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THE DESIGN AND CONSTRUCTION OF POWER WORKBOATS
By ARTHUR F. JOHNSON. N. A.
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Tke Design ana Construction
-^ of
Power Workboats
by
Arthur F. Johnson, N. A.
Copyright in tKc United States and Canada
and
Entered at Stationers' Hall, London
1990
By The Penton PublisKing Company Cleveland, Ohio. U. S. A.
All
RigKts Reserved l)#/)i
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NaVal architecture as applied to power worl^- hoats lacks literature; perhaps because bigger game is more absorbing. When it is realized that the future inland waterways of this country must be developed and utilized; also that power boats will provide the means of avoiding the repetition of lamentable inefficiency in conveying the products of our interior to the principal ports or centers of distribution, proper design will be no small factor in the solution of the problem.
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I Table of Contents
Chapter I — Advantages and Classifications 1
Chapter II — Analyzing Operating Conditions 5
Chapter III — Buoyancy, Draft and Displacement 9
Chapter IV — Laying Down and Fairing the Lines 15
Chapter V — Stem, Keel and Stern Design 19
Chapter VI — Application of Steel Construction 25
Chapter VII — Wood and Steel Transverse Framing 29
Chapter VIII — Design of Longitudinal Framing 33
Chapter IX — Bulkheads Demand Careful Planning 37
Chapter ^— Hull Planks— Fenders— Bilge Keels 43
Chapter XI — Decks for Wood and Steel Boats 47
Chapter XII — Constructing the Deck House 53
Chapter XIII — Companions — Hatches — Awnings 59
Chapter XIV — Mats — Davits — Winches — Windlasses 65
Chapter XV — Anchors — Towing — Deck Drainage 71
Chapter XVI — Auxiliary Machinery and Quarters 75
Chapter XVII — Food Storage, Heating and Lighting 79
Chapter XVIII — Painting Structure and Sheathing 83
Chapter XIX — How Concrete Power Boats Are Built 87
Appendix I — Tables of Scantlings for Power Workboats 93
Appendix II — Designs and Details of Typical Power Workboats 101
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List of Illustrations
Page |
Fig. 1 — Cost Chart ok Power Vessels Under Normal Building Conditions (Commercial) 5 |
Fig. 2 — Cost Chart of Large Power Vessels (Commercial) Under Normal Building Conditions 6 |
Fig. 3 — Character Curves Sternwheel Power Boats (Wood) Less Than 100 Feet Long 6 |
Fig. 4 — Hull Proportions Sternwheel Power Vessels Over 100 Feet Long 7 |
Fig. 5 — Hull Proportions Power Tugs Over 60 Feet Long 7 j
Fig. 6 — Character Curves Power Lighters 8 |
Fig. 7 — Hull Proportions Small Screw Vessels (Wood) 8 |
Fig. 8 — Shows Water Pressure Acting on a Floating Vessel 10 j
Fig. 9 — Illustrates Relation Between Draft and Displacement 11 |
Fig. 10 — Indicates the Utility of Reserve Buoyancy 11 j
Fig. 11 — How External Force Causes Heeled-Over Position 12 |
Fig. 12 — Path of Water Around a Box-Shaped Hull 12 |
Fig. 13 — -Gradual Stream-Line of a Properly Formed Vessel 12 |
Fig. 14 — Lines of a SO-Foot Power Tug 14 |
Fig. is — Various Forms of Stems IS |
Fig. 16 — Various Types of Sterns 16 |
Fig. 17 — Sterns for Sh.\li.ow Draft Vessels 17 |
Fig. 18 — Paddle Wheel Stern 17 |
Fig. 19 — Illustrating a Typical Body Section 18 |
Fig. 20 — Stem of a Wooden Tug 19 j
Fig. 21 — Stem of a Small Power Workboat 19 |
Fig. 22 — Stem of a Large Vessel 250 Feet Long 19 |
Fig. 23 — Stem of a Large Wooden Vessel 20 |
Fig. 24 — Construction of Spoon Bow for Shallow Draft Bo.\ts 20 |
Fig. 25 — Clipper Stem of Auxiliary Sailing Vessel 20 |
Fig. 26— Construction- ok Bottom Girder of Large Wooden Ship 20 |
Fig. 26a — How Keel Bolts are Countersunk 21 |
Fig. 27 — Keel of a Wooden Schooner 21 |
Fig. 28 — Keel of a Wooden Tug 21 |
Fig. 29 — Keel of a SO-Foot Workboat 21 |
Fig. 30 — Keel of Shallow Draft Vessel 21 1
Fig. 31 — Overhung Transom Stern of Auxiliary Schooner 22 I
Fig. 32 — Stern of Tug or Lighter With Single Deck and Guard Timber 22 |
Fig. 33 — Transom Stern for Small Boat With Metal Rudder 22 |
Fig. 34 — Compromise Sterns Seldom Used on Workboats 22 I
Fig. 35 — Shallow Draft Stern With Stern Wheel 23 |
Fig. 36 — Longitudinal Section of Wooden Tunnel Stern Boat 23 |
Fig. 37 — Cross Sections Showing Different Tunnel Construction 23 |
Fig. 38^Bar Stems and Method of Scarphing 2S |
Fig. 39 — Three Types of Keels of Steel Vessels 25 |
Fig. 40 — Methods of Fitting Keelsons 25 |
F"ig. 41 — Center Keelson with Innercostal Plate 26 I
Fig. 42 — ^Transverse Section of Double Bottom 26 I
Fig. 43 — Construction of Overhung Transom Stern 26 |
Fig. 44 — Attaching Guards and Rails 26 I
Fig. 45 — Construction of Rudders and Strut Bearings 27 |
Fig. 46 — Elevation and Plan ok Sternwheel Vessel 27 |
Fig. 47 — How the Bottom Plating is Dished for Tunnel Stern 27 |
Fig. 48 — Stern (Or Bow) of Double Ended Steel Ferry Boat 27 |
Fig. 49 — Construction for Tugs and Power Lighters 29 |
Fig. 50 — Transverse Framing of Large Wooden Vessels 30 |
Fig. 51 — Frames for Shallow Draft Vessels 30 |
Fig. 52 — Midship Section of Steel Tug or Lighter 30 |
Fig. 53 — Where the Main Deck Overhangs the Hull 31 |
P"iG. 54 — Shallow Draft Vessels Have Straight Frames 31 |
Fig. 55 — Steel Stanchions and Stanchion Heads 32 |
Fig. 56— Longitudinal Stringers and Shelves For Wooden Tugs; Frames for Shallow Steel Vessels 33 |
Fig. 57 — Cross Sections Showing Frame Construction 34 |
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List of Illustrations
i
Page
Fig. 5S — Steei, Side Keef-sons with Transverse Frami.nx 35
I Fig. 59 — Haic it and Cockpit Coami ng Construction 35
Fig. 60 — Cross Section of a Tug with Longitudinal Framing 36
I Fig. 61 — What Happens When the Bow or Stern Compartment is Flooded 38
I Fig. 62 — Transverse Watertight Bulkhead of Wooden Vessel Longer Than 125 Feet 38 |
I Fig. 63 — Transverse Watertight Bulkhead for Small Wooden Vessel 39 |
I Fig. 64 — Cross Sections of Various Minor Bulkheads for Cabins, Etc 39 |
I Fig. 65 — .Steel Bulkheads and Fastenings for Wooden Vessels 40 |
I Fig. 66 — Shows Method of Fitting "Shoes" at Bulkheads Where Keelsons and Stringers are Cut 40 |
I Fig. 67 — Construction of Tank Bulkheads for Oil and Water; Also Metal Bulkheads for Minor Com- I
I PARTMENTS 41 |
I Fig. 68 — How Stealer Plates ari: Introduced 43 |
I Fig. 68-a — Methods of Fitting Hull Plating to Frames ; 44 |
I Fig. 69 — Construction of Fenders and Bilge Keels 45 i
I Fig. 70 — How Decks are Classified 45 |
I Fig. 71 — Drawings Showing Contour of Decks and Sheer 4g |
I Fig. 72 — Methods of Laying Deck Planks 48 |
I Fig. 7.3 — Cross-Section of Wooden Deck Construction 49 j
I Fig. 74 — Construction of Decks of Steel Vessels 50 |
I Fig. 75 — Construction of Ceilings and Double Bottoms 50 |
1 Fig. 76 — Contour and Construction of Wooden Deck Houses 54 |
I Fig. n — Construction Details of Steel Houses 55 |
j Fig. 78 — Watertight Doors, Air Ports and Dead Ligh f s 56 1
I Fig. 79 — Construction of Hinged Windows a.xd Skvlights 57 |
1 Fig. 80 — Wood and Steel Companions 59 |
I Fig. 81 — Detail Construction of Companion Slides and Hatches 60 |
I Fig. 82 — Watertight Hatches and Manholes 61 I
I Fig. 83 — Construction Details of Ladders and Kails 62 i
I Fig. 84 — Awning Stanchions and Fittings 63 1
I Fig. 85 — How Pole Mast and Boom is Fitted 65 |
I Fig. 86 — Construction and Install.mion of Steel Masts, Also Boom Crotch 66 I
j Fig. 87 — Davits and How They are Installed 67 I
I F'lG. 88 — Winches, Windlasses and Ground Tackle 68 I
Fig. 89 — Anchors, Chocks and Hawse Pipes 72 |
Fig. 90 — Towing Bitts and Knees ■]■>, |
Fig. 91 — Chocks and Cleats 73 |
Fig. 92 — -Fuel or Water Tanks, Flat Side Type 75 |
Fig. 93 — Installation and Equipment of Fuel Tanks 76 |
Detail of Inlet Connection for Pipe Suctions from Sea 76 1
Detail of Soil Pipe Discharge Connection 77 1
Detail of Scupper from Tiled Toilet Space 77 |
I Fig. 95 — Built-in Refrigerator in Cabin Trunk of 50 to 75-Foot Power Boat 7g |
I Fig. 96 — Construction of Refrigerator Door 79 |
I Fig. 97 — Interior of Stack with Tanks 80 |
1 Fig. 98 — Ventilating Equipment gO |
I Fig. 99 — Ventilating Equipment 80 I
I Fig. 100 — Pipe and Transom Berths 81 |
I Fig. 101 — Bilge Keels and Sheathing 84 1
I Fig. 102 — How Wood Sheathing is Fitted on Wooden Hulls 85 1
■ Fig. 103 — Typical Section o.'^ a Concrete Hull Under Constructiu.\- 88 |
I Fig. 104 — Metal Clips Used to Support Longitudinal Rods 89 i
I Fig. 105 — Method Used in Holding Rods in Place for Pourixc; Forms 89 =
I Fig. 106 — Molded Guide Bar Punched to Receive Rods. This is a Very Satisfactory Method Used with |
I Excellent Results 89 I
I Fig. 107 — Construction of Stanchions and Girders 90 |
1 Figs. 108 and 109 — Bow and Stern Construction for a Concrete Workbjat 90 1
I Fig. 110 — Details for Attaching Miscellaneous Fittings 91 |
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Arthur F. Jihnson, N. A., authcr cf De- sign and Cunslraciion 0/ Power Wcrl^boots, apptars here in the unikrm of AssislanI Marine Superintendent of the U. S. Army Transport Seroiez. Besides being educated as a natal architect and marine engineer, h: has had wide experience in th: U. S. Engineer's Department and in shipbuilding yards and as Designing Engineer for the Fabricated Ship Corporation, Milwaukee, Wis., so that h; has a practical as well as a theoretical knowledge of the subject. Mr. Johnson, at thz present writing is Produc- tion Manager of Nelson Purchasing Organiza- tion, Chicago, III.
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CHAPTER I
Advantages ana Classincations
^^^^^HE utilization of vessels, propelled by internal M C^\ combustion engines, for commercial transporta- ^ J tion by water is no longer in the experimental
^^^ stage; nor has there been a dearth of literature setting forth the general characteristics of the numerous uses to which this type of craft has been adapted. From the very first, good engineering portended success of this class of vessels, since there can be no sounder logic than that
points should be understood by owners, operators and builders.
In general power workboats may be classified under three main headings: First, service in which engaged; second, material of which constructed; and third, type and arrangement of propelling machinery.
With respect to service, the first consideration is whether the waters navigated are to be "open" or
chemical energy as contained in fuel will produce maxi- "sheltered;" that is, whether the vessel is to go to sea
mum power when converted into mechanical energy at the nearest practicable location to the point of applica- tion of the power.
Whereas, in steam-propelled craft, the latent energy in fuel was first converted into heat of gases due to combustion, these gases then transmitting their heat to water in a boiler, generating steam ; this in turn passing to the engine, losing con- siderable heat content en route ; in a combus- tion engine all the en- ergy conversion takes place in the cylinders. This not only results in saving of weight by omission of boilers and increased space for car- go storage due to lesser space occupied per horsepower, but also the abolition of heat losses and the carriage of wa- ter for boiler feed.
