
Once the beaching point is established the boatman
watches the surf for enough time to pick the proper wave which
is followed in on the back slope through the break point by
use of the throttle to keep from overtaking the breaker and
keeping ahead of the following wave.
As he approaches the trailer the beach man raises the
tounge of the trailer and the boatman rides the surge right
up the centre line of the trailer and holds the boat there with
the throttle. The beach man then drops the tounge and
rapidly hooks the trailer winch cable on the boat's towing
ring located on the boat's stem slightly below the waterline.
Once the winch line is pulled taut both boatman and truck
driver man the winch and shake the hull all the way forward
over the trailer rollers. The truck is then either hitched to the
trailer and boat and trailer pulled clear of the water or else
boat and trailer pulled clear using the power winch on the
truck front bumper until high enough above the surge to
allow the truck to hitch up as before.
The above sounds very chancy but with some practice is
very rapidly done in rather a high surf. Practice is required
and speed and co-ordination between both men essential.
Surf boats— hull
These boats are a local built design called the "Cardiff
Skiff" and are made of marine plywood (best construction
or of "exterior" grade commercial plywood). The cheaper
wood is good for at the best only 3 to 4 years and its lasting
quality depends on an outside sheating of fibreglass cloth for
watertightness and abrasion protection. Interior of the
cheaper boat is thickly painted with a cheap oil base house
paint and fasteners are nailed.
The best construction boats are bronze screw or monel
"anchorfast" nailed and all joints, frames and woodwork
glued as it is assembled. These boats are also sheathed with
fibreglass cloth and a better grade paint used inside. To date
the oldest boat is nearly 10 years of age and is still in excellent
shape. Fibreglass bottom is renewed as required (average
once yearly) and this is the only major upkeep expense.
The boats average 16 to 18 Loa (4.9 to 5.5 m) and 6} to 8 ft
beam (2 to 2.5 m). Beam width is controlled by California
State laws restricting towed trailers to not more than 8 ft
or 2.5 m width. Some of the latest boats measure up to
21 ft (6.4 m). Experience has shown that 18 ft (5.5 m) is about
the maximum length that a two man crew can handle launch-
ing or beaching off a trailer on a sand beach.
The hulls are V-bottom design, very sharp forward and taper-
ing to a fairly shallow V at the transom. In proportion to their
length they have enormous freeboard and a very strong sheer
particularly toward the bow. Transom is flat with a slight
rake aft and the hull has extreme flare above the chine all the
way aft to the transom. No deck or whaledeck is used.
A very small 2J- to 3 hp outboard is carried when long-
lining and is used in "walking the line" after the longline set
is made and for emergency use. This engine is lashed in the
bilges and not kept on the stern when landing 'or going
out through the surf.
The hulls are built upside down on a jig and laminated
frames, stringers and keel are used. Sawn frames are not
liked as they are "too heavy and split out in the surf". No
projecting keel or shoe is used and a triple layer of fibreglass
is used to fair in the chines and for protection of the keel
strip. Chine batten is steam bent oak. Frames are widely
spaced (18 to 24 in, 460 to 610 mm) and stringers and chine
battens depended on planking is single sections of I in (9.5
mm) plywood for the bottom up to the chines and J in
(6.4 mm) or -ft- in (4.8 mm) for the sides. Stringer and rib
spacing is doubled the first 5 ft (1.5 mm) aft of the stem.
No flooring is used and bilges are open throughout the
boat to facilitate bailing. If an inboard engine is installed
(rare), it is in a watertight box with a hinged cover.
A finished hull is very strong and stiff for its weight and
considering their power and the beating received during
launching and in the surf it is well this is so, fig 26.
Surf boats— engine
With the exception of a few inboard/outboard drive or jet
pump propulsion installations, the vast majority of these
boats are powered by 50 to lOOhp outboards and by and
large it has proved the most efficient. Primary problems are
corrosion which is pretty well under control and the item of
a heavy mass located in the extreme stern of the boat which
is compensated for in the design of the boat.
The problem of swamping by waves coming aboard through
the low transom required by outboard installations has been
solved by the installation of, in effect, two transoms — the aft
or true transom is low and strongly braced and is the one on
which the engine is mounted, and the second is simply a
watertight bulkhead far enough forward to allow the engine
to tilt inboard if the lower end strikes bottom. The space in
between as mentioned being decked and used for fuel tanks.
Modern American outboard ignition systems are now
transistorized and geared and quite unaffected by moisture so
this is no longer a problem.
Without exception the engines are electric started as the
large size makes hand cranking impractical and if engine is
stopped in the surf it is much too time consuming to restart
by hand. Also the most favoured engine, an in line six
cylinder type uses no reverse gear but is stopped and cranked
backward to back down. Batteries are charged by an AC
alternator built in to the engine's flywheel and battery ignition
is used to fire the plugs as it is lighter and more reliable than
the old fashioned magneto systems as well as being easier to
seal against moisture.
Fuel consumption is still high by comparison to a four-
cycle engine of the same output but only slightly higher and
the overall dollar/hour cost is equal between engines for a
season's use. Repairs are much simpler on the two-cycle
engine and can be made without special tools or power
machinery. Most owners do their own repairs at home.
Cooling systems are positive pressure pump circulated
systems and work well in water with sand particles in suspen-
sion in it as the pump impellers are made of synthetic rubber
and will not wear nearly as rapidly as the old metal pump
gears.
Engine controls and steering station is slightly aft of amid-
ships usually fastened to the box on the starboard side
covering the gurdy drive engine. The boat is operated at all
[516]
times with the fisherman standing for better visibility and so
his legs can absorb the fierce pounding of the hull in the surf
or at high speed in the open water outside the surf line. This
same pounding poses a problem with the old style float
controlled carburation but modern engines use diaphragm
injection carburettors, and this trouble no longer exists.
Experiments with motor wells through the hull have been
made but the problems of excessive drag, sealing, motor
tilting and working space lost in the boat require too many
fancy solutions so they have been dropped without exception.
No inboard engine installations have been made for several
years, they are just too heavy and expensive to be com-
petitive.
The excessive power (to European eyes) installed in these
light hulls at first glance may seem wasteful but it is used
primarily for steering and to accelerate the boat while in
transit through the surf line. Sometimes only a few seconds
are available between crests in which the boat has to be
correctly positioned to meet the oncoming wave system, and
then this high power is well worth the cost and the absence
of skegs or keel and the high thrust of what amounts to an
active rudder gives them a fantastically quick response to the
helm.
The combination of this high speed, plus the mobility on the
trailer allows a tremendous area of coast line to be available
for fishing, so that if bad surf or some other condition
prevents longlinging in one area a large choice is still at hand
every day. The old slow displacement hull permanently
afloat in some harbour allowed no such choice. Again this
mobility allows the fisherman to dc all of his hull, gear and
engine work at his own home, where tools and working
space are at hand — no small advantage. In fact a surprisingly
large percentage of these fishing ventures are composed of
husband and wife teams. He fishes and the wife drives the
truck, and handles the beaching gear.
Suggested improvement of FAQ beach boat type BB-59
If local tradition is against the use of outboards McKinley
suggested that these boats be powered with rebuilt automotive
engines, not diesel, for the following reason :
• low first cost
• easier to keep in service
• faster throttle response
• light weight per hp
The only really good competition offered the outboard
engines for surf boat work is the following system:
A fairly small auto engine direct coupled to an axial flow
high volume pump discharging through an above water
swivelling nozzle in the stern. The water intake for the
pump being through a large gridded opening in the boat's
bottom alongside or straddling the keel— the so called "Jet
Boat".
The engine cooling system is the same as that originally
installed in the car the engine was removed from. That is to
say the automobile radiator, cooling fan, water pump and
plumbing are removed intact and reinstalled in the boat.
The engine is encased in an air tight box with an opening
at the forward end for the radiator and a larger air exhaust
trunk opening pointing upward at the aft end of the engine
box. This exhaust trunk has a raised coaming about 1 2 in
(30 cm) high and is fitted with deflector vanes to direct the
air flow straight up. The cooling fan is fitted with a shroud
between the radiator core and the fan and blades are usually
increased in pitch to increase the air flow or the fan itself is
replaced with one having a larger number of blades. Fresh
water or anti-freeze mixture is used as the engine coolant
liquid and coolant temperature controlled by a conventional
thermostat. Usual setting is 180°F (82°C).
The engine exhaust is directed through a conventional
automobile muffler mounted vertically in the centre of the
exhaust cooling air duct so that the muffler is cooled by the
air flow around it and the engine exhaust gas is blown well
clear of the interior of the boat by the same air flow.
US Coast Guard regulations require that the engine be
fitted with a back fire trap and drip pan on the carburettor
and that a bilge blower be used to vent air inside the engine
box before starting.
The propelling pump or "jet pump" is a manufactured
item that comes complete and ready to install as a unit
including coupling flange, steering and reversing gear for the
thrust nozzle and all fittings. The only modification found
required for working in shoal water is that some users have
had "stellite" leading edges bra/ed on the pump and stator
vanes to reduce abrasion when suspended sand is forced
through the pump in very shoal water when launching or
landing through the surf.
The most popular engines are six cylinder, 140 and 170
in3 (2.3 and 2.8 1), engines. No clutch is used between pump
and engine. Nor is an engine thrust bearing needed as thrust
bearings me fitted to the jet pump itself and no load is
transferred to the engine. The engine flywheel is removed and
a spline machined in the flywheel centre hole to mate with a
spline on a stub shaft fitted with a coupling flange. After
reinstalling the flywheel the engine is mounted in the boat
with the stub shaft inserted. Then the stub shaft and pump
shaft coupling flanges aligned and bolted and the engine
installation is complete. Engines are run with the boat out
of the water to warm them prior to launching and for adjust-
ments if required without any noticeable damage to the
pump unit. The engine starter does not object to the small
extra load of the pump rotor when engine is started with the
boat in the water.
Unfortunately the total cost of the entire propulsion plant
is higher than an outboard for the same service as the cost of
the propelling pump is quite high and the engine bearers, jet
pump mount and plumbing, the engine box and miscellaneous
labour total up to quite a lot.
Steering effect in water down to less than 1 ft (0.3 m) in
depth is very good and as the boat requires no skeg to
protect the prop the deadwood can be cut away to increase
turning speed and reduce draft both of which are very desir-
able in any beach boat.
Thrust output is a function of rpm and thrust build up
from idle to maximum power quite satisfactory. Reverse
thrust is poor being only 10 to 15 per cent of forward power
so the boat operator has to adjust to this. Fine speed control,
that is the ability to adjust speed by varying engine rpm is
quite good but requires familiarization if a person has only
conventionally propelled boat experience.
Fuel consumption is higher than a normal boat's but is
balanced by the far better shallow water ability of these units
for surf boat use.
A great virtue is that the installation can be serviced by any
competent auto mechanic and unlike the very limited life of
seawater-cooled engines this one is operating entirely in the
environment originally planned.
In areas where air temperature is higher than normal a so
called "heavy duty" radiator is required if prolonged high
power operation is planned. These radiators are stock items
from any American auto maker.
The engine/pump system has been very reliable and satis-
factory and only the high cost of the patented pump unit keep
them from displacing the outboards. Perhaps the Govern-
ments can reach an agreement with the patent owners for
[517]
Fig 25. Surf-going fishing boats in Southern California are
powered with strong out hoar (is for optimum manoeuvrability
in the surf. On shore they are easily launched and landed
with the help of modern boat trailers
local manufacture of the pumps and thus reduce the price for
the benefit of their fishermen.
McKinley suggested a design study along these lines and
some form of hire purchase plan with the fishermen.
Special method for tropical surf areas
McKinley also proposed an idea, which, at first glance, he
said, may sound foolish, but really has merit in that it is a de-
vice which will enable a single fisherman to obtain sufficient
fish each day to feed at least several other people, primarily in
warm water areas, where steep coral reefs or rocky shores
prevent the use of canoes or rafts from being launched from
the shore for more conventional fishing.
The idea is to use a slightly modified surf board or paddle
board of the kind now so popular as a sporting device, as a
small scale fishing platform. This idea was suggested by a
manufacturer of a popular surf board which is used on both
coasts of the USA, in Hawaii and Australia. The standard
tandem or two person board could be modified very easily
into a unit that could carry one person and at least 200 Ib
(100 kg) of load through any surf condition up to swells of
8 ft (2.4 m) high, and that the board alone would not weigh
more than 35 to 40 Ib (16 to 18 kg) ready to launch. Any
person of normal swimming ability could handle this board in
the surf with only a few hours of instruction, and a day or
so of solo practice.
The manufacturer's idea is to construct an open wood or
plastic tray on top of the board, the width of the board, and
about 4 in (10 cm) high by 4 to 5 ft (1.2 to 1.5 m) in length.
This tray is to be covered by a securely fastened net and used
to contain the fishing gear (say a longline set) on the outward
bound trip, and the gear and the catch on the return trip.
A rig, somewhat to the order of this, is used illegally by
poachers hunting abalone and lobsters. This was so successful
that howls of dismay from sport men's clubs and commercial
fishing interests succeeded in having them barred from normal
use.
The surfboard maker said that the best size is of the order of
12 ft LoaX28 in beamXS in depth (3.7X0.7X0.1 m), and
that made in his plant of a thick fibreglass shell stiffened with
a hardwood spine and with the voids filled with polyurethane
foam, they sell f.o.b. for £50 ($140) each in lots of a dozen-
service life about 8 to 10 years. A cheaper board can be made
of marine plywood but the angular shape is much harder to
handle in the surf, and it is not nearly as durable as the
moulded fibreglass unit, as well as being prone to leakage.
This "sharpshooting" board is not intended to be ridden
back through the surf as is the more familiar sport board, but
is paddled through by its rider in a prone position using his
Fig 26. The V-bottom pleasure boat type surf fishing boats
in Southern California use light weight transistorized echo-
sounders, voice radios and line haulers driven by a small
inboard engine. Surf negotiation is facilitated by the active
steering provided by the heavy out boards used
hands to propel and guide the board (although a skilled
surfer can ride them through moderate surf standing erect). The
"sharpshooter" or "sniper" poaching board is often fitted
with a glass bottomed well and rubber light screen, so that the
operator can lie prone on the board and while he hand
paddles the board along can look through the well and spot
abalone, lobsters or fish of a size worth spearing -- not sport-
ing but very effective and the poacher doesn't expend his
energy or in heat loss from his body into the colder water.
McKinley admitted that this might sound a most unlikely
way to fish but it will work and the investment is very small
which is very attractive, and it also allows serious fishing in
an area not open to more conventional systems, along the
coasts of, say, India, Africa and other tropical overpopulated
areas of the world. Most of all, the areas that lack harbours or
markets able to absorb large catches of fish, and areas where
road transport does not exist to distribute large fishing tonnage,
even if it were brought in by conventional fishing fleets.
Were some of the tropical governments to set up a factory
using cheap local labour to make these boards in standard
moulds, he believed that an acceptable one could be produced
for around £10 ($25)— a unit with cargo tray and water glass
built right into the board. This is very likely the most effective
fishing system per dollar that can be made but would only be
efficient in warm water fishing at the subsistence level, but is a
system that anyone, male or female, above the age of ten,
can master in a very short period of time and would be of
great assistance to family groups in backward coastal areas all
around the world within this temperature zone. Transporta-
tion of the board from home to beach presents no problems
as, due to its light weight and modest size, it can be hand
carried by a child.
Sharks here are often seen swimming in the midst of a
group of surfers but do not seem to be interested in the
boards as long as the rider keeps his arms and legs onboard,
but in the event of an aggressive interest by them the user
can retreat into the surf zone which the large sharks avoid.
Gulbrandsen (FAO): There are very few natural harbours
along the coast of West Africa and for centuries the fishermen
have been obliged to work from the surf-beaten beaches.
Future developments will probably favour bigger boats work-
ing from well-equipped harbours. However, breakwaters are
extremely expensive and the sand carried by the long shore
current clogs the entrance in a few years unless frequent
dredging is carried out. Both for economic and social reasons,
fishing from the beaches will continue to play an important
part for a long time to come.
[518]
fig 27. A beach boat using an outboard motor placed in a well
developed by FAO naval architect Gulbrandsen, ami built in Dahomey
The main weapon of the West African fisherman in his fight
against surf and sea is the Senegal or the Ghana type dug-out
canoe powered by paddles or by sail. These long, slender
craft are a beautiful blend of each country's wood resources,
skill and tradition, In recent years a great many have success-
fully been equipped with outboard motors. All attempts to
use inboard engines have failed. Several countries have also
attacked the problem of replacing the dug-out canoe with a
more modern boat, but no solution has yet been found. An
analysis of the problem shows that the requirements for a
beach boat are indeed difficult to fulfil:
• Low cost
• Strength combined with low weight
• Construction simple enough to be made by local
boatbuildcrs, preferably of materials available locally
• Positive steering when negotiating surf
In 1966 the Government of Dahomey asked FAO to assist
in developing suitable fishing boats. Based on Gulbrandsen's
experience, gained from beach landing tests with a 21 ft (6.4 m)
prototype fibreglass boat, built by FAO and previous FAO
work (Gurtner, I960), a new type of beach boat was designed
to use a special rope landing technique (Estlander, 1955).
Fig 29 shows schematically the rope landing system con-
sisting of a buoy anchored well outside the surf 7one and a
synthetic rope stretched between the buoy and the beach.
For the construction of the beach boat, new materials were
considered, but aluminium was found to be too costly and a
fibreglass construction would require an air-conditioned boat-
yard because of the extreme temperatures and humidity. The
final choice was marine plywood which is produced in
several African countries.
The prototype beach boat had the following characteristics:
Loa 23ft (7.1 m)
Beam max 6.9ft (2.1 m)
Hull weight 13001b (580kg)
Outboard motor 1 0 20 hp
Cost of hull £155 ($550)
Cost of engine £110 ($400)
Total investment £265
($950)
For a surf boat the outboard motor has several advantages
Fig 28. FAO Dahomey surf boat
coming in through the surf, utilizing a synthetic rope to assist steering and to dampen pitching. The boat uses
an outboard engine, to obtain as active steering as possible
[519]
It is light in weight, has optimum steering characteristics and
can be tilted when approaching the beach. The motor was
mounted in a well (fig 27) to get maximum protection against
breakers from aft.
The prototype was tested in beach landing (fig 28) together
with the rope landing system. Before launching the boat, the
rope was put through roller fairleads forward and aft. When
the boat was floated by an onrushing wave, the crew jumped
on board and hauled the boat through the first line of breakers
until there was sufficient depth of water to start the outboard
motor. This is a critical phase in the normal way of launching.
If the motor fails to start, the canoe is often thrown towards
the beach by the next breaker, resulting in capsizing, swamping
or a broken motor. By using the rope there was no difficulty
in keeping the bow against the waves until the engine was
started, since the boat could be hauled a good distance from
shore before starting the motor, the risk of having the pro-
peller touching the bottom was greatly reduced. Full speed was
given at the right moment in order to cross the next line of
the development of motor transport so will the canoe be in
operation for a very long time to come. Just as the bicycle is
a cheap form of transport which the low-income individual can
afford, so is the canoe a cheap platform from which to fish
and one which the individual fisherman can afford. Moreover,
the strong desire of the fishermen in developing countries for
independence and self-employment is met by the canoe.
Furthermore, the canoe fits into the techno-socio-economic
situation of many developing countries. For one thing, there
are many developing countries which will not be able to
build fishing harbours for larger craft for a very long time to
come, and even if such fishing harbours were built, it is likely
that a new set of fishermen would have to be trained at a
higher level and with a different concept to man the larger
craft.
To force the fishermen in many developing countries to
abandon their canoe is to drive them into unemployment.
Fishing is usually the principal field in which they are skilled
and even where other industries exist, the displaced fishermen
Buoy, buoyancy - 150 Kg
X
Surf zone
| 3/8 Nylon cord
400 kg weight
or anchors
Fig 29. In Fishing Boats of the World (1955), Estlander proposed the use of a rope when launching and landing a beach boat
breakers as fast as possible. On arrival at the buoy, the rope
was released from the fairleads and the boat could continue to
the fishing ground. Coming back, the rope was picked up, put
into the fairleads, and the skipper waited for the right wave to
"hang on". He tried to position the boat a little behind the
wave crest when it started to break. The boat was then carried
by the wave like a surf board towards the shore. If the boat
had been forward of the wave crest when it broke, it would have
been in great danger of being swamped or broached, but the
rope added much to security by counteracting the broaching.
The main targets in the design of this 23 ft (7.1 m) beach
boat, namely low cost and minimum weight have been reached.
These, coupled with the rope landing system, have resulted in
the risks of beach landing being much reduced and in addition
there is more space for gear and catch. The prototype has been
used for several months by fishermen in a village of Dahomey,
but it is still too early to make any definite conclusions. Only
time will tell whether the glued plywood construction can
withstand the stress of beach landing over a long period.
Author's reply
Thomas (FAO): Like Traung he disagreed with Zimmer that
the dugout canoes are something of the past and will soon
disappear. Just as the bicycle has not disappeared because of
would be unlikely to fit into these. They would not willingly
exchange their independence for unskilled jobs in which they
would become dependant.
Just as the mobility of the bicycle can be improved by
adapting an engine so the mobility of the canoe can be
improved by motorization.
The problem from the canoe fisherman's point of view is
largely a sociological one which many technicians involved
in large-scale fisheries do not appreciate. What possibly will
happen is that in developing countries which can afford to
build fishing harbours and provide facilities necessary for
large craft a stratification will develop in the fisheries. The
canoe fisherman will continue to operate his small craft and a
new set of fishermen will be trained to man larger craft.
In these initial stages the right thing to do is to undertake
such improvements as can be made to the small-craft without
seriously altering their behaviour or functional adaptability
and certainly one of the ways of doing this is by motorization.
In remarking that the dugout canoe means a lot of hard-
wood wasted, Zimmer had failed to take into account the
skill available in some countries. In many developing
countries in which dugout canoes are made and especially
those in which little interest has been taken in the fishing
industry, the builders know how to build dugout canoes
[520]
but not plank boats. Moreover, it is not certain that the
quantity of wood involved in making a dugout canoe could
serve better economic purposes when it is considered that for
the duration of the life of the canoe it is providing employ-
ment for the fishermen and crew and perhaps for vendors of
the fish.
New material in old design
Because of their knowledge of the sociological problem
involved in removing the conservative fishermen from his
traditional craft, private, commercial and engineering interests
in Jamaica manufacture from fibreglass a canoe which
resembles, behaves and has the functional adaptability similar
to the traditional dugout canoe. A fair number of these craft
have been acquired by fishermen.
Von Brandt in referring to very small boats and pieces of
wood used as raft stated that these methods have no influence
on the production of protein. He says that this can be done
by bigger gear only like large bottom trawls and purse-seines
which are not adaptable from indigenous craft. But there is
evidence to disprove the first part of his observations.
Heath pointed out that Zambia produces 35,000 tons ol
fish annually and that the craft used arc dugout canoes.
Gurtner also pointed out that in Senegal canoes account for
90 per cent of the annual fish catch amounting to 90,000 tons.
In 1959 the catch in Ghana was 35,439 tons of which canoes
produced 32,804 tons as against 2,635 tons produced by
motorized vessels. In Jamaica in 1962/63 canoes were
responsible for production of 15,000 tons. Motorization of
the Jamaican dugout canoe (together with gear training) was
responsible for the dramatic increase in fishermen's earnings.
In some instances canoes with an annual turnover of £600
($1,650) increased their income to £1,500 ($4,200) and more,
whilst in others fishermen's income rose from £2 ($6) a week
to £7 ($20) a week. The proof of the pudding is in the eating.
Von Brandt had also failed to take into account the
characteristics of the sea floor in certain areas. For example,
the sea floor over wide areas of the Caribbean are covered
with coral and rocks which forbid the use of bottom trawls
and in other areas the patchiness of shoals of pelagic fish
would make purse-seining a very doubtful gear economically.
Again, von Brandt has evidently misread the paper. He
believed it as advocating the mechanization of indigenous
small craft as a final step and as the best way for fishery
development whereas the paper advocated this as an initial
step towards improving the productivity of the small-boat
fishermen in developing countries.
NEWLY DESIGNED SMALL BOATS
Devara (India): Gurtner did a good job in bringing out a
paper about various boat development projects undertaken by
FAO experts in developing countries in Asia, Africa and
Latin America.
The cost of boats in India is comparatively low. The boat
development has progressed well in the last ten years in
Andhra Pradesh, India. During 1953 to 1954, Mr. Ziener,
an FAO naval architect, surveyed the existing craft and
selected two types of local craft for mechanization. The first
local craft, called Nava, was mechanized in 1955. In all, 44
navas were mechanized. As the manoeuvrability of these
navas is not satisfactory, mechanization was stopped and
well-designed boats were introduced. They were designed by
Ziener, Gurtner and the Central Institute for Fisheries
Technology (CIFT), Cochin and Devara and Sastry of the
Kakinada Boatyard.
From 1960 to now, more than 200 boats (including navas)
have been constructed and distributed. The performance and
results of these boats are very encouraging. One fisherman
who was given a mechanized nava, is now the proud owner
of a house worth £535 ($1,500) and three sailing boats with
full sets of nets worth another £720 ($2,000), after paying
back the subsidized cost of the boat. Another fisherman, who
was given a 25ft (7.6m) boat, now owns a house worth
£1,000 ($2,800), in addition to substantial savings in a bank
account, after paying back fully the subsidized cost of his
boat. Both of them are acquiring bigger boats now.
Originally, these fishermen conducted gillnet fishing, but
now they want to do trawling for demersal fish and prawn
and shrimps. There is a great demand for larger and larger
boats. So the tentative target for the fourth 5-year plan is:
Two 50 ft (15 m) boats; 34 40 ft (12 m) boats; 78 32 ft
(9.75 m) boats; 30 30 ft (9.1 m) boats.
It is also planned to establish a second boatyard and a
small steel shipyard. With this present encouraging result and
good response from fishermen, far better results should be
achieved.
This developing fishery has attracted a few non-fishermen
and they floated a firm with a capital of more than £360,000
($1,000,000). The boat development scheme not only im-
proved the economical condition of fishermen, but also
provided employment for more than 350 workers, mechanics
and administrative staff.
Trend in Japan
Takagi (Japan): Gurtner's paper is very much appreciated
and he is to be congratulated on his great activities in fishing
boat design.
The near-future trend of small fishing boat building in
lapan is as follows:
• Small wooden boat building will slow down because
of lack of timber and skilled labourers
• To recover the above situation, research and develop-
ment of FRP fishing boats under a special research
committee is under way
• Recently, many small steel fishing boats under 50 ft
(15m) are being built. The minimum length of steel
fishing boats may be 32ft (10m) on the standard
scantlings of steel fishing boat construction rules
Kojima (Japan): Generally speaking, Yokoyama's paper
(Part II) highlights more intensively from a scientific point of
view the small fishing vessels in Japan, which are great in
number and have been used for a long period, rather than
examining only the problems of their resistance, propulsive
efficiency and seakindliness.
Good preparatory work
Rawlings (UK): Gurtner suggested to determine the exact
power being developed by the engine with the help of a
torsion meter in the band of horsepowers considered; but it
is doubtful whether consistent results would be obtained.
Large torsion meters can produce an inconsistent pattern
down the running range; smaller ones would probably be
much less consistent. A more reliable and much simpler
method is to calibrate the engine fuel pump against dynamo-
meter loads, mainly to obtain reliable information against
specific individual performance tests; adoption as a standard
feature would not be encouraged however.
Thomas', Gurtner's, Rasmussen's and Brandlmayr's
papers deal with widely differing types of small craft within
comparatively narrow dimensional extremes, but it is most
significant that they all have at least one thing in common,
and that is the lack of truly factual and fundamental informa-
tion even of a general nature, on which to work in the
beginning and subsequently of performance in service under
the widely varying operating conditions to be expected.
[521]
It is not the intent of this discussion to suggest recommended
values for GM and freeboard; however, some suggestions
can be found in two papers presented at this meeting; one by
Traung, Doust and Hayes page 139, the other by Gueroult
page 112. Where the proper parameters have been established,
a curve such as fig 30 can be provided to the personnel of a
fishing vessel to guide them in the matter of stability, any
period of roll to the right of the curve, for a given freeboard
estimated when among waves), indicating insufficient stability.
Authors9 reply
Gurtner (FAO): There is no standard answer to Heath's
problem. On-the-spot investigations by qualified technical
personnel are necessary before an attempt is made to give
recommendations regarding boat development.
Rawlings* suggestions are valuable and one must certainly
look forward to the day when all engines delivered by his
firm are fitted with calibrated injection pumps and are issued
with full instructions on how to measure power delivered.
As Townsend stated, a wealth of information on the
problem of fishing vessel stability was indeed presented in
1963 in Gdansk, Poland. Unfortunately, this material could
not be published due to lack of funds, and in view of its
availability to a very few people only, no reference was made
in the paper to data contained in this material. International
co-operation was, however, continuing in this field, and the
problem of finding and proposing for adoption a suitable
criterion or a series of criteria for fishing vessel stability was
being dealt with by a special IMCO/FAO committee as
outlined by Nadeinski, page 182, and it was hoped that the
findings of this committee would be published for general
use in the near future.
He was sorry to have to disagree with Sinclair and Tyrrell
regarding the effect of low angle of entrance. FAO experience
to date had shown clearly that low angle of entrance need
not be detrimental to good seakeeping qualities. On Tyrrell's
remarks concerning the construction of the boats shown he
felt that local traditions and preferences would be extremely
difficult to overcome and the ultimate in modern construction
practices could only be considered when more experienced
carpenters were available. In the absence of these he con-
sidered it safer to rely on scantlings that were perhaps a trifle
on the heavy side.
ARCTIC FISHING VESSELS
Zimmer (Norway): Rasmussen says that the hull must be
protected from ice by galvanized sheet iron. A tarred felt
between the plating and the wood makes for added protection.
What thickness of plating does Rasmussen propose? The
heating of ships in Arctic climatic conditions is mentioned.
By freshwater cooling the engine and thcrmostatic control,
the cooling water could provide reasonable heating if lead to
radiators when the ship is underway. When the engine is idle,
an electric dynamo could be used to provide extra heat
electrically.
Gurtner's very substantial and fine piece of work is extreme-
ly useful and interesting. The stability problem is well treated
and he gives important information of period of roll. The
main difficulty in the stability problem is overloading. In a
wooden boat when loading fish on deck up to the coamings
freeboard then gets almost nil and the bulky wooden bulwarks
help to maintain stability. However, this is not the case in
steel vessels.
?an den Bosch (Netherlands): Emphasized the importance
of not judging stability alone by the initial stability. Zimmer
had mentioned that fishermen tend to load the vessel up to
the coaming so that freeboard becomes extinct. For a small
trawler, the range of stability in the condition quoted by
Zimmer must indeed have been so large that the vessel was
virtually uncapsizable, and the buoyancy of the wooden
bulwarks cannot have done much.
Special Danish designs
Christensen (Denmark): Thanked Rasmussen for an excellent
paper on Arctic fishing boats and their development. The
Danish Royal Trade Department intends to build larger
fishing vessels for Greenland and in 1965 they have finished
the construction of two 82 ft (25 m) wooden boats — one
95 ft (29 m) steel boat is still under construction. One problem
encountered is how to introduce a higher standard of living
in the Northern part of Greenland. In this area, there are
special problems insofar as processing which has been the
same for centuries. Most of the seas are covered with ice and
only for a few months in the summer is it possible to use a boat.
They had therefore been trying to find a small boat which
could do this fishing just a few months each year.
The boats have to be light, strong and inexpensive. In 1965
24 ft (7.3 m) boats have been built. This boat type has the
accommodation forward. It is still too early to comment on
the results, but is is already indicated that this type of boat is
excellent. On the other hand, the construction is not good
enough and therefore a new type of construction, maybe
laminate or plastic might be better. Of the particular design
problems for fishing vessels in Greenland, one of the most
important is to construct a boat having the biggest flexibility
for different fishing methods. H is very difficult to have a
multi-purpose boat which is excellent for all fishing techniques.
It is necessary to select the most important fishing methods
used, i.e. longlining, handlining, gillnetting, pelagic netting,
bottom trawl and seine netting.
Referring to the Norwegian type vessels, the engine is
semi-dicsel of simple construction and the boats fish in threes,
one equipped with an echo sounder so as to locate the fish
for all the boats. It is very difficult in Greenland to develop
the fishing industry based on small vessels and therefore it is
essential to have bigger boats of over 60 ft (18 m) for use in
the open sea. This is the present stage of development of the
fishing boats in Greenland, but the small vessels will still be
able to fish along the North and South coasts of Greenland.
Methods in Newfoundland and Greenland
Harvey (Canada) : Newfoundland has severe winter conditions
and the boats encounter heavy ice. To protect the outer hull
planking, a sheathing of greenheart is laycd over the outer
planking with tar paper between the wood. The fastening of
galvanized iron must be kept clear of caulking seams and must
be short enough not to go through the planking. Steel re-
inforcing plates are placed at the bow and around the stem-
bar. Also around the skeg and under the stern. These plates
are fastened with special screw nails and care should be taken
that they do not interfere with seams and pierce through
planking.
Danielsen (Switzerland) : The connection with the development
of fishing vessels of Greenland can be taken as a very good
example of the importance of the interrelationship between
fishing, processing and marketing. Characteristic for these
small boats in all the North Atlantic area is the seasonal
variations in the catch. For the boats described by Rasmussen
under 20 GT, the catching curve will be as fig 31 for the
Greenland waters.
With an investment on shore of about £133 ($370)/tons
raw materials processed during the year, one will very soon
realize the economical consequences of not using the factory
[524]
J FMAMJ J ASOND
Months of year
Fig 31 'Relation of catch and month in Greenland
for more than four to five months during the summer time.
This would be like a shipyard running under these conditions
with a degree of utilization of 25 per cent. Further problems
arise in the marketing of a product with a limited keeping
quality and which is processed during a very short period
of the year.
This is a very important point in all decision-making
concerning the development of the fishing industry, especially
in developing countries. A very good example should be
Greenland. The explanation of the Jack of success in some
countries is to be found in the lack of understanding of the
suboptimization of all functions from raw material procure-
ment through processing to marketing. Boat operators and
naval architects must show a better understanding of this
problem in the future.
Training of fishermen in Hong Kong
Orchard (Hong Kong): The main objectives of the Fisheries
Development and Extension Division in Hong Kong have
been (1) the initial mechanization of indigenous craft coupled
with the training of fishermen, (2) the gradual improvement
of boats generally, including the training of boat builders,
(3) and the introduction of better fishing methods, particularly
the introduction of single-boat otter trawling to replace the
two-boat trawling traditionally carried out.
One of the most important original steps— taken on the
advice of Traung— was the local recruitment in 1956 of a
qualified and experienced craft technician. This officer
proved very worthy but left the post on promotion. In his
place came Choi Kwok-leung, who is now senior Craft
Technician. There is in Hong Kong an establishment of
altogether six craft technicians: that is two boat designers
backed up with a draughtsman; one mechanical and one
electrical engineer; plus a master shipwright, and these
officers are all fully committed on useful work. In addition
to this staff, the Division has a master fisherman who has
together with Choi been so largely responsible for the
acceptance and success of the work.
Following news concerning the success of a 40ft (12m)
modern shrimp trawler, a "clear stern" modified junk-type
shrimp beam trawler of 64 ft (1 9.5 m) was built by a graduate
from one of the training courses run by the master ship-
wright of the Division. This particular boat costs HK$58,000
(£3,637, US$10,000). Trials 9J knots. Bollard pull 5,200 Ib
(2,360kg), GM lightship condition 5.43ft (1.66m). The
boat is now fishing successfully, local fishermen are accustomed
to a stiff ship, and now a 66 footer (20 m) has been designed.
There is the Government loan system of just under HK
$200,000 (£12,500, US$35,000). Fishermen given loans
should follow the instruction of the Government technical
officers, the boat should be built to the government design
and under its guidance and supervision. This marks the
beginning of buildng to detailed plans, and to specifications
of a higher order than ever in the past. In previous years,
the Government has had to "retail" development and so
gradually earn the confidence of the fishermen, but now hopes
to be able to put across the development work on a "whole-
sale" basis.
Retvig (Denmark): Just a brief remark to Rasmussen as
regards the government's point of view to approving designs
and dimensions, which, of course, is their duty. Denmark
will not keep technical achievements (so far as they are
obtained) a secret. On the contrary, the Danish authorities
are always ready to discuss problems arising from practising
the rules. The reason is, of course, that the administration
has the highest interest in the rules being applied in the right
way (not only for the benefit of the administration, but what
is much more important, to the satisfaction of the ship-
builder and the fisherman) and in order to collect experience
from practice, so that it is able to amend the rules prevailing
today so that they work as sensibly as possible.
Author's reply
Rasmussen (Denmark): Agreed with Christcnsen and
Danielsen that expensive filleting plants cannot be fed by
small boats operating only during a short season. If all the
functions from marketing to processing had been well ex-
plained to the naval architect, results would have been better.
There is no fishing in winter in Greenland, but small boats
play a role in seal- and bird-hunting. The 20 GT boat-type
proposed in Rasmusscn's paper could carry kayaks on deck
to travel to and from the hunting grounds.
In reply to Zimmer, tarred felt is provided under the sheeting
for ice protection. Sheet thicknesses are given in the paper.
Use of freshwater cooling with the heated water to circulate
to radiators for heating the boat is a good system, but in
harbour, when the engine is not running, there will be no
heating and that is why one must have a small oil healer for
radiators in port. Use of the oil heater could also heat the
engine before starting in cold weather.
To Harvey, Rasmussen said that greenheart was not avail-
able and that is why there was no mention of it in the paper.
To Retvig, no reference had been made to the Danish
Ship Inspection Service when it was stated that governments
held back information. This office has given all possible
assistance.
HIGH-SPEED FISHING CRAFT
MacLcar (USA): On the US East Coast, about four years
ago, a high-speed boat was used for lobstering. She was
designed and built to be able to go further off-shore than
existing vessels. The boat was about 40 ft (12 m) overall and
was expected to cruise at 21 to 28 knots. She had an open
transom to facilitate hauling lobster pots. However, no other
such boats have apparently been ordered.
A fast 36ft (11 m) boat was designed, which is almost
identical to Brandlmayr's design. One hundred and fifty of
these boats have been built, with a wide range of engine
horsepower and their performance is similar to Brandlmayr's
graph. One boat was fitted with two diesels of 1,015 hp
together for off-shore sport racing and this permits extending
the performance curve.
In fig 32 the average boats operate in the range (A), the
fast boats were in range (B) of the curve. The boat, which
was used exclusively for racing, had a speed of 52 knots and
cost £18,000 ($50,000), fitted with two engines and spares
worth £11,000 ($30,000). These engines were estimated to
[525]
hp
price of boot $50000
52 V(knots)
Fig 32. Speed-power curve
give a service life of 22 hours per engine, and indicate how
expensive it is to go fast on the water.
High-speed inshore day boats are amply seaworthy, and it
is only economics that limit the speed of fishing boats.
In connection with canoes, MacLear once owned a gaumier
or canoe used in Martinique and St Lucia, BW1. It costs £6
($17) and could be amortized in one good day. This 100 per
cent return on investment in one day, while it seems a
miraculous business opportunity, is not so good when one
considers the rest of the fishing season in St Lucia. When
fishing for red snapper two or three men row and sail their
gaumier at a total of 20 to 30 miles in one day to fish with
hand lines in 600ft (180m). On a bad day, their catch may
only number 20 red snappers, and the return per man is very
poor.
Interesting speed problems
Borgenstam (Sweden): In the design of the fast gillnetter
described by Brandlmayr, there are some interesting hydro-
dynamic problems involved which might need some clari-
fying. The speed-range of 10 to 20 knots is a very critical one.
It represents a transition region between displacement and
planing conditions, where neither of the hull forms is ideal.
Unfortunately there is a tendency also for modern pleasure
craft to come right into this speed bracket, which should be
avoided if at all possible.
Brandlmayr remarked there have been great variations in
reported and observed performance. The explanation for
this is the form of the power curve of a planing craft. It
intersects the curve of available power at a very small angle.
Even small variation in resistance or engine power will thus
cause the intersection point to move considerably, so that
the top speed is much more influenced than is the case with
a displacement craft. This fact makes it desirable to use an
engine with a very full torque curve, which is the case with
the big US car engines. Diesels are usually not only too heavy
but they also often have a too flat torque curve to go well
with a planing or semiplaning hull.
In a planing craft it is important to prevent unnecessary
increase of the weight, apart from that caused by the useful
fish load. The designer must keep a careful control over the
weight not only during the design but also during the con-
struction and operation.
Lee (UK): The hull form, longitudinal position of centre of
gravity, and the position and type of spray chine, are probably
ideal for a lightly loaded boat operating over the speed range
stated in smooth water conditions, but fuller sections forward
and a steeper rise of floor aft would improve seaworthiness,
as Brandlmayr suggested.
It should be recognized that high-speed craft involve more
maintenance. The engine must be kept at peak performance
and the bottom kept clean. A light wooden hull construction
fails with repeated pounding and requires frequent attention.
A light metal construction involves many problems arising
from dissimilar metals, moreover special welding equipment
is required for building such craft.
The high durability of the plywood boat sheathed with
glass reinforced plastic, shown in fig 4 of Brandlmayr's paper
is of great interest and some information about the resin
and reinforcement and method of application would be
appreciated.
High cost of extra profits?
Gillmer (USA): Undoubtedly the advantages of using high-
speed fishing craft are most attractive and enticing and it
takes little imagination to visualize the ensuing increased
profits caused by more rapid transportation of the catch to
the market, the more numerous trips possible to and from the
fishing grounds, the possible elimination of refrigeration, etc.
It would seem, however, that these bright and beckoning
advantages must have been thought of often in the past and
had there been no engineering obstacles, would have become
at this time more of a generality.
Brandlmayr, in his discussion under economics, included in
his statement some surprising claims in a comparison of
displacement boats versus planing boats, in terms of operating
fuel consumption. The inference here would appear to be
that planing hulls arc 50 per cent more economical than
displacement hulls. There seems to be no statistical data
or descriptions of test comparisons, hull forms and weights
involved, etc., in the paper to substantiate such claims and it
is fell that if such exists, they would have been included in
the paper.
Generalization on such unsupported claims can lead to
false conclusions. It would have been far more desirable had
Brandlmayr approached this most interesting area of com-
parison more objectively. Resistance or power curves in terms
of specific resistance or specific power (R/A or P/A) plotted
against speed might have been more revealing for these hull
types. It would have perhaps thrown more light on the
ability (or lack of it) of light planing hulls to carry a pay load
efficiently.
McNeely (USA): In many countries the cost of fuel would
prohibit the use of high-speed fishing craft. As Brandlmayr
pointed out, high-speed craft may be used in only a limited
part of the world's fisheries, such as where (1 ) the value of the
fish is exceptionally high, (2) the day fishery exists, and
(3) the weight of the catch is relatively small. High speed
craft would probably not be suited to trolling which is usually
carried on at greatly reduced engine power and speed.
Sinclair (UK): One other point on Brandlmayr's paper.
When considering high speed for fishing vessels, it should be
remembered that these are generally not good seaboats and
in areas where bad weather is frequent they may be harbour-
locked much more frequently than their orthodox com-
petitors.
Takehana (Japan): In Japan, some fishermen are planning to
change from traditional pole and line fishing to tow-line
fishing. So they require a lighter and higher speed boat.
Japanese traditional small wooden fishing boats are so heavy
that their speed is limited to under 8 to 10 knots. They are
planning to change hull to steel, but it is difficult to make a
steel boat under 10GT lighter than wood, due to corrosion
and the welding technique of thin plates. Fibreglass reinforced
plastics may be better suited to these high-speed boats than
steel, and having regard to the boatyard facilities, conversion
from traditional wood to moulded fibreglass would be easier
[526]
than to steel. So Takehana was going to recommend them to
make fibreglass boats. The higher initial cost of this material
may be covered by higher speed and higher fishing ability.
Author's reply
Brandlmayr (Canada): Agreed with Borgenstam's excellent
explanation of performance characteristics and wished he
had done as well. Many fast boats are disappointing and over-
rated in this marginal range. Speed predictions usually
backed with many pages of calculations often lack the under-
standing of the principles.
In reply to Sinclair on seaworthiness, these boats are
generally fishing in protected waters, but they make a sur-
prising speed at sea especially in long swells. Seaworthiness
with these boats is very much a matter of boat-handling. They
are most difficult to handle in short seas and better in long
swells. A good seaman with experience can run between the
swells and run down the slopes. There is less roll and the
ability to accelerate away from following seas is useful to an
experienced man.
On Lee's question about covering plywood with FRP,
conditions must be dry and polyester resin is used with
surfacing mat applied first and then covered with woven
roving.
Gillmer's questions were to some extent answered in the
paper but they are questions worth repeating. The engineering
obstacles to high-speed fishing craft are the need for light,
powerful engines and sophisticated structures. In recent years
a few builders have overcome these obstacles to a limited
extent, but most have failed thuugh insufficient power,
overweight, lack of strength or poor hull form. These obstacles
continue to be formidable. Concerning fuel consumption:
reports were gathered from fishermen using boats on their
usual passages. The displacement hull forms were believed to
be much heavier and, of course, were designed for carrying
capacity. On significant runs to fishing grounds they tended
to be driven at nearly full throttle using engines of about the
same power as the light planing types. Curves of specific
resistance or specific power plotted against speed would be
of interest but while operational data on distance, time and
fuel consumed were available, weight figures were not. It is
somewhat like comparing the fuel consumption of a dump
truck with that of a passenger automobile when both are
travelling empty. Planing hulls are not efficient pay load
carriers unless the pay load has an hourly cost as is the case
of highly-paid personnel.
DEVELOPABLE SURFACES
Michelsen (USA): It is amazing that it should take so long
to develop such a simple, straightforward method of generating
developable hull surfaces. Is it that one by nature tends to
make things more difficult than they really are? To anyone
who has tried to use the cone-cylinder method of hull form
design, this must certainly never be the case, more especially
so after reading Kilgore's paper. He is to be congratulated
on having the ability to challenge established design pro-
cedures and for presenting a simple underlying principle of
developable surfaces in a lucid and concise manner. No more
can now be said on this subject as related to hull design.
Fig 33. Rotation of co-ordinate system to explain Kilgore's method
[527]
Kilgorc stated that proof of existence is very involved, but
perhaps a rotation of co-ordinate system will provide what
is needed. Graphically this is shown in fig 33 of this dis-
cussion. Assume two segments of space curves A and B,
given by their top and front views; the question is then asked,
does there exist a plane which is tangent to curves A and B
at points located between end points of segments? To furnish
the answer, a tangent is drawn to curve A at an arbitrary point
A3. By using two successive auxiliary views, a point view of
this tangent is obtained. Obviously all planes containing the
tangent will appear as an edge in this second auxiliary view.
Therefore, if a tangent plane exists, that is tangent to curve A
at point A3, it will be possible to construct a line from the
point view of the tangent (in the second auxiliary view) which
will also be tangent to some point on the curve B. In fig 33
it is clear that curve B does not satisfy this requirement.
Curve C, on the other hand, does meet the criterion stated
above and the line A3C3 is a tangent element.
Uniqueness follows directly from elementary theorem of
geometry regarding the uniqueness of tangents to a plane
curve from a point not on the curve. To use an old, well-used
phrase: *The proof of the pudding is in the eating." He hoped
therefore, that boatbuilders will freely help themselves to
what has been served. He was thoroughly convinced that
anybody who uses Kilgore's method of developable hull
surface design will find the savings in labour cost to be of
great significance, both in the drawing room and in the shop.
The impact of this paper on future boatbuilding practices
should not be underestimated.
Allen (USA): As a builder of large numbers of steel and
aluminium small boats, he expanded on practical considera-
tions for the construction of fair hull forms.
The general problem with light gauge steel hull construction
is to obtain fairness. After establishing the shear and chine
lines by a developed surface technique, it is necessary to
allow considerable deviation in the mid-panels for expansion
during seam and butt welding or rather the contraction of
the periphery of the plates.
For vessels of 33 ft (10 m) length, a jig with no frames is
used. Leveau's fig 4 to 6 show a boat on the jig, fig 5 a hull
with no frames removed from the jig, fig 6 internal structure
installed at a later stage.
In vessels of 33 to 85 ft (10 to 25 m) with plating of J in
(5.35 mm) thickness, the following guides arc used :
• Minimum number of transverse frames to establish
hull shape
• Flexible longitudinal frame structure to which the
plating is attached
• Welding sequence which permits pressure to be applied
to the mid-panels from the inside of the hull to expand
the hull form rather than to restrain the plating to the
transverse frame shape
Real service rendered
Benford (USA): Kilgore has done the industry a real service
in presenting this exposition of the design of developable
surfaces. Beforehand, Benford had always assumed that
developable surfaces required endless trial-and-error with
families of cylinders and cones. There is now a better set of
tools for this task. The result is that the naval architect can
design a cheaper hull in less time than before.
Kilgore's comments on the application of straight-line
frames is worth noting. However, canted frames throughout a
vessel will create intersection problems at bulkheads, hatch-
side girders, etc. But, of course, reluctance comes from the
tradition that the frame location was the shipbuilder's primary
index for fore and aft location. Kilgore is certainly funda-
mentally right in recommending straight canted frames and
that the disadvantages will be little more than distractions
to an imaginative designer-builder.
How important are the savings inherent in developable
hull forms? If the structural hull contributes one-third to the
total cost of the fisherman's boat and gear, and if the hull cost
can be reduced by 25 per cent, then there will be about an
8 per cent saving in invested cost. A boat built in the older
way might cost £180,000 ($500,000). An 8 per cent reduction
would be £14,000 ($40,000). To many fishermen this might
be the difference between success and failure in financing a
new boat. Furthermore, few people realize the great influence
of first cost on profitability of an operation. Considering the
risks, both physical and financial, an investor in a commercial
fishing boat should be satisfied with nothing less than a
12 per cent rate of return. If a 20-year life is assumed, a
12 per cent interest rate and a 48 per cent corporate profits
tax, the annual cost of capital recovery comes to 21 per cent
of the investment. Thus the £14,000 ($40,000) in reduction
of building costs is equivalent to a saving in operating costs
of £3,000 ($8,400) per year. This would assuredly be welcome
to any fisherman and illustrates the wisdom of careful
professional design.
For Kilgore's next paper on this subject is suggested an
explanation of how to design developable surfaces within
the restraints imposed by the minimum bending radii of
different thicknesses of plywood.
Hull shape problem
Colvin (USA): While there is much merit in Kilgore's desire
for lighter structures and lower costs, one must still accept
the fact that planked hulls will continue to be built for many
years to come, and that in certain areas the advantages of a
planked hull often outweigh the disadvantages of not being
able to predict the strength of testable sheet material. On
paper, it is often more simple to convert from the heavier
structure to a lighter and usually better structure, than it is
in practice; for, as the weight of the material decreases, the
skill of the builder increases, and with it come a host of new
methods, all of which must be learned before he can success-
fully construct the lighter hulls.
There is no question at all of the ability of a designer to
design the hard chine or V-bottom hull that has equal or
only slightly higher resistance than an equally well-prepared
design of a round-bottom hull. Tf the material for the shell
of the hull is to be of marine plywood, then there is no question
that a developable surface must be prepared, and that the
designer must not in any case sacrifice any more than is
absolutely necessary to come within the preconceived ideal
shape that he is trying to obtain, for, on a heavily warped
surface, the joining of small pieces of wood and their butt
blocks or liners would increase the labour manifold over a
developable surface. However, when the material of the shell
becomes steel, then there is no conceivable excuse to adhere
directly or indirectly to a developable surface.
It had been Colvin's practice in the last decade to use the
V-bottom hull in the midbody and afterbody; but, in the
forebody he never hesitated to depart from the V-bottom hull
to gain a finer entrance or, at least, an entrance that is
compatible with the speed of the vessel and its seakeeping
characteristics. By actual comparison, the additional time
involved in framing up a conical surface in steel equals out
the additional time spent in cutting a plate to a smaller
width to adhere to a non-developed surface. Many times
that the stressing of developable surfaces by designers with
the view of time-saving in the plating of hulls tends to blind
them to the fact that framing becomes more difficult and it
can, in many instances, be more advantageous to make a
[528]
radical departure rather than try to obtain simplicity in shell
application.
From a draughtsman's viewpoint, the fundamentals of
developing a surface can be rather easily understood; how-
ever, there are a number of methods where the developable
surface is external to the hull where the ambiguous point is
found by trial and error. Rabl (1959) outlined a method of
multi-conic development where the development of the sur-
faces was within the hull boundary limits and external points
were not necessary to find or to think about. Also, the method
that he used gave direct means of determining expanded
shapes. The method outlined by Kilgore approaches this in
its simplicity and gives a reliable development. The final
development indicates a great deal of flam added to the
underbody forward which, in some instances, could give a
bow that was too full to utilize without either an increase in
horsepower or an increase in displacement. The altering of
the displacement prismatic coefficient and longitudinal centre
of buoyancy can be acceptable in smaller craft, but must be
corrected in larger vessels.
Colvin is in full agreement with Kilgore that there is
enough plasticity in most materials to accommodate slight
deformation, which makes it advantageous from a building
point of view, to dispense with developing frames when they
approach a curvature of less than one-fortieth the span.
Again on paper, there is absolutely no reason why the frames
must be square to perpendicular to some other main portion
of the hull.
Other technical points
It is true that welding has ended the necessity lor right
angles and square framing, but only from a strength point of
view. From a builder's point of view, unless a very compli-
cated jig were set up, it would be unduly expensive and
difficult to set up a hull that has lost all of its reference points.
In very full hulls, it is still necessary to use cant frames as it is
in the round stern, cruiser stern and fantail types of hull.
The attachment of bulkheads, the building-in of fuel tanks,
fish pens, etc., still indicate the desirability for framing that
is square to the centreline. The combined longitudinal-
transverse framing system on all forms of hulls is preferred
to a straight transverse system, especially in the forebodies.
With sufficient combined transverse and longitudinal framing,
a very light shell can be applied, giving a vast reduction in
overall weight of the vessel without a reduction in longitudinal,
transverse or panel strength.
The fallacy of believing that fully-developed hulls reduce
the need for high skill in metalworking is common; however,
when given just a welder and a shipwright who are not
masters of their art, some shocking results will occur to the
best plans prepared. The skill of the designer many times is
lost through poor builders, and many poor designs are
improved by good builders. Developable surfaces may lessen
the need for heavy tools and furnaces in large vessel construc-
tion, but in sizes to 75 ft (23 m) whether V-bottom or round-
bottom, furnaces are not a requirement and that the shell
framing on most vessels up to and including 50ft (15m)
can be cold-worked by hammering. As an example, on a
45 ft (14 m) deck length, 22 ton displacement, round-bottom
hull, three men can loft, make patterns and the frames, and
have the frames set up with transverse frames on 17 in
(430 mm) centres in 10 working days.
McNeely (USA): Kilgore's paper makes a lot of sense in its
description of the use of differential geometry to develop
contours of a hull consistent with good architectural practices,
but predictable in shape for precision assembly of pre-cut
and shaped sections. However, arc not most steel vessels
constructed in this manner?
Verweij (Netherlands): This is a very useful method, since it
can be applied to whatever construction material is used for
the actual boats. Especially if fibreglass is chosen and only
a very small number of boats have to be built, it will result in
a great saving of cost for the mould if the hull consists of
developable surfaces. The mould cost for building two fibre-
glass landing craft of 36 ft (1 1 m) length was 7.5 per cent of
the value of the finished boats.
yr Boor.
face poor
Fig 34. Body plan of a British steel chine boat
[529]
Double chine vessels
Lee (UK): Design based on developable surfaces sometimes
involves difficulty in balancing the FB and FG and it is
desirable to have ample margin in the distribution of the
main weights and to allow for ballasting. While the statement
in Kilgore's paper that the backbone and ribs are best
forgotten, may apply to small smooth-water craft, they are
essential for all other types. The single chine forms illustrated
are likely to suffer heavy pounding in a seaway and the flare
of the forward sections do not appear to be sufficient for
fishing in open seas.
It may be of interest to note that British 75 ft (23 m)
motor fishing vessels of wooden construction are being re-
placed by double chine vessels of steel construction; the
body plan and shell profile are shown in fig 34 and 35. All
the plates and frames are fitted without fairing, thus reducing
the amount of skilled labour required. The frames forward
are rounded slightly to take the curve of the plate where it is
twisted in the plate rolls; rounding of the frame is shown in
Kilgore's fig 5. With this form pounding on the flat sections
aft has necessitated the fitting of longitudinal stifTeners
components, care being taken to keep these as close
as possible to those established in the beginning (by
use of cones and cylinders)
• Adjustment of the form so obtained in order to adhere
as closely as possible to the original features. Hulls
have longitudinal framing in welded steel
To save time and labour, plating joints are arranged in such
a way as to:
(1) Make the best use of whole rolled sheets
(2) Keep down waste
(3) Reduce the number and length of joints
Faulting (USA): Kilgore's paper presented an interesting
example of the application of rather sophisticated mathe-
matical reasoning to the solution of a real and apparently
simple engineering problem. With the results presented so
succinctly here, the designer of craft of developable form is
freed of his most serious handicap, i.e. the difficulty of
producing a hull with predetermined properties, and is
granted nearly the same control over the geometry of the
hull he produces as the designer of a moulded form. Further,
Fig 35. Shell profile of a British steel chine boat
(intercostal) full welded, and full welding (in place of inter-
mittent welding) to floors.
Toullec (France): People in France are watching with great
interest the construction currently proceeding there on a
series of small aluminium boats where the lines and the method
of drawing are similar to those advocated by Kilgore. It is
not suggested that the French have developed the method
before Kilgore, but just that they entirely share his view.
French owner pleased
Foussat (France): In 1962 an overseas owner, who had no
preconceived ideas against developable hulls, ordered from
Foussat's firm a large 66ft (20m) 300-hp steel launch,
constructed on Kilgore's principles. He was so pleased with
its sea behaviour that he ordered a bigger one. The procedure
in designing the hull is as follows:
• Drawing of approximate form with straight-line
sections to have the desired centre of buoyancy,
volume and underwater hull form coefficients
• Translation of this form into developable surface
considering the trial and error nature of previous methods of
developable hull design, this method presented should lead
to significant saving in the naval architect's time.
Faulting did not fully agree with Kilgore's statement
concerning the relative resistance of round-bottom versus
chine hull forms. In particular, at the higher speeds which
are often characteristic of small craft, the chine hull often
shows a definite superiority in resistance. In a head seaway,
perhaps the average moulded hull form may have an ad-
vantage, but the greater damping in roll of the chine hull is
likewise an advantage in beam seas. In any case, by the use
of multiple chines, a developable hull form can be produced
which will approximate, as closely as necessary, the hydro-
dynamic characteristics of a given moulded hull. For this
purpose, double chines will probably be adequate in any
real case.
Author's reply
Kilgore (USA): In regard to the proof of uniqueness,
attention should be called to the principle that the cross
product of unit vectors not orthogonal results in a scalar
[530]
coefficient less than unity. Kilgore omitted to show such a
coefficient in the proof, but this does not affect the general
truth of the theorem.
Kilgore replied with reluctance to some contributors who
have defended methods of generating approximately develop-
able surfaces. He said that he should not care what fallacious
notions anyone might choose to entertain, but on the other
hand he felt an obligation to the large number of people,
not expected to know any better, who waste their labour and
money in following procedures they have read in published
papers. For the benefit of these people, the distinction between
a ruled surface and a developable surface is here repeated:
All developable surfaces are ruled surfaces, but very few ruled
surfaces are developable. Some ruled surface may be con-
structed between two space curves by any arbitrary procedure,
but if the procedure does not satisfy the fundamental require-
ments of Definition 2.3 of the paper and Theorem 2 it is not a
developable surface. It may be almost developable, but each
time you design a hull by fallacious methods you run the
risk of failure.
He also replied to some misconceptions. The example hull
is not presented as a recommended design, but only as an
illustration of graphical procedure. In regard to transverse
stations along the keel, he had not proposed that web frames
or bulkheads be eliminated, only saying that no structural
reason exists for perpendicularity of plate softeners to primary
landings. In proposing that one shipwright assisted by welders
and labourers could build a large hull by simplified methods,
it is not supposed that either the shipwright or the welders
would be incompetent.
Benford's analysis is illuminating. He shows what far-
reaching effects an initial saving can have. While the ratio
of 25 per cent is only an example, his analysis shows that any
saving is a good investment.
Michelson's remarks are humbly received. He has offered
further insight into the geometry of developable surfaces,
thereby enhancing the value of the paper.
With regard to Allen's remarks, the technique of fitting
and fastening frames after the plating is hung is very good,
and works especially well with longitudinal framing. Many
hulls have been framed in this way without previous detailed
development of the surfaces, but the inexperienced builder
should be warned that he can find himself with some freakish
results if he does not know in advance what he is doing.
Toullec's gallant endorsement is gratefully acknowledged.
Foussat supplies additional testimony that the designer can
keep control of hull form in using developable surfaces, and
that economy in construction usually results.
Paulling's reaffirmation of the hydrodynamic efficiency
possible with hard chines, comes from a man who has made
a great many observations of flow phenomena. Kilgore
believed Paulling would also endorse his plea for additional
research on flow lines around hard-chined, displacement
hulls. Johnson (1964) has also shown that hard-chined hulls
may be superior to optimum moulded forms even for dis-
placement hulls. It is necessary to go into this problem more
thoroughly, and particularly to study the effect of varying
displacement when hard-chined hulls are compared with
equivalent moulded forms.
