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Full text of "Fishing Boats Of The World 3"

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 

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 C W|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 Bo 1 -' 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- . T rcss, 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 i s 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, mus 4 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 ue 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^f h& 

BMF<:A 

, B f 

RATNAol r -(' 
^EVAJANDA 
V.JAV5JRG 
MALVAN^ 

MURMAGAO"" J^G 
KARWAR 



CANNANORE 

BEYPORE 

^(MALABAFO \R 

COCHIN 
NEENDAKARA 



MAJOR PORTS *nKf 'SMiNi i-u"M " 
fQH DtEf' SFA T RAA.M'i "A'< l 

"Lb WITHIN T MI 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 scith-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 powrd 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 tf 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, 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 


4 


656 


987 


1,154 


1,561 





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 





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 



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 nr j ) 






Period and no. 
of vessels involved 

GT/LBD ft 3 

nr 1 


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 


A d /LBD ft' 

nr 1 


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 m 3 ) 






Period and no. 
of vessels involved 


1930 1940 
(0} 


1941-1950 
(4} 


1951 1954 

(7) 


1955-1958 

(25) 


1959-1963 
(4) 


GT/LBD ft 3 

m :i 





().(X)725 
0.256 


0.00731 
0.258 


0.00722 
0.255 


0.00737 
0.260 


hp/I.BD ft r ' 
nr 1 





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 ft 3 
m y 


__ 


4.27 
0.121 


4.30 
0.122 


4.52 
0.128 


3.22 
0.094 


Ai/LBD ft : ' 
m 3 





0.0102 
0.358 


0.00910 
0.321 


0.00950 
0.335 


0.0102 
0.360 


A rt /LBD ft 3 

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 


981 


98.93 


NC 


47.4 


60.0 


55.8 


49.2 


49.6 


hp 


1^7 


207 


267 


29<> 


338 


FH fV J 

nr' 


3,035 
86 


3.035 
86 


3.035 
86 


2.860 
81 


3.110 

88 


FO ft' 
m a 


670 
19 


742 
21 


8X2 

25 


847 
24 


812 
23 


A, 


119 


108 


12> 


130 


132 


A rt 


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 ft 3 


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 ft 3 
m 3 


3,140 
89 


3,250 
92 


3,070 

87 


3,140 
89 


3,280 
93 


FO ft 3 

m 3 


812 

23 


742 
21 


812 
23 


883 

25 


883 

25 


A, 


116 


117 


128 


138 


142 


A d 


213 


214 


215 


236 


232 



63; 



TABLE 9 continued 


(2) tuna longline fishing vessels 






(a) LBD -12,350 13,250ft 3 


(350-375 m 3 ) 






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 


m 3 


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 ft 3 


3,140 





3,710 


3,430 


3,360 


m :l 


89 




105 


97 


95 


FO ft 3 


917 


_ 


1,340 


1,305 


1,235 


m a 


26 




38 


37 


35 


A! 


111 





121 


130 


135 


A, 


178 


~ 


223 


230 


228 








(b) LBD- 13,250-14,150 ft' 


(375 400 m 3 ) 






Period and no. 


1930-1940 


7947 1950 


1951-1954 


1955-1958 


7959 796.? 


of vessels involved 


(0) 


(4) 


(7) 


(25) 


(4) 


LBD ft 3 





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 


m 3 




103 


102 


106 


97 


FO ft 3 





1,023 


1,160 


1,420 


1,165 


m sl 




29 


32 


40 


33 


A! 





138 


124 


129 


137 


A d 


,-.._ 


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 : ' 
m 3 





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' 

m 1 


-- 


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 ft 3 

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 ft 1 


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 :< 
m ri 


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 fl n 


().(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 


A rt /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 : < 
m 3 


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 3 
m :i 


1,770 
50 


1,590 
45 


1,695 
48 


1,695 
48 


1,695 
48 


FO 


ft 3 
iri 1 


233 
6.6 


315 
8.9 


318 
9.0 


350 
9.9 


364 
10.3 


Ai 





62 


70 


71 


72 


69 


A d 


--- 


109 


121 


106 


106 


118 



Year and no. of 
vessels involved 

LBD 



GT 

NC 

hp 

FH 

FO 



ft :i 
nv< 



ft 8 



ft 3 
m 9 



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 tf 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 ft 3 

m 3 


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* 
m 3 


1,770 
50 


1,590 
45 


1,695 
48 


1,695 
48 


1,695 
48 


FO ft* 

m n 


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 ft 3 

nv' 



GT 

NC 

hp 

FH 



FO 



ft 3 
m 3 

ft 3 
m s 



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 ovr 



.?. 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 

-;::---._. 1 08 
]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: aoo f 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 show r 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 km 2 ) 
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 m a 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 90 l 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 


k K 






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). 



,, ! . ., , , 

f10 110 200 220 240 260 280 300 920 

Shall r p n. 