These advantages were at first oflfsct by practical defects in com- bustion engine design, lack of skill on the part of the operators and the customary conservative frame of mind on the part of vessel owners which is inevitable to all radical innovations
or to operate in rivers and harbors.
Seagoing vessels to date have been mainly cargo car- riers (wooden or steel) or auxiliary sailing craft. The construction in these being identical with that of steamers, has been thoroughly treated in other works of ship
design.
V e s s e Is traversing coastwise, harbor or inland waters are those here to be dis- cussed and embraced'
(1) Ferries:
(a) Fast passenger.
(b) Passenger and freight.
(c) Car.
(2) Tugs.
(3) Power lighters.
(4) Tank boats:
(a) Water.
(b) Petroleum prod- ucts.
(5) Trawlers.
(6) Shop boats: (a) Repair boats:
(Machine shops) (Welding plants)
(7) Pumping and wrecking boats.
Passenger ferries vary from fine-lined relative- ly fast vessels of from 50 or 60 feet, to 200 feet in length. Depend- ing upon the length of run they may vary in speed from 10 to 20
KUMTUX, LUMBER TOW BOAT
She is 65 feet x 16 feet and is powered with a 110-horsepower Standard-Corliss
engine. She is owned by the Puget Sound Tow Boat Co. and has given her
owners great service
miles (statute). Their characteristic arrangement is to afford maximum passenger accommodation : Sleeping, mess accom- modations and sanitation for the large craft on long runs (seldom more than for one night) ; and maximum seating, sanitary and sometimes messing provisions for relatively short Since power boats, particularly those using the lighter runs not exceeding one day (sunrise to sunset). fuels, have practically replaced the small steamers of fore-
in industry. The tendency to let others pay for the experi- ments incidental to practical perfection delayed progress in development.
Power Boats Have Replaced Small Steamers
gone days, and the ones requiring considerable power and cheap fuel have long since shown the dcsiral)ility of diesel engines ; effort should be made to co-ordinate the valuable experience of operators and record the features of design in power boats. This is particularly desirable with respect to the smaller vessels, where ordinary power- boat construction would prove fragile and the essential
Jitney Boat for Commuters
A recent innovation in this connection has been the "jitney boat", making runs from points within an hour's run of a city or railroad depot, and used for transporting commuters.
Passenger and freight ferries of moderate speed (8 to 12 miles), relatively full lines and ranging in length
The Design and Construction of Power Work Boats
welding. With the prevailing prices at present, and as long as steel ex- ceeds $0.03 per pound, this would not be desirable, however.
Composite vessels arc those with wooden hull planking and steel framing. For boats under 100 feet long, this is scarcely a desirable construction, though in larger ones it is being ex-
from 50 to 200 feet are becoming in- creasingly popular as sources of profit. The holds and main deck are employed for freight storage and the superstruc- ture houses the passengers. A cargo boom forward facilitates lifting heavy weights, the hoisting winch being geared from the main engine or being an inde- pendent machine. There is a single- ended type for voyages of more than tensively employed.
one-half hour or so ; the ones for short Wooden construction is the most and frequent trips as well as the car universally employed and desirable for ferries being double-ended. They may vessels less than 100 feet long. This be propelled by screws or paddle wheels, is due to the facility in working the Tugs comprise probably the most nu- material, simplicity of equipment needed merous class of the commercial power in building yards and also to the fact boats. Their lengths are from 35 to that vessels up to this size are amply 150 feet and speeds (when not towing) strong when built of wood. Steel, if too from 8 to 12 miles. Many of the con- light, has not the requisite stiffness and ventionalities in tug design could be corrodes through quickly. If the steel improved or dispensed with to the ulti- is made heavier, care must be taken mate betterment of the whole. This that the vessel is not of greater dis- will be elaborated upon subsequently, placement than would be the case in a The essential to a tug's success is great pulling power at slow speeds, requiring a heavy-duty, slow-turning engine coupled to a propeller of large diameter and low pitch ratio (0.9 to 1). Power lighters are modified types with large decks and hold space for cargo and a boom for loading. Tank boats, as their name iin- plies, carry water or petroleum in bulk, the form being full and the engines aft (at the stern). Trawlers are of tug design, fit- ted with hoisting booms and fish tanks. They attained no- toriety in the recent war by their utility in mine sweeping. Shop boats, carrying machine shop tools, welding plants and apparatus are becoming numer- ous. They are constructed with a view to bringing the repair
equipment to the disabled plant, in- wooden one of corresponding size and stead of requiring the cripple to visit strength.
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ir,\,,.,., , .-CnOONER CONSTANCE One of the finest boats ever built for halibut service- measures 87 feet on deck, 18 feet beam and carries horsepower Standard-Frisco engine
the shipyard. Workboats used for salv- ing and wrecking purposes carry a mis- cellaneous equipment, such as pumping apparatus and machines for handling divers. With the value of vessel prop- erty going up sky high these boats are becotning profitable.
Steel Too High for Small Boats
By material of construction is ineant that of which the prmcipal strength members and hull are composed. Steel is most universally einployed in vessels over 100 feet long, though it has been used in pressed form for small power and life boats. In the writer's opinion powerboats as small as SO feet long, pro- viding they are full lined, could -be built of light galvanized steel shapes and plates, riveting being replaced by spot
Power workboats of wood are much more substantially built than are pleas- ure craft and it is to establish stand- ards and details in these practical ves- sels that this Avork is undertaken.
Reinforced concrete promises to be- come extensively used in boat construc- tion, particularly where a considerable number of the same form and size of vessels are produced. It is no longer an experimental construction, barges and seagoing vessels now building being the result of observing, for years, those already in service.
Concrete Boats for Inland IVatcrways
Steel and concrete having nearly the same coefficients of expansion and the fact that painting, copper sheathing and fouling of bottoms will be troubles of
the past as well as that deterioration is negligible, point to extensive utilization of this desirable material, particularly for inland waterways. A very rich mixture (1-1-^-3) of concrete, with gravel passing J-^-inch mesh, is used for the hull. This is molded or "shot" onto galvanized wire mesh supported by ordinary reinforcing rods, the to- tal hull thickness varying from 2 to 5 inches. Internal hull structure em- bodies reinforcing steel skeleton work with a leaner concrete (1-2-4) or (1-3-5) again using fine gravel. The density of concrete determines its life, strength and watertightness as well as its elasticity. Ordinary con- crete, as commonly used ashore, would not prove satisfactory for ves- sels. If the ships are molded, stand- ard metal molds may serve for nu- merous hulls, but if one or two only are to be built, the "gunning" meth- od is more desirable, particularly in view of the fact that a more nearly ship-shape form can be built in this manner. Molded hulls have resulted in crude- ness of lines and while this is immaterial at low speeds, tugs or finer craft would require excessive power unless more refined in form. The type and arrangement of the propelling machinery together with the means of converting the power generated into propulsive thrust will not be elaborated upon except wherein they affect hull construction or arrangement. The power plant itself may be combustion engines of any one of the following types :
(a) Diesel or oil engines, op- erating on two-stroke or four-stroke cycle using heavy oil fuel (between 14 degrees and 23 de- grees B a u m e), wherein fuel is i n j e c ted as spray into the cylinders with compressed air and ignition results from high compression of the charge. Revolution ISO to 300.
"Semidiescl" — or heavy distillate engines, using kerosene or dis- tillate fuel with hot bulb igni- tion or spark. These engines are similar to ordinary gasoline machines, but operate at slow speed and are much more heav- ily constructed. Revolutions from 200 to 600.
Gasoline engines (usually four- stroke cycle) using light pe- troleum distillate, with electrical ignition, low compression and operating (in heavy marine work)
-She 140
(b)
(c)
Advantages and Classifications
between 350 and 800 revolutions
per minute, (d) Gas producer plants using coal,
wood or other gaseous fuel. Diesel or oil engines being relatively high powered, are not much used in small commercial power boats. An in- teresting departure from this generality is the government tug Manteo which has a 100-horscpower, 2-cycle, dicsel en- gine and which is only 50 feet long.
"Semidiescl" engines, a rather vague and incorrect term, are excellent for heavy duty service providing the oper- ator understands them. Such engines should be more extensively utilized than they now are, not only because of the saving in fuel, but their rugged con- struction and ability to run continuously if properly attended. There have been some sad experiences, however, when inexpertly handled.
Gasoline, or light distillate engines, of heavy duty design, are usually direct connected to the propeller and are the most generally employed. Sometimes, in order to conserve space and weight, small, high-speed engines (900 to 1200 revolutions per minute) are installed with a reduction gear to the propeller shaft. This system is comparatively re- cent in ships, though long used in auto- mobiles. It promises to become pop-
ular if light fuels do not attain pro- hibitive prices.
Gas producer plants have never been extensively employed, though when prop- erly designed and operated they have proved practical and economical. They consist of a producer proper, where fuel is caused to give off its combustible gases through distillation, partial com- bustion and sometimes chemical combina- tion with water vapor.
The fuels used may be wood, coal of a low grade or residue combustible material. The gases generally pass through a "scrubber" where foreign matter is removed by spray or other means and thence to an internal combustion engine.
The arguments against producer plants are : Excess weight and space occupied by the plant, and skill necessary to proper operation.
The propulsive mechanism of com- mercial power boats may be propellers or paddle wheels.
Propellers are most commonly em- ployed where light draft is not a factor in design. This is because of their pro- tected location with respect to the hull, which minimizes damage by striking against docks, towed vessels or by rough seas. Another reason is that higher revolutions with efficient propulsion ren- der them adaptable to direct coupling
with engine shafts, with attendant re- duction in space occupied by machinery of a given power.
Paddle wheels (at side or stern of vessels) are desirable in shoal water because of efficient propulsion under limited depth of immersion and also fa- cility of repairing buckets damaged through striking submerged olistacles.
The practical range of revolutions in paddle wheels is between 20 and 40, rendering necessary a reduction in speed from engine to wheel. This is accom- plished through belts, gears, chains, or a combination of these.
Profcllcrs in Tunnel Boats
Propellers in tunnels, so that the wa- ter surface at rest is not more than one-third of the wheel diameter below the upper tip of blades, are frequently employed for shallow draft propulsion. Though the wheel diameter is restricted and revolutions comparatively high, ex- cellent results have been obtained in this way, even in tow boats. In these, the out-of-the-way propellers present an advantage over the projecting paddle wheels, and the lightened and less roomy machinery afford lighter draft on a given size of vessel or permit of de- crease in vessel dimensions for given draft and power.
The Design and Construction of Pozvcr Work Boats
CHAPTER II
Analyzing Operating Conditions
"^^^^^HE first essential in selecting m (7\ a design of power boat is a ^ J careful study of the require- ^^^^ ments imposed by the service in which it will be engaged. This will determine the general arrange- ment, degree of equipment, power, amount of fuel, stores and water, ma- terial and construction, etc.
It is assumed that one undertaking the construction of a commercial vessel will familiarize himself with these re- quirements by careful study of the local conditions at the terminals and through the trade route which the vessel is to ply. Conditions are so varied and the combinations of these so numerous that exhaustive discussion would scarcely be warranted.
In general the factors encountered are :
(1) Character of service.
(2) Character of materials ported.
(3) Conditions of water traversed.
(4) Terminal adaptation to the trade
contemplated.
The design as affected by character of service has already been considered, as have the general features called for in passenger traffic.
Freight may be roughly subdivided into :
(a) Fast package.
(b) Perishable.
(c) Miscellaneous
slow.
(d) Bulk. The first of these
has heretofore been most extensive on ocean or large in- 1 a n d or sea trade routes, services in which natural con- ditions have pro- hibited land trans- portation. There is reason to suppose that with reliable and well adminis- trated inland water- way runs, much of this revenue earn- ing cargo could be diverted from the none too punctual rail routes of this country. This does not infer competi- tion, but rather co- operation with the railroads, since
many water routes are shorter between terminal points and the question of collection and delivery may afifect to- tal time in transit and portage charges. Fast water freight would work well in conjunction with passenger traffic. It is not very many years gone that travelers preferred canals to stage coach and the analogy still applies insofar as comfort and restful conditions in water travel surpass those in a sleeping car. It is merely a question of providing every convenience and shortening time in transit which are not insurmountable difficulties in many overnight runs.
Kinds of Freight Handled
Perishable freight is of two general kinds : That which will deteriorate due to delay in shipment (mainly edibles) ; and that which must be protected from the weather. The first of these will require refrigeration or ventilation, and the second merely storage in holds or under cover. Both of these classes are readily adaptable to economical water conveyence, delay at terminals being the most adverse condition to be remedied.
Miscellaneous slow freight already constitutes a considerable percentage of the total transport material in some
sections of this country and a greater proportion in many foreign lands than is generally supposed. It consists of many items in variegated sizes from large pieces of machinery to small boxes, cases, castings, etc.