GENERAL
Troup (UK): Had been a naval architect with a company,
which, apart from building small vessels, provided a design
service for anyone who wanted to build a vessel and had no
facilities for design or a drawing office in which to develop
these designs. Designs were developed for New Zealand,
India, the Middle East, South Africa and even for such remote
places as the upper reaches of the Zambesi. A complete set
of working drawings were completed for each design. They
were carefully drawn, detailed in every way, and in accordance
with what was modern shipbuilding practice. There were
usually very few questions about these drawings, but these
were surprising, until it was realized that they had been dealing
with people who had no tradition of shipbuilding behind
them.
Questions such as "Why don't you show flexible mountings
under the engine?" could be asked, or "could we build this
vessel upside down?"— "And if we do build it upside down,
how do we get it upright without straining it?"- "Why is
the propeller so big?" and they might well have asked
"How do we line a shaft?"
Only a few contributors have offered any real practical
help to these new shipbuilders in various parts of the world.
FAO has done a first-class job in training naval architects
and producing designs for fishing vessels, but some action
should be taken to produce papers which would be devoted
to the very difficult business of actually building a ship —
how to lay it off, how to erect it, how to erect the rudder,
how to weld awkward corners, or better still, how to avoid
awkward corners, how to get bilge pipes through double
bottoms, how to bore out a stern tube. These new shipbuilders
need the experience of traditional shipbuilding countries
and they need it in a good, solid, down-to-earth practical
manner.
There is no advantage in advanced fish boat designs, if
theie is not at the same time an increase in shipbuilding skills.
There is a very great thirst for knowledge in some countries
today, and what they need to a very great extent is simple
basic shipbuilding.
New Zealand skills well developed
McKenzic (New Zealand): Wanted to take the opportunity to
correct an impression created by Troup's remarks. Troup
placed New Zealand in the category of developing countries
and in the category of countries who had received assistance
in the way of receiving plans of fishing vessels, but un-
fortunately had no experience of boatbuilding. Whilst those
in New Zealand would welcome any information to assist
in a better design of fishing boats and will also assist the
fishing fleet in adopting more modern methods to lower the
cost of production, New Zealand should not be regarded as
a country having no knowledge of boatbuilding. The coast
line is approximately two thousand miles long and the nearest
neighbour, Australia, is separated by twelve hundred miles of,
at times, very turbulent waters, the Tasman Sea.
Of necessity, New Zealanders have been boatbuilders for
over 100 years and the native race, the Maoris, prior to the
arrival of the white man, built canoes of up to 100 ft (30.5 m)
in length. These were hewn out from trunks of trees. New
Zealand had built fishing vessels, passenger vessels and
pleasure craft in wood and up to 70ft (21 m) in length for
many, many years, During the last world war they had an
intensive ship-building programme for a small country and
some 50 to 60 minesweepers and small tugs were built for
war service. The minesweepers were constructed from
drawings supplied by UK and based on a trawler design.
These vessels were constructed in steel, wood and in some
cases were composite vessels. In the past ten years, many
new fishing vessels have been constructed, all welded steel
vessels up to 65 ft (20 m) in overall length and wooden
vessels up to 70ft (21 m) in length. Some of these vessels
have been constructed from imported plans and others were
designed by New Zealand naval architects.
In an endeavour to create uniformity and offer some assis-
tance to designers and boatbuilders, the Survey Section of
531]
the Marine Department of New Zealand, had recently
produced a small booklet which set out the requirements and
the acceptable scantlings for wooden vessels of up to 70 ft
(21 m) in registered length. At present, a 68 ft (20.8 m)
fisheries patrol vessel is being built in New Zealand and a
speed of 21 knots is specified and guaranteed by the builder.
Jet boats designed and made in New Zealand made history
by conquering the Colorado River in the US. These Hamilton
jet boats are now manufactured under licence in many parts
of the world. These few facts show that New Zealand has
some knowledge of boatbuilding.
Progress in Canada
Sainsbury (Canada): The need for increased education of all
concerned with fisheries is apparent to all and has been stressed
on many occasions; the benefits of an increased general
standard in addition to specialized training can in fact be
seen in the fishing activities of countries where a real attack
has been made on education.
Two years ago the Government of Newfoundland, together
with the Government of Canada, established a course of
fisheries in St Johns, with three main tasks :
(1) To increase the general standard of education among
young fishermen who did not complete schooling
(2) To train these young men in the basic subjects of their
vocation
(3) To operate courses in all branches of the fishing and
marine industry to provide the technically trained
personnel needed by the industry
The courses under this heading are of a very high standard,
of three or more years' duration. Students from outside
Canada are able to attend the college by special arrangement
with the Government of Canada through one of the following
programmes: the Colombo Plan— the Commonwealth
Caribbean Assistance Programme— the Special Common-
wealth Africa Aid Programme— Educational Assistance for
Independent French-speaking African States— Economic
Assistance to Commonwealth Countries and Territories.
Training programmes available under these plans are
administered by the Director-General of External Aid,
75 Albert Street, Ottawa, Ontario, Canada. Information
regarding the course of fisheries may be obtained from this
address or by writing to the College direct.
It is worthwhile noting that the plans provide free trans-
portation to and from Canada, a clothing allowance, books,
equipment and supplies allowance, enrolment fees, and a
monthly allowance sufficient to maintain the student during
the studies. These arrangements could be very useful to
developing countries, and at the course of fisheries cover, in
addition to short vacation courses, three or more year courses
in nautical science (navigation), marine engineering, fish plant
engineering, food technology (fisheries), electronics, naval
architecture and shipbuilding.
The basic course in naval architecture and shipbuilding
extends over 3i years and is based towards the size and type
of vessels which includes all the ships discussed here. A
diploma in technology is awarded and past graduate training
in a number of fields (including fishing vessel technology) is
available. Special interest to developing countries is a 15-
month course to provide students with qualifications in
engineering or a similar field with training in naval architec-
ture and shipbuilding.
Much more information on the college and all the courses
will be found in the catalogue of information which may be
obtained from: the College of Fisheries, Navigation, Marine
Engineering and Electronics, St Johns, Newfoundland,
Canada.
Orchard (Hong Kong): The need is to train boatbuilders
within the developing countries concerned. Textbooks with
fundamental basic details are helpful and FAO does, most
successfully, stimulate training in boatbuilding within the
various developing countries themselves. However, to bridge
the gap between developed and developing countries, we
ourselves have to do the grafting.
FAQ's hard won experience
Gurtner (FAO): In addition to what has been said about the
need for training and dissemination of information, not much
will be achieved by distributing written material to boat-
builders in developing countries. Many of these able boat-
builders only speak and write such minority languages as
Malayalam or Ouolof, while others perhaps speak some
English or French, but cannot read it. Furthermore, their
capacity to absorb written information is generally not great,
due to lack of experience and formal schooling. This was
realized in FAO long ago, and it is felt that it is very important
for experts to be on the spot to give advice and to impart
training to boatbuilders; they are not interested in papers,
but in practical, visual help.
[532]
PART VI
DEVELOPMENTS
Recent US Combination Fishing Vessels Development of Japanese Stern Trawlers
Luther H Blount and Edward A Schaeftrs
Recent Developments in Japanese Tuna Longliners
Small Stern Trawlers
New Trends in Stern Fishing .
Talsuo Shintizu
. W M Reid
Jan F Minncc
Jun Kazamu Discussion
Recent US Combination Fishing Vessels
by Luther H. Blount and Edward A. Schaefers
Bateaux de peche polyvalents reccmment mis en service aux E.U.
d'Amerique
Lcs bateaux de pdche polyvalents existent depuis de nombreuses
annees sur la c6te ouest des Etats-Unis d'Amerique, mais depuis peu
se manifesto un inte>6t pour ce type de bailments dans d'autres
secteurs du pays. DCS navires mixtes a passerelle a I'avant, conc.us
principalement comme chalutiers a peche par 1'arriere, ont etc
construits en Nouvelle-Angleterre.
Le chalutier a rampe arriere Nttrragansett vire son filet
enticement par 1'arriere. On ne s'est heurte a aucune difficulte en
matiere de "crpches" ni d'embarquement dc paquets de mer. Pour
la peche du poisson de fond, la rentabilite cst bien superieure a celle
des grands chalutiers de Nouvelle-Angleterre travaillant sur Ic
cote.
Le Canyon Prince, bailment plus petit, pratique le chalutage
du poisson de fond et du poisson destine aux industries des sous-
produits. Certaines unites de la Nouvellc-Angleterre, quoique
n'ayant pas et6 con^ues comme bateaux mixtes, effectuent des
operations dc peche tres variees. On pent citer par exemple le
Silver Mink, chalutier crevettier du type Floridc, Le succes
remporl£ par ce bateau avec le filet coulissant est du pour une large
part a la tactique employ6c. Le Silver Mink n'est toutefois pas
adapte a la peche du thon a la senne en haute mer, et doit attendrc
que celui-ci pgnctre dans les eaux cotiercs.
Dans le golfe du Mexique, 1'attention s'est portee sur des bati-
ments hybrides qui pratiquent la prospection des gisements peiroli-
fcres sous-marins en sus dc la pfcche de la crevette et des "snappers"
(Lutjanides). Le Service des peches commcrcialcs des Etats-Unis a
mis au point un prototype experimental dc bateau de peche
commcrciale pratiquant plusieurs metiers, destine* & Texploitation
du vaste reseau de lacs naturels ct de lacs de barrage des regions
ccntrales des Etats-Unis. Sur la base de la pratique acquise en
p^che, la principale recommandation formulee est de remplacer le
moteur diescl classique par un hors-bord diesel installe a 1'interieur.
L' Astronaut, bateau polyvalent de taille moyenne pour la
peche du "king crab", construit sur la cote Pacifique, fournit un
excellent exemple dc la substitution dc I'cnergic hydrauliquc ct
elcctrique au travail manuel. Les auteurs termincnt par unc
comparaison, fondee sur des experiences de roulis au bassin, cntre
une quille massive et des quilles de roulis montees sur un ferry-boat,
indiquant qu'il y aurait tout interet a organiser des essais analogues
pour les bateaux dc peche.
Recientes barcos mixtos en los E.E.U.t.
En los Estados Unidos, los barcos pesqueros mixtos han sido cosa
corriente en la costa del Pacifico durante muchos artos, pero en los
ultimos tiempos tambien en otras zonas del pais ha ido surgiendo
interes por cllos. En Nucva Inglaterra han sido construidos barcos
mixtos con el puente a proa, fundamcntalmente disenados como
arrastreros por popa. El arrastrero con rampa a popa Narragansett
cobra el artc completamcnte por popa. No se ha tropozado con
problemas para liberar enganches o por inundaciones del puente.
La rentabilidad de un arrastrero para pcsca de fondo es mucho
mas elevadu que la dc un gran arrastrero dc Nueva Inglaterra que
act ue por el costado.
El Canyon Prince, cmbarcacion de tipo mas pequeflo, se ha
dedicado a la pesca de arrastre de fondo y a la de peces industriales.
Algunos barcos de Nucva Inglaterra se han dedicado a una diversi-
dad de operauones pcsqueras, aunque no estan proycctados
espccificamente como barcos mixtos. Uno de ellos es el arrastrero
Silver Mink para camarones, del modclo de los utilizados en
Florida. Las tecnicas de pesca desempcftan un papel importante en
el cxito de sus faenas de pesca con red dc csrco. Este barco cs
inadecuado para la pesca del atun con red de ccrco en aguas de
altura y depende de la migracion de los pcces a aguas mas cercanas
a la costa.
En el Golfn de Mexico, la atencion se ha concentrado en los
barcos mixtos que llevan a cabo trabajos de estudio petrolero
en aguas de altura, asi como la pesca de camarones y de pargos.
La Oticina dc Pcsca Comercial de los Estados Unidos ha ideado un
barco de pesca mixto comercial-experimental para trabajar en el
gran sistema de cmbalses y lagos existentes en la purte central de los
Estados Unidos. Basandose en la experiencia de trabajo, la principal
recomendacion consiste en sustituir los motores normales diesel
internos con unidades de propulsion diesel internos-extcrnos.
Un barco mixto de tamafto medio construido en lu costa del
Pacifico estadounidense es el Astronaut para la pesca de centollas,
cl cual es un magnifico ejemplo de la ventaja de la sustitucion de la
potcncia manual por la energia hidraulica y electrica. Por ultimo,
una comparacion de la quilla maciza y de la quilla dc balance en un
transbordador indica que tal ensayo podria ser venlajoso en las
embarcaciones pesqueras.
IN the USA, the term "combination-type fishing vessel"
is usually associated with the Pacific coast. This type
of vessel, ordinarily under 100 GT, is designed
to purse seine for salmon, trawl for groundfish and
shrimp, longline for halibut, use pots for crabs, and troll
for tuna and salmon. Various factors, such as seasonal
availability of the major fish species, adequate conserva-
tion measures, short seasons, social-economic con-
siderations, and the realization that diversification
provides increased opportunities for efficient year-round
operation, were initially responsible for its development.
On the US Pacific coast, according to Hanson (1955),
single-purpose craft are extremely wasteful, although some
types, such as large tuna vessels, perhaps can be justified.
The tendency for US fishing vessels of under 100 GT to
be multi-purpose vessels has spread from the Pacific
north-west to the north-east coast (New England). Some
companies have designed and constructed even offshore oil
survey and service vessels easily adaptable to the Gulf of
Mexico shrimp and snapper fishing. Finally, in an
attempt to determine the most practical type of vessel to
fish the unexploited vast network of central US inland
rivers and reservoirs, a prototype experimental combina-
tion vessel for commercial fishing operations has been
designed and constructed. This report reviews recent
trends in the design, construction, and operational
experiences of US combination-type vessels. Particular
emphasis is placed on specific vessels designed for
operation in specific geographical areas.
[535]
ATLANTIC (NEW ENGLAND) COAST
COMBINATION VESSELS
After large European stern-ramp trawlers appeared off
the north-east Atlantic coast, the New England trawling
industry showed interest in the US west coast style of
combination purse-seiner-trawler that uses stern-trawling
techniques. Additional stimulation for the introduction
of combination vessels was the need to develop a purse-
seine tuna fishery. New methods were obviously re-
quired, but the advanced technical experience of the
US had not been in this direction. Stern trawlers of
European design were 120 ft (36.6 m) or more, and many
US operators felt these would be unprofitable in the
medium-distance fishery.
Medium-distance vessel, Narragansett
It appeared that a combination stern trawler of 65 to
100 ft (19.8 to 30.5 m) designed primarily as a stsrn-ramp
trawler, but readily adaptable to purse seining and
scalloping, would be most suitable. Background in-
formation was assembled to design a vessel with the
features of the west coast net-drum trawler and the
smaller European stern trawler. Pacific coast trawlers
have used a stern-trawling system, except that the entire
trawl was swung to the side of the vessel and hoisted
aboard amidships in a series of lifts. The net-reel drum
system introduced in the late J950's (Wathnc, 1959)
brought most of the net over the stern; however, the
cod-end still had to be swung to the side of the vessel for
bringing aboard. The boat had to be stopped dead at the
time the gilson was connected to the cod-end. The vessel
was then turned sharply port or starboard to swing the
cod-end over either side rail and backed astern until the
cod-end was at the side for emptying. This required
stopping, turning, and backing and would not always be
practical in the north Atlantic because of weather and
sea. If the cod-end could be hauled directly over the stern,
the boat could continue under power in one direction for
the most comfort and efficiency in handling.
An east coast shipyard decided, therefore, to design
and construct a medium (50 to 150 GT) stern-ramp
trawler with its net drum just aft of the bridge; this
location would allow the entire net to be hauled aboard
over the stern. The optimum size of stern trawler for the
offshore banks, such as Georges Bank and Browns Bank,
was calculated to be about 113 GT and 83 ft (25.3 m)
Loa (table 1). Several designs were developed along the
lines of the traditional "eastern rig" with the bridge aft,
but offset to accommodate the net. Considering all
factors however led to the decision that the "western rig"
with the bridge forward was a more feasible combination
vessel design. One factor seldom mentioned in the con-
struction of "western rigs" is that they cost more to
build than the "eastern rig" for the following reasons:
• The engine either has to be located forward of the
fish hold or placed aft with a more complicated
arrangement
• Controls have to be led further
• Crew's quarters arc more expensive
• Separate heating and services have to be supplied
for two areas
Specialized equipment
An additional consideration in designing and con-
structing the stern-ramp trawler, Narragansett, was the
availability of several recent mechanical systems in the
US that made some automation possible. The most
important among these was the air tube clutch and brake
operation that allows finely and remotely controlled
clutching and braking. Furthermore, no important
mechanical elements in the system are subject to salt-
water deterioration. Another development that made the
Dimensions
Loa
Length registered
B
B over guards
D
Capacities
Fish hold
Fuel oil
Fresh water
TABLE 1
Principal characteristics of the Narragansett
83 ft (25.3 m)
76 ft (23.2 m)
22 ft 6 in (6.86 m)
23ft 6 in (7.16m)
12ft 3 in (3.73 m)
4,300 ft3 (120.4 mfl)
3,500 gal (13,2471)
600 gal (2,271 1)
Deck Gear
Trawl winches — 2 single drum, 1,000 fm
(1,830 m), £ in (15.9 mm) diam wire
per drum
Net drum— 1 single
Winch and drum— 120 hp drive
Rigged for stern trawling
Electrical
AC system 5 kW off main engine
DC system 1 50 A and 60 A alternators off
main engine, 50 A alternator off winch
engine 2 x 32 V battery banks
T, keel, light
T, keel, loaded
GT
NT
.Might
L loaded
Propulsion
Main engine
Drive
Propeller
9 ft 2 in (2.79 m)
11 ft 6 in (3.52 m)
113(111)
95 (93.5)
142 tons (140 ton)
228 tons (224 ton)
380 hp w/air clutch
gear belt
Controllable pitch
60 in (1.54m) diam
Electronics
Fish finder— Radio receiver
Depth sounder— Loran
Radar- Auto pilot
Radiotelephone
A ccommodation — 9
Structural
Plating— bottom and bilge strakes f in
(9.5 mm) sides, deck and whaleback
•A in (7.9 mm), J In (6.3 mm)
elsewhere
[536]
7. Medium distance combination stern-ramp trawler. Setting the trawl
2. Hauling the cod-end
[537]
"piggy-back" stern drive feasible is the toothed gear
belt made of stainless steel cables surrounded by rubber
and nylon fibre composition with teeth of moulded
nylon. This has been available only in very recent years.
Other devices include an infinite variety of air control
mechanisms and specialized valves.
Stern trawling system
According to Manning (1964), by European stern trawler
standards, the net hauling system is both simple and
effective (fig 1 and 2). The otter trawl is dragged by
warps led through sheaves on conventional gallows and
on the frames. These gallows are fitted against the bul-
warks and port and starboard, a short distance forward
of the rudder post. The trawl warps lead to trawl
winches port and starboard, which are controlled from
the bridge. The engine-in-stern, belt-driven trawler, is
one of the first US vessels to have a trawl handling
system adaptable to remote and automated control. This
is accomplished by means of a remotely controlled net-
winding drum, located forward The main engines are
"piggy-backed" over the shaft to keep them as far aft as
possible, thus increasing the fish hold space. The vessel
is one of the first attempts to combine the navigation
bridge and net hauling controls at a single station, with
360° observation overlooking the deck. All power-
assisted equipment is controllable from this point.
The trawl board connections utilize a system developed
on the US west coast. The net can be disconnected from
the trawl boards and re-connected to leads attached to
the net drum.
The Narragansett carries 1,000 fm (1,830 m) of
0.625 in (15.9 mm) trawl cable on each trawl winch.
Automated hauling features
Initially, the Narragansett was fitted with an automated
system that allowed the winches to be stopped after the
desired length of trawl cable had been shot. This system
however, was too radical for the New England crew, who
preferred to hand-control the payout. An automated
haulback system also was installed in the vessel to allow
course to be set upward or downwind and the net
hauled in by pushing a button. Both winch drums, which
are locked together for the operation, function simul-
taneously and haul the trawl wires more or less evenly.
An air-operated limit control stops the winch drums
when the doors reach the gallows frames, and the brake
is applied automatically. This system, too, bowed to
tradition and reverted to hand control, retaining only the
feature of interlocking the clutches and brakes. This
example bears out the fears expressed by Pain et al,
(1964) that fishermen who are being faced more and more
with a mass of highly scientific "black boxes" would be
frightened of them rather than consider them as "big
brothers".
Controlling propeller thrust
Delicate control of propeller thrust may be accomplished
by varying the pitch of the vessel's controllable pitch
propeller. This is particularly important: firstly, to
obtain enough force to shoot properly and carry the net
off and out over the stern ; and secondly, to provide just
enough steerage way when hauling and splitting. On the
Narragansett, a stop has been put on the pitch control
to prevent the pitch from going to below the setting that
provides minimum forward speed while trawling.
Specialized techniques
No serious trouble has developed with regard to hang-
ups on the bottom. The vessel always has been capable of
backing over the obstacle and retrieving the net. At any
time during fishing or hauling, a single lever remotely
controls the winches singly or collectively. In addition,
the air-controlled winch drums can literally "inch" the
cable in or out. The problem of steering or control when
the net is hung on the bottom has been solved by placing
the gallows frames far enough forward so that the vessel
can pivot under the warps. For emergency turns, one
warp or the other is slackened off at the bridge control-
console so that the Irawler manoeuvres quickly if the
net is fouled on the bottom. Deck flooding has not been
any problem. The vessel's ramp is short and steep and the
incline begins several feet above the waterline. The ramp
is closed off to the sea by a tailgate that is opened while
setting and hauling.
Economic analysis
As a commercial fishing vessel, the Narragansen also
represents important economic change from the normal
offshore New England side trawler. The crew is normally
seven compared with 1 7 on the typical large offshore side
trawler. This is a significant increase in the ratio of capital
to labour. Studies of industries that have been charac-
terized by increasing productivity and efficiency have one
common factor — an increasing capital to labour ratio.
Even though the Narragansett may not bring back as
large a catch as the larger side-trawler, the profitability
in terms of earnings per fisherman and yield per dollar
invested in vessel and gear is much higher. In vessel design
we must accept the principle that these arc the final criteria
TABLE 2
Economic analysis of trawling operations,
Narragansett and side trawlers
Side trawler
Narragansett
high
earning
low
earning
Number of trips
Average trip days
15
7.7
27
10.4
24
10,7
Average crew size
Total landings Ib
(kg)
7
979,400
(440,000)
15.8
2,882,500
(1,308,655)
15
2,044,700
(928,294)
Land ings/ trip Ib
(kg)
65,300
(29,600)
106,759
(48,469)
85,196
(38,679)
Landings/man trip Ib
(kg)
9,329
(4,230)
6,756
(3,067)
5,673
(2,575)
Landings/day Ib
absent (kg)
8,481
(3,840)
10,265
(4,660)
7,962
(3,615)
Value of landings £
($)
36,300
(101,700)
92,488
(258,966)
63,428
(177,598)
Value/day absent £
(!)
315
(881)
329
(922)
242
(678)
Min. wage and £
food cost/day (!)
absent
38
(107)
87
(244)
84
(235)
[538]
of design success. Of particular importance to the vessel
owner is the decrease in costs for payment to the crew
for trips where the value of the crew share does not cover
the guaranteed minimum wage. The relative advantages
of these economic factors are demonstrated in table 2.
Data on side trawlers are for vessels 1 50 GT and over and
are based on average annual operation per vessel (for
the years 1960 to 1963). Figures for the Narragansett are
based on data for 15 groundfish trips during 1964.
Diversified operations to dale
During the first five months of successful operation, the
ship was engaged in groundfish and deepwater lobster
trawling and made several longlining trips for swordfish.
Then a charter was obtained to help dismantle offshore
platforms on Nantucket Shoals and Georges Bank. The
vessel supplied the wrecking crews with food, acetylene
and oxygen equipment, and freight etc. and brought back
the dismantled equipment. This charter enabled the ship
to make much more money than it would have under
normal fishing. The charter lasted for three and a half
months.
The vessel was ideally suited for a number of reasons:
firstly, the dismantling operation was far out at sea
and a strong, medium-range vessel was needed to with-
stand the rigours of the North Atlantic; and secondly, all
hoisting gear was already aboard and only one and a half
days were required to remove the fishing equipment,
features that a normal supply boat would not have.
Later, the Narragansett was sold to her present owners,
who were contacted by a Gulf of Mexico oil exploration
firm that wanted a boat. The boat was easily reconverted
and engaged in oil exploration for about nine months,
with once again a very handsome profit and, incidentally,
with several of the original fishing crew aboard. The boat
is now again commercially fishing.
Short-distance combination stern-ramp trawler, Canyon
Prince
Following the success of the Narragansett as a ground-
fish trawler, the desire of various industrial fish trawling
interests for a smaller combination stern-ramp trawler
was met with the 65 ft (19.8 m) Loa Canyon Prince
(table 3, fig 3 and 4).
The vessel was designed for operating from small
harbours, primarily tor industrial fish. Since the distances
Fig 3. Short distance combination stem trawler
[539]
TABLE 3
Principal characteristics of the Canyon Prince
Dimensions
Lou
Length registered
B
B over guards
D
Capacities
Fish hold
Fuel oil
Fresh water
64 ft 11 in (19.8 m)
61 ft (18.6 m)
20 ft 6 in (6.25 m)
21 ft 2 in (6.56 m)
9 ft 6 in (2.89 m)
3,500 ft3 (98 m3)
3,800 gal (14,383 1)
30Ogal (1,135 1)
Deck Gear
Trawl winch -double drum, 45O fm (823.2 m)
£ in (15.9 mm) per drum
Net drum — 1 each
Winch and drum — main engine power drive
take-off
Rigged for stern trawling
Structural
Plating — bottom and sides
decks i in (6.3 mm)
ft in (7.9 mm).
T, keel, light
T, keel, loaded
Alight
A loaded
Propulsi€m
Main engine
Drive
Propeller
8 ft 3 in (2.52 m)
10ft 6 in (3.2 m)
67 tons (65.9 ton)
13O tons (127.9 ton)
335 hp
marine shafting-std
4 blade, 6O in (1.54m)
Electnmics
Fishfinder-Radio telephone
Depth sounder-Radio receiver
Radar — Loran
Electrical
AC system 7.5 kW auxiliary
DC system 6O A alternator off main
engine, 2 x 32 V battery banks
A ccommodation-—%
Fig 4. Emptying the catch
[540]
to the grounds were short, usually less than 75 miles
(120 km) for red hake and 25 miles (40 km) for tuna, this
vessel has been quite profitable. It was found that in
designing smaller boats, it was necessary to offset the net
drum and balance the opposite side by the trawl winch
to achieve enough deck working space. On the Canyon
Prince, the ramp was located the same side as the net
drum and worked quite well, particularly for ground-
fishing. For industrial fish operations, however, moving
the net drum to the stern made it much easier to split the
big catches. The net drum was situated just far enough
forward of the transom to allow the net to be repaired
from each side. The control with a fixed propeller, while
not as delicate as with the variable pitch propeller, was
acceptable. Some trouble has occurred. On several
occasions when the propeller has been inadvertently
left in neutral and the vessel has had little or no headway,
the doors and net have come into contact with the
propeller.
Modified shrimp trawler as combination vessel, Silver
Mink
Although the expanding industrial bottomfish industry
supplying pet food factories in the Gulf of Mexico has
utilized existing standard shrimp vessels, the basic-
method is still the same- trawling. Of particular ''merest
is the use of a conventional Florida type wooden shrimp
trawler for various types of fishing in New England
waters.
Fish trawling and tuna seining
The Silver Mink (fig 5), originally designed as a shrimp
vessel, has been used for a variety of fishing operations
other than shrimping. Initial New England operations
concentrated on trawling for industrial fish (fig 6) as well
as readily marketable food fish. A unique use of this
vessel occurred in 1958 when it was rigged for tuna
purse-seining (Squire, 1959). The vessel landed 161 tons
(163 ton) of bluefin (table 4) during a short season of
about ten weeks. Previous sporadic efforts by regular
west coast seiners in earlier years produced a maximum
catch per season of only 122 tons (123.8 ton). Table 4
shows the tuna seining results for the Silver Mink, 1958
to 1961
Fig 6. Emptying Mas trial fish trawl catch
(note removable gallows)
TABLE 4
Comparison of tuna seining results,
Silver Mink, 1958 to 1961*
Tons (ton)
Length of season •
weeks
Number of trips
Number offish
Average weight of
fish— Ib (kg)
1958
161 (163)
10
29
1959
678 (688)
7.5
30
J 1,577
130.8
(59.4)
I960 1961
302 (306) 921 (934)
4
20
4,620
146
(66.5)
13
86
Fig 5. Shrimp vessel rigged for tuna purse seining
' Includes catch of an additional 65-ft (19.8-m) purse seiner in 1961.
Modifications
Modifications of the vessel for tuna seining were simple
and consisted of removing the trawl gallows and installing
an extended boom for initially strapping the net aboard.
The existing double-drum trawl winch was used for
purse-seining operations. The tuna purse seine was of
linen and cotton netting 310 fathoms (567 m) long and
25 fathoms (45.8 m) deep. Most trips were on a daily
basis out of Provincetown, Mass., in the immediate area of
Cape Cod, namely Cape Cod Bay and Massachusetts Bay.
Later, the natural fibre seine was replaced with nylon, a
power block was installed (fig 7) and aeroplane spotting
was employed. Initial success led to an expansion of the
east coast tuna fishery from inshore waters near Cape
Cod to a high-seas fishery extending south to Cape
[541]
Fig 7. Hauling a tuna purse seine net
Hatteras, NC In 1963, according to Wilson (1965), the
total catch by 16 US vessels and two Canadian vessels
was over 18 million Ib (8.2 million kg). The success of the
initial fishing for tuna stimulated the owner to use the
vessel for purse seining herring, alewives and mackerel
until the tuna runs start, usually in late July.
Fishing tactics
Fishing tactics play an important role in the operation.
For example, it was ascertained that, while scouting for
tuna, the vessel often would encounter only schools of
herring or mackerel that could not be taken with the
large-mesh tuna seine. To assure that the correct net is
on board, an aeroplane is now used for fish-scouting
while the vessel remains at the dock. The aeroplane
scouts waters adjacent to Provincetown during the
morning. If tuna are spotted, the pilot radios the vessel
and the tuna seine is loaded; if mackerel or herring are
spotted, the other seine is loaded. The pilot circles the
schools until the vessel arrives and sets the seine.
During the autumn of 1964, the vessel purse seined
268 tons of mackerel in about five weeks. From January
to June 1965, 616 tons of herring, 446 tons of alewife and
a few mackerel were caught. This is a case where a com-
bination of factors, namely, a versatile vessel, availability
of a variety of fish in commercial quantities in strategic
geographical locations, adequate markets and, prob-
ably most important of all, the ingenuity and resourceful-
ness of the owner-captain, result in maximum utilization
of the vessel.
Limitations of vessel for tuna seining
While the vessel made favourable tuna catches during
subsequent years, catches have fluctuated considerably,
because it has to operate in inshore waters. The large
size of the seine and accessory equipment precludes
operations in weather and sea conditions encountered
in offshore waters. Success is therefore dependent on the
bluefin tunas being available in inshore waters. The east
coast tuna fishing grounds have been extended to offshore
waters by vessels of the regular California tuna seining
fleet, including some of the largest individual vessels of
that fleet. Catches in offshore waters have included
considerable quantities of skipjack tuna, which are not
available to the inshore fleet.
This is not the only case of a shrimp vessel being used
as a seiner. Robas (1961) reported that a standard 50-ft
(15.2-m) steel Mexican flag shrimp vessel was successfully
seining jack crevalle in the Gulf of Mexico. A seine 180
fathoms long (329 m) and 22 fm deep (40.2 m) was set
from an elevated table on the stern.
GULF OF MEXICO COMBINATION VESSELS
Until recently, there has been little, if any, attention
given to the construction of multi-purpose combination
fishing vessels for the Gulf of Mexico. The main reasons
are that rather standardized single-purpose vessels have
prevailed in the two major fisheries— trawlers in the
shrimp and purse seiners in the menhaden fisheries. The
recent booming of the offshore oil industry in the Gulf of
Mexico has required great numbers of vessels. Oil survey
vessels are used for seismic explorations, transporting
cargo, ferrying workers to and from offshore drilling
platforms, and general utility work.
Modified oil survey-shrimp vessels
A style of vessel was developed which is readily adaptable
from oil survey to use in shrimp and industrial fish
trawling, as well as snapper fishing. The simplicity of
design tends to reduce the cost and they can be built
even by the smallest shipyards in the Gulf of Mexico
area.
Although the space devoted to the various features of
the vessel varies with its intended primary service in the
oil industry (cargo, passengers or explorations), the basic
hull design is the same. The length varies from about
70 ft (21.2 m) to 100 ft (30.5 m). A vessel designed
primarily for passenger-carrying service to offshore oil
drilling platforms with the features of a shrimp vessel is
shown in fig 8 and 9. This vessel has a fuel capacity of
about 25,000 gal (84,600 1), water capacity of 2,700 gal
(10,219 1) and is twin-screw with two 330-hp diesel
engines. It is usually equipped with air conditioning.
While it may be too large to interest most shrimp
fishermen, scaled-down versions can easily be built. For
example, several 70 ft (21.2 m) vessels have been con-
structed this year. These are scaled-down versions of the
95 ft (29 m) vessel and have either single or twin-screws.
The single-screw type is 300 hp and the twin-screw type
has two 230-hp diesel engines. The fish-carrying
capacity is about 175,000 Ib (79,450 kg). These vessels are
currently chartered to oil interests, but are built to replace
the fleet of conventional wooden shrimp vessels.
As early as 1954, vessels were built in the Gulf of
Mexico expressly for oil explorations with the object of
future use as shrimp vessels. Such a vessel, originally
used in oil exploration and now rigged for shrimp
trawling, is shown in fig 10. The lines are those of a large
Gulf of Mexico shrimp vessel, but the house is modified
along the lines of current oil survey vessels. This 83 ft
(25.3 m) vessel is constructed of wood, of 120 GT and
82 net tons. After lengthy service in oil explorations,
the vessel engaged in commercial shrimp fishing. It is
currently used in biological research on shrimp.
[542]
tLlVATION LOOKING fWP.
F/£ 8. Preliminary arrangement combination commercial fishing ami oil survey vessel
TIAWl
•OOM r/t
e !
J/
NO| OAlllY
, —
F'71
'
,
1ST.
.,»H n. .___
.
m'l/wr'il'ii.
•--- f -; -
- •}
%I-M
IAZAIETTI
mm WAIII,
Dim w.i It,
MACHINIIV SfACI
. . -U1M-UNJL (UOW
— ~*" i
s^
;
•
;:::.«-• -
4JW._1_
::.ZTI
Fig 9. Preliminary arrangement combination fishing and oil survey vessel
[543]
Fig 10. Oil survey vessel modified for shrimp trawling
RESERVOIR COMBINATION FISHING VESSELS
The central area of the USA has vast networks of reservoirs
and lakes formed by dams designed for flood control,
irrigation, navigation and hydro-electric purposes. Some
of these, such as the Oahe Reservoir in the Dakotas, are
large bodies of water. This particular reservoir is 250
miles long (402 km), varies in width from several hun-
dred yards to several miles, and will eventually have a
water area of 376,000 acres (158,000 hectares). Another
example is Kentucky Lake in Tennessee, which covers
158,000 acres (64,100 hectares) and has a potential
commercial yield of 32 million Ib (14.5 million kg) of
fish annually.
Since the major portion of the fish in reservoirs cannot
be absorbed immediately for human food markets, the
development of highly productive fisheries must rely on
industrial-type outlets. This means high-volume fishing
at low-landed value. The relatively small open-boats now
used in US inland fisheries are definitely not suited for
such fishing.
To determine the most effective craft for economically
harvesting the untapped fishery resources of these areas,
the US Government recently began operating an experi-
mental fishing vessel equipped to fish with trawls, gill
nets, trap nets and other types of seines and capable of
making simulated commercial fishing tests as well as
conducting research activities. It could be modified
easily for commercial fishing.
Type and design
In developing design criteria for the experimental vessel,
Hiodon, various factors necessary to "fit" the vessel to
the intended fisheries were considered. The original work
was scheduled for the Oahe Reservoir which appeared
to offer good potential for early development of a com-
mercial fishery. A well-equipped, multi-purpose vessel
capable of operating independently at distances of 100 or
more miles (160 km) from home port for periods of over
one week was essential for experimental operations as
well as commercial operations. Such a vessel should be
primarily flat-bottomed with a barge-type bow and
tunnelled stern to allow rudders and propellers to be
completely above the bottom of the hull. Consideration
of methods was also necessary to permit ease of trans-
portation of the vessel overland to other reservoirs. This
design, coupled with twin-screw propulsion, would
permit fishing in shallow water. The vessel should be of
welded steel construction capable of withstanding
weather and storms in the Mississippi drainage area.
The possibility of grounding during shallow-water
operations necessitated the use of 0.25 in (6.3 mm) hull
plating throughout.
The Hiodon is equipped with modern deck machinery
and electronic equipment. The deck equipment consisting
of two single drum trawl winches, power block, net
drum and articulating crane, is driven hydraulically by a
dual pump coupled to one propulsion engine. This pump
provides oil at 1,800 lb/in2 (130 kg/cm2) to a single
remote station which controls all functions of the deck
machinery. This arrangement allows the vessel to be
safely operated by a two-man crew. Electronic equipment
includes a 35-watt radiotelephone and a "white-line"
type echo-sounder. The echo-sounder is equipped with a
controllable transducer for both horizontal ranging and
vertical depth sounding or fish detection. The vessel,
constructed in 1965, has the following characteristics:
Construction
Length
Beam
Hull depth
Draft
Main engines (2)
Net drum
Deck crane
Trawl winches
Cruising speed
Cruising range
Displacement, light
Displacement, loaded
Accommodation
Propellers
Generator
all steel welded
46ft (14m)
14 ft 6 in (4.4 m)
4ft (1.2m)
2 ft 6 in (.76 m)
85 hp each, diesel
l,5001b(681 kg), 45ft
(13.7 m)/min
2,500 Ib (1,135 kg) capacity
Single drum, port and star-
board, capacity each drum:
2,000 ft (610 m) of -ft in (7.9
mm) wire, 2,000 Ib (908 kg) at
160 ft (48.8 m) per min.
8.5 knots
1,500 miles (2,41 3 km)
20 tons
35 tons
4 personnel
26 in (66 cm) diam, 20 in
(50.8 cm) pitch
6kW
Drawings of the profiles and deck arrangement are
presented in fig 1 1, and fig 12 shows the vessel underway.
A transporting unit was built to facilitate moving the
vessel from one reservoir to another. This unit consists of
two assemblies, a heavy-duty wheel and axle assembly
fitted with "I" beams shaped to fit an inverted "T"
attachment under the stern of the vessel and a towing
frame pinned to the bow (fig 13 to 15). The towing
frame is equipped to fit the towing facility of any stan-
dard transport truck. This unique arrangement permits
travel over gravel or hard surface roads at speeds to
50 mph (80 km/h).
[544]
-1 Asdic
---1
Fl I
F.W.
JL tanks Pa S
2X85 HP Diesel engmesS
F.W
Fish topks
Fig 11- Reservoir vessel, general arrangement
[545]
Fig 12. Reservoir vessel
^fl^O)
Fig /.?. Towing arrangement for lam/ transport
Fig 14. Hooking the vessel to a truck
Fig 15. Transporting the vessel
Recommended changes for future designs
Based on initial operations, substantial improvements
would be obtained over the existing design by in-
corporating the following modifications, especially in a
commercial version (fig 16).
Hull design
A longer bow curve of inverted-spoon type would reduce
water resistance and help overcome the tendency to
nose down in upper speed range.
Main propulsion
Replacement of standard engines, through-hull shafts,
skegs and rudders with inboard-out board diesel pro-
pulsion units would reduce engine room space require-
ments, increase hold capacity in an area of the hull where
increase in payload would not affect trim, eliminate the
need for a tunnel stern which is lifted by propeller wash
considerably, and simplify maintenance and repair since
outboard section of propulsion unit can be lifted to
deck level to facilitate propeller work and rudders are
not needed with inboard/outboard propulsion units.
Auxiliary power
A separate engine of about 60 hp diesel should provide
auxiliary power to drive 10 kW generator at one end
and 35 hp hydraulic pump the other.
Deckhouse
The deckhouse on a commercial version should be much
smaller because it can be operated by two fishermen, who
will have no need for covered laboratory space.
Deck gear
The deck machinery complex (including two trawl
winches, net reel and articulated crane) with controls
could be located from bulwark to bulwark between the
22 ft (6.7 m) (from the bow) and the 28 ft (8.54 m)
marks. This is about midway along the length of the hold
space and would facilitate dividing the hold into fore
and aft sections fitted with hatches within easy reach of
the articulated crane.
PACIFIC COAST COMBINATION VESSELS
Schmidt (1960) reported that the U.S. Pacific coast
combination vessels had been developed primarily as
purse seiners modified for use as trawlers and long-
liners. Most small combination vessels of the Alaska
Limit seiner size, maximum registered length 50 ft
(15.3 m) and about 58 ft (17.7 m) Loa, are still designed
primarily as purse seiners, but the major secondary use
is for king crab fishing with pots (Allen, 1964). Most of
the very few medium-size combination vessels recently
built in the Pacific north-west have been designed
firstly for trawling and secondly for king crab fishing.
The vessel Astronaut (fig 17) is a good example of this
type (Anonymous, 1962). The main feature of this vessel
is the substitution of hydraulic and electric power for
manpower. The principal characteristics are:
[546]
V
F.W.
2 Diesel engines
inboard -out board
Loa
Lpp
B
T
GT
NT
Fuel oil
Water
Engine power
Generator
Accommodation
10 20
l-ig If). Proposed modified reservoir vessel
66 ft (20.1 m)
59ft 4 in (18.1 m)
18ft 2 in (5.6 m)
10ft 7 in (3.2 m)
77
31
7,000 gal (26,495 1)
3,000 gal (11, 3551)
227 hp
20 kW
6
40
The vessel is of all-steel construction with 0.31 in
(7.9 mm) plate on the Vee-bottom and 0.25 in (6.3 mm)
on the sides and decks. After initially fishing groundfish,
the vessel is now fishing king crab pots in Alaska.
SPECIFIC DESIGN STUDIES DESIRABLE
The need for specific fishing boat design studies has been
brought out at the First and Second FAO World Fishing
Boat Congresses. During the design and construction
of the Narragansett and Canyon Prince the roll damping
effect of bar keel compared with bilge keel was considered.
Scientific analysis through model rolling tests are far
too expensive for the individual small fishing vessel con-
Fig 17. Cvmhinaiion trawler king crah fishing vessel
struction yard to finance. The need for such tests,
however, is clearly evident in comparing the seakind-
liness of the Narragansett and Canyon Prince. The need
for these tests is further brought out in model rolling
tests to determine the effect of a bar keel on the 150 ft
(45.7 m) Loa vehicle-passenger ferry Uncatena.
[547]
s2
Because the Narragansett, which did not have a bar
keel, rolled heavily before bilge keels were installed, a
bar keel was installed on the Canyon Prince. Model
tests of bar keels on vessels of the size of the Narra-
gansett are particularly recommended since vessels of
this size are too large to utilize effectively onboard
HMt — SICON
Fig 18. Representative curves of rolling amplitudes from model
rolling tests, m.v. Uncatena
stabilizers as roll damping devices. To strengthen our
recommendation that such tests be undertaken for
fishing vessels, the report of the model rolling tests to
determine the effect of the bar keel is included as an
Appendix. This report clearly indicates that bilge keels
are really unnecessary when a bar keel of the proportions
used on the Uncatena is installed (fig 18 and 19).
11 12 13 14
TIME -SECONDS
fig 19. Curves showing rate of decrease of rolling amplitude
from model rolling tests, m.v. Uncatena
CONCLUSION
There is a growing trend in the USA for combination-
type fishing vessels to be built in areas other than the
Pacific coast. This trend has been brought about by the
realization that, by building combination-type vessels,
fishermen are able to harvest several types of fish, each
of which may require a different type of gear. This pro-
vides for year-round use of the vessels and removes the
risk that one-purpose boats always face dependence on a
single type of fish, the abundance and availability of
which may fluctuate greatly. There has also been
profitable employment for combination vessels de-
signed for oil exploration work and fishing. Model tests to
determine the roll damping effect of bilge keels and a bar
keel would have been of considerable benefit in the
design of the Narragansett and Canyon Prince.
Acknowledgment
The authors were assisted by the staff of the Branch of Exploratory
Fishing, Bureau of Commercial Fisheries; Howard Chapelle; Gulf
City Fisheries Corporation; Captain Manuel Phillips; Captain Dan
Luketa and J. E. Bowker.
APPENDIX
During the design of the Uncatena, it was decided to fit
a deep bar keel along the centreline at the bottom of the
vessel with the expectation that this member would:
(a) overcome any tendency that the vessel might have
towards directional instability; (b) increase resistance to
drift downwind; and (c) substantially reduce the amount
of rolling in a seaway so that bilge keels would not be
needed. Since the preliminary design profile had con-
siderable rise of keel (from the end of the skegto the bow),
a deep full-length bar keel could be worked in without
increasing maximum service draft, by reducing the rise of
keel and modifying slightly the shape of the hull form over
the forward half of the vessel. Since the intended route
passes through shoal water, actual service draft is critical.
This bar keel is 1.25 in (3.2cm) thick and projects
13.5 in (34.3 cm) below hull between the curve of the
forefoot and amidships. Aft, as the hull form rises, the
bar keel blends into the centre line skeg, having the
effect of increasing the skeg depth, particularly near
amidships. The depth of the bar keel above includes the
thickness of a flat bar 6 in (15.2 cm) wide, welded, T-
fashion, to the bottom of the bar keel to provide a
suitable resting surface on keel blocks when the vessel is
dry-docked.
Comparing the final underwater profile of that with
the keel and that without, a strip about 13 in (33 cm)
deep and approximately 124 ft (37.8 m) long, equivalent
to 134 ft2 (12.5 m2) has been added to the lateral area
of the vessel. This is based on the assumption that the
bar keel would replace a flat plate keel in area.
Bilge keels were considered for this vessel and roll tests
were made using a J4 scale model of the vessel's hull,
ballasted and with a metacentric height suitable for one
of the expected service conditions. These tests were
conducted in the model testing tank at Massachusetts
Institute of Technology, by forcibly heeling the model to a
specific angle, then suddenly releasing it and recording
roll amplitudes for several seconds. The rate of decrease
of roll amplitude was plotted from the amplitude-time
graphs obtained and a comparison made for correspond-
ing conditions.
Subsequently, the bar keel was removed from the
model, together with its extension along the bottom of the
skeg (representing a strip 13 in wide, 124ft long) and the
model was again rolled, ballasted as before, in order to
get information as to the roll damping effects of the bar
keel.
Records of decreasing amplitude of roll were made, as
before. These tests were made only with the model at
rest (not being towed) in order to avoid effects of water
pressure, resulting from flow, against the hull. Com-
parison of the rate of decrement of roll from these tests
with those previously obtained for zero model speed
[548]
indicates that the bar keel does have a measurable
effect as a roll-damping device.
With the bar keel on the model, but without bilge keels,
the amplitude of rolling decreased from 20° (full roll,
port to starboard) to 10° in 5.6 sec, an average rate (for
this range of amplitude) of 1.79° per sec. With the bar
keel removed, the average of four roll tests gave the time
to reduce the roll from 20° to 10° as 6.3 sec, an average
rate of 1 .59" per sec over this range. It was also found that
removal of the bar keel was accompanied by a slight
increase in the period of roll of the model, from 1.85 sec
to 2.0 sec.
Figure 1 8 shows two roll amplitude curves obtained with
'the "envelopes" of maximum amplitudes added. The
curves shown are for zero model speed, one is for the
model with bar keel and without bilge keels; the other
is for one of the four tests with the bar keel removed.
Figure 19 shows the comparison, at zero model speed,
of the rate of decrease of roll amplitude. Here the
steeper the curve, the more effective is the roll-damping.
The flat bar on the bottom of the keel was not fitted to
the model, due to the small size. A bar such as this,
presenting a horizontal surface, even though small in
vertical area but with four relatively sharp edges to
impede the flow of water from side to side under the
keel as the vessel rolls, would augment the roll-damping
effect of the bar keel.
The late Dwight S. Simpson advocated the use of box
or bar keels of substantial depth, as greatly assisting in
roll damping, for resisting drift, and for improving
directional stability.
[549]
Recent Developments in
Japanese Tuna Longliners
by Jun Kazama
Evolution recente des thoniers palangriers japonais
Les thoniers palangriers japonais, qui operent maintenant dans tous
les oceans, ont fait de grands progres dcpuis 1952. devolution
survenue tant dans les terrains de peche que dans la situation de la
main-d'oeuvre impose maintenant un nouvel effort dc ddveloppe-
ment. La conception des futurs navires s'en ressentira (auto-
matisation de I'appareil prop u I si f, des installations de congelation,
du pilotage, etc.).
Reicentes innovaciones en los palangreros japoneses
Desde 1952 los japoneses ban hecho grandes progresos con los
palangreros del atun, los cualcs operan hoy en lodo el mundo.
Los cambios experimentados por los caladeros y por la mano de
obra reclaman hoy otra etapa de innovaciones, Todo ello influira en
facto res del proyecto de embarcaciones como la propulsion, la
refrigeracion y los aparatos automdticos de gobierno.
SINCE 1952 tuna-freezing equipment has been in-
stalled on Japanese tuna longliners, extending their
fishing range to world-wide coverage and increasing
both the size and number of vessels. The daily catch,
however, has gradually decreased in recent years to an
average of only 2 to 2.5 tons per day, less than half that
of five to six years ago. This has increased the fishing time
per trip and hence increased the expenses and reduced
the profit. This has influenced the design and recently-
constructed vessels show a general reduction in size,
while paying more attention to the quality of frozen
products and methods of reducing manual labour.
CHANGE OF SHIP DESIGN
The recent trend in tuna longliners in Japan is that the
number of small vessels under 40 GT has increased and
the mid water vessels over 300 GT, which were built in
large quantities until 1962, have given place to medium-
sized vessels of 290 to 190 GT (table 1).
The small vessels under 40 GT have been built since
1960 as they were outside the Government restriction.
They were built initially to catch tuna in Japanese home
waters, but then they made longer trips as their numbers
increased, and reached the Midway and the South
Pacific Islands, although many accidents occurred due to
overloading. Under such circumstances, the Govern-
ment included these vessels in the restriction in J964
and started to control the total number and the main
particulars of these vessels. Table 2 shows their principal
particulars.
The number of large midwater tuna longliners over
300 GT has decreased, because the reduction in catching
rate increased the fishing time, hence increasing expenses
and reducing profit. A 340-GT tuna longliner built in
1960 has the following particulars:
L registered .
B moulded .
D moulded .
GT .
Fish holds .
Fuel oil lank
Fresh-water tank .
Complement
Main engine
Service speed
Fish-carrying capacity
Deep freezer
139.40 ft (42.5m)
25.58 ft (7.8 m)
12.46ft (3.8 m)
339.5
14,030 ft3 (397.5m3)
6,530 ft3 (184.9m3)
760ft3 (21.6m3)
32
800 hp diesel
10.5 knots
270 ton
12 ton/day
This vessel was scheduled for a 5,000 sea-mile voyage,
assuming a fuel-oil consumption as follows:
During voyage: 790 gal (3.0 ms) days gal ma
per day
outward 20 1 5,800
homeward 20 15,800
60
60
During fishing: 475 gal (1 -8 m3) days gal
per day
fishing 120 57,000
fish hunting 10 4,750
m
216
18
total (voyage+fishing) 170 93,350 354
Year
39 OT .
40 to 99 GT .
100 to 149 GT
150 to 199 GT
200 to 299 GT
300 to 499 GT
500 GT and over
Total .
TABLE 1 . Tuna fishing vessels launched in the last ten years
7955
8
5
1
4
26
2
46
1956
\
8
~2
16
10
7957
1
4
5
~3
14
9
1958
3
7
6
13
10
1959
25
12
6
1
17
19
6
1960
108
24
3
2
19
42
7
1961
139
25
5
1
66
40
2
1962
40
60
1
6
71
38
5
796.?
39
31
67
55
66
26
2
1964
36
26
23
28
53
13
1
Total
391
198
129
94
314
244
44
37
36
39
86
205
278
221
286
180 1,414
[550]
TABLE 2. Particulars of 39-GT tuna longliners launched in 1960
Wooden construction
Steel construction
Length registered .
Breadth moulded .
Depth moulded .
Gross tonnage
ft(m)
ft (m)
ft(m)
65.10(19.85)
14.34 (4.37)
6.86 (2.09)
39.71
65.10(19.85)
14.76 (4.50)
6.20 (1.89)
39.92
Main engine
Trial speed
Electric generator
Refrigerator type .
Number of crew
B1
riJ/hr
i hp
knots
No. kW
(Kgcal/hr)
D-160
8.34
2-3
NH:, 29,000 (7,300)
J7
D 180
8.58
1-10, 1 3
R,a 13,200(3,320)
18
Fish hold
Fuel-oil tank
Fresh-water tank .
ft3 (mr>)
fta (m3)
ft" (m3)
1,484(42.0)
484(13.7)
117 (3.3)
1,589(45.0)
495 (14.0)
106 (3.0)
Light load A
ton
75.16
69.96
T
ft(m)
5.02(1.53)
3.74(1.14)
cb
0.64
0.67
CM .
ft (m)
1.18(0.36)
2.13(0.65)
Full load A
ton
119.55
110.06
T .
ft (m)
6.86 (2.09)
5.38(1.64)
ch
0.71
0.73
GM
ft(m)
1.21 (0.37)
1.64(0.50)
Freeboard ft (m)
1.30(0.41)
0.99(0.31)
The physical perseverance of crew and fishermen, of
course, enters the question, but the lack of fuel oil
capacity is also a problem. The vessel originally carried
additional fuel-oil (about 7,920 gal (30m3)) in inflatable
bags in the fish-hold on departure, which provided
sufficient fuel-oil capacity when a daily awragc catch of
six tons could be expected.
Now a vessel must cull once or even twice at a port
during the fishing period to refuel, thus adding 10 to 20
days to the trip. It is not so unusual for a vessel of 340
GT to make a voyage lasting over 200 days. Recently,
the Federation of Japan Tuna-Fishing Cooperative
Unions has sent a fuel-oil and fresh-water supply boat
for these tuna vessels around the fishing area in the
Pacific, but has not been able to satisfy all their require-
ments.
This is reflected in the si/c of newly-built vessels in a
tendency to reduce the size of vessels under 300 GT to
290 GT to 190 GT. Midwater tuna longliners, which
had been increasing in size since 1952, have now reverted
to medium size. A special design feature of recent vessels
is in the remarkable increase in breadth (B/D= 2.1 to 2. 2)
because of the raising of the centre of gravity caused by
relocating the refrigerator, originally in the engine room,
10 the deck behind the freezing chamber. The principal
particulars of these medium-sized tuna longliners are
shown in table 3.
These medium-sized vessels also have not sufficient
fuel-oil capacity for the intended range, and carry
additional fuel oil in a specially-constructed fish hold for
this purpose, usually the forward, which holds fuel oil,
in bulk, on departure and fish on return.
TABLE 3. Particulars of medium tuna longliners
Year launched
LBP ....
B moulded
D moulded
Gross tonnage .
Main engine
Trial speed (at MCR).
Service speed (approximately)
Flee, generator .
Aux. engines
Refrigerator
Freezing capacity
Freezing chamber
Freezing lobby .
Fish hold ....
Fuel-oil tank
Fresh- water tank
Light load A ...
ch ". '. :
GM
Full load A ...
T
Cb .
GM .
Freeboard .
Number of crew
ft (m)
ft (m)
ft (m)
hp
knots
knots
. No. KVA
No. hp
BTU/hr (Kgcal/hr)
ton/day
ft:' (nr!)
ft3 <nv<)
ft3 (m3)
ft" (m3)
. ft3 (mr<)
. ton
ft (m)
ft (m)
ton
ft (m)
ft (m)
190 GT
1964
109.55 (33.40)
22.63 (6.90)
10.34 (3.15)
192.95
D-650
12.03
10.0
2-60
2-80
2: 362,300(91,300)
4.0
1,250 (35.4)
696 (19.7)
6.960(197.2)
4,595 (130.2)
658 (18.6)
267.71
6.05(1.844)
0.622
1 .64 (0.50)
465.62
9.52 (2.902)
0.689
1.41 (0.43)
1.44(0.44)
26
250 GT
1964
125.00 (3X.10)
24.60 (7.50)
10.99 (3.35)
253.96
D 800
12.02
10.7
2 80
2 100
1x494,100(12,450)
1x362,300(91,300)
6.4
1,906 (54.0)
862 (24.4)
10,490 (297.0)
5,185(146.8)
652 (18.5)
322.22
6.05(1.843)
0.606
2.23 (0.68)
602.03
10.02 (3.055)
0.681
1.73(0.53)
1.60(0.49)
28
2^0 GT
I9f>3
134.50 (41. (X))
25.27 (7.70)
11.48 (3.50)
294.84
D 750
12.21
10.5
2 80
2 105
1 .-' 41 6,300 ( 104,900)
1x34,600 (87,300)
7.5
2,143 (60.7)
579 (16.4)
12,400(351.1)
5,980(169.3)
955 (27.1)
329.96
5.63(1.716)
0.587
2.20 (0.67)
695.31
10.59 (3.229)
0.676
2.26 (0.69)
1.52(0.46)
29
[551
TABLE 4. Particulars of large tuna longliners with catcher boat
880 GT
1,500 GT
2,800 GT
Year launched
1963
1962
1963
LBP . ft (m)
186.40 (56.80)
238.90 (72.80)
288.80 (88.00)
B moulded
ft(m)
36.10(11.00)
42.00 (12.80)
48.60 (14.80)
D moulded
ft (m)
16.40 (5.00)
18.70 (5.70)
19.68 (6.00)
Gross tonnage
886.98
1,490.50
2,801.32
Main engine
hp
D-1,600
D-2,200
D-2,400
Trial speed (at MCR)
knots
13.79
14.79
14.10
Service speed
knots
*12.0
*12.5
*12,5
Hlec. generator
No. KVA
2x200, ix 90
2x300, 1x80
3x300
Aux. engines
No. hp
2x240,1x110
2x360, 1 xlOO
3x360
Refrigerator
BTU/hr
3x805,000
3x1,167,300
4x1,167,300
(Kgcal/hr)
(202,800)
(294,100)
(294,100)
Freezing capacity
ton/day
22.5
40.0
60.0
Freezing chamber
Freezing lobby .
ft* <m:')
ft" (m:j)
5,850(165.7)
1,885 (53.4)
11,200(317.1)
3,135 (88.8)
20,980(591.0)
13,210 (374.4)
Fish hold .
ft3 (m3)
42,400(1,201.6)
79,600 (2,254.2)
119,900(3,394.3)
Fuel-oil tank
ft;} (nv<)
15,700 (444.7)
24,120(683.3)
48,9500,386.2)
Fresh -water tank
ft" (m3)
2,225 (63.0)
4,340 (125.6)
6,130(170.7)
Light load A
. ton
852.0
1,270.4
2,048.9
T .
ft(m)
7.25 (2.209)
7.40 (2.256)
8.22 (2.507)
Cb .
0.610
0.585
0.619
CM
ft (m)
3.45(1.05)
6.00(1.83)
4.63 (1.41)
Full load A
. ton
1,923.0
3,278.2
5,274.4
T
ft (m)
14.05 (4.285)
16.24(4.948)
15.20 (4.635)
Ch .
0.700
0.693
0.685
GM .
ft (m)
3.45(1.05)
4.140.26)
4.630.41)
Freeboard
ft (m)
2.80 (0.85)
2.93 (0.89)
1.67(0.51)
Number of crew
63
112
148
Number of catcher boats
2
4
6
* Approximately.
About ten years ago, a tuna longliner mothership was
designed, that carried catcher boats on board and un-
loaded them in the fishing area. This mothership was
1,800 GT and had six catcher boats of 13 GT each.
Since then, about 46 such vessels have been built with
two to six catcher boats each. The motherships were 800
to 3,000 GT and the catcher boats, of wooden or steel
construction, were mostly 19.9 GT, which is the upper
limit of restriction by the Fisheries Law. The number of
catcher boats is generally as follows:
Mothership
700 to 800 GT .
UOOto K500GT
over 2,000 GT .
Catcher boats
. 2xl9GT
4xl9GT
6xl9GT
Fig I. Recent 5QO-GT tuna hngliner
The particulars of these and the catcher boats are
shown in tables 4 and 5 respectively. In the light con-
dition, a catcher boat of wooden construction weighs
about 25 to 30 tons, and one of plywood and steel con-
struction about 19 tons. Therefore the mothership must
be equipped with a heavy derrick arrangement, usually
consisting of two derrick posts, four derrick booms and
four cargo winches of three to five tons at 100 to 130
ft/min (30 to 40 m/min). Therefore, the stability may be
insufficient, especially in the case of small-sized vessels.
TABLE 5. Particulars of catcher boats on board tuna fishing vessels
20 GT
20 GT
20 GT
19 GT
Construction
Wooden
Plywood
HT Steel
*FRP
LBP . ft(m)
52.50(16.00)
52.50 (16.00)
49.20(15.00)
49.20(15.00)
B moulded
ft(m)
11.78 (3.60)
11.94 (3.65)
11.45 (3.50)
11.78 (3.60)
D moulded
ft(m)
5,42 (1.65)
4.99 (1.52)
4.76(1.45)
4.99 (1.52)
Fish hold
ft3 (m3)
424(12.0)
593 (16.8)
424(12.0)
325 (9.2)
Fuel oil
ft3 (m3)
52 (1.5)
53 (1.5)
49 (1.4)
57(1.6)
Fresh-water
fta (m3)
18 (0.5)
11 (0.3)
14 (0.4)
11 (0.3)
Main engine
hp
D-90
D-90
D-90
D-120
Weight . . ton
25.0
19.8
19.9
13.4
Fibreglass reinforced plastic.