Fig 14. Opportune II: Free-running power characteristic 



a 80 



O J 



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 





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. 









> 


lOOi 


150 


10 


80 






0. 






* 60 


100- 


5 : 


| 40 


1 15i 




<o 


S : 


75 


20 J 


S 1-0: 






: 


50 


40 


*-'! 


2 5 


30- 


or ^ 


; 


CL 




0^ 


i 20- 


, 100 




2 10- 


t 




o. 


UJ 




J 


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 





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 Thrul 


/ "* --. .. lb 

\ / -- 




- - "i ib 

.^--' 1 1500 


/ 


2500 - 


__^--"' * 






~"" 250 T Prop Rv. 


200 


----.. Pr Mm 


1500 - 









~~ "J Prop Shol 150 






Torqu* Ib 


... 


1000 - 


2 


Ship'* 5pd 


Engmt 


Knol 

. 


" 1 




1 "1 V 




\^ Ship* Spd , 






~~"--^ Knot* 


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 

PfOpl!( 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 



2 * 6 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 

__L Ha ^_ 



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_10 1 ' 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 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, w t is quite small and disadvantageous^ 
decreased from 0.1 to 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 w t . 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 w t . 

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 w t 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 v m (degree), the maximum 
rolling angle is calculated by: 

0m ^ ^ Kyv m /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 r ln 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 v m and N. If 
v m = 5.0" is assumed, the synchronous rolling angle of 
boat A which has hard chine throughout its length is m 
(boat A)416.5 in fig 12 by using its N 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 
N . 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/sec u 
> 7.6 ft/sec 2 


(128 cm/sec 2 ) 
(:> 230 cm/sec 8 ) 



Note: 1 . wave period, Tw: 3.0 sec ( Ts when synchronized) 

wave length, A: 46 ft (14 m) 

maximum wave slope, v m : 5.0 

maximum wave height, H w : 1.3 ft (39 cm) 

H W /A: 1/36 

2, Limit value of unbearable acceleration 

by Kempf 1.97 ft/sec 2 ( 60 cm/sec") 

Inoue 3.93 ft/sec u (120 cm/sec 2 ) 

Kawashima 6.55 ft/sec 2 (200 cm/sec") 

3. Maximum circular velocity at the deck edge 

4 2 ^'** j, (where mttx - radian) 

Maximum circular acceleration at the deck edge 
v ^mux I T J (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 T s -~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, T 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 hhng 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 </> , 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 



2 

Fig 23. 24 ft pole fishing boat 

[ 108] 



4 ft 




[109] 



C E 



Q 



QLD 






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 


ft 3 (m 3 ) 


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 ft 3 (m 3 ) 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 

T m = mean draft 
$0 = angle of initial keel 

0, = maximum rolling angle by synchronous wave 
a = maximum rolling angle by synchronous wave and 
gust 

m = maximum rolling angle 
y p = 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 rduire. 

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'essus 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 base 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, R c , 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/V 1 /^ 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. 




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 (ia r ") 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., C R = R-L/AV 2 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, C R , as a function of the 
nine hull shape and dimension parameters, i.e., 

(1) 



in which V y 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 6r m which when added 
to the speed of the model in the tank r m , 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 <5r m is 
proportional to the slope of the resistance-speed curve, 
we have defined the slope of the (C R K/vL) curve as 
/? at any point, in which case the change in C R due to a 
corresponding change in Vj\jL is given by: 



where 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 a r and a r + 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 a r , #,.+ , 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 (dr m /v n ,) h when // - - gives zero 
as one would expect. Hughes (1961) has given good 
approximate values of the function [<>r m ! r m ] 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 C K 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 f Kii 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 C Ktn 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 


C m 


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 C m and LIB of models analysed in the 
computer study 






Fig 3. Relation between C p 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(X e (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 a B s(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 C m of models analysed in the 
computer study 



Fig 10. Relation between C r 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 70 80 

Fig /.?. Relation between BIT and Mdeg.) of models analysed 
in the computer study 



40 10 



Fig 14. Relation between B/Tand<Xn S (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 C p andC m of models analysed in the 
computer study 



[127; 



LCBW i 



/iff 17. Relation between C m and l.c.b.( ) of models analysed 
in the computer study 



20 30 



Fig 18. Relation between C m and \aL f (deg.) of models analysed 
in the computer study 



I dr(deg) 



Fig 19. Relation between C m and k<x T (deg.) of models analysed 
in the computer study 



20 JO 



Fig 20. Relation between C m and a nx(deg.) of models analysed 
in the computer study 



Toft-Tfwd_ ltK] : 



/'iff 21. Relation between C m and trim of models analysed in 
the computer study 



rig 22. Relation between C r and /.rA( n ) of models analysed 
in the computer study 



(dag) 



Fig 23. Relation between C v and \a. e (deg.) of models analysed 
in the computer study 



Cp 



[ 128 



Fig 24. Relation between C P and far(dcg.) of models analysed 
in the computer study 