Bulk freight lends itself most agree- ably to storage and terminal loading and discharge. It consists of coal, brick, petroleum, ore, grain, etc., and renders possible the design of vessels specially fitted to carry the particular commodity. Maritime traffic in this class is also profitable and constaiith increasing in volume. Freight affects hull design in conjunction with the route of travel, necessitating large closed holds or 1)eing most expeditiously stowed on deck in the open or under cover. The amount to be carried per voyage is dependent upon length of the trip (in distance as well as duration). If the dis- tance is considerable, the decreased num- ber of trips will necessitate a larger ship that profit may result. On a short run the assumption that gross expense of conveyance is inversely proportional to tonnage conveyed, does not necessarily hold, since the increased time for load- ing and discharging may be excessive when considering the loss in vessel's earning power while idle and the great- er original invest- ment. Again, the depth, width and contour of channel, dimensions of locks, wharves and man- euvering space at terminals may be considerations af- fectinjc size, pro- portions and even propelling mechan- ism of the vessel. Thus a compara- tively narrow and shallow river with sharp bends, locks, and sometimes rap- ids, would necessi- tate radically differ- ent design from that permissible with a wide, deep and open stream. Paddle v.'heel or tunnel-sterned boats with shallow beamy hulls have arisen
The Design and Construction of t'oivcr Work Boats
from the first mentioned natural limila- tions, whereas the normally formed screw vessel is desirable where these ob- stacles are absent or negligible.
How to Determine First Cost
When the appropriate type and its lengths have been decided upon, it be- comes necessary to determine the prob- able first cost and also the other dimensions properly applicable. The ideal condition with respect to funds would be that in which these were ample for the most desirable type of vessel. Very often this is not the case, and modifica- tions in design must be resorted to.
If the total costs of numerous vessels in a class are plotted as ordinates upon abscissa representing vessels' lengths, it will be found that all the resulting spots lie within an area enclosed by two curves, which are the maximum and minimum amounts requisite for building this type of vessel for any length.
Figs. 1 and 2 are "cost charts" of this nature, the smaller vessels having cost ordinates to large scale in Fig. 1, while the larger vessels' prices are modified to suit the limits of Fig. 2.
It will be observed that the screw vessels in Fig. 1 are more costly than the shallow draft paddle vessels. This is because of the more complex form and rugged structure of the former, requiring more elaborate and carefu! workmanship to withstand the strain? of rougher waters which are navigated by this class. The same reasoning ap- plies to Fig. 2, where it will be further noted that steel vessels are most ex- pensive in cither class.
The excess first cost of this material is more than offset by the gain in strength, durability and carrying ca- pacity, for contrary to general supposi- tion, the total weight of a wood vessel is greater than that of a steel one hav- ing equal strength, while the interior volume of the wooden one, representing cargo capacity on given dimensions, is also less than that in the steel hull.
The costs here plotted represent re- sults of competitive bids during normal
times, contracts having been awarded not necessarily to the lowest, but rather to the most responsible bidder, as deter- mined by capital and equipment of the boat yard.
If a certain fund is available for the construction of power boats, the vari- ous sizes of a given type could be derived as follows : Assume that the amount at hand is $40,000. Then in Fig. 1, an 82-foot wooden screw tug could be built to maximum equipment standards and two 87- footers of simplest character in normal times. At present the costs would be higher — the above sum affording a vessel about 70 feet long, with all refinements and two 40- footers which would be little beyond hull, engine and steering gear.
On the other hand, if a vessel of given length is to be built, its cost range could be similarly arrived at. In Fig. 1, a 60-foot tug (wooden) would range between $7500 and $23,750. The maximum figures are most nearly in accord with present mean rates for ordinary boats.
Beam Varies on Given Length
For a given length of vessel, the beam (width) and the depth may vary considerably. This variation is limited in the case of beam, by its effect upon stability and speed for a given power. Also to complicate matters, where the increased beam heightens the tendency to resist capsizing force, it will result in greater resistance to propulsion.
The degree to which stability may be sacrificed to minimizing resistance has been determined within minimum and
Analyzing Operating Condition!;
maximum limits, beyond which it is rarely and with questionable gain, that proportions are assigned in design.
These proportions are graphically de- picted in Figs. 3 to 7, and dimensions for any length selected from these can- not fail to produce vessels of ample strength, stability and reasonably speedy in proportion to the power installed.
The depth of hull at mid-length is an index to strength, just as the depth of a girder determines ability to resist deflection. A deeper vessel on given length is relatively stronger than a shallow one.
Power of the engine to drive the hull whose dimensions have been selected, is the next consideration. Too many vessels, particularly in the "small boat" class, have either too much or too little energy in the machines driving them, for a vessel may be over as well as under-powered. It is fallacious to pre- sume corresponding increase in speed for additional horsepower.
Further, it is impossible to calculate the exact resistance of a given sized boat by direct mathematical analysis. This is because, even with two vessels having like dimensions and diplacement, the hull forms may vary considerably.
There is at present no precise mathe- matical formula for that peculiarly warped surface of a hull, and until this is established (which will only be after years of investigation) the only ways to properly predetermine engines, are :
(a) By comparison of results in other similar vessels.
(b) By actually towing a model of the vessel, to scale, and deriving the
result through the "method of com- parison".
The first of these methods is that most feasible in power workboat de- sign ; the second, though in large ves- sels usually more reliable, is too elabor- ate and occasionally does not produce results anticipated, particularly in un- usual forms. Since it is impossible to install machinery to scale in the model, or to fit miniature propellers, thereto, considerable experience is necessary to
^^
foretell the energy dissipated between engine and the point of expenditure of propulsive thrust. Adding to this the cost of a series of models, also the ex- pense of conducting the tests at a properly equipped model testing basin, the method does not at present justify its adoption for small commercial boats.
In these, allaround working qualities are often superlative to minimum resist- ance at given speed, so that unless predecessors of like proportions have proven uneconomical, the result of ob- serving their features (favorable or not) will ordinarily produce excellent re- sults.
To this end, Figs. 3 to 7 have been elaborated, embracing powers, displace- ments, drafts and speeds of various types. These are characteristics of many boats in each class and may be considered representative.
Working Out the Details
Assume that the vessel is to be an 80-foot stern wheel towboat of wood. In Fig. 3, we would derive the follow- ing limits for particulars of the hull by reading up to the various curves as ordinate on the abscissa labeled 80:
Length, 80 feet.
Beam, between 16 feet and 20 feet 6 inches.
Depth of hull, 32>^ inches and 51 inches.
Draft in running condition, 17 inches
and 25J4 inches. Displacement (fresh water), between
31 tons and 73 tons.
The Design and Cunstniction of Poivcr Work Boats
Brake-horsepower of engine, 37 to 62. derived from the remaining charts if Speed (per hour) 6 to 10 miles. other types of vessels are under consid-
These preliminary figures may be eration. It should be understood that
the lowest horsepower is the one which will drive the narrowest hull at the minimum speed, the higher power in the narrower boat will probably produce the maximum speed figure, while in the beamier boat this power will result in a speed intermediate between maxi- mum and minimum.
The next consideration is that of fuel capacity, the kind having been predeter- mined by considerations of economy, facility of replenishing, etc., in the locality of the vessels' route. Gasoline and light distillate engines will require about a pint of fuel per horsepower per hour. This figure is high for a fuel consumption test with the engine on the blocks at the factory, but it must be understood the ordinary working conditions in the boat will prove less economical, due to wear, leakage, occa- sional overheating and perhaps neg- lect. It is therefore imperative to antici- pate these difficulties by providing fuel ample under worst conditions.
Fuel oil for diesel engines will be safely estimated at 0.7 lb. per horse- power per hour.
In our chosen vessel, at 62 horse- power, burning gasoline or distillate, that many pints or 7j4 gallons would carry the wider boat eight miles and the narrower one ten. From this the tank capacity could be determined, de- pending upon facility of re-fueling. If the home dock were capable of re-filling tanks (a desirable feature) less fuel need be carried with increase in amount of freight. It should not be necessary to re-fuel oftener than once per work- ing day, and, of course, if the voyage required more time than this, once per trip, if feasible.
The general arrangement will be gov- erned by type. Accommodations for crew need only be fitted if these can- not return to their home port nightly, in which case necessary plumbing, lock- ers, etc., must also be installed. A study of arrangement will later be made, it being sufficient for any type to assume a somewhat similar layout to other boats in the same class, many of which have been ably described by current magazine contributions.
The preliminary study of and deci- sions with respect to design have now been gone over, bringing us to the stage at which details must be understood and perfected.
CHAPTER III
Buoyancy, Draft and Displacement
'^^^^^^HE first requirement which m (t\ commercial vessels must have ^ 1 is the ability to float. By ^^^ this we mean that they should be suspended on the water's surface and that a certain portion of the hull should be above that surface. Now if the total weight of a boat be divid- ed by its total watertight volume in cubic feet, the resulting figure is the pounds per cubic foot or the "density" of the vessel. If this weight per unit of volume is greater than that of a cubic foot of water, the vessel will sink.
Fresh water has a weight of 62.5 pounds per cubic foot, while salt wa- ter weighs 64 pounds for an equal volume. A cubic foot of solid iron weighs 490 pounds and would sink in fresh or salt water. A cubic foot
of wood which weighs from 30 to 60 pounds will float in water. If a cubical box, 1 foot on each side, were made of steel sheets J4 inch thick the six plates forming the sides would weigh 10 pounds each, making a total weight for the box of 60 pounds. This 60 pounds is the density of the box and since it is less than the weight of a cubic foot of either salt or fresh water, the steel box will float.
In fresh water we could put a load of 2 pounds in the 60-pound steel box and it would still float. In salt water this load could be iYz pounds.
We thus see that the difference be- tween the total weight of a floating body and the weight of an equal volume of water represents the cargo carrying capacity and that the same
vessel will carry more cargo in salt than in fresh water.
Experiment on Flotation
Take a shallow tray and weigh it carefully. Then place a deep bowl in the tray and fill the bowl brim full of water, taking care that it is just on the point of overflowing into the tray but that none of the water gets into the tray. Now weigh a square block of wood which is about half as wide as the bowl. Place the block carefully on the water in the bowl. The block will float in the bowl and some of the water will over- flow into the tray. Take the block carefully out of the bowl and lift the bowl from the tray, being sure that no more water spills. Then weigh the tray again with the water which
SCANDIA, SEA-GOING POWER HALIBUT BOAT OF THE TACIFIC COAST
9
10
The Design and Coiisfructioii of Power Work Boats
was displaced from the bowl by the floating block.
Deducting the original weight of the dry tray from the final weight of the tray with displaced water will give the actual weight of the water. It will develop that the water displaced will weigh exactly what the block did.
We therefore see that the weight of a floating body is exactly equal to the weight of water it sets aside or displaces.
Now imagine that while the block floated in the bowl, we had frozen the water in the bowl. Then if the block were removed a cavity would remain in the ice and this cavity would have exactly the shape and volume of that part of the block below the water level. The shape of this cavity is called the "under- water surface" of the floating body.
If the water which overflowed into the tray were pourad back into the cavity in the ice it would be filled and no water would remain in the tray.
This proves that: "The volume of water displaced by a ship is exactly
First the form of hull is carefully drawn and its volume is calculated to diflferent heights above the bottom of the keel. When the volume to each level or "water plane" has been formed, determine the weight of an equal volume of the water in which the vessel is to float by multiply- ing the number of cubic feet in the hull to each water level by the weight of a cubic foot of water.
In general the ton is used for dis^ placement weights in preference to the pound, that the figures employed may not be too large. To convert cubic feet of hull volume to the number of long tons (2240 pounds) of water displaced by that volume, divide by 35 for salt or 36 for fresh water. This is based on the fact that one ton of fresh water equals 35 and of salt water equals 36 cubic feet.
Suppose that a chart is made where- on heights above a given base line represent draft to scale. On the base line we can represent displacement in tons or in cubic feet by a hori- zontal scale measuring from left to right. Then if our calculations at 2 feet draft had shown the vessel's
8 X 10
X 75 = 41.67 cubic feet
144
FIG. 8-SHOWS WATER PRESSURE ACTING ON A FLOATING VESSEL
equal to that part of the ship below underwater volume to be equal to 10 the waterline," and that: "The weight tons of displaced water we could in-
of the water displaced by a ship equals the ship's weight."
This displaced water is the "dis- placement" of the ship and may be expressed in cubic feet or pounds.
Hold a body of known weight at arm's length and let go of it. The body falls to the ground. This shows that if any mass is suspended and
dicate this displacement by a point on the chart 2 feet above the base and 10 tons to the right of the ver- tical line through zero. A similar point for the displacement corre- sponding to each level for which the hull volume has been calculated would show just how the weight of dis-
not prevented from falling it will placed water increased as the vessel answer the attraction of gravity. sank to diflferent water levels. A
Now fix a spring scale to .the body curve through these spots is known
and again hold it out. The pull on the scale shows the body's weight. Therefore, to prevent a body from falling, the force holding it up must equal the body's weight.