[552]
Fig 2. Recent 500-GT tuna longliner
Recently a vessel, under 500 GT, carrying a catcher
boat of 19 GT on board, was designed to cope with the
recent decrease in catch. The stability on the voyage with
a catcher boat on board is no problem, but it is some-
what dangerous when the vessel hauls or lifts the catcher
boat at sea, sometimes causing a large heel with the
deck-edge immersed. So far, however, no accidents have
occurred (fig 1 and 2).
It is essential to reduce the weight of catcher boats in
the case of these motherships. In 1965 a catcher boat
with a fibre-reinforced plastic hull was built for this
purpose. It weighs about 13 tons, only two-thirds that
[553
of steel or plywood construction. The derrick arrange-
ment weight has also been reduced, giving a considerable
decrease in the heeling. The success of this catcher boat
gives good future prospects for this design and it may
come into wide use.
FISH HOLD AND REFRIGERATION
Small tuna longliners under 100 GT have not yet gener-
ally been installed with deep-free/ing equipment, but
with ice cooling and auxiliary refrigeration. This is
because of the lack of available space to install a deep-
freezer with sufficient capacity for preserving the daily
catch, and also the length of voyage and size of vessel
hardly warrant it.
Tuna vessels over 100 GT are generally installed with
a deep-freezer with a capacity of 4 to 10 tons per day.
Some 110-GT vessels have the freezing chamber below
deck, but in vessels of over 190 GT it is mostly installed
on deck. This is generally a semi-airblast freezing system,
although occasionally Ottesen's salt-brine system is used.
The semi-airblast system is considered the most suitable
because the frozen tuna are sold in a round or semi-
dressed state. The salt-brine system is not favoured,
although it is labour saving. Salt-brine frozen tuna has a
lower market price in Japan.
The refrigerant for the deep-freeze and the hold
refrigeration is usually ammonia gas, the direct-expansion
system. Others, such as the indirect or Freon gas direct
system, are scarcely used because the ammonia direct-
expansion system has a higher freezing efficiency and
lower running costs.
Fish-hold refrigeration is generally done with hairpin
coil evaporators on the bottom, walls and ceiling of the
holds. The airblast freezer in the freezing chamber con-
sists of evaporator coil racks and power air blowers. The
installation standard for the semi-airblast system of
Japanese fishing boats is given in the Fishing Boat
Inspection Regulation by the Government as follows:
Deep freezing
3
5
10
'pacitv
BTU/hr
144,800
238,100
Refrigerator
capacity
(kgcal/hr)
36,500
60,000
Evaporator
cooling surface
ft2 ' m2
860 80
1,450 135
460,300 116,000
2,900
270
Frozen fish-hold refrigeration
Hold capacity per Refrigerator
Evaporator
compartment capacity cooling surface
ft3 m3 BTU/hr (kgcal/hr) ft2' m2
1,770 50 61,500 15,500 707 65.7
3,530 100 86,500 21,800 1,010 93.8
5,300 150 105,600 26,600 1,211 112.5
7,060 200 115,500 29,100 1,328 123.4
The above standard has been unaltered since 1959
(Doke and Chigusa, 1960). However, the temperature
standard has changed; from -22°F to -40°F (-30°C
to -40°C) in the freezer chamber and from 0°F to
- 1 3°F ( - 1 8°C to - 25°C) in the storage hold, to improve
the quality of frozen tuna products.
In these few years, defrozen tuna meat had as good a
market in Japan as fresh raw meat, indicating the high
quality of frozen tuna. To meet these requirements, the
majority of recent tuna longliners have increased the
length of evaporator coils in the fish-hold and freezing
chamber by 20 to 30 per cent and have thickened the
insulation materials by 1.0 to 2.0 in (25 to 50 mm). The
refrigerators also have increased in capacity by about
50 per cent and some vessels have used an additional two-
stage system and /or refrigerant liquid pumps.
A contemporary NH3 refrigerating system installed in
a 250-GT tuna longlincr is shown in fig 3.
PROPULSIVE MACHINERY
The majority of propulsive machinery installed in
Japanese tuna longliners is of slow rotation, four-stroke,
vertical trunk piston-type diesel, with turbo-supercharger.
The outputs of these engines are comparatively high for
the vessels' size:
GT
39
110
190
250
350
500
hp
160 to 250
400 to 450
550 to 650
700 to 800
800 to 1,000
1,300
rpm
400 to 450
385 to 430
340 to 390
340 to 380
310 to 330
290 to 310
Engines with an output less than 450 hp generally
have reversing gears, and those over are self-reversible
with the friction clutch between flywheel and thrust
shaft. The mean effective pressure in cylinder of these
engines is generally 106.6 to 156.5 lb/in2 (7.5 to 11
kg/cm2). The engine is cooled by seawater circulation
and only rarely by fresh water. Table 7 shows an example
of the propulsive engines installed recently.
The tuna longliner must steam, while fishing is in
progress, at a speed of four to five knots, because the
most suitable hauling speed of fishing line is believed to
be 40 to 50 baskets of lines, or 39,400 to 49,300 ft (12,000
to 15,000 m) per hour. The vessels, however, may have a
speed of six to seven knots even at the lowest revolutions,
TABLE 6. A contemporary NH9 refrigerating system installed in a 250-GT longliner
Refrigerator (2 stage compressor)
3 cylinders, 2-stage compressor, 45 kW motor
Refrigerator
2 cylinders, 30 kW motor .
Condenser, shell and tube
Cooling water pumps, 2.2 kW motor
Liquid receivers, vertical
Oil separators, „
Accumulator, „
Oaspurger,
Intercooler, „
Electric axial flow fans for quick-freezing room, 1.5 kW motor
Thermometer, electric-resistance system ....
2x7.09x5.51 in (180x1 40 mm)
1 x 5.91 x 5.51 in (150 x 140 mm)
1 set
2x7.09x5.51 in (180x140 mm) 1 set
329 ft3 (30.6 m2) xlset
230 ft2 (21. 4m2) xl set
1,059 ft" (30 mfj)/hr x 39.4 ft (12 m) x 2 sets
21. 5 ft3 (0*610 m3)
12.5 x 35.4 in (318 x 900 mm)
14x41.4 in (355 x 1,050 mm)
8.5x23.6 in (216x600 mm)
12.55 x 66.6 in (319 x 1,690 mm)
-58°to860F(-50°to30fC)
x 2 sets
x 2 sets
x 1 set
xl set
xl set
x 8 sets
x 1 set (20 points of elements)
[554]
II in i n
j
ifi in i n
1 Ml
[555]
Model
hp
rpm
TABLE 7. Specifications of propulsive machinery for tuna longliners
No. Diam.of « . Weight of
of cylinder *troKe engine
Weight of engine
per hp
cyl.
in
mm
in
mm
Ib
ton
Ib
kg
27/40
600
390
6
10.6
270
15.8
400
22,700
11.2
39.8
18,1
32/45
650
350
6
12.6
320
17.7
450
39,500
17.9
60.8
27.5
30/42
700
370
6
11.8
300
16.5
420
34,850
15.8
49.8
22.6
28/44
750
380
6
11.0
280
17,3
440
32,400
14.7
43.2
19.6
32/45
750
350
6
12.6
320
17.7
450
40,800
18.5
54.4
24.7
33/46
850
330
6
13.0
330
18.1
460
39,900
18.2
47.0
22.4
35/50
1,000
330
6
13.8
350
19.7
500
48,500
22.0
48.5
22.0
37/52
1,000
320
6
14.6
370
20.5
520
58,400
26.5
58.4
26.5
40/57
1,300
290
6
18.8
400
22.4
570
69,000
31.3
53.1
24.1
and therefore they maintain the speed of four to five
knots by means of an on-and-off clutch, which may
sometimes be used over 30 times per hour. This un-
economical and troublesome procedure has been normal
practice for a considerable time.
Recently the controllable pitch propeller (cp) has
been widely introduced. The cp was initially used
about ten years ago on several tuna longliners, but it
was not widely accepted because some vessels met with
serious trouble due to the entanglement of the fishing
lines around the shaft between the propeller boss and
the aft end of the stern tube. In recent years it has
become really popular due to the simplification of the
pitch control mechanism and reduction in costs. About
one-fifth of recent vessels use them and are satisfied with
the easy control of the ship's speed during iishing. A
clutch is still installed between flywheel and thrust shaft
for the purpose of disentangling the fishing lines around
the propeller shaft.
The remote control of the main engine is also widely
used, together with cp. Many systems have been
developed, utilizing mechanical, compressed air, electric
and electro-hydraulic, for remote control of engine
revolutions, starting, stopping and reversing. The most
popular systems are electric or electro-hydraulic with the
remote control panel and measuring instruments situated
in the wheelhouse adjacent to the autostecring stand.
Lately, medium-speed diesel engines of 600 to 800
rpm with reduction gear, as well as high-speed genera-
tor engines, have been used and have saved space. These
geared diesel engines, however, are not yet widely used
because of their poor durability. Midwater tuna long-
liners are obliged to go on long trips and the main engines
must run continuously for quite long periods, very often
over 4,000 hours. The most durable, heavy-duty, slow-
speed diesels, therefore, are still preferred by the majority
of midwatcr tuna longliner owners, and only a few
vessels with small engines, less than 650 hp, have used
geared diesel engines. Table 8 shows an example.
METHODS TO REDUCE MANUAL LABOUR
Modern tuna longliners normally have the following
crew and fishermen on board :
GT
39
190
250
290
350
450
Crew and fishermen
18
26
28
30
32
34
The number of crew has not changed over the past
five to six years. On the other hand, the daily average
catch has decreased. These vessels are therefore forced
to extend the duration of the trip and thus increase the
expenses. To offset this, the owners try to reduce the
crew and fishermen by reducing their manual labour.
This is currently a serious problem for all the fishing
industry and particularly the Japanese tuna fisheries. A
committee has recently been organized to investigate this
problem. It consists of the Fisheries Research Institute,
the Federation of Tuna- Fishermen Cooperatives, fishing
firms, fishing boat builders and machinery manu-
facturers. The tentative recommendations for study by
the Committee are:
• (a) Mechanization of fishing operation
• (b) Automation for freezing tuna
• (c) Automatic control of engine and steering
(a) It is quite difficult to mechanize the whole fishing
operation, namely the throwing of lines, buoys, hooks
and bait from the ship's stern in three to four hours,
hauling them back with the catch on the fore deck in
12 to 14 hours and conveying the lines and buoys from
the fore deck to the aft deck. The mechanical equipment
now used is the power-driven line hauler and a conveyor
belt for longlines and buoys after hauling. The Com-
mittee has investigated the possibility of using an
Model
hp
TABLE
rpm
8. Specification of medium-speed
No Diam. of
of cylinder
propelling machinery for tuna longliners
W3K?
Weight of engine
per hp
cyl
in
mm
in
mm
Ib
ton
Ib
kg
16/20
260
1,200
6
6.3
160
7.9
200
7,500
3.4
28.8
13.1
20/26
420
800
6
7.4
200
10.2
260
14,550
6.6
34.7
15.7
20/26
420
900
6
7.9
200
10.2
260
15,000
6.8
35.7
16.2
25/32
650
720
6
9.8
250
12.6
320
22,700
10.2
34.9
15.7
[556]
automatic throwing machine for the lines and bait, a
power winding reel for the lines after hauling or a
complete conveyor system for the lines and buoys from
line hauler to the after-casting platform. Automating
the whole operation presents certain difficulties because
the rate of flow of the fishing gear is not constant, as it
is entangled by the movement of tuna. Therefore the
design of the fishing lines themselves may also have to
be studied in respect of material, hardness and swivel
arrangements, etc. The Committee has not yet reached a
definite conclusion on this.
(b) The question is which freezing system is preferable:
salt-brine or airblast? The salt-brine system requires
little labour compared with the airblast system, but may
not be accepted because the salt-brine frozen tuna has
a poor market value in Japan. On the other hand, the
airblast system produces better quality frozen tuna, but
requires much more labour and space. Thus the Com-
mittee faces two problems; firstly how lo improve the
quality of salt-brine produce for good market prospects,
and secondly how to automate the airblast freezing
system to reduce labour and to obtain compactness.
(c) The majority of tuna longliners have already been
installed with automatic steering control and the main
engine remote-control systems, but even if completely
automatic machinery control is applied, there is little
chance of reducing labour, because most of the crew are
absorbed in assisting in the actual fishing operation and
not in handling the ship.
CONCLUSION
Modernization of Japanese tuna longliners is now being
closely studied, aiming at the most economical operation
with the least labour and expense. This may give rise to
an entirely new type of midwater tuna longliner, with
advanced mechanization of fishing gear and fish pro-
cessing plant.
[557
Development of Japanese
Stern Trawlers
by Tatsuo Shimizu
Evolution des chalutiers japonais a peche par Tan-tore
L'auteur expose revolution generate ayant abouti au ehalutier
japonais moderne £ peche par 1'arriare, en soulignant Ic grand role
joue par la n6cessit6 d'aller pechcr de plus en plus loin pour satis-
faire la demande accrue. 11 decrit la technique moderne de construc-
tion, examinant les moteurs, I'amenagcment du pont, certains
parametres de formes, le profil du tableau arriere, tant au-dcssus de
la ligne de flottaison qu'au-dessous dc la voute, et les divers types de
gouvernail, Apres avoir ctudie plus a fond les appareils propulsifs,
Pauteur traite de la commande des treuils de peche, de la longueur
du pont de travail, des emmenagements, et du fonctionnement du
treuil de peche. Sont ensuite abordes les chalutiers d'une jaugc brute
de 300 tonneaux et leurs caracteristiques les plus marquantes:
moteurs de grande puissance, treuils de peche, helices a pas variable.
L'auteur passe ensuite bri eve merit en revue les grands navires
usines jaugeant de 3 000 d 3 500 tonneaux, ct terminc en traitant de
Involution future.
Arrastreros japoneses que pescan por la popa
Se examinan los antecedentes del proyecto de modernos arrastreros
japoneses quc pescan por la popa, con el gran efecto resultante dc
verse forzados a pescar muy lejos para hacer frente al consume.
Se pasa a describir la practica moderna de la pesca, con un examen
general de los motores, el trazado de la cubicrta, algunos parametros
de la forma del casco, el perfil vertical de la popa de espejo, sobre
el agua y bajo la bovedilla, y la disposition del timon. Se estudian
mas detenidamente las maquinas propulsoras, y siguen capitulos
dedicados a las maquinillas de arras t re, la longitud de la cubierta de
faena, los alojamientos y el funcionamiento de las maquinillas de
arrastre. Se examinan arrastreros de 300 toneladas brutas y sus
caractcristicas peculiarcs mas importantcs, como los motores de
propulsion y maquinillas de arrastre muy potentes y las helices de
paso variable, Luego se analizan sucintamcnte buques factorias de
mayor tonelaje (3.000-3.500 toneladas brutas). Por ultimo se
discuten futuras innovaciones.
WHEN the Japanese trawler fisheries were
searching for new overseas fishing grounds to
expand operations beyond the region of the
East China Sea and Japanese waters, where fishing until
then had been prosperous, a study of European stern-
trawling techniques was first undertaken. In 1955 the
training ship, Umiiuka Maru, of Tokyo University of
Fisheries was then built, following closely the design of
a European stern trawler. In 1957, the Taiyo Mam No. 57,
a larger trawler, was built by a Japanese firm, but as the
data on stern-trawler construction was still insufficient it
was planned that the vessel would serve both as a deep-
sea trawler and as a carrier for the Antarctic whaling
industry. This design proved so successful, however, and
such good results were obtained by the two vessels in
the North Pacific and New Zealand waters that about
30 stern trawlers of 1,500 to 2,500 GT were launched by
Fig 1. Sankichi Maru No. 51, 299 GT
Japanese fishing companies during the years 1960 to
1963. These trawlers not only operate in waters off the
North-West African coast and transport their catch to
Japan, but are also required to process frozen fish for
export, meeting the various consumption requirements
peculiar to the importing countries.
Large trawlers were developed with the capacity of
operating for long periods in distant waters. They were
fully equipped with filleting machinery and meal plant
to produce various finished products with the minimum
of wastage. In 1964 designs were so improved in the
2,500 to 3,500 GT range that adequate space to accom-
modate essential maintenance personnel and equipment
was available. From an economic aspect the larger the
trawler the larger must be the catch which can only be
acquired from deep water fishing grounds, entailing
heavier duty trawl winches.
Stern trawlers of 300 GT were also built by lesser
Japanese fishing companies for operation mainly in the
North Pacific utilizing a powerful trawl winch and main
engine. Their small size naturally restricted their opera-
tional range and they operated more efficiently working
co-operatively with a factory vessel rather than as
individuals. Due to seakceping considerations, and
hence working conditions aboard, it was necessary to
increase their size to 500 GT. The general appearance of
typical stern trawlers is shown in fig 1 to 4, and main
particulars given in table 1.
TYPE AND SIZE OF VESSEL
The initial consideration in designing a stern ramp
trawler is the position of the main engine aft or amidships.
Japanese trawlers operate far from their home ports and
[558]
TABLE 1 : Typical Japanese stern trawlers, 300 to 3,500 GT
Nan* of ihip
GT
L
ft m
B
ft B>
D
ft B
Diml
hp
Tear
built
Crtw
COMpl«-
atnt
Hold
capacity
ft3 B?
Sharp
fretzing Trawl winch
capacity capacity
Sankiohi Maru Ho. 51
(fig 1)
Chuyo Maru No. 7
(fie 2)
Ebiau Maru
299
299
314
123.0
124.5
128.5
37.6
38.0
39.2
26.6
26.6
26.2
6.0
6.1
8.0
11.8
12.6
11.6
3.6
3.9
3.6
4 x 66
lew motor
1,000
1,000
1964
1965
1964
32
25
29
9,650
10,950
10,700
273
310
303
6.7T/E
6.7 "
16.0 "
6t x 197ft (60m)
7t x 262ft (BOa)
7t x 262ft (80m)
Fukuyo Maru Mo. 1
314
132.0
40.2
26.2
8.0
12.6
3.9
1,200
1965
24
11,800
334
6.2 "
7.5t x 262ft (60m)
Ak«bono Maru No. 50
1,425
255.0
72.6
39.4
12.0
16.7
^.7
2,000
I960
87
54,800
1,550
40.0 "
lOt x 213ft (65m)
Taiyo Maru Ho. 61
1,497
226.0
69.0
37.4
11.4
18.7
5-7
1,600
1957
70
56,000
1,588
37.5 "
72 t x 148ft (45a)
Taiyo Maru Ho. 65
1,626
230.5
70.3
39-4
12.0
27.2
6.3
2,OOO
I960
67
69,600
1,971
24.0 "
13t x 141ft (43m)
Taiyo Maru No. 75
2,160
243-5
74.2
42.0
12.8
28.5
8.7
2,470
1963
74
6?, 600
1,772
30.0 "
13t x 197ft (60m)
Kiio Maru
2,52?
260.0
79.2
44.3
13.5
29.2
8.9
2,750
196J
75
84,100
2,380
J%0 "
20t x llbft (3!>m)
UxiB«n Maru
(fie 4)
Taiyo Maru No. 81
2,525
2,807
260.0
269.0
79.2
82.0
44.3
46.0
13.5
14.0
28.5
30.2
8.7
9.2
2,400
2,880
1961
1<M
70
99
86,000
70,600
2,435
2,000
33.2 "
48.6 "
24t x 148ft (45m)
18. 6t x 197ft (60m)
Balshin Maru No. 12
2,967
269.0
68.1
48.6
14.9
2J.6
7.2
5,380
1963
85
122,000
3,457
!>2.0 "
15t x 197ft (60m)
Zuiyo Maru
(fie 5)
Takaohiho Maru
(fig 6)
2,970
3,495
269.0
292.5
82.0
89.2
46.0
52.5
14.0
16.0
30.2
24.0
9.2
7.3
?,880
3,710
1964
1964
112
104
68,700
ID.OOO
1,945
3,483
62.0 "
55.0 "
19. 7t i 216ft (66m)
23t x 230ft (70m)
therefore the ratio of fishing to voyage time needs to be
considered when fixing the refrigeration, refrigeration
hold, fuel oil, fresh-water tank and provision store
capacities. A sufficient after draft for aii loading con-
ditions must also be considered. To satisfy these con-
ditions the following arrangement is indicated: fat amid-
ship for fish hold, fore peak and double bottom for fuel
oil tank and the remainder engine room. This is a
description of the engine aft type. A problem is the
location of the engine casing and funnel. A large engine
casing will reduce the fish treatment space on the shelter
deck and a centre-line funnel will complicate the trawl-
winch layout. With the exception of the prototype vessel,
the Taiyo Maru No. 57, this was solved by adopting a
layout similar to a whole factory ship, that is the engine
casing reduced to a minimum in way of the shelter deck
or the casing and funnel divided longitudinally and sited
at the sides of the deck. Apart from the prototype, there-
fore, all large Japanese trawlers have been built with
engine and shelter deck aft.
In general, Japanese large stern trawlers have larger
L/B values in the range 5.7 to 6.0, whilst other countries
tend to the range 5.5 to 5.7, but the latest factory trawler
of about 3,000 GT has a smaller L/B ratio to accom-
modate factory equipment. The block coefficient of
Japanese trawlers also tends to be higher when composed
on deadweight. This means that some loss in com-
parative ship's speed is inevitable.
For ease of sliding up the otter boards, the transom
was inclined slightly forward, but with the increase of
deep-sea trawling, this slope has become vertical or
even inclined aft, thus permitting the trawl net warp to
come up almost vertically on to the top roller and so
avoid faying on bulwark roller. The engine aft allows a
constant after draft to be maintained although it has
been noticed that this type of vessel suffers from panting
under the counter when the midship hold is empty. The
increase in tow-rope force required has a tendency to
increase the engine power, hence decreased propeller
revolutions and increased propeller diameter. This
necessitates a raising of the counter and decreases the
stern immersion which increases the susceptibility of
panting in heavy seas. To avoid this, either the after
Fig 2. Chuyo Maru No. 6, 299 GT
draft must be increased or a spade-type rudder, as in the
British stern trawler Ross Valiant, must be introduced.
To help the net-hauling operation the after end of the
stern ramp is to some extent submerged, giving a corre-
sponding increase in total ship resistance, but this is
found to be negligible.
TYPE OF ENGINES FOR PROPULSION
Most Japanese stern trawlers have single direct engines
but some European trawlers on the other hand use
diesel-electric propulsive systems. There is hesitation in
Japan in using this system because of the following
reasons when compared with single direct engines:
[559]
• Higher installation costs and fuel costs
• Larger engine room required
• Insufficient working knowledge and practical
experience
The Japanese Fisheries Agency is proposing a proto-
type guidance vessel with dicsel-electric system. The
"Father and Son" and other systems are also under
consideration. Most Japanese trawlers built since 1953
are equipped with remote control from the wheel house
to the engine room and some are equipped with auto-
matic systems for fuel oil purification and refrigeration.
TRAWL WINCH
The type of trawl winch required, whether it be electric
or electro-hydraulic drive, and in the latter case, high or
low pressure, is decided by the cost and the winch
characteristics. It is difficult, therefore, to reach any
definite conclusions as to a best type. Initially electric
drive was used and since then almost all vessels have
been equipped with AC motors for trawl winches. The
AC motor as it stands is unsuitable for this purpose
and low pressure electro-hydraulic drive was adopted.
With the expansion of deep sea trawling, higher winch
winding speeds were necessary. To adapt the low
pressure system is not simple because of the large pump
room required, so recently AC Kraemer type electric or
high pressure electro-hydraulic systems are used. The
trawl winch capacity is calculated from the maximum
intended trawling depth and size of net. Winches of
current stern trawlers have capacities of 1 2 to 23 tons x
295 to 197 ft (90 to 60 m) wire speeds per minute.
Fig 3. Fukyo Maru No. 7, 314 GT
NOTES ON GENERAL EQUIPMENT
Working deck
The advantage of having engines aft is in providing
ample working deck length if the disposition of the engine
casing can be correctly adjusted. The distance between
the upper edge of the stern slipway to the trawl winch
is some 100 ft (32.8 m) for 1,500 GT and 130 ft (42.7 m)
for 3,000 GT vessels. To obtain this the bridge must be
well forward and, consequently giving a centre of wind
pressure well forward, this has the disadvantage of pro-
ducing a tendency to drift to leeward. To overcome this
the working deck length for even a large vessel is se-
stricted to about 100 ft (32.8 m).
Accommodation space
Processing and refrigeration equipment occupy much
space in Japanese distant-water trawlers. This equipment
demands a larger crew to operate it than is common in
other countries, so adequate accommodation space is
necessary. A factory trawler has a crew complement of
110 to 130, therefore any reduction in this number by
adopting automatic control systems is desirable. Hence
automation and accommodation should be studied as
interdependents.
Fig 4. Unzcn Maru, 2J25 GT
Trawl winch operations
Most trawl winches are side operated but in several large
trawlers control rooms have been situated just aft of the
bridge with the clutch and brake operated by pneumatic
remote control. Depending on the ship's operational
area, care must be taken not to lose the net by snagging
on natural underwater projections. For this purpose an
alarm system, triggered by excessive strain on the warps
and recorded in the bridge and control room, has been
installed. This is remotely recorded by an oil-pressure or
wire resistance strain gauge at the top roller of the
gallows or on the rope way of the warp. This is now
under practical proving tests in u large stern trawler.
300-GT TRAWLER
In 1960 the Japanese Government allowed trawlers to
operate in the North Pacific and trawlers of such small
displacement were neglected. In 1962, however, the
Chuyo Maru No. 5 was built and has had a favourable
reception. After consideration, the main engine was
fixed amidship and the long fo'c'sle accommodated the
after part of the engine room, this caused a reduction in
working space but not accommodation. From 1963 to
1965 ten more stern trawlers of 300 GT have been built,
equipped with more powerful engines and trawl winch
when compared with the ship's size and also controllable
pitch propellers. These were designed as independent
middle-water trawlers, with heavy catches on short
[560]
voyage times, and fishing period. The main engine was
800 to 1,200 hp. For the engine aft type, a compact
engine was essential and so the geared diesel was the
obvious choice. The controllable pitch propeller and
power trawl winch enable a steady winch rotation which
is oil-pressure-driven from the main engine.
*«A< . v"t^
Fig .5. Zniyo Maru, 2,970 GT
Basically, three types have been developed:
• Shelter deck
• Hnginc midship with long fb'c'sle
• Engine aft with long foVslc
The Sankichi Maru No. 57, built in 1964. has a dicscl-
elcctric propulsive unit with two three-phase motors,
reduction gearing and a controllable pitch propeller.
JAPANESE FACTORY TRAWLERS
With trawlers being forced to fish in more distant waters,
it was necessary to increase the size of vessel, to increase
the lish hold capacity and to still maintain an economic
proposition. Nowadays, in order to maintain the full
edible standard of the catch, the relay base system,
which has come to be possible with co-operation from
other nations, has been established, and whilst fish for
domestic consumption is washed and then frozen whole,
fish for export is processed almost to fish block. Non-
processibte fish and fish offal arc profitably reduced to
meal. For this purpose, full processing factory trawlers
of 3,000 to 3,500 GT, equipped with Baader and meal
plant, began to be built by 1963.
EXAMINATION OF FUTURE DEVELOPMENTS
Large factory trawlers are expensive and can make no
commercial profit unless they are fully utilized because
of the installations and large crew required. It appears
that vessels specially designed and equipped for a
specific fishing ground must be considered. This would
enable a minimum of equipment to be installed. A
careful analysis should be made, therefore, of the specific
area in respect of depth of water, prevailing weather and
sea conditions, types of fish and associated processing
and the marketing possibilities.
Fig 6. TakacMho Mont,
CiT
Wages and living standard in Japan have risen, and
better accommodation must be provided because of the
long periods at sea. Simplification of handling vessels,
fishing and factory operation must be studied seriously.
This is without mentioning the obvious need for im-
proved fish gear. It is, therefore, necessary to look well
ahead and to attempt to forecast future requirements, by
studying both private and national economics. The plan
for building a large guidance vessel for the investigation
of fishing grounds arouses great interest.
561
Small Stern Trawlers
by W. M. Reid
Pet its chalutiers Canadiens & pgche par Tarricre
Apres avoir fait 1'historique des petits chalutiers modernes £
peche par 1'arriere de la cote nord-est du Pacifique et decrit le
milieu dans lequel ils opercnt, 1'auteur gtudie les deux principaux
types de chalutiers arriere sans rampe, Tun convenant aux engins
pour fonds mous, 1'autre aux engins pour fonds durs. 11 d£crit
ensuite 4 types de petits bateaux £ rampe arriere, caract6ris6s par la
methode d'embarquement du chalut: (a) corps du chalut laissg dans
1'eau; (b) embarquement des ailes sur les deux bords; (c) em barque-
men t des deux ailes sur un bord; (d) embarquement du chalut
cnticr sur la rampe au moyen d'un tambour; et conclut en passant
en revue revolution future du dessin des chalutiers.
Pequenos arrastreros de popa canadienses
La historia y las condiciones de operaci6n ambientales de los
modernos arrastreros pequeftos para la pesca por la popa, en la
costa del Pacirico Noreste plantea una discusion sobre los dos
tipos principals dc los referidos arrastreros sin rampa, uno apto
para artes de pesca en fondos lisos, y el otro para artes de pesca en
fondos accidentados. Sigue una descripci6n de cuatro tipos de
pequeflos barcos con rampa en la popa, caracterizados por sus
m&odos de manipulaci6n de las redes: (a) dejandolas en el agua,
(b) recogiendo las pernadas por una y otra banda, (c) recogiendo
las pernadas por una banda, (d) combinando la rampa y cl tambor.
Por ultimo, se estudian las futuras tendencias del disefio.
WHILE the term "stern trawling" is of fairly
recent origin and is generally taken to
mean those vessels which tow and recover the
trawl over the stern, as opposed to those which tow and
recover the trawl from the side, there exists on the
Pacific coast of Canada and USA a very large fleet of
small stern trawlers or draggers, 45 to 90 ft (13.7 to
27.4 m) length overall, which have combined the best
features of these two systems of fishing for more than
30 years.
It has been normal practice to tow the trawl with
warps leading to davits (gallows) located one at each
stern quarter of the vessel, exactly as the modern stern
trawlers, with the exception that the codend is lifted
over the side for emptying.
This system of handling the trawl may have been an
inheritance from Mediterranean fishermen who migrated
to the Pacific coast after 1918. Many improvements in the
mechanical handling of gear has increased the efficiency
to a level of productivity equal to vessels many times
their size.
For over 20 years the author has been designing
fishing craft up to 100 ft (30.5 m) (about 180 GT)
operating on the west coasts of Canada and USA.
Knowledge of this vast area is essential to understand
the factors influencing the development of the "Pacific
coast" type of vessel.
The sketch map, fig 1, shows the north and west
coasts of Washington, British Columbia and Alaska,
extending through the Bering Sea to the eastern coast
of the USSR. This clearly shows the extensive and rugged
coastline along which these vessels operate. To illustrate,
the airline distance between the major British Columbia
fishing ports of Vancouver to the south and Prince
Rupert to the north is some 500 miles (825 km); how-
ever, the actual coastline between these two points has a
total length of nearly 13,000 miles (24,000 km).
The climate is generally mild, being influenced by the
Japanese Current. Harbours are usually ice free to well
Fig L The fishing boats with wheel house and engine forward used on
the Pacific Coast of Canada and USA are operating along an
extensive and rugged coast line
above 55° north although heavy snowfalls and fog are
common.
Tides range from —2 to+16 ft (0.61 to 4.87 m) at
Vancouver to —2 to +26 ft (0.61 to 7.92 m) in south-
east Alaska. Tidal velocities tend to be strong, averaging
3 to 6 knots in the Hecate Strait trawling grounds.
A most unusual phenomena along the entire coast is an
ocean ground swell, running in from a generally westerly
[562]
Fig 2. The typical Pacific groundswell very often shows a lack of wind generated waves
direction. This is a long, lazy swell, varying slightly with
location and season but usually from 4 to 6 ft (1.2 to
1.8 m) in height and wave length up to 350 ft (110 m) in
open sea. However, as these swells move in on the
continental shelf they tend to shorten and steepen
noticeably (fig 2). The groundswell is independent of
any weather system and when wind-generated waves are
superimposed a very confused and unpleasant sea
results.
Average wind conditions along the entire coast are
fresh to strong, with generally fair winds from the north-
west, and storm winds from the south-east. However, the
Gulf of Alaska and Bering Sea regions produce a local
disturbance called the Alaska "Williwas" from a northern
quadrant which, although not cyclonic in origin,
produces recorded winds in excess of 125 nautical
miles/hr (230 km/hr).
Table 1 shows the frequency of daily maximum wind
speeds recorded by a Canadian weather station located
at Cape St. James, Queen Charlotte Islands. These
velocities are based on a four-year average and are the
least severe conditions recorded by three such stations,
the others being at Sandspit and Spring Island.
The Cape St. James weather oilice is nearly central to
Hecate Straits, the most prolific trawling grounds on the
west coast. The yearly average wind speeds on 8.4 days
out of 10 equals or exceeds Force 5 and on 4.7 days
out of 10 equals or exceeds Force 7, or moderate force.
Because virtually all Canadian west coast trawlers above
75 GT arc combination boats fishing several types of
gear over the year, it is of interest to note the dis-
position of the major fishing grounds in iig 1, and the
very great distances involved. Gulf of Alaska and Bering
Sea fishing trips arc 20 to 35 days and may involve
2,300 miles each way.
This paper describes the arrangements and techniques
used by small rampless Pacific Coast vessels and those
used by the somewhat larger Atlantic Coast stern ramp
trawlers.
Vessels engaged in this fishery have the typical wide
stern and wheelhouse and engine well forward, providing
the relatively clear after deck for fishing. Vessels of this
type were described by Hanson (1955).
VESSELS OF 25 TO 49 GT WITHOUT RAMP OR
DRUM
Back to 1912 the trawl was towed over the stern as an
accepted practice, although not in the form known today.
Vessels used were usually small salmon seiners fishing out
Wind
Speed
0-18
19-24
25-31
32-38
39-ovcr
Jan
4
2
4
6
15
Feb
\
1
5
8
13
TABLU 1
Frequency of daily maximum wind speeds in nautical miles at Cape St. .lames
Mar
5
4
5
4
13
Apr May Jim
4
6
6
6
7
10
5
3
5
6
8
7
4
Jul
7
4
9
7
4
AUK Sep
8
9
10
3
1
Oct
3
4
5
7
12
5
4
5
4
12
Dec
Annual
Fre- Per cent
quency
4
57 16
2
56 16
5
80 21
7
71 19
13
101 28
[563
of season and were 45 to 50 ft (13.7 to 15.2 m) long by
11 to 12 ft (3.4 to 3.7 m) beam; single decked with the
wheelhouse and engine well forward; powered by 60 to
100 hp heavy duty petrol engines. The mast and
salmon purse winch were about amidship (as today)
and the winch was no more than a powered whipping
drum. The trawls were small, seldom more than a 50-ft
(15.2-m) opening and the wooden doors were light enough
to be lifted aboard by hand. Manila rope was used for all
running lines, the rope bridles being spliced into a single
manila warp. The crew was the skipper and one man or at
the most, two.
The trawl was towed from a wooden bollard located
on the centreline just forward of the net platform
(approximately 0.75 L). Shooting the net was just
throwing the trawl into the water, followed by the boards
as the wings came tight, then one man would slack off
the bridles on the bollard and run the warp off to the
desired length.
When hauling, the boat was stopped and the warp
pulled in until the boards could be lifted on to the deck.
The vessel would then steam ahead until the trawl broke
surface, the bridles were recovered, and the boat would
then back down until the codend was alongside. At this
point wings and belly would be fleeted aboard, using a
single fall from the boom end to the purse winch. The
codend would be similarly lifted aboard for emptying,
using a double tackle.
In 1919, Jack Shannon conceived the idea of using a
heavy beam, hinged at the inboard end and projecting
3 to 4 ft over the rail, to carry a trawl lead block. Using,
for the first time, a single wire trawl warp and bridles
and a small, single drum winch in place of the usual
powered whipping drum, the trawl was towed from the
single block on the beam, which was amidships, opposite
the winch.
Hauling the gear was simplified, as the single warp
and bridles could be rolled on to the winch drum,
pulling the boards up to the lead block on the beam.
The same procedure was then followed for getting the
codend on board. Between tows, the boards were left
hanging at the lead block, when travelling the beam was
pivoted, bringing the boards on to the deck.
This system, known locally as "beam trawling'* is still
used by many smaller boats unsuitable for fitting a trawl
drum and may be the forerunner of the Gulf of Mexico
"double-rig" shrimp trawlers which use two "beams" or
outrigger booms, one to each side.
One of the first known boats to be rigged to tow a trawl
from stern davits using two trawl warps was a small
Canadian salmon seiner named the Ispaco 1. In 1934
a very crude arrangement of quarter davits and hanging
blocks, combined with a centreline bollard, was installed
on the vessel. As the salmon purse winch has no drum
for wire, the trawl warps were of manila rope and were
belayed around the centre bollard. When shooting gear
the trawl was dropped over the stern and allowed to
stream aft until the wings became tight, the bridles were
slackened on the bollard to drop the boards into the
water, then the warps were slackened off to the desired
length for fishing.
Not until 1937 was a Pacific coast trawler fitted with a
double drum winch capable of handling two wire trawl
warps through stern davits and the deck arrangement
thus worked out is the basis for virtually all such vessels
operating today. The winch was set athwartship, with
Hg 3. Traditional deck arrangement for Pacific Coast trawlers with
a thwart ship-placed winch permitting the trawl warps to be led
straight to the bulwarks
the trawl warps leading to a flat sheave mounted on the
bulwark rail cap then aft on each side to the quarter
davits and hanging blocks (fig 3).
The advantages arc obvious, as there arc no running
lines across the working deck area and consequently no
need for bollard or other lead sheaves mounted on the
deck. This is also a natural lead to the davit when purse
seining.
One disadvantage is the need for spooling arrangement
on the winch as the distance from winch to bulwark lead
is not usually enough to provide for natural spooling
of the wire. A second disadvantage is that when the
wings arc hauled up to the davits and the codend taken
around the side for emptying, much loose web remains
in the water around the stern with the possibility of
fouling the propeller and rudder. Even if the excess web
is fleeted aboard, the wings arc still lying across the stern
and it was to solve this problem that the trawl drum was
developed.
TRAWLERS FITTED WITH DRUM
Since being developed by a Seattle fisherman in 1952 the
trawl drum has virtually become standard equipment
on all west coast trawlers and is finding an increasing
acceptance among Atlantic coast fishermen.
While there are no standard dimensions for trawl
TYPF B
_
(?360mm )
(304mm)
Fig 4. Typical dimensions of trawl drums constructed recently
drums, as most have been built to suit individual needs,
the majority are constructed generally to the dimensions
shown in fig 4.
Type A is suitable for trawls up to 80 ft (24.5 m)
headline and 100 ft (30.5 m) groundline if fitted with
smooth bottom gear; type B for any trawl now in use
on the west coast if fitted with rough bottom gear of
14 in (35.5 cm) and 18 in (45.7 cm) bobbins and rollers.
Type A makes use of the so-called "yo-yo" drive,
and is just a rope around the winding drum with a lead
to the shipping drum on the winch. When hauling the
trawl, the free end of the rope is taken around the whip-
ping drum and, unwinding on the drum, winds the
independent cables, sweeplines and wings on to the
storage drums.
Shooting the gear is just the opposite, the hauling rope
being allowed to slip on the whipping drum with a
consequent braking effect and, as the pull of the trawl
unwinds the drum, the hauling rope is rewound on the
winding drum (h'g 5).
Type B is a fairly recent Canadian development
intended to further simplify the handling of the sweep-
lines, which arc rolled on to swecpline drums, making
manual handling of the wire to ensure even wraps on the
barrel (fig 6). A slot cut through the inner flanges of the
sweeplinc drums allows the wire to be passed through
on to the main drum when the wings start to come
aboard. This much larger drum is powered w.th a piston
reversing hydraulic motor, usually of 45 hp at 1,200
lb/in2 (85 kg/cnr'), fitted with 3:1 gear ratio lor drum
speeds of 0 to 1 5 rpm.
The hauling sequence is basically as follows:
• The trawl boards are hove up to the gallows and
left hanging on the warps and the boards clamped
to prevent slamming
• The independent cables are unhooked from the
boards and clipped to eyes on the drum
• The drum winds in the independent cables until
the pull of the trawl is taken by the drum, then the
pennants are disconnected from the sweeplines
and hung on the gallows
• The sweeplines, wings, and belly of the trawl are
wound on to the drum, leaving the length re-
quired to get the codend aboard for emptying
Advantages:
• It makes a "big" trawler out of a boat too small to
accommodate a stern ramp
• Reduces the number of crew required to handle
trawl to the winch operator (engineer) and two
men to hook the doors and connect the inde-
pendent cables
• No manual hauling of web
• Although the codend must be lifted aboard it is
simple to split the codend on large tows and empty
the catch into the desired deck pond
• Faster handling of the trawl when hauling as
warp pull and drum pull are in line with the ship
• Because the bulk of the trawl is stowed on the
drum, the working deck is kept clear, even on
relatively small vessels
• There arc no running lines or wires crossing the
deck, resulting in greater safety
• The crew are not required to handle moving wires
• The working area, at the after end of the vessel,
is much less affected by pitching and the forward
Fig 5. Trawl drum driven by a rope from the trawl winch
[565]
Fig 6. Improved hydraulically driven trawl drum having separate sections for the sweep lines
deckhouse offers a greater degree of safety and
comfort to the crew
• The extreme simplicity of the drums, ensuring low
initial cost and trouble-free operation
• The greatest advantage of the drum is the in-
creased earnings resulting from the fewer number
of crew. Typical west coast drum trawlers of 70 to
75 ft (21.3 to 22.9 m) and 100 GT, with a crew of
four men, consistently land an average of 1 10,000
Ib (49,900 kg) of iced fish for five days fishing.
This will be taken on 4.2 tows of 2.1 hr each per
day for a mean catch per two of 5,239 Ib (2,376 kg).
This may be extended to show a production of
624 Ib (285 kg) per man/hour expended
Favourable comparison
This compares most favourably with much larger 110 to
116 ft (33.5 to 35.4 m) stern trawlers on the Atlantic
coast which are consistently landing 260,000 Ib (117,950
kg) of iced fish for eight days fishing time, working with
a crew of 12. This catch will be taken on an average of
six tows per day of about 1 .8 hr duration for a mean
catch per tow of 5,425 Ib (2,460 kg). However, the
production per man/hour is only 252 Ib (114 kg). In
both cases only the larger fish were dressed, the balance
iced in the round.
It must be admitted that a direct comparison cannot
be drawn between large trawlers operating on the
Grand Banks and small trawlers fishing in the north
Pacific, but it indicates the relatively high efficiency of a
small drum trawler. The figures for catch and effort are
the average for all vessels of this general size operating in
each area and were supplied by the Fisheries Research
Board of Canada.
An interesting experiment is being conducted by the
Industrial Development Service of the Department of
Fisheries (Canada) using a standard hydraulically-
powered trawl drum on a conventional side trawler,
with the intention of eliminating all manual hauling of
the web. To date the fishing tests have not been carried
out.
TRAWL WINCHES
Although briefly covered by Alverson (1959) the winches
used on the smaller north Pacific trawlers are of special
interest.
All vessels used for combination fishing such as
V1'1"
Fig 7. Typical Pacific Coast combination winch suitable for trawling
as well as for purse seining
trawling, herring and salmon seining, halibut long-
lining and tuna seining make use of the ''combination"
winch (fig 7).
Vessels solely for trawling are quite often rigged with
individual or "split'* winches positioned just inside the
bulwarks and leading directly aft to the trawl davits.
Although this eliminates the need for spooling gear, it
requires an awkward arrangement of leads when purse
seining and is not much favoured for this reason.
The combination winch is always set with an athwart-
ship lead from the main drums and when trawling each
warp is taken around a heavy sheave (at least 16 X wire
[566]
dia) located at or on the bulwark cap and in line with
the winch, then directly aft to the quarter davits. Al-
though this requires a right-angle lead, the friction loss
is less than the usual system of deck or bollard mounted
sheaves which alter the direction of the wire at least
three times. The greatest advantage is the complete
absence of running lines crossing the working deck
where men may be sorting and dressing fish or mending
gear. While less important in large trawlers, this is
essential in vessels under 100 ft (30.5 m) where working
space is always at a premium.
When seining, the purse lines are both led from the
same side of the winch to the seine davit, the main drums
often being vertically offset to simplify this. The spooling
gear, either hand or mechanically operated, can be
moved to either end of the winch depending on use. A
cargo or "brailing" drum is fitted either at the port side
or on top of the winch. A removable longline hauler is
fitted at the port after side of the winch. Independent
spool drums and pipe cavil are fitted as shown. Major
characteristics of some typical combination winches arc
shown in table 2.
SMALL STERN TRAWLERS WITH RAMP
With the present type of trawl gear there aic only four
basic handling methods for small Jtern ramp trawlers,
although there are many variations of procedure.
These are :
• Leaving the trawl in the water and bringing only
the codend up the ramp
• Taking the wings up each side and hauling the
codend over the square
• Taking both wings up one side and the codend and
intermediate up the ramp
• Taking the entire trawl up the ramp by means of a
trawl drum
It would seem pertinent to discuss some of the advant-
ages and disadvantages of these systems.
Leaving the trawl in the water
This method is exemplified by such stern trawlers as the
Canadian Polar Fish, the British Universal Star and
others. The basis of this system is the use of either a
pivoting arch or overhead gantry to lift only the codend
up the ramp. A variation is the Pacific coast practice of
lifting the codend aboard over the side on vessels not
fitted with a drum. In both methods the wings, belly and
intermediate are left floating in the water.
Advantages:
• Involves the least amount of handling of net when
fishing, as only three men on deck are required to
handle the gear
• Requires least amount of deck space beyond that
needed for dumping, cleaning and sorting fish.
May be as little as 20 ft (6.1 m) from winches to
stern
• Suitable for very small trawlers of 40 to 50 ft
(12.2 to 15.2 m), particularly for combination
boats already fated with a boom
Disadvantages:
• The net is left floating across the stern with the
ever-present possibility of fouling or rolling up
• Unless both wings are hauled up to one side the
codend must be lifted over the floating net
• Impossible to examine or repair net during
normal fishing sequence
• When fishing is finished, or the net is required on
board for repairs, trawl can be recovered only by
successive fleeting or pulling aboard by hand
• Experience has shown that when fishing in rough
weather there is very often trawl damage due to
vessel heaving or sliding over the floating net
• If an arch is used, the restricted drift between the
recovery blocks and the deck limits the amount of
fish that can be brought aboard in one lift
• It is awkward to split the codend when working
over the stern with the trawl floating in the water,
TABLE 2
Major characterististics of some typical combination winches
Base dimensions
Drum capacity each
Line pull J drum each
Line speed £ drum trawling
Input horsepower
Hydraulic oil rcg'd.
Line speed j drum seining
Small Boars
25 to 60 67
36x57 in
(90x1 45 cm)
300 fm i in
(550 m 12.7 mm)
3,1501b
(1,430kg)
180 ft/min
(55 m/min)
30 hp
40 gal/min
at UOOlb/in*
(84.5 kg/cm2)
100 ft/min
(30.5 m/min)
Medium Boats
50 to 90 GT
36x70 in
(90x1 80 cm)
600 fm ft in
(1,100m 143 mm)
7,500 Ib
(3,400 kg)
180-200 ft/min
(55-60 m/min)
* 50-60 hp
60-80 gal/min
at l^OOlb/in*
(84.5 kg/cm2)
120 140 ft/min
(36.5-42.7 m/min)
Large Boats
80/0 15067'
48 • 90 in
(120/230 cm)
750 fm I in
(1,370m 19mm)
7,800 Ib
(3,540 kg)
220 ft/min
(67 m/min)
90 hp
80 gal/min
at l,6001b/in2
(112.5 kg/cm2)
140 ft/min
(42.7 m/min)
[567
TOR POWER BLOCK
SIN6LE DRUM
WMCH FOR
3WEEPUNE
Fig 8. Proposed deck arrangement for a 79 ft (23.8 m) combination fishing vessel
although if the codcnd is brought around the side
this becomes a much simpler problem
• If a single trawl winch is used and is set to lead
fore and aft, a complex system of lead blocks
must be used unless the warps are led directly from
the spooling pins to the gallows blocks. In either
case there are running lines crossing the working
area. A better system would be to use thwartship
leads from the winch to the bulwark sheaves,
then aft to the quarter blocks, thus keeping the
working area clear
Taking the wings up either side
This method is exemplified by the Canadian stern traw-
lers Grand Monarch and Donald Rheal, the proposal by
Birkhoff (Stern Trawling, 1963) and by the author's
design of a 79-ft (24 m) vessel for combination
fishing (fig 8).
The basis of this method is to have a bobbin tray port
and starboard of the working deck, each of a length to
accommodate half the head rope. A small hydraulic
single drum winch is fitted at the forward end of each
tray to handle the sweeplines. The codend is hauled up
the ramp and lifted over the square by a lazy-decky
connected to the chocker strap. This is clipped to a
messenger line from the brailing winch through a lead on
the boom. A variation is used by the British vessel Ross
Daring which lifts the codend aboard over the side.
Another variation is to eliminate the small sweepline
winches and haul the wings forward with the main trawl
warps, which are disconnected from the boards for this
purpose. This can be done only if the winch is a combina-
tion type with thwartship leads or split winches are used.
If, as shown in fig 8, the vessel is fitted with a hydraulic
ramp gate which is kept closed at all times except when
shooting and hauling gear, the hauling sequence is as
follows:
> Hauling warp the gate is closed
568]
• Trawl boards are hooked and left on the main
warps
• The independent cables are unhooked from the
boards and clipped to the messengers from the
sweepline winches. Recessed links and G-hooks
are used
• The ramp-gate is opened and the sweeplines
placed in the ramp opening
• The bridle pennant is disconnected and hung out
of the way as sweeplines and wings are hove up
the ramp
• When the headline is tight against the restraining
track the lazy-decky is clipped to either a mast or
boom tackle and the intermediate and extension
piece is doubled up the ramp
• The codend is lifted with a boom tackle for
emptying
• The ramp door can be closed if desired as soon as
the codend clears the ramp although this depends
on the length of the intermediate and extension
pieces
Advantages:
• The entire trawl is brought aboard in two pulls
• The net is well spread out for quick repairs, and
replacing the groundline is a simple matter
• The bobbins, being cont; ;ned by the track,
cannot roll around in bad weather
• Vessels of only 80 ft (24.4 m) LOJ ,?an handle
trawls up to 110 ft (33.5 m) ground-rope, such as
a modified Grunton or Yankee 41, fitted with
rough bottom gear. There is no objection to
leaving part of the groundline on the ramp
• The trawl is clear of the main fish ponds during
emptying of the codend
• The gear can be shot immediately after emptying,
without interfering with the cleaning and sorting
of catch
• Maximum safety for deck crew as all running lines
are clear of the working area, with the exception
of the nylon haulback
• Maximum safety for ship and crew as the ramp
gate almost eliminates the possibility of flooding
the main deck by a sea breaking over the ramp.
This is important on small trawlers with their
relatively low freeboard
• Experience on Canadian trawlers indicates no
undue wear on codend is caused by dragging
over the floats, bobbins, etc
• The main winch can be under cover
• For winter fishing portable sides can be fitted above
the bulwarks and extending from the break
forward aft to the gallows. This will provide
maximum crew protection from wind and spray
Disadvantages:
• Splitting of large tows is awkward when working
over the stern
• Small stern trawlers of 80 to 100 ft (24.4 to
30.5 m) of length do not have sufficient moulded
depth to permit tween-deck storage of wet fish.
It is therefore necessary to dump fish into deck
ponds for cleaning and sorting. This results in
the codend having to be lifted over the square
• Somewhat greater mechanization is required if
separate sweepline winches are used. The alterna-
tive requires much more handling of running lines
and results in slower handling of gear
• If vessel is to be used for combination fishing,
changeover is more complex because of the dual
bobbin trays
Taking both wings up one side
The basis of this method is the French "Amyot" system
and modified by the author in the design of a new trawler
to be built on the Pacific coast (fig 9).
This makes use of a bobbin tray fitted to one side of
the deck of a si/e to handle both wings and of a length
to handle the doubled footropc. A small hydraulically
powered double-drum winch is fitted to haul the wings
up the tray. The codend and intermediate only are
brought up the ramp, the travM being doubled around a
faired post at the side of the ramp.
The hauling sequence is virtually the same as system B
except that the Marboard independent cable must be
passed across to the port side before being clipped to the
messenger line from the sweepline winch.
A second bobbin tray fitted to the starboard side with a
complete trawl made up in the tray will permit in-
slanianeous change of gear, eliminating lost time due to
repairs or change of bobbin line.
For a trawl of 120 ft (36.6 m) groundrope the shortest
practical length of vessel would appear to be about
95 ft (29 m) length overall, although the determining
factor is the amount of water that is trapped on deck
and consequent effect on vessel stability. A partial solu-
tion is 10 use narrow waterways on each side of the deck-
house, thus reducing the permeability of the deck.
Advantages :
• There is always a trawl ready for shooting with no
handling required
• The codend does not have to be lifted over the
square
• The lish ponds are clear for emptying, sorting and
cleaning
• Shooting can be carried out with fish on deck
• One trawl can be spread out for repairs without
interfering with the shooting or hauling of the other
• The fishing operation can be handled by only
three men including the winch operator. If the fish
is being landed iced in the round, one additional
man for icing would be required and, if dressed,
two additional men would be required. The crew,
for eight-day trips, will not exceed six men in-
cluding the captain, whatever the method of
handling
• Deck configuration is ideally suited to protected
operation of crew and machinery
• Maximum safety for crew due to absence of
running lines and containment of bobbins in trays
• Maximum safety of ship due to use of ramp gate
and narrow waterways for bobbin trays, thus
reducing amount of water that is trapped on deck
[569
Fig 9. Modified "Atnyot" system for handling the trawl net on deck which requires a vessel length of about 95 ft (29 m)
Disadvantages:
• Higher initial capitalization due to greater
mechanization. However, productivity should
reach average levels of 900 to 1,000 Ib (410 to
500 kg) per man/hour, resulting in increased
earnings
• More involved changeover if vessel to be used for
purse seining
Combination of ramp and trawl drum
This method is exemplified by the proposed designs of
Alverson and Schmidt (1959) and by the US trawlers
Narragansett and Canyon Prince.
The basis is the use of a west coast trawl drum mounted
coaxially with the trawl winch, the lead being aft. The
trawl is hauled up the stern ramp and along the deck by
the drum until the codend is aboard and can be lifted
with boom tackles for emptying.
The hauling sequence is basically similar to that
described for a stern mounted drum trawler, with the
exception that hauling would be continued until the
codend was on the ramp or could be reached with the
boom tackle.
There are several advantages to this system with
particular application to fairly small vessels of 60 ft
(18.3 m) or more, if such vessels recover the codend
over the stern.
Advantages:
• The entire trawl is brought on deck in one pull
• A minimum of labour is required to handle trawl
• The drum pull is in line with the ship so manoeuvra-
bility is not impaired
• No special winches are required for the sweeplines
• System can be operated in as little as 30 ft (9.2 m)
deck length
• Trawl can be easily rolled off the drum for
repairs, if deck space available
• Codend is well positioned for lifting with boom
tackle
The principal advantage of a drum is the ability to
haul and store the trawl at the stern and clear of
the working area. If the drum is positioned at the
forward end of the deck this advantage is lost
and experience indicates that most, if not all, of
the following comments are valid.
Disadvantages :
• Hauling speed must be lower than is usual with a
drum to prevent undue wear on the net by dragging
over the deck
[570]
• Virtually the entire trawl must be on the drum
before the codend is available for lifting
• When shooting gear, the trawl must be either
successively fleeted aft, using a haul back tackle, or
the drum and chute must be mounted sufficiently
high above the deck that the trawi will pull off
after the codend has been dropped back in the
water
• Some form of chute from the top of the ramp (or
stern) to the drum must be used to restrain the
net from sliding over the deck and is essential if
rough bottom gear is being used
• In smaller vessels, up to 75 ft (22.9 m), the chute
or net tray covers a large proportion of the avail-
able working deck
• The codend must be emptied into ponds clear of
the trawl chute and warps. Such ponds may be
very limited in size if both the warps and chute
cross the working deck. The only exception would
be if all catches were "clean" and could be
emptied directly into the storage hold by way of
the main hatch, although the fish would still have
to be hand-stowed into the wing pens
• Tf the trawl needs repairs, it can only be spread
over fish on deck, or must wait until the deck is
clear
• If the stern ramp is deliberately shallow and runs
well into the working deck (in lieu of n net chute)
the following comments apply:
(a) Increased possibility of flooding the deck if
vessel backs down over fouled gear
(b) Deck is badly arranged for holding fish for
cleaning and sorting
(c) Difficult to locate loading hatches for easy
access to wing pens, and main hatch may
have to be used to transfer fish below
(d) Changeover to other fishing gear, notably
seining, is unduly complicated because of
covering the ramp
A variation of this system which eliminates most of the
above disadvantages is to offset the trawl drum to the
port side of the stern and the ramp to starboard (fig 10).
The hauling sequence is identical to that described for
any drum installation except the codend is lifted up the
ramp with the boom tackle, leaving the intermediate
doubled around a faired post between the drum and the
ramp. The principal advantage is that no trawl net
crosses the working area and fish may be emptied to
suit loading requirements.
A second advantage of landing the codend up a ramp,
rather than over the side, is the opportunity to close in
Fig JO. Arrangement of trawl drum and ramp
both sides of the working deck with portable bulwarks,
providing effective protection for the crew from wind
and spray.
FUTURE TRENDS
In those countries where year-round operation with one
type of gear is impractical, due either to seasonal
appearance of fish stocks or to incidence of bad winter
weather, the need for a combination boat becomes
inevitable. If such a vessel is considered, two factors
play a dominant part in the earning capacity of the
vessel. These are:
• The ease with which a gear changeover may be
carried out
• The capital investment required for the various
types of gear
Since trawling, purse seining and longlining are the
three most commonly practiced methods of fishing it is
essential, in planning a combination boat, to make
provision for maximum efficiency in each of these
fisheries.
In the case of really small trawlers of from 36 to 50 ft
(11 to 15.2 m), there can be little argument with the use of
a trawl drum, whether the codend is brought over the
stern or the side. The cost of the drum is extremely low,
especially so if a rope-drive is used. Further, the saving
in manpower is important in both the amouni of living
accommodation required on board and in the increased
earnings per man.
Since trawlers of this type simply do not have sufficient
power to tow even moderately sized trawls fitted with
rough bottom gear, the limitations of the drum in
storing anything larger than 18 in (45.7 cm) bobbins is
not a pertinent factor.
In larger vessels of from 50 to 75 ft (15.2 to 22.9 m),
the use of a trawl drum, such as the Type B, again has
too many advantages to be ignored. Chief among these
is the ease with which the drum can be removed during
changeover, the hydraulic drive commonly being used to
power either the power block or the longline hauler. A
stern ramp is not essential since lifting the codend over
the side with boom tackles (the boom remaining fixed
at the centreline) has been standard Pacific coast practice
for many years despite the frequency of heavy weather
during operations.
Since both purse seining and longlining require
considerable space across the stern, the absence of a
ramp simplifies the changeover. However, a ramp offers
one indirect advantage in that if the codend is not being
lifted over the side the bulwarks can be closed in for
protection from wind and spray.
It is in this general size of vessel that the author would
make the suggestion of using two trawl drums mounted
side by side at the stern, the second drum being used to
stow a spare trawl. Then fishing is uninterrupted because
of damage repairs or if a change from smooth to rough
bottom gear is required.
From 75 ft (22.9 m) or over, a ramp becomes quite
practical if the vessel is consistently fishing rough
bottom, since the handling of heavy bobbins can be
better done by either of the systems shown in fig 9 or 10
than by the use of a drum.
571]
New Trends in Stern Fishing
by Jan F. Minnee
Tendances nouvelles dans la p£che por Tarnere
Lc succ&s de la peche par 1'arrierc pratiquec avcc dc grands bateaux
s'est affirme ces demises annte, et les armateurs de bateaux de
petit tonnage commenceni & s'int6resser a cette technique. L'auteur
presente dcs recommanda lions d'ordre general quant a 1 'age n ce-
ment ct au dessin de petits navires a peche par rarrierc. DCS
details sont fournis sur trois recentes realisations (1%2, 1963 et
1965): un navire tirant le chalut a pcrchc par rarrifere; un bateau
polyvalent (presentant comme innovation une installation pour
manoeuvre de la senne par I'arrigre); un petonclier a peche par
1'arriere utilisant trois dragues.
Nuevas tendencias en la pesca por la popa
La pesca por la popa ha tenido exito en las grandes embarcaciones
de pesca en estos ultimos aflos, pero tambi6n van estando intercsados
en el la los propietarios de embarcaciones menores. Se formulan
rccomcndaciones generates para la distribuci6n y disefto de
pequeftas embarcaciones para la pesca por la popa. Se presentan
tres diseftos recientes (1962, 1963 y 1965) correspondientes a un
arrastrero de vara por la popa, una embarcaci6n de aplicacioncs
multiples (con una propucsta para la pesca con redes de ccrco por
la popa) y un arrastrero para la pesca de vieiras por la popa
mcdiante tres rastras.