Cp 



BS (deg) 



Fig 25. Relation between C p 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 \cn c (dcg.} and I.e. />.(") oj models 
analysed in the computer study 

of MS (dog) 



Fig 29. Relation between x DS (dcg.) and l.c.b.( l( ) of models 
analysed in the computer study 



Lde(dg) 



?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(dg), 

ID ZO 3D 40 50 60 



Fig 31. Relation between Mdeg.) and a r (</<*p.) of models Fig 32. Relation between \*<(deg.) and ^(deg.) of models 

analysed in the computer study analysed in the computer study 

[129] E 



"'J V :V-' ".?" '.-" 



Fig 33. Relation between \oi r (deR.) and trim of models analysed 
in the computer study 



rfBS 
(deg) 



I 

..u .1 



Hg 34. Relation between <y.i t s(deR .) and 0r r U/cv?.) of models 
analysed in the computer study 



I rtr 
2 (deg) 



Fig 3.5. Relation between ^on r (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 C p against , in which there is an absence 
of data for high values of C p 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 a IIN (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 X 2 < were cross-linked, the 
following 9 terms appeared in the equation: 



X 2 

Y 2 
A 2 



Array type (i) 



This array contains all the possible cross-products of 
positive (or zero) powers of X\ and X 2 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/B 9 B/T, 
C m , C r , 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: 



(C P ,B/T), 



and 



(L/B.K). 



[130] 



The only other term in the equation was a simple linear 
term in C m . 

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 C r 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 C r 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 4 C > 
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 C R 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 C m varies between 0.44 and 0.88, a very 
wide range which represents very substantial differences 
in the charactci of the hull forms. Consequently C m 
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\ C p 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: - 

v 2 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 X 2 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, (C p ,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 C fl = (C p xCJ were tested but rejected, 
namely: C fl , 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 C R 
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 {} a 1 a 2 . . . tfgs together with the 
numerical specification of parameters [A^ X 2 X% . . . X$] 
and the individual terms such as X^X 29 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 () . 

In addition to evaluating the values of C Kni for each 
speed-length ratio, the program also determines the 
values of C R at any required ship length (L) together with 
the corresponding values of EHP using the ITTC formula- 
tion, i.e., 

C Ktr =( 



-0.212847 



-( 



log 1. 2834 r. 



3 ) 1 



(7) 



where S~ wetted hull surface area (ft 2 ) 

L= Length on waterline (ft) 

A = ship displacement (moulded) in tons 
(35 ft 3 /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 C Ru 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 C m 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 




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 C R}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 Cjj lfi 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 C Ri6 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 C r = 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 C p 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 C p = 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 



(OC m 



The effects of variations in maximum area 
coefficient C m have been calculated over 
the range C,,,==0.50 to C m ^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 C m 0.65 



there is a penalty in resistance criterion as 
C m is reduced and this penalty is the same 
for all values of prismatic coefficient 
within the range C r = 0.55 to C r = 0.65. 
The slope of the C Rlti -C m curve, however, 
is rather less for values of C m 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 C p =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 
C r =-0.55 to C r - 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 C r 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^ 4V. 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 C p 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) ir 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". :_~ 



/-/X 7 5^. 7'/w effects of variations in half-angle of run from 
the standard value of Aa r 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 C Rn> 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, C m and C n 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.' J BS 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 C R 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 

T aft 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 

T fw t 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 (ft 3 ) 
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 ft 3 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 
59F(15C) in salt water 
Reynolds number = (?'/,/ v) 
Froude number 
speed-length ratio 

maximum area coefficient evaluated to 
waterline WL(C m = AJBT) 
prismatic coefficient based on the maximum 
section area and the moulded displacement 
including stern (C p = 35&/L.A m ) 
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. l n 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 



"AK 2 



R f 



v m 
/ 



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/sec 2 ) 



137 



APPENDIX 

Final Regression Equation 

3 *3 + a 4 AT 4 + tf 5 X 5 + <**** + ^7*7 + tf 8 



+ a ,8* + a i 



X 2 



* X 5 + 53 Xl X 5 4- 54 JV 4 *? 

4 ^6 + ^5b ^4 ^6 +^57 ^4 ^fo 

^ 5K J^T 4 A^ 7 -f 5,, A- A' 7 -h oo X* X 2 



- 66 

^6 + ^68 %2 X6 

+ a 70 X 3 X 



X 2 A r 

X $ X #-+- a$ o X $ X #-\- ci#i A 5 A 8 



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/ , 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 'employe 1 -.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, C m , C p , l.c.b.% l;, ty, a B 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 C Rl6 
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 C p are fixed, the value of C m 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 C R for all possible combinations of these sets 
of live values, and examining the results to find a mini- 
mum C R . 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 \vL r 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. ( / 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 C p , 
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 C p , can be considered independently of 
all parameters except C p . 