A body floating is subject to the same "pull" of gravity, but is prevented from falling, or rather "sinking" by an upward force in the water called "buoyancy", whose magnitude equals
as the displacement curve, one of which has been drawn in Fig. 14.
Getting the Weight of the Lumber
After the complete plans showing the vessel's construction and the loca- tion of each item therein have been drawn, it is possible to calculate the weight of every item and of the struc- the ship's weight and also that of the ture. For example the keel may be displaced water. a timber of oak 75 feet long and 8
The foregoing principles are applied inches wide by 10 inches deep. The in determining to just what level a volume of this timber in cubic feet ship will float and the method of is obtained by multiplying the cross doing this follows: sectional area by the length.
Oak weighs about 54 pounds per cubic foot when saturated with water and allowing for fastenings. There- fore the keel of the vessel would weigh:
41.67 X 54 = 2250.18 pounds or slightly more than one long ton.
Performing a similar calculation for the other framing, the hull planking, the deck beams and planking, the bulkheads, deck houses, tank and engine foundations, masts, booms, deck fittings, life boats, furniture and joiner work, machinery, tanks, steer- ing gear, etc., we obtain the com- plete hull weight in pounds. Divid- ing this sum by 2240 gives the tons for the vessel's light displacement. If the holds are calculated full of the cargo which is to be carried and the water and fuel in the tanks are added to this, the sum of these three figures is the total deadweight of cargo which may be added to the light displacement thus getting the full load weight or displacement of the vessel.
Now on the base line of the dis- placement curve find the figure cor- responding to the light displacement in tons. Draw a vertical line from this point to the curve. Then at the point where this vertical line cuts the curve, draw a horizontal line over to the scale showing draft. The figure so found will be the light draft of the vessel and a similar procedure with the load displacement will indicate the full load draft.
After the vessel is built the dis- placement scale is useful in finding the weight of cargo carried per trip. This is done by taking the vessel's light displacement in tons from the load displacement as obtained from the curve by reading the tons corre- sponding to the draft with cargo on board. The diflference gives the long tons of cargo.
An Illustration of Buoyancy
Fig. 8 shows the water pressures acting on a floating vessel. These may be divided into horizontal and vertical forces and are shown by arrows. The horizontal forces on the sides are equal and opposite at each depth below the surface and therefore balance each other so that there is no tendency to move side- wise, "d" is the draft in feet and the upward pressures on each square foot of the bottom equal "d" times the weight of a cubic foot of water. The sum of all such upward pres- sures equals the force "buoyancy" which keeps the vessel afloat.
Buoyancy, Draft and Displacement
11
Fig. 9 illustrates the relation be- tween draft and displacement with and without cargo. When the vessel is light, "d" is the draft, "DC" the water line and the rectangle "D C E F" a cross section of the hull below wa- ter. "C B" is the center of gravity of the displaced volume and is called the "center of buoyancy". The upward force of the water is assumed to be concentrated at this point.
When cargo is placed aboard, the vessel's weight increases and the force of buoyancy acting in the light condition is not sufficient to support it. The vessel, therefore, sinks to the new water level "A B" where buoyancy as represented by the in- creased weight of displaced water becomes equal to the augmented weight of the vessel, "d' " is the new draft and "C B'" the new center of buoyancy.
The height "f" of the deck above the water line is called the "free- board". It is a measure of the weight which can be added to completely submerge the vessel by increasing the displacement by the volume "H K A B". This volume is called the "re- serve buoyancy" and is necessary for stability and safety against sinkage.
What is Meant by Reserve Buoyancy
In Fig. 10 the utility of reserve buoyancy is indicated. Assume that the box-shaped vessel has two walls or "bulkheads" (G M and FN) divid- ing it into three compartments, and that the vessel floats at the water line W L. Suppose that a hole is made in the bottom of the central compartment so that sea water enters between the bulkheads. Before this occurred the volume of the hull (B CFG) between these bulkheads dis- placed a certain amount of water and thus helped to float the vessel or rather to support as much of the total vessel's weight as would equal the water displaced. When water en- tered the compartment the section between the bulkheads no longer af- forded buoyancy since the volume of sea water originally displaced rushed back into the cavity. Meanwhile the vessel's weight has not changed and since this weight exceeds the net amount of intact buoyancy represent- ed by the displaced volumes A B G H plus C D E F, the vessel will sink until the weight of water displaced again equals the original amount. This sinkage is assumed to the water line W L'. During the sinkage the water rose freely inside the damaged compartment to the level M N and no buoyancy could therefore be regained in that compartment.
FIG. 9— ILLUSTR.'\TES RELATION' BETWEEN DKAFT AND DISPLACEMENT
When sinkage has ceased, the vol- ume L M G H plus the volume N P F E equals the original volume A D E II, and since by taking B C F G from A D E H we get the same vol- umes as by taking L M B A and N P D C from the sum of L M G H and N P E F, we see that the added end displacements LMBA plus NP DC must equal B CFG.
Figuring Reduced Freeboard
Notice that the original freeboard "I" has been reduced to "{'". This reduced freeboard is easy to calculate in the case of a box. For example assume that the vessel in Fig. 10 is 100 feet long, 30 feet wide and 10 feet deep. Suppose the bulkheads G M and FN to be at a distance of 40 feet from each end, or that the distance between them (B C) is 20 feet. If the draft (A H) is 5 feet before the bottom is punctured, what will be the new draft after the acci- dent to the central compartment? First calculate the volume of the orig- inal displacement
A D E H = 100 X 30 X 5 cubic feet = 15,000. 15,000
Then — • = 428 4/7 tons of salt
35 water or 15,000 := 416 2/3 tons of fresh water.
35
Then when G F is punctured the lost volume of displacement is B C F G = 20 X 30 X 5 = 3000 cubic feet.
Therefore the amount of original displacement remaining is 15,000 — 3000 = 12,000 cubic feet = ABGH plus CDEF.
The lost 3000 cubic feet must be replaced by volumes LMBA plus N P D C which are each 40 feet long and 30 feet wide but whose
heights L.'\ arc not known.
Volume LMBA = 40 X 30 X (LA) feet; volume NPDC = 40 X 30 X (LA) feet.
Volume LMBA = 1200 X (LA) feet; volume N P D C = 1200 X (L A) feet.
LMBA + NPDC = 2 X 1200 X LA feet = 2400 X LA' = 3000 cubic feet.
3000
LA ^ =: 114 feet which is
2400 the amount the vessel will sink. The new draft is 5 plus \]4 = 6j4 feet.
The Value of Transverse Bulkheads
The foregoing shows the value of transverse bulkheads and also makes it clear that the volume above the original water line W L and outside of the damaged compartment (B C G F) must be greater than the lost buoyancy (B C G F), for unless this can be regained in the undamaged ends, the sinkage (L A) will be great- er than the freeboard and the vessel will not float after the accident.
When some external force inclines a boat the conditions which exist in the heeled-over position are shown in Fig. 11. The water line when up- right was at W L and the displace- ment volume had the rectangular cross section R A S T. Point B is the center of buoyancy when upright and point G the center of gravity of the vessel and its contents. W' L' is the new water line when heeled over and it crosses the original water line at point O.
An Analysis of Stability
Observe that the cross section N D S T of the underwater bedy has been changed to the form of a trape- zoid, whose center of gravity is at B'. This point is therefore the center
.^'l l |
. .n |
/y |
p 'i m'l' |
||||
"' ivi. |
a. |
c |
D i W L |
||||
H |
<s |
; |
i -1 |
11 |
r |
E |
|
1 |
1 1 |
ff |
FIG. 10— INDICATES THE UTILITY OF RESERVE BUOYANCY
12
The Design and Constnicfion of Power Work Boats
i-r;. 11— how external iouce causes heeled-over position
of buoyancy when heeled over and we see that a change in the form of a vessel's underwater body causes a shift of the center of buoyancy.
Now the force of buoyancy acts vertically upward through B' and is equal to the vessel's weight acting downward through G, which point is not changed in position. The two parallel forces are a distance of G Z apart and are called a "couple". They tend to rotate the vessel in a direction opposite to the motion of a clock's hands, or "counter clockwise", which in Fig. 11 tends to return the vessel to the upright. The magnitude of this couple equals one of the forces times the lever arm "G Z". Let W equal the vessel's weight (also the buoyancy or displacement in pounds or tons). GZ is in feet so when W multiplies it we have:
'jV>
I El
F1(J. 12— PATH UE WAIER ARUUNU A BOX-SHAPED HULL
W X GZ = the foot pounds tend- ing to turn the vessel upright.
This product is called the moment of "statical stability".
It will be noticed that the force of buoyancy intersects the vessel's cen- ter line at the point M which is called the "metacenter". The distance G M is the "metacentric height" and is a direct measure of the distance G Z. GZ
( = sine of angle GMZ)
CM
FIG. 13— GRADUAL STREAM-LINE OF A PROPERLY FORMED VESSEL
If M is above G the vessel tends to right itself and G M is called posi-
tive. When M is below G the couple is reverse in direction and would upset the vessel. G M is then called negative. This unstable condition can exist if the point G is high up such as with very heavy deck loads.
The method of calculating stability is too complicated for discussion in this article, but can be obtained by consulting Attwood's work on "Theo- retical Naval Architecture".
The box-shaped vessels we have thus far considered would carry a maximum amount of cargo with given limiting dimensions of length, beam and draft. Ease of propulsion plays, however, an important part in con- tributing toward earning capacity.
Resistance of the Movixg Hull
Figs. 12 and 13 illustrate the eflfect of hull form upon the resistance set up by the water when a vessel moves through it.
Looking down on a box-shaped moving boat, the arrows in Fig. 12 are the paths taken by particles of water which are deflected when the boat passes them. Notice the sharp right angle turn or sudden changes in direction of the particles' flow. These paths of flow are called "stream- lines". The sharp changes in direc- tion cause eddies at the two forward corners of the box form and also at the after portion.
Experience has shown that all changes in direction of streamlines should be gradual as in Fig. 13 and that a vessel properly formed will offset the loss in carrying capacity by the facility of propulsion.
Resistance to propulsion is made up of three distinct components:
(1) Surface friction or "frictional resistance" which depends upon the area of submerged or "wetted" surface and the smoothness and the rough- ness of this surface.
(2) Eddy making resistance, set up by abrupt changes of surface con- formation and is most serious at the after end of vessels.
(3) Wave-making resistance which is the power expended in generating the familiar bow and stern waves. This is affected by the form of hull and speed.
Sometimes wave and eddy-making resistances are grouped under the name "residual resistance". This is because frictional resistance is the only portion which can be fairly ap- proximated by calculations and if this is subtracted from the total resistance the result is the sum of wave and eddy resistances.
The power actually required to pull a vessel at various speeds, thus over- coming the resistances encountered, is the Effective Horsepower (EHP). Be- tween the machinery which generates the power and the propeller or pad- dle wheel which converts the power into thrust driving the vessel, there is mechanical loss due to friction in the machinery parts, etc. There- fore, the power at the engines must be greater than the E II P by the amount of this loss.
Indicated Vs. Brake Horscpoiver
When power at the engines is de- rived from indicator cards which show the work done by the gases in the cylinders, it is the indicated horse- power (I H P). If the engine power is measured by the actual torsion in the crank shaft it is called the Brake Horsepower (B H P).
Clearly the less power lost between engine and propeller, the greater the efficiency and a measure of this can be expressed by the ratio of EHP to I H P or B H P. This ratio is called the "Propulsive Coefficient" and is from SO to 70 per cent in ordinary vessels. Of course it will be higher when B H P is used than with I H P because there are losses in the engine itself between the power developed in cylinders and that delivered at the crank shaft. This engine efficiency B H P
(a ratio of ) should be from 80
I H P to 92 per cent. »
The surface to which a ship's hull is formed or molded is known as the "molded surface". It is parabolic in nature so that a section in any direc- tion between a plane and the surface is a parabolic curve.
If the hull is cut by a number of planes in various directions, the re- sulting curves of intersection between the planes and hull surface show the character of surface and may be used as a guide in constructing the vessel. The drawing so made is called the "sheer draft" or more often the "Lines."
Biiovnncv, Draft and Displacement
13
M AT AMEK— OWNED BY COPLEY AMORY, OF CAMBRIDGE, MASS. Used in I.abradore; 36 feet long by 8 feet 9 inches beam; driven by Lawley 2-cylinder, 4-cycIe engine
14
The Design and Constrtictioii of Power Work Boats
CHAPTER IV
Laymgf Down-Fairing tne Lines
HAST chapter we explained as simply as an intricate question will permit, the principles in- volved in designing a workboat hull. There are certain fundamental fea- tures of every successful power-driven boat which must be molded into a homo- geneous model, otherwise a boat ma}' be satisfactory in some respects and entirely lacking in other requisites of performance.