IN the few years since its introduction, stern trawling
has proved so advantageous, from the point of view
of fishing tactics and vessel design, that even owners of
small boats — the most conservative of fishermen —
wonder whether stern trawling may be worthwhile for
them. The small-boat fisherman works under many
handicaps. He generally has a small crew whose educa-
tion is limited. Government regulations about tickets
and licences limit the size of his boat. To take full
advantage of his restricted power, he must use a variety
of fishing methods which change with the season. Above
all, the small-boat fisherman has little money. He cannot
afford to gamble on relatively new and untried tech-
niques.
DESIGN REQUIREMENTS
Designing a small stern trawler is more difficult than
designing a large one. The problems are greater and
often more controversial. The requirements are contra-
dictory. For example, a small-boat skipper wants the
biggest boat with the lowest tonnage and, of course, the
lowest price. He wants the case of remote-control of.
operations, but he wants mechanical simplicity. He
wants a multi-purpose vessel on which he can change
operations at sea. A recent trend is the demand for
sheltered processing space apart from the fish-deck.
SMALL-BOAT DESIGNS
Some general particulars for designing small stern
fishing craft are given below:
Hull shape and particulars
Breadth should be maximum in order to ensure sufficient
GM and large deck area, especially at the stern.
Depth: in connection with breadth, sufficient free-
board for dry deck while heeling, ensuring adequate
dynamical levers.
Draft aft maximum for restricted water depth, to
give good propeller immersion for satisfactory towing
thrust and protection.
Adequate flare and sheer forward and preferably a
forecastle for dry decks and good seakeeping per-
formances.
High midship section coefficient (Cm) for moderate
prismatic coefficient. The old vee-bottom midship
section, which may have had good sailing properties,
should be avoided for modern power-driven boats. A
smaller prismatic coefficient produces better speed and
towing characteristics because of waterline fore and aft
and larger hull dimensions for the same tonnage,
enabling ballast to be put lower in the vessel. From
experience the seakeeping properties are improved and
there is less slamming and better propeller performance
in waves.
Short deep bilge keels to increase the short rolling
period caused by the fairly high GM. These keels should
extend only over the fullest part of the midship body to
avoid unnecessary increases in resistance.
Hull subdivision and arrangement
The deck area aft, needed for gear handling, depends on
whether a ramp is used. Stern trawlers with a ramp need
sufficient afterdeck length to accommodate the length of
the trawl wings plus extra length for placing straps at the
top of the ramp. In this system, each haul brings all the
gear aboard with a generally horizontal direction of
towing.
Stern trawlers without a ramp require only sufficient
deck space to accommodate the trawl doors. The gear
is hauled more or less vertically and the codend is
brought aboard between the trawl doors. To minimize
space requirements and maintain a normal transom
stern, the rampless system offers better possibilities for
small vessels both for single and multi-purpose layouts.
A rampless stern trawler, however, still requires a
minimum fishdeck length of JO ft (3 m). The centre-
line casing becomes an obstacle in boats under about
70 ft (21 m) with engines aft.
As a rule, processing should be done on top of the
fish hold, the fish-hold hatch being the last position in
processing. If space allows, the route of fish for pro-
572]
cessing should start on the after fishdeck and finish at the
first available fish-hold hatch. These hatches should of
course, give easy access to the entire fish hold for easy
loading and unloading. The limited deck space docs not
permit the use of a portion of the fishdeck for processing
only, since the whole deck area must be available if net
repairs are needed.
Wing engine-room casings against the ship's sides are
not only unattractive but also unacceptable in certain
fishdeck arrangements (e.g. in beam trawling).
From experience of vessels up to about 90 ft (27 m)
Loa, the most economical way of hull space utilization
is to locate engine space forward, with wheelhouse and
winch nearly on top of it for short communication, more
direct control and mechanical drive. This introduces the
problem of a long propeller shaft, passing through the
fish hold aft. In way of the shaft, the fish-hold floor must
be raised, but the loss is compensated since the S-shaped
framing aft gives more capacity than the vee-framing
forward. In these stiff hulls there should be no technical
problems with this shaft, providing there is easy access
to the stern gland and modern self-adjusting bearings
are used.
When underdeck crew accommodation is needed,
often the case in small craft, the best position is between
engine room and fish hold, practically amidships where
the ship's motion is relatively small.
With fuel tanks aft, the less accessible hull spaces are
used and trimming effects are small. As fyd is burned,
its weight is replaced by fish. In this case, the vessel
becomes heavy-ended, introducing a large longitudinal
moment of inertia that increases the pitching period.
Good flare and high sheer or forecastle are needed to
prevent wet decks.
Vessels over 90 ft (27 m) Loa using the rampless
system may be laid out in the conventional way, engine
room aft and fish hold forward, especially when a long
forecastle is required for accommodation and processing
or for bad weather conditions. Here there is sufficient
deck area to have a fishdeck aft and a processing deck
amidships, separated by the engine room casing. The
catch will then be transferred by a conveyor belt which
serves as a moving worktable, giving better working
conditions; its mechanical assistance, though adding to
the boat's initial cost, increases earning power because
it attracts better crewmen.
Winch and wheelhouse
Except for power, the most important factor for a boat's
fishing efficiency is the positioning of winch and wheel-
house. Although the general arrangement or hull sub-
division frequently determines these positions, they
deserve more consideration. Generally the winch controls
should be in the wheelhouse. On both large and small
boats, this gives more direct control of the winch in
relation to vessel manoeuvres and vice versa. Beyond
that, on smaller craft, the skipper has direct contact
with the gear handling and he can take rapid corrective
measures in emergencies. With the winch adjacent to
the wheelhouse, expensive remote control systems are
avoided.
Both winch and wheelhouse should be as far aft as
possible. This results in better steering and provides the
best view during fishing operations. Several factors com-
plicate this positioning: minimum deck length aft,
position of the fish-hold hatch, engine room location,
spooling distance and other factors. Once again a com-
promise position must be selected.
Much care must be given to arranging the various
wheelhouse instruments. Their size and number are
increasing continually, yet the designer must ensure an
all-round view from the controls during critical stages in
fishing operations. The captain's cabin should be adjacent
to and forward of the wheelhouse if possible, but must
not obstruct the view from the wheelhouse. The space
under the wheelhouse floor may be used for the winch
motor, electronic equipment, convenors, fans or the
small harbour electricity set.
The general arrangement and stability considerations
control whether winch and wheelhouse are situated on
the main deck or above. As a rule, warps and other wires
should be led well above the working deck so as not to
cause obstruction. The number of guide rollers should
be kept to a minimum as each additional one adds to
line wear, but sufficiently wide guide roller spacing
makes for easy spooling on the drums. These should be
as narrow as possible to enable the fitting of extra drums
for auxiliary purposes.
So as to be adaptable, the winch should be designed
to perform the main part of the varied handling require-
ments and must provide the mechanical power for gear
handling. Therefore the winch should be able to cope
with many ropes and wires, either simultaneously or
selectively in order to reduce manual handling to a
minimum. Winches with six independent drums arc
common today in the Netherlands. After the intro-
duction of a multi-purpose winch, it takes some time
for a crew to become accustomed to not working on the
warping ends. Warping ends still arc occasionally useful,
even with modern equipment, but the winch is usually
badly situated for them. Again a compromise on winch
location must be reached, although it must not interfere
with deck work. With the good selection of compact
gears now available, it is better to have some well located
additional hydraulic gear. The winch itself should have
all the modern requirements such as reverse systems
in the main drive and auxiliary drums with small fly-
wheel effect (small moment of inertia), thus facilitating
easy stopping and reversing.
FISHING EQUIPMENT
Since small boats use many fishing methods, a general
detailed explanation of fishing gear is difficult. However,
all fishing relics on a skeleton of basic equipment to
which a variety of specialized equipment may be added
for specific methods. From experience of multi-purpose
designs, the following are worthy of note:
Basic equipment
A multi-drum winch: minimum: two main drums plus
two auxiliary drums plus two warping ends.
A fishing mast, single or bipod, preferably unstayed.
This mast should carry either a transverse outrigger at a
573]
©
!• 4 worp trawl
2- gilson
3" split strap
4- codend
5~ wmg
/. Ground and midwater stern trawling (split net system)
certain height to provide suspension for blocks or
rollers in line with the different winch drums and with
the inclined transom stern, or two derricks providing the
same suspension points. These should be able to be
rigged either fixed together with diaphragms or cross-
bars, or independently for beam fishing or purse seining.
A pair of gallows, either as part of the mast structure
without any other attachment (leaving bulwarks and
deck completely free) or as removable structures bolted
only on top of the port and starboard bulwarks, which
must be reinforced locally.
A system of removable stanchions and boards on
deck to provide fishponds, or other means of storing the
catch on deck during processing.
The necessary guideblocks, leading the wires and
ropes from the winch to the different blocks. None should
be mounted on deck, and preferably on the mast structure
only. This leads to a variety of possible layouts by the
addition of special equipment.
Special equipment
For stern trawling, both on the bottom and midwater
(fig 1) (single or two-boat fishing with two or more
warps): add big net roller on the transverse (outrigger), a
guide frame for the gilson and loose netting, and a bag
arrestor. The vessel may be laid out with open or closed
processing space or with just an open-sided sun awning.
In fig la a split of yoyo-system is shown. The quarter
ropes are hauled up either over the low rollers or over
the handling mast blocks (dotted).
In fig Ib, by the splitting strap (3), the fore part of the
net is dried and the codend filled. By means of the
gilson (2), the codend is hauled aboard. In fig Ic the cod-
end is hoisted, swung aboard and emptied. The cod-
end is then returned to the sea and a further pull of the
splitting strap (3) refills the codend and the procedure is
repeated. This system enables an unlimited amount of
catch to be hauled in without the risk of bursting the
codend. It can be used for midwater and bottom trawl
gear of any size and shape with normal deck layout and
is easily converted to other fishing methods.
For beam trawling with two-door shrimp trawls,
groundfish rakes or scallop rakes: use the outfit with two
derricks, or add two derricks. Layout may be similar to
fig. 1, but for beam trawling open sides are preferable.
For purse seining (Pacific system): add powerblock
and outfit with two derricks, boom swing winch, purse
davit and some other special equipment (net grating,
etc.). For stern purse seining (for which a proposal is
given later) the outfit for stern trawling is sufficient, with
only the powerblock and topping brail boom added.
For longlining a special type of capstan should be
added and some less important equipment for running
out the lines. The general arrangement should show at
least one side open.
For gillnetting a power-drive net roller on the stern
bulwark is needed. In addition there should be some
labour-saving equipment, such as a webshuttle machine.
The layout may be similar to that used for stern trawling,
even with an all-enclosed processing space. Since herring
driftnetting is declining now, there is very little interest
in developing new tactics for this method in the Nether-
lands.
MULTI-PURPOSE DESIGN PRINCIPLES
The above may give the impression that a sound multi-
purpose design is easy to produce. There are, however, a
few very important points :
• Whenever a compromise has to be found between
controversial requirements, this should never be
an excuse to spoil the whole layout
[574;
warp
boom
topping wire
bock ttay
5 front stay
6 gilton block or
nttrolltr
7
8
9
10
II
12
13
gilton
top ttoy
from* stay
fromt for tttrn trawling
stopper
trawl gal lows
hmgtd fishpond
Fig 2. Dutch stcm/heam trawler
The minimum basic equipment may be too
elaborate. Items that do not exist are never in the
way
After thorough practical study of the fishing
methods that are to be catered for, do not hesitate
to propose a modification or something basically
different, because most methods have been
developed, through time, on different boat types
and from different viewpoints. This will not be
easy, but may sometimes lead to real development
and progress.
RECENT DEVELOPMENTS
A few specific examples of new developments are shown.
These arc from the designs of the author, recently com-
pleted for owners in the Netherlands, Mexico and
Canada. Most details in the general arrangement need
no explanation after the previous pages, so that only
particular points will be given some further considera-
tion: fishing equipment and special tactics.
Dutch stern/beam trawler
First vessel completed in the Netherlands in March 1965.
[575]
Particulars
Loa
B . .
D .
Power .
Winch .
Mechanical drive off
Tonnage
Hold capacity.
Fuel capacity .
Fresh-water capacity
Accommodation
Gear
Fishing equipment
Basic
73 ft (22m )
60 ft (18m)
18 ft 8 in (5.6m)
8 ft 8 in (2.6 m)
380 hp (reversible and reduction
gear)
2 x 400 fathom i in ( 1 2.7 mm) wire
2 x 100 fathom I in ( 1 2.7 mm) wire
main engine
49.5 GT
1,750 ft3 (50 m3)
560 ft3 (16m3)
50 ft* (Mm3)
6(2x3 persons)
(a) ground trawl with tickler
chains
(b) midwatcr two-boat trawl
(c) two beamrakes 30 ft (9 m) wide
Four-drum winch on maindeck, controls at winch
and in whcclhouse
Bipod (unstaycd) fishing mast with two derricks
23 ft (6.9 m) long and with suspension frame
carrying: two gilson blocks for beam trawling or
one gilson block plus one net roller when trawling
Cantilever-gallows built on mastlegs, port and
starboard
• A turn-over fishpond, hoisted by the gilson
messenger, that gradually discharges catch on to
sorting tables in the processing space, where men
can work upright (a non-expensive device utilizing
the force of gravity and a substitute for the con-
veyor belt aboard larger vessels)
Special
This is the first small boat in the Netherlands arranged
with a sheltered work space. To accommodate the beam-
trawl-rakes during sailing, sides must be open and bul-
wark rails entirely free but, when fishing, the gap between
the shelterdeck and bulwark rails can be closed by
hinged flaps, providing an enclosed space for processing
and net repair.
Warps and ropes, topping wires, etc., arc led over the
sheltcrdeck to guideblocks and footsheaves, adjusted by
different attachments to suit the various situations. A
guide frame is fitted for stern trawling and also serves to
steady the bags of the beam rakes when hoisted (fig 2).
Tactics
The main difference in stern beam trawling and con-
ventional beam trawling, carrying the derricks on the
foremast (Verhocst and Maton, 1964) is that the towing
points (derrick-tops) are considerably aft of midships
(fig 3b). Consequently:
• Slightly reduced manoeuvrability must be com-
pensated for by increased rudder area
I
k. U-->v
Jut
(a) Conventional snug clearing tnctics
(b)Boom pivol points Stern -beam trawler
(c)(d)(e) Snag clearing tactm Stern -beam trawler
Safety block decreases inclining lever
Fig 3. Beam trawling
[576
Principol dmtntiont
Brtodth mid.
85ft 3 |/2to (26.00m)
75ft 3 1/2 n (23.00m)
23ft 7 1/2 in ( 7.20m)
Depth mid. to maMtck 9ft 8 in ( 2.93m)
Dipm mW. to fo-cvto dtck 16ft 9 in ( 5.10m)
Draught loafed loci, kul 8ft 2 l^in ( 2.50m)
. Multi-purpose fishing vessel
[577]
• Safety is increased (see fig 3a, Conventional). When
fishing with the current and one rake gets caught,
the stern beam trawler will not tend to turn in
the tide as the conventional beam trawler does,
thus avoiding dangerous situations in which the
current might capsize the vessel. To free the caught
rake (figs 3b, 3e, 3d, 3e) the stern beam trawler
should move astern, meanwhile either swing the
boom into the line of pull or shift the warp-
block attachment from the derricktop to the bul-
wark (in this vessel, to the gallow), to increase
the hoisting power on a short lever and then the
rake can be pulled free of the obstruction. This
" going astern " manoeuvre has other advantages
over the conventional method of turning up into
the tide. The warp will not wind around the
obstruction and the warp of the other rake will
neither shave under the keel and foul the pro-
peller nor handicap completion of the turn by
swinging over the after-deck. There is little chance
of the above happening when using the winch
only, even though the vessel will not go astern in
a straight course (hydrofoil action)
Mexican multi-purpose fishing vessel
First vessel completed in the Netherlands in December
1963.
Particulars
Loa
Lpp
B
D
Power .
Winch .
Mechanical drive off main engine
85 ft 3± in (26 m)
76 ft 4 in (23.20 m)
23 ft ?i in (7.20 m)
9 ft 8 in (2.95 m)
2 x 240 hp at 1 ,500 rpm reversible
reduction
2 x 600 fathom f in (19 mm) wire
2 x 600 fathom g in (9.5 mm) wire
Tonnage . . 125 GT
Hold capacity. . 3,500 ft3 (100 m3)
Fuel capacity . . 1,320 ft3 (37.8 m3)
Fresh-water capacity 700 ft3 (20 m3)
Accommodation . 9 to 16 persons
Gear . . . (a) bottom and mid water trawl,
single or two-boat stern traw-
ling
(b) beam trawling with two-door
shrimp nets or ground rakes
(c) purse seining
Fishing equipment
Basic
• Four-drum winch on upper deck : controls in the
wheelhouse
• Bipod fishing mast (enveloping the engine ex-
hausts) carrying two derricks, coupled together
when trawling, providing suspension for gilson
block and net roller, or used independently when
beam trawling or purse seining
• Two removable gallows mounted on top of bul-
warks aft, port and starboard
• Removable fishponds on deck, adjustable to suit
the fishing system
Special
• Framework to support guide blocks in different
positions and gilson blocks when beam trawling:
also providing a canvas sun awning over the
working space and fish hold
• Power block, purse davit and other equipment for
seining
• Longline capstan
The first of five vessels of this type was for fishery
research in the Gulf of Mexico, exploration of new fishing
grounds, testing the most adequate fishing methods and
C
Fig 5. Multi-purpose fishing vessel
[578]
instructing new crews. For this reason, she has been
arranged with air conditioning and accommodation for
up to a crew of 16. All these vessels have refrigerated
fish holds supporting the ice-cooling system. The high-
speed twin-engine arrangement and wide casing enables
engine exchange and shore overhaul (fig 4 and 5).
Tactics
When pursing the seine over the side from either amid-
ships (Pacific system, fig 6) or further forward (Icelandic
Fig 6. Pacific method of purse seining
system, Jakobsson, 1964), the pursing force tends to pull
the vessel into the seine. A powerskifT, bowthruster,
active-rudder or other means are needed to keep the
vessel free of the net.
In an attempt to achieve higher efficiency, stern purse
seining has been proposed. In fig 7a, the seine net is shot
over the starboard corner of the transom, while a circular
course is steered. When the circle is completed, the buoy
is picked up. The vessel then turns stern into the wind
and the purseline is attached to the drum through the
port gallow, and the towline is belayed on the portside.
The starboard purseline is taken on to the starboard
drum through the starboard gallow. The corkline is
hauled through the powerblock and pursing starts on
both drums simultaneously. In fig 7c pursing is com-
pleted, and in fig 7d the rings are released from the purse-
line and put on the bulwarkrod, the purseline being re-
wound on the starboard drum. The port spreader boom
can form a brailpit for brailnet or fish pump. The
following advantages of stern purse seining may be
noted :
• The vessel can manoeuvre with rudder and
propeller counterbalancing the pursing force of
the winch without any auxiliary aid of skiff
• The fish are frightened into the net by the propeller
• Deck equipment of stern trawler can be used, a
powerblock being the only addition
• A four-drum winch can handle all operations —
pursing, towing and brailing
• The guide frame may be used as brail boom
• No hydraulic boom swingers are necessary, merely
topping
0
Fig 7. Purse seining over the stern
• The rampless stern trawler has ample deck space
to store two complete Icelandic seines — one deep
and another shallow, but both with double bunt
ends
• When brailing with stern to the wind, the whole
system (ship and net) is in an equilibrium position
Triple-rake scallop dragger-stern trawler
First such vessel completed in Canada in December 1962.
[579]
T2
Particulars
Loa
Lpp
B .
D.
Power .
Winch .
116 ft 6 in (35.5m)
99 ft (30 m)
26 ft 3 in (8 m)
14 ft (4.25 m)
660 hp at 750 rpm reversible
reduction 3 : 1
2 x 600 fathom $ in (22.22 mm)
wire
2x600 fathom £ in (12.7 mm)
wire
Mechanical drive off main engine
Tonnage
Hold capacity.
Fuel capacity .
Fresh-water capacity
Accommodation
Gear
350 GT
7,000 ft3 (200 m3)
2,060 ft3 (62 m3)
875 ft3 (25 m3)
20 persons
(a) Granton bottom trawl
(b) midwater trawl
(c) three scallop rakes 10 ft (3 m)
wide
Fishing equipment
Basic
• Four-drum winch on shelterdeck: controls in the
wheelhouse
• Single pole, unstayed, fishing mast with trans-
verse outrigger to provide the suspension for
gilson block and net roller for stern trawling
• Fixed gallow structures, part of the ship's sides
• Usual fishponds on deck
Special
• Guide frame and bag arrestor designed for
directing and holding heavy bags when trawling
in rough weather
• A longitudinal outrigger at the mast aft
• Two short, but sturdy, derricks for towing
scallop rakes
• Two hydraulically-driven topping winches for the
above-mentioned derricks, controlled in the
wheelhouse
• A hydraulically-operated stern flap for emptying
the scallop rakes, controlled at the stern
The vessel is designed for operation in the rough
weather and ice of the Canadian Atlantic grounds. The
design should provide maximum seaworthiness, comfort
and protection. Except for the fishdeck aft, which has
three high sides, all work spaces are entirely closed (fig 8,
General arrangement).
H61t *m 1302m)
99ft Ota (300 m)
26ft Sir t tOm)
14ft On ( 42m)
21ft 2m I Mm)
12ft «n( Urn)
_J
Fig 8. Trawler-scalloper
[580]
f chafing bars
/clubstick
fixed X
h^oms "**
©
©
9. Conventional Canadian scallop dredging
[581]
Tactics
The triple-rake stern scallop dragger enables more pro-
duction than the conventional two-rake system (much
like beam trawling, figs 9 a to e): Two rakes 10 ft (3 m)
long with wire bags are towed on the adjustable forward
gallows. The rakes are then hauled up under the gallows
and the boomrunners attached. They are hoisted over
the bulwarks, lowered on to the deck, and then the club-
stick is hoisted until the bag empties, then the rakes are
laid on the bulwark rail. The sliphooks are attached and
the rakes are re-shot. The three-rake system operates as
follows: two are towed on short derricks, just reaching
outside the vessel to port and starboard. The third rake
runs through the centreline outrigger aft. Towing time
(about 20 minutes) is just enough to maintain a rotary
operation. Two rakes are at the bottom all the time,
while the third is being hauled, emptied and shot again.
This increases production by about 50 per cent. To
accomplish this, each rake, when it is due for hauling
just before it breaks the surface, is brought in at the
vessel's centreline and pulled up the stern flap. There it
is caught by its clubstick (at the bottom of the wire bag)
in leads and chocks on the flap sides. The flap is over-
turned hydraulically, allowing the contents to slide down
the deck. Finally the flap returns to its original position,
ready for shooting the rake again (fig lOa, b, c).
A further advantage of this flap is that the rake,
weighing about 4,000 Ib (2,000 kg), is being held tight
during this whole procedure: in the conventional
operation, the heavy rake sways from the top of the
conventional hoisting derrick, over the crew. A specially-
developed self-loading conveyor carries the shells from
the aft deck into the processing area, and serves as a
moving tabletop where the work is done under stan-
dardized conditions.
Fig 10. Triple rake stern scalloping
[582]
U1SCUSS10I1 I Developments in the design of vessels and gear
DEVELOPMENTS FOR BETTER OPERATION
Labour easing
Hovart (Belgium): Rationalization, when applied to handling
of gear and catch, means a rationally equipped fishing vessel
with the right man at the right place. As in other industries,
work-time studies on fishing vessels are necessary. It is impor-
tant to know what must be improved, what can be improved
and what cannot, how the improvements can be carried out,
what gain of time and labour can be obtained and what are
the costs involved, etc. To solve these problems it is necessary
to have quantitative or numerical values of labour in general,
and of the labour of crew members in particular.
Time study measurements have been carried out in Belgium
on coastal vessels equipped for beam trawling. On different
vessels, all handling, even the mechanical, c.g, the work done
by the winches, was analysed in detail. The handling was split
into two categories—handling of gear and handling of the
catch— each category was further subdivided so that every
movement in the handling of the fishermen could be noted.
For each of these movements the MTM timetables were used
to find the working or action lime. Many observations are
required and the collaboration of the fishermen is essential.
But to control the investigations initially some of the handling
was measured by means of a stop-watch, then also model
tests were carried out. These tests are very important to test
improvements before being brought into practice.
Many improvements are possible, even with small altera-
tions, e.g. regarding the procedure of handling, the order of
working of the crew for shooting and hauling the gear, the
handling of the catch, the location of equipment, etc. It
should be stressed that rationalization does not always require
more complicated equipment, as other factors, such as costs,
quality of labour also have to be taken into account.
It is certain that the shipbuilding industry can obtain useful
data from time studies. To mention a few: the type of equip-
ment, the advantages of the equipment to be installed, the
working deck, the construction of the fish hold, etc. Time
studies are important for the owner and the fishermen. Not
only a clear idea about the division of work on board can be
obtained, but also arrangements can be made to facilitate the
work, to permit more rest, etc., and this is an important factor
in solving the crew problem.
It should be mentioned that the first publication on time
studies on coastal vessels is nearly ready, and it is hoped that
it will be useful for the fishing industry, since on an optimum
fishing vessel, optimum labour conditions are necessary for
the final goal to be reached.
Drum system approved
Roberts (UK): Roberts said he was not a designer, nor an
engineer, but a fisherman now engaged in fleet management.
In his youth he spent many weary years as a deckhand stoop-
ing to get deckloads of Arctic cod and occasionally floating
overboard and successfully back again, and from those days
he had tried to improve the working conditions of fishermen.
Labour saving in handling trawls is the ultimate aim of those
who have a vessel manning problem, whether it be economic
or just the lack of available crew men.
Roberts had seen nothing better than the drum system of the
Canadian stern draggers, described by Reid. Some years ago
he had the privilege of fishing from one of those vessels but
hesitated to adopt the system in Ross Daring because they
needed to use fairly heavy bobbins on rough ground in the
North Sea. It now seems that drums well built as described
in Reid's paper can cope with bobbins up to a diameter of
18 in (0.45 m), and this discovery may well be one of the most
important in recent years as a labour-saving device in handling
trawls.
Reid's suggestion of fitting two drums side by side is
particularly good. Two trawls are then instantly ready for use,
and in the case of North Sea fishing, possibly 5 to 10 per cent
more fishing time would result. Who can ignore a 5 per cent
increase in production? Also, the skipper can use his two
drums alternately for comparative fishing trials for new nets
and net materials. There is no reason why, on a large vessel,
another deck is used to carry two more drums with a codcnd
ramp in between each pair of drums.
Many fishermen today cannot mend their nets and much of
this work is done ashore by older men. The vessel could back
into harbour, moor astern and unroll the nets conveniently
and take on the repaired nets from the previous voyage.
One day there will be an efficient gutting machine for small
vessels, but until then every effort should be made by designers
to get fish to the fishermen at waist height. Reid's paper does
not discuss this point — perhaps his fishermen do not gut, but
still use pitchforks to stow fish.
Ohlsson (Sweden): Could net drums, as described by Reid, be
used on Swedish-type side trawlers for fishing in the rough
weather conditions in the North Sea?
Traung (FAO): Reid's suggestion for drum trawling belongs
to the most interesting possibilities to improve many fishing
boats in many parts of the world. Reid mentioned that care
should be taken not to use too heavy trawls. With the intro-
duction of lighter netting, the weight of these trawls could be
reduced. It would be very interesting to hear Reid's reaction
to using drums even on side trawlers.
Benefits of net drum
McNeely (USA): One of the principal advantages of the net
drum is its utility in poor weather conditions, when strapping
in a net is both hazardous and time-consuming. Minor
disadvantages include the necessity of removal of the net for
repairs to webbing. Whenever very long nets are used, rapid
retrieval is a distinct advantage.
Reid's paper shows separate slots for the groundlines. Most
Pacific North-west trawlers do not have this feature, but from
the standpoint of safety, it would seem desirable to have them.
Some hazard is present when fishermen guide the bridles on to
[583]
the drum (level winding). The separate slots reduce that
hazard.
Shelter
Frechet (Canada): In Canada where fishermen are exposed to
extreme weather conditions, ingenious shelters were recently
developed. The Great Lakes steel gillnetter or combination
Fig 7. A Great Lake steel gillnetter outside view
dragger may look a little like a submarine, fig 1 and 2, but
offers excellent comfort, since the deck area is totally enclosed.
Portable side covers are removed on hot summer days for
open-air circulation, but just one cover is removed on cold
winter days. The gear is set through this opening; a sliding
canvas may close it before fishermen are ready to trawl. The
side opening, which extends into the roof, permits hauling a
Fig 2. A Great Lake steel gillnetter inside the shelter
full codend. These principles are now applied to stern trawlers
and even side trawlers plan to cover the whole deck in the
same way. Recent stern ramp trawlers are not only of the
"tween" deck type, but trawling operations are carried out
under shelter on the lower deck.
Canadian longliners are usually partly sheltered under a
canopy. On the Pacific coast, the 68 ft (21 m) combination
boats which longline halibut in the Bering Sea, some 2,500
miles away, usually carry a portable covering superstructure
aft. It is sometimes made of plywood, otherwise of canvas over
a steel pipe framework, of aluminium or even of translucent
reinforced fibreglass. Atlantic types of longliners have a
canopy with portable side covers. This construction extends
behind the forward wheelhouse and usually covers a wide well.
Recent scallop draggers are provided with excellent shelters
located on each side of the after superstructure. Recent side
trawlers have the winch totally enclosed either in front of the
poop deck superstructure under a starboard side canopy, or
under the whaleback.
There are a number of other shelter arrangements not
located on the main working deck, For instance, the hurricane
decks are fitted with wooden or translucent plastic wind
deflectors and crows-nests are totally encircled by removable
plexiglass windows. On many vessels, the comfort of fishermen
working in cold weather is ensured by radiant heating. The
latest installations involve the use of quartz infra-red lamps
or reflector heat lamps.
One must object forcefully to naval architects or others
referring to fishing vessels as "working platforms", as if they
can be open to all bad weather conditions. Fishermen now
need and deserve "a home away from home". In the Hardy
memorial lecture (page 25), Rinman rightly stated: "A
happy ship is an efficient money-making machine." A pre-
requisite to happiness consists of adequate shelters to provide
comfort for fishermen.
Roberts (UK): With too much shelter the skipper may well
lose some control over his ship and crew. By covering all the
working spaces, top hamper is added and a skipper used to
handling a ship in rough seas will have the extra hazard of
windage to contend with. Also, if he cannot easily see his crew,
he will be faced with even more difficulties.
Traung (FAO): Disagreed with Roberts' remarks because
there will not be anyone wanting to crew fishing vessels if no
better shelters are provided in the future. With care in design
and close-circuit TV it is possible to keep each corner under
control.
Reid (Canada): Shelter need not obstruct the master's view
of the working deck, as such shelters are most necessary to
stop wind and spray and can therefore be open at the top —
particularly needed for hauling codend over the stern. A
check of the sight line from the bridge wing will show that
the winch man can be easily seen, and this is the important
point.
Internal heating facilities
Rawlings (UK): Regarding the matter of heating shipboard
accommodation in temperate and sub-temperate climates,
in the larger classes of steel fishing vessel, consideration might
generally be given to installing air-cooled engines to drive the
generators and auxiliary plant, the hot cooling air from the
engine can then be harnessed for heating — provided this hot
air is controlled in ducting. This practical method has already
been used with advantage in warming crew cabins and wheel-
house, but more particularly in circulating hot air across the
tank top, in way of machinery space in the larger steel vessels,
thus combatting condensation in a particularly vulnerable
part of the ship, usually subjected to corrosion attack.
Safety of the crew
Lyon-Dean (UK): Reid places quite high the importance of
safety. Very little has previously been mentioned about safety
precautions for the fishermen as distinct from safety of the
[584]
vessel. In the Moray Firth, scarcely a week passes without some
fisherman going overboard by being caught in the bight of a
rope or being swept over the side by a rope jumping from its
fairlead. It is found that, although certain safety devices are
insisted on and others recommended, in practice they are
usually disregarded. Slippery decks, slippery iron-runged
ladders are a potential source of injury, and the major injuries
of oil skins catching in the winch drums are well known. As a
doctor in a fishing port, Lyon-Dean saw and treated these
casualties and he knew that many of them could have been
avoided.
He asked designers, engineers, work study engineers
and fishermen to co-operate and use their combined intel-
lectual ability and common sense to make the working areas
at sea as foolproof as possible so that safety conditions on
board fishing vessels will be comparable with those in a
factory on shore.
To reduce accidents
Minnee (Netherlands): Lyon-Dcan had stated that many
accidents still happen. Several ways in which these can be
minimized are:
• Keep the warps and other wires as far above the work-
ing deck as possible, out of the way of the men
• Winches should be remote-controlled so that the whole
control of the vessel is centralized— good all-round
visibility is necessary, especially from the wheel-
house to the fish deck aft. The wheelhouse for this
reason should not be too fnr forward. There should
be no view-obstructing shelter as far as the gear
operation is concerned, so that the skipper can control
the work of his crew. However, for processing, the
mate can take over operations and therefore excellent
shelter can be provided in this area
• It is important to bear in mind the improved location
of accommodation. For crews sleeping aft or midships,
movement is far less
• Non-slip (and anti-corrosive) deck covering can be
found in asphalt compounds
Seakeeping
Kilgore (USA): Blount and Schaefers report the paradoxical
result that adding a deep bar keel decreased the rolling period.
Increasing the damping coefficient and increasing the added
inertia both cause lengthening of the natural period, and yet
in this case the opposite effect occurred. The notion that the
rate of extinction of excited motions is important in seakind-
liness persists so firmly among people who rely on their
intuition for understanding of physical phenomena that a
brief review seems warranted.
The equation of periodic motion with damping, whether
the damping be linear or of some higher order, tells all the
story there is to tell, with very high accuracy. The solution
of the equation yields the natural period of motion,
where the meaning of the symbols can be found in the
glossary. The mass moment of inertia here, Ixx, includes the
added inertia of entrained water, and 2N is the damping
coefficient. This period determines the seakindliness in roll,
the habitability and hence the usefulness of the ship. The
damping rate, determined by the magnitude of the coefficient
2N, does cause the period to be a little longer than it would
have been in the absence of any damping whatever, but
JV2//ZI2 is so small in comparison with GA///« that for
practical purposes it may be ignored.
On the other hand, note that increasing the moment of
inertiajias a most significant effect on rolling period, provided
that CM is not increased concurrently. Bilge keels and bar
keels achieve their effect commonly by increasing the virtual
moment of inertia, entraining large masses of water at a
distance from the axis of roll. Indeed they also increase the
damping rate, but this part of the function has a negligible
result.
Now, if metacentric radius is increased by adding heavy
appendages, the rolling period may be decreased in spite of
the augmented moment of inertia. This evidently is what has
been accomplished. Although the deep massive bar keel has
resulted in an increased hydrodynamic mass moment of inertia,
and has also increased the gyradius of the ship itself, it has at
the same time jowered the centre of gravity of the ship and
thus increased CM. The total effect is a reduced rolling period.
The faster extinction rate will not be noticeable when at sea
the motion is constantly re-excited. Seamen always would
choose the ship with slow roll and slow extinction rate before
a ship with fast roll, no matter how rapid the extinction rate,
if such an alternative were presented.
Solution sought
Lee (UK): Would Blount and Schaefers explain why, if it is
necessary for the propellers of the inboard installation in
Hiodon to be completely above the bottom of the hull, the
propellers of the inboard/outboard installation shown in fig
16 in their paper are below the bottom? Are there any special
arrangements for avoiding grounding of these propellers and
when the vessel is grounded how is it got off* ?
The remarks about the effect of bilge keels and deep bar
keels are of interest. May it be stated whether such protections
on the vessel's bottom affect the performance of the fish finder
and depth sounder.
Sehnan (UK): Blounl's and Schaefers' fig 19 referring to
rolling tests with model of Uncatenu is very confusing. What
is the difference between the four curves given for the naked
model ? What were the dimensions of the bilge keels and what
were the results with these bilge keels alone? To what does
the full line in fig 19 refer?
Authors* replies
Blount (USA): In reply to Kilgore on seakecping: The net
difference in GM resulting from the weight addition of the
bar keel is apparently in the order of 2 per cent for the full
size vessel. This is evidently insufficient to cause the indicated
change in period. It is unlikely that weight and KG changes
in the model were held precisely to scale as far as the bar keel
was concerned, since the effect being investigated was
decrement of amplitude rather than difference in period. It
is also thought likely that model weight changes were below
rather than above scale value. There is some doubt, therefore,
that the effect cited in the discussion accounts for the change
of period, which in any case has the status of a corollary
observation without relevance to the primary object of the
test.
Selman wanted to know the difference between the four
curves given in fig 19 for the naked model. The only difference
among the four "naked model" curves shown on fig 19 is
the initial angle at which the model was released. All were
plotted for zero speed of advance. The slopes should all be
the same, but are not. An average of the four slopes is
probably as good as any one of them.
In reply to Selman's queries regarding the bilge keels:
the dimensions were 39 ft 6 in (12 m) long by 18 in (0.45 m)
wide (full ship size). No tests were made with the bilge keels
[585
alone. He also asks about the full line in fig 19; this is for
the model with both bilge keels and bar keel attached, at zero
speed of advance. The arrow marked "With Bilge Keels" on
this diagram should actually lead to this line. The arrow
marked "Without Bilge Keels'1 should go to the dashed line
instead of the dot-dash line.
Schaefers (USA): In designing the Hiodon it was felt that,
since the vessel was scheduled for experimental operation in
a recently filled reservoir, grounding would be a problem
because information concerning bottom conditions and water
depths was unavailable. Accordingly, the vessel was designed
with a tunnelled stern to allow the rudders and propellers to
be completely above the bottom of the hull. Initial operations
indicated that the replacement of the standard engine arrange-
ment with inboard/outboard propulsion units and elimination
of the tunnel stern would be desirable for the reasons
stated. Even though grounding will certainly occur, and the
propellers of the inboard/outboard units will be below the
bottom, these units allow the entire submerged portion of the
unit to be raised through a 90 degrees angle. Thus, when the
drive portion touches bottom, the unit automatically raises. If
the vessel actually becomes grounded, the unit can be set at an
angle so that the propeller is above the bottom. The propeller
action is then reversed and the vessel backed off.
With regard to the effect of bilge keels and deep bar keels
on the performance of the echo sounder and echo ranger, no
adverse performance of either type of unit has been reported
from such vessels now in service.
TUNA CATCHING
Ando (Japan): The main problem in tuna fishing in Japan is
the low profitability, due to prolonged days for one voyage
that has caused the following tendencies. First, the size of
boats is to be smaller than 300 GT. Until 1960, most people
wanted to have boats over 300 GT, but later it was found that,
to have a full catch in such a large boat, they had to make
voyages of more than 200 days. Naturally, that raised serious
problems, how to get fuel supply. Therefore, smaller boats,
less than 300 GT, are now preferred so as to shorten the days
of a voyage. Second, the temperature of the fish hold has been
lowered from 0 to -13°F(-18 to 25°C) and the freezing
room from -22 to -40°F (-30 to --40°C) to be able to
improve the quality of frozen fish during long trips.
Thirdly, there is a requirement to study more about labour-
saving to secure the necessary labour and to increase profit-
ability. However, the fishing technique is so delicate that much
improvement cannot be expected in the near future. On the
Government's suggestion, a special committee has been
established, in co-operation with a research organization, a
fishermen's organization and suppliers of various equipment,
to find suitable solutions to all these problems. Apart from
these problems for large longline tuna fishing boats, there are
those with the small-sized tuna fishing boats of less than
40 GT. As the Government did not require approval for the
building of such boats, they have increased very much in
number since 1961. They started to look for fish far away in
the South Pacific. They were naturally overloaded, and many
accidents occurred. Therefore, finally the Government was
forced to place their construction under control, limiting the
number of boats and placing minimum requirements on the
boats.
In order to solve the problems with decreasing catch and
increasing days of voyage with large fishing boats, it is
considered to be one solution to carry small catcher-boats on
board, and this catcher-boat system has been recently
employed by boats of less than 500 GT. The stability of the
mother boats when loading and unloading the catchers has
to be carefully considered. So far no trouble has occurred.
Tuna purse-seining
Guicheney (France): Since about 1956 fishing for tuna in the
tropics has developed considerably, France being one of the
countries interested.
The earliest craft confined their searching to the immediate
vicinity of Dakar. Nowadays tuna boats travel as far as Pointe
Noire, and their range is extending a little each year with the
increase in the size of the fleet. The method most widely
employed is that of the rod and line using live bait.
Information accumulating chiefly since 1960 on fishing with
large seines in the Pacific and on the at times spectacular
results obtained with this method has led to its being tried out
in West Africa. Several attempts made by American tuna
clippers in the Gulf of Guinea in 1961 and 1963 met with
complete failure. At the present time a fleet of Japanese tuna
boats is understood to be trying out netting techniques in
these parts, though without much success either. In nine
cases out of ten the encircled fish dive under the net and
escape at an astounding speed. Nor does deepening the nets
provide an answer to this aspect of tuna behaviour, which does
not seem to be so inexorably the rule with species in the east
Pacific. It would be interesting to try to explain this difference
between fish of the same species, but that is not the purpose of
this contribution.
Experience also shows that good results can only be hoped
for by combining methods, involving the location and
attraction of schools of tuna by the use of live bait followed
by their capture by seining. These remarks, of course, refer
to fishing grounds with which Guicheney was personally
acquainted, and to operations conducted in the daytime.
Fig 3. French tuna seiner Danguey
A steel-hulled tuna boat, Danguey (fig 3), was refitted to
handle a large-size tuna seine; it has the following principal
dimensions:
Loa 121 ft (37m)
B 25.6 ft (7.80 m)
D 13.5 ft (4. 10m).
It has one propulsion engine, 650 hp, and two electric
generator sets, 200 hp, 120 kW. The catch is stowed in eight
holds with a total capacity of 5,300 ft3 (150 m3). Freezing (in
brine) at -0.4 to -4°F (-18 to — 20°C) is provided by a plant
comprising three units extracting 75,000 kcal/h, i.e. a total of
225,000 kcal/h.
Deck gear listed
Deck gear consists of the following main items:
• One hydraulic winch, 120hp, with a lifting power of
12 tons at empty drum. The winch is of the traditional
[586]
Fig 4. French tuna purse-seiners use trawl-winch type winches and
extra small winches
trawl-handling type, with two drums and two gipsies,
and is mounted astern, fig 4
• Two trawl-type gallows mounted on the port side,
fig 5. The forward end of the purscline is hauled on
the forward gallow, the rear end on the rear gallow;
the purse rings are thus supported between the two
gallows. This arrangement, which differs from that
traditional with trie- Portuguese gallows widely used by
American tuna seiners, has given complete satisfaction
• One-drum, one-gipsy electric winch, 35 hp, for hand-
manoeuvring the brcastlinc of the rear wing. This
winch is platform-mounted nstern, above the main
winch, fig 4
• One hydraulic power block, 35 hp, mounted at the
top of a fixed tripod mast
Fig 5. French tuna purse-seiners use double gallows
HK 6. Derricks mounted on gallows help support cork line
• One derrick, 2.5 tons capacity, chiefly for hauling the
excess webbing once the purse has been formed. This
derrick is mounted at the foot of the port tripod and
can be swung sideways. It is driven from a small hand
winch and off one of the gipsies of the hydraulic
winch
• Two derricks, 1 .5 tons each, mounted on the respective
gallows, fig 6. These derricks can be swung to a
horizontal position, at right angles to the axis of the
boat. Their purpose is to support the floatlinc by stout
slings during pursing
• A deck area of approximately 480 IV (45 nr;) at the
stern for stacking the net. The bulwark surrounding
this space has been raised 3.3 ft ( I m) and made to slant
inwards for the dual purpose of making it easier to
slide the fish on board and of ensuring adequate
frictional hold on the net which, on the inboard side
is stacked on wooden duckboarding with an 8 in
(20 cm) clearance above the deck
Net characteristics
The net had the following characteristics when it first left
the braiding sheds:
• Length (in fishing condition): 546 fm (1,000 m) in four
detachable sections of 136.5 fm (250 m) each
• The two middle sections were exactly similar, so that
the total length could be brought down to 410 fm
(750 m) if desired
• Depth: 69 fm (126.5 m or 1,265 meshes stretched)
• The webbing had meshes with 2 in (50 mm) bar
During the 1962/63 fishing season, it was decided to remove
one of the middle pieces of webbing and so reduce the total
length to 410 fm (750 m).
[587]
Trials with the original 546 fm (1,000m) length, showed
that the power required for pursing exceeded the capacity of
the winch whenever the sea was not absolutely calm.
Prior to the 1964 season, further modifications were deemed
necessary in order:
• To strengthen the last bunt. The original bunt was
fitted under the new one, replacing the earlier webbing
in such a way as to extend the selvedges to the entire
forward extremity of the net, where the fish concen-
trate
• To fit one zipper close to the bunt
• To replace the 0.55 in (14mm) chain by another of
4 in (10mm) diameter in order to reduce the sinker
effect
Methods of manoeuvre
To manoeuvre the net, a flat-bottomed, wooden, unsinkablc
(double-bottom) skiff of approximately 20 ft (6 m) length,
powered by a 35 hp outboard motor was used, fig 7, the
specific purpose of which was to hold fast the tow wing of the
net (running end of the purseline and forward wing) in order
to aid the seiner to set and haul the forward breast line and the
purseline.
Fig 7. French purse-seine skiff
During the first two seasons a small tuna boat (non-
refrigerated) casting live bait was used. Present efforts are
being directed to rendering the seiner independent of the
auxiliary boat by having specially designed skiffs capable of
being hoisted on board.
Once on the fishing grounds, the two craft (seiner and bait
skiff) take up positions half a mile to a mile from each other.
The net is carefully laid out on the seiner, corks to starboard,
webbing in the middle, sinkers to port, and rings hanging over
the rail (all other currently used arrangements with smaller
seines have caused tearing or other damage). The purseline is
wound on the port winch. The running end passes through
the gallows and the rings and is seized on the fiat-bottomed
skiff, which is towed by the seiner while the end of the
purseline and breastline arc roved until all is ready for
shooting.
The moment a school of fish is sighted, the bait skiff heads
in that direction and tries to hold it by throwing live bait
overboard, If the seiner itself is the first to reach the school it,
too, throws out bait in order to gather the fish around it
while awaiting the arrival of the skiff, which takes over the
task of holding the school. The manoeuvre described varies
considerably in time depending on the reactions of the bait
and how it presents itself. In a case of a compact school rising
easily to the bait, the actual baiting lasts only a few minutes.
Otherwise, fairly scattered fish or fish lying at some depth,
must be brought together or nearer the surface and, in an
extreme case, the operation may last several hours. The role
and the competence of the man in command of the skiff are
decisive to the success of the entire fishing operation.
All the time that the skiff is manoeuvring, the seiner stays
a fair distance astern and to leeward. The skipper of the bait
skiff keeps in touch by radio with the skipper of the seiner,
and tells him when, in his judgment, the school is sufficiently
compact. Then the skipper of the seiner cruises in his direction,
keeping to leeward, and arrives at a position crosswise to the
wind and astern of the skiff. He then releases the net and
circles the bait skiff which continues to throw overboard
large quantities of live bait until encirclement is complete.
A hundred metres or so from actually completing the circle,
the seiner shuts off its engines. Braked by the net, it continues
in its course by impetus until coming to a virtual standstill on
a level with the skiff. The end of the purseline is then cast
aboard the seiner, passed over the roller on the forward
gallows and wound on to the port drum. Then both drums are
wound simultaneously. When the breastline arrives on board,
the winch is stopped for a few *<*fffi<}& in order to unloop the
purseline. The forward wing is'iirmly fixed on the bow side
of the forward gallows. The pursing operation is completed
by shipping the rings between the two gallows.
Precision needed in operation
The encircling operation needs to be conducted with some
precision if the rear wing is not to leave the seiner. If that
happens, the rear breastline is dipped and the rear wing must
be hauled again before pursing is attempted. Pursing and
traction on the wing requires too much power for these
operations to be executed correctly at one end and the same
time. In any case, experience proves that no time is lost by
completing them in two distinct stages.
Once the rings are on board, the skiff relinquishes its end
of the net (at a predetermined point on the float line) and goes
to leeward of the seiner. A bridle is passed between the two,
whereafter the skiff helps the seiner to get clear of the net, if
that is necessary, and in any case to avoid fouling it.
While this is going on, the rear wing on the net is passed
over a powered block and hauling commences. The rings are
slipped, one by one, off the purseline as the net comes in.
The net is stacked on the afterdeck ready for the next set.
Once the last ring is aboard, the float line is looped on to
two gallows and the catch drawn up in the bunt. The first fish
are lifted aboard.
Experience shows that there are always a number of fish
gilled or otherwise caught up in the folds of the net, and these
have to be removed by hand. Gilling may take on serious
proportions and cause trouble in the case, for example, of
skipjack. If the catch is large, most of the fish gravitate to the
bottom of the bunt and no longer struggle, in which case it is
necessary to haul on the bunt webbing to dry the fish as much
as possible. A brailer with a handle some 40 ft (12 m) long is
hooked to the derrick and plunged into the catch, which can
thus be hauled on board by lifts of 900 to l,1001b (400 to
500 kg) a time.
The time required for the various operations described is as
follows: 5 to 7min for encircling; llmin for pursing;
approximately 45 min for hauling the net and 30 min readying
the gear for the next set. The time for actual hauling of the
catch on board naturally varies according to the catch.
[588]
Some adjustments needed
In December 1962, following a number of satisfactory sets
(22 tons albacore caught in the first few days) difficulties arose
due to the excessive length of the net— at the time 546 fm
(1,000 m). This was shortened to 410 fm (750 m) in order to
reduce the great pull exerted on the net by the swell or the
wind, however slight, and to facilitate, first the braking and,
secondly, the manoeuvring of the rear wing by means of the
main winch.
For this reason, and because the boat was out of service
while the conversions were being made, the number of days
at sea between 25th December and 28th April totalled no
more than 77. During these 77 days tuna were detected on
only 40 days, allowing only 37 actually for fishing, since on
3 days the schools detected did not rise to the bait and
attempts at shooting the net without carefully setting it were
unavailing.
Accordingly, the total fishing days represented only 48 per
cent of the time spent at sea, which, for a 325-ton total catch,
gives an average of 8.8 tons daily (consisting of about a
quarter skipjack and three-quarters albacore).
Average haul per set, which was approximately 5 tons in
January and February rose to 10 tons in April.
A 35-hp electric winch was installed for the purpose of
helping the manoeuvring of the brcastline of the rear wing;
an additional derrick was also installed in order to take up
excess webbing during pursing. Other modifications concerned
the strengthening of the net and a reduction of the weight of
the sinkers.
During the 1963/64 campaign, with no interruptions this
time, the average monthly catch -ame to approximately
102 tons, with the following proportions:
albacore
skipjack
70 per cent
30 per cent
Catches would certainly have been 10 to 15 per cent higher
than this, considering that schools of skipjack were frequently
disregarded in order to continue looking for albacore.
Method suited for wide adoption
The number of days when fish were detected amounted to
about half of the total spent at sea and, practically speaking,
for each day when fish were detected, a catch was also made,
so that the fishing method here described can apparently be
very widely adopted. Only on very few occasions weather or
fish behaviour of such a nature was encountered that a catch
could not be made once the fish were detected. On each day
when fish were detected, the catch averaged 8.4 tons, i.e.
about 4 tons for every day at sea. For the campaign as a
whole the average catch per set was slightly over 5 tons.
The observations made during the Danguey's first two
campaigns off the African coast bring out a number of points
which are decisive for the success of tuna seining.
The tuna seiner, Dangucy, caught more than double (a ratio
of 100 to 46) the catch of the ten freezer tuna boats with the
best performances using the rod-and-line and live-bait
technique.
Nevertheless, it should be noted that daily catches were
largely the same in 1 962/63 and in 1 963/64 despite the technical
improvements introduced, and that to achieve even that
result more sets had to be made. This may be attributable to
two causes: first the method of baiting, and the second, which
seems sufficiently definite to warrant mention here, the
depletion of the fish population (this doubtless subjective
impression should perhaps be taken with due caution). Yet
the threat that seems to hang over the tuna fleet— namely, a
decline in catch in the future, should be seriously examined.
Type of bait
The bait skiff is extremely important, and it is reasonable
to suppose that, with a perfected method, markedly different
from that used in rod-and-line fishing, yields with seining
could be boosted by some 30 per cent. This statement is based
on the following considerations :
• Small-size bait is preferable to the medium-size used
for rod-and-lining. Baiting should produce a "mass
effect"
• It is necessary to throw the bait very energetically into
the water during the encircling operation that takes
only a few minutes. The relatively slow procedure
with the rod is out of the question at such a critical
moment
• The crew of the bait skiff must on no account dip their
rods in the water— but this is difficult to avoid when
hands are used to rod-and-lining
All the same, a very rapid change is apparently coming
over crews, in favour of seining and the wider introduction of
bait skiffs should afford some solution to the problem.
Bait is still cheap, only about 2 tons being needed to land
100 tons of tuna. The essential thing, however, is that the
bait must be thrown into the water very energetically during
the encircling operation.
Except when the fish are very scattered, and generally when
they are found in company with schools of porpoises, seining
is possible whenever lining is; on the other hand, seining is
possible even when conditions preclude lining.
The seine used by the Dangncy differs from others by reason
of its relatively small mesh size (50mm) and not merely as
regards weight and dimensions. Generally, therefore, it is the
drag caused by the webbing in the water that demands extra
power for circling.
Important points
The following points should be emphasized.
Apparently the dimensions of the present net are very close
to the optimum. The use of smaller nets does not seem
appropriate because of the uncertainty of the tuna grounds
off the African coast. It is indeed possible to catch tuna with
relatively small 270 to 330 fm (500 to 600 m) nets, but this
involves a decidedly higher number of sets when fish may
not be taken at all. Besides a lower yield, it is by no means
unreasonable to hold that with a general use of excessively
small-sized nets the fish will "get wise" to the situation
sooner and, accordingly, be more evasive. The trouble in
certain cases in taking schools where rod-and-line methods
had already been attempted only support this assumption.
The adoption of larger nets would undeniably offer a
better average haul per set, though the greater time needed
for manoeuvring would offset the benefits so accruing, at
least with methods currently employed.
The rapidity of manoeuvring is a decisive element in the
efficiency of the method.
The arrangement of sinkers is very important and has little
in common with the standards prevailing in this field. For a
tuna net, the 8 Ib sinker weight per fathom length (2 kg/m)
of net is too little and, accordingly, steel purselines arc much
better than those made of nylon.
Lessening of the labour required for pursing must be sought
in a judicious design of the net and not in reduction of its
dimensions. Much can be done to improve new nets.
Tuna seine manoeuvring calls for the following gear:
A 2-drum, trawl-type winch (or American type seine winch)
with traction on each drum of at least 5.5 tons on half drum,
i.e. for a winding-on speed of about 4 ft/sec (1.2 m/sec) an
[589]
effective power on the two drums of about 140 hp, with the
facility whereby the entire power can be transferred to a
single drum when winding on is complete (in other words, a
tractive force on the purse line at that moment of between
8 and 9 tons). The capacity of the drum should be:
On one of the two drums 550 fm (1,000 m) 0,9 in (23 mm)
dia. warp
On the other drum 275 fm (500 m) 0.9 in (23 mm) dia.
warp (minimum)
Detailed requirements
The winch for rear breastline should be of the drum type
and have a brake, and a capacity of approximately 165fm
(300m) of fcin (16mm) dia. cable. The winding-on speed
must be quite low (1.6 ft/sec or 0.50 m/sec, at the most) and
the traction should be in the region of 2 to 2.5 tons. The
purpose of the winch is to provide a braking effect on the
boat and on the body of the net at those times when the rear
wing is attached to the boat only by means of the breastline,
and to lift the wing on board (where it is immediately roved
through the powered block). Jt goes without saying that it is
possible to relay this winch to the main one if one adds a
third drum to the latter.
There should be a powered block of sufficient capacity (the
35-hp rating is recommended) mounted at the end of a swing
derrick capable of taking 6 to 7 tons (static) load. The derrick
in question should have a 90 to 100U slew from the axis of
the boat (the slew excursion is limited by the position of the
rear purseline roller), and should preferably be able to peak
with a 3- to 4-ton load.
There should be a derrick of at least 2.5 tons capacity above
the forward warp roller. This derrick serves to lift the forward
wing until the first ring is reached in such a way as to hold the
net up close against the boat in order to prevent the fish
escaping through any open spaces that would otherwise be
created.
It is not possible to give an exact description of the arrange-
ment of the rollers, something to be worked out for each
individual case. Nevertheless, the principle adopted on the
Danguey is far better than the Portuguese gallows system
generally used on seiners. The system in question consists of
two gallows sufficiently far apart for the rings to be lifted at
working height above deck level between the two gallows
rollers and fall automatically on the deck without a derrick
being necessary.
The afterdeck, on which the net is stacked, measures about
485 ft2 (45 m2) in area, which leaves enough work space. It
does not seem possible to reduce that area very much without
paying some penalty, since the net when stacked reaches a
height of 6.5 ft (2 m) on the float line side in any case. The
bulwarks, especially the one aft, should offer a fair slope
(about 20 per cent slant on the inner side) and be free of any
rough edges. It is highly desirable that the bulwarks on the
chain and ring side should be lined with wood to diminish
noise when setting. The net must be stacked on duckboarding
with a 4 in (10cm) clearance above the deck to facilitate
draining.
Factors in manoeuvring
Manoeuvring the seine creates a fairly large upsetting
moment. A mean heel of at least 10° was recorded during
many sets. Now, since the boat has a displacement of about
500 tons and a metacentric height of approximately 2.1 ft
(0.65 m) the corresponding upsetting moment is of the order
of 17 to 18 tons ft (52 to 55 tons m). Clearly, when subjected
to this moment, the vessel must have an adequate reserve of
stability.
The earliest results obtained with the fishing method
described here may be taken as quite satisfactory. In 1966,
six or seven French tuna boats were setting out equipped for
tuna fishing with seines and live bait. However, these were
converted tuna longliners, of recent construction and modified
either while in building or after delivery. For the tuna seines
operating in the eastern Atlantic, provision must be made for:
• Fishing gear with the characteristics described above.
In particular, the dimensions of the net and power
rating of the winch should be generously calculated
• The employment of at least one bait skiff most of the
time during the fishing season. In order to ensure
sufficient autonomy in the seiner, the best solution, in
the light of current experience, consists in employing
power skiffs with a hold of about 70 ft3 (2 m3) in size
for live bait and diesel motors of sufficient power to
allow of a speed of at least 6 to 8 knots. The skiffs
should have a crew of two or three men of considerable
skill (since they make all the difference to the success
of a set)
• Carrying on board the seiner a sufficient quantity
(approximately 2 per cent by weight of the fish hold
capacity) of bait for the entire trip. Experience shows
that, fish mortality being what it is, the actual amount
of bait should not exceed 3 to 4 per cent by weight of
the water in the live wells. Assuming an average
storage density of frozen tuna at 0.65 (of the available
space), the volume of the live wells will need to be
about half that of the total fish holds
• A freezing plant able to handle daily peak hauls of
up to (exceptionally) 30 to 40 tons. Accordingly,
freezing-brine techniques are called for, and these in
turn require a heat exchanger and a reserve of chilled
brine
To the extent that one may legitimately extrapolate the
results obtained so far, it would be prudent not to assume
an average catch of over 8 or 9 tons for each day fish are
detected. Now, experience seems to suggest that with currently
available craft and gear, fish are detected on no more than
half of the days of a fishing trip. There seems to be little doubt
that much might be gained by improving detection methods,
by say, air scouting, high-power sonars and a better under-
standing of fish behaviour,
Varied lessons to be learned
Doust (UK): Kazama's paper is a most fascinating report on
the tuna longliner in Japan, and one from which many lessons
applicable to other fishing vessels can be learnt. The first
comment refers to the influence of catching rate on the ship's
size. The opening remarks amplify the importance of making
more realistic forward estimates of catching rates.
For example, it may be inferred that since recently-con-
structed vessels show a general reduction in size that the
earlier designs were developed on too optimistic a basis.
Exactly the same situations have occurred in the case of wet
fish vessels longer than about 160 ft (48 m) based in Western
Europe, and the application of some type of air-blast freezing
system in an attempt to increase the edible life of the catch
would seem worthwhile. By such means the time available
from commencement of fishing operations to landing can be
increased, thereby improving the quantity of saleable fish and
increasing the number of hauls per day at sea.
Other methods described
Beaudoux (France): It is customary to group under the name
of longliners, craft intended for a very wide range of types of
[590]
fishing, from tuna fishing in pelagic waters, of which the
Japanese provide the most notable example, to the working
of rocky bottoms where trawling is out of the question, this
latter method being used in particular by Scandinavian
fishermen.
Apart from the basic principle of longlining, the actual
applications are diverse in the extreme. Many studies have
been made on the two main branches of longlining, and this
contribution is limited to a brief summary.
(a) Faroes method— longlining for bottom species, fig 8
Grounds — Fresh fish: Faroes and Iceland banks. Salted
or frozen fish : Newfoundland and Greenland banks
Length of trips— 10 to 12 days in the case of fresh fish;
60 days approximately in the case of salted or frozen
fish
Fig 8. A Faroes longliner for bottom species, N< rnagcstur
Gear — The longline consists of a main line in sisal to
which are attached the branch lines carrying the hooks.