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 C p the best 
value of CK and the corresponding value of Ja^ is 
selected. Thus, for C p = .575, i^ = 15 and the first 
approximation to be best C R value, for this C r , 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 C R 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 
C R value is therefore 15.71 -0.67=: 15.04. 

It now remains only to consider the effect of C w ; it 
has been observed earlier, when L/B, B/T and C p are 
fixed with <M constant, the value of C m follows. Table l(c) 
gives the values of C m corresponding to different values 
of C p and (M. Assuming 4.5 to be the value of $p of 
current interest, it is found that for a C p value of .575 
that C w = .758. By interpolation in table l(d) for this 
value of C m the appropriate addition to C R is obtained 
and it is -| 0.1, giving a final value of 15.04 | 0.1 = 15.14 
for C R . This corresponds to the following parameter 
values: 



L/B B/T C m 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 C r , 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 C R{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 C Rl6 with estimated resistance 
for the turbulence stimulators subtracted. Fig 12 to 16 
show these C Rtt 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 B l n and the 
regression coefficients given by the equation in Appen- 
dix 1 of Doust, Hayes and Tsuchiya (page 138). 

A plotting of C Rl6 against A 16 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 Ca JO -Ai 6 was determined for 
each of these speed-length ratios, whilst on the same 
diagram were shown the C KJ8 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 C R|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 C Rl6 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/^Ll.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 







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 Af 5 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 GM and one factor^ M S, 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 = 77.5" 75.2 


35 
72.6 U 


37.5 
72 


45 fl 
67.7 ft 




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 


T r (=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 






T r scc 4.5 6.0 7.6 9,0 


Results of stability analyses of 55-ft (16.8-m) 


hull ( - 


4.25.) 


T r V(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 


T r (= 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. 


T f 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 





KG-T 


-.82 


-.30 


.41 


1.02 


1.64 


(p at GZ max 


32.5 


35 


38" 


42.5 


45 


V at GZ - 


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 


T r V(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 


9atGZ-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 


T r 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 




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 


T r ( 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 


T r (=* B in m) sec 


3.3 


4.5 


5.8 


7.0 


T r sec 


3.8 


5.1 


6.2 


7.3 


D L I T r A/(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 


T f 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 


>90 fl 


: 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 


T f sec 


5.2 


6.2 


7.3 


8.9 


9.4 


T r V(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 


T r 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' 20.3 f> 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 
T r sec 2.9 3.2 3.6 4.0 4.2 
T r x/(g/B) 5.0 5.5 6.2 6.9 7.2 


All lir 

4 
ft 

3 
2 

1 



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 


T f sec 


3.0 


3.3 


3.8 


4.0 


4.0 


T f \/(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 = T r ^/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 T f IB-ratios for different freehoard/B- 

ratios compared with T r 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 M Q 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 =* 


>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 


>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 - 


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 =- 


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 == 


>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 


>90 


>90 


<p at GZ =* 


>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- 
matemticas 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> 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 = M fl sin(o>f + e,) 

= M a sin <Dt cos e, -f M a cos tot sin e t 

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] 



M a SINE t 



M g cose t 




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+ + Rf <f> = K a sin (cot + e A 
With </> 



(*.-> 



(j) a sin cot this expression becomes: 
y 2 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 /? -/o> 2 . The reduced 
quadrature component (A/ fl /</O sin e r 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 e f 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 ' - 
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 UVJ7g ^ 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 p t gb 3 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 GM t 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 D t = 2 GM t 
can be used 

The data which are shown in fig 6, 7, 8 and 9 are 
results of measurements with fl =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 GM t /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 GM t 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 GM t for the conditions A and C satisfied 
the criteria of Rahola, also if the reduction of GM t 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 GM t 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 GM t 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 n a cos e t 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 



0.25 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) 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 ft 3 (3.586 m 3 ). 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 

M a =0289ft.lbs 



CALCULATED 
ACCJQRDJNG TO 
LINEAR 
EQUATION OF 
MOTION 




CALCULATED CURVE 
FOR h/tu008 



TANK IN 
IOPERATION 

EXPERIMENT 
WITH M gS 

"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 

LM a= 0.2$9ft,Lbs 

EXPERIMENT WITH 



CALCULATED CURVE 
FOR h/bsO.08 




TANK IN 
OPERATION 

EXPERIMENT 

WITH: 

l89fUbs 
'0434ft 
IDs 



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 
S kti (co) do> = S c (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**** \ 



,S M 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 

D t 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 
M a Moment amplitude produced by the anti-rolling 

tank 
m Q ^ 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 
T t Theoretical natural period of the water motion 

in the anti-rolling tank 
e t Phase angle between the rolling motion and the 

tank moment 

$i/3 Significant roll amplitude 
p. Non-dimensional tank moment 

/t fl Non-dimensional tank moment amplitude 
v^ Non-dimensional damping coefficient of roll 
CD, Theoretical natural frequency of the water 

motion in the tank 
p t 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 ft 3 (100 m 3 ) 
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 







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 C r 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 


c r 
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. 73 


3. r >4 


6. (.3 


5.95 


147. ! -0 
(13.75) 






































11 


7-U) 


' 


ii 


It 








2 r >,20 
(7.70) 


" 


1.94 

I'- 1 . 59) 


4.59 


0.541 


0.62 r > 


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 
F n >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 F n -0.30 and come down about to cross that near 
F n =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 F n --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 C nie 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 C P 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 C illtt which would correspond to a C p of 0.65 
and a half angle of entrance of 22 J n ? 