Now having mastered the principles of displacement, buoyancy, stability, etc., we will endeavor to apply them to the job in hand, of creating a design from which construction of the hull may be accurately carried out. Fig. 14 is the "Lines" for a SO-foot power tug and consists of three views; a longitudinal elevation, a plan view or "half breadth" and an end view or "body plan". The relative location of these views is conven- tionally arranged as in the figure with the forward part of the boat or the "bow" toward the right hand.
In the elevation and body plans a horizontal base line is drawn at the lowest point and all vertical measure- ments or "heights" are measured from this. This base line is really the edge of a horizontal plane and numer- ous other horizon- tal planes are shown at distances above it. These latter planes are as near- ly parallel to the load water line as can be estimated and are called "water plan es." They are labeled "2' 6" W L," "3' 6"W L," "Designed W L," etc., and ap- pear as St r a i g h t horizontal lines in the elevaticn and body plans. Where the hull is cut by water planes a series of longitudi- nal horizontal curves result. These c ur v e s can be shown onlv in a
plan view and are "water lines." They are labeled in conformity to the watei plane, which cuts them from the hull surface.
The upper hull limiting line is called the "sheer line" and may be curved or straight in elevation. It is usually higher at the bow than at the stern and if curved, its lowest point is at about one-third of the length from the stern, the line rising from this low point to the forward and after ends.
The plan view of the sheer line in the half breadth plan is widest and parallel to the longitudinal center line at about mid-length. From this it curves inward to the bow and stern respectively.
At the extreme ends in the eleva- tion two vertical lines are drawn and are the "forward" or "after per- pendicular" respectively. The distance between these is divided into ten or more equal lengths and perpendiculars are erected at the points of division. These vertical profile lines are the edges of cross sectional planes which are passed through the hull perpendi-
FIG. 15— VARIOUS FOKMS OF STEMS
15
cular to the base plane and the longitudinal center plane. The sec- tional planes intersect the molded hull surface in curves called "cross sections" which are shown in the "body plan" or end view.
The fullest of these sections is usually half-way between the end perpendiculars and is called the mid- ship section. Its characteristics are similar to Fig. 19, where the section intersects the half siding of the keel at the "rabbet line." From this lower point and depending upon the type of vessel, a "line of bottom" extends to the "lower turn of bilge". If the line of bottom is produced to the vertical line tangent to the widest point of the section, the height of the point where the two lines inter- sect above the lowest point of sec- tion, is called the "deadrise". Con- tinuing from the lower turn of bilge, the section rounds sharply upward to the point where it is tangent at the vertical line showing the maximum width. This vertical line is the "line of half breadth" and the maximum width of section to this line is the "m o 1 d e d beam." From the upper turn of bilge the section may be ver- tical to the point where it cuts the deck side, and a vessel with this type of section is called "wallsided." If the upper part of the section falls in from the upper turn of bilge to the deck at side, the amount of fall in from the line of half breadth is called the "tumble home." This fea- ture is not essen- tial to efficient de- sign, being retained mainly through the dictates of custom. The height from the point where the midship section intersects the keel
16
Tlic Design and Ccnstntction of Po7ver Work Boats
fSMER
CovnTEit
'SxX;y-^TEnN POST RUPDEn^fOST
^De/iDWooD <~BcTTCfi Of Kcei.
FIG. 16— VARIOUS TYPES OF STERNS
to the upper deck at side is the "mold- ed depth."
When the deck is rounded up or "cambered" the crown of deck at center above deck at side is usually to the amount of % inch per foot of deck width. This curvature may be more or less and is often entirely dispensed with. Its purpose is mere- ly to drain the deck, but since few vessels are on an even keel very often, camber can be omitted with attendant gain in simplicity of con- struction.
The sections forward and aft of amidships are finer than the midship section and it is desirable to have the forward ones U-shaped at their lower endings, while the after ones are V-shaped.
When a portion of the hull amid- ships has the same cross section as at the midship section, it is called the "parallel middle body" and it may be
as great as 60 per cent of the length. The hull forward of the parallel mid- dle body is the "forebody", that aft of the parallel middle body the "after body".
If a series of planes is passed through the hull at varying distances from and parallel to the vertical longitudinal center line plane, the intersections of these planes with the molded surface are curves shown in the longitudinal elevation as "but- tocks" and labeled "1' Butt", "2' Butt", etc.
Buttock planes appear as vertical straight lines in the body plan and as horizontal lines in the half breadth. The spacing of buttock planes should be the same as for water planes.
Fairing the Lines The process of delineating a ves- sel's molded surface is called "fairing the lines". When "faired", the lines should be smooth, pleasing to the
eye, free from sudden bumps or hol- lows and the volume of the under- water body should afford the proper displacement and location of the center of buoyancy under the center of gravity. Proper stability and trim are dependent on the lines. In gen- eral, the location of any point on the hull surface should be the same height above base line in elevation and body plans, the same width from the longitudinal center plane in half breadth and body plan, and the same longitudinal location in the elevation and half breadth plans.
A detailed description of the fair- ing process will be found in "A Manual of Laying Off", by Watson, while elaborated descriptions of displace- ment, stability and trim calculations are set forth in "Theoretical Naval Architecture", by E. L. Attwood. Forms for Bow or Stem
The bow or stem may have one of the forms in Fig. IS. (a) and (b) are "plumb stems" with rounded or abrupt forefoot. The former type is extensively used on tugs, lighters and other small vessels under ISO feet long. Its name is derived from the fact that the portion above the water line is vertical.
Fig. IS-c is a "raked stem", where the part above the water line slopes forward, (e) is the stem of a shal- low draft vessel, differing from the ordinary plumb stem by the wide for- ward deck end which is used to push barges, (d) is a rounded stem, curved from sheer line to keel and used in tugs or lighters. (f) is the spoon bow used in some shallow draft work. It has relatively high resistance and is less desirable than type (e) though simpler in construction.
Various types of after vessels' ends or sterns are shown in figures 16 and 17. Tugs and lighters have rounded sterns (Fig. 16-a) with a vertical sur- face between sheer and knuckle to which heavy fenders are attached. The rabbet line which was parallel to the bottom of keel amidships, rises at the after deadwood and merges into the counter. The structural appendages to which propeller and rudder are attached should be as narrow as prac- ticable to reduce eddying.
Fig. 16-c is an overhung transom stern, the transom being a transverse plant or cylindrical surface which may slope as shown or be vertical. Employed in auxiliary sailing vessels.
Fig. 16-b is the semielliptical stern used in large vessels. Fig. 16-d is the compromise stern not common to workboats because difficult to con- struct. It is popular in cruisers and now often adopted in large com- mercial vessels.
Fig. 16-e, the full transom stern is
Laying Doiuii and Pairing the Lines
17
used in small boats of all types. The transom may be flat, cylindrical or V-shaped.
Sterns for shallow-draft vessels are of the tunnel or paddle wheel type. Fig. 17-a shows the elevation plan and half section of a tunnel stern. It was originated by the necessity for a larger propeller than could be fitted under the hull with the limited draft. Consequently, a depression was made in the way of the propeller, as shown by the dotted lines in elevation and plan views. A cross section of the tunnel at any point in its length is the arc of a circle.
Fig. 18 is the outline in eleva- tion, plan and section of a paddle wheel stern. The hull terminates at the transom, as shown, while the pad- dle wheel is overhung on two or more girders.
When the proper stem, stern, mid- ship section and sheer line have been decided upon, they are drawn in on the rectangular layout of water planes, buttock and cross sectional planes in the line drawing.
Drazving in the Rabbet Line The rabbet line joining the lower end of stem with the stern is now drawn in the elevation. Its height above the bottom of keel amidships equals the depth of keel timber minus the thickness of garboard plank. The forward and after endings of the rabbet line depend upon the cross sections, but may be roughed in for final fairing later on.
A line showing the half width of keel, stem and deadwood is drawn parallel to the longitudinal center line in the half breadth and body plans. Then the width of forward stem
,VI*LHW^y
tLUVATIOh/i
K^
Section A-A
FIG. 17— ST1LRN.S FOR SIIAU.OW DR.\FT VESSELS
edge is indicated by a line at half this width parallel to the center line at the forward end of the half breadth plan. This surface on fore edge of stem varies from one-half "to three inches and serves as a backing for the half round iron bar which is screwed to it and protects the stem timber. All water lines end at this line forward and on the half siding of deadwood and keel aft.
A trial load water line is now drawn in the half breadth of proper width at the midship section and with forward and after ends fixed from the points where fore edge of stem and rabbet line are cut by the load water plane in the elevation.
Then two sections located midway between amidships and the ends can be derived from the half breadth by taking their widths on the trial water line and the sheer line. These widths are placed at the proper levels in the body plan, care being taken tliat the forward section is on the right and the after section on the left of the vertical center line. The height of sheer and of rabbet on these sections is measured from the eleva- tion.
Intermediate water lines are then drawn in the half breadth plan by taking widths from the three sections already shown in body plan, and by finding the forward and after endings in the elevation.
These water lines should always spring to a fair curve when using a slender wooden "spline" or "batten"
, WHfO.
FIG. 18— PAUDLE WHICKL STERN
which is bent through the points through which the line should pass. If this cannot be done, the batten should pass through a majority of the points and spring fair between them. The corrected line may then be drawn in and the width of section through whose spot the batten would not spring, should be made that of the fair line on that section and transferred to the proper water plane in the body plan. The section curve should then be corrected to pass through this new point and the other fixed points.
A buttock line half way between center line and molded beam line can now be drawn in the elevation, taking the heights from intersection of the chosen plane with the sections of the body plan and transferring these heights to their proper sections in the elevation. By squaring up from the half breadth to the elevation, the longitudinal locations of points where the water lines and sheer line cut the chosen buttock plane, it is possible to obtain the abrupt curvature of the ends of the buttock line.
Continuing this fairing process for the remaining water lines, buttocks and sections, correcting all unfair points as the work proceeds, the lines will finally be "faired".
Next the volume of displacement should be calculated as heretofore described and if the ship's weight is such as to result in proper draft and trim, the lines are complete. If this is not the case, the proper volumetric correction must be made before mak- ing the "'ofifset table" which gives the molded surface dimensions of all the lines.
A final check on the fairness is obtained by passing diagonal planes, shown in the body plan of Fig. 14. The slope of these planes is such as to be at nearly right angles to most of the sections and to cut the bilge of the midship section. Such a plane cuts a curve called a "diagonal" from
18
The Design and Construction of Poivcr Work Boats
the hull surface. Sometimes more than one diagonal is employed. The true shape of a "diagonal" is ob- tained by "expand- ing" the inclined plane into the horizontal. To do this, the plane is assumed to revolve about its intersec- tion with the lon- gitudinal center line plane, so that the curve is shown as it really ap- pears on the di- agonal plane. The exact distances from the center line are measured
TunBLB Hone: 3HECFI LiriB
CAMBrH
-ffABBET LirfS
<porTon OF HE£i-
'UPPER Tuffii ofBiloe
TVffff OF 0/t&£ OCAD ff/se
^SASE Li He
FIG. 19— ILLUSTRATING A TYPICAL BODY SPXTION
Dimensions of the different lines at the va r i o u s sec- tions are record- ed in three groups: those showing heights of sheer, buttock and rabbet lines above the base in the ele- vation ; those giv- ing widths of sheer, water line and keel from the cen- ter line in the half breadth and those giving true distances along the diagonal plane from the center line to each section in the body plan. All
along the diagonal plane to each lines, and the distances along the offsets are recorded in three fig- section in the body plan and are diagonal to these two can be ex- ures representing feet, inches and then laid off below the center line panded at the points so found in the eighths of inches. For example, in
in the corresponding sections on the half breadth.
half breadth plan. The offset table is used as a
The heights at which the inclined guide for drawing the lines in the
plane cuts the transom and the half boatyard to the full size of the ves-
siding of stem are transferred to the sel. This is done on a smooth floor
elevation and squared down to the called the mold loft and ensures elimi-
half breadth plan. This gives the nation of the inaccuracies which would
longitudinal location of the diagonal result if molds were made from the
endings at the transom and the rabbet original small scale line drawing.
the table on Fig. 14, the figure to the right of the word "sheer" and directly below "stem", is 9-1-0. This indicates that the stem is 9 feet 1 inch above the base line at the stem.
The profile and plan of stem and stern should be dimensioned in the elevation and half breadths, to estab- lish their true outline.
CHAPTER V
Stem, Keel and Stern Design
^>^^^^HE fore end of a vessel is a M C^\ ridge formed by the intersec- ^ I tion of the side surfaces, the
^•^^ structure consisting of a bar called the stem. This bar may be of wood or of steel in conformation to the material composing the hull. Attached to the stem are the side planking or plating, the longitudinal framing of the hull, the forward end of the keel and keelsons, and some of the ex- treme forward frames.
Stem construction for wooden ves- sels is shown in Figs. 20, 21 and 22.