The main line is stowed in baskets in lengths of between
150 and 165fm (275 and 300m). Each craft carries
100 to 150 baskets— a total length of line, therefore, of
15 to 27 nautical miles (27.5 to 50 km). Buoys at 1.1 or
1.6 nautical miles (2 or 3 km) intervals for retrieval of
the sinkers holding the line down. A light buoy is
used to mark the beginning of the line
Operations — The lines are set astern from the main deck,
with the craft cruising at 7 to 8 knots. Hauling is done
onto the main deck aft and to starboard, using a
winch with horizontal warping heads. The above
operations and those involved in preparing the fish
need a 24-man crew
(b) Surface longlining for tuna, fig 9
Grounds— Generally speaking, all waters, whether seas or
oceans, near the tropics. Particularly abundant in tuna
are the Pacific around Fiji and Samoa, and the Atlantic
off Dakar
F ig 9, A freezer tuna hngliner for surface species* Daguitc
Length of trips— 25 to 30 days approximately in the case
of fresh fish; 60 to 75 days approximately in the case
of fro/en fish
Gear — In this case the gear consists of a main line in
synthetic material to which arc attached the branch
lines carrying the hooks. It is stowed in baskets in
220 fm (400 m) lengths, any one boat carrying a total
length of between 43 and 76 nautical miles (80 and
150 km), divided among 270 to 470 baskets. The float
line is supported by glass floats with bamboo perches
in between. Light buoys facilitate retrieval of the
lines and in some cases a radio buoy is also used
Operations- The line is set astern of the upper deck, the
craft cruising at 7 or 8 knots. The operation takes, on
an average, 4 hours with a 12-man crew. The line is
hauled forward, at a point level with the main deck,
and to starboard. Two winches with vertical warping
heads are used in this second operation which takes
9 to 10 hours with a crew of 24
The craft accordingly reflect, on the one hand, the fishing
methods used and, on the other, the climatic conditions to
which they are suited. That is why Scandinavians in particular
prepare their lines and set them, under cover, from the main
deck, while the Japanese perform the same operations un-
sheltered astern on the upper deck. Although these craft
differ in the layout of their below-deck areas, their general
TABLE 1
Main particulars of three types of longliners built in France
Characteristics
Length overall ......
Length between perpendiculars
Breadth
Depth (to main deck)
LBDft'On')
Draught amidships on departure for fishing grounds
Displacement on departure for fishing grounds
Block coefficient
Prismatic coefficient
GM
Fish hold capacity ft8 (m8) ....
Fish hold capacity
Volume of fish hold /LBD ....
L/B
L/D
B/D
Method of conservation ....
Faroes
longtiner
ft
119.0
102.3
23.6
12.3
29,750
11.4
450 ton
0.577
0.696
3.51
7,720
143 ton
26.1 percent
4.3
8.3
1.9
ieing and salting
m
36.31
31.20
7.20
3.75
843
3.48
1.07
220
Tuna
longliner
ft
167.0
147.4
29.4
14.4
62,300
50.95
44.85
8.95
4.40
1 ,766
10.3 3.14
719 ton
0.557
0.673
2.49 0.76
16,800 480
3 10 ton
27.2 per cent
5
10
2.04
freezing
Tuna
hngliner
ft
98.5
82.0
21.3
10.2
17,800
8.4
259 ton
0.615
0.668
1.64
4,210
78 ton
23.8 per cent
3.85
10
2.1
icing
30.00
25.00
6.50
3.10
504
2.57
0.50
120
[591]
characteristics have various points in common. Three types
of longliner have been built in France, one for Scandinavian
methods and the other two for tuna longlining. The main
characteristics are given in table 1 .
Table 1 suggests that some of the results might be com-
pared and the corresponding curves plotted (fig 10). The most
important characteristics have therefore been shown, viz:
block coefficient Cb; ratio of fish hold volume/LBD; ratio
L/B; ratio L/D. From the aforementioned curves, taking into
account the results achieved with boats already built, the
following conclusions emerge.
WOO 10.000 19,000 FT*
Fig W. Curves of a few parameters of tuna longliners
Allowing for the operational conditions specified by the
owners or prospective owners, and the financial returns
demanded of the craft, it is possible, on the basis of the
anticipated tonnage offering the highest returns, to determine
with a fair degree of precision the principal characteristics of
the craft: block coefficient and the L/B ratio. The ratio
between volume of fish hold and LBD will then be given
automatically. It goes without saying that the values from
which these curves were plotted were obtained under optimum
conditions of transverse stability, trim and seakindliness. In
particular, the initial stability (GM) of all these craft on
leaving port for the fishing grounds lie within the range 1 .6
to 3.3 ft (0.5 to 1 m).
Designing the interior
The choice of design and its interior layout would be
governed by the methods of fishing and of preserving the
catch. One general remark is necessary, however, in con-
clusion, namely that the gross weight carried is in general
distinctly (15 to 20 per cent) greater than with other fishing
craft, in particular trawlers. This is due principally to the
fact that with craft not designed for trawling — the required
speeds and towing power not being very high— installed power
ratings are appreciably lower than for trawlers which,
furthermore, have a much greater amount of deck gear,
winches and various other apparatus, so that the space taken
up by the engine on longliners is correspondingly smaller
than on trawlers, thus rendering possible much larger fish
holds.
Forms are, of course, fuller than for trawlers, as the block
coefficient values makes clear. A further consequence is that
longliners are very economical from the standpoint of fuel
consumption and therefore, with equal power rating, of much
greater cruising range.
Finally, mention should be made of the pronounced trend
nowadays towards longliners with freezing equipment
installed, whatever their size. Until recently, only longliners
with a capacity of over 1 00 tpns were thus equipped ; nowadays
there are a number of craft below that size with one or more
freezing tunnels, but usually some more intensive refrigera-
tion method is used.
Below in table 2 are given the principal characteristics of
the refrigeration apparatus for longliners of 300 and 70 GT
respectively:
TABLE 2
Principal characteristics of refrigeration apparatus for 300 GT and
70 GT longliners
300 GT longliner 70 CT longliner
Volume offish holds ft8 (m») 16,900 (480) 3,875 (110)
Volume of freezing tunnels
fta(m8) . . . 5,280(150) —
Refrigeration apparatus
range .... 490,000 kcal/hr 1 5,000 kcal/hr
Liquid refrigerant . . Frcon 22 Freon 12
JAPANESE STERN TRAWLERS
Doust (UK): Shimizu's paper is an excellent summary of the
development of the larger deep sea trawlers and the factory-
type vessels in Japan. It reflects many of the problems which
have been and still are facing owners in other countries,
more remote from the prolific fishing grounds.
The block coefficient of Japanese trawlers quoted is rather
higher than other countries and there is the attendant loss in
speed. For vessels which freeze the whole or most of the catch
on board, excessive speed is detrimental to economic per-
formance and it would seem quite in order to accept such a
lower free-running speed, permitting economical savings in
fuel consumption, greater radius of action and a better ratio
of fish to fuel capacity.
At present, the economic justification of these large
vessels, especially in regions where the highly-qualified
technical staff required on board the vessels are being
competed for by shore-based industries, requires very careful
consideration and emphasize the need for more reliable
automatic machinery, deck- and fish-handling equipment.
Shimizu proposes the adoption of vessels specifically designed
for a specific fishing ground to minimize the equipment
required. This principle is now gaining favour in the design
of fishing vessels of size above about 1 30 ft (40 m) in length,
since the vessel and gear can be tailor-made for specific
adverse weather conditions, bottom conditions, depth of
water and range of operations. Many cases could be quoted
where the design of vessels has been spoiled by attempting to
cope in the design with too many fishing possibilities.
To overcome the tendency for the larger deep sea trawlers
to drift to leeward and lose course stability at low trawling
speeds, lateral thrust units fitted at the bow and stern have
been successfully employed. Experiments with such units in
the ship division of NPL have shown that special care must
be taken in sighting the lateral tunnel required. Fairing of the
mouths of the tunnel is required, particularly when the lines
of the vessel have rapid curvature in this region.
Studies made by WFA
Eddie (UK) : On the question of whether to have warping ends
on winches, one might note the very comprehensive study of
the operation of the winch of a large stern trawler carried out
by the Industrial Development Unit of the White Fish
Authority (UK). To avoid losing fishing time, high light-
hook speeds are needed for some parts of the operation of
handling the trawl; at other times, heavy pulls are needed;
therefore, if the job has to be done by having a lot of little
auxiliary winches scattered about the deck, and these are of
the common constant-torque hydraulic type, they have to be
[592]
of quite big horsepower. The idea is economic only if
sophisticated hydraulic systems with near constant-power
characteristics are adopted, otherwise the use of warping
ends on the winch is advised.
The UK has experience of large stern-fishing freezer
trawlers with engines aft, engines forward and split diesel-
electric. The present trend is towards a single engine forward
driving a controllable pitch propeller, second most popular is
diesel-electric.
If a controllable pitch propeller is used in this class of ship,
there is considerable fuel saving if it is possible to vary
propeller rpm. Further on the subject of propulsion
economics, careful selection of machinery on a basis of
measurements made in service conditions can make a great
difference to costs: one popular class of machinery (diesel-
electric was selected on the basis of theoretical estimates and
comprised 3 y. \ ,000 hp engines ; measurement at sea showed
that for fishing a maximum of 1,200 hp was required and this
class of vessel therefore, could not quite fish on one engine
two were usually run. As a result of these measurements, the
specification of subsequent vessels has been changed to
2 x l,400hp engines, with consequent savings.
Processing layout
On layout of freezer trawlers, it is very desirable to keep
the fish awaiting freezing in chilled sea water, because this
gives consistent high quality, as the Poles have shown by
experience. It is obviously necessary that the buffer siorage be
arranged on a first-in, first-out bans, and the whole thing
needs very careful thought on the part of the naval architect.
The processing plants in British freezer tra vlers can handle
about 30 ton/day. These ships are from 210 to 240ft ((4 to
73 m) overall; they make trips of 30 to 60 days. The total
number of crew is 26 to 27, which is a long way from the
100 to 1 10 mentioned in the papers. This is possible because
the fish is frozen in the whole, gutted form in vertical plate
freezers. The vertical plate freezers in use in British freezer
trawlers are suitable for fish about 4 ft (1.2 m) long and 4 in
(10 cm) thick. The type of freezer would be useful for fish up
to 5 ft (1.5 m) by 6 in (15 cm) thick.
Returning to the subject of optimizing the design, it may
be worth mentioning Saint Finbarr. This freezer trawler is
210ft (64m) overall with 1,400 hp and carries the same
amount of fish as vessels 240 ft (73 m) overall with 2,000 hp.
According to such information as is available, her capital
cost was 1 5 to 20 per cent less, her fuel costs are about 20 per
cent less. Owing to her lower speed, she loses about 4 or
5 per cent of fishing time in a year. She has shown herself to
be as effective for catching fish as the more powerful type, so
it would seem that she must be a more economic solution. In
any case, this example, like the other, shows that it is impor-
tant to have design on reliable measurement of what is
actually required and on subsequent selection of the solution
with least costs for a given amount of fish produced,
Cardoso (Portugal): Shimizu should be complimented on the
very interesting paper presented. Could he give an indication
of the block coefficients and maximum section coefficients at
maximum load and the general arrangement plans of the
vessels mentioned? This would considerably add to the value
of the paper and make it easier to understand the special
problems mentioned and the solutions found.
Load on the warps
Hatfleld (UK): Shimizu mentions a load indicator for the
trawl warps. An exchange of information here might be
useful. The White Fish Authority developed a trawl warp
load indicator for stern trawlers about 18 months ago.
Although used first for research, it proved so popular with
fishing skippers that it was fitted to three of the newest UK
stern trawlers in its development form. It has now been taken
over for commercial production by a firm of internationally-
known marine electronic engineers, and ordered for some
six or seven new vessels.
It is used not only for detecting snags but for setting engine
power while towing in a tideway and setting the winch brakes.
It works as follows: the stern pulley cannot be used for
reading the load since the included angle of the warp over this
pulley changes substantially. The warps have therefore been
passed over jockey pulleys on the mizzenmast. These pulleys
hang on strain-gauged tension loadcells and since the included
angle always remains the same, the load on the pulley is
always proportional to the load on the warp.
A pair of indicators marked in tons is placed on the
wheelhousc and the system is calibrated in situ. Each meter
also has an alarm contactor which the skipper can set at a
value slightly above the towing load by the turn of a knob.
Designs built on experience
Kristinsson (Canada)- It is evident from all the papers pre-
sented that considerable data exist on the design and operation
of fishing vessels and that data gathered both from experi-
mental and actual performances now available could form a
good base for the development of future designs. The best
vessels arc obtained by collective efforts from the naval
architect, the owner, the fishermen and the gear technologists.
A considerable amount of hydrodynamic data has been
established in the past by model experiments of models
tested in series and, as staled in the Traung, Doust, Hayes
paper, data gathered by FAO will be issued as soon as time
and funds permit. As such data is much needed by some of
the boat designers, funds should be made available in the
shortest possible time. In order to come up with the best boat
to fulfil specific fishing requirements, the following are the
major factors: hull form; fishing gear; machinery; fish
handling.
Not enough attention has been paid to the handling of
fish on board after it has been caught. This does not apply to
factory vessels but to fishing trawlers gutting the catch and
storing it in ice.
Convenient gutting lines and carriers should be designed
to enable the fishermen to work in a more convenient position
at waist level, instead of bending down and throwing the fish
several feet away into a washing box or in a fishhold. The
method of sorting and handling fish has not been improved
on for many years and most primitive methods are used in
most instances; then it takes much too long time to unload
the catch.
Container systems, pumping or carrying systems should be
given close study. Engine room automation should be closely
considered and all machinery should be started and operated
from the wheelhouse, having the engine room manless, with
the exception of one master mechanic, who could work the
normal 7j hours a day, for the purpose of maintenance and
not watch keeping.
The economic size of fishing vessels is an important factor
which is very much overlooked by many designers and
operators. An economic relation between hold cubic and size
of vessel should be closely studied. Some vessels of 148 ft
(45 m) length, having hold cubic of only 9,500 ft* (270 m3)
and in other cases 125 ft (38 m) length vessel having the same
hold cubic. This does not seem reasonable and is unecono-
mical, especially from the construction cost point of view.
Especially if one considers the fact that a vessel of 125ft
overall length with well-designed hull form can fish in
[593]
rougher weather than a vessel of 148 ft length, having poor
hull form.
r The design of fishing vessels is an interesting and challeng-
ing problem and as so many different factors are involved, a
good teamwork will always produce the best results.
SMALL CANADIAN STERN TRAWLERS
Gueroult (France): Reid has covered the entire field of small
trawlers and Gueroult congratulated him on his excellent
paper. It was interesting to see how the same problems as
one's own are solved in the antipodes.
Stern trawling methods came to Northern Europe from the
Mediterranean via the Pacific coast of North America, before
reaching Britain via the Norwegian whale factory ships. The
drum is a most important addition, though the limits of its use
remain to be seen. All the bobbins and floats are wound on
the drum together with the net. Accordingly, it offers an
acceptable solution for both large craft and small, where so
much deck space is rendered useless because the net has to be
laid out there. The proper place for the drum seems to be on
the centreline and not too close to the stern, so that there is
room for the crew to work between the drum and the aftrail.
The layout in Reid's fig 10 has probably not a great future
ahead of it. All asymmetric solutions disappear in time.
Fishermen in the US and Canada are fortunate in having
special winches for the various operations. The simplicity of
the drum and of its operation suggests that much would be
gained by installing a second one for a spare net in order to
avoid losing time on net repairs. With the appropriate
hauling gear, all handling of the net in the water or completely
on board, with the wings on one or both sides, hauling in the
codend over the stern or over the side are possible and
equally good. It is for the skipper to decide which method is
most practical for the state of the sea and the catch.
Once a simple solution is found for small boats, it will be
adopted for all tonnages. The conclusion to all this, then, is
that no amount of care in the matter of designing deck gear
for small boats is too much.
Gueroult agreed with Roberts re shelter. The skipper
should be able to see his crew at their tasks and cannot do
so if he is on the bridge. The latter should be designed in
such a way as to leave the crew under cover and yet in view
of the skipper.
Comparison with British conditions
Corlett (UK): Both the papers by Reid and Minnee are very
interesting and admirable. The Pacific Coast fishing vessels
certainly work in arduous conditions and it would be interest-
ing to have supplementary information on prevalent wave
heights and lengths in perhaps Reid's table 1. A special
feature of sea conditions around Britain is the considerable
wave height often associated with relatively short wave
lengths. For example, 10 ft (3 m) significant wave heights are
observed in Beaufort 8 in the south of the North Sea, very
often with the bulk of the waves in the region of 100 to 150 ft
(30 to 45 m). Often in confined waters due to shoals, vessels
cannot choose their course and so running and broaching
behaviour can be critical, especially on 50 to 75 ft (15 to 23 m)
boats.
The detailed description of trawl drums given in Reid's
paper is of interest and value and there is no doubt but that
this method will find increasing acceptance, especially on
smaller boats. If the drum is placed close to the stem,
occupying the bulk of the width of the stern on a small boat,
she will then be capable of trawling from the stern, but must
recover her catch from the side and is, of course, not a true
stem trawler. Some of the advantage of stern trawling is then
lost but, on the other hand, the simple mechanization of the
gear handling will probably compensate for this. At the same
time, possibly one of the most significant uses for the trawl
drum may be on side trawlers, especially perhaps in the 100 ft
(30 m) region, where there is an urgent need to reduce the man-
power used in the light of increasing competition from semi-
mechanized stern trawlers. A heavy bulwark roller with side
rollers to contain the net would appear to be about the only
modification needed to such ships in order to accommodate
a trawl drum although there might be some alteration needed
to the arrangement of fishroom hatches.
The side by side trawl drum/ramp arrangement does mean
that a small ship can trawl and recover over the stern, but the
efficiency of this arrangement is somewhat dubious in areas
where heavy catches are obtained. Fig 1 to 4 of Blount's and
Schaefers' paper show the relative congestion of this arrange-
ment and the codends shown are very small. If a large catch
is obtained, it is easy to see that there might be considerable
difficulty in handling the codend up the very small, narrow
ramp.
Care needed in comparing figures
The use of catching figures per head of crew in the way
Reid has done, while quite legitimate, can be misleading if
taken out of context due to the influence of varying grounds
and practices as to the processing and handling of fish. For
example, a particular gantry trawler of 90 ft (27 m) overall
length in North Europe caught 27,000 to 45,000 Ib (12 to
20 ton) per day and carries 15 men, but of these only three
are actually required for gear handling. All fish however is
gutted and dressed and practice in this latter respect has a
very considerable bearing on the crew carried. A more
indicative measure would be the catch per haul measured
against the number of men actually required to handle the
fishing gear itself and on this reckoning the ship quoted above
would, of course, compare very favourably indeed.
Reid's description of the basic methods of gear handling
are not all of ramp types or necessarily applicable to ramp
types. For example, the method of handling by lifting the
codend only was pioneered on the Universal Star and has been
incorporated in a considerable number of trawlers since, not
one of which has a true ramp. Reid refers to disadvantages
of this method of fishing and, with respect, Corlett disagreed
with him on certain points. For example:
• The net left in the water does not in practice foul up as
suggested, and this trouble is quite unknown
• The net does not float, but the codend does, and there
is no difficulty at all in bringing the codend forward
over the net and it will be found that there is no
tendency for the two to get entangled
• Fig 1 1 shows a deck arrangement of a small stern
trawler with this arrangement. It can be seen that the
whole arrangement is extremely convenient and the
gantry can be used for successively fleeting the net so
that a particular point can be reached systematically
and with the net in the flat. The mouth of the net and
both wings can be hauled straight on board in a
manner very similar to that of Reid's type B, and at
any time the fishing sequence for the latter type can
be adopted if net examination is needed. However, the
work, time and wear on the gear involved in having to
adopt this not too desirable fishing sequence is
avoided, except when it is necessary for examination
and repair. Corlett was not impressed with the idea of
dragging the fish bag over the bobbins on every haul
and he did not believe that this would attract many
fishermen
[594]
Fit? 11- Deck arrangement of a small gantry stern trawler
• Corlett's experience did not agree wilh Reid's
experience, that when fishing in rough weather there
is often trawl damage due to vessel heaving or sliding
over the floating net. Corlett did not know of such
behaviour
• The restriction to the lift in a well-designed trawler of
this type with a properly raised ramp gate is the
gantry lift and not the height of the gantry, although
of course this must be adequate. Double bagging is not
difficult as the codend is not really floating at this
stage; it is being partly lifted and is in fact easier to
get at than with a side trawler
• Good practice here is to use synchronized split
winches with auto-spooling and with these the quoted
difficulty does not arise. Alternatively, the arrange-
ment shown in fig 5 of Minnie's paper is sometimes
adopted. Finally, where the bag is dragged up a
stern ramp as opposed to lifted, the implication is a
ramp extending to below the waterlinc. On small ships
such as those working in extreme conditions this is
not ideal and additionally tends to waste a fair amount
of the deck space
Trends in Dutch fishing
Turning to Minnee's paper, Corlett was very interested in
some of the detailed features of the boats he had put forward
and considered that his arrangement of trawl winch and
deck house in fig 4 is particularly attractive. It is slightly
unfortunate in a vessel of this sophistication and capability
that a warp should be led forward to handle the anchor, and
an anchor winch with its own wire would seem to be well
justified. The arrangements of warps is good but is leaving
whipping drums open a desirable practice nowadays as the
use of these wires on slipping drums is probably the most
prolific source of accidents ?
Turning to the hull, the use of a fixed nozzle in association
with a large balanced rudder is interesting. It would seem
questionable whether this gives really good manoeuvrability,
that is to say, of the character associated with steering nozzles
or other optimum arrangements, particularly whether the
vessel is controllable astern.
One other important point is the question of propeller
noise and nozzles. Minnee stated that in the stern purse
seining proposal, the propeller noise will frighten the fish into
the net. This is possible. Looking at Minnee's fig 7(a) it can
be seen that the fish will tend to swim towards the centre of
the purse providing the ship can go around them fast enough
but it is questionable whether this is so and probably the need
will be to make as little noise as possible. In this respect a
nozzle whether fixed or steering is of great help as the bulk
of the noise from a propeller comes from the top vortices
and these are very largely suppressed by a shroud, especially
with the type of propeller which is clearly implied in Minnee's
drawing, namely square tips with very little tip clearance. A
nozzle purse seiner would probably cause very much less
disturbance to fish than a ship without a nozzle.
Minnee's fig 7 and his proposals for purse seining over the
stern are interesting. The main difficulty seems to be that of
brailing. Minnee's arrangement for brailing is not attractive.
Topping a loaded boom is a slow and expensive business
and will cause considerable wear on the gear. It is always
better if possible to slew at a fixed luffing radius.
Comment on details
Dickson (FAO): Commented on Minnee's fig 2 on stern
trawler/beam, trawler. The gallows are too far forward for
stern trawling:
(1) when towing and turning the warps would rub across
the rail at the stern
(2) If gear snags on the bottom at some stage, it is brought
directly below the boat when breaking it free. The
wires may be all spun together and waiting on the
shooting marks to come in view before slowing
the winch, the twisted wires can foul the bottom of the
boat. Quite a bit of speed is needed then to clear the
gear aft of the propeller when the gallows are so far
forward
Why cantilever gallows? These are convenient on small
boats, where the board is light and can be lifted in by hand.
However, ease of access to the board bears the consequence
that on a bigger boat with heavy doors and in a rough sea,
the operator has less protection. He is safer with the ordinary
inverted U-typc.
In Minnee's fig 3 it is proposed to run the ship astern or
winch it astern until it is over the snag. Jf there is a following
sea, with this shape of stern, this would be a very wet pro-
cedure. It is better practice to slacken the winch brakes, pay
out wire and steam the boat round to face the snag, then steam
towards it reeling in the slack.
Christensen (Sweden): Minnee's paper was most interesting.
To optimize a fishing vessel and make a better ship, one
always needs to consider the special kind of fishing water one
is fishing in. This often is the reason for new types of vessels,
but not always.
As a consulting engineer in Sweden, Christensen has the
experience that the stern trawler is not desired in those waters.
This argument is based on the fact that he had tried to intro-
duce the stern trawler without any luck — as this type of
vessel has not shown any better economy than the conven-
tional side trawler.
At present, a new model of this type has been tested, as
the demand for more speed and horsepower requires a more
careful design of the lines, combined with extensive model
tests to state all the propulsive dates. Concerning engine
[595]
arrangement, deck and navigation equipment, there is a really
great demand for automation.
Well arranged winch controls
Smettem (UK): The vessels illustrated in Minnee's paper
show a good deal of imaginative thinking and one is particu-
larly impressed by such details, as the simple arrangement of
winch controls in the wheelhouse in his fig 4 and the clear
working space afforded by raising the winch to the foc'sle
deck position. One does wonder, however, if the warping ends
are really necessary with a 4-drum winch, especially as a man
cannot stand behind, due to the close proximity of the wheel-
house. Could Minnee state the winch pull on mean drum for
the vessel shown in Minnee's fig 4.
The trawl handling methods shown in fig 1 are fairly
conventional for the small stern trawler and this method was
pioneered on the Universal Star, but in the case of that vessel
with the use of a hydraulically-operated stern gantry. Many
smaller stern trawlers are now fitted with this device and a
higher degree of automation can be achieved by its use.
The proposals for purse seining over the stern are very
interesting and this seems to be the logical method of handling
a purse seine. The difficulty with this method is to provide an
efficient method of brailing in the restricted space at the stern
and on the surface Minnee's proposals would not appear to
solve this problem.
If the brailing boom is topped only, as proposed, some sort
of guying arrangement will still be necessary to prevent the
boom swinging with the roll of the vessel. In addition the
fish can only be dropped on the after deck, which already
contains the stacked up purse net. In the event of the fish
being brailed on to a carrier vessel, hanging winches will be
necessary to swing the boom across for this operation.
Could Minnee elaborate on his proposals, as the problem
seems to be to provide a quick and efficient brailing system
which can transfer the fish to the working deck forward of
the stacked net or feed a carrier vessel alongside without the
use of a complicated guying arrangement.
The double rig trawl method
Juhl (USA): As noted by Knake, Murdock and Cating (1958),
first attempts to develop the double-rig trawling methods in
the Gulf of Mexico were made in 1955 by shrimp fishermen in
Texas. These intial efforts caused widespread industry interest
and many individuals contributed further development during
the past 10 years. The popularity and acceptance of double-rig
Fig 12. Paravane-type stabilizer used by some of the Gulf shrimp
vessels. Shown is a stainless steel model-- most are of galvanized
steel construction
Fig 13. Stabilizers suspended from the outriggers" extremities of a shrimp vessel fishing a single trawl in deep water
[596]
fishing led to the conversion of many conventional shrimp
trawlers and has influenced vessel deck and gear arrangement
to a degree where practically all new constructions are of the
double-rig type.
Although the double-rig method of shrimp trawling has
reached a fairly advanced stage of development, it is still
evolving. A recent innovation has been the introduction of
stabilizer planes which are suspended from the midpoint of
the outriggers during fishing operations and while at anchor
in the fishing grounds. The stabilizers help considerably to
dampen the roll of the vessel. One major shrimp boatyard
includes stabilizers as standard equipment in all new construc-
tions (fig 12).
Normally the stabilizers are suspended from blocks
mounted about two-thirds out on the outrigger booms.
Fig 13 shows the stabilizers suspended from the extremities of
the booms. This practice is employed in the deepwater
(200 fm or 370 m range) royal red shrimp fishery which cur-
rently utilizes a single trawl.
Another development of recent origin is the use of tag lines
on the trawl doors. The tag line, long enough to reach the
deck, is permanently tied to the upper part of the doors.
Recovery of the line is accomplished with a pole. Formerly,
a crew member had to catwalk out to the end of the outriggers
and tie a line to the door's chain for subsequent hauling aboard.
This practice was dangerous at all times, especially during
heavy seas.
Main trawl winches have increased in si/e and ruggedness
to allow for greater versatility for faster setting and hyulback
of gear and greater cable capacity for fishing in deeper waters.
Also, they provide for use of largci diameter cable which
reduces breakage, lasts longer and improves safety.
Table 3 shows information of the shrimp ves^ls over 5 GT
operating in the Gulf of Mexico during 1963 and 1964,
compiled from published and unpublished US statistical data.
Similar statistics on vessel characteristics are not readily
available prior to 1963.
TABLE 3
Average measurements and characteristics of shrimp trawlers
operating in the Gulf of Mexico during 1963 and 1964
J963
Lou No. in Size* Total No.
GT ft(m) of net of vessels
Double 53.6 43.5
rig 37.2 (16.5) 2.85 (13.4) 2051
Single
rig
17.4
45.3
(14.0)
2.12
57.0
(17.6)
646
1964
GT
Loa
ft (m)
No. in
crew
Size
of net
Total No.
///?t of vessels
Double
rig
39.3
55.2
(17.0)
2.71
44.5
(13.7)
197 2059
Single
rig
18.4
45.4
(14.0)
2.06
55.5
(17.1)
145 723
*Net size measurement is length of leadline,
thp data not available for 1963.
Reduced manpower
For the Gulf of Mexico fleet, data shown in table 3 are
fairly similar for the two years. However, the average number
of crew members per vessel for 1964 on the double-rigged
vessels has decreased by 0.14. This implies that five per cent of
this fleet of over 2,000 vessels employs one man less. Similarly,
</» 400
Number of Doubl* Rig Vottolt 2059
Number of SingU Rig V9i»«lt 723
Total 2782
Single-Rig gggl
Double-Rig PTTT^
000
loi
70-79 30-39 40-49 SO-S9 *0 *f 70-79 iO-lt 90-49
GROSS TONS
Hg 14. Number of shnmp fishiiiK vessels over 5 GT operating in the
Gulf of Mexico during W64< single ami double rigs
but to a lesser degree, the single-rig trawl data also shows
reduction in manpower. Increase of single-rig vessels in 1964
over 1963, as shown in table 3, may indicate conversion of
smaller double riggers to single rigs, or entry of vessels
engaged in other activities into the shrimp fishery.
Many of the new constructions, vessels in the 65 to 75 ft
(20 to 23 m) category, arc operating in international waters off
the north-east coast of South America. The migration to these
grounds is indicated in fig 14, which reflects this reduced
(A 300
35-39 40*4 45-49 SO-S4 55-39 4044 «S4t 70-74 75-79
FEET(LOA)
Fig J5. Length overall and number of shrimp vessels operating in the
Gulf of Mexico during 1964, total vessels are 2J82
number of vessels in the higher GT category. It also shows the
majority of the double-rigged vessels fall in the 30 to 49 GT
class. This tonnage class coincides with the 50 to 59 ft (15 to
18 m) length groups shown in fig 15. However, the GT-length
relationships are not well defined in the upper and lower
extremities of the graphs in fig 14 and 15.
[597]
Fig 16 shows the relative size of the nets (footrope measure-
ment) used by double and single-rig vessels. Footrope
measurement of the two nets used by the double riggers have
been combined. The lower graph indicates a decrease in size
of nets on double-rig vessels for 1964 in the 84 to 90 ft (25 to
27.5 m) range and a slight increase in the nets with ground-
ropes 99ft (30m) and over. The upper graph shows an
increased usage of 60 ft (18 m) and smaller nets on single-rig
vessels during 1964 as compared with the previous year.
SINGLE- RIG
IB 1963- 646 V«M«li
G23 1964- 723 V*ss*lt
£ 4,or FOOT ROPE LENGTH IN FEET
DOUBLE-RIG
O S5
310-
300 -
950-
300 -
JIO-
1963- 2051 V«ss«ls
1964- 2059 V.is*ls
»* 73 75 71 II 14 «7 tO V3 *• •* 103
FOOT ROPE LENGTH IN FEET(2n«t»)
Fig 16. Number of shrimp fishing vessels and their trawl net size*
operating in the Gulf of Mexico during 1963 and J9f>4, single and
double rigs are shown separately
VESSEL HORSE POWER
Fig 17. Predominance ofhp preference of shrimp vessels operating in
the Gulf of Mexico during J964
Composition of Belgian fleet
Hovart and Verhoest (Belgium): Table 4 shows that the near
and middlewater fleet represents the most important group
of the Belgian fleet; at the end of 1964, this fleet totalled 230
vessels. There has been a movement towards bigger vessels
with more powerful engines, and more powerful engines have
been installed in old ships. The number of coastal boats has
decreased. In the period 1955 to 1964, the number of coastal
boats has been reduced with 108 units.
Data on shrimp vessel main engine hp are available only for
1964 and not classified by rig type. Fig 17 clearly shows the
predominance of hp preference. A comparison of this graph
with those of fig 14 and 15 indicate poor correlation between
hp, vessel length and GT. The reason for this discrepancy may
stem from the popularity and preference of certain model
engines, available only in specific hp. This practice may account
for many vessels, over and under typical characteristics
(shown below) to be overpowered and others underpowered
(Juhl, 1961).
Data collected indicate certain vessel measurements and
characteristics which allow describing a typical Gulf of
Mexico double-rig shrimp vessel as follows :
GT . . 42 to 45
Loa . . 55 to 60 ft (17 to 18.5 m)
Main engine . 200 hp
Trawl net size . 90 ft (27.5 m) footrope (two nets combined)
The present trend, however, is towards larger vessels, in the
65 to 75 ft (20 to 23 m) class, of 60 to 80 GT and 275 to
300 hp main engines. Steel hull construction is rapidly
gaining acceptance, although wood is still preferred by the
majority of the boatyards.
TABLE 4
The Belgian fleet, end 1964
Ranges
Costal fleet
number ,
144
hp .
8,784
15—119
GT
2,474
5—57
Midwater fleet
number .
230
....._
hp .
45,119
120-349
GT
15,664
33—185
Deep-sea fleet
number .
44
hp .
28,105
350-2,330
GT
11,142
118—1,399
The new middlewater vessels are traditional side trawlers.
The introduction of the double-rig shrimp beam trawling for
the coastal fisheries must be mentioned. The main advantages
are:
• The horizontal opening of the two beam trawls is
greater as compared with one otter trawl for the same
resistance
[598]
• The length of warp has much less influence on the
performances of the beam trawl than on the otter
trawl
• The opening does not change during course alterations.
• The influence of tides is much less on a beam trawl than
on an otter trawl, as the opening is fixed whereas with
otter trawls the resistance and shear of the otter boards
is highly affected when fishing in tidal areas
• Shrimp trawling is usually carried out in muddy and
soft bottoms. This does not affect the opening of the
beam trawl, as the opening is constant and the foot rope
catanary adjusted to an appropriate and constant
("raking") light in the bosom. Such bottoms do affect
the shearing effect of the boards so that the opening of
the trawl varies, with the result that the footrope tends
to dig in soft bottoms when the boards close
• Double-rig operations allow easier adjustment of the
gear to the fishing conditions, as it is possible to conduct
comparative fishing at all times because two nets arc
constantly in operation at the same time
• The direction of wind and tide has no influence on the
shooting of the gear. As only the codend is hauled
aboard, the whole operation can be mechanized,
leading to faster operation with less crew
Increase of comfort
On the new side trawlers the comfort of fishermen was
much improved, but the simplification of the handling of the
gear and catch was still an open problem.
Two small stern trawlers have recently been built in Belgium,
namely the 0.700 and the Z.594. The 0.700 is classified in the
coastal fleet and the Z.594 in the midwater fleet.
Beam trawling is applied for shrimps and flatfish. The two
derricks (1 ) in fig 18 are set at an angle of approximately 0 to
30 degrees (and pointing a little more aft than abeam).
The vessel steams ahead on a straight course, while wearing
out both nets by means of the warps (3), coming from the
mean drums (2a) of the winch over the blocks (4), attached on
the deck gallows (5) to the top of the derricks. While operating
or afterwards, the derricks are lowered by the drums (2b) at an
almost horizontal position. After hauling, both nets are heaved
to the boomtips. The derricks are put to an angle of about
30 to 40 degrees and only the bag is then hauled on deck, the
codend emptied and the gear prepared for the next haul.
Pair-trawling is applied in wintertime for sprat and herring
fishing. The operational method is the same as on side trawlers,
except that the net is paid out over the stern.
With bottom-trawling, the warps (3) arc running from the
mean drums (2a) of the winch, over blocks (4) hanging on the
gallow (5) to the otter boards. The net is dropped into the
water over a stern reel (6) by the 0.700 or the stern ramp (6)
by the Z.594. Sufficient warp is paid out in relation to the
depth. By hauling, the otter boards are hung in the gallows, the
dandylincs are unshackled from the boards and fixed at a line
coming from the drums (2b). Using these drums, the net is
hauled over the reel or stern until it is on board, excepting the
codend. The codend is brought on board over the reel or stern
by means of a runner coming from the derrick (7).
With the possibility of the application of these three fishing
methods, it is expected that an increase of fishing operation
and a decrease of the uncertainty of supply will be possible.
On the other hand, better working conditions are provided
and a simplification of the manual work is realized by a
rationally-designed working deck and the possibility of
handling the winch directly from the bridge.
Fig 18. Recently built Belgian combination fishing boat, O.I 00
[599]
Fig 79. Recently built Belgian combination fishing hoat< Z.594
The first-built combination vessel, O.100, fig 18, has the
following characteristics:
Loa .
Lpp .
moulded breadth
depth .
draught aft .
55 ft (16.8 m)
46 ft (14.0 m)
16.5 ft (5.0m)
7.9 ft (2,4 m)
7.0 ft (2.1 m)
The fish hold has a capacity of 775 ft* (22 mn). The fuel-oil
capacity is 1,300 Imp gal (6,000 1) and freshwater capacity
130 Imp gal (600 1). The propulsion engine is a four-stroke
diesel, which develops 1 50 hp at 1 ,250 rpm. This engine allows
the boat to get a speed of 9 knots. The winch is a four drum
winch with friction clutches and is controlled from the wheel-
house. The vessel is further equipped with a hydraulic
steering gear, echo-sounder, radio and direction finder. The
crew consists of three men, a skipper and two mates.
The Z.594, fig 19, has the following characteristics:
Loa .
Lpp .
moulded breadth
depth .
draught aft .
69 ft (21. Om)
56.5 ft (17.25m)
19.7 ft (6.0m)
9.85 ft (3.0 m)
10.5 ft (3.21 m)
The fish-hold capacity is 2,100 ft3 (60 m3). The fuel capacity
amounts to 1,750 Imp gal (8,000 1) and freshwater tanks hold
875 Imp gal (4,000 1).
The vessel is powered by a diesel providing 220 hp at
1,500 rpm and can do 9 knots. A hydraulic steering gear is
fitted and a six-drum winch is controlled from the wheelhouse.
The wheelhouse equipment includes radio, direction finder,
echo-sounder and a radar set. The crew consists of four men,
namely a skipper, an engineer, a mate and a deckhand.
Safeguards for beam trawling
Of the two trawlers, special safety arrangements have been
taken for beam trawling. One disadvantage of beam trawling
is that the stability of the vessel can be greatly impaired when
one of the trawls becomes hung-up by a bottom obstruction.
The forces acting on the boomtop become so great that the
vessel may capsize. The forces arising from a hang-up of one
net may be taken to culminate at a point at the top of the beam
which is high above and far outside the centre of gravity and
tends to heel the vessel over. Therefore, a special security
release system had been introduced by Hovart and Verhoest.
This system:
• Allows the forces acting at the top of the boom to be
brought to a point lower down, even when there are
winch or other defects which prevent veering out of
the warps
[600]
7WQMN INTO THE SEA
A : POSITION OF BUOY THR** inn MU PICKED «*
CF ; P03rr«>ioFCu»«)w^PHw^Wo
o : POSITION of *6T THROWN INTO
SHOW me POSITION B
Positioning of gear during fishing operation of Japanese Danish seiner
[601]
• Transfers the forces to a point which allows the vessel
to manoeuvre the gear clear of the obstacle
• Allows the net to be hauled quickly and in a safe way
On the O.I 00, the warps coming from the winch are led
through a block attached to the stern gallows and run over a
derrick block to the gear. The derrick block is attached to the
boomtop by means of a sliphook.
When the gear meets an obstruction, the sliphook is released,
which in turn releases the boomblock, so that the towing
forces now act on the block attached to the stern, which
ensures full stability of the vessel. The free net is then hauled
over its own boom, after which the vessel is manoeuvred in the
usual manner to free the hung-up gear from this obstruction.
The gear is hauled hard on to the block in the stern where it is
stoppered. The boomblock is then hauled back to its position
at the boomtip and the gear is further hauled in the usual
manner.
At the beginning, on the Z.594, the warps were led from the
winch to a block attached to the double mast and they were
run directly to the boomderrick. This solution proved to have
many disadvantages when hauling the hung-up gear. Therefore
the same security system as on the O.100 was installed.
The O.IOO and Z.594 are the first two small stern trawlers in
Hasomi Drum
Rope
Warping Drum
Scale
12
16
2,4
30
36
Inf
1
i
1
1
i
1
lm[ ....
I
6
20C
)
400
600
600
1000
Particulars
Load
Winding
Spetd
Rope Type
Ton
Ft/Min
M/MIn
Hotomi Drum
25
1.5
295
394
90
120
Compound
1,09-1.2 5 In ( 28~32mm)Dlom.
8700 Ft (2650m) Lenath
Reel
3,5
Wire 0.b2In(!6mm)Diom.
£30 R (70nt) Length
Wo r ping Drum
Wire 0,62ln(l6mm)Diam,
Winch Drum
Fig 21. Layout of winch for Japanese Danish seiner
[602]
Belgium, and they are operating very well as compared with
the best vessels, so the construction of small stern trawlers is
being continued.
Japanese one-boat trawling
Okamoto (Japan): The operation of Japanese-type small
trawlers is similar to that of Danish seiners because the use of
trawl-doors is prohibited, near the Japanese coast. There are
approximately 1,100 boats of this type, from 15 to 100GT,
and the catch reaches 655,000 tons, equivalent to about
10 per cent of the total catch of Japan. Recently more than
50 steel boats of 50 to 100 GT have been built every year.
The catch by otter trawlers was 14,000 tons only in 1963.
Takagi (1955) described a Danish seiner to the First Fishing
Boat Congress. Since then many similar boats have been
built. Fig 20 shows the setting sequence of warp and seine,
At point A, the warp will be thrown into the sea, attaching a
buoy at one end of the warp and change the course of the
boat at point C. At point D, the codend is thrown into the sea,
after passing point F return to the point A. After picking up
the buoy, towing starts. Sometimes the net is set clockwise.
After the seine has reached the sea bottom, towing is made for
a while with slow speed and the net is hauled up by a taper-
type sheave between two discs of winch drums, as in fig 21.
As a comparison the movement of the trawl net and warp in
the sea is shown in fig 22.
Fig 23 shows the pulling up of the seine net and warp on
the stern of the boat. With ordinary side operation, the seine
net is pulled to the side of the boat, and the fish are scooped
from the gunwale. One cycle of operation takes about I i
hours. Otter trawling sweeps the sea bottom, but the Japanese
Danish seining is different, as clearly seen in fig 20 when fish
is surrounded by the rope on the sea bottom. It is not yet
completely studied whether or not fish are gathered by the
rope only. The following are important points:
• Ropes are not to flap up from the sea bottom so that as
much fish as possible can be gathered
• To drive fish into the net with good timing and control
of winding up speed of rope and thrust of propeller
adequately are essential. Such control depends on fish
species and the water depth
Up to 10 years ago, the winch and propeller were directly
driven by the same main engine and control was difficult, as
the rope speed and thrust of propeller could not be adjusted
independently. Such control could be done only by very
experienced fishermen and they kept the technique secret.
Advantages gained
The advantages of this fishing, in spite of the control
difficulty, are that fishing can be done on uneven or slanting
sea bottom and it is possible to operate in deep sea. Otter
trawler fishermen call the sea more than 165 fm (300m)
depth deep sea, and U>5 fm (300 in) operation is common for
this type of trawler. In fact operation is practical and very
effective in 275 fm (500m) depth and it seems possible to
explore further deeper sea bottom. Another point is that the
otter trawlers are so effective that many fishing grounds are
over-fished, but Danish seiners will not damage the fish-
ing grounds.
In the past 10 years, fishing procedure has been improved.
Firstly, by using hydraulic system winch, speed adjustment
became flexible. Secondly, by the adoption of controllable
pilch propellers, adjustment of thrust of propeller became
possible, combining these two arrangements to solve the most
difficult points of the operation. Now, an important problem
is how to improve fishing efficiency and save manual labour.
There are a few other matters; in the past, manila rope was
used for the warp but it lasted only two to three months.
Synthetic fibre has been tested, but did not stand the severe
operational conditions. Then compound rope was applied
2000-
1000
1000-
2000-
800-1
600
400-
200-
Ship Advanced Diltanct
1000 1500
1000 2000 3600 4000 5600
2500 3000 3500
7000
1000 2606' 3000' ' 4660' ' '5600 WOO 7000
Trowl Ntt Advanced Distance
$ta Sutfaet
8000
9000
loooo iidoo
12000 13600
14000
200
400
i Bottom SrS, Position Of Ship
8,-Sfc Position Of Ship IA Dragging Not
8,-S^ Position Of Ship In Haulm?
Z--Z,, Position Of Trawl Ntt
X(~X,A*»dX-Y7Curv«d Position Of Warp
Fig 22. Movement of trawl net and warps is different from that of the Danish seine shown in fig 20
[603]
• TO PULL U» NET
SETTLE OF NgT list QHPER TP Ng)(T CYCLE
# 23. Hauling sequence of Japanese Danish seine
synthetic fibre outside with wire inside as a padding. In 1960,
this arrangement was first tried and the improvement was
completed in 1962. Compound rope costs twice as much, but
lasts one year or more and is therefore economical. Another
problem with using compound rope is that it is almost
impossible to coil by manpower, and has to be wound by a
reel, which has contributed greatly in saving time. Compound
rope sinks quickly because of its larger specific gravity. This
large specific gravity has another benefit in that it facilitates
throwing the rope exactly to the point aimed at, which is
especially good for deep-sea operation. Another merit is that
20 per cent more area can be surrounded by compound rope
than manila rope. The use of wire rope was once considered,
but its specific gravity was too large and it dug into the sea
bottom.
Better hauling capacity
The improving of the hauling operation was undertaken
and working over the stern has been found most advantageous.
The difficulty of the Japanese-type Danish seining is
that the wing nets are so long that some device to pull them up
is needed. The first boat which tried stern operation was
Sankichi Mam No. 51 built in 1964. This boat 122 ft (37.2 m)
Lpp, 300 GT, electric propulsion, was built for operation on
the Bering Sea. Devices were originated on this boat to operate
independently either the right or left hand side drum of the
winch. This made seining possible, irrespective of the
direction of wind and tide, because the adjustment of tension
of warp at either right or left side drum was possible, and
controllable pitch propeller was also used. The adoption of a
bow thruster will add further improvement in the future.
[604]
,-..-_, ENGINE ROOM !j No 6 1 ! MO 9 4> 5
^ -j I! FISH HOLD ! FISH HOLD
35 ~2£o 45 5Of
DECK
x-- r
"*•••- L_
t^
L-.J; C
r . ^
{ j "^'
..
4 UlJ'Uo V J
L.
N. 1 1
'
^4 ' J*nsiu^
StfcERIMG
ENG n*
FNtMNt ROOM
*•**••
r i r' .
rY'01
[I.TL |
A!
JO
*^
ti iM5'ri
MBM «OOM|«-
U- i i t H
— t
N. iF
^^
*
-_--..: ^3
L ' J
r "1*1S).<.,M
L ^J,*"'*'M
*
ri^p
Fig 24. General arrangement of a Japanese Danish seiner
Because of the good results ofSankichi Maru No. 51 ', two other
same-type boats were completed and three additional boats
are under construction.
A somewhat smaller boat of the same type is shown in
fig 24, Sankichi Maru No. 51 has a long foc'sle type and
has a ramp at the stern. There are many opinions about
the advantages and disadvantages of installation of a stern
ramp for such a small boat. In the case of otter trawlers,
unigan type or system to pull up codend by derrick from the
side of stern are used. However, in the case of this type of
boat, the most effective way is the ramp system, which can
take up to 15 tons of catch at once, which often occurs in the
high season. Such an arrangement necessitates the increase
of freeboard at the stern, raised deck over the engine room
2 ft (0.6 m) higher than the upper deck and top of the ramp
3.3 ft (1 m) higher than the upper deck. A removable door
is installed near the top of the ramp. This door is remote-
controlled from a safe place on the deck by a hydraulic unit.
All these devices are designed for protection of the deck from
seawater and when waves still break over, the water will be
discharged through a gutter; the water from the middle of
the deck will be discharged from the scupper with sufficient
area at the centre part of the bulwark.
Engine room layout
The propulsion engines are twin engines with one shaft so
that they are used for main and auxiliary purposes. Another
advantage of such engines is that the size is small, According
to the general layout, it is possible to have steering room,
fishery winches, reels, etc, at one place on the engine room,
thus giving remarkably good convenience for the operation
and maintenance. As the engine room is ideally installed at
the stern, it is possible to make 3,450 ft3 (98 m3) of fish hold
at the centre of the boat. In the waters near Japan, fish
resources are rich, but market prices of fish are so low that
large hold capacity is absolutely needed. Concentrating
machinery in one place on board results in the saving of
labour, which is most important under the present circum-
[605]
stances in Japan.The bridge is so made that both forward and
aft of the bridge can be seen. The principal dimensions are as
follows :
Loa .
Lpp .
B
D
d
Main engine
Speed (trial max,)
GT .
Fish hold .
Fuel oil
Complement
Built .
100 ft (30.65m)
85 ft (25.90 m)
20 ft (6.10m)
8.2 ft (2.50 m)
7.3 ft (2.20 m)
510 hp
11. 5 knots
96
3,450 fty (98 my)
950 fty (28 my)
15
September 1965
Operating methods
Details of the fishing operation are shown in fig 20 and 23.
Fishing winches are installed at both sides of the stern. This
means that with this arrangement, the long wing nets can be
hauled up without being disturbed by the limited space on the
normal deck arrangement. Fish are caught with the codend and
hauled on to the upper deck at the bow side of the winches.
Therefore, before finishing fish handling on board, one is able
to prepare throwing or pulling up the net. Winches are
installed on the entrance casing for the engine room, thus
saving weight and space. Winches are driven by hydraulic
oil pumps with a pressure of 2,000 lb/in2 (140 kg/cm2) driven
by the main engine with a capacity of 2.5 tons/295 ft (90 m)/
min, or 1.5 tons/400 ft (120m)/min. Reels installed on both
sides of the stern automatically wind up ropes coming from
winches. The whole operation of the hydraulic winch is
controlled electrically from the bridge. However, for the sake
of safety, emergency stop can be made by the side of the
winches. Load and speed of the winches are indicated in the
bridge. It is expected that with this system the daily catch will
increase by 30 per cent.
The main engine consists of two sets of 260 hp, 1,200 rpm
diesels, a reduction gearbox and a controllable pitch propeller.
The output at the propeller shaft is 510 hp at 360 rpm. In
the front engines there are two generators each of 45 kW
with reduction gear. Two sets of hydraulic oil pumps are
similarly driven from the other side of the main engines.
These machineries are all remote controlled from the bridge,
namely: starting of engines, regulation of engine revolution,
on and off of the driving clutch of propeller shaft, regulation
of propeller pitch angles, various warning apparatus and
watching arrangement. The steering gear is of the rotary
cylinder type and is mechanically hydraulically operated and
the whole steering angle is 90 degrees. The operation handle of
the rudder is assembled with control panel of the engine.
Rudder and controllable pitch propeller are operated from
front and rear of the centre of the bridge, both starboard and
port side. Capacity of the fuel stands for about two weeks'
voyage.
Care of the catch
Until now most fishing boats of this size cooled fish with
crushed ice. Only a few boats are equipped with refrigerators.
Fish near the cooling coils get frozen, but fish inside are left
unfrozen in the case of bulk storing. It has therefore been
found that pre-cooling with brine of about 28°F (-2°C)
is the most effective and economical method. To facilitate the
cooling operation on deck, the brine cooler and two pumps
are installed at the port side of bow foc'sle. The refrigerator
is driven by a motor of 15 kW and is controlled from the
bridge.
Loading and unloading the boat is undertaken by belt
Fig 25. Belt conveyor arrangement of a Japanese Danish seiner
conveyors. No. 4 fish hold shown in the general arrangement
plan is the conveyor room for fish unloading, and the conveyor
arrangement at the port is shown in fig 25. Fish in a fish hold
are flowing out from the hatch near the floor to the conveyor
room and land automatically. This system is also available
to store fish in fish holds during the fishing operation.
Finding the exact location of a boat is very important, not
only for adequate voyage, but also for getting good economy
efficiency while fishing. Therefore radar, direction finder,
loran and a gyro compass are installed.
Steps in development
Birkhoff (Germany): When developing a new type of fishing
vessel, there is normally the tendency to find first of all simple
basic solutions and to advance step-by-step to more sophis-
ticated solutions for vessels with increased main dimensions.
Reid's paper shows, for example, purse-seiners, adapted to a
certain extent to the requirements of stern trawling. After one
decade of experience in the field of deep-sea trawling with large
units of very sophisticated layouts, an effort is now being made
to reverse this tendency.
In consideration of all advantages of the new successful
larger type of vessel, the next effort is to grant the same
advantages also to smaller types, which are used for midwater
and inshore fishing. The aims, which should mainly be reached
in this respect are:
(1) Gain in time for active fishing by decreasing the gear-
handling time
(2) Extended mechanization of gear-handling
(3) Ability to catch at worst weather conditions
(4) Increased protection for the crew
With regard to the limited financial resources of the owners
of these smaller vessels — sometimes in fact the skipper — the
additional cost for a stern trawler, compared with the existing
side trawlers, should be kept as low as possible. It should in
fact be considerably lower than the usual 15 per cent which
occurs with bigger stern trawlers.
Restricting to some extent the requirements of the above-
stated items 3 and 4, it is possible to eliminate the whole
[606]
MAIN DIMSN9IONB
29.97 m 9>.0*
« 55 m 28- o*
/n /9-t. 9'
581 m
3,
**TM tin. 4.04 /n
T7/^ 2(5. 700 // (30.65 /if) 5/m? trawler with ramp
shelterdeck, for instance, in case of no danger of icing up. extended foc'sle, running into a light centreline bridgedeck,
During the last year, several single-deck stern trawlers have as connection to the sternramp (see fig 26). This centreline
been built with only a partial tweendeck. connection deck gives a certain overhead protection to the
In consideration that the crew is accustomed to work on gutting area, which is at the same time protected to forward
the open deck and, as a matter of fact, generally prefer this if by the foc'sle. The latter one also contributes to the vessel's
the weather is not too bad, a step further was taken by seaworthiness,
introducing a new single-deck stern trawler type with an However, the demands of the above-mentioned items land 2
[607]
Fig 27. Final location of net hauling on 100ft (30.65 m) stern ramp trawler
Fig 28. One pull brings the codend to the right position on the deck of 100 ft (30.65 m) stern ramp trawler
are met by using four-fifths of the ship's length for a single
long pull of the gear on to the deck (see fig 27). Now, only
one pull is still necessary to bring the codend on deck and
deposit it in the right position for emptying it (see fig 28).
Due to this way of operation, it is now possible to empty the
codend into the ponds on maindeck within about 10 sec,
depending on the weight of the codend.
Such a type of ship, with the dimensions of a middlewater
trawler of 100 to 120 ft (30 to 36 m), opens up the possibility
of using the heaviest gear, such as the 140 ft (43 m) bottom
trawl with 18 or more heavy bobbins, like they are used on big
German stern trawlers.
[608]
Fig 29. SO ft (24.4 m) stern trawler with ramp
Loa 70 ft (24.1 2m)
Lw 72 ft 2 in (22m)
Lbp 65 ft 7i in (20m)
breadth 23 ft (7 m)
draught max with keel 12 ft 5$ in (3.8 m)
depth to main deck U ft 5J in (3.5 m)
[609J
Fig 30. 90ft (27 m) boat of steel construction
[610]
Same type for inshore and midwater vessels?
For the inshore and nearwatcr fisheries BirkhofT was trying
to develop the same type of vessel, but using lighter trawl gear.
Here, it seems to be advantageous to use the net-veer-drum
system in addition to the existing trawl winch, or — a new task
for the winch maker— a special trawl winch, eventually a
split-type, which can coil up the trawl warps, sweeplines and
net wings together. Furthermore, an opening at the forward
end of the codend is proposed, which allows an emptying of the
codend to forward, so that the length of the ramp can be
regarded as part of the utilizable deck area. Thus, the codend
is only hoisted onto the ramp and not the deck. A pivoted flap,
forming the upper end of the ramp, tilts the codend to for-
ward, spilling the fish into the culling and gutting checkers.
When doing this, the aft part of the codend must be held by a
rope which runs over the bipod post block. The forward-
emptying of the codend by means of this tilting operation
allows a very low block position which limits at the same time
the height of the aft bipod post and consequently results in a
light and cheap construction.
With an 80 ft (24 m) boat of composite construction and a
90 ft (27 m) boat of steel construction, lig 29 and 30 for
example, these proposals can be realized. Here, a quadripod
post is used, which has at the same time the function of a
double-gallows aft. The pivoted ramp which is raised up into
a vertical position during free running, forms a recess, which
is provided with freeing ports on port and starboard sides,
for the purpose of water drainage.
Comparing the small single-deck stern trawlers with ramps
leading to the upper deck only, with the type proposed here.
Scale
Feet 0
20
Fig 31. Central arrangement oj '79 ft (24.12 m) midwaler trawler
[611]
the advantages regarding seaworthiness, gain in time, etc.
when hoisting the trawl gear over a ramp up to the foc'sle
deck level, are quite evident.
In consideration of future developments, it should not be
forgotten that such a type of vessel offers many possibilities
with regard to further mechanization and eventually
automation.
Conditions in Argentina
Santarelli (Argentina): Argentina has a high consumption of
red meat and it has become important to maintain, and even
increase, the country's meat exports, which are one of the main
sources of foreign exchange.
Fish is to be found in great quantity and variety off the
long coastline of Argentina. In 1959 there were about 300
inshore fishing craft and about 20 trawlers, most of them of
antiquated design. It became necessary to modernize the
fishing fleet. A number of craft were built, most of them of
steel. Although the country had experience in building wooden
boats, it had practically none in the field of steel construction.
Nevertheless, even this was fortunate in that rule-of-thumb
practices (with craft built to no plans and with no preliminary
studies) could be avoided and there could now be a technical
approach to the problem, with the principles of naval architec-
ture and boatbuilding practice as a basis.
In this connection, special mention should be made of the
papers read at FAO congresses which have been of the
utmost usefulness.
One point should first be noted, however, namely that
catches have risen by something like 100 per cent over the
last six years, and that an annual rise of 20 per cent is expected
in the future.
At the present time, 40 distant water and middlcwater
craft arc under construction. Since Santarelli had been
personally responsible for the design of some of these, he
referred briefly to their principal characteristics.
Fig 31 shows a middlewater type used chiefly for merluza
trawling. Several of these were built between 1960 and 1964.
Principal characteristics:
Loa ....
Lpp ....
Moulded breadth
Depth of hold
Mean draft .
Displacement
Volume of refrigerated hold
Volume of fuel tanks .
Fresh water tanks
Cruising speed
79 ft (24. 12m)
71 ft (21. 70m)
20 ft (6.06 m)
11. 5 ft (3.50m)
9.85 ft (3.00 m)
165 tons
3,360 ft3 (95 m3)
600 ft3 (17m3)
9 tons
9.5 knots
The hull is of steel; working deck of wood. The construction
is of the transverse type, with welded joints. It has the Bureau
Veritas certificate.
Type of lines
The lines are of U-type section and have a prismatic
coefficient in the region of 0.60. The craft has a raking stem
and a cruiser stern. Metacentric height minimum 1.4ft
(0.43 m). It has an excellent working platform and is easy to
manoeuvre. Average speed during trials and in operation
10 to 10.2 knots; power 300 to 350 hp, depending on the
engine installed. It is fast revving (1,200 to 1,300 rpm),
four-stroke, single-acting and compressed air starting.
Reverse/reduction gear with 4 : 1 ratio; the propeller is of
the fixed-blade type. Water cooling, with heat exchanger.
The engine has a power take-off, with clutch transmission
for driving the pump or the winch, depending on whether the
hauling gear is hydraulic or mechanical. There is a 15-hp
generator set. There are also pumps for bailing, fish cleaning,
fresh and sea water for use on board, and a standby com-
pressor. Also in the engine room is located the freezing
equipment (coolant: Freon 22) of 1 2,000 kcal/hr rating and
an 8-hp electric motor.
The fishing winch has a low pressure 400 lb/in2 (28 kg/cm2)
hydraulic drive, otherwise it is mechanical. Capacity: 400 fm
(730 m) of | in (19 mm) dia. cable on each drum.
There is a boom capable of taking up to three tons, which
is used for hauling the net. There is also a smaller (1-ton)
boom for lifting the codend; when this is hauled in very full
it has to be supported half and half by two booms.
Anchors are worked from hand winches or a train of
rollers from the fishing winch. Steering is manual, the rudder
being operated via chains and pulleys. Radio direction finder
(fixed loop), echosounder and radio telephone. The wheel-
house also contains the controls for the propulsion engine.
Good crew quarters
The crew consists of 10 men. Effort has been made to
ensure that the men have comfortable quarters, even within
craft of these reduced dimensions. The craft have met with
favour among fishermen. They work the year round, with
45 to 50 trips a year, depending on the distance of the fishing
grounds.
The fishing craft shown in fig 32 is the largest built in
Argentina to date, it was completed in 1964.