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 
C p 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 C B 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 C p . 
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 C n 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, UZ m 

Angle of heel at maximum righting arm, </> m 

Angle of vanishing stability, V 

Initial mctacentric height, GM 

Angle of heel at which the edge of the upper deck 
immerses, rd 

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 (GM ) 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 



T 7 /^ 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 
reduction 1 '. 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 

b 2 
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 w t appears to be 
much lower than o^, the influence can be neglected. When w t 
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 b 3 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 

* I 7 l l \ 


\ S' 

\ ? 


r\ 


ii 


? 1 






p^l 




j- :: _ - X H2 / 






- 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 700ft 2 (65m 2 ). Livadia** midship 
section area was 1,000 ft 2 (93 m 2 ). 



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 7 rt 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 C K 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 C u value for the design under 
consideration: in particular, it does not take into account the 



f 197 



effect of changing C m . 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 C m from 0.758 
to 0.670. From table l(b), this decrease involves a penalty in 
C R of about 2.2 units, which more than cancels out the 
difference in the C R 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(i6 t 
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 in 2 (12.8 cm 2 ) 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 


59 U 


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 15 y 20 25 30 35* 

F 41 50 59 68 77 86 11 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 65F (18C) and at 
65 per cent relative humidity, 9 Ib per 100 ft 2 (0.45 kg/m 2 ) 
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/in 2 (10.5 kg/cm 2 ) 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 65F(18C). 

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 

.j-. 




CIRCULAR SAW 



WALL 



K 



40 ft 


\ 4Oft 




"" j~ rfl- 


If. \ 

\_ _ _ .. ~ _, _ .. _ -. _ _ _ _ i_ _. 




f TJ 

1 , 


1 


i 
. 1 



BAND SAW 



WALL 







,.,, ,. , 


} r - 
i 

L _ 


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 pche 

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/ ) 
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/in 2 
kg/cm* 

lb/in 2 
kg/cm 2 

in-lb/in 3 
cm-kg/cm 11 

in-lb/in 3 
cm-kg/cm 3 

1,000 lb/in 3 
1, 000 kg/cm 2 



in 
cm 



lb/in* 
kg/cm 2 

lb/in 2 
kg/cm a 

1,000 lb/in 2 
1, 000 kg/cm" 



Compression perpendicular to grain : 
Fibre stress at proportional limit 

Hardness: 
end grain 



lb/in a 
kg/cm 2 



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/in 2 


x 10 rj 
kglcn? 


Iblin* 


w 
kRlcnf* 


Ex 
Ih/iri 2 


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 

W a : 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 . < L M 
Material In/in Sip" 
< k /<"> (ctcm, 
C) H) 


Ib/in* (kiz/cm*) * 10" of claMi- 
' B/ city in 


^ C tt c e nt - (b) Laminated pla.tic 
\*9.e 




tion i Ultimate strength Modulus of 
in/2in i lb;in (kg/cm 1 ) * 10 s 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 
: I0 a 


t Compression parallel to grain ' ' '^ rt> sl^ss at 
ding In/in (kg/cm ) |'h/in* (kg/cm 1 ) ; PP- 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/cm 1 ) 
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.' 1OO T 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 68 C5 F (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 pche 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/in 2 kg/om 2 


Minimum 
yield strength 
lb/in 2 kg/om 2 


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/in 2 kg/on 2 


strength 
lb/in 2 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/in 2 kg/am 2 


Yield 
strength i/ 
lb/in 2 kg/on 2 


Elongation ! 
% in 2 in 
(50.8 mm) 


Joint 
efficiency 

%y 


Location of fracture 








tested with beads 












in place 






5086, 


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 1,40 


16.7 


100 


Fusion line, parent plate 








Tested with beads 












machined off 






5086, 


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, 


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, 


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/in 2 (700,000 kg/cm 2 ) and steel about 
29,000,000 lb/in 2 (2,000,000 kg/cm 2 ). Thus, some alu- 
minium plate deflects farther under a given load; the 
kinetic energy of impact (\mv 2 ) 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/in 2 (3,300 kg/cm 2 ), a yield strength of 37,000 lb/in 2 
(2,610 kg/cm 2 ) 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/in 2 
(3,170 to 3,520 kg/cm 2 ) with a yield strength of about 
35,000 lb/in 2 (2,470 kg/cm 2 ). When stretch-forming has 
to be done, however, a hot rolled steel is used with a 
yield of 24,000 to 28,000 lb/in 2 (1,690 to 1,970 kg/cm 2 ). 
When it comes to strength to weight ratio alloy, 5,086 is 
18,000 lb/in 2 (1,270 kg/cm 2 ) per unit weight versus 7,000 
lb/in 2 (493 kg/cm 2 ) for steel and no more than 15,000 
lb/in 2 (1,060 kg/cm 2 ) 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 IADUPONAN UlllUUU KNtl 

tTtfNf.TM or MOM ni IDR ITIII AMDtnt OUAKANIICI> UIIIM*U$ ct 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 t 3 kg/om 3 