Fig. 20 is the stem of a wooden tug between 90 and ISO feet long. The stem log is backed by an "apron", both timbers being fastened together with through bolts having counter- sunk heads riveted over ring wash- ers. Where the longitudinals end and at the deck, these bolts extend through heavy knees called "breasthooks". The lower ends of stem and apron are scarphed to the stem knee and its backing timbers (called the forward deadwood) as shown. In Fig. 22 the stem of a larger vessel, the deadwood is heavier; while in Fig. 23, the stem of a large vessel (250 to 325 feet long), the forefoot is formed by two knees scarphed to the stem, apron, keel, keelsons and filling piece, the whole being backed by deadwood timbers.
Fig. 21 is the stem of a small ves- sel or shallow draft one with model bow. The stem and keel are con- nected by a natural crook knee, mean- ing one in which the grain follows a curve. These knees (formerly of hackmatack but now frequently of locust, oak or fir), are cut from tree
Stopwatar
FIG. 21— STEM OF A SMALL POWER WORKBOAT
stumps, one arm of the knee being in the lower extremity of the trunk and the other in one of the large main roots diverging therefrom. The single knee forefoot is applicable to ..mall vessels only, being limited in use by the maximum size of knees available. It is unusual to obtain these with arms longer than 6 feet.
(A-A), (B-B) and (C-C) in Fig. 20 are cross sections at various points in the stem structure. The hull plank-
frames are notched into the dead- wood as in section at frame (1), Fig. 23.
The construction of a "spoon bow" for shallow draft vessels is as indicat- ed in Fig. 24. One or more heavy "bow timbers" extend across the for- ward hull end, being scarphed to receive the deck, bottom and side planking. The trusses ordinarily built into the shallow hull for longitudinal strength, terminate against the bow
^Rabbet Line 'SBsaiStprr) Bo
'and
C-C
FIG. 20— STEM OF A WOODEN TUG
ing joins the stem and keel at a recess or "rabbet", the intersection between outside of plank and side of keel or stem being the "rabbet line". In large wooden vessels with "mod- el" or ship-shaped forms, the stem is arranged somewhat as in Fig. 23. Apron and stem terminate at their lower ends in scarphs bolted to knees and deadwood. The keelsons and keel scarph into the after knee, while the space between end portions of these and the knee is fitted with a filling piece. The extreme forward
i'op Wafer
■Sropy^ai'^''
FIG. 22— STEM OF A LARGE VESSEL 250 FEET LONG
timbers; while the space between these timbers and the first beam and floor, are fitted with filler pieces. A filler is also fitted at the intersec- tion between upper and lower chords (if the dimension "d" is small enough to bring this about).
Auxiliary sailing vessels are fitted with "clipper stems" afifording a maximum outreach for the forestays with increased jib areas. Fig. 25 indi- cates construction of the upper part in wooden clipper (or overhang) stems.
Keels form the strong center line girder connecting lower extremities of stem and stern post. Since their function is contribution of longitudinal strength, it is essential that their structure be continuous. In wooden vessels this feature is particularly necessary but is prohibited by limited lengths in which timber is obtain- able. This in turn varies with kind of timber.
Oak formerly was almost altogether used in keels. Oregon fir now has become popular, principally because of its large sizes, long lengths, strength and durability.
19
20
The Design and Constnietion of Power Work Boats
When the vessel is of such size that a continuous keel timber is un- obtainable, two or more lengths are "scarphed" together as shown in the longitudinal section of Fig. 26. The "hook scarph" here shown is securely
Fig. 27. An intercostal filler is lilted Figs. 31 to 36 inclusive are various
lietween keel and keelsons while the types of sterns in wooden vessels,
frames have no joint in the center An auxiliary schooner or large cargo
line. The lower keelson is shown carrier (ISO to 300 feet long) may
notched over the frames. have an overhung transom stern
Fig. 28 is the keel and keelson of ('■'S- 31). The keel extends beyond
a wooden tug with continuous trans- ^^^ rudder post, forming a lower
verse frames; while Fig. 29 is a step-bearing for the rudder. Both
similar detail of boats 50 to SO feet s'^""" ^"d rudder posts mortice into
The keelson in the latter is '^e keel, the "shoe" between their
long.
directly on the keel, forming there- with a rabbet and having the frames butted on the center line. Additional longitudinal strength is contributed by the engine keelsons which are notched over the deep transverse
FIG. 23— STEM OF A LARGE WOODEN VESSEL
FIG. 24— CONSTRUCTION OF SPOON
fastened with countersunk head bolts with ends riveted over ring washers, the recesses at bolt ends being plugged in white lead. (Fig. 26-a.)
Fig. 23 shows a cross section and a longitudinal section of the center line hull bottom girder formed by conjugation of the keel and center line "keelsons". The five keelsons (as large as 18 x 18 inches each) are bolted together horizontally and ver- tically, their scarphs being spaced well apart to avoid excessive weaken- ing, l-ong vertical bolts (b) pass from keelson through the double frames to the keel. Shorter tlirough bolts connect keelsons to frames out- board of the keel. The false keel is spiked to the keel proper over the metal hull sheathing and is read- ily detachable when worn.
The extra heavy planks adjacent to the keel and called the "gar- boards" are sometimes rabbeted in:o the keel (Figs. 27, 28 and 29) or they may be fitted closely against the keel as in Fig. 26. Where garboards are of considerable thickness, they may be edge bolted to the keel.
At points where scarph joints cross the rabbet throughout the stem, keel and stern, wooden plugs called "stop- waters" are fitted across the joint (Figs. 17 to 23 and Fig. 26). These prevent entrance of seawater through the joint into the hull.
The keel of a wooden schooner, 110 to 160 feet long, is shown in
lower ends being reinforced by nat- ural crook knees which form the lower arch of the propeller aperture.
The line of counter is formed by
a heavy "horn timber", morticed to
take the upper end of the stern post
floor timbers and extend as far fore and to permit passage of rudder post
and aft as practicable. and stock. The forward end of horn
Shallow draft vessels may be as in timber extends into the hull and is
Fig. 30 or the keel may be of same securely bolted to the deadwood and
shaft log, against which it terminates. Notice the way the beveled ends of all timbers are cut to prevent feather edges. At its upper and after end the horn timber is let into the knuckle timber (Fig. 31), or the rim logs (Fig. 32).
The propeller shaft passes through a hole cut in a "shaft log" which has a stuffing box at its inboard end and is morticed to the sternpost at its outer terminus. Great care must be observed in boring out the shaft log, particularly if it is long, so that alignment with machinery may result. Sometimes it is made in halves (sec-
U(JW FOR SHALLOW DRAFT BOATS
thickness as remainder of bottom planking. The reduction in strength is justified by considerations of draft
increase of interior hull strengthen- ing.
Drainage of bilge water in all these types is effected through "limber holes" cut in the frames as shown. Galvanized "limber chains" pass con-
and is reimbursed by corresponding tion "A-A" Fig. 32), facilitating this.
All such joints must be well coated with thick white or red lead and securely bolted. Shaft logs may be lined with a lead sleeve bedded in white lead and flanged at the extremities under flanges of stuffing box and stern bearings. Ordinary pipe may be used here and threaded into the fittings at its end, sufficient clear- ance about the shaft being provided to insure against binding.
The frames whose lower ends con- verge at acute angles at the stern are let into deadwood timbers and secure- ly through bolted. Abaft the stern- post they butt against the horn tim- ber, which is rabbeted to take the
FIG. 2,i— CLIPPER STEM OK Al'.XlI. lARY SAILING VESSEL
Limber St,
7rornav6r3e ■5e>ofian
Lonijiucllnal Sccticn
FIG. 26— CON.STRUCTION OF BOTTOM GIRDER OF LARGE WOODEN SHIP
hull plank ends as indicated in Fig. 31. The upper end of rudder post is securely bolted to the deck beams and forms the forward side of a watertight box or "rudder trunk" through which the rudder stock passes to the quad-
tinuously through these holes so that when drawn back and forth the holes will be cleared of clogging matter. The "limber strakes" fitted in the ceiling of large' vessels afford access to the limber holes.
Stem, Keel and Stern Design
21
rant or tiller. A stuffing box em- braces the stock at top of trunk un- der the "rudder support bearing" which carries the weight of the rudder The trunk is large enough to permit unshipping the rudder.
"hrouqk'Bol+'-
FIG. 26a— HOW KEEL BOLTS ARE COUNTERSUNK
The rudder blade is formed by heavy timbers fitted as shown and edge bolted together. Metal straps assist in tying them together and are formed into sockets at their forward ends. Hinge bolts or "pintles" fit into these sockets or "gudgeons" and corresponding ones on the rudder post, the gudgeons sometimes having me- tallic bushings. Notice that the rud- der stock extends in one piece to the keel. Where this is impracticable the two lengths should be securely scarphed. Lugs called "stops" on the rudder post should bear against sim- ilar ones on the rudder stock, pre- venting a rotation of more than 45 degrees on each side of center line. Rudder chains, shackled to an eye on the rudder blade are led to pad eyes on each side of the stern and serve as emergency stops in event of breakdown.
Between the knuckle and upper deck, transom frames are fitted as in Fig. 31, the transom planks extend- ing athwartships being fastened there to. The outline of transom forms a knuckle and a heavy timber conforms with it, being scarphed to take the ends of the hull and transom planks. The knuckle timber and rim logs (Fig. 31) form parts of this transom margin log.
Tugs and power lighters have us- ually but one deck and a semi-elliptical
Tfobbct
FIG. 27— KEEL OF A WOODEN SCHOONER
Stern whose general construction is as heretofore described. In Fig. 32 the main point of difference is at the deck where heavy rim logs are shown and a guard timber is securely bolted to these. The rudder stock passes
through the deck and is covered by a grating upon which Iiawsers are stowed. Sometimes the quadrant is below decks. Sterns of this type are common to tugs and lighters be- tween SO and ISO feet long .
Full transom sterns (Fig. 33) are common to small craft of all descrip- tions up to 80 or 90 feet long. The transoms may be variously formed as previously described but the same general construction applies for all of them. Keel, deadwood, shaft log and horn timber have already been con- sidered, except that where a metal rudder is fitted the shoe is formed by a casting as shown.
Hechon
Rabbtt
FIG. 28— KEEL OF A WOODEN TUG
The rudder stock passes through a lead-lined opening in horn timber and bearing log. A natural crook knee connects horn timber keelson or stringer ends to transom framing. Cheek plates are sometimes fitted over the junction of shaft log and deadwood with sternpost.
The proper rudder areas for vari- ous small boats will be considered under steering gear. In event of breakdown to this gear a spare tiller may be inserted through the deck plate shown in Fig. 33 and fitted over the square rudder head.
^Enain
HcalsonS
FIG. 29— KEEL OF A 50-FOOT WORKBOAT
Transom sterns properly formed are desirable for the additional hold storage space, the wider deck, the tendency to prevent squatting when under way and the facility of con- struction. They do not render a vessel difficult to steer nor make her uncomfortable in quartering seas unless they are extremely broad and flat underneath.
Compromise sterns (Fig. 34) are seldom fitted to commercial power boats. They are similar in structure to the stem, having a central ridge formed by the horn timber, a knee and the stern log. The planking scarphs to these timbers and care must
be observed that the plank ends fit properly and are not too narrow. The flat iron shoe shown in Fig. 34 is not recommended but is indicated merely as common in pleasure boats. Such a shoe affords little protection to the propeller since it is liable to distortion on contact with submerged obstacles, in which case the rudder may be thrown out of alignment or twisted and jammed.
Shallow draft sterns with stern- wheels are as indicated in Fig. 3:. The flat bottom planking rises to a transom whose lower edge is at or near the water line. The hull is not pierced as in vessels formerly con- sidered but rudder stocks extend up to the house deck as shown. Bearings at the transom and house decks support these stocks and the tiller arms are linked together over the house or "texas".
Multiple rudders are necessary be- cause of the limited draft and un- wieldiness of the boxlike hull. The forward upper edges of these rudders are very close to the bottom planks so that obstructions cannot wedge
l«*4«\/^
ri/ss
Gorboard
FIG. 30--KEEL OF SHALLOW DRAFT VESSEL
themselves between rudder and hull. Details of construction will be consid- ered under steering gear.
The stern wheels, whose details of construction will be later taken up, are supported upon two or more overhung girders whose inboard ends securely bolted through the main deck to the longitudinal trusses in the hold. If the continuous trusses do not end under these girders it is necessary to provide auxiliary trusses or other reinforcing. The extreme outboard ends of wheel girders are connected by a heavy transverse tim- ber and walkways are provided out- side of the outer girders to facilitate inspection and repairs to the wheels.
Vibration is minimized by hog posts and tie rods as shown which form part of the longitudinal strengthening truss above the hull necessary in these shallow hulled boats.
The paddle wheels revolve in a clockwise direction, dip of the buckets being fixed by vessel's draft, but sel- dom exceeding 27 inches. The after deckhouse bulkhead is termed the "splash bulkhead" and is watertight.