Principal characteristics:
Loa 115 ft (35.17m)
Lpp 101 ft (30.90m)
Moulded breadth . . . 24 ft (7.35 m)
Depth of hold .... 13 ft (4.00m)
Mean draft . . . . 11 f t (3.40 m)
Displacement 380 tons
Volume of refrigerated hold 6,700 ft9 (190 m3)
Volume of fuel tanks . 2,800 ft" (80 ma)
Freshwater tanks .... 18 tons
Cruising speed J 1 .5 knots
This craft is used chiefly for fishing merluza, but it has also
achieved excellent catches of bacaloa on trips totalling about
25 days.
The hull has transverse sections and is welded throughout.
It has Bureau Veritas certificate.
The lines are of the double chine type with an ample
deadwood at the stern to ensure adequate stability when
under way. It has a raking stem and a cruiser stern. Meta-
centric height (minimum) 1 .58 ft (0.48 m).
Tests have been made with a model of this boat. The
velocity obtained (subsequently corroborated by experience
with the actual craft) were 1 1 .5 knots at 540 hp.
Main and auxiliary power
The propulsion engine, 4-stroke, single acting, has a 540 hp
rating at 500 rpm. Starting is by compressed air. The engine
is water-cooled, and has a heat exchanger.
The transmission has a 2:1 reverse/reduction gear. The
propeller has four blades (fixed). At the forward end of the
engine there is a power take-off, clutch-operated, for driving
the hydraulic pump, which absorbs 80 hp.
Two auxiliary diesels, of 50 hp at 1,000 rpm each, have been
installed to drive two dynamos (30 kw, 220 volts DC). One
of these motors drives the bailing pump and a compressor,
while the other drives a 240-volt battery charger for emergency
lighting. There is a bilge pump for the engine room, others for
fish cleaning, fresh and sea water, etc. A refrigerating unit of
15, 000 kcal/hr rating (coolant: ammonia) driven by a lOhp
motor, maintains a temperature of 32° F (0° C) in the fish
hold.
There is a low-pressure hydraulic fishing winch, with two
[612]
Fig 32. Layout of US ft (35.17 m) Argentinian trawler
drums, each with a capacity of 900 fm (1,650m) of Jin
(19 mm) dia. cable and fitted with an automatic guide. Within
the hauling train itself there is a hydraulic winch for the
anchors.
There is a mast with a crosstree to which is attached a
pulley lifting up to 5 tons at a time and which supports a
3-ton boom. Over the wheelhouse a 1-ton auxiliary boom has
been installed for handling the codend.
The rudder is manually and hydraulically operated.
Navigational equipment includes radar and a radio direction
finder (fixed loop). There is an echosounder and fish detector
and a main and auxiliary radio telephone. In the wheelhouse
there are also the controls for the main engine, and manoeuvres
can be directed from the bridge or from the engine room.
The crew consists of 16 men, who have good quarters, the
galley and mess being particularly spacious and comfortable.
The skipper's quarters consists of a sitting room, cabin and
private bath. All baths on board have hot and cold water.
The craft has worked without interruption ever since
delivery to the owners and has brought in excellent returns.
The crew are very satisfied with its sea behaviour and with
the modern conveniences with which it is equipped.
In late 1964, realizing the increased demand for fish and
also the fact that the merluza was shifting habitat, being
found ever farther away from the ports, the fishermen were
anxious to have a craft affording greater range, although
without being too expensive.
Type of vessel evolved
The appropriate technical and cost/benefit studies were
undertaken, and from these there emerged a type of boat
described below. Five boats on this design are currently under
construction.
Loa ....
Lpp ....
Moulded breadth
Depth hold
Mean draft
Displacement .
Volume of refrigerated hold
Volume of fuel tanks
Fresh water tanks
Design speed .
90 ft (27.45 m)
78 ft (23.80 m)
2 1.3 ft (6.50m)
1 2.5 ft (3.80m)
10.6 ft (3.25m)
. 265 tons
(135m:j)
(38.5 ma)
9 tons
11 knots
4,770 ft
1,360ft
The hull follows the general lines of the craft just described,
except that under the hold there is a double bottom contain-
ing four fuel tanks. It has a bulbous bow and a transom
stern. Model tests were conducted in the tank of the Facultad
dc Ingenieria (Engineering School) of Buenos Aires, and
results confirmed the estimated speed obtainable with a
400 hp engine rating. The minimum metacentric height has
been calculated as 1.7 ft (0.52 m).
The propulsion engine will be of Argentine manufacture
[613]
and will have reduction gearing in the transmission, which
also has a controllable-pitch propeller. There will be a main
electrical generator and one auxiliary generator coupled to
the propulsion engine (1 10 volts AC, 50 cycles).
The fishing winch (hydraulic or mechanical) will be able
to take 700 fm (1,300 m) of i in (9 mm) dia. cable.
The crew will consist of 14 men, who will be accommodated
in four cabins. The skipper's cabin has a private bathroom.
The rudder will be hydraulically-controlled and servo-
assisted or controlled. Radar, radio direction finder, echo-
sounder, radio telephone, etc., will be installed on the bridge.
In Fishing Boats of the World:2, page 684, Santarelli has
described boats used in inshore fishing in Argentina.
Due to the rising demand for raw material for fish meal
and for fish for human consumption, research was begun on
a boat able to fish anchoveta (anchovy), caballa (mackerel)
and other pelagic species, with ring nets, and merluza with
trawls.
Stern trawler designed
From these studies a stern trawler gradually took shape
and although it was not easy at first to overcome resistance
from the fishermen to this innovation, they were won over in
the end, so that there are now under construction three craft
of the following type and four others of a very similar design.
Principal characteristics:
Loa ....
Lpp ....
Moulded breadth
Depth of hold .
Mean draft
Displacement .
Volume of refrigerated hold
Volume of fuel tanks
Fresh water tanks
Design speed .
. 64ft (19.45m)
. 55ft (16.86m)
. 18.3ft (5.60m)
. 9.35ft (2.85m)
. 8.25ft (2.52m)
. 120 tons
2,500 ft3 (70 m3)
335ft3 (9.5m3)
. 2.5 tons
. 10 knots
The hull is of steel and the deck of wood. The engine room
is forward. Under the hold there is a double bottom con-
taining four fuel tanks.
The lines are of the double chine type with a transom stern,
which also has a ramp. The minimum metacenlric height has
been calculated at 1.57ft (0.48m). Model tests were con*
ducted in the tank at the Facultad de Ingenicria of Buenos
Aires, and results confirm that the design speed is obtainable
with a 200 hp engine rating, reduction gear and controllable-
pitch propeller. The auxiliary equipment described for the
other craft will be installed and also refrigeration plant.
The fishing winch will be hydraulic and have a capacity of
350 fm (640m) of Jin (19mm) diameter cable. The rudder
will be hydraulically operated.
The craft will have electronic navigation and fish-finding
equipment. The crew will consist of eight men, who will have
the necessary shipboard comforts, despite the fact that the
craft is intended for short trips only.
A combination craft
Recently Santarelli had been asked to design a fishing craft
for both trawling and 'atun' (tuna) catching. In Argentina
'atun' is fished for the most part by Japanese methods. It is
first caught, then headed and, where desired, cut up on deck
and then frozen. Construction has already begun to this
design. Principal characteristics:
Moulded breadth
Depth of hold .
Mean draft
Displacement .
Volume of fuel tanks
Freshwater tanks
Estimated speed
Designed power rating
. 24ft (7.35m)
.12ft (3.70m)
. 10.6ft (3.25m)
. 350 tons
3,000 fta (85 m3)
. 16 tons
. 11. 5 knots
. 550 hp
Loa
Lpp
108ft (32.92m)
96.5 ft (29.40 m)
The hull is derived from that of the craft shown in fig 32.
It will have a quick-freezing room with a capacity of 5 tons
every 24 hours, down to 40° F (-40° C), and a refrigerated
storage room at -4° F (-20° C).
It will have the Izui-type line hauler, an hydraulic winch
for the trawl itself, an hydraulic powered block on the fore-
mast, and windlass and capstans likewise hydraulically
operated. The steering gear is hydraulically operated and
servo-controlled. The craft will have radar, radio direction
finder, radio telephone, cchosounder, log and apparatus for
measuring the temperature of the sea water, etc.
The craft described in this contribution are being built with
help from the Argentina Government, which supplies credit
up to 70 per cent of the construction costs, at low interest and
with a fairly long repayment period. The Government also
gives a subsidy covering approximately 20 per cent of the
construction costs.
Improved scallop craft
Pross (USA): Recent design changes in the type and size of
fishing vessels in the US New England scallop fleet have
materialized as a result of severe competition from other
countries.
The first scallopers were 30ft (9.14m) "cat" sailboats
which used 3 to 4 ft (.91 to 1.22 m) drags. In the 1920's and
1930's, power draggers employing 5ft (1.5m) drags in the
65ft (19.8m) range came into being. From then on there
was a continuing progression in the size and modernization
of the scallopers. In the late 1930's and early 1940's, shucking
boxes were added. By 1958, there were 70 to 80 boats in the
New England scallop fleet, mainly centred about New
Bedford, Mass. It was about this time that the Canadian
scallop fleet expanded from about one or two boats to 90
with an average length of about 90 ft (27 m). In the last five
years, the New England fleet has dropped to 30 boats. One of
the reasons for this decline was that smaller vessels (about
73 ft or 22.3 m) could not stay out as long, therefore smaller
catches resulted; also they were unable to operate in rough
winter weather on the Georges Banks and therefore became
non-competitive. This competition has resulted in the design
and construction of steel stern seal loper /trawlers averaging
95 to 100 ft (29 to 30.5 m).
One such scalloper is currently being constructed under the
US Fishing Fleet Improvement Act of 1964. The vessel is a
single screw, steel, diesel-powered stern scalloper with raked
stem, transom stern and multi-chine hull designed for stern
scalloping and bottom and midwater stern trawling in the
West North Atlantic fishing grounds. The inboard profile is
shown in fig 33. The fish hold is located about amidships,
the engine room forward of the fish hold and the crew's
quarters forward of the engine room. The superstructure
space forward contains the galley and messroom, crew's
head, shower, staterooms and upper engine room. Living
quarters for the crew include a ten-man foc'sle and one
two-man room. A single stateroom for the captain and a
double stateroom for the engineers are located in the super-
structure. The pilot house and chart room are above the
superstructure forward. The foc'sle, engine room, fish hold
[614]
Pig .?.?. I (tO. 5 ft (32 m) Loa steel stern scalloper
and lazarette are below the continuous main deck. The
principal characteristics are:
Loa ....
Lwl
Lpp ....
Breadth
Depth to main deck
Draft, designed midships .
Scantling draft
Displacement, ready for sea
Total power, continuous .
Speed, trial .
Radius of action
Complement — officers
— crew
Fuel oil .
Fresh water .
Lub. oil ...
Fish hold
Refrigerated stores
Weight of catch, at 40 lb/ft3
Works from both sides
The vessel is rigged for scalloping over both sides of the
stern. The scallop rake booms are mounted on the main deck.
The rake booms are used in lowering outboard and hauling
inboard the 16 ft (4.88 m) scallop rakes. The gallows consist
of hinged steel weldments mounted on the main deck which
may be swung outboard over the rail for towing.
The trawl warp (1 in or 2.54 cm) diameter plow steel wire
is lead from the winch to sheaves on deck, to the trawl block
on the gallows to the rake. The trawl winch is a four-drum
diesel-driven model, each 27 in (.686 m) drum with a capacity
of 450 fm (825 m). The drums are independently clutched to
100.5 ft (30.63m)
93.25 ft (28.42 m)
84.0ft (25.6m)
24.37ft (7.43m)
13.5ft (4.11m)
10.0ft (3.05m)
12.0ft (3.66m)
320 tons (325 ton)
765 hp
1 1 .5 knots
3,000 nautical miles
3
12
11, 600 gal (9.800
Imp gal, 43.9 mn)
3,000 gal (2,500
Imp gal, 11.35m3)
250 gal (2 10 Imp
gal, .95 m3)
4,200ft3(120nv})
100 ft* (2.83m3)
1 68,000 Ib (76 ton)
a low-speed shaft by means of air-actuated clutches On each
end of the winch, cargo winch drums are provided f from
which the single part rake hoist is run. A 150 hp diesel drives
the trawl winch through a fluid coupling, clutch reduction
gear, chain drive and shafting arrangement. Four unloading
booms with single part tackle lead to two single drum
hydraulic fish hoists mounted on the mast legs. They are
arranged to take out fish from the forward and after hatch.
After the rakes are towed for a pre-determined period, they
are lifted up onto the deck and turned upside down. The
catch is sorted on the deck. The scallops arc taken from the
pile on deck, placed in baskets and carried forward to the
shucking houses. The stones are debris are shovelled over-
board through the rock doors built into the bulwarks. The
scallops are dumped into the shucking boxes where they arc
opened, the meat removed and then placed in the wash box.
The empty shells arc dropped in the space outboard of the
shucking box, where they fall overboard through the shell
doors. The meats are washed in clean sea water, packed in
clean linen bags and stored in the fish hold in ice.
Many benefits listed
The arrangement and design of the new scallopers, with
the mast, booms, gallows, etc., located aft and the trawl
winch, shucking houses, etc., located forward, provide num-
erous advantages :
• Exposed working deck is more sheltered by extended
superstructure forward, providing more protection for
the deck crew handling the rakes and catch
• The pitching motion of the vessel is much less violent
on the aft deck of a vessel, which provides a more
steady working platform
• The above two advantages allow for fishing in more
violent weather than is possible in the old con-
ventional scalloper
• The increase in length of the deck working area will
allow larger dredges to be towed, therefore providing
a more efficient operation
[615]
• The shucking houses are not open to the weather
forward as in the conventional scalloper. This pro-
vides the men doing the shucking much greater
protection from the wind and sea. This area is also
less subject to flooding from seas breaking aboard
• The steel boats can take a greater beating than the
previous wooden boats
• The increase in length, depth and breadth have given
an increase in freeboard, greater stability and provides
for better handling in rough weather
• All machinery, living spaces and operational spaces
are located forward. This allows the crew to move
about from mess, galley, machinery spaces, wheel
house and sleeping quarters without having to cross
the open main deck, a wet and potentially dangerous
area in bad weather. The galley and mess are no
longer in the foc'sle
• An oilskin locker, open to the deck and to the
quarters, allows the crew to enter from the deck in
wet, dirty oilskins and boots, remove them for drying
and enter in clean, dry clothes, without tracking sand
and water through the quarters
• The wheel house arrangement allows the captain on
the bridge to operate the ship from the auxiliary
control station in the aft end of the pilot house, per-
mitting full visibility of the fishing operation. The
centreline located wheel house and all-round windows
provide 360 degree visibility from any location in the
pilot house. Day cabin is provided for the captain in
the pilot house
• Ample space is provided for the later installation of
new and improved gear, such as conveyors, automatic
shucking machines, etc
A new fleet of US steel stern scallopers is slowly emerging
on the scene. Competition has forced the way with the result
that a new design and arrangement for this type of vessel has
been developed. Operational experience will show if the new
scalloper can hold its own in this competitive field.
Author's reply
Minnee (Netherlands): Dickson put up a very practical
question about the trawl warps rubbing the aft rail.
Adequately decreasing the width of the rail aft and sufficient
height of the blocks will prevent this. Cantilever gallows are
necessary on this particular boat, leaving the bulwarks free
for stowage of the beamrakes, but there is no problem of
course in fitting a removable guard to prevent the door from
swaying when hoisted over the rail. Besides this, normal
V-frame gallows have the warps rubbing the aft leg of the V,
when turning the boat. Going stern up in a heavy following
sea should be avoided with a sterntrawler stern this should
be restricted: "when weather permits".
Corlett wondered about the manoeuvrability of fixed
nozzles with normal rudders associated — it can be proved
that there is no decrease at all. This system is used for differ-
ent reasons: extra thrust by little and constant tap clearance,
less vibration and maintenance of rudderbearings, constant
thrust during pitching (no racing), excellent propeller protec-
tion and less propeller noise (mine sweepers are equipped
with nozzles to protect themselves from acoustic mines).
Smettem asked whether warping ends are necessary with a
4-drum winch as now generally used. They are still very
handy and until the winchmakers provide friction-clutched
auxiliary drums of very light construction, most rope-
handling can be done faster by means of warping-ends. Those
imperfect 4-drum winches on multi -purpose vessels are still
fitted for handling topping lifts of booms or top warps on
4-seam-trawls and for purse-seining.
For safety reasons, the man handling the warping ends will
stand aside, so that there is no real need for space behind the
end. On the Mexican vessels, the total pull on the mean
drum's diameter amounts to about 4 tons. The sterntrawl
method shown is conventional compared with sidetrawling
today, where there is a minimum of mechanical installations,
but all advantages of sterntrawling are achieved in tactics and
deck-layouts.
No sterngate, nor hydraulically operated gantry can
improve this, which is the reason why they are not used. How-
ever, there were a few problems to be solved, mainly in the
guiding and holding of the swaying bag on a rolling and
pitching vessel, referred in the paper as to guider frames and
bag arrester.
Reply to ramp advocacy
Birkoff is a strong promoter of ramps, but in Minnee's
opinion most of his arguments for general application of
ramps can be refuted by considering:
• The average catch per haul generally is small, say
4 tons (daily catch 25 tons) which can be shipped in
two bags of standard construction netting. The real
catches vary considerably on most grounds, which
means, that more than 50 per cent are smaller and a
few per cent are really high, causing extraordinary
heavy strain on the gear and lifting equipment. The
splitting method permits the use of light standard gear
and moderate-sized equipment for handling each size
of catch without risks of spoiling
• The space gained by omitting a ramp enables one to
locate the wheel house further aft and give a simpler
sternstructure with maximum safety and shelter for
the crew without all kinds of mechanically driven
flaps and doors. These neutralize in the cost of vessel
and equipment, the so-called gain in operation time.
When these arc measured in split-minutes they sound
good, when sitting in the office, but every fisherman
knows, the heartbreaking efforts necessary to keep the
gear going and the time involved in repairs. In theory
the time benefits gained by a ramptrawler compared
with the splitting system in good average fishing
amounts to 15 minutes per day, which has no influence
on timetables in which mending consumes, sometimes
several hours, besides the risks of losing codends and
fish and the shooting, which takes even more time
with a ramp. There must be a very good reason for
the particular choice of a ramp, in general, Minnee
doubted it
Shimizu responds to queries
Shimizu (Japan): He was grateful to many people for their
attention and study of his paper. Doust requested him to cite
examples pertaining to unsuccessful combination trawler
designs, but Shimizu would frankly mention that, apart from
unsuccessful examples, they are continuing strenuous efforts in
the following respects.
(a) A large deepsea trawler (factory trawler)
So long as it may be expected that large amounts of
initial investment are required, it involves some risk
to design trawlers specially fixed to a certain fishing
ground. Therefore, for instance, in addition to
operating in the North Pacific waters — the main
fishing ground — the possibility of operating in
African waters is also required. In this connection,
there is no conclusive choice of kinds and lines of
Baader system and proportional ratio between
refrigerating holds and meal hatches, with the
[616]
result that some lines of Baader are useless; or there
appear hatches full of meal, and on the other hand,
the refrigerating holds are quite empty and vice versa
(b) Small sized trawler
It will be methodical to decide power of trawl winch
and main engine after laying down the scale of trawl
net beforehand. But in fishing anyhow, the net is apt
to be larger. Consequently, it causes such a simple
trouble as being unable to wind up, with the result
that too great a quantity of fish is caught in a large
net
(c) Lpp of trawler and waves
Tenyo Mam No. 3— a reconstructed stern trawler
operated the fishery in the North Atlantic waters.
This trawler was of 4,000 GT, 304 ft (99.8 m) Lpp.
Satisfactory operations were unexpected in this water,
due to the danger of the hull's intensity by panting
in harmony with the waves. On the other hand, a
stern trawler of 300 GT which followed Tenyo Maru
No. 3 at that time, had no fear of it. The Tenyo Marti
No. 3 is at present operating in North Pacific waters.
The above seems to suggest that there is necessity
to design beforehand such a scale and type of vessel
as will be in harmony with those wave lengths which
may arise in the waters to be encountered
In reply to Cardoso, Shimi/u said: block coefficients
midship coefficients arc given in table 5.
and
TABLE 5
Block coefficients and midship coefficients of various vessels
Names of vessels CV Cm
Talyo Maru No. 6 1 , . . 0.649 0.947
(The same as Taivo Maru No. .5/j
Taivo Maru No. 65 . . 0.67K 0.945
Taiyo Maru No. 75 , , 0.654 0.954
Talyo Muru No. #/ . 0.651 0.963
Fukuyo Maru No. I . . 0.680 0.942
Chuvo Maru No. 7 . . 0.679 0.947
Zulyo Maru . . . . 0.663 0.960
To Hatfield's comments Shimizu added that Taiyo Maru
No. 82, built in 1964, is equipped with oil pressure tension
meter just before top roller of gallows, that is, link mechanism
system with top roller. In consequence, with no effect from
warp angle, warp tension can be read in the control room
filled wilh an alarm.
Taiyo Maru No. 83, buill in 1965, is fixed with deck roller
between top roller and trawl winch, and strain gauge with an
alarm is also equipped with utilizing it. In addition, automatic
"off" mechanism of main engine clutch according to trawl
winch torque is also adopted.
Handling the purse-seine net
Bardarson (Iceland): It is stated in Minnee's paper that when
using the Icelandic system of purse-seining, it is needed to
keep the vessel free of the net by a power skiff, bowthrusler,
active-rudder or other means. This is not exactly done in all
cases. Only one Icelandic fishing vessel has until now been
fitted with a bowthruster and active-rudder, and although
most of the Icelandic purse-seiners do have a power skiff
for emergency cases, it is only very seldom used.
It seems that it would be more difficult to use the method
for purse-seining over the stern in bad weather and sea
conditions, than the Icelandic method. The movement of the
vessel is greater at the stern than amidships and when the
vessel is pitching, the seine net after closing could be at a
rather small distance from the propeller (see situation (r) and
(d) in fig 7 of Minncc's paper). Therefore the statement that
rudder and propeller will counterbalance the pursing force
of the winch might not be so advantageous compared with
the Icelandic purse-seining on the starboard side. The state-
ment that the fish are frightened into the net by the propeller
sounds as a kind of wishful thinking. It is Bardarson s
experience that it is wise to make the least possible noise with
the propeller before the purse-seine has been closed at bottom.
Minnee seems to consider stage (b) of fig 7 to be when the
noise from the propeller would be useful to frighten the
herring into the net. Here the net has not yet been closed at
the bottom and excessive noise could very easily result in thai
most of the herring would escape under the net.
Regarding the statement that no hydraulic boom swingers
are necessary, merely topping, this might be right, but the
derrick would need some side guidance at its lowest point,
during topping and at its highest point. These guiding wires
or ropes would have to be varied in length during this opera-
tion. Therefore some equipment would be needed for that
purpose which is not explained in ihc paper. It is stated thai
the rampless stern trawler has ample deck space to store two
complete Icelandic seines -one deep and another shallow.
Then there will not be much deck area left for herring on
deck, and as ihis is only a 125 GT vessel, it is doubtful if it
would be advisable to carry constantly two nets on deck, each
weighing 7 to 8 tons.
It is staled lhat when brailing with stern to the wind, the
whole system (ship and net) is in an equilibrium position.
This might be so in calm weather and no sea, but if the vessel
is pitching in heavy seas, Ihere could occasionally be some
disorder in the situation, and then the short distance from ihe
propeller under the ramp and the net hanging into the sea
abaft, it might cause trouble. The vessel concerned was
completed in December 1963. It would be of interest to know
if this vessel has been purse-seining with this method, and if
so, what the experience has been.
Basic strain in drying up
Allen (USA): The basic problem in purse-seining is slrain on
ihe net during the last phases of drying up large catches before
and during brailing. They have vessels of 54, 66, 73, 82 and
83 ft (16.5, 20, 22.3, 25 and 25.3 m) in length. The quicker-
motion of large vessels has resulted in substantially greater
net damage and lost catches. Since the vertical accelerations
of the stern are much greater than when lying beam to the
sea, this proposed system may result in a serious problem.
A power skiff or bowthruster is necessary. However, the
South African pilchard, Peruvian anchovy, US menhaden
and Icelandic herring fisheries are all working without skiffs.
Some of the fleet in Chile uses skiffs for towing, the major
requirement for the skiff is to support the cork line during
brailing. In certain fisheries, this would be essential for stern
seining. Possibly several substantial booms not shown in the
drawings could be used. Operating identical vessels in trawling
and seining in South Africa, they had evolved a system of
fishing similar to that used in Canada.
Reid (Canada): Complimented Minnee on an excellent paper.
His proposed system of purse-seining seems to offer a simple
and very inexpensive method of changing over. However, a
seine skiff is probably necessary to make a fast set
particularly for tuna or herring — and Allan is right about the
need for extra cork line buoyancy, and in addition to skiffs,
it is quite common to use other fishing vessels to support the
cork line.
A Canadian development is a somewhat larger storage
[617
drum for purse-seining— the drum set being some 8 ft (2.4 m)
diameter x 8 ft (2.4 m) long barrel— which will hold a
380 x 40 fm (700 x 73 m) seine and is used on quite small
vessels of 45 to 55 ft (13.7 to 16.8 m) fishing with only five
men, so efficient that the USA has outlawed the method.
Dual use of stern trawlers?
Birkhoff (Germany): An efficient stern trawler with ramp can
also be used for purse-seining and the ramp will facilitate
shooting and hauling the seine. Minnee's proposal of purse-
seining can with advantage be used also on a stern trawler
with ramp, the heavy purse rings could be wound up to the
ramp's wavetrap or over the lateral stern bulwark. The bipod
post could be provided with a powered block, which would
deposit the voluminous seine on to the geardeck, where it
would be ready for the next shooting operation.
There are some other interesting advantages in using a
ramp trawler for purse-seining. For instance, such a vessel
can use its own propulsion as compensating force against the
pull of the powered block, and also for aligning the purse-
seine when the fish in the wings try to press forward around
the ship. When it is not advisable to pump out the purse, i.e.
in case of bigger fish or different fish sizes, the time-consuming
brailing operation can be avoided by using a kind of codend,
recessed into the buntends of the purse-seine, which can be
hoisted up the ramp like a chain one after the other (see fig 34).
There should not be any problem in chasing the fish into
these codend-shaped recesses. The fish, trying to escape from
the purse, will certainly completely fill the recesses.
Pumping out the purse will take about one hour for 100
tons of fish. Now, in the proposed case, several of the men-
tioned bag recesses are arranged around the purse taking up,
equally filled, say 10 tons of fish each. When trawl fishing, it
takes about 20 seconds to hoist such a codend on to deck and
to empty it into the checkers. Thus, supposing the seine gear
of the discussed vessel is well adapted to the new way of
operation, it should be possible to hoist such a buntend bag
within 20 seconds as well. That means that the hoisting of
100 tons offish of a purse-seine, which is filled in the proposed
special way, would take less than four minutes. Of course, the
installations have to be well adapted to this quick boarding
of the fish. A conveyor belt should help the continuously-
working washing drum to transport the fish to the fishhold
hatches.
Considering the seasonal employment of purse-seining and
stern trawling, the somewhat higher expenses for a combina-
tion vessel should be compensated by the advantage of
having a very seaworthy ship with highly mechanized standard
of gear handling, which results in a considerable gain in
active catching time, and consequently in a better catch result
and profit for the ship.
The development of such a vessel, being not only a matter
of the naval architect, presents at the same time a problem to
be solved by the gear specialists and trawl manufacturers.
Thus, suppose there is a good co-operation among these
people concerned, it is likely that such a vessel will be
developed in the not-too-far-distant-future.
Minnee replies on seining problem
Minnee (Netherlands): Bardarson mentioned that power
skiffs on Icelandic boats are not necessary to assist the
operation, which is true and therefore it is already a big
advantage over the Pacific method. But the Icelandic boats
have very little similarity with stern vessels, which was the aim.
Referring to the remark on net stowage and space for brailing,
Minnee's idea was to drop the fish just behind the sternrail
on a chute or tunnel leading forward. The net can be stacked
right over this tunnel so that no storage space is lost. To
brail-out the sacked-up net takes only 10 to 15 ft (3 to 4.5 m)
of length of net in the water, which can be enlarged by using
a spreader boom. Corlett and Smettem also asked for more
details about the brailing operation with a topping boom.
Minnee admitted that the sketches in the paper are rather
simplified and do not show the guider frame usually fitted in,
which the gilson and other wires arc led in a strictly longitud-
inal direction, no matter the rolling of the vessel. This avoids
guys of variable length, boomswingers, etc., while the topping
is by auxiliary winch-drums.
Transferring the catch to a carrier-vessel however should
be done in the usual way.
Fig 34. Purse bagging by a recessed bunt-end
F6181
The aforementioned guiderframe may also support the
corkline, another reason for omitting the skiff,
Allan mentioned this and the problem of the accelerations
at the stern. Here the same precautions have to be taken as
side seiners turn their stern into the swell; slernseiners there-
fore should probably turn off the swell. This proposal is really
not more complicated.
The escape of fish during the pursing period has been the
subject of different precautions. Tuna boats throw "cherry
bombs" to frighten the fish back into the purse. Icelandic
fishermen have tried to hang a "barrier" from the starboard
side of the vessel, why could not propeller wake do something
worthwhile in this respect ?
COMBINATION FISHING VESSELS
Glehen (France): Fig 35 shows a type of boat which has
spelled high returns for the seafolk of Brittany. This is a
wooden combination boat, working shellfish (crayfish,
lobster, and crab), but which can also engage in tuna long-
lining and trawling. The boat has a very high initial stability
because its centre of gravity is very low by reason of the water
contained in the fish well; GM^4.5 ft (1.39 m). The water in
question does not have a free surface effect as is evident from
the plan.
•>up^^^p^
faun
Fig 35. Arrangement to decrease surface effect
The craft also has great stability of form because it has flat
longitudinal sections, a high freeboard and a very high
prismatic coefficient (0.68) and a large beam (rolling period
4.5 sec). In the well, the shellfish can be kept alive for several
months without the water having to be renewed mechanically.
Intensive shellfish gathering oft* the French coast has
depleted the area; but this has only meant that the fishermen
have built bigger boats and have repeated the process outside
the territorial waters off Cornwall, Ireland, Morocco and
Portugal and in the Mediterranean. As if that were not enough,
they have built bigger boats still — up to 115ft (35m) in
length, though still in wood — and they have gone as far afield
as the Arguin banks off Mauritania and even to the coasts of
Brazil and Honduras, where crayfish are very abundant and
scarcely exploited, but they have been chased away. The
waters off Angola, Brazil, Honduras, Madagascar, Mauritania,
Senegal and elsewhere represent a veritable gold-mine. Small
boats will be adequate because shellfish are taken very near
the coast.
Wells are of delicate construction. As many as 400 stoppers
may be needed for fish wells to ensure complete watertightncss.
Certain precautions have to be taken with the shellfish in the
well. They must be prevented from killing and devouring each
other.
Marketing poses no problems. All the wealthier countries
are ready buyers, since shellfish are a great delicacy. Air
freight is minimal when set beside the selling price. Paris
takes deliveries of live lobsters from Canada and live crayfish
from South Africa. One importer has installed at Orly
Airport a fish tank capable of keeping up to ll,0001b
(5,000 kg) of live shellfish for several months at a time. The
example could be followed in all parts far from the sea.
Active building in USA
Whittemore (USA): Blount and Schaefers make reference to
the construction of combination vessels in the US Pacific-
Coast. In recent months, there has been stepped up activity in
the construction of fishing vessels in this area. A number of
vessels are being built in the 70 to 100 ft (21 to 30 m) overall
length size, primarily for the king crab fishing with pots and
carrying the crab live in circulating sea water in the fish holds.
Some of the vessels are for single purpose king crab fishing,
some are for combination king crab and trawling, and others
arc being considered for combination king crab fishing and
chilled seawater salmon packing. In the latter case the vessel
would operate in the king crab fishing in the winter time when
it is most profitable and in the carrying of salmon in chilled
seawater from catcher boat to cannery during the salmon runs
in the summertime.
The use of bar keels to effect roll dampening, as suggested,
has been considered necessary on small vessels, especially
where draft is no limitation, not only to effect roll damping,
but to provide directional stability of high displacement to
length vessels as well. However, the keel should not be simply
a single vertical plate. Rather, it should have a fiat bar set
horizontally, running the full length of the vessel's keel. This
provides added strength, additional roll dampening, and
prevents damage to wooden keel blocks when the vessel is dry
docked. Sometimes the centreline keel is fabricated as a
box keel rather than as a single plate keel where it is desired
to take advantage of the steel surfaces to provide keel cooling
for the main engine or auxiliary engines and avoid the
corrosion and maintenance problems of heat exchangers.
In the case of shallow draft vessels where there is no room
for a keel below the plating on centreline, it is suggested that
side skcgs approximately a quarter beam of the vessel from
the centreline be used in order to provide roll damping and
directional stability for the vessel. The centreline keel is of
more value than bilge keels. This is especially true on fishing
vessels which handle gear over the side. In such cases, the
bilge keels can cause damage to the fishing gear and the bilge
keels themselves arc subject to damage.
Year round fishing activity
Hovart (Belgium): The general aim of the construction of
combination vessels is to obtain maximum utilization of the
vessel throughout the year, Generally speaking, the fishing
season of the Belgian coastal and near midwater fleet is as
follows :
• From March to October is the season of beam trawling
for shrimps
• From October to March is the season of the sprat
fishing and the spent herring fishing
• Throughout the year some ships use, however, bottom
trawling
The fishing operations are very irregular, and as a recon-
struction of the coastal and near midwater fleet was planned,
the question was raised if it could be of economic interest to
apply on the same vessel different fishing methods. With the
combination vessels it will be possible to do so — to increase
the fishing intensity and diminish the uncertainty of supply.
Interesting category of craft
Gueroult (France): Multipurpose or combination boats, i.e.
those engaging in more than one type of fishing, make up an
[619]
interesting category of craft and one correspondingly difficult
to discuss. It is only natural, with the failures of the past, that
the general view should be somewhat pessimistic, and people's
caution is justified. The failures have been due largely to
attempts to make the side trawler capable of performing two
jobs at once —which is simply accumulating incompatibilities.
The fact remains, however, that Scandinavian vessels have
nearly always used both trawling and Danish seining methods.
Nothing could be simpler than those boats with their dual-
purpose deck gear.
With an afterdeck free of obstructions and with a reasonable
programme from the owner regarding the use of the craft,
there is no difficulty in combining bottom and surface fishing.
Longlining can always be added, though not, of course,
Japanese tuna longlining methods, which call for considerable
deck gear and a large crew.
A combination boat is conceived before all else for fishing
different species at different times of the year, and for countries
where fish resources are not overabundant. In either case it is a
question of economic necessity. Boats that can be used for both
stern trawling and tuna seining are also giving satisfactory
results. If the emphasis is to be placed on one type of fishing
rather than the other where deck gear is concerned, bottom
fishing would have a slight priority over surface fishing. At all
events, the combination boat will always be, technically,
something of a mongrel.
Technical and economic problems
Hildebrandt (Netherlands): The naval architect and the
economist have different ways of thinking. The naval architect
is especially interested in studies of one or more separate
parts of the vessel and its auxiliaries and has to build what the
fisherman wishes. The economist is rearly only interested in
the whole of the boat and especially maximizing the profit of
it. The vessel is not his aim, but the profit. Now, in the Nether-
lands, studies of costs and earnings have taught that it is in
general impossible to reach maximum profits with combination
boats. Therefore, specialize! The combination boat is many
times a vessel of yesterday based on irrational feelings : it is run
with the hare and hunt with the hounds. The specialized boat
is an optimal ship based on rational calculations: the vessel of
tomorrow.
De Wit (Netherlands): The problem of combination boats
cannot be solved in the simple way Hildebrandt points out.
Though he does not state clearly which fishing methods were
combined, he probably has in mind Netherlands fishing
vessels combining herring drift-netting and herring trawling.
The requirements for these fishing methods differ so much
regarding the number of crew and engine output that Hilde-
brandt's statement might be true for a compromise between
these two specific fishing methods.
Nevertheless, there are many successful combination boats
in the Netherlands. The small trawlers of about 80 ft (24 m)
length were originally built for bottom trawling for bottom
fish. Now they are generally beam trawling with double-rig
for bottom fish and can very easily switch over to pair-
fishing for pelagic fish. The engine output, the crew and the
fish-hold capacity suit these different fishing methods very
well.
Therefore a combination fishing vessel can be an economic
proposition if the requirements for the fishing methods to be
exercised cover each other for a big part. On the other hand
a contradiction between these requirements is no sound base
for a good overall economy in most cases.
Main problem is the catch
Minnee (Netherlands): It is generally true that combination
boats are not very good in many respects. Naval architects
should never cease their efforts to improve these boats because
combination vessels in many cases are the only way to make
fishing economical. The Norwegians, for example, have great
peaks in their fishing seasons and to make the best of it, they
have to use different kinds of fishing gear at different times of
the year. Reid's paper encourages continuing with combination
vessel design.
The aim should be to obtain optimal solutions both ways,
not to result in a sterntrawler with an unsatisfactory layout for
purse-seining or a purse-seiner with a poor arrangement for
sterntrawling. The main problem often does not lie in the
fishing, but in the preservation of the catch, different species in
different seasons.
To carry on with combination vessel design, it is meaningful
enough to try this system in order to obtain optimal solutions
both ways, not to result in a stern trawler with an unsatisfactory
layout for purse-seining and a purse-seiner with a poor
arrangement for stern trawling.
The main problem does not lie in the fishing, but in the
preservation of the catch. Transferring the catch to a carrier
vessel alongside cannot be done at the stern, of course, and
most likely should be done in the usual way.
Specialized proposals
Toullec (France): Small craft engaging in stern trawling and
seining should have a clear working space aft. The most
commonly used layout, accordingly, has the propulsion
engine and crew's quarters forward. In Toullec's proposals,
fig 36 has the engine installed aft, yet leaves a sufficient area of
clear deck available. The accommodation space is well out of
the way and, also, there is a sheltered place for handling the
fish. The proposed design exploits these possibilities to the full
by keeping a large space aft of the engine room unobstructed.
This results in a greater improvement in the crew's comfort
and more working space, greater safety and efficiency-
characteristics which go together.
In this way the main winch can be driven by the propulsion
engine. The winch itself is placed slightly to port, giving more
unbroken working deck. A variant of this principle consists
in having a winch with two separate drums, controlled from
the bridge, and standing in more central relationship to the
shelter deck. The wheel house is placed centrally, thus affording
a view of all fishing operations, as advocated by Roberts.
Accordingly, the general layout, when all is said and done,
is of very low cost. The boat described, being intended for the
smaller fisherman, is kept within the lattcr's financial means
by the specification of simple gear, not by reducing hull
dimensions. For the same reason there is no call for large fish
holds, the latter to be considered appropriate for smaller craft
subsequently enlarged to benefit from advantages other than
that of a larger fish-hold capacity.
Coming now to seakindliness, this design is based on
similar trawlers working the difficult waters of North Western
Europe in winter. The experience there gained makes it
possible to build in a minimum reserve of stability to counter
the heeling couple due to wind and fishing gear (care must be
taken not to exceed this couple, which has a different value
for each size of boat, if the desired seagoing qualities are to be
assured. Here = 16tonm, (under the French regulations of
8th February 1962). A good multipurpose boat is only
possible above a certain size.
Safety considerations call increasingly for high freeboard
aft and yet, at the same time, a well-immersed afterbody
and a smooth form in order to mitigate the effects of buffeting
when the craft pitches. Rudder and propeller should not be
too far aft in order to avoid fouling the trawl ; practice shows
that placing them a small distance forward suffices. Balanced
afterbody, depth and sheer are all bound up with one another
[620]
Main deck
Lower dtek
Fig 36. French combination trawler seiner with the following dimensions:
Loa 78. 7 ft (24 ni)
Lbp 68.8 ft (2 1m)
B 21. 3 ft (6.5m)
dma, 10.2 ft (3.35 m)
Volume fish-hold 2,470 cu ft (70 m)
Volume fuel-tanks 920 cu ft (26 m)
[621]
and govern satisfactory design. Contrary to what was the
case with certain early stern trawler prototypes it is with a
good depth of hull that the best compromise can be obtained.
Deck layout and the possibility of installing two fish holds
means that the craft can engage in more than one type of
fishing, though, clearly, it can never be perfectly adapted to
all types. Working plans for each mass production series
should allow for the various types of operation anticipated,
e.g.:
trawling, seining, short trips (no special fish holds)
tuna, lining and seining (fish holds — live wells)
longlining, trawling for bait, shrimping, etc.
Where the craft is used only as a trawler, the shelter deck
could be prolonged aft and the part between decks closed
off with a metal door, thus providing a fish processing room.
Small craft must work in all seasons
Barthoux (France): Small-scale fishing is before all else
seasonal, and the boats and gear employed are of all shapes,
sizes, tonnage and power rating. If it is, first of all, to survive,
and in the second place, to develop, the small-scale fishing
sector must keep abreast of the economic situation and
technical progress and take advantage of all the improvements
introduced in the last few years. Most of all, fishing must no
longer be seasonal and should be converted to standard
bottom trawling, though without abandoning during the high
season, fishing for migratory species (tuna, sardine, sprat,
etc.). Accordingly, for small-scale fishing, what is needed is a
combination boat, i.e. a trawler/seiner which can engage,
without undue difficulty, in other types of fishing (fishing
with live bait, dragnetting and longlining).
It is with these considerations in mind that the Ministry
of the Merchant Marine, wishing to enhance the productivity
of small-scale fishing, has sought, as part of a plan for a
rehabilitation of the country's fishing economy, a design for a
combination boat suitable for mass production in the
country's shipyards. The characteristics of these boats have
been arrived at after taking into account the wide differences
in the financial means of fishermen, in port installations, and
in the customs prevailing at different parts of the coast.
A preliminary study showed that France's small-scale
fishing sector needed boats of much the same type, but having
different dimensions and engine ratings, with hull lengths
ranging between 52 to 100 ft (16 to 30 m). In 1962, accordingly,
the Ministry announced a contest, inviting the country's
shipyards specializing in small fishing craft to submit studies
for such a boat, and also designs for trawler/seiners of one
or other of the following classes:
length overall 52 to 92 ft (16 to 28 m) (wooden or
steel hull)
length overall 72 to 79 ft (22 to 24 m) (wooden or
steel hull)
length overall 85 to 92 ft (26 to 28 m) (steel hull)
All these were to be prototypes of stern trawlers so that no
modifications would be required for their use whether as
trawlers or seiners. The shipyards were informed that the
designs would be awarded prizes in accordance with their
technical worth, and also that they would be made available
to fishermen desirous of having one or other of these types
built. The contest benefited the small-scale fishing sector
doubly in that boats could now be standardized—with the
advantages of mass production and the correspondingly
lower unit price — and, secondly, the experts would not have
to pay for the studies thus made available.
Collected designs helped progress
Designs and related documents submitted by the various
shipyards taking part in the contest have been condensed in
a handbook brought out by the Central Sea Fisheries Com-
mittee, representing fishing boat owners. The publication has
had wide circulation and has proved a valuable source of
information in the development of small-scale fishing in
France. Ever since, the trend has been towards the con-
struction of trawler/seiners having steel or wooden hulls and
stern fishing arrangements. Nevertheless, many matters remain
to be finalized before it is possible to decide on the best system
of stem fishing on small trawlers.
Fishing boat owners, convinced of the need for a combina-
tion boat and of the efficiency of stern fishing methods, for
enhanced safety and workability in that the crew are sheltered
from the elements, are joining forces with the shipbuilders in
research on the best type of gear to introduce. Stern hauling
on small trawlers will probably always mean shipping the
net in successive lifts using tackle fixed to the rear mast,
leaving the remaining lengths of the trawl in the water, since
there is no room to instal a hauling ramp. Nevertheless, better
hauling gear will certainly be devised. Equipping small
trawlers for seine fishing is likewise progressing. The use of the
powered block is gaining ever wider popularity, though seine
and trawl winches are being combined in order to save space
and weight. The most widely used system is the two-drum
trawl winch, together with a capstan with one vertical and
two horizontal warping heads, the entire mechanism being
belt-driven, via a clutch, by the propulsion engine. With this
system, the handling of the purseline and hardening up of the
seine still remain manual (over the warping heads).
With purse-seiners, experience has shown that when fishing
for tuna, it is sometimes necessary to complete setting and
hauling operations within something like ten minutes.
French manufacturers have therefore developed a three-drum
winch (two for the purselines and one for the warp), powered,
via a clutch, from a central hydraulic drive and thus of very
flexible control. On these criteria, a combination winch is
being developed that will have three drums, two of them
being used for both trawling and seining, the third exclusively
for completing seining manoeuvres.
The Ministry of the Merchant Marine is currently having
constructed a 105 ft (32 m) research vessel, equipped as both
trawler (stern type, without hauling ramp) and as seiner. In
addition, there is a one-drum winch, likewise hydraulically
operated, for hauling the tow wing of the seine. A hydraulic-
ally powered block is also specified.
The experience gained with this vessel may offer guidance
in deciding the type of gear to be used on combination boats,
a question which remains crucial for small boats, since their
dimensions render them less adaptable to new techniques.
SPECIALIZED BOATS
Winter (USA): Bottom fishing for grouper and red snapper
forms an important segment of the commercial fishing in-
dustry in Florida, USA. The fishing is done by independent
operators who sell their catch to shore-based processing
plants, and no state agency compiles figures on the value of
the catch. To do so would be almost impossible, as vessel
operators are extremely close-mouthed and may also not
engage in the fishery on a continuous basis. A conservative
estimate, however, would place the number of vessels engaged
in this fishery at from 300 to 400.
The principal type of vessel used is schooner rigged with
a length of approximately 65 ft (20 m). These vessels are
usually equipped with an auxiliary engine and are used for
the long voyages to the snapper fishing grounds off Campeche,
622]
Fig 37. A reel in common use
Mexico. Many other types of vessels are engaged in the fishery,
however, and it would be truthful to say that almost anything
that will float can be found in the fleet. These vessels are
usually converted from other uses and cannot be considered
exceptionally seaworthy. On the contrary, they are often very
old and require constant repairs if to icmain in service. As a
consequence, they are used only for voyages to fishing grounds
50 to 75 miles off the coast, and the slightest heavy weather
means an immediate return to port.
The fishing method used consists solely of hook and line,
due to the rocky fishing grounds, which precludes the use of
any type trawl or net. The lines used are solid or braided
stainless steel with hooks rigged any of three different ways.
Fig 37 is a photograph of a reel commonly used on the boats
engaged in the fishery. These are usually constructed on the
spot, using whatever materials are locally available. They
vary slightly in design but are basically the same — a reel
capable of holding up to 300 ft (90 m) or more of wire line,
a spring (generally made from an old automobile spring),
and a small block over which the line is payed out and reeled
in. Up to ten of these reels may be installed on a single vessel.
Some experimentation has been carried out with electric
reels, but these have generally proved to be unsatisfactory,
due to the corrosion problem. Some operators prefer to use
reels and rods ordinarily used for sport fishing when they
are engaged in "picking" fish — that is, when fish are scarce,
and only one fish at a time is being caught.
Locating the fish
The vessels are usually equipped with echosounders which
are used primarily to locate the rocky bottoms where fish are
to be found, but occasionally sounding leads with hollow
bottoms are used. The hollow is filled with soap and the soap
is examined after each sounding for traces of coral rock which
indicates the possibility of fish. When a location is found by
either method the vessel is anchored and fishing begins. If
the location proves unproductive the vessel is moved until
satisfactory results are obtained.
Since the bottom areas where fish may be found are usually
quite small, great skill is required on the part of the vessel's
master in estimating the length of his anchor rode and wind
and tide direction in order to bring the vessel directly over
the rocks.
Because of the age and variety of vessels engaged in the
Plan
Fig 38. Lines of grouper and red snapper fishing boat
[623]
fishery, there is no standard type of construction, both steam-
bent and sawn frames being found at random. Recently-
constructed vessels, however, have tended towards double-
sawn frames, spaced on 12 in (30cm) centres and generally
have averaged 46 ft (14 m) in overall length. Construction is
from native woods, generally long-leaf yellow pine for keels
and stems, with cypress for planking which is usually 1J in
(32 mm) in thickness. Planking methods are generally carvel,
but no caulking is used, the seams being allowed to swell
shut. Lately, good boatbuilding lumber has become in-
creasingly scarce in the State and fir is being substituted for
cypress in the planking. Fig 38 illustrates the lines of a
recently-constructed vessel for this fishery and more or less
illustrates the type of vessel that is built primarily for this
trade.
Power and equipment
Motive power for the vessels is almost exclusively diescl,
with the engines ranging from 65 to 90 hp as a rule, although
larger engines are found in a few modern vessels. Speeds
average 10 to 12 knots. Cruising range, with the exception of
vessels designed to operate on the Campeche Banks, is
limited, since the fishing grounds are located 50 to 100 miles
off the coast, with the actual fishing done while the vessel is
anchored. Costs of construction vary greatly, but it would
seem safe to say that a new 46 ft (14m) vessel of wooden
construction would cost from £5,400 to £7,100 ($15,000 to
$20,000), ready for sea.
Fish-hold construction ranges from simple wooden boxes
to well-insulated holds lined with 3 to 6 in (7 to 15cm) of
styrofoam. Tn the foam-lined holds, the foam is placed
directly against the ceiling, fastened in place and covered with
wire mesh, over which a layer of cement J to I in (13 to 19
mm) in thickness is placed.
Refrigeration consists almost entirely of chipped ice. The
fish, in the less well-constructed holds, can be held up to a
maximum of 20 days, but very few voyages last this long as
the average catch is from 5,000 to 7,000 Ib (2,300 to 3,200 kg),
which requires about a week to 10 days to catch. Methods of
storing the fish vary. Some of the shore-based processing
plants require that the fish be gutted immediately after being
caught. Others do not. Generally the fish are stored in layers,
with 2 to 3 in (5 to 7 cm) of ice between layers.
Crew strength and operation
Crew accommodations on the vessels range from extremely
primitive to fairly complete. In no instance, however, could
they be termed luxurious. The crew usually numbers four to
six, with perhaps a dozen being found on the larger vessels.
While extremely competent at their trade, the fishermen,
with the exception of the master, seldom meet very high
standards otherwise. Masters average £5,360 ($15,000)
yearly income.
The vessels arc usually operated on shares — one share for
the vessel, one for the master and one share divided amongst
the crew, although this may vary slightly.
Grouper landed at the dock in the early part of 1965 was
bringing approximately 1/3 ($0.18) per Ib, with snapper
bringing approximately 2/5 ($0.34). These prices, however,
have been under extreme downward pressure recently from
imported fish, which can be sold at retail levels, filleted, at
from 2/5 to 2/10 (0.34 to $0.40) per Ib. As a consequence,
great difficulty is being encountered in raising capital to
invest in more modern vessels for the fishery or in modern
shore-based processing plants. Despite these difficulties,
however, it is thought that bottom fishing for grouper and
snapper will be an important fishery for some time in Florida,
as the fish are readily available, as are average vessels that can
Pig 39. Snapper fleet in Pensacola Harbour
be converted to the trade. A snapper fleet docked in the
harbour at Pensacola is shown in fig 39.
Problems for developing countries
Paz-Andrade (Spain): The present technical situation in the
developed countries affects development in countries which
are increasing their fisheries. Fishing in general now finds
itself in a vicious circle. The skipper wants to increase the
size of his vessel without becoming involved in complicated
economics concerning the rentability of his ship, this increase
in size is a reaction against two factors:
• Ovcrfishing of resources, thus requiring larger ships to
get the maximum possible catch from dwindling
resources
• The need to make longer and longer trips
This circle must be broken. In Spain there was a fleet of
small ships, coastal, side and pair trawlers. The pair trawlers
dominated and gave good results. However, the time came
when the need for refrigeration and new fishing grounds
further away from home ports, e.g. South Africa, indicated
the need to find a midway solution. For example, one
enterprise bought a factory ship of 5,000 tons. They built
ten small stern trawlers, which were equipped also for purse-
seining and these were combined with existing small vessels
to give a fleet in which small catchers worked in combination
with a factory ship. This provided a good fleet combining
smaller vessels with large freezing factory ships and eco-
nomically it was a good solution.
Spain is now the second most important nation in Europe
producing maritime fishing equipment. In Spain the fleet
consists of 30,000 vessels, but although there is a large factory
processing vessel, some 20,000 vessels arc still propelled by
sail or oar. Thus it can be seen that they arc in the midway
stage of fisheries development. Especially from the social and
economic position, one must still consider the small fishing
boat, but one is particularly interested in utilizing them in
larger enterprises, say with a factory ship as the mother ship
and a fleet of small catcher boats.
Australia's crayfish industry
Cormack (Australia): Well boats predominate the Australian
crayfishing industry. The boats are usually full-ended with
the fish well situated amidships. Accommodation is arranged
forward with the engine and wheelhouse aft. The wheelhouse
[624
is constructed over the engine-room trunk and is readily
removed. A few recent boats have been built with the engine
and wheelhouse forward (fig 40). These are proving far better
boats working among pots, giving better vision to the helms-
man. The boat illustrated was top crayboat out of Port
Adelaide in her first season 1963-64. In this latter type, sails
have been dispensed with entirely. These boats are all built
locally, constructed of Australian timbers, with the exception
of deck beams and decking, for which some builders use
Oregon pine. For these latter members, Australian oak has
been used for beams and Tasmanian cclcrytop pine for
decking with success.
Fix 40. Linda Bruce, 51 ft Loa x 15 ft B x 6ft 6 in D. Top Port
Adelaide cray boat in her first season 1963/64
The crayfish boats range in size from 18 to 6()ft (5.5 to
18m) overall in length. The smaller boats are invariably
half-decked, working only a few pots, close inshore and single-
handed. Average size would be in the 40 to 5()ft (12 to 15 m)
range. For the crayfishing industry, the most economical
boat would be in this range. The most suitable are beamy,
full-ended boats with the beam carried into a short, wide
counter. The advantage of the big deck area for working
Fig 41. Star of South from the starboard quarter
and also the carrying of pots is obvious. Average number of
pots worked per boat is 70 to 80. A typical example is shown
in fig 41, whilst fig 42 makes a comparison of the beam of
these boats with normal standards.
Boats in South Australia are divided into two classes, those
working Kangaroo Island shores and those working the
South East Coast. Those working Kangaroo Island are
based on Port Adelaide, 80 miles distant. Of consequence, the
large deck area provided by a large square stern is necessary,
as all cray pots are recovered and returned to port each
voyage. Each voyage would be of 10 to 14 days' duration.
In the South Eastern ports such a large deck area carried
right aft is not nearly so important and many boats there
have cruiser sterns. These are virtually day boats only and
BtAM-LtNCiTH *
LINf, T M HI T
Fig 42. Beam-length curve of Australian cray hoats
the pots are left on the grounds for the entire season, necessary
running repairs being the only exception. The working area
amidships, the lowest point of the sheer, which is kept to a
minimum, being a little aft amidships. A sheer height at
this point of 2.5 ft (0.75 m) being considered a maximum.
For pot-hauling purposes, the pot line is led over rollers lined
to the bulwark rail capping to a vertical winch. This winch
Fig 43. Pot winch set for hauling
is driven from the main engine. A typical winch is illustrated
in fig 43. The ability of the boat to hold her position during
the pot hauling is a decided advantage, and experience has
shown that the boat with a steep rise of floor does this
reasonably well.
Choice of the owner
Choice of engine make and power in these vessels has been
mainly on the whim of the owner. In many instances, boats
are overpowered or as in others the engine is never run at
maximum revolutions. Thus the cost in both original outlay
and running is far from economical. The same could be said
for propeller selection. In most propellers for these boats
are purchased "off the hook". With a correctly-designed
propeller, together with adequate fairing of the stcrnpost into
the propeller, added to a better selection of horsepower for
a given hull, would greatly reduce running costs. Fairing of
the sternpost was advocated by Traung when visiting Australia
in 1964 and 1966.
The fish well is one of the most vulnerable parts of these
vessels, and unless properly constructed, is a continuing
source of annoyance. Bed logs of the well should be securely
[625;
Fig 44. Fastening well into hull
through-fastened, and the bolts set up on adequate plate
washers against the hull planking (fig 44). These plate washers
are bronze castings and shaped to offer the least resistance.
The holes in the washers to accommodate the bolt head
should be tapered for the entire thickness of the washer. This
will ensure that the head of the bolt will perform its function
at all times even if some corrosion to the head has taken place.
Construction of "wells"
The thwartship bed logs are fitted directly to the hull
planking, i.e. between the bent frames. The fore and aft bed
logs are fitted over the frames; the space between the frames
being filled with hardwood blocks. The succeeding logs
forming the well are bolted to Jarrah straps secured to bed log
and beams and carlines. These straps are fitted on the outside
of the well. The logs are seamed on the inside to take the
caulking.
The well bottom over floors and frames is usually covered
with concrete at least 3 in (76 mm) in thickness. A longitudinal
bulkhead (open sheathed) is fitted to prevent excessive
turbulence in the well during heavy weather, which could kill
the catch. This also, of course, reduces the effects of the free
surface within the well.
In all these well boats, closely-spaced transverse floors are
fitted in lieu of full-length keelsons. These are of Jarrah or
Karri fitted between the frames to the planking. Fastenings
are copper through throat and tail. These floors are left
straight across the top with the exception of those within the
fish well. These latter are usually trimmed hollow at the throat
to avoid excessive depth of concrete in the well as mentioned
above.
Water is introduced into the well through vents cut in the
hull planking. This water is carried at all times, whether
carrying fish or not. Further saving in running costs could
be made if a tank were substituted for the well. Water which
could be circulated mechanically, as in a bait tank of a tuna
boat, need then only be carried when the fish have been caught.
Some half dozen of recent additions to the crayfishing fleet
have been so fitted. However, in the majority of these, the
move was unsuccessful, through some lack of experience of
the crews concerned. Fortunately in one boat, the scheme was
a success, due mainly to the perseverance of the owner, and
according to him the tank is far superior to the well. A boat
so fitted has the further advantage of being readily converted
to tuna fishing.
SIZE RESTRICTIONS
Hoeksrra (Netherlands): In the Netherlands there are certain
limitations on the size of the inshore trawlers regarding the
crew. The inshore fishing vessels in former days were mainly
in the category of 20 GT. Trawlers and drifters in the size of
120 GT. Vessels of 50 GT and more were obliged to have a
licensed skipper and engineer. As long as these inshore fishing
vessels were about 20 GT there were no problems, but due
to the increase of electronic equipment and better crew
accommodation, the deckhouses became bigger and bigger.
To retain good stability, especially when beam trawling, the
principal dimensions had to increase and after a time the
50 GT limit was reached. On the other hand there was, and
there still is, a shortage of licensed men, and in spite of this
the size of vessels continued to increase and could not be
stopped for economical reasons at the 50 GT limit.
Builders tried to build fishing vessels of a maximum length
and not exceeding the tonnage limit, using all the tricks of
tonnage measurement, to give the vessel such a form that
the demand for bigger ships does not result in exceeding the
50 GT limit. This might result in new ships having less stability
than the older ones. The application of measurement rules
now can result in a licensed crew or not for ships of the same
length. Thus the gross tonnage is not a good indication of the
size of a fishing vessel, and should not be used in laws, in
which it is necessary to indicate the size of a vessel. Length
overall, for instance, is a better indication.
Dutch small trawler-owners are hesitating to accept designs
of a fishing vessel of less than 100 GT fishing over the stern.
It may be true that the fishing operations are easier when
fishing over the stern. However, there is an objection from the
point of view of accommodation. When steaming into a heavy
sea, the pitching of the vessel makes forward accommodation
NUMBER OF VESSELS (1962)
1500.
1OOO
500_
0 20 40 60 60 100 G T
Fig 45. Number of Danish fishing vessels in function of GT
T6261
18QQ
5QQ
NUMBER OF VESSELS
. Number of Danish fishing vessels in function of lime
very uneasy. Here is the dilemma of better fishing operation
conditions or better accommodation.
De Wit (Netherlands): It can be agreed with Hoekstra that
gross tonnage as a measure of the size of fishing vessels has
had an unsound influence on design. There is a growing
tendency to replace gross tonnage by length. For certain
regulations, e.g. number of crew, in the future, length will be
used in the Netherlands for classifying fishing vessels.
Practice in Denmark
Pedersen (Denmark): Gross register tonnage may be a highly-
misleading guide for classification of size of a vessel. Length,
or still better, displacement, gives a much more exact figure
on the size of a vessel. Demands for trained crew, safety
equipment, port duties, etc., when exceeding certain GT
limits, play a vital role in respect of limitation of size. The
trend naturally will be a concentration of vessels with GT
just below such limits, or to use every effort to get the vessels
"measured down" below the limit.
In Denmark there are GT limits on 20, 40, 50, UK), 200 etc.
GT. Some naval architects specialize in the design of these
so-called paragraph vessels. In the range 5 to l(X) GT in
which most fishing vessels fall, the 20, 40 and 50 GT limits
clearly are distinguished in fig 45. Only boats above 10 GT
arc taken into account. For vessels above 20 GT, a skipper
must have a certificate, while below this limit anyone is
allowed to sail a boat. Therefore most of the smaller boats
arc classified at 19.99GT. For vessels above 50 GT, two
crew members must have certificates. Therefore vessels
15 -If. 9 GT
Fig 47. GT of Danish fishing vessels in function of time
[627]
group about the 49.9 GT value. Above 40 GT harbour duties
in many Danish harbours rise rapidly; consequently many
vessels are registered at 39.9 GT. In Esbjerg, the largest
fishing harbour in Denmark, approximately 35 per cent of
all boats are registered in the 35 to 39.9 GT range. Fig 46
shows how the number of vessels inside various GT groups
vary as a function of time.