Ult. tensile 
lb/in 2 kg/cm 2 


Tield tensile 

2 2 
lb/in kg/ cm 


Ult. shear 
lb/in 2 kg/ cm 2 


Shear to grair 
lb/in 2 kg/cm 2 


Ult* bearing 
> 2 2 
; lb/in kg/cm 


Mod. of 
elasticity 

lb/in 2 kg/cm 2 


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/in 2 kg/cm 2 lb/in 2 kg/om 2 % I/ 


Hardness 
Brinell 
Ho. 2/ 


Shear 
Ultimate 
strength 
lb/in 2 kg/om 2 


Bearing 
Ultimate 
strength ^/ 
lb/in* kg/om 2 


Fatigue 
Endurance 
limit j 
lb/in 2 kg/om 2 


Modulus 

Elasticity / 
lb/in 2 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 10 6 


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 IO 6 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 IO 6 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 IO 6 0.705 x 10 6 


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 IO 6 0.705 x 10 6 


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 10 6 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 10 6 0.705 x IO 6 


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 IO 6 0.719 x lO 6 


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 IO 6 0.719 x 10 6 


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 IO 6 


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 IO 6 


5083-H113 


46,000 3,240 33,000 2,320 16 


84 


27,000 1,900 


- 


23,000 1,620 


10.3 x IO 6 0.725 x 10 6 


5086-0 


38,000 2,670 17,000 1,200 22 


65 


64,000 4 r i>10 


79,000 5,560 


- 


10.3 x IO 6 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/in 2 kg/om 2 lb/in 2 kg/on 2 % i/ 


Hardness 
Brine 11 
Ho. 2/ 


Shear 
Ultimate 
strength 
lb/in 2 kg/on 2 


Fatigue 
Endurance 
limit 4/ 
lb/in* kg/cm 2 


Modulus 

Elasticity ^/ 
lb/in 2 kg/om^ 


5086-E32 


42,000 2,960 30,OOO 2,120 12 


77 


25,000 1,760 


- 


10.3 x IO 6 0.725 x IO 6 


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 IO 6 


5086-H112 


39,000 2,750 19,000 1,340 14 


68 


23,000 1,640 


22,000 1,550 


10.3 x IO 6 0.72t> x IO 6 


5154-0 


35,000 2,470 17,000 1,200 27 


58 


22,000 1,550 


17,000 1,200 


10.2 x IO 6 0.719 x IO 6 


5154-W2 


39,000 2,750 30,000 2,110 15 


67 


22,000 1,550 


18,000 1,270 


10.2 x IO 6 0.719 x IO 6 


5154-B34 


42,000 2,960 33,000 2,330 13 


73 


24,000 1,690 


19,000 1,340 


10.2 x IO 6 0.719 x IO 6 


5154-B36 


45,000 3,170 36,000 2,540 12 


83 


26,000 1,830 


20,000 1,410 


10.2 x 10 6 0.715* x IO 6 


5154-112 


35,000 2,460 17,000 1,200 25 


63 


- 


17,000 1,200 


10.2 x IO 6 0.719 x IO 6 


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 IO 6 


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 IO 6 


5454-H112 


36,000 2,540 IB, 000 1,270 Iti 


62 


23,000 1,620 


16,000 1,270 


10.il x ID 6 0.719 x IO 6 


5456-0 


45,000 3,170 23,000 1,620 24 


75 


28,000 1,970 


- 


10.3 x 10^ 0.72!) x IO 6 


5456-*321 


51,000 3,600 37,000 2,610 16 


90 


30,000 2.120 


- 


10.3 x IO 6 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 IO 6 0.705 x IO 6 


6061-96 


45,000 3,170 40,000 2,820 12 


95 


30,000 2,120 


14,000 985 


10.0 x IO 6 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 


in 2 o 2 


Strength minimum 
Ultimata Yield 
lb/in 2 kg/cm 2 lo/in 2 kg/cm 2 


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 


-0.500 -13.2 


All 


17,OOO 1,200 10,000 705 


12 


6063-T6 


-0.124 -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 


- 


.036 


0. 


71 - 


0. 


91 


1/16 


1 


.57 


Over 


0. 


036 


- 


.048 


0. 