22
The Design and Coiistniclioii of Fotver Work Boats
imrm
VJ^^
*^tal3e teel
7ov
'Shoe FIG. 31-OVERHUNG TRANSOM STERN OF AUXILIARY SCHOONER
The wheel shaft bearings fitted on each girder are bolted to timber pads. Wheel girders are designed as canti- levers to take the wheel weight but a high factor of safety must be em- ployed to allow for the vibrational stresses. At the same time these overhung weights are not directly sup- ported by buoyancy so that care must be taken not to trim the vessel by the stern. In most cases it is necessary to locate the engine and fuel tanks well forward to oflfset the stern weights.
Propeller-driven, shallow-draft boats are very successful if properly de- signed. Their advantages over stern- wheel vessels are reduced machinery weights, less difficulty in obtaining proper trim, improved maneuvering qualities, greater free deck space and compactness of hull appendages. Higher speed of the propeller permits of lighter and better balanced machin- ery for the same power.
Fig. 36 is a longitudinal section through a wooden tunnel-stern vessel;
Fig. 37 ("a" and "b") are two cross sections at "A-A" of Fig. 36 for dif- ferent tunnel constructions. Two or more propellers are necessary since the limited draft cuts down permis- sible diameter and the total thrust area must therefore be distributed.
The tunnel should be a smoothly scooped out recess in the vessel's bot- tom and the propeller tips should fit into this with minimum practicable clearance (J/2-inch if possible). The highest point of tunnel should not be more than one-third the propeller diameter above the water line and the after end should just touch the water line at the stern. If this is not practicable, a vertically hinged flap should cover the after tunnel end, opening with the stream flow when going ahead. This is to insure good backing qualities, the water filling
Full Transom SrrRN
■■5 pare Ttilc-r
FIG. 33— TRANSOM STERN FOR SMAI.I.
r.OAT WITH METAL RUDDER
fcalcuart t-ail
FIG
STERN OF TUG OR LIGHTER WITH SINGLE DECK AND GUARD TIMBER
^—F/of Iron Shoa FIG. 34— COMPROMISE STERNS SELDOM USED ON WORKBOATS
the tunnel when flap is forced closed by astern motion.
Cross sections along the tunnel should be circles with varying diame- ters and their upper points in the longitudinal profile curve of tunnel.
Workmanship in wooden tunnel sterns must be of highest class, since smooth water flow is essential and leak- age is likely due t > complex struc- ture.
In Fig. 37-a the tunnel is merely a watertight box with arch beams to whici! is fastened a metal fairwater top ; 37-b has the tunnel formed by bottom planks which are cut and bent into place, calked and fastened to arch beams inside the hull.
Sinn, Kci'l and Stern Dcsiyii
23
u J u J u u u I
Stern
=^-/~^.-lL,^'
■iT-^'i— TT- ill! I|
^y^^^i^
'" "
/ ^Multiple ^Dsodwood \^ottOrn
FIG. 35— SHALLOW DRAFT STERN WITH STERN WHEEL
II II
JM- 'ilk kb ' *f' *t '
oHorn
IUNN£.L St£RN FIG. 36— LO\G[TUniNAL SECTION OF WOODEN TUNNEL STERN BOAT
Co)
(Tunnel ■^ICol-hns
/
Jection Tti hough Tunnll Sterns
FIG. 37— GROSS SIXTIONS SHOWING DIFFERENT TUNNEL CONSTRUCTION
24
The Design and Constntction of Power Work Boats
KAMCHATKA— A SAILING VESSEL RECENTLY CONVERTED INTO AK AUXILIARY FOR USE AS A WHALER IN THE
ARCTIC OCEAN AND BERING SEA
144 feet long by 31 feet beam by 15-foot depth. Fitted with a 300-horsepower Macintosh & Seymour diesel engine, which drives her at 7'/i knots loaded. Two auxiliary engines, one 25 horsepower Burn-Oil, and a 20 horsepower gasoline engine installed.
CHAPTER VI
Application of Steel Construction
long.
^TEEL construction as here considered will be limited to practice in commercial ves- sels between SO and 250 feet Bar stems are ordinarily fitted in these and are scarphed to the plate keel or bar keel as in Fig. 38-a and b. The length of these scarphs is nine times the thickness of bar stem and keel and the scarph faces are machined to fit closely together (Fig. 38-6). The shell plating is flanged to the stem and is connected thereto by through rivets with countersunk heads. In small ves- sels a single row of rivets is used but in vessels more than 75 feet long two rows of zig-zag rivets are employed. When bar stems join a plate keel (Fig 38-0 ) their lower ends are flattened out and riveted thereto (Section Frame 2). At one-twentieth of the vessel's length from the stem a transverse watertight bulkhead extends from side to side and from keel to upper deck. This is the "forepeak" or "collision" bulkhead and the space between it and the stem is the "forepeak".
Deep transverse floor plates whose upper edges are stiffened by the reverse frames, connect the lower ends of frames and are cut to permit passage of the center keelson plate and angles (Sec- tion Frame 2). Where longitudinal gir- der angles (called keelsons or stringers,
according as they are on the vessel's bottom or sides), join at the stem, they are connected by horizontal bracket plates or "breasthooks" which are con- nected to the hull plating between frames by short "shell clips" and have their
after edges stiffened by an angle. Large breasthook and floor plates are pierced with "lightening holes" cut from the least affected part to reduce the weight. Limber holes drain the spaces between floors (Section Frame 2).
FloorPlcr^^ci+f
Gorboard StraK«>
Keelson Plo*6
) Qt-boord Stroke,
"iSide Bar Keel
'Bacboard Plote Kee.1 PI 0+6
(b) Co)
FIG. 39— THREE TYPES OF KEELS OF STEEL VESSELS
Floors
, Ke«ldon IS
"P/ frame Keels
Fowndift'ion "Plate
lonTlate CUpi To Flo<7r6
Limber Hole
FIG. 40— METHODS OF FITTING KEELSONS
KeeliOM cups To F\oors.
'Foonddftic>r\'T\a\-e
Bar S+er
3c'C.tion
Fra me Z ^/cufei He.e>l ^Bci^ Stem FIG. 38— BAR STEMS AND METHOD OF SCARPHING
Keels of steel vessels are of three types: plate, bar and side bar (Fig. 39- a-b-c). Plate keels are common to large steel vessels and to those of shallow draft.
Bar keels are used in tugs, power lighters and in general for vessels up to ISO feet long.
Side bar keels are not extensively em- ployed due chiefly to the difficulty of obtaining good rivet connections through the five thicknesses of metal (two gar- board plates, two keel bars and the center keelson plate).
The Center Keelsons
Center keelsons form a girder with the keel and their construction is affect- ed by the size of vessel together with the method of making connection with transverse "floor plates" which are a part of the framing and will be later discussed. With respect to these
25
26
Tlic Design and Coustriiiiiou of Pozvcr Work Boats
Siringftr A^^^le-
FIG. 43 — CONSTRUCTION
OF OVERHUNG TRANSOM
STERN
Knuckh r^udd&rTruriK
I? dddfrf Coupling. f7udd&rFrafTn
-Snoe
"floors", keelsons may be built above them and extend continuously fore and aft; the floors may be cut at the cen- ter line to admit a continuous plate keelson extending down to the keel ; or the keelson plate may be intercostal be- tween floors, with continuous keelson angles on top of floors.
Fig 40-a is a continuous keelson on floors, attachment to upper edge of floor plates being by rivets through the re- verse frames on one side and a clip on the other side of plates.
The keelson may consist of two angles, as shown; of two bulb angles, four angles with a rider plate over the upper ones, whose long flange is horizontal, or four angles with a "foundation plate" under the lower angles and on top of floors, a rider plate being fitted over the upper angles.
When through keelson plates of floor depth are fitted (Fig. 40-6), the upper keelson angles may be above the floor tops, or (in small vessels) below this level. The upper part of keelson girder may vary in structure as did the type entirely above floors. Double clips are always fitted connecting the keelson and foundation plates to the floors. When a bar keel is employed the lower edge of keelson plate butts against it without angle connections. In the case of a
Lficai-pul '~Rot«.He*l
Asttt-fi/aK Bulhhcad
1 C_ From} to, R
Sten
plate keel this is connected to the keel- son plate by continuous double keel angles (Fig. i^-c).
Fig. 41 shows a center keelson with intercostal plate and continuous upper
Ivinet BoM-orM
■Vivtrie finable
Foojndatton ,_, ^j/
Floor
FIG. 42— TRANSVERSE SECTION OF DOUBLE BOTTOM
angles. The intercostal plate is in sec- tions of frame space length which are cut to pass the frames and heel pieces at keel and the reverse frames and re- verse frame clips at floor top. With bar keels there is no lower keelson plate
/Plate
-e\ate.
Jy,terco6tal ■<ee\ '^'"'^'fitir^ I III 1 ' i-i I
^
connection, but double intercostal keel angles are fitted with plate keels.
Tanks built in the ordinarily wasted space below floor tops are used for fresh water, fuel oil or ballast water. The floor tops are plated over by an "innerbottom"' or "tank top". Center keelsons in these "double bottom" com- partments are composed of continuous girder or keelson plates with double keelson angles and top angles to the inner bottom plating. Fig. 42 is a trans- verse section through a keelson in dou- ble bottoms. Generally double bottom tanks e.xtend the full vessel's length be- tween peak bulkheads, but often they are limited to spaces under machinery compartments. When this is so the keelsons outside of tank are of the con- structions in Figs. 39 to 41.
Steel sterns applied to commercial power craft are ordinarily limited to those in Figs. 43 to 48 inclusive.
Passenger and cargo or au.xiliary sail- ing vessels may be fitted with semi- elliptica! or overhung transom sterns (Fig. 43), where the transverse framing extends aft to the "transom floor", which is a deep vertical transverse plate against which the upper end of rudder
rBulivark Rail
Bulwcurki
BulwarK BracKet ' or f offlcd S-t-gy JBitt_liM_WH mi Ml
awser Sraiin^
c«ci ■piate Keel ^
FIG. 41~CI-:NTER KEELSON WITH I.NNERCOSTAL PLATE
FIG. 44— ATTACHING GUARDS AND RAILS
post is clipped with double angles. The rudder and stern posts, connected at their tops as shown and at their lower ends by a "shoe", form the "stern frame" forging. This is scarphed at its forward end to the plate or bar keel, tapering down to the horizontal plate connection in the former case and being connected as for stems in the latter instance. This keel scarph should begin at least two and one-half frame spaces forward of the stern post which is "bossed" to permit passage of the cen- ter line propeller shaft, which passes through a cast steel stern tube to the after peak bulkhead, where a stuffing box is fitted.
When twin screws are fitted no screw aperture is necessary unless the pro- peller tips overlap at or C(jme close to the center line. Fig. 45 is a twin screw frame and indicates the forged stmt which supports each wing shaft.
The shoe under the propeller aperture is of flattened elliptical section and ex-
Application of Steel Constniction
27
tends beyond the rudder post to form a step bearing for the rudder.
Forged to the sternpost are eyes or "gudgeons" which receive the pintles about which the rudder hinges and which may l»e bushed with metal or lignum vitx wood. At the upper end of the rudder post, heavy lugs are forged to form "rudder stops" which prevent greater angular swing than 45 degrees.
Large vessels have their rudder stock coupled to the blade, as in Fig. 43, this connection being a horizontally or verti- cally transverse flanged or a scarphed joint.
Rudder Construction Double plate rudders (Fig. 43) con- sist of a forged or cast frame with plates riveted on each side and the in- tervening space filled with pine well coated with pitch or other preservative. Single plate rudders (Fig. 45) are com- posed of one plate riveted to forged arms on the rudder stock.
■Bo++oin Plafm^
FIG. 46— ELEVATION AND PLAN OF STERN WHEEL VESSEL
or serve as a trimming tank when filled with or emptied of sea water. Fantail sterns are similar in construc-
the vertical distance between deck and knuckle is just sufficient to attach the heavy guard shown in Fig. 44. Being common to tugs and lighters and con- sequently constructed for towing, a bulwark rail strongly supported by forged stanchions or brackets is fitted. The tiller or quadrant cannot usually be installed below deck due to lack of space, and is therefore covered by an ash grating upon which hawsers may be coiled when not in use.
Shallow draft sternwheel vessels have the same characteristic construction as was pointed out under wooden hulls, and Fig. 46 is an elevation and plan of this type.
A tunnel stern (Fig. 47) has the bot- tom plating dished to the tunnel con- tour and the bottom angles forged in conformity. It is much more readily and simply fitted in steel than in wood- en vessels. The stern casting shown All rudder heads must pierce the hull tion to the overhung type but differ at flanges to the outside of tunnel and has
Rodde*-
Plo\Te»
FIG. 45— CONSTRUCTION OF RUDDERS AND STRUT BEARINGS
through some form of watertight box or "trunk", at the top of which is a stuffing box and the rudder support bear- ing, surmounted by the steering arm or quadrant. This trunk is connected to the afterside of transom floor and shaped to permit unshipping the rudder. The side and top trunk plates are con- nected by forged angles caulked water- tight.