In fig 47 the gross register tonnage inside various GT groups
is shown how it varies as a function of time. If the smallest
group of 10 to 14.6 GT, which shows the constant trend, is
excluded, the most popular and expanding group is the 1 5 to
19.9 GT group, which is followed by the 35 to 39.9 GT, and
the 45 to 49.9 GT group.
As is well known, register tonnage is measured as the inside
volume of the vessel. Most owners want to get as large a
vessel as possible, and there has been a tendency to increase
moulding dimension of transverse members to obtain a large
displacement for a fixed GT. On so-called "large" 20-ton
boats, the frame moulding is kept constant from keel to deck,
and even increased considerably above the rule scantlings.
The authorities have only cared about the inner volume of
the vessel, and it is a fact, roughly speaking, that many
vessels are registered at 19.99GT regardless of outside
dimensions.
This tendency, however, became so exaggerated that the
Ship Inspection authorities in 1962 stated that only an
increase of 50 per cent above the rule scantlings (moulded
dimension) was accepted for the purpose of giving a reduction
in the measuring and calculating for the gross register
tonnage.
USA's Improvement Act
Pross (USA): A brief description of the US Fishing Fleet
Improvement Act of 1 964 under which scalloppers and other
vessels are to be constructed might be of interest.
• The US Fishing Fleet Improvement Act of 1964 was
designed to make the US fishing fleet more competitive
with vessels of other countries
• Up to 50 per cent subsidy is paid on construction of
fishing vessels. This subsidy is based on an estimate of
the foreign cost of the vessel in a selected shipbuilding
centre, i.e. the owner pays the foreign cost and the
US Government pays the difference between the
foreign cost and the lowest domestic bid. Reason:
old law not allowing catch to be brought into the US
from anything but a US-built vessel
• The giving of the subsidy by the US Government has
a slight catch, i.e. Congress realized that the re-
building of the same old type of boats would not
improve the relative status of the US fishing fleet.
Therefore, the vessels have to be of advanced design,
have the most modern gear available aboard them,
be able to fish in extended areas. To do this (fish in
extended areas) the vessel must have increased fuel
capacity, larger main engines, increased hold capacity
over previous vessels etc., i.e. they must be a much
better boat than is currently operating in the same
fishery or they must be seeking to exploit new fisheries
• The programme is essentially just beginning, but
already quite a variety of vessels has been submitted.
In addition to the 100 ft (30.5 m) steel stern scalloper
already described, the following types are in various
stages of processing:
100 ft (30.5 m) steel stern trawlers
97 ft (29.6 m) combination boats, as described in
Reid's paper
88 ft (26.8 m) steel longliner-trawlers used for
swordfish
86 ft (26.2 m) steel shrimp boats
1 50 ft (45.7 m) aluminium menhaden boat
220 ft (67 m) steel menhaden boat
150 ft (45.7 m) tuna vessels
265 ft (80.7 m) stern factory trawler with filleting
machines, fishmeal plant, plate and blast
freezer and all the other equipment associated
with this type of vessel
As Congress and people become more aware of the impor-
tance of the fishing industry to the USA, this programme
should expand and the number of vessels built under it increase
greatly.
Trends in Portugal
Cardoso (Portugal): Competition in fisheries, overfishing or
near-overfishing in some areas and the extension of exclusive
fishing zones have spurred the owners and technicians to
demand the building of larger, faster and more sophisticated
ships which can move faster from distant fishing grounds,
stay there longer, process the fish and offals and entertain
and attract a crew.
The growth in size of fishing ships in the last 10 or 1 5 years
has been a curve like— a cubic, at least. It is, however,
becoming more and more evident that the curve of profit-
ability as a function of size is a Gaussian curve of some kind
—see Gueroulf s fig 8. It is no wonder, therefore, that already
some valiant efforts are being made to make fishing vessels
more compact, with reduced crews and consequently con-
siderably smaller.
The fishing vessel should be not only a safe machine for
catching fish, but also a safe machine for making money.
This function of the fishing vessel has not been too often
mentioned. It is important that the biologist, the economist
and the technologist help the naval architect, in influencing
and determining that point.
The combined purpose is to increase the wealth and welfare
of nations and to build economically wrong, although
technically beautiful, fishing fleets, would be catastrophic for
that wealth and welfare.
FUTURE DEVELOPMENTS
Chairman's introduction
Nickum (USA): We now come to that nebulous and limitless
area which we call "the future". While this session is open to
any ideas and any concepts that you may have, some form is
needed to keep the discussion along logical lines and I there-
fore suggest that we channel our discussions into the following
categories.
First, let's look at methods of fishing. For thousands of
years we have been catching fish by three basic methods.
One way is with a hook; another is with a harpoon, and the
third is with a net. Isn't it time for something new? Can the
fisheries' technologists find a shape or a colour, a noise, a
taste, a light, or a vibration intensity that fish either don't
like, or like, which would allow them to be repelled or
attracted into a fishing harbour? If the experts on the be-
haviour of fish and the fishing gear technologists can find
some new way to catch a fish the naval architects have all
the knowledge necessary to design the new types of boats
which may be required.
Let's talk about future types of equipment. What kind of
equipment and machines do the fisheries people need? Do
they need radar that will scan and locate fish at the surface
of the water in amongst the waves? Can they locate schools
of fish accurately enough so that we could build a machine
for them which could be towed through the schools and
would deliver fish oil out one side and fish meal out the
other?
[628]
What kind of propulsion equipment will be used 20 years
from now; and are the manufacturers expending their research
and development funds in the right way? We have heard
about outboard motors and the problems of life and
dependability of units primarily built for pleasure craft when
operated in remote locations without servicing and spare
parts facilities. We have heard manufacturers say they can't
spend large amounts of money making the units more
rugged and dependable just to supply a demand that is only
a very small percentage of the total overall market. Is there
a way in which we can correct this?
Let's consider methods of design. Are we neglecting
developable surface forms such as Kilgore's, now that we
have methods to produce them? Are we going far enough
in computer studies, either in developing optimum ship forms
or in developing a tool for better utilization of fishing time in
getting fishing vessels to more productive grounds?
We have heard here about the individuality and character
which we admire in fishermen— their desire to own their own
boat — their desire to be their own master. This is, of course,
valuable and certainly promotes initiative. But let's face the
fact also that in this modern world unfortunately it is the
big organizations that arc making the major developments.
Shouldn't we face the inevitability of a change from small
individual enterprises to major group efforts?
Aim is increased productivity
Finally, let's consider the business of catching fish in its
entirety rather than its separate parts. Remember that the
basic purpose of this meeting is to get increased productivity
in fishing. We want to catch more fish with fewer man hours
of labour and fewer costs for physical facilities. At the
present time we take our fishing equipment, place it on board
a ship, and don't use it at all while it is going out to the
grounds. We fish with it for a while and then turn around and
take it all the way back into port and let il sit while we unload
and get ready to start the cycle all over again. During this
period while the fishing gear is not being used the fishermen
are either doing nothing or are navigating and sailing the
ship to and from the grounds. Think of an idea like this.
Suppose we take a stern trawler, for example, and let the deck
at the stern consist of a number of small compartments, each
fitted with watertight hatches. The vessel catches a load of
fish. Instead of turning the ship around and heading back for
port let's put the fish in these removable compartments; run
up to a nearby location where some spare compartments arc
floating, drop the loaded compartments into the water, pick
up the spare compartments and start fishing again. A mother
ship can come out and pick up the loaded compartments,
transfer their cargo to her hold, fill the compartments with
stores, oil or water, and leave them ready for the next fishing
vessel of the group.
Perhaps we can have a hydrofoil boat running to and from
this central gathering spot which can bring out new crews and
take the old ones back. Perhaps we should use aeroplanes.
Isn't this a means by which we could get rid of unproductive
hours, and get the fisherman home to his family, so that he
has a working week comparable to a man working on shore?
Isn't this a way the fishing vessel operators can compete for
labour with the manufacturer?
Trends must be considered together
Margetts (UK): Future methods of catching and future types
of ships should not be considered separately. Cardoso is
concerned about the changes occurring in fish stocks. The
so-called developed countries have overfished many of their
own local grounds and are still searching further afield. Big
ships or big fishery units will put more pressure on the in-
shore fisheries, where it will be even more important for units
to be adaptable so as to switch between different catching
methods and catching different species of fish. In many
developing areas, the local sea fishermen will be competing
with big units from developed countries.
The biologists expect that the searches of the world oceans
will reveal some unexploited stocks, particularly of pelagic
fish. The major fishing fleets will probably continue to develop
power methods in which a premium will be on towing and
hauling powers.
Gear technologists and biologists are working towards
better designs of gear, especially of trawls, and towards
understanding the behaviour of fish, the better to turn their
natural reactions to account in achieving their capture. Most
modern development is in big ship methods. Although some
of the general genuine principles of design of gear will apply
to small-boat methods, it will not always be wise to scale-
down big gear to small size, e.g. big single-boat midwater
trawls are now used to catch cod in midwater, but small
single-boat midwater trawling is not likely to be successful
for catching cod.
Nowadays more attention is being paid to fish farming of
marine species. It is unlikely that this will be done, in the
manner envisaged by Cousteau and Hardy by totally under-
water operations requiring submarines and dual-purpose
underwater boats or tractors, but is likely to be by intensive
farming in enclosed sea waters where there will be a need for
specially designed small boats and river craft.
The most modern aid to fish-catching is electricity. The
use of electricity in sea fishing is being successfully adopted at
the research level and practical commercial methods may
follow, probably by using electro stunning in conjunction
with trawls. If so, there will be new scope for ship designers
to build ships including all the extra generating plant.
Danger of pollution
von Brandt (Germany): The future of sea fisheries may possibly
be the same as it has developed, especially in Europe, for the
freshwater fisheries. In fresh water the pollution of rivers and
lakes is increasing rapidly, transforming the freshwater
fishery from the fisheries in lakes and rivers to the pond
fishery and hatcheries.
It may be that this will also occur in sea fisheries. Perhaps
it will be impossible to prevent the contamination of the sea,
e.g. with atomic waste. Also in this case sea fisheries may be
driven away from the open sea to protected enclosed areas with
known stocks kept under regular management like cattle and
so on.
In the near future midwater trawling is expected to become
more and more important for small and large vessels as
mentioned by Margetts. It is also to be expected that in
future the depths for bottom trawls will increase to 3,(K)() ft
(1,000m) and more. That would cause new problems for
better deck arrangements, such as winches and warps. It may
also occur that a higher efficiency of bottom and midwater
trawls may be achieved by means of electricity.
Kffect of noise on fish
Takagi (Japan): In 1936 it was known that when whales
were followed by catcher boats, they tried to run away. This
is the reason why people used the steam whalers. However,
if boats run parallel with whales inshore, they do not run
away from the boats. In 1936 an experiment was made to
measure the speed of whales in open sea near Japan. Ten
boats were run parallel one to the other, with a submarine
chaser capable of over 20 knots at each end with the eight
whalers in between. As soon as a whale was found, the outer
submarine chasers started to run after the whale and as a
629]
result it was observed that even a whale over 80 ft (25 m)
could not move any more after 30 minutes. The surface speed
of the whale was 14 knots. Therefore it was concluded that
whales would not be able to escape from boats faster than
14 knots and noise from the boats should not be any problem.
Thus Japanese whalers started to employ diesel engines.
Bardarson (Iceland) : Studies on the hearing offish have shown
that fish have a hearing range apparently within the same
range as the human ear, possibly somewhat more, but varies
according to the species. It has been indicated that herring
and fish of the same family are more sensitive to noise and
have a greater range of hearing than most other kinds offish.
These observations are based on experiments carried out in
aquariums or in the open sea, by keeping the fish within a
limited area with nets. By sending out sound in different
ranges and noting the reaction of the different types of fish,
the sensitivity of the fish concerned could be registered and
compared. The above results are in conformity with the
practical experience of Icelandic fishermen. It is the general
opinion of Icelandic fishermen that noise from fishing vessels
does not generally disturb cod fishing, but can considerably
disturb herring which is to be caught with purse-seine
especially in good weather during the day.
Icelanders seek quiet approach
If a single fishing vessel is approaching a school of herring,
and when catching, it is a general opinion of Icelandic fisher-
men, that it is of great value to keep noise from the fishing
vessel to a minimum to prevent the school from disappearing
into a safe depth beyond the depth of the net. When several
vessels are spread around, thus making the noise level rather
similar and constant within a certain area, it seems that the
herring are not so disturbed by the noise as when the noise
comes from one source only. Constant noise therefore seems
not to cause as much disturbance as a sudden change of noise.
It is not a new idea that noise from fishing vessels disturb
fish to make fishing impossible. When steam ships came after
sailing ships, it was thought that the noise from the steam
engine would soon drive the fish from the fishing grounds.
This proved not to be the fact. Later, the noisy diesel engines
followed after steam engines in fishing vessels, and then came
many types of noisy auxiliary engines and equipment, but
still fish are caught on the fishing banks. This should, however,
not be taken as an indication that fishermen's views as regards
the herring fishing should not be taken seriously.
Some fishing vessels catch less herring than others, although
the vessel's type and size might be similar and the ability of
the captain and crew comparable. By listening with an
underwater microphone and recording on a tape recorder the
sounds from different fishing vessels at the same distance at
the same place and same weather and sea conditions, it may
be found that ship noise and character of the noise varies for
different vessels. If testing in the same manner one vessel, it
may be found that the type of noise and noise level can vary
widely, with altered revolutions of the main engine, with
altered pitch on a controllable pitch propeller, by starting,
stopping or changing the revolutions of auxiliary engines and
equipment such as pumps, winches, etc.
Tracking fish with tape recorders
By first listening to and registering on a tape recorder the
characteristic noise from a certain fishing vessel, then taking
the vessel on land and changing one item at a time and then
registering the noise in the same way again, at exactly the
same distance, same depth of water, same surroundings etc.,
there is a possibility of comparing the different single items
affecting noise. This is a practical approach to a problem
with full-scale tests on the ship itself. It is a very costly and
time-consuming method, but is still believed to be the only
practical way to study the noise from a certain ship.
Excessive noise may be due to many things. Among them
are damaged propeller blades, propeller cavitation, in-
sufficiently balanced or inexact pitch of the different blades of
the same propeller, limited space around the propeller or
disturbed flow of water to the propeller, which can be due to
thick and square sterns as in wooden vessels— auxiliary
engines on top of a flat tank can also produce vibrations and
noise. All these, and many other items have to be considered
when studying noise from fishing vessels.
It is believed that noise from herring fishing vessels should
generally be kept to a minimum, but it appears that under-
water noise from fishing vessels and its influence on fish has
not yet been studied sufficiently. Experiments in this field are
needed both on a scientific and technical basis, to increase
knowledge of the problem as a whole. Such experiments are,
however, costly and complicated, since so many different
unknown factors are involved. At any rate noise should be
given more consideration in the future development of
fishing vessels than has been done generally until now.
How fish react to noise
H0gsgaard (Denmark): In Denmark soles are caught in
shallow water, but fishermen say that soles cannot be caught
in the daytime because they are so deep in the sand that they
are not taken out with the net. A Scottish film about Danish
seines showed how fish escaped from the seines; when the
fish had been collected by the sweep lines and were nearing
the net, the most powerful of the fish went right up and over
the top. Then on the headline of the seine between the two
wings, H0gsgaard placed a line on which he placed two
artificial fishes of white plywood, with cork. When the soles
started to go up in the water, they were frightened by the
white fish and escaped down into the seine. This has been
proved many times.
Traung, page 385, mentioned that fish can be scared by the
noise of ships and Bardarson said the same, and Hogsgaard
having travelled around the world so much said he had similar
ideas. About ten years ago he had talked with a man in Nova
Scotia, owner of two boats, from which the crew harpooned
swordfish. This man said that they kept the old-type engine,
the engine without a reduction gear between the engine and
propeller shaft. With this engine the ship can move closer to
the swordfish. And then some years later, Hogsgaard went
to the Faroes and there were three small whalccatchers from
Norway which operated very well until one day one of the
ships just couldn't get near the whales. The owners cabled
to Norway for the reason and the Norwegian who had sold
the ship cabled back advising putting the ship on the slipway
to inspect the propeller, as it might have been loose. This was
the case.
Propellers sometimes not to blame
Recently a young naval architect asked whether Hogsgaard
could make him a noiseless propeller, to which he replied
that he could not but would make a propeller making less
noise than the normally-designed propellers. Cavitation
causes air bubbles and that means more noise again. A more
modern propeller will go smoothly through the water. The
young naval architect had complained that the herring shoals
would not go near the six purse-seiners they had in Iceland,
and H0gsgaard mentioned the story of Nova Scotia. It might
be that these ships have noisy reduction gears and one should
not put the blame on propellers. It is very difficult to make
reduction gears with little noise. However, the thickness of
oil used in the reduction gear is also relevant. So if fish are
[630]
scared away, it does not always depend on the propeller.
It is important to make noiseless gear that can be used in
fishing boats for the progress of the industry, and the type
of teeth is very important. The propeller people say it is the
fault of the gear; the gear people say it is the fault of the
propeller. It would be valuable to know what frequencies
fish do not like.
Handline fishermen always stop the auxiliary engine
because the noise frightens fish — however, with a diesel car
engine as auxiliary engine, one will have, not a noiseless,
but a very quiet engine when fishing, which will also afford
the crew a little more comfort. Anyone who has been aboard
ships knows that when the big engine is running one is in
Heaven, but when the auxiliary engines are running, one is
in Purgatory!
SUBMARINES
Pedersen (Denmark): Who are the best fishermen? Fish
themselves. Jt is a fact that bigger fish eat smaller fish. The
big mammal of several hundred tons lives upon shrimps.
These mammals only open their mouths and swim through
schools of shrimps in the Antarctic Ocean. It might be
possible to adopt this simple principle of catching animals in
the water, by making an artificial mammal, steered by man.
This means that such a submarine fishing boat, fig 48, should
have a "mouth" and "stomach", and the operator, when
detecting a school of fish on his sonar apparatus, dives down
to the proper depth, opens the "mouth", steers through the
school, which is collected in the "stomach" tanks, where the
fish may be kept alive until reaching port, just as in normal
fish well vessels.
The "stomach" tanks are fitted with nets of proper mesh
sizes in order to allow undersize fish to escape. Fish can be
sorted automatically if different mesh sizes are fitted in the
different tanks, just as stones, grained stones und sand are
sorted through a sieve. Water will flow freely into and through
the "stomach" tanks from small openings in the "mouth".
Supplies of food and oxygen arc thus provided for keeping
fish alive inside the tanks.
Power may be supplied from diesel electric alternators, in
connection with a battery feeding a slow-running electric
Fig 48. Submarine fishing vessels utilizing the mammal principle of fishing
[631]
motor, which again drives the large diameter propeller.
Vertical and horizontal rudders fitted behind the propeller
and in the nose, provide good manoeuvrability. The cylin-
drical main part of the body is divided in six parts with
longitudinal bulkheads around a centre pipe. The upper part
contains the buoyancy tanks; the lower part the fuel oil
supply, which rests directly on the seawater, as in normal
submarine practice.
The battery is situated below the fuel oil tanks in a special
pressure pipe. The electric motor is covered in a shield into
which compressed air is led in order to avoid water entering
the motor. Separate engine room and operator living room
will be of advantage. The engine room need not be contained
in a pressure hull, as compressed air can be led into the room
when diving in order to keep equilibrium in pressures. As
diesel alternators are stopped when diving, this arrangement
seems satisfactory.
Cruising depth is limited by height of the snorkel mast
naturally. This may be made so high as to allow a safe margin
for greatest draught of surface vessels in order to avoid
collision.
Possible advantages of submarine fishing
• The operator never touches the fish. He does not have
to haul a net with fish in bad weather, kill and gut the
fish, prepare and stack them in the hold under difficult
conditions. The only thing the operator has to do is to
find the fish, collect them, and bring the living fish to
a processing plant, either on land or on a factory vessel
at sea. The vessel can thus operate either as an in-
dependent unit or as a member of a fishing fleet
• There will be no trouble with winches, warps, nets and
ground gear, as such items do not exist. Maintenance
costs on nets will be low, as only a trawl mouth net is
needed
• The vessel can fish independent of weather conditions,
as it is always calm below the water surface
• Through the periscope, antennae, decca etc., situated
on top of the snorkel mast, the operator will have the
same, or a better view, as a skipper on a surface vessel,
when the boat travels as a surface vessel
The following questions require answers:
• Can the fish be kept in good condition in the "stomach"
during a fishing trip of, say, ten days, if the concentration
of fish is high ?
• Can the school be concentrated and attracted towards
and into the mouth by using, for instance, light,
electricity, or other attracting devices such as stimulating
solubles let out into the water from the end of the
mouth ?
• Can the school be "frozen" for a moment by using a
form of shock-waves (ultrasonic sound, etc.) trans-
mitted from the nose in order to harvest the school?
• Is there any risk that sound from the electric engine
may frighten and split the school (constant low-
frequency noise level assumed) ?
Investigations made by FAO
Traung (FAO): When the first atomic powered submarine
went under the Arctic icecap, officers in FAO were impressed
by the possibilities of fishing untapped resources under the
ice, using a submarine without any contact with the surface.
One FAO naval architect with previous experience of sub-
marines looked into the possibilities of adapting a second-
hand submarine for this purpose. He started off by investi-
gating whether it could tow a trawl and then found that the
hauling of the trawl would be quite complicated — how to
separate the fish from the net, shoot the net again, etc. Then
somebody suggested considering the submarine as being at
the end of a codend of a free-running trawl. It was suggested
to use a simplified trawl, towed by four small torpedos that
were radio controlled from the submarine, which was hung
in the codend. The gear had then a very large screening area
and the fish would be collected in the bow of the submarine
for further transfer to some pressure chambers, where they
could be properly boxed, iced and kept. Still again, there was
a problem how to handle a net like that, and another idea
was to have some telescope poles which one could press out
by air through the bow of the submarine. The poles were to
have many small holes so that air bubbles could be sent out
and the unit form a kind of new fishing gear working with
air as "webbing". The air webbing would force the fish into
the pressure chamber, which then from time to time could
be locked, the water pumped out and the fish put into a fish
room.
Fish attracted by light
Margetts (UK): The answer to whether light or electricity
can be used to attract fish is yes. Of the two, electricity offers
most likelihood for the whale-type catching submarine. A
steady noise from the engine would not likely frighten fish,
but sudden noise generated within the submarine or by
opening of the jaws is likely to scare the fish away. Bardarson's
observations about Iceland herring fishing support the
suggestion that steady sound is not so important, and also
that visual stimuli are very important in frightening fish.
As the supposed noise effect is most marked in Iceland in
calm weather and daytime, the inference is that the real thing
affecting the herring is sight not sound. To continue Pcdcrsen's
analogy, it is very likely that his submarine will be like the
shark from which, when they can see it, other fish flee. The
opening of the mouth of the submarine is likely to be frighten-
ing to fish in clear water.
H0gsgaard and Takagi both referred to the effect of ship's
noise on whales, the former speaker compared the reactions
offish and whales. The hearing of a whale, which is a mammal,
is very different from that of fish and the behaviour of the
two in reaction to noise is not comparable. The fish scarers
on the headline of H0gsgaard's trawl, it is believed, act by
scaring fish downwards by sight in daylight, as do the kites
on bottom herring trawls, while the effect of tickler chains
suggests that a lot of soles are not disturbed by the noise of
the oncoming trawl.
Some research work has been done in UK identifying and
measuring the noise generated by a trawler and different
sets of trawls and aquarium experiments are being conducted
investigating the reactions of fish to sound and other stimuli.
More scientific evidence on these subjects is required and an
analysis of the noises from ships could be profitable,
The opening of the jaws of the submarine wide enough to
be effective in catching fish— perhaps 150 to 300ft (50 to
100m) — while still moving forward presents a big problem
to the naval architect as the drag will increase enormously.
There is also the problem of stability and control of the draft
if it should catch a lot of fish, such as cod, with air bladders;
change in depth of the craft will alter the buoyancy of such
fish and ascent could be very hazardous.
Fish reaction to skin divers
Bonnassies (France): Just after World War 11 in France, a
suggestion on the lines of Pedersen was made to the French
fishery authorities, that is for submarine-type fishing. The
first difference was that the propulsion was by electric motor
which was fed by a mother ship. Secondly, compressed air
was installed to force the water out after the capture of the
[632]
fish. In the main fish-containing compartment, there were
electromagnetic means of deciding when the container was
filled. The container was then ejected and rose to the surface
as it was designed to be buoyant and was retrieved by the
mother ship. It is perhaps of interest that fish probably are
not frightened by the sight of menacing objects as has been
supposed. Skin-divers had little trouble in easily making
reasonable catches when this sport was first introduced, but
perhaps because of some memory device of the fish, the fish
now appear to avoid them and catching is more difficult.
Light might well attract fish and an asdic type of apparatus
as envisaged should be easily obtainable. Notably the Germans
and the Russians have experimented in the use of electricity
as a method of stunning fish and thus easily collecting them.
This collection could be easily undertaken by the underwater
submarine.
The suggestion to the French fishing authorities remained
as only a suggestion and was not exploited. A prophet is
never heard in his own land.
Birds are good fishermen
Dickson (FAO): Pederscn referred to the fish themselves and
to sea mammals as the best fishers of the animal world, but
he forgot to mention the birds. Jt is by their keen eyesight,
their means of communication both visual and vocal, also
by their great speed of movement that seabirds possess such
remarkable searching power. Searching power is the very
essence offish finding and it is in this very field that a technical
revolution is underway, a revolution which has started to
transform fishing operations. As fishing vessels become bigger
and faster, as fishing operations extend farther and farther
from the home port, organi/ed fish finding becomes more
essential. The means arc to hand, modern communication
systems can ensure that data is fed to a central point, data
processing methods can then deal with it there and com-
munications can redistribute the processed data. What is
mostly lacking is organization and enough technically
and scientifically trained people in the fishing industry.
The daily catch rate per hundred hooks operated by the
tuna longliners is transmitted to Japan along with the
position of the vessel. This data is processed by a centralized
technical staff and within two days the summarized catching
rates arc re-broadcast to the fleet. The re-broadcast is received
by facsimile machine which prints out the catch rates by area
squares on a world chart. The system is similarly used for the
broadcast of weather charts. Thus skippers can have an up-to-
date picture of generalized weather and fishing conditions in
all surrounding areas. Some trawler fleets are also on the
threshold of such developments and it may be that as well as
catch data, echosounder search data will also be processed
and the two thus become better correlated.
Value of collection and communication of information
Communication instruments of this sort, plus the use of
more instrumented fishing gear, such as netzsonde guided
midwater trawling, the telemetering back to the ship of
information on fishing gear performance, sonar guided purse-
seining and the like, look more promising than submerging
a man on the fishing gear. His field of visibility is so very
limited and the safety precautions surrounding him so con-
siderable that the ratio of information gained to money spent
is likely to be much lower than with the submersion of fish
finding and observational instruments. It is not meant to
imply by this that mankind has no future under the oceans,
but simply that the idea of a man sitting in the place of the
brain of an artificial whale is not the most promising approach.
There is also a structural objection to the artificial whale
idea with its fishing gear at the head-end pushing it along as
it were so that the catch enters by way of the "whale's"
mouth. This arrangement implies large members in com-
pression and it is to be noted that all the biggest and most
successful fishing gears can only be so big because they aie
completely flexible, and therefore without any members in
compression.
AIRLIFT PUMPS
Reid (Canada): Airlift pumps are used in Canada for dis-
charging fish out of the net. In a dewatering device of a
12 in (3(X)mm) pipe, compressed air is introduced which
tends to boil the water at standing point, and with this system
a 25 Ib (11 kg) cod has been driven up to 14ft (4.25m)
above the level of the water.
Utilizing the possibilities of this airlift pump, one can
imagine a fishing system utilizing two tug boats operating
one mile apart and each towing a large oversi/e trawl door.
The tugs would also tow together a fish collecting vessel some
two miles behind. The trawl doors together would tow a
trawl of gigantic proportions and in the codend of the trawl
one would have a pipe connection to the fish collecting vessel,
to which the fish would be delivered by help of the airlift
pump.
In midwater trawling, it is difficult to keep the correct
trawling depth, but with the two tugs in this way towing the
trawl and the collecting vessel, it would be a simple matter to
slacken or tighten the trawl to achieve the desired vertical
height of the gear. Please consider this as one off the-cufT idea.
Promises recalled and answered
Lenier (France): At previous FAO fishery congresses the
Japanese have promised many good developments for the
future. For instance at the FAO Research Vessel Forum in
Tokyo in 1961 there was a suggestion that work was being
done on bulbous bows for trawlers. It was suggested that a
ship would require only one-twentieth of a conventional
vessel's power, but no result of this suggestion has been
published.
At the Rome Fishing Boat Congress in 1959 some pictures
were shown of a proposed nuclear power fishing vessel, for
which is was said that funds for construction were already
available. No more of this suggestion has been heard either.
Could the Japanese delegation enlighten us on these subjects?
Takagi (Japan): Answered Lenier's queries:
• Inui of the University of Tokyo presented his paper on
the so-called Inui bulb to the FAO Research Vessel
Forum in Tokyo in 1961 (Inui, 1961). Since then, this
bulb has been applied to many vessels, not only
Japanese vessels, but also vessels of various countries.
Even in Gcitcborg a few vessels under construction
have Inui bulbs. This bulb was applied to a few
fisheries research vessels, but until now has been used
mainly for merchant vessels. The fuel saving is some
20 per cent, a reduction of the power to one-twentieth
was never claimed.
• The atomic fishing vessel proposed at the second
fishing boat congress in 1959 was in a session about
fishing vessels in 1975. Fortunately, there are ten years
more until 1975 and Japan will certainly complete
an atomic research vessel before then, because an
order for such a boat will be given in 1967.
PROPULSION
Borgenstam (Sweden): Gas turbines have often been talked
about and are now to a certain extent used by the Navy.
633]
What about using gas turbines in fishing boats ? Unfortunately,
inherently in the gas turbine is a high fuel consumption and
a complicated construction. It is also sensitive to salt water
in the inlet area. The development of gas turbines is towards
units with high output, especially suited for the Navy. Fishing
vessels will probably be the least possible application of gas
turbines.
Concerning outboards, it must be remembered that it is
the pleasure boats who are the main users and they will
therefore decide the design. However, for small fishing boats
one could keep the top part, the engine head, which is now
well developed with good enclosure and good starting
property, and modify the lower part. In the usual motor, the
top part of the engine is 75 per cent of the total cost, while
the lower unit represents 25 per cent. A new more slow-
running lower unit will probably cost three times the price of
the present lower unit. However, outboards have so many
advantages that the effort might be worthwhile.
A lot has been said about the necessity of teaching. There
seems to be a great need for new teaching methods, for
example, plastic models to better illustrate what is taught.
COMPUTERS
Doust (UK): Several computer programmes are available to
designers of future vessels, which relieve one of many routine
calculations formerly done by hand machines, although, even
now, full advantage of these facilities is not always taken by
some trawler yards. Such programmes are, at present, con-
cerned with the evaluation of hydrostatics, capacities, stability
characteristics, including design stability and hull strength.
For those not familiar with output data derived from such
programmes, the section of the Traung, Doust and Hayes
paper dealing with stability characteristics is a typical example
showing how the computer can be used to assess the adequacy
of beam and freeboard and to ensure an adequate range of
stability.
Now that resistance and carrying characteristics of the
smaller fishing vessels has been expressed in terms of their
hull shape and dimensions, it is possible to use a computer
to evaluate the relative merit of new proposals, thus avoiding
unnecessarily high-powered and inefficient designs which in
terms of fuel wastage on an international scale represents
enormous financial losses. It is a fact that an inefficient hull
design from the powering viewpoint is often the result of
badly chosen form parameters, leading also to bad motions
and seakeeping qualities, which further drastically reduce
economic efficiency.
With the theoretical developments now taking place in the
analysis of ship motions, wetness and loss of speed in various
sea states, it should be possible in the not-too-distant future
to define the desirable hull qualities, for fishing vessels in a
seaway more closely than is at present possible. It is therefore
an urgent requirement to study the quantitative effect of
factors thought to be, or already known to be, of major
influence on seagoing qualities, such as freeboard and flare
allied with the vertical and longitudinal distribution of area
above the waterplane, stem and stern contour shapes, in
addition to the distribution of weight in these vessels.
Probably the least understood aspect of vessels below
100 GT is the combined importance of dimensions, speed,
fish carrying capacity, fuel capacity, range of operation and
engine power on the economic efficiency. In this field, the
computer offers considerable scope in providing an additional
design tool, whereby the functions of a fishing vessel can be
simulated. By expressing the technical and economic perfor-
mance in an equational form which can then be interpreted
by the computer, the best economical areas can be derived
using linear programming or similar optimization techniques.
Since fishing vessels often tend to be built in fairly large
numbers to reduce shipbuilding costs, the mathematical
representation of the hull surface enabling computer-controlled
flame-cutting machines to be employed, is now a reality and
several fishing vessel designs are already being mathematically
faired.
The next logical step is one on which several workers are
engaged. This is to start from the optimized hull form
parameters and to develop a method whereby the computer
actually calculates the best form for the required condition
together with its shape. Three dimensional computer display
units are already available, which could be adapted for the
design of fishing vessels thereby enabling the effective changes
in one dimension to be seen in the other two dimensions.
Computers can co-ordinate through-put
Eddie (UK): The use of computers in design is not confined to
relieving the naval architects of their tedious arithmetic—
although of course that is a very worthwhile objective. An
example of another kind of application may be of interest:
the use of the methods of operations research to solve the
problem of choosing the optimum throughput for the
processing plant in a deepsea trawler.
It is well known that the rate of catch can fluctuate very
violently; single hauls can represent catching rates up to at
least 10 times the average for the trip. It is desirable although
not necessary for certain types of product, that the fish be
processed immediately after catching, but in the case just
quoted the processing plant would then be hopelessly
uneconomic. A plant which could deal only with the average
rate of catch, however, implies a very large buffer store at
times of good catching, and this is unacceptable because of the
handling problem and also because considerations of product
quality impose strict time limits on buffer storage before
freezing; the situation is further complicated by biological
phenomena like rigor mortis. It is not practicable to ask
fishermen to stop fishing when fishing is good. The best
choice for the size of the processing plant therefore lies
somewhere between the average and the peak catching rates,
but the range of choice is very wide and the choice is difficult.
Processing plant is very expensive in first cost and in space
and the choice obviously has a very great influence on the
economics of the vessel.
Practical use by WFA in Hull
The Industrial Development Unit of the White Fish
Authority working in conjunction with the University of Hull
has developed a computer programme which provides a
solution of the simulation type. For numerical solutions, this
requires records of fishing on a haul-by-haul basis, shifting
grounds and dodging weather, for the fishery under con-
sideration, sufficiently comprehensive to be statistically
representative of the pattern of operations on those grounds.
This information is stored in the computer. Various designs
of vessel are then postulated with different sizes of processing
plant and if desired, different sizes of hold, and the computer
simulates fishing operations with these vessels for, say, two
to three years, each succeeding haul being chosen at random
from the store. It can then be seen how often each design
would have had to stop fishing, what proportion of the catch
has to be handled in and out of the buffer store and so on.
The programme also includes consideration of costs and
earnings insofar as these are affected by the choice of proces-
sing plant and size of hold.
For the type of work described in Hatfield's paper, access
to a computer is not essential, but can be very desirable.
Many hundreds of metres of multiple-channel analogue
[634]
traces are produced on such trials and the results are digitized
by means of trace analysis equipment ; the use of a computer
for the subsequent calculations is sometimes desirable.
Work of data-loggers
Recently, data-loggers have been used by the Industrial
Development Unit of the White Fish Authority to record
automatically the performance in service conditions of deep-
sea fishing vessels and their machinery, throughout commercial
voyages, as a logical extension of the type of work described
by Hatfield. These automatic loggers record ship speed,
propeller revolutions, shaft torque, wind speed, fuel flow, etc. ;
the information is stored by punching a paper tape. The tape
is recovered at the end of the voyage and the information
upon it is digitized by a computer and subsequently calcula-
tions may be carried out also. Since automatic data-loggers
should be of interest to vessel managements as well as to
research development workers— they can be used for monitor-
ing engine temperatures and so on and as alarm systems it
may be as well to remark that these need not be very large
and expensive devices, such as are used by some tanker-
operating firms : the logger referred to above is a 20-channel
instrument which with the associated punch unit and black
boxes will occupy between a quarter and half a cubic metre;
the basic logger costs about £1,5(X) ($4,200). This makes it
feasible for quite small fishing vessels. One problem is that
ship motion introduces fluctuations in such parameters as
shaft revolutions and torque, but these can be automatically
integrated over a period of many seconds and averaged; this
is practicable if the correct choice is made by the designer of
the type of electrical circuit to be used.
Problem of keeping abreast
Cardoso (Portugal): The impact of computers allied to modern
methods of experimentation and testing make many times
obsolete today what was modern yesterday. All agree that
the naval architect of this day and age works hard just to keep
abreast of every clay's developments. The best sources of
information are the large national laboratories, experimental
tanks and research centres. It is, however, difficult to obtain
the latest published reports of such centres. It would be good
if those centres, either by publishing a journal or by keeping
the international technical press abundantly informed of
the progress of their work, could make the general practitioner
well-informed of the latest information on the best methods
and data involving modern design of ships.
Gone are the days when a good technical education and a
flair for design would be sufficient for the production of
successful designs, providing the best all-round solution.
So many variables must now be taken into account that only
the most up-to-date methods lead to a good solution. Thus
this request is of capital importance for the practising naval
architect, both in developed and developing countries.
Research and testing centres have never enough funds to
carry on the programme they wish to complete. More wide-
spread knowledge of their results could lead to a means of
income not to be neglected.
NEW BOAT TYPES
Odero (Kenya): In Kenya there are about 5,000 fishing vessels
and about 500 pleasure fishing vessels. Whereas practically
all sport fishing vessels are mechanized in one way or another,
only about 50 of the fishing craft use engines. The low figure
of mechanization is probably due to the fact that the fisher-
men have in the past been content with the situation and have
never had any incentive to improve their fishing vessels.
Most of the fishermen are now convinced about the need to
raise the standard of fisheries, which would require properly
built fishing vessels using engines. However, the fishermen are
too poor to pay for such improvements; furthermore the
vessels they have— canoes and sail boats— are not suitable
for engines. Attempts to fit outboards to some of the canoes
have proved on the whole rather clumsy. However, it might
be possible to find a practical way to instal outboards on some
of the present canoes.
Meanwhile, the more well-to-do fishermen arc being per-
suaded to buy the 28 ft (8.5 m) Mwan/a fishing canoe
from Uganda and these are well designed for outboard
installation. The Government is keen to develop the fishing
industry and there are plans for building a boat yard. But
first of all there is a need for boatbuilders and if possible
expert designers.
Impact on new gear needs
Birkhoff (Germany): In consideration of new catching
possibilities by using, for example, electric current or light,
one should first of all utilize all possibilities of the actually
used trawl gear. With the introduction of the pelagic gear,
trawl operations have become far more flexible. Thus, this
gear offers the best possibilities of further development.
Sooner or later, there must be a further reduction of crews.
A high percentage of the crews arc now leaving for other
industries which offer better wages. Consequently the wages
of a single man must be increased to render the work as
attractive as possible. This can only be reached by a further
mechanization or extended automation of the whole catching
operation.
/riff 49. Automation oj 'gear handling
As an example, on a proposed 130 ft (39.6 m) stern trawler,
nearly all gear handling is to be carried out mechanically or
by means of automatic control (see fig 49). Only one man is
needed at the control desk in the wheelhouse and one man on
the geardcck, who controls the automatic work. The only
direct work this man has to do, is to hook the combined
hoisting and shooting tackle into a becket at the codend.
With such a high reduction of manual work on deck, and a
corresponding automation of fish processing and storing,
a crew of six men would be sufficient for a midwater stern
trawler.
On such a vessel, trawls like the "western trawl" as well as
the "bottom trawl", which is used on big European stern
trawlers fishing off the East coast, can be automatically
handled.
;635]
LCNOTH, OVERALL
klNQTM, LOAD NATIftUNt IM
AT MAN OCCK
MFIACIMCNT, TONS
BODY PLAN
Fig 50. Profile and body plan ofPopoffka
/•'fr 57. Bridge deck of Popoffka
Fig 52. Upper deck of Popoffka
f 6361
l:ig 53. Main deck ofPopoffka
Fig 54. Lower deck oj Popoffka
Requirements of new research vessels
Sutherland (USA): There are recurrent complaints about all
existing research ships. Generally speaking, they include
limited operation radius, inadequate laboratory facilities,
accommodations for scientists and crew are too few in
number and lacking in comfort, there is insufficient open deck
area, a lack of manoeuvrability at creep speeds, and inability
to continue operations in high seas states. Research personnel
continually seek better and better tools. Seldom does a group
completely agree on specifications, for each man builds upon
his own experience and has distinct opinions as to the overall
importance of different ship characteristics, and how much he
is willing to sacrifice in other areas in order to meet "real"
requirements.
Research on the popoffka (page 195) suggested that it
might be adopted for the solution of several special ship
problems, especially where the fuel cost and speed to a given
station are of relatively small importance to the success of the
voyage. As a demonstration of popoffka qualities, sketches
of a research vessel designed to meet everyone's requirements
arc presented impossible as such an achievement may be.
The target of this preliminary design was a ship of less than
150ft (45m) in length, to displace not over 1,000 tons, to
have a sea speed of not less than 10 knots, to offer far more in
facilities and comfort than any existing ship of comparable
si/e, and to have the ultimate in manoeuvrability and position-
keeping ability. Further study would be required to assure
that hoped-for qualities can actually be attained.
The hull configuration is scaled-down from Livadia, Minor
variations in hull outline and dimensions could perhaps be
made without penalty, and possibly improvements in the
design could be made, considering that modern testing facilities
and methods, as well as better materials, are available 80-odd
years after Livadia was built.
Fig 50 to 54 inclusive show possible arrangements which
meet the criteria established in the previous section. The
design appears well balanced, but many additional investiga-
tions need still be made. Notable features of the design,
[637;
uncommon in conventional research vessels of similar
displacement or length, include:
simple construction
double-bottom throughout most of length
excellent watertight subdivision
8 ft (2.4 m) deck heights throughout
numerous void spaces adding to reserve buoyancy
unassigned spaces reserved for growth
large sheltered working deck areas
retractable, steerable propulsion units
push-button ship control from bridge or secondary
conning station
manoeuvring and positioning capability
large open well amidships
ramp of suitable dimensions
helicopter platform (or van space)
viewing compartments
aquarium
eight large laboratories, plus appropriate shops
unmatched stability and heavy-lifting capability
boat stowage outboard of main deck areas
comfortable and adequate accommodations
long endurance on station
alleged seakindliness making anti-rolling devices unneces-
sary
Possible propulsion methods
For both propulsion and positioning, it is proposed to use
three 500 hp, electric drive, retractable, steerable right angle
drive units. One of the three identical units would be located
on the ship's centreline near the bow, the other two well off
the centreline at the stern. Provision is made for complete
retraction of the units into the hull, as for instance when a
clear-bottom area is needed in order to avoid fouling gear.
Units could be serviced while in the retracted position. All the
right angle drive units should have infinite speed control,
available by using either DC motors, or AC motors with eddy-
current couplings. All units would be remotely controlled from
the bridge, or the secondary conning station aft, and on
occasion by an automatic pilot. The right angle drive unit
would swing perhaps 70 in (1,780mm) propellers, with or
without Kort nozzles, at about 325 rpm maximum. The
performance to be expected from 500 hp right angle drive
units is detailed by Wanzer on page 407. With infinitely
variable thrust which can be directed at any angle, it is possible
to overcome any conceivable combination of forces imposed
upon the ship by wind, sea, current and operations. So
powered, the ship can maintain any desired position, with any
prescribed heading.
In table 6, it is noted that 1,500 shaft hp has been provided
for a trial speed of 11 knots and service speed of 10 knots.
It is unlikely that amount of power will be required for those
speeds. Actually scaling-down from Livadia^ and her full-scale
trial results, using Froude's well-known Laws of Comparison,
Admiralty coefficients, etc., it appears that this research
vessel version of a small popoffka would require about 610
shaft hp in order to make 10 knots under trial conditions.
Probably the ship would make the stated speeds using only
two of the three right angle drive units, but the third would be
very helpful in meeting positioning requirements, and some-
times during operations it may be advantageous to retract
one unit and "steam" on the other two, without great
sacrifice in speed.
Some may note the failure to assign space to chain lockers
and ground tackle. Adequate space is available for such
assignment, if desired. But ideally, the ship would auto-
matically hover over her assigned anchorage using her pro-
pulsion and positioning units. Signal input to the automatic
control is obtainable from a small taut wire to the bottom.
Trend of the wire, and its tension, would control direction
and amount of thrust of the propulsion units. Using a similar
system, but with different input and with lesser total position-
ing power available, much larger Cuss I maintained position
**for days on end'*, as reported, within a circle of 50 ft (15 m)
radius in 12,000ft (3,700m) of water while engaged in the
preliminary phase of the Mohole project.
Besides tabulating the principal characteristics, complement,
living and laboratory areas for the popoffka research vessels,
tables 6 and 7 offer a convenient comparison of the popoffka
with a catamaran design and two conventional ships.
It is believed that the small popoffka design shows to
advantage in several respects, but it is acknowledged that not
everything one expects to achieve during the early preliminary
design stage of a ship remains attainable at the time a contract
design is completed.
Contract design of the smaller catamaran used in the
comparison is understood to have been completed, though
the ship has not been built. The other two larger ships used in
the comparison have been put into service. Data presented for
the catamaran design, and for the two conventional ships have
been obtained from Traung and Fujinami (1961).
TABLE 6
[General characteristics of research vessels
Popoffka
ft
m
149.5
45.5
136
41.5
88
26.9
71
21.6
4
1.2
17
~5.2
6
1.8
910
1,500
3
11
10
361
0.86
1.55
22.0
Length overall
Length, load waterline
Breadth, moulded
Breadth, at main deck
Design draught .
Drag .
Freeboard, forward
Freeboard, aft
Displacement, tons
Shaft horsepower .
No. of propellers .
Speed, trial knots
Speed, service knots
Displacement/length ratio
Speed/length ratio
Length/beam ratio
Beam/draft ratio .
Atlantis II
Miami
Agor Class
Catamaran
ft m
ft m
ft m
209.74 64
41 43
208.3 63.4
195 59.3
30 39.6
196 60
44 13.4
57.6 17.6
37 11.25
16 1.9
8 2.44
?4 1.27
3 0.9
_ —
1 0.3
21 6.4
17.75 5.4
— —
8 2.44
8.75 2.67
7.25 2.21
2,110
640
1,373
1,400
950
1,100
2
2
1
13
13.5
13
12
13.1
12
284
281
183
0.86
1.15
0.86
4.42
2.26
5.3
2.75
7.2
2.64
[638]
TABLE 7
Space facilities on research vessels
Popoffka
fta ma
170
1,016
170
478
900
430
400
228
488
92
605
1,515
188
6,900
2,920
16
95
16
44
84
40
37
21
45
9
56
141
18
645
272
Living areas
Chief scientist
Other scientists
Master
Officers
Crew .
Scientists* and officers* mess
Crew's mess and lounge
Galley
Washrooms and toilets .
Library
Scientific areas
Laboratories, below main deck
Laboratories, on main deck .
Laboratories, above main deck
Open area above main deck .
Open area on main deck aft .
Complement
Atlantis 11
198
1,094
198
726
914
480
232
216
525
204
458
1,010
1,010
1,208
1,780
18
102
18
68
85
45
22
20
49
19
43
94
94
112
163
Miami
Catamaran
ft3 m3
170
585
180
233
430
415
200
180
510
120
1,160
1,800
2,400
16
55
17
22
40
39
19
17
47
11
108
167
223
Agor Class
ft3
234
672
234
336
252
306
200
240
1,200
22
62
22
31
23
28
19
22
112
28
Scientists
25
17
15
8
Officers
9
5
8
20
Crew .
19
12
14
1
Guest .
57
Total ,
! ! ! 53
34
37
By any other mode of comparison, it also can be shown that
the popoffka offers advantages, if its disadvantages are
acceptable. The same claim can as validly be made for the
catamaran and the conventional hulls.
Popoffkas are a specialized type of ship which might be
useful for special purposes. Unique capabilities are necessary
today in several areas, and one might be willing to sacrifice
other qualities in order to obtain outstanding stability, large
deck areas, the manoeuvrability associated with short length
and unconventional propulsion machinery, and seakindliness.
If reliance can safely be placed in the published professional
literature, quoting some of the most eminent authorities of
the day, popoffka hull seems to offer attractive advantages.
The reliability of the literature can be easily confirmed or
refuted by model tests in a modern laboratory.
New and improved fish products
Danielsen (Switzerland): The demand for protein is
tremendous and increasing year by year. The development in
the USA and Europe is a good example of the increased need
for sophisticated fish products of high quality. This develop-
ment has a paramount influence— and will have in the future—
on the design of fishing boats.
Modern preservation technique is today being extended to
developing countries — Africa, South America, etc. — the
result of this quite obviously will be a sound economical
background for the modernization of the fishing and a change
from smaller boats to larger sea-going vessels.
The fact that, on the near-by fishing grounds, there has
been a tendency to overfishing, so that the fishing nations have
been forced to look for other grounds in distant waters,
together with the development of the processing technique,
will influence the size of the ships, technique used, etc.
This will be of major importance for developing countries.
Another factor not less important is the formation of market
communities and the larger companies need and desire to
diversify and expand. These companies will be thinking only
in economical terms and therefore this will probably influence
the future more than anything else.
For this rapid development, it is very important that fishing
boat operators and naval architects are dynamic and quick
to adapt to v\\ changes in the environment without being
bound to traditions and politics, but are thinking in economical
terms only. The potentials in the sea arc at least one well-
prepared meal from fish to every single individual in the world
once a week. Let this be the objective in the future!
Increasing complexity of needs
Paz-Andrade (Spain): World fisheries are going through a
period of transition towards: a different level of greater
complexity on the extractive side, and greater volume in pro-
duction ; factors triggering off the process are the growing need
for protein foods and the impact of technological innovation
applied to production; the process involves the rehabilitation
ot developing or economically depressed areas, humanitarian
and social responsibility of the prosperous or technologically
developed countries.
The process has as its main objectives:
(1) priority for distant-water fisheries, involving freezing
of catch at sea
(2) full utilization of catch, obviating rejection of species
which could be used for by-products other than
fishmeal, thereby correcting the trend towards mass-
scale and indiscriminate concentration on the latter;
(3) introduction of advanced equipment involving heavy
capital outlay, including mother ships, factory ships,
trawlers, freezers, refrigerated transport
(4) changes in pattern of fisheries involving
• progressive abandonment of the traditional
system whereby one and the same craft does the
fishing and takes catch to port
• operational separation of these two phases, even
in the case of vessels unsuitable for use independ-
ently
[639]
• adoption of practice of operation as a fleet aimed
at
maximum effective fishing time
full utilization of available crew, including
traditional type crews
full utilization of catch aboard ships acting as
collection centres for other boats in fleet
On the above premises, the problem of the development of
the fisheries sector for the future amounts to:
• perfecting the machinery of the technological and
economic development now underway
facilitating the changeover from "dispersed** to
centralized production
coordination of these objectives with conservation of
the biological resource, by enabling crews to have a
wider deployment range and establishing possible
alternatives among the various fishing grounds
reservation, one at a time, of adjacent areas (if
possible, subject to their re-stocking) for fleets of low
tonnage and practicing non-industrial fishing
co-operative organization of family-type fisheries
efficient management of the entire system with a view
to maximizing production on a sustained-yield basis
[640]
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[648]
ADVERTISEMENT SECTION
A stated in the preliminary pages, this advertisement section is included because
it is appreciated that practical, commercial information should be readily
available for all interested parties concerning fishing vessels, fishing gear and equip-
ment that can be procured from various sources for the betterment of fishing practices.
The prime object of the Department of Fisheries, Food and Agriculture
Organization (United Nations) in organizing these Fishing Boats Congresses is to
bring together the leading experts from all major fishing countries and fishery
administrators in order to give and exchange information calculated to improve the
technical capacity and efficiency of the fishing industries in their territories.
To supplement that knowledge this section is designed to give commercial informa-
tion of where and how fishing craft of various types can be most satisfactorily secured
or built, reliable engines bought and particular gear and equipment purchased. The
co-operation of the firms who thus advertise, renders a double service: in addition to
giving information about their wares, their support enables this book to be produced
at a lower figure than would otherwise be possible.
Therefore the publishers of this book bespeak for these firms such good will and
support as can be given by appreciative fishermen and operators in the expanding
industries of the countries of Asia, Africa, the Pacific, South America, North America
and European areas.
Fishing News (Books) Ltd.
110 Fleet Street, London, E.C.4.
An index of advertisements included in this section appears overleaf
Index to Advertisements
page
nglo Belgian Cy xxxiv
peldoornse Nettenfabriek von Zeppelin & Co. N.V. . xxiv
TCtic Norsenet Ltd xxxiii
>stilleros Unidos del Pacifko, S.A xviii
^tlas-Elektronik Bremen (Fried. Krupp), . . xiii
endix international Operations .... xxiii
con Societe Anonyme des Ateliers, Le . . . xxxvi
crnt Ivcrsen & S0n A/S ..... xxxiv
loctubc Controls Ltd xxvi
lount Marine Corporation xiv
rown, S.G. Ltd.. ...... xxi
russelle A. S.p.r.l., Ateliers de Construction . . xxxi
'hantiers et Ateliers de la Perricrc, . . . xxii
oehrane & Sons Ltd. ...... xxxiii
unis, W. R. Ltd. ...... xxxvii
>ecca Navigator Co. Ltd., The .... viii
isheries Dept. F.A.O. . . . . . . xl, xli
ishing News (Books) Ltd. .... xxxix, xlii
ishing News International xxxviii
rick-Barbieri, S.p.A. ...... xii
lidrostal S.A. ....... xxvii
loppe, Hans ....... xxx
lundested Motorfabrik, A/S .... vi
lydraulik Brattvaag, A/S xvi
C.I. Fibres Ltd xi
onkopings Motorfabrik, A.B. . . . xxix
Lelvin Hughes (a Division of Smiths Industries Ltd.) . i
Loden Electronics Co. Ltd xxxv
lOrneuburg Shipyard A.G. ..... xxxi
Lristinsson, G.E. & Dr. David J. Doust . . xxxvii
arsen, Hans L xxxvi
-ister Blackstone Marine Ltd xxxv
page
Marine Construction & Design Co. . . . ii, iii
Marinovich Trawl Co. ...... xxviii
Mewes & von Eitzen, J. H xxx
Miho Shipyard Co. Ltd. ..... vii
Miller, James N. & Sons Ltd xxxv
Mirrlecs National Ltd. ...... xvii
Modern Wheel Drive Ltd vii
Morishita Fishing Net Mfg. Co. Ltd. . . . xviii
Moteurs Baudouin ..... xxx
Motorcn-Wcrkc Mannheim A.G xxv
Mustad, O. & Son xxxvii
Nippon Gyomo Sengu Kaisha Ltd., The . . xxii
Nordisk Aluminiumindustri, A/S .... xxxiv
N0rskov Laursen, Maskinfabrik .... xxxii
Nuova San Giorgio s.p.a. ..... xxviii
Nyqvist & Holm A.B. (NOHAB) .... xx
Outboard Marine (F.vinrude). .... v
Outboard Marine (Johnson) ix
Prout, G. & Sons Ltd. ...... xxxvi
Rickmers Werft ....... xxix
Rolls-Royce Ltd xix
"Samifi", (Soc.P.A/. Macchinari Impianti Frigoriferi
Industrial!) ....... xxxiv
Simonscn Radio A/S xv
Sorefamc de Angola S.A.R.L xxiv
Strojexport, (SKODA Marine Engines) ... x
Taiyo Musen Co. Ltd xxxii
Tyrrell, John & Sons Ltd. ..... xxxvii
Wichmann Motorfabrikk A/S .... xxxii
Wykcham, W. & Co. Ltd xxvi
Zahnraderfabrik Renk A.G. (Augsburg) iv
NEW RADARS
From Kelvin Hughes
Both are fully transistorised and represent logical developments—
i/vith additional features—of the highly successful KH radars 17 & 17R,
3f which well over 3000 are at sea.
L7/9orl2
jreat versatility
_ow price
Jigh Definition j—24 miles
L9/9orl2
Vliddle&Distant
/Vater Trawlers
ligh Definition £-48 miles
Reliability
An improved (3kW) transmitter— with
excellent short range characteristics —
operates a 9 " or 1 2 " display, or a com-
bination of the 2 with either as master.
Scanner: either 4tt. 6ft. 7.5ft. or 10ft.
This versatility enables the owners of
coastal craft to PICK and choose according
to their specific needs. Included as stand-
ard : Variable range marxer ; new stable
local oscillator; auto alignment to Ship's
Head-up display (and North-up with
compass converter).
A new (25kW) transmitter combines, for
the first time, the necessary power for
long range performance with the out-
standing high definition at very short
ranges hitherto only associated with spec-
ialised river Radar. 9", 12" or dual dis-
play. 7* 5ft. or 1 0ft. scanner recommended.
The Performance plus Versatility (as
above) of Series 1 9 add up to the right
equipment for any individual oceangoer.
Standard features : as for 1 7, plus Trans-
mitter and Receiver monitors; three
matched pulse lengths, p.r.f.'s and auto-
switched receiver band widths.
Samples from the production line of all
new equipment are put through KH tests
which in many cases are more stringent
than the relative Ministry specifications.
These include dry heat, damp heat low
temperature, driving rain, vibration, corro-
sion, mould growth and packaging. Be-
hind this is the fact that every item is
engineered to the high standard for which
Kelvin Hughes is rightly famous — backed
by world-wide service.
[ELVIN HUGHES KNOW THE SEA FROM SHORE TO SHORE — FROM SURFACE TO SEA BED
KELVIN HUGHES
St. Clare House, Minories, London, E.C.3.
Royal 8741 Grams— Cables : Marinst London EC3
DIVISION OF SMITHS INDUSTRIES LIMITED Telex : 25368
Index to Advertisements
Anglo Belgian Cy
Apeldoornse Nettenfabriek von Zeppelin & Co.
Arctic Norsenet Ltd. .....
Astilleros Unidos del Pacifico, S.A
Atlas-Elektronik Bremen (Fried. Krupp). .
Bendix International Operations ...
Beon Societe Anonyme des Ateliers, Lc . .
Bcrnt Iversen & S0n A/S
Bloctube Controls Ltd
Blount Marine Corporation
Brown, S.G. Ltd
Brussclle A. S.p.r.l., Ateliers de Construction .
Chantiers et Ateliers de la Perriere. . .
Cochrane & Sons Ltd. .....
Cunis, W. R. Ltd
Decca Navigator Co. Ltd., The ...
Fisheries Dept. F.A.O
Fishing News (Books) Ltd. ....
Fishing News International ....
Frick-Barbieri, S.p.A
Hidrostal S.A
Hoppe, Hans
Hundested Motorfabrik, A/S ...
Hydraulik Brattvaag, A/S
I.C.I. Fibres Ltd
Jonkopings Motorfabrik, A.B
Kelvin Hughes (a Division of Smiths Industries
Koden Electronics Co. Ltd. ....
Korneuburg Shipyard A.G
Kristinsson, G.E. & Dr. David J. Doust .
Larsen, Hans L
Lister Blackstone Marine Ltd. ...
xxxv
N.V. . xxiv
. xxxiii
xviii
. xiii
. xxiii
. xxxvi
xxxiv
xxvi
xiv
xxi
. xxxi
. xxii
. xxxiii
xxxvii
. viii
xl, xli
xxxix, xlii
. xxxviii
xii
xxvii
xxx
. vi
xvi
xi
xxix
Ltd.) . i
. xxxv
xxxi
. xxxvii
xxxvi
. xxxv
page
Marine Construction & Design Co. ii, iii
Marinovich Trawl Co. ...... xxviii
Mewes & von Eitzen, J. H. . . . . . xxx
Miho Shipyard Co. Ltd vii
Miller, James N. & Sons Ltd. .... xxxv
Mirrlecs National Ltd. ...... xvii
Modern Wheel Drive Ltd. . . . . . vii
Morishita Fishing Net Mfg. Co. Ltd. . . . xviii
Moteurs Baudouin ..... xxx
Motoren-Werke Mannheim A.G. .... xxv
Mustad, O. & Son ...... xxxvii
Nippon Gyomo Sengu Kaisha Ltd., The . . xxii
Nordisk Aluminiumindustri, A/S .... xxxiv
N0rskov Laursen, Maskinfabrik .... xxxii
Nuova San Giorgio s.p.a. ..... xxviii
Nyqvist & Holm A.B. (NOHAB) .... xx
Outboard Marine (Evinrude) v
Outboard Marine (Johnson) ..... ix
Prout, G. & Sons Ltd xxxvi
Rickmers Werft xxix
Rolls-Royce Ltd xix
"Samifi", (Soc.P.Az. Macchinari Impianti Frigoriferi
Industrial!) ....... xxxiv
Simonsen Radio A/S ...... xv
Sorcfame de Angola S.A.R.L. . . . . xxiv
Strojexport, (SKODA Marine Engines) ... x
Taiyo Musen Co. Ltd. ...... xxxii
Tyrrell, John & Sons Ltd xxxvii
Wichmann Motorfabrikk A/S .... xxxii
Wykeham, W. & Co. Ltd xxvi
Zahnriiderfabrik Renk A.G. (Augsburg) iv
ADVERTISEMENT SECTION
NEW RADARS
From Kelvin Hughes
Both are fully transistorised and represent logical developments—
with additional features— of the highly successful KH radars 17 & 17R,
of which well over 3000 are at sea.