91 - 


1. 


22 


3/32 


2 


.38 


Over 


0. 


048 


- 


.064 


le 


22 - 


1. 


62 


I/* 


3 


.14 


Over 


0. 


064 


- 


.080 


1. 


62 - 


2. 


30 


5/32 


3 


.96 


Over 


0. 


080 


- 


.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 


- 


.188 


3. 


25 - 


4. 


77 


5/16 


8 


.45 


Over 


0. 


188 


- 


.20 


4. 


77 - 


5. 


08 


3/8 


9 


.50 


Over 


0. 


20 


- 


.25 


5. 


08 - 


6. 


35 


7/16 


11 


.10 


Over 


0. 


25 


- 


.30 


6. 


35 - 


7. 


62 


1/2 


12 


.70 


Over 


0. 


30 


- 


.35 


7. 


62 - 


8. 


88 


9/16 


14 


.30 


Over 


0. 


35 


- 


.40 


8. 


88 - 


10.02 


5/8 


15 


.90 


Over 


0. 


40 


- 


.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-G 4 ) 

A-SC!? 1 
+Cr 


(AlMgSiCu) 


PASXO 4 ? 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 iAi 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 
<*ih 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 stl 
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 stel 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 TransomDecking 

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 

Propeller20 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: 
L57 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.ovrd OftCk l/4m(6?Smm) aluminium with decking 



Wait__2Jgjjifi 3/8 in (10 mm) plywood 



i 3/4 < 5 1/2 PQK t?gmi 22 C-C 
,'X ' 5/6in(l6mm) plywood gusitt f <') 



et I i/4 fi \/ m(4!Si40fi\rt)i ook 2? C -C rromt 3l 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 piyood 

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 
'.76565mm) 



21/2 l/4in(4x.5m 
Stttl F.8. 



4*1/4 in (102 65 mm) F B. alum in 
4in*5/l6m| \ v i/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 < ?03Bmm) 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 p R 2,7) IWlnl32mm) 

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 I25x30in(306x76j5x75mm) 
|\fjan mt_. . ... .1 


Vl6:n(5mm)AI. 


4x3xl/4in(l02 76563mm) * 
JfLVtrttd t : 
BtBx 
brack* 

-?. xl 1/2x1/4 ml5l 3 8 65 mml.iwar. tf d 



eBx.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 ft3in5/16m alu 
U02765B mm) 



Vfeln ttMl platt 
IB mm] 



8 in olum 
2mm) 



4 5/16 in tll 
. ]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 2xlxJ 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 




($448) 




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 7f ff 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 ' 
(/6b3mm) 



21/2 Bl/4ui(646.5mm) 
Stttl F.B. - . 



J to 4 in i9/l6nl v I/4 m alumi 
(l50lOZ8mm)i. ! I '6 5 mm) 



MS w . 

(Smm) 



3l/4tn Al F- B 



/r- * T" L j- 5/l6 * 6 <nl6l53mm) 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 lixlx 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. 



IO2B86iB89in(254n7352Z6mm) 





. 9Lmlnium L. iffl. 21 U PR Ml . 1 M In ( 32 mm ) 




aluminium pip* stanchion ^ , 




.2 8 IniTjBjm) afamtntum J3 inl8 4mm) Alyn^ 






X \ 


S 5 " 




\433/8in{l02r6.5IOmm) 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/2l/4in 




2il l/2>IMh 






4 3 5/l6in(IOZ 76a8mm) 






(91 i38K6.fi mm 


i 




aluminium I 


Ja*- 




. 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.K3665mm)'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 lx 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 




($448) 




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 7j 5 c 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 dbouch a ce procd, & 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 
59 GT 
1019 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 ft 3 (1,000 m 3 ) 
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/in 2 (0.25 kg/mm 2 ), 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 ft 3 (m a ) 






(1.51) 
2,970 


(1.53) 
3,110 


(1.52) 
2,980 








(84.0) 


(88.2) 


(84.4) 


Fish-hold capacity, ft a 


(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: outsideglass 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 amliors 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 
proprits 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, comparndolo 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/ft 2 (0.587 to 1.546 
g/cm 2 ). 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/yd 2 
(70.47 g/cm 2 ) 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/yd 2 (169 to 190 g/cm 2 ) 
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/in 2 
(21,130 kg/cm 2 ) 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/ft 2 (1.566 g/cm 2 ) mat and 24 to 27 o7./yd 2 (169 to 
190 g/cm 2 ) 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/yd 2 (169 to 190 g/cm 2 ) 
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/ft 8 (2.87 to 3.83 kg/m a ) 



[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/ft 3 (2.87 to 3.83 kg/m 8 ) 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)N G 5" T HCK 
- 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/FT 2 ) 




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^NAL 1 -. 