Aft of the transom floor ordinary transverse framing is supplanted by ra- diating "cant frames" and beams, strongly bracketed together and at their forward ends to the transom beam and floor. Cant frames are spaced around the knuckle at intervals equaling the ordinary frame spacing amidships.
A watertight "flat" or short deck usually extends from after the peak bulk- head to sternpost, the space beneath which is too fine and congested for cargo stowage and is termed the "after peak tank." It may store fresh water
the deck marginal connection, where a bearing at the after end with the
FIG. 47— HOW THE BOTTOM PLATING IS DISHED FOR TUNNEL STERN
--i-vHK--L L
FIG. 48— STERN (OR BOW) OF DOUBLE ENDED STEEL FERRY BOAT
28 The Design and Construction of Power Work Boats
usual stuffing box inboard. frames need not be fitted though they der. In such a case the rudder may be The stern (or bow) of a double-ended sometimes are, particularly in wooden formed to fair into the normal hull sur- screw steel vessel, such as ferry boats, vessels. Heavy longitudinals should, face, but this is an unnecessary elab- is shown by Fig. 48, the peculiar con- however, be introduced to absorb the ^^^j|^^ ^^^ forward rudder is al- tour of stern frame being the only rad- end thrust in docking. When side pad- . > . . ,• ■ ^ l ical departure from ordinary stern con- die wheels are employed the screw aper- ^^^^ ^'^^^'^ °" *^^ «"'^'" ''"^ ^"^«'' ^^ struction. Because of the relatively ture is dispensed with and the sternpost =» through pin from the deck or by lock- wide ending of deck in this type, cant is located close to inboard edge of rud- ing the rudder stock.
CHAPTER VII
Wooci and Steel Transverse Framing
CHE watertight hull cannot be made sufficiently thick to with- stand longitudinal, transverse or local stresses, for the light displacement would be thereby in- creased to an uneconomical degree; even assuming that the required strength could be brought about by such cumbersome construction. An inner system of framing accordingly has been introduced to suitably re- inforce the skin and is called the framing.
It can be readily seen that this framework must run both longitudi- nally and transversely, and that one system must be predominant because of structural limitations. Now the most severe strains are ordinarily longitudinal in character, which would make it desirable to run the princi- pal framing in fore and aft directions. This is practicable in steel and small wooden ships, though the construction is complicated by the warped and refined hull surface at the vessel's extremities.
(a) Wood Framing
Large wooden vessels (100 feet long and above) cannot be rigidly constructed with longitudinal frames because the framing timbers are rela- tively short, the end connections be- tween timber lengths weak, the tim- bers cannot be suitably bent and beveled without serious loss of strength by cutting across grain, and finally the planking which is in nar- row strips could not be properly fast- ened. To run this hull planking trans- versely would seriously increase the resistance and result in loss of strength by the already comparatively weak structure.
Framing of Wooden Vessels
The transverse framing of large wooden vessels is similar to Fig. SO. Here the frames, relatively heavy tim- bers, are sawn to shape and fitted in two thicknesses (doubler), with butts of sections in each thickness stag- gered with those of the adjacent mem- ber of that frame. Butt joints at the center line are avoided and the molded dimensions of timbers (that measured
in the vessel's transverse planes) may be constant or gradually decreasing from keel to frame head at upper deck. The two sections of each frame
FIG. 49 — CONSTRUCTION FOR TUGS AND POWER LIGHTERS
are bolted together. Sided dimensions of frames (measured in fore and aft direction) are usually the same from keel to head.
Except at the vessel's extreme end, all frames are perpendicular to the keel. At the ends where the inward curvature of water line would entail extreme bevel with accompanying loss of frame thickness, the frames are placed nearly at right angles to most of the water lines. These radiating frames, called "futtocks", are shown ir Fig. 50 (a), which is a plan view of the vessel's end framing with the ceiling and longitudinals omitted.
When wooden bulwarks are fitted, one of the double frame heads passes through the deck margin planks to form a bulwark stanchion. Every al- ternate or third frame is thus ex- tended.
Frame heads are connected to the deck beams by continuous longitudi- nal clamp and shelf timbers, as shown.
In wooden construction the deck beam ends do not always butt against nor lap on the frame heads, though this should be so if practicable. At least every third or fourth beam should be directly connected to frame heads by heavy natural crook timber knees the intermediate beams landing on the clamp and shelf which are through bolted to these and the frame heads.
29
Limber holes must be cut at the lowest point of frame heels providing longitudinal drainage for bilge water to the pump suctions. In wooden ships limber chains are fitted in these holes.
Tuys (Did Power Lighters
Tugs and power lighters have mid- ship sections similar to Fig. 49. The frames cross or are butted at the center line, tapering to reduced molded dimensions at the deck. Ex- cept in extremely light construction, frames are sawn in sections with double timbers and staggered butts, through bolted longitudinally. Light frames may sometimes be bent to shape but this is not practicable with large timbers which tend to split and are stiff. Bending is preceded by steaming the timber in a box and then forming it to the proper crook. Frames in shallow draft vessels are straight on the bottoms and sides, butting against a timber called the "bilge log" at each bilge. (See Fig. 5L) Where considerable deadrise exists and always in the machinery space, heavy transverse floor timbers should be fitted at the lower point of frames on center line. These floors are sometimes introduced all fore and aft. Wooden deck beams extend in one length from side to side except where hatches or other deck openings neces- sitate cutting them (Figs. 49 and 50). In this case the resultant "half beams" are butted against or mortised into heavy longitudinal "carlins" which bound the opening.
The weather deck beams are some- times sawn to a camber on their up- per edges, the lower edge being flat and the ends reduced in depth. When beams are light enough to permit, they may be steamed and bent to cam- ber. The outer ends of beams should be notched over clamp timbers and kneed to frames, as previously de- scribed. Inner ends of half beams where the stanchions are fitted should have a natural knee.
Hold beams consisting of heavy double timbers widely spaced, are in- troduced in larger vessels. The beam ends bear on hold stringers or shelf
30
The Design and Conslntction of Pozver Work Boats
ffail Leg
Oul itrtrh 3tQnth\or\
Filhng Block Qetweeit Frame Hca/i
FmURE A-S-(h)
Hull Plank
FievttE 49 fi)
FIG. SO— TliANSVICKMC ]■ lIAMINr,' UK L.MMilC \\(10i)i:.\ VESSKLS
and cianip, to which they may be necting upper end of frames to deck kneed in vertical and horizontal direc- beams, deck beams and stanchions tions. Where stanchions mortise supporting these.
through double hold beams, metal Frames may be one of the various
cheek straps should be fitted (Fip. 50). structural shapes shown by "Sections
Stanchions supporting the uccks at A-A" Fig. 52. Angles and channel are fitted in wide vessels and deep holds. They should always be on a frame and their lower end or "heel" should bear on a keelson and have wooden knees. Sometimes a forged metal strap is employed at heads and heel connections or the heel may notch over a keelson and be through bolted. (Fig. 49.)
Stanchions should always be fitted at each corner of large deck openings
KIG. 51_FR.\MES FOR .<^II.\M.O\V DRAFT VESSELS
center keelson, and were shown in diagram of the latter. When floors are not cut at center lines the frame heels butt at this point and a heel bar 3 feet long is fitted on the oppo- site side of floor.
Good Riveting is Essential
Reverse frames which stiffen the inner edge of frame angles and ex- tend along the floor tops on side opposite to frames, form an inner flange to which keelsons, stringers and other members may be conven- iently attached. The overlap of frames and reverse frames should be suffi- cient to ensure good riveting. When frames are of bulb, channel or zee section, reverse frames are fitted on upper edge of floor plates only, but ordinary angles and reverse bars are used at the ends of the vessel where the channels and "Z" bars would be difficult to bend and bevel.
Reverse frames at floor tops are single except under machinery foun- dations where they are doubled. At the vessel's ends it is necessary to keep the athwartship frame flange in a transverse plane and to bevel the shell flange in conformation to the hull form. (Fig. 52.) This bevel should always be "open", that is, the angle between flanges should never be less than 90 degrees. This is es- sential to good riveting. The lower ends of frames at the vessel's bow and stern are lapped at the keel and riveted together.
Tlie bending of steel frames to proper contour and bevel is per-
and to every third intermediate frame '^^''^ ^""^ most frequently used. They formed by means of templates as
at hatch cabins. The upper ends or "heads" should be strongly kneed to carlins and deck beams.
When fitted in holds, stanchions should support adjacent beams through a longitudinal girder fitted at heads. (Fig. 51.)
In shallow draft hulls the hold depth in proportion to beam and length renders it imperative to intro- duce strengthening "trusses" running longitudinally and athwartships. In these trusses the girders at stanchion heads and keelson at heels are termed the upper and lower "chords". Diag- onal tie timbers serve as compression members against racking. (Fig. 51.)
The longitudinals are from one to four in number depending on the beam. Transverse trusses or simply "transverses" are at every tenth or twelfth frame.
(b) Steel Framing
Fig. 52 is the midship section of a steel tug or lighter. The transverse framing is composed of frames ex- tending from keel to deck, floor plates at keel, knees or beam brackets con-
are spaced from IS to 27 inches apart guides which are secured to a heavy
and are in one length from keel to cast metal slab. The frame bar is
deck. Frame ends at keel are de- heated, placed on the slab and bent
pendent upon the type of keel and against this template, the standing
I An^le.
^Fi^au- Channt,!-. fVoct-ttor Srtaptt
FIG. 52— MIDSHIP SECTION OF STFJ^L TUG OR LIGHTER
Wood and Steel Transverse framing
31
(lange being properly beveled at the same time. Spring "clogs" of round bar iron clamp the horizontal frame flange to the "bending slab" being driven into square holes closely spaced in the slab. Bevel templates of light wood or metal, cut to the proper slope which has been obtained from the lines, are used as guides in prop- erly beveling the standing flange.
Machines for bending and beveling structural shapes have been employed successfully in many shipyards.
The shell flange of frames must bear directly against the hull plating and since the longitudinal strakes of this are usually lap jointed, it is clear that either the frames or plates must be joggled (Figs. 52 and 53).
The practice of bending frames to a fair curve and fitting liner pieces between shell flange and outside hull plates is still used but should be avoided because of the excess weight of structure and generally unsatisfac- tory structural fitting resulting there- from.
Where the Main Deck Overhangs
Passenger and ferry boats for in- land waters usually have the main deck overhang the hull. This over- hang may be supported on brackets or be formed by a sudden hull pro- tuberance above the waterline (Fig. S3a). In the first construction the transverse framing resembles that for tugs or lighters, while in the second the frames are knuckled to conform with the deformed hull surface. This overhang is to afiford a maximum of deck space with minimum permissible beam of actual hull, so that the speed may not be seriously reduced.
Shallow draft vessels (Fig. 54) have straight frames on their bottoms and sides. The bilges are usually rounded and a bracket may be introduced to join side and bottom lengths. This avoids furnacing the frames and is as satisfactory a construction as when
-D«tl« House [TexasJ
,Coamtrn?life
Met.l Psr.der
^^
10) (W CO
FIG. 54— SHALLOW DRAFT VESSELS HAVE STRAIGHT FRAMES
Ul^H'C-ni
the side frames are bent to the bilge radius and overlapped on the bottom frames (Fig. 54a). In small vessels it may be possible to obtain the frame shapes in sufficient lengths to extend in one piece from gunwale to gun- wale, but this is not ordinarily feas- ible.
Square bilges with heavy bilge angles connecting the side and bot- tom plating may be employed and if the hull ends are properly modeled this will not prove a serious detri- ment to efificient propulsion. Bilge brackets are in this case also em- ployed. (Fig. 54b.)
Of late the bilges have occasion- ally been cut at an angle and a flanged bilge plate fitted to forged frames. (Fig. 54c.)
Web frames (Fig. 52) are fitted on every sixth to tenth frame and at the ends of the large hatches or fore-
'^:::'-'0
-Dauble I26/«'-s« F">-aivi<i
FIG. 53— WHERE THE MAIN DECK OVERHANGS THE HULL
castles, bridges and poop erections. They consist of a web plate from 14 to 42 inches wide connected to the hull by single or double angles and faced with half round or angle "face bars". The outline of a web frame is indicated by the broken line in the midship section (Fig. 52). The lower ends of web frames fair into floors and are connected thereto by lapped joints. The face angles continue along upper edge of floor plates in similar manner to reverse frames. Web plates may have lightening holes cut in them.
Floor plates from 8>^ to 36 inches deep at the center line form trans- verse brackets at the lower ends of side framing. The depth at a dis- tance from center line of J4 the half beam must be at least half what it is on the center line for large vessels. With a flat bottom this sometimes permits of sloping the upper edge of floor plates downward and outward to save structural weight and gain hold space.
It is usually preferable to have the upper floor edge horizontal and in small boats this is usually done re- gardless of the consequent reduction in overall width of floors.
Where the side frames join the floor plates the reverse angles diverge from the frames crossing the bottom of