17/9 or 12
Great versatility
Low price
High Definition £-24 miles
19/9 or 12
Middle&Distant
Water Trawlers
High Definition i-48 miles
Reliability
An improved (3kW) transmitter—with
excellent short range characteristics-
operates a 9 " or 1 2 " display, or a com-
bination of the 2 with either as master.
Scanner: either 4ft. 6ft. 7.bft. or 10ft.
This versatility enables the owners of
coastal cratt to picK and choose according
to their specific needs. Included as stand-
ard : Variable range marker; new stable
local oscillator; auto alignment to Ship's
Head* up display (and North-up with
compass converter).
A new (25kW) transmitter combines, for
the first time, the necessary power for
long range performance with the out-
standing high definition at very short
ranges hitherto only associated with spec-
ialised river Radar. 9". 12" or dual dis-
play. 7- 5ft. or 1 0ft. scanner recommended.
The Performance plus Versatility (as
above) of Series 1 9 add up to the right
equipment for any individual oceangoer.
Standard features : as for 1 1, plus Trans-
mitter and Receiver monitors; three
matched pulse lengths, p.r.f/s and auto-
switched receiver band widths.
Samples from the production line of all
new equipment are put through KH tests
which in many cases are more stringent
than the relative Ministry specifications.
These include dry heat, damp heat low
temperature, driving rain, vibration, corro-
sion, mould growth and packaging. Be-
hind this is the fact that every item is
engineered to the high standard for which
Kelvin Hughes is rightly famous — backed
by world-wide service.
KELVIN HUGHES KNOW THE SEA FROM SHORE TO SHORE — FROM SURFACE TO SEA BED
KELVIN HUGHES
St. Clare House, Minories, London, E.C.3.
Royal 8741 Grams— Cables : Marinst London ECS
A DIVISION OF SMITHS INDUSTRIES LIMITED Telex : 25368
URETIC POWER BLOCK— the patented net hauling device that has revolutionised STIIL PURSE SEINERS— designed by Marco in various typei from 12 to 48 mete
urse seining In more than 25 countries. This Marco /Rapp model, manufactured under l.o.a., for specific fisheries. Design* are developed for maximum effectiveness an t
sense in Norway, has a 31-inch sheave and is shown in use on a Norwegian vessel. A
*ries of models, with shvove sizes from 12 to 42 inches, have been developed through
;tual fishing experience to moot local operating conditions. Seines from the smallest to the
rgest are handled.
fishing grounds, and for a high rate of multiple construction with economical use of lo<
facilities and labor. The examples here are 22-meter vessels built in Chile by Marco Chiler
S.A.I. More than 500 vessels have been built by Marco and its licensees.
ARCO - PIONEERING NEW EQUIPMENT AND SERVICES
The wide scope of Marco services is based on direct
experience in many technical fields. Personnel include
marine and mechanical engineers, naval architects, fleet
managers, processing plant designers and managers, civil
engineers, master fishermen, spotter-aircraft pilots, refrig-
eration specialists, project managers. These personnel have
one area of experience in common: a Jirst-luiml knowledge
of fishing operations.
The various areas of Marco's experience are made available
through the Fisheries Development Division, in the form
of economic and resource surveys, feasibility studies, con-
sultation, design, construction, management and manage-
ment assistance. Inquiries are invited concerning how these
capabilities may be applied to comprehensive projects in
newly-developing fisheries, or to special problems in
advanced fisheries.
ARCO PISH PUMP— the patented, submersible design creates a revolution in
ih pumping. Priming is eliminated; hose is light and fully collapsible, as seen here on
luth African seiner. Pump connects to most Puretic Power Block hydraulic systems. This
vention is the outgrowth of experience in many different fisheries, with prototype develop-
ent being carried out in rigorous day-to-day fishing. Capacity of largest model exceeds
X) tons per hour.
DESIGN AND CONSTRUCTION OF PROCESSING PLANTS-from initial studies throuj
final start-up and personnel training. This plant for tuna freezing and canning, at
anchovy reduction, is a Marco protect completed under contract to the Chiloan Govern me
agency CORFO. Planning included full coordination of fishing effort and shore faciliti«
such as establishing a fleet, selecting fishing gear, and setting-up maintenance and personn
programs.
HYDRAULIC DECK MACHINERY- complete high-pressure systems for fishing, cargo
handling, and oceanography, including full responsibility for all pumping and
control functions. This Marco winch, shown on a Faroese seiner, is one of a teries for
seine, trawl and combination service. New designs are evolved from accumulated fishing
experience, providing increased power, speed and convenience.
lARCO MANUFACTURING LICENS
Scope of respective manufacturing program it Indicated. In add
thote licensees, Marco distributors are established in most major
centtrt off the world.
NORTHERN EUROPE — Marco / Rapp hydraulic
machinery
RAPP FABRIKKER A/S
Nyholmen
Pottbokt 145
Bodoe, Norway
Telephone: 21 091
Cables: RAPPFABRIK
Telex: 4087
FRANCE — Marco hydraulic deck machinery
AYELLO & PILS S.A.
5, Rue Carnot
Boite Postale 1-016
Dunkerque
Telephone: 66.52.00
Cables: AYELLOFILETS
SPAIN — Marco hydraulic deck machinery
JUNASA
Julio N. Santho
Apartado 582
Vigo
Telephone: 15769
Cables: JUNASA
FOR MODERN FISHERIES
IRINE CONSTRUCTION * DESIGN CO.
2300 W. Commodore Way, Seattle, Washington 98199, U.S.A.
Cables: MARCO Telephone ATwater 3-2680
Telex; 32-298
Area Code 206
SOUTH AFRICA— Marco fishing vessels
CAPETEX ENGINEERING WORKS (PTY.) LTD.
P.O. Box 3130
Cape Town
Telephone: 53-1386
Cables: COLLIN5TEX
Telex: C-764B
HYDRAULIC MACHINERY • PURETIC POWER BLOCKS •
SPECIALIZED GEAR FOR FISHING AND FISHERIES RESEARCH
• NEW VESSEL DESIGN AND CONSTRUCTION • DESIGN
AND MODIFICATION WORK FOR VESSEL CONVERSIONS
• ENGINEERING OF INTEGRATED FISHERIES FACILITIES
COASTAL STERN TRAWLERS— holders of many production records for hake and
•hrlmp. GRINGO, 22 meter* l.o.a., produced 9700 tons of hake in 12 months. Designed and
built by Marco, the vessel hat on hydraulic deck machinery system of unusual refinement
and efficiency. Trawl drum, combination winch and auxilliary winches enable the crew of
only six men to perform all net-handling operations with ease.
EASTERN CANADA— Marco hydraulic deck machi
PEACOCK BROTHERS, LTD.
P.O. Box 1040
Montreal, Quebec, Canada
PERU — Marco fishing vessels
FABRICACIONES METALICAS S.A.
Catilla 307
Calloo
Telephone: (514) 366-!
Telephone: 93202
Cablet: FABRIMET
PERU — Marco hydraulic deck machinery
MARCO PERUANA S.A.
Apartado 41 5
Callao
CHILE— Marco fishing vessels
MARCO CHILENA S.A.I.
Clasif leader 116
Santiago
Telephone: 93970
Cables: MARCO
Telex: 0207
Telephone: 66835
Cable*: MARCO
Telex: 299
FISHING BOATS OF THE WORLD: 3
RENK TWIN GEAR UNITS
MtENK
RENK twin gear units for econo-
mical Installations on modern
fishing vessels. Multi engine
drive with single output, each engine
disengageable by means of
built-in multi disc clutches
Reliable quick manoeuvering
Economical operation
Naval adaptability
Know how in RENK design
ZAHNRADERFABRIK RENK AKTIEN G ES E LLS CH AFT AU GS BURG
Mvl
ADVERTISEMENT SECTION
Want an outboard \<i fun with an inboard'sgo?
Fit an Evinrude Stern-Drive.
The new Erinrude Stern-Drire can make any boat (your bout)
pet with it. These e.ir lustre l\r in rude features tell win':
Electric power nhift - Cires smoother control than old-
f axh it med mechanical shifts.
Electric power lift - I'rorides dash-board (fingertip) control
to raise the lower unit a full 7.5°.
Quiet mount ttrtttem - Offers rubber mounts strategically
located to isolate uiolor and outdrive for greater balance and
t/utel. } on pet nia.riinuin performance irifh minimum ribratiou.
ItiHtfiltfition pnckuge include*: pu.sh~hutton. remote control.
Dash panel and itixtruments consisting of ammeter, oil lipht.
le/uperalure //if///, ignition switch, tilt switch ami tachometer
for single or dual installations and all mounting hardware,
.tlso throttle and electrical cables, propeller.
In addition, you hare the assurance that corner from owning
an Evinrude - (>0 years of experience plus holder of the
world's speed record.
See your local Krinrude Distributor and choose your Stern-
Drive from his selection of 5 different models - WJ. /I'O, /.>->.
/ S,5 and. 200 ///'. Karh one has a 2-year warranty.
the power of experience * ~i^?C wINRUDE
For complete information, wrile to; Outhonnl Marine Bruges.
Belgium or Nassau. Bahamas.
Water Cods" can male a biff splash with any of these mapni'Jfrent Stern-Drires.
[v]
FISHING BOATS OF THE WORLD: 3
HUNDESTED
ENGINES
H.M.F. semi-diesel engines ranging from 12-250 b.h.p. are
ideally suited for all types of fishing vessels, tugs and
coasters. These engines are heavily built, slow running,
giving the owner absolute reliability and economies in
running and maintenance and are easily operated,
the ideal uncomplicated engine, easy service. All engines
are fitted with our simple and robust variable pitch
propeller unit giving the owner maximum efficiency
under all conditions.
VARIABLE PITCH
PROPELLER
Semi-fix propeller with variable pitch when the ship is
on a slipway. Can only be used in connection with a
reversing gear.
Our new hydraulic reversing mechanism is the simplest
design existing. Type FR-H
Closed fully reversible propeller mechanism, manually
operated with built-in thrust bearing. Type FR
Open fully reversible propeller mechanism without thrust
bearing, type FROA. The pitch can be adjusted from the
wheel house or the engine room, when the propeller
shaft is rotating.
Propeller with variable pitch when the shaft is stopped,
type AIS. Can only be used in connection with a reversing
gear.
WE SPECIALISE IN SUPPLYING PROPELLER UNITS FOR ALL DUTIES AND TO ANY TYPE OF MARINE ENGINE
Manufacturers of our propeller units for the European Market, are Messrs. Lips Propeller Works, Drunen, Holland.
Manufacturers of our propeller units for U.K. Market are Messrs. Propulsion Ltd., Propulsion Works, Duchess Street, Shaw Nr. Oldham.
Manufacturers of our propeller units for Brazil and other Latin American countries are Messrs. Cofama S.A., Equipamentos Industrials,
Rua Rego Freitas 354-8u Andar, Conj. 85, Sao Paulo.
A/S HUNDESTED MOTOR & PROPELLER FABRIK
Cables: Propelmotor HUNDESTED - DENMARK Telex: 5594 Telephone: 117
[Vi]
ADVERTISEMENT SECTION
All kinds of
WORLD
WIDE
SERVICE
Fishing Boats, Coastal Cargos,
Tug Boats and Oil Tankers
TENYO-MARU
Training Ship. 400 G. T.
for Shimonoseki Fishing University J
with Unigan stern Trawling gear
MfflO SHIPYARD CO., LTD.
HEAD OFFICE : MIHO, SHIMIZU, SHIZUOKA PREF., JAPAN
BRANCH : ROOM No, 705, TOKYO TATEMONO BLDG., CHUO-KU, TOKYO, JAPAN
ALL TYPES OF TRANSMISSION FOR FISHING VESSELS
Including Controllable Pitch Propellers
One of the well-known HINDMARCH/
MWD oil-operated reverse-reduction gear-
boxes. The type shown has two speeds.
Eight gearboxes of this design were sup-
plied for Leslie Fishing Go's Aberdeen
fleet, with Lister-Blackstone engines.
HINDMARCH/MWD reduction gearbox
with two generator drives. Twelve
Polish distant-water trawlers have this
gearbox with Mirrlees-National engines.
HINDMARCH/MWD twin-input single-
output reduction gear for Ruston-engined
distant water trawler ROSS RENOWN.
The Ross Group has many types of Modern
Wheel Drive installations.
MODERN WHEEL DRIVE LTD.
Auociated with
T. HINDMARCH * CO. LTD. and OIL-OPERATED GEARS t TRANSMISSIONS LTD.
SLOUGH, BUCKS. TELEPHONE: SLOUGH 25435 CABLES: OILOPRATED SLOUGH
HINDMARCH/BERG controllable pitch pro-
peller with hydraulic control, as supplied
to European, Canadian and other fishing
fleets of the world.
[vii]
FISHING BOATS OF THE WORLD: 3
for more profitable fishing...
DECCA
The Dacca Navigator Mark 12 Multipulse
extends Decca coverage and gives more accurate fixes at the longer ranges.
A chain selector switch is conveniently placed for inter-chain fixing.
Dacca Track Plotter
Grounds, wrecks and fastenings can be plotted in advance and planned fishing
can be systematically carried out. Set and drift can be judged at a glance.
Arkas Autopilot
reduces passage time and fuel consumption. Releases that extra man for work on deck.
The Decca Navigator Company Limited • London
[ viii ]
ADVERTISEMENT SECTION
Introducing the newest concept in marine power
Johnson Stern-Drives.
The new Johnson StenvDrivcs are loaded with all
the features for which others charge extra plus some
you can't huy anywhere dashboard control, electric
powershift and electric power lift are standard equip*
ment / The new Johnson Stern-Drives give you
smoother performance with a lot less vibration. Here
is why: only the new Johnson Stern-Drives feature
an exclusive rubber mounting system that isolates both
the motor and outdrive* Applies all the thrust to the
floor of the boat where it should be.
INSTALLATION PACKAGE INCLUDES : single
lever shift remote control. Dash panel and instruments
consisting of ammeter, oil light, temperature light,
ignition switch, tilt switch and tachometer for single
or dual installations and all mounting hardware. Also
throttle and electrical cables, propeller.
You can choose from a range of 5 dependable Stern-
Drives from 90 to 200 HP with 4, 6 or 8 cylinders.
Each one comes with a 2-year warranty.
To get the newest concept in marine power plus the
know-how that only Johnson can provide, see your
Johnson dealer and select the new Stern-Drive which
best fits your boat.
•Johnson
is first in dependability
For complete information, write to: Outboard Marine
Bruges, Belgium or Nassau, Bahamas.
90 HP
Any of the.se dependable Stern-Drives can give you real boating pleasure.
IX
FISHING BOATS OF THE WORLD: 3
SKODR
i GOOD CATCH WITH
KODA DIESEL
CODA diesel engines, backed by more than 50 years' experience in design and production, are
e best power for all types of fishing vessels.
ie SKODA range, available in both naturally aspirated and turbo-charged versions from 30 up to
rO bhp, offers unequalled reliability, high economy, easy maintenance and extra long life.
v
pays to standardise on SKODA Diesels for propulsion and auxiliary applications!
jll information from :
SJROJEXPORT
DIESEL ENGINE DIVISION, PRAHA I, P.O.B. 662, CZECHOSLOVAK I A
Cobfo: Stroj«xdi«Ml Prahm T«/ex: Praha 171.208
EPRESENTED ALL OVER THE WORLD
[x]
ADVERTISEMENT SECTION
ULSTRON
holds
the big catches
ULSTRON in fishing gear is strong, light,
long lasting, holds bigger catches,
requires less maintenance and saves money.
If your problem involves any aspect of
fishing nets and ropes, find out about ULSTRON by
getting in touch with your usual supplier or
ICI FIBRES LIMITED, INDUSTRIAL USES DEPARTMENT,
HOOKSTONE ROAD, HARROGATE, YORKSHIRE
HARROGATE 68021
ULSTRON u a Repaired Trade Mark of Id
ICI Fibres
work for industry
XI
FISHING BOATS OF THE WORLD: 3
FRICK BARBIERI
Factory management :
Castelmaggmre (Bologna), Italy
Telephone 711.155
Cable address :
Fnck-Barbieri (Bologna) Italy
P.O. Box 128
BARBIERI
FRICK-BARBIERI REFRIGERATION ON THE "ANNUNZIATA C"*
4f By kind permission of the trawler owners, Messrs. CefalCi Bros., Palermo, Italy.
[xii]
ADVERTISEMENT SECTION
Clear view
with ATLAS Radar
Equipment
The outstanding reliability
of ATLAS Radar Equipment
and the efficiency
of the Service Organisation
guarantee
a successful catching trip.
KRUPP
The stern trawler
"Hans Pickenpack" was equipped
with the ATLAS Echosounders
NETZSONDE, FISCHFINDER and
MONOTYPE,
and with 2 Radars "ATLAS 1555"
FRIED. KRUPP
ATLAS-ELEKTRONIK BREMEN
[ xiii ]
FISHING BOATS OF THE WORLD: 3
NARRAGANSETT
World's First Automated Stern Trawler
Launched early in 1963, this 83-ft. all-
steel vessel is the world's largest engine-
in-stern, belt-driven trawler. Designed
and built by the Blount Marine Cor-
poration in the United States, she
features a special "Trawlmatic" winch,
which forms the basis of the amazing
automated trawl handling system.
From a console aft of the wheel-house
overlooking the deck, a single operator
can control not only the vessel itself,
but the entire trawling system.
Built entirely by private U.S. capital . . . this vessel, with her automated
trawl mechanism, is believed to hold the world's net-hauling speed record.
The "Narragansett" can haul and
dump in only 2£ minutes after doors
are secured. Most European and
American trawlers consume 7 minutes
or more each way. Another outstanding
feature of this vessel is her patented
Hustad Controllable Pitch Propeller,
which permits shifting from full power
ahead to full astern in 3!- seconds.
Blount-built commercial vessels of all
types are in service throughout the
world. Before you order your next
boat, consult the shipbuilder that has
the skill, facilities and imagination to
design and build a "Narragansett1'.
Write for illustrated brochure describing this unique vessel in detail.
BLOUNT MARINE CORP
NAVAL ARCHITECTS
BUILDERS OF STEEL VESSELS
BOX 360, WARREN, RHODE ISLAND, U.S
xiv
ADVERTISEMENT SECTION
«Our Simrad Sounder told us exactly where to set our gear.
Just like fishermen aboard 13.000 other boats in 40 countries,
we rely on our Simrad to find the fish.
Simply because it tells us more about single fish, fish-schools
and bottom conditions than any other fish-finder. Look at any
Simrad recording and see for yourself the accurate details.
You can't have better proof».
For bigger catches, higher income, a Simrad Fish Finder is the
answer. There is a range of 26 Simrad Echo Sounders and 6
fully-automatic Sonars to choose from. Designed for all types
of vessels and fisheries. Produced by the world's leading manu-
facturer of modern fish finding equipment.
EH SUPER SOUNDER
Today's most advanced sounder for
any fishery. Effective White Line on
all trawling depths. 8 ranges. /I
J^Maximum 860 fathoms. All voltages. / ,
MASTER SOUNDER
Specially designed (or open
.boats. Watertight.
6 ranges. Maximum 600 fathoms.
All voltages
-SKIPPER SOUNDER
Powerful and easy to operate
Effective White Line.
6 ranges. Maximum 600 fathoms.
, All voltages
COMPACT SOUNDER
Fully transistorized echo sounder
for small fishing vessels
'Maximum 200 fathoms 12. S»4. volts
You find more fish faster with
For further information apply to your local Simrad Distributor, or direct to Simonsen Radio A.S., Ensjoveien 18, Oslo, Norway
[XV]
FISHING BOATS OF THE WORLD: 3
HYDRAULIK
LOW PRESSURE DECK MACHINERY
the modern equipment for modern
fishing vessels of any type and size.
Our HYDRAULIK Deck Machinery was originally
designed for fishing crafts, and since 1938 more
than 10.000 HYDRAULIK installations are delivered
through out the world.
At present we deliver trawlwinches, long line hau-
lers, cargowinches and windlasses for stern traw-
lers, tequri-vessels, conventional trawlers, herring
drifters and purse seiners in Japan, Korea, India,
Pakistan, Malaya, South Africa, South America,
Australia, U. S. A., Canada, Portugal, Spain, Italy,
France, Germany, Holland, U. K., Ireland, Faroe Is-
lands, Denmark, Iceland, Sweden and Norway.
FROM OUR MANUFACTURING PROGRAM:
Trawlwinches, long line haulers, cargo winches,
windlasses, warping winches, mooring-winches
(also automatic selftensioning), topping- and sj
ing winches, tug winches, oceanographic
and level luffing deck cranes.
Dutch trawler -Cornells den Dulk» havinp
HYDRAULIK trawlwinch and windlass.
. ., Sea Research Vessel
anS Stern TTa"wW. ~ 1)500 G R. T. *': -
HYDRAULIK trawlwinch, windlass, oceanogra-
phic winches.
20 countries throu
-Taiyo Maru 62» (and 12 sister ships). Japanese
stern trawlers — 2000 G. R. T.
HYDRAULIK trawlwinch, windlass, cargo-
winches.
ADVERTISEMENT SECTION
MIRRLEES NATIONAL
ON-THE-SPOT SERVICE-MORE HOURS AT SEA
Mirrlees provide service where it counts
most : at the dock-side. Our service depots,
staffed by skilled engineers and stocked
with a full range of spares, are strategically
located throughout Britain and overseas.
M irrlees service provides you with effective
insurance against long and costly turn-
rounds.'Please contact us for full details of
our wide range of medium-speed engines
(up to 8,000 h.p.), and our comprehensive
after-sales support. Depots in the U.K. at
Aberdeen, Fleetwood, Glasgow, Gnmsby,
Hull, London, Milford Haven and North
Shields.
HAWKER SIDDELEY
MIRRLEES DIESELS
Hawker Siddeley Group supplies mechanical, electrical and aerospace capital equipment with world-wide sales and service.
MIRRLEES NATIONAL LTD.,
HAZEL GROVE, STOCKPORT,
CHESHIRE-Tcl: Stepping Hill 1000
[ xvii ]
FISHING BOATS OF THE WORLD: 3
ASTILLEROS UNIDOS DEL PACIFICO, S. A,
Tomas de Rueda Jr. General Manager.
The Astilleros Unidos del Pacifico, S.A., of Estero
del Infiernillo, Apartado Postal 80, Mazatldn,
Sinaloa, Mexico, have up to now built 350 fishing
boats.
Specialists in the building of all types of vessels, in
steel and wood. General repairs to fishing boats of all
kinds.
Over fifteen years experience in shipbuilding.
UNDER CONSTRUCTION:
3 boats for Chile
10 boats for Central America
6 boats for Venezuela
7 boats for Brazil
COPASA I Tuna Purse Seiner
Shipowners: Conserves del Pacifico, S.A., Ensenada, B.C.
WE INVITE SHIPOWNERS EVERYWHERE TO WRITE TO US FOR INFORMATION
[ xviii ]
ADVERTISEMENT SECTION
PHILIPPINES
INDIA
EIRE
SCOTLAND
"Rolls-Royce Diesels"
means
reliable power
in any language
under the sun
MOROCCO
ICELAND
Power for the World's fishing boats. Rugged, eager power that meets up with the fish
sooner, then home with the haul lickety-spit. Dependable power, rarin' to go— that's Rolls-
Royce Diesels, Pacemakers, and spacemakers, these engines need less room on board
than others, and that leaves more room for fish. With all that and low running costs you've
also said 'good fishing1 in any language when you've said 'Rolls-Royce Diesels'.
ROLLS-ROYCE LTD SHREWSBURY EN6LAND Til: 52282 Tatox: 3571 Brams: ROYCAR SHREWSBURY - DIESEL AND PETROL ENGINES • AERO EN6INES • MOTOR CARS • INDUSTRIAL 8A5 TURBINES - ROCKET MOTORS • NUCLEAR PROPULSION
P43I6
Diesels
FISHING BOATS OF THE WORLD: 3
They
also
chose .
NOHAB POLAR
Swedish fisherman Gunnar Karlsson and his fellow-owner, ex-World Heavy-
weight Boxing Champion Ingemar Johansson (right) .inspecting the 12-cyl.
NOHAB POLAR-F for their purse seiner "Ingo". This V-engine develops up
to 1800 bhp at 750 rpm but is, at the same time, extremely compact. In
common with the in-line engine (below), it is fitted with a hydraulic governor
which is regulated from the bridge through a pneumatic controf system.
Centrifugal filters and thermostat for the lubricating oil extend the intervals
between oil changes and overhauls.
Fill in and send us the coupon below if you would like more details about
the NOHAB POLAR-F.
Send me broahxure about tlie NOHAB POI*AR-F
Name
Address
I am most interested in
[J V-engine 1000—2400 bhp
Q In-line engine 300 — 900 bhp
Convenient working height for
valve adjustment, etc.
Centrifugal filters keep the lub-
ricating oil particularly clean.
DIESEL DIVISION
NOHAB
TROLLH&TTAN SWEDEN
Telephone 18000 Cables NOHAB Telex 5284
The original manufacturer of PO LA R engines
"Ingo" with the engine shown above
will be able to land 350 tons.
The in-line engine is enough for
power requirements up to 900 bhp.
[XX]
ADVERTISEMENT SECTION
Complete Control by
HAWKER SIDDELEY
The most efficient fishing
fleets in the World fit
Navigational Equipment
by S. G. Brown.
S. G. BROWN LTD
WATFORD • ENGLAND
Telephone: Watford 27241
Telex: 23408 • Cables: Sidbrownix Watford
Hawker Siddeley Group supplies mechanical, electrical and
aerospace capital equipment with world-wide sales and service.
[xxi]
FISHING BOATS OF THE WORLD: 3
Chantiers et Ateliers de LA PERRIERE
SHIPBUILDING
• Specialists in fishing vessel building:
Stern trawlers 23-27-33-37 metres O.A.
Classics trawlers
• Small Passenger Ships
• Tugs
• Harbour Craft, Etc.
All Ships up to 50 metres overall
SEAWORTHY
SOUND CONSTRUCTION
PERFECT FINISH
PortdePeche LORIENT FRANCE
Tel.: 64-16-50
"CEZEMBRE"
Stcrntrawler 33 metres overall
wFishing Nets and Boat Equipment
Outline of Nichimo's Enterprise
Manufactures and sells fishing nets and equipment.
Plans fisheries and conducts studies on fishes for
such projects.
0 Provides fishing know-how.
O Acts as consultants for building modern fishing vessels.
Supplies all kinds of ship's fittings-mainly for fishing
vessels.
Supplies steel products mainly for shipbuilding, fuel for
fishing vessels and petroleum products.
Assists international organizations and government
agencies of many countries for the development of
the world's fishing industry.
NjGHIMO.
THE NIPPON GYOMO SENGU KAISHA LTD.
Central P.O.Box 243, Tokyo, Japan / Cable Address: "GYOMO TOKYO"
xxii ]
ADVERTISEMENT SECTION
You can't hire a better helmsman than the Bendix Model 14.
On board your fishing boat, the Bendix Model 14 Auto-
pilot adds to your profits by saving fuel. And adds to your
fishing time by steering a straighter, more direct course,
A flip of the switch turns the autopilot on. Then you
put the boat on the desired course and engage the electri-
cally operated clutch. The autopilot takes over and holds
your true course even better than the most experienced
helmsman. Without attention, for hours and hours. You're
free to relax or attend to other duties.
The Model 14 is modestly priced, rugged and reliable
for years of dependable service, and will pay for itself
quickly. It's available for 12-, 24-, or 32-volt operation.
Also available are accessories for changing course, dodging,
and power steering by remote hand controls.
Bendix also offers other autopilots for electromechanical
or hydraulic operation. Plus a complete line of radars,
depth sounders, direction finders, radiotelephones and
ignition systems. Contact the Bendix representative in
your area, or write for complete details. Bendix Inter-
national Operations, Dept. EX116-71, 605 Third Avenue,
New York, N.Y. 10016.
The name TtENDIX in u n-gittered imdnnark of Tht llrndit Corp., U.S.A.
Other vital aids for commercial fishers are the Bendix MR-4
radar (left) which is available in 16- or 8%-mile range models.
Depth Sounders (recording or indicating types) with ranges from
50 to 400 fathoms. And (right) the Skipper 850 radiotelephone, a
new, 150-watt, vacuum tube radio designed for extra-heavy duty.
Bendix International Operations
[xxiii]
FISHING BOATS OF THE WORLD: 3
SOREFAME DE ANGOLA S.A.R.L.
Steel Shipbuilders Ship Repairers & Engineers
• Facilities
54000 sq. ft. covering welding shops. Two slip-
ways for vessels up to 200 ft. length. 200
skilled employees.
• Regular Production
Shipbuilding up to 200 feet including: Tugs,
Barges, Pontoons, Coasters, Tankers, Fishing
Vessels and special Marine Craft.
• Repairs & Maintenance
Our shipyard is sited right near to the rich
trawler fishing grounds. We cordially invite
all members of the world's fishing fleets to
call at the well equipped Lobito Port and
avail themselves of our facilities, for ship
repairs or regular maintenance purposes at
European cost and care levels.
P.O. BOX 480
LOBITO
ANGOLA
APELDOORNSE NETTENFABRIEK YON ZEPPELIN & CO. N.V
APELDOORN HOLLAND
with subsidiaries and affiliates
By courtesy of Messrs. Holland Shipbuilding Association, Amsterdam.
One of the many modern sterntrow/ers that ore fishing successfully with ANZA nets.
Manufacturers and suppliers of:
All types of fishing nets, in particular purse-seines and newly developed ground- and
mid-water trawls.
Fishing equipment . Wire ropes . Nylon rope and braided cord . Flags
[ xxiv ]
ADVERTISEMENT SECTION
Dieselelectric Stern Trawler
,,Juan de Urbieta" with Advanced
Three-Phase-Current, CP-Propeller Installation
Three supercharged MWM diesel engines type TRHS 435 S of 640 hp
each at 600 rpm and a naturally aspirated engine of the same type with
an output of 410 hp were chosen as prime movers for the powerplant
which supplies three phase current to propeller motors and ship's mains.
These reliable, sturdy diesel engines proven in many marine type
generating sets are the correct match for the robust maintenance free
three phase-current system.
OTOREN-WERKE MA
HEIM AG
VORM. BENZ A B T . STAT. MOTORENBA
Agents In the U. K.: Tristram Fox ft CO. Ld. Finsbury Court. • Finsbury Pavement • London E. C. 2
U
FISHING BOATS OF THE WORLD: 3
W. WYKEHAM & COMPANY LIMITED
WESTMINSTER
LONDON
SHIPYARDS: PORTHLEVEN, CORNWALL, ENGLAND
BIDEFORD, N. DEVON, ENGLAND
Sea-going vessels for all purposes in steel, wood, light alloy or com-
posite construction, up to ISO feet in length.
One of four Fisheries research vessels being built at
our Bideford shipyard for the F.A.O. for operation in
the Caribbean, the Philippines, Central America and
Lake Victoria, to Lloyds classification "100 A.I Fishing
Vessels". Underwater hull form approved by N.P.L.
with stability conforming to F.A.O. and Rahola criteria.
Fishing equipment includes: Stern Trawling, Gillnet,
Long Line, Live Bait, Trolling and Trap Hauling Gear.
Approximate size:
L.O.A.: 56'; Beam: 16'; Depth: 8' 8"; Draft: 6 9".
Enquiries: 6 STOREY'S GATE, WESTMINSTER, LONDON, S.W.I. Tel: WHItehall 5307 Telex: 22448
FltM HOLD IMlilNt ROOM
Cftew I 4 TMAW4CCI ;
BRIDGE CONTROL
For positive control from bridge or any remote position to
the engine, gearbox, V.P. propeller and/or auxiliaries you
can rely on Bloctube-Hindmarch Remote Controls.
Bloctube-Hindmarch Remote Control Systems are essen-
tial features of modern competitive vessels, designed for
reduced operating costs and greater working profits. The
range includes PNEUMATIC, ELECTRICAL, HYDRAULIC
and MECHANICAL or any combination of these.
Control Systems supplied to owners* specific
requirements.
For CONTROLS - AUTOMATION - CONSOLES-
TELEGRAPHS - consult . . .
BLOCTUBE CONTROLS LTD.
AYLESBURY. BUCKS. ENGLAND
Telephone: Aylesbury 3494 Telegrams: Bloctube Aylesbury
[ xxvi ]
ADVERTISEMENT SECTION
HIDROSTAL MEANS FISHPUMPING EFFICIENCY
For equipping your fishing vessel with a Hidrostal fishpump you should know the following different size characteristics
applicable to each pump.
Type of Pump
E8D
F10D
I12D
L16D
Capacity dewatered fish
100 tons/hour
200 tons/hour
300 tons/hour
500 tons/hour
Recommended largest fish specimen to be handled by this
pump
HERRING
MACKEREL
TUNA
Any up to 4 ft. long and 10 in. diameter
For detailed information contact your nearest Hidrostal Distributor, or:
Head Office: HIDROSTAL S.A. P.O. Box 5734 Av. Argentina 2842
Tel : 44485 Cables: Hidrostal Lima
LIMA . PERU
Telex : WLA-5298
DISTRIBUTORS:
CANADA : Grove Processing Equip-
ment Ltd., 1481 Pemberton
Avenue, North Vancouver, B.C.
Tel : 985-5308
CHILE : Flores, Iversen & Labra
Ltda., Casllla 13550, Moneda812-
Of. 912 Tel : 392845
GERMANY : Reiner Kossman, 415
Krefeld, Ostwall 9, Tel : 35021
NORWAY: A/5 Hydema & Co.,
Ole Deviksvei 14, Oslo, Tel :
878762
PAN AMAiAlimentoi Marino* S. A.
Apartado 4510, Tel : 50834
8. AFRICA: K. F. Albrecht & Co.,
P.O. Box 4750, 304/330 Broad-
way Centre, Capetown. Tel :
2-7394/5-21305
Rock Engineering Works (Pty.)
Ltd., P.O. Box 128, Jenklnson
Street, Parow, C.P. Tel : 98-3881
SWITZERLAND: Hidrostal A.G.,
8213 Neunkirch (SH), Tel : 053/
61331
TURKEY : MUmessiller Ticaret
Limited Sirketl, P.O. Box 1070,
Karakdy, Eski Sarap Iskelesl
No. 15/3, Adriatika Han. Tel :
443357
U.S.A. : Mr. Nicholas F. Trutanlc,
917 South Grand Avenue, San
Pedro, California 90731.
[ xxvii
FISHING BOATS OF THE WORLD: 3
SAN GIORGIO
MARINE AUXILIARIES DIVISION
— Electric, electro-hydraulic and hand-operated steering gears
— Electrically and hydraulically operated anchor capstans and
windlasses capstans, warping, cargo and trawl winches
— Line haulers and power blocks
— Engine telegraphs, rudder and RPM indicators
nuova SAN GIORGIO S.p-a. ViaL. Manara,2.GENOVA-SESTRI(ITALY) telephones 474.141 -471.441
For Anything
That SWIMS
MARINOVICH
-Famous World-Wide-
Trawls, Nets
Fishing Gear
Manufacturers and Shippers for Over 20 Years
Serving the Commercial and Marine Research Fields
Any Type or Design S) Shrimp Trawls • Fish Trawls • Trammel Nets • Lampara Nets •
Gill Nets t) Trap Nets
Specially-Designed Gear for Scientists-Research
Oceanography • Explorations • Limnology
There's a world of experience built into Marinovich Fishing Gear,
Designed to meet any individual needs, Fishing Requirements.
Distributors: Complete lines of ropes, netting, floats, trawl boards,
One-Stop Service for All Your Fishing Gear.
IllflRinOVICH
P.O. Box 294
BHoxi, Mississippi, U.S.A. 39533
Phone: 436-6429 Area Code 601
Trawl Compamj
Cable Address "MARINOVICH1
[ xxviii ]
ADVERTISEMENT SECTION
THIS IS OUR STERNTRAWLER PROGRAMME
FACTORY & FREEZERS
TYPE "WOMME" 800 GRT
TYPE "ALTON A- -1400 GRT
TYPE" 30CHEN HOMANN" 4050GRT
TYPE " HANS PICKEN PACK " 4600 CRT
TYPE "SAXONIAJEUTONIA'-IOOOORT
TYPE "WESER-2200 GRT
RICKMERS WERFT BREMERHAVEN
SINCE 1834
ENGINES
ARE DESIGNED RIGHT
DOWN TO THE LAST
DETAIL FOR HEAVY DUTY
MARINE SERVICE.
360-2700 B.H.P.
AB JONKOPINGS MOTORFABRIK
JONKO'PING. SWEDEN. CABLE: MOTOR • A member of the STAB group
[ xxix ]
FISHING BOATS OF THE WORLD: 3
TRAWLS
MID-WATER TRAWLS
All types of Fishing Gear
Ropes — Wire Ropes
J. H. MEWES & v. EITZEN
2 HAMBURG-ALTONA
Phones: 387945-46
NEUER FISCHEREIHAFEN
Grams: TAUNETZ
FISHING CONTROL UNIT
HANS HOPPE BORDMESSTECHNIK
2 HAMBURG 39— RATHENAUSTRASSE 60
1. Propeller pitch
2. Distance meter
3. Warp tension meter port with alarm (red)
4. Recording instrument for speed (blue), warp tension
meter port (red) and starboard (green)
5. Speed 0-5 and 0-16 knots stem log, side log, bottom
log
6. Warp tension meter starboard with alarm
7. Propeller revolutions
8-14. Ancillary equipment such as echo sounders, fish
location devices, rudder position, coastal telephone,
radar
MOTEURS BAUDOUIN
DIESEL MARINS & INDUSTRIELS
deSOa ISOOcv.
Si&ge Social Usines & Bureaux
165 Boulevard de Pont-de-Vivaux, MARSEILLE (X°) T<§leph: 47 5873
[ XXX ]
ADVERTISEMENT SECTION
EVANGELISTRIA IV"
Built I960 for G. Arcoulis, Piraeus, Greece.
Designed for trawl fishing in the tropics. Two-decked vessel,
upper deck formed as open shelter deck with tonnage opening.
Main Data: Length over all 76,0 m, Breadth 1 1 ,2 m. Depth
7,3 m, Draught 4,87 m, Engine output 2x720
HP at 3100 rpm, Refrigerated fishhold 1 150 m3,
German Lloyd's Classification + 100 A 4 (K).
"VIENNA" "KORNEUBURG" "LINZ"
Three stern trawlers built 1 965 for Edopu Fishing Co., Nigeria.
Main Data: Length over all 23,6 m, Breadth 6,3 m, Depth
3,2 m, Draught 2,5 m, Engine output 480 HP,
Refrigerated fishhold 60 m:>, German Lloyd's
Classification } 100 A 4 (K).
We sell skill
and experience
SHIPYARD KORNEUBURG-VIENNA
2100 KORNEUBURG. AM HAFEN 6, AUSTRIA
Telex: 01 1 856 Preselection No. 0 22 62, 2586 series
DECKMACHINERY "BRUSSELLE" - FIRST CLASS QUALITY
View of the French sterntrawler "Klondyke" top winner
of Boulogne s/Mer, built by Beliard-Murdoch, Oostende for
Nord-P&cheries.
Brusselle-equipment : 3-drum trawlwinch 10 tons pull,
4 hydraulic sweepline winches, el-hydr. steering gear of
10 tonmeter and windlass for chain 32 mm.
AND... YEARS AHEAD BY ITS DESIGN
AND PERFORMANCES
TRAWLWINCHES
Beltdriven — Electric — Hydraulic
The most complete range for all ship sizes
HYDRAULIC STEERING GEARS
in the most different versions of steering methods
ANCHOR WINDLASSES
HYDRAULIC SWEEPLINE WINCHES
combined or not with the trawlwinch
[BRUSSELLl
A. BRUSSELLE Ltd.
NIEUWPOORT- Belgium
Phone: 236.46 Telex: 181.32
', xxxi ]
FISHING BOATS OF THE WORLD: 3
WICHMANN
MARINE DIESEL ENGINE
135-1 400 HP
THE NEW ENGINE
based on the wide experience of sixty years.
THE ROBUST SLOWSPEED DIESEL ENGINE
WHICH NEVER NEEDS MORE SPACE THAN
HIGH SPEED DIESELS.
WICHMANN marine diesels are expressly
designed as marine propulsion engines, and all of
them are equipped with an oil operated clutch
and
Controllable pitch propeller
This gives the following advantages:
You can utilize full power under all conditions of
service, from running free to heavy towing.
You can use a smaller engine for the same work.
You can achieve quick and exact manoeuvring.
You can adjust the speed of the ship to any value, right
down to zero.
You can carry out all manoeuvres from the bridge.
You can carry out any number of manoeuvres in rapid
succession.
WICHMANN marine diesel engines provide a
range of exceptionally efficient power sources
from I35 to I400 h.p.
SCANDINAVIAN FISHERMEN prefer
WICHMANN diesels because of their low fuel
consumption, minimum of maintenance and long
span of life.
Apply for further particulars.
SHRIMP TRAWL WINCH
gentle to the fishing gear
SINCE 1 933
if conical friction clutches
<jAr roller bearings in drums
-jAr oil-bath gear box
^r precision milled wheels of steel
^4r two or three drums
^ metallized
NORSKOV LAURSEN
Engineering Company
Esbjerg, Denmark
cable address: NORLAU
TAIYOfs
Automatic Direction Finder
assures your safe navigation
Transistorized Parfect
A.D.F. TD-A163
• Quick Response
• Compact Size
• Mast Top Installation
• Nominal Power Dissipation
• SSB Reception
Another Products
Facsimile Receiver,
Radio Buoy, Rescue Radio Transmitter
Rubbestadneset, NORWAY
No. 20, 2-ehom,, Ebitu-Niihi, Shibwyo-ku, Tokyo,
Cobl. Addrei*. "TAIYQ WIRELESS TOKYO"
[ xxxii ]
When he
takes over
the Helm . .
ADVERTISEMENT SECTION
" ROSS VANGUARD" Trawler built by Cochranes of Selby for Ross Trawlers Lid., Grimsby.
. . . Cochrane's trawlers, tugs and coasters will still be
in advance of the times.
A modern shipyard such its COCHRANES, builds with un eye lo the future. With 'I rawlcr Owners' co-opera lion every con-
ceivable device for profitable truwliny is in every vessel leaving our yard.
Shipbuilders for GENERATIONS, COCHRANES urc GENERATIONS ahead and our design experts are at your disposal for
the creation of the vessel most suited to your needs.
COASTERS • TANKERS • OIL RIG SUPPLY VESSELS
build fine ships — progressively
OF SELBY Ousc Shipbuilding Yard • Selby • Yorkshire • England
COCHRANE & SONS LIMITI-D TELEPHONE : SFLBY 2636 7/8 • TELEGRAMS : COCIIRANKS • SELBY
TRAWLERS
TUGS
PURSE SEINES
"Tailored to your requirements"
All kinds of fishing gear and equipment
«Boss» purse rings
ADDRESS:
P O B 646 BERGEN - NORWAY
TOMS: NO'RSENET - PHONE in 44
[ xxxiii ]
FISHING BOATS OF THE WORLD: 3
A GOOD CATCH NEEDS PERFECT QUICK FREEZING
OUR EXPERIENCE
COMES FROM
OVER 70 SHIPS
EQUIPPED WITH
SAMIFI
REFRIGERATION
A SCIENTIFIC APPROACH TO THE SCIENCE OF FREEZING
VIA BOLZANO 31 MILANO (ITALY) and in PARIS ATHENS • NEW YORK • BARCELLONA
Two All-purpose
Aluminium
Fish Boxes
For details write to:
or
Bernt Iversen & Son A/S A/S Nordisk Aluminiumindustri
NygSrdsvik, Bergen Drammensveien 40, Oslo 2
NORWAY NORWAY
BELGIAN ENGINEERING AT ITS BEST!
A DIESEL ENGINE
DESIGNED FOR TRAWLERS
POWER RANGE 150-1000 H.P.
ANGLO BELGIAN CY.
WIEDAUWKAAI 35 GHENT BELGIUM
TEL 23.45.41 TELEX 1 1.298 TELEG A.B.C. GHENT
[ xxxiv ]
ADVERTISEMENT SECTION
Contributing a great deal to
modern fishing and
safe navigation
through
DIRECTION FINDERS FISH FINDERS
LORAN RECEIVERS SYNCHRO SONARS
FACSIMILE RECEIVERS MORSE CODE SELECTORS
284, Kamioiaki, Chojamaru, Shinagawa-ku, To
Cable Address: "KOELEC TOKYO"
45' STERN TRAWI.h.R
of ST. MONANCE
Builders of Fishing Craft for over 200 years
Makers of FI PER winches, trawl and se ine — capstans
ami boat equipment
Send for catalogue
JAS. N. MILLER & SONS LIMITED
ST. MONANCE, SCOTLAND
F.V. " EARLY ON " E.238 Lyme Regis. 32'. HB3MGR2
Speed 8-22 knots.
F.V. " LATER ON " E.94 Lyme Regis. SL2MRG2. 24'
Speed 6-2 knots.
THROUGHOUT THE
WORLD
FISHERMEN RELY
ON
LISTER BLACKSTONE
Icelandic Fishing Vessel " Budaklettur " Lister Blackstone
ERS8M 660 h.p. engine driving Liaaen variable pitch propeller
For full particulars of propulsion and auxiliary engines from 3 to 2000 h.p.
write to:
LISTER BLUKMOU MARINE LIMITED
DURSLEY, GLOUCESTERSHIRE Phone: 2981
London Office: Imperial House, Kingsway, W.C.2
Phone: TEMple Bar 9681
MAWKTR SIDDELFY
HAWKER SIDDELEY GROUP SUPPLIES MECHANICAL, ELECTRICAL AND
AEROSPACE CAPITAL EQUIPMENT WITH WORLD-WIDE SALES & SERVICE
[ XXXV ]
FISHING BOATS OF THE WORLD: 3
M7 glassfibre Workboat
can carry 20 people
oHHonsofcargo
with great stability,
highspeed...
and extreme economy
Check the features of the 27' Workboat against any other craft of
its size/capability (if you can find one) :
STABILITY: Unequalled by sin- can give 30 knots safely. Two
glc hull craft of much greater 15 h.p. outboard motors will
waterline length. This means out- give 14 knots. Outboard or
standing safety for passengers and inboard outboard engines can be
cargo, even in rough weather. fitted.
EASE OF HANDLING: One man DESIGN VERSATILITY: Special
can operate the Workboat with- fittings and mountings can be
out trouble. mou!ded into the hull during
MANOEUVRABILITY: The Work
boat can turn in its own length.
SHALLOW DRAUGHT: Only J5//I.
The Workboat can be beached
without damage.
LARGE CABIN & COCKPIT SPACE :
Forward cabin can have two
berths, toilet and galley. Cockpit
11 ft. 9 in. square.
HIGH SPEEDS: Large engines
only £1,250 ex works
building (or afterwards) for in-
struments, lifting gear, winches,
beam trawls, etc.
APPLICATION VERSATILITY:
Personnel and stores transport;
water-taxi operations; ship's ten-
der; trawl and line fishing;
seaside patrol and rescue; ski-
school tuition; photography and
filming; laying moorings; canal
dredging; weed clearing; marine
research ...AND YOUR WORK
exclusive of power unit
Also available: 45 WORKBOAT with cockpit of 190 sq. ft. carries
40-50 people or 6-10 tons of cargo. From £7,500 ex. power unit.
Interested? Then send for a detailed leaflet TODAY:
G.PROUT& SONS LTD.
14 THE POINT - CANVEY ISLAND • ESSEX • Tel: Canvey 2268/9
A KVOiUTION IN THE f/ELD
OF fLOATS
THE "R.L.B. SUPPORTER"
ELIPTICAL FLOAT
AILERONS
FIANCE
FIXING POINT
PRODUCT OF:—
HYDRODYNAMIC
HULL
ANONYME DES ATELIERS
LE BEON
MARINE CASTINGS — DROP FORCINGS
HOT & COLD PRESSINGS
7 Boulevard Nail — Port de Peche
LORIENT - FRANCE
Telephone Lorient 64.28.40
Liquid Fuel Heaters
specially made for use in
ships.
Approved by the Danish
Government's Ships Inspec-
tion.
Cabin stove
Wheelhouse stove
Outer casing made of stainless steel.
Combustion chamber made of heavy
cast-iron with outside ribs for in-
creased heating surface.
Specially designed oil control en-
suring combustion at heeling.
HANSLLARSEN
NYBORG JERNST0BERI I
2 Vester Voldgade,
Copenhagen V,, Denmark
Cable address: NYBORGJERN, Copenhagen
Tel. (01) 14 38 71
f xxxvi ]
ADVERTISEMENT SECTION
W. R. CUNIS LTD
SOLE REPRESENTATIVES FOR
U.K. AND COMMONWEALTH
FOR
OIL-OPERATED MARINE GEARBOXES
ALL SPEEDS UP TO 2000 R.P.M. INPUT
WIDE RANGE OF RATIOS TO OWNERS CHOICE
* RUGGED CONSTRUCTION
* HIGH EFFICIENCY
* PRECISION BUILT
* QUIET RUNNING
OUTPUT END SHOWING TWO POWER TAKE OFF
SHAFTS TWIN INPUT EACH 550 SHP AT 475 R.P.M.
SINGLE OUTPUT REVERSE REDUCTION GEARBOX FOR
TRAWLER MARIE ELIZABETH
57 YEARS EXPERIENCE SPECIALISING IN GEARBOXES FOR TUGS AND TRAWLERS
51 Woolwich Church St. London S.E.I8. Tel: WOOLwich 1194/7 • Cables: APERMACO LONDON S.E.I8
FISH HOOKS -
All over the world
Sole Manufacturers
O. MUSTAD & SON
Established 1832
OSLO, NORWAY
G. E. KRISTINSSON
Dr. DAVID J.DOUST
NAVAL ARCHITECTS
637 CRAIG ST. W.
SUITE 1002
MONTREAL 3. P.Q- CANADA TEL: 868-2788
34-FT LOBSTER FISHING BOAT
JOHN TYRRELL & SONS LTD.
ARKLOW - IRELAND
ESTABLISHED 1864
xxxvli ]
flsfiiii News
International
FISHING BOATS OF THE WORLD: 3
FOUNDED for
SER VICE
Fishing News International was founded six years ago
(October 1961) to serve fishing interests by providing all
countries with up-to-date information about progressive
developments; to describe new craft from lordly all-freeze
vessels to stern trawlers, combination vessels, tuna
catchers and purse-seiners down to small but efficient
inshore vessels; to report and describe new gear, new
equipment, new methods; to report developments in
processing fish and producing meal and oil ; and encourage
better marketing offish.
A^TER four years' operation as a quarterly — during which it won much
praise for quality of editorial and high standard of presentation — Fishing
News International was changed to monthly issue.
This took place 1st January, 1966, and was decided on because of the
increasing volume of important editorial material and also because of the need
for more frequent contact between advertisers and customers in the surging
expansion of these days.
This move has been widely welcomed by readers and advertisers and
rewarded with ever-expanding support.
Our SERVICE is built on QUALITY. In addition to close world-wide
contact with all important forward moves, special attention is given to the
practical details of fishing vessel design and operation and to recording and
estimating the value of new equipment; all this to serve the fundamental need
of catching more fish!
Each month up to a score of new vessels are described with details of speci-
fications and pictures — gleaned from every important fishing country. Each
month up to a dozen or more new types of gear or equipment are described and
generally illustrated. In a year about 200 new vessels are described, of new
equipment well over 100.
That detailed practical service is, we believe, unrivalled in its extent and
enables readers to keep in the forefront of money-making progress. No major
fishing vessel skipper, owner, operator, in the world can really afford not to
subscribe to Fishing News International.
One year
Two years
SUBSCRIPTION
Overseas
£2 15 0 $8
£500 $15
RATES
In United Kingdom
£2 10 0
£4 10 0
Cables: F1SPROBOK
NEWS INTERNATIONAL
11O FLEET STREET, LONDON, E.C.4
Phone : FLEet Street 6961/6
xxxviii ]
ADVERTISEMENT SECTION
GOOD BOOKS ABOUT FISHING
Following publication of the
volume Fishing Boats of the
World (in 1955) recording the
papers and proceedings given at
FAO's first Fishing Boats Con-
gress in Paris, a special subsidiary
company was formed to specialize
in publishing books about fishing.
In the eleven years since then
some 30 titles have been issued
and plans arc in hand to carry the total to 50 or
more in the very near future.
Outstanding in this series arc the major volumes
that have arisen from the various important con-
gresses organised by FAO. These volumes are:
Fishing Boats of the World
Price £7 2 6, plus 6/- packing and postage
($21.50)
Fishing Boats of the World 2
Price £7 7 0, plus 7/6 p. & />. ($22.50)
Fishing Boats of the World 3
Price £7 15 0, plus 7/6 p. & p. ($23.50)
Modern Fishing Gear of the World
Price £5 5 0, plus 5/6 p. & p.
Modern Fishing Gear of the World 2
Price £6150, plus 5/6 p. & p. ($20.50)
Fish in Nutrition
Price £6 6 0, plus 4/- p. & p. ($19)
The Technology of Fish Utilization
Price £5 5 0, plus 5/- p. & p. ($16)
Mechanization of Small Fishing Craft
Price £1116, plus l/6p.& p. ($5)
The issue of these books has contributed to the
excellent work done by the Department of Fisheries,
FAO, all over the world by making available to
practical fishermen, skippers, owners, processors,
libraries, educational institutions and research estab-
lishments, the invaluable information provided by the
world experts mobilized by FAO from every field
bearing on commercial fishery development.
In addition to those volumes we have been happy
to publish independent works all calculated to
stimulate progress in fishing.
An up-to-date list of all our publications is avail-
able on request, but mention is made here of just a
few of the more outstanding works issued :
Fish Catching Methods of the World
By Dr. A. von Brandt, Hamburg
Price £2 J7 6, plus 2/3 postage ami packing
($8.75)
Japan's World Success in Fishing
By Professor G. Borgslrom, Michigan State
University, U.S.A.
Price €2 150, plus 1/9 />. & p. ($8.50)
Underwater Observation Using Sonar
By Professor D. G. Tucker
Price £2, plus 1/3 />. & p. ($6.25)
Stern Trawling
W.F.A. Symposium at Grimsby
Price £2 2 0, plus 1/9 p. & p. ( $6.50)
Trawlermen's Handbook
Modern i/ation of a 60-year old classic brought
up-to-date by Lt.-Cdr. R. C. Oliver for the
Hull Steam Trawlers' Mutual Insurance and
Protecting Co. Ltd.
Price £1 100, plus 2/- p. & p. ($4.75)
Fishing Boats and Equipment
By Lt.-Cdr. John Burgess
Price £1 186, plus I/-- p. & p. ($6.25)
Developments in Handling and Processing Fish
By Dr. G. H. O. Burgess, H umber Laboratory
Price £1 5 0, plus I/- p. & /?. ($4.00)
Fisheries Hydrography
By Drs. llmo Hela and Taivo Laevastu
Price £2150, plus 2/~ p. & p. ($8.50)
The Stocks of Whales
By Dr. N. A. Mackintosh, National Institute
of Oceanography
Price £2 7 6, plus }/6p.& p. ($7.25)
These volumes, all by recognized experts, have set
a standard of publication which will be maintained
in an impressive list of further books to be issued over
the next two years. Ordinarily 6 to 10 new titles are
issued yearly.
Please write for current list :
FISHING NEWS (BOOKS) LTD.
110 FLEET STREET, LONDON, E.C.4
table* : FISPROBOK
Phone : FLEet StrMt (961/6
[ XXXIX ]
FAO
FISHING BOATS OF THE WORLD: 3
YEARBOOK OF
FISHERY STATISTICS
Trilingual. First published in 1948
The most important internationally-published source of world-wide statistical tabulations covering, on a calendar
year basis, catches and landings, disposition of catches, and production, imports and exports of preserved and pro-
cessed fishery commodities. Special efforts are made to publish within approximately 10 months of the close of the
last calendar year covered. The YEARBOOK data for many countries appear months before the data are released
nationally.
Until the end of 1963 the Production and Fishing Graft volume appeared annually and the International Trade
volume biennially. Since 1964 two volumes have appeared annually. The latest volumes are*:
Volume 15
Volume ifo
Volume 17
Volume 1 8
Volume 19
Volume 20
Volume 21
(to appear in 1967)
Production and Fishing Craft
1962 data (published 1963)
Catches and Landings
1963 data (published 1964)
Fishery Commodities
1963 data (published 1964)
Catches and Landings
1964 data (published 1965)
Fishery Commodities
1964 data (published 1965)
Catches and Landings
1965 data
Fishery Commodities
1965 data
$8,00 or 405. or FFs8,oo
$4.50 or 228. 6d. or
$6.50 or 325. 6d. or FF22,75
$5.00 or 255* or FFi7,50
$6.00 or 305. or FFai,oo
$5.50 or 278. 6d. or FFig,25
$7.00 or 358. or
The YEARBOOK is supplemented by a trilingual series of Bulletins of Fishery Statistics. Numbers are issued
from time to time and are available in a limited number of copies from the DISTRIBUTION AND SALES
SECTION, FOOD AND AGRICULTURE ORGANIZATION, VIA DELLE TERME DI CARACALLA,
ROME, ITALY.
FAQ
WORLD FISHERIES
ABSTRACTS
English, French and Spanish Editions
A quarterly review of fisheries technological literature. Subjects include fishing boats, fishing methods, fish handling,
processing, analysis, chemical composition, nutritive value and quality control. The average issue contains about
140 references, abstracted on 69 cards convenient for filing (3 X 5 in. or 76 X 127 mm.), plus two pages of tech-
nological notes. Abstracts can be filed alphabetically by author, subject, UDC and FWS code systems. To assist
the reader to obtain copies of references, eacli reference abstracted carries, where possible, the current address of
the author.
Single issue
$1.25 or 6s. $d. or
Annual subscription
$4.00 or 2os. or FF 14,00
For a free copy of the complete Catalogue of FAO Publications, write to: DISTRIBUTION AND SALES
SECTION, FOOD AND AGRICULTURE ORGANIZATION, VIA DELLE TERME DI CARACALLA,
ROME, ITALY.
1*1]
FAO
ADVERTISEMENT SECTION
FISHERIES
STUDIES
A series of monographs on selected topics of importance in English,
French and Spanish editions.
FAO FISHERIES STUDIES No. 12
Handbook of Mutual Insurance Systems for Commercial Fishing Vessels and Gear
by C. A. Theodore, 1966, 1 17 pp. Price: $2.00 or los. or FF7,oo
Scheduled for publication in 1967.
FAO FISHERIES STUDIES No. n
Financial Assistance Policies and Administration for Fishery Industries
by E. S. Holliman, 1962, 121 pp. Price: $1.00 or 55. or
This is the third FAO publication on financial aid schemes in fishery development. The study is based on discussions
and papers contributed to the FAO Technical Meeting on Credit for Fishery Industries, held in Paris in 1960.
Drawing on his experience as Assistant Chief Executive of the White Fish Authority, in London, Mr. Holliman covers
many of the finer points of administrative decision-making in fishery industries.
FAO FISHERIES STUDIES No. 10
Costs and Earnings Investigations of Primary Fishing Enterprises
by A. E. Ovenden, 1961, 60 pp. Price: $0.75 or 38. gd. or FF2,7«>
A study of the main concepts arid dHinitions of the principal elements of primary fishing economies, with definition
of terms commonly used in costs and earnings studies and with the application of those definitions to practical work.
The book resulted from the FAO Technical Meeting on Costs and Earnings of Fishing Enterprises, held in London
in 1958, which noted that lack of uniformity in fisheries organization seems to act as a barrier to agreement on many
fishery concepts.
A limited number of the following earlier FAO Fisheries Studies is still available:
No. 9 1960 Financial Assistance Schemes for the Acquisition or Improvement of Fishing Craft
(English, French and Spanish editions) $1.00 or 55. or
No. 8 1959 La Science Appliquee aux Peches Intcrieures Aplicacion de la Ciencia a la Pesca Continental
(out of print in English) $0.50 or 2S. 6d. or FFi,75
No. 7 1957 Electrical Fishing (English, French and Spanish editions) $1.00 or 58. or FFj^o
No. 6 1957 Sea-Fish Marketing in the Federal Republic of Germany (English, French and Spanish
editions) $1.50 or 75. 6d. or
No. 5 1957 Governmental Services to the Sea-Fish Industry of Great Britain (English, French and
Spanish editions) $1.25 or 6s. 3d. or FF^o
Information on specific world areas:
The Proceedings and Technical Papers of the General Fisheries Council for the Mediterranean have been published
biennially since 1952 in bilingual English- French editions. The proceedings of the seventh session (1964) are available
at $10.00 or 505.^ or FF35,oo. The eighth session proceedings are in press.
The Proceedings and Technical Papers of the Indo-Pacirk Fisheries Council have been published in English since
1949. Proceedings (Section I) of the eleventh session (1964) is the latest available at $1.00 or 55. or FF3,so. Complete
sets of proceedings are still available for the sixth, seventh, eighth, ninth and tenth sessions. Both the GFCM and
IPFC have additional documentation for specific fisheries problems in their areas.
Aside from its publications, the FAO Fisheries Department also produces documents in the following series: Fisheries
Reports; Synopses; Technical Papers; Technical Assistance and Training Centre Reports.
[ xli ]
FISHING BOATS OF THE WORLD: 3
ONLY SOME OF OUR BOOKS
36 page Book List free on request
FISHING NEWS (BOOKS) LTD.
110 FLEET STREET, LONDON, B.C. 4
Cables: FISPROBOK
Telephone : FLEet Street 6961
[ xlii ]
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