* 4* X 3" X .l7*J\. ' \ 

SPACED IB" O.C. \ 

Plf Ttf B "y IS 



TlT ^T y ^j 

~/ 7 

B"x3%.L J l"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 6 H 
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 laminates 41 



Physical property} 

Per cent glass by weight 
Specific gravity 

Flexural strength 
lb/in a x 10 3 
kg/cm 2 x 10" 

Flexural modulus 
Ib/in 3 xl0 6 
kg/cm 2 x 10 

Tensile strength 
Ib/in 2 xl0 8 
kg/cm 2 xlO 6 

Tensile modulus 
Ib/in a xl0 6 
kg/cm 2 x 10 

Compressive strength 
lb/in*x!0 3 
kg/cm* xlO 3 

Compressive modulus 
lb/in a x 10 6 
kg/cm 2 x 10 

Shear strength perpendicular 

Ib/in a xl0 3 

kg/cm a x 10 3 

Shear strength parallel 
Ib/in a xl0 3 
kg/cm 2 x 10 3 

Shear modulus parallel 
Ib/in a xl0 6 
kg/cm 2 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/ft 2 (1 .566 g/cm a ) mat and 24 oz/yd 2 (169 g/cm a ) 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/ft 2 
(1.57 g/cm 2 ) mat and 24 to 27 oz/yd 2 (169 to 190 g/m 2 ) 
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 
', l n 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 rut 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/ft 3 (2.87 to 3.83 kg/m 3 ) 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 


ft 2 


200 


220 


230 


230 


234 


234 




(m 2 ) 


(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 


in 4 x 10 3 


16,660 


1,242 


4,173 


3,641 


4,285 


3,590 




(cm 4 x!0 3 ) 


(686,730) 


(51,230) 


(171,990) 


(150,140) 


(176,680) 


(148,000) 


Modulus of elasticity, E 


lb/in 3 xlO 6 


.85J 


30 


.95 


1,2 


.95 


1.2 




(kg/cm 2 x 10") 


(0.060) 


(2.1) 


(.067) 


(.085) 


(.067) 


(.085) 


El 


lb/in 2 xlO 13 


14.1 


37.3 


4.0 


4.3 


4.0 


4.3 




(kg/cm* x 10 12 ) 


(41.3) 


(109) 


01.7) 


(12.6) 


01.7) 


(12.6) 


Stiffness relative to wood 







2.6 


.29 


.31 


.29 


.31 


Section modulus 


in 3 xlO 3 


190.4 


13.6 


46.2 


40.4 


47.9 


40.2 




(cm 3 x 10 3 ) 


(3,121) 


(242) 


(757) 


(663) 


(785) 


(659) 


Stress for 2.7 x 10 6 ft Ib Mom., 


lb/in 2 


170 


2,190 


700 


800 


680 


810 




(kg/cm 2 ) 


(11.9) 


(154) 


(49.3) 


(563) 


(47.9) 


(57.1) 


Ultimate strength 


Ibin 2 


6,500 


60,000 


14,000|| 


17,000[ 


14 V 000|| 


17.000H 




(kg cm 2 ) 


(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 10 6 lb/in 2 , 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 -! SS aS mso g"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 shipyards 9 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 ft 3 


6,000 (165.6m 3 ) 


6,600 (182 m 3 ) 6,900 (190 m 3 ) 


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 mcaniques, 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 matri- 
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/cm 3 
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/in a xI0 8 



-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 F t , 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 : 

a h = M ; M =s %F b l = bending moment 
W = %H 2 = 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/in 2 (kg/cm 2 ) 


lb/in 2 (kg/cm 2 ) 


lb/in 2 (kg/cm 2 ) 


lb/in 2 (kg/cm 2 ) 


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 


a B 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 (2.1xlO fl ) 


10,000,000 (700,000) 


crry 1 


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) 


Ey 3 ... 


318,000 (22,250) 


361,000 (25,432) 


63,200 (4,452) 


538,000 (37,900) 


<TJ y" 1 x 10 2 x 6,920" l 


100 


241 


102 


179 


<r B y- 2 xlO a x7,100- 1 . 


100 


144 


13 


64 


Ey~ 3 xlO a xl87,000- 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 
F b that the deflection, a, surpasses acceptable values, 
although the bending stress a b may stay within normal 
limits. Therefore, stiffness and strength must be dealt 
with separately. The deflection, a, depends on the ratio 
F b /EI where = modulus of elasticity, and 7= moment 
of inertia = T V A 3 . 

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- 1 xl(Px6 f 92D- 1 



FRP mat 

lb/in 2 
(kg/cm 2 ) 

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/in 2 

(kg/cm 2 ) 

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/in 2 

(kg/cm 2 ) 

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/in 2 

(kg/cm 2 ) 

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/in 2 

(kg/cm 2 ) 

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/in 2 

(kg/cm 2 ) 

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 H 2 



0.05 H 2 



= 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/in 2 (1,100 kg/cm 2 ) 
=1,145,000 lb/in 2 (80,000 kg/cm 2 ) 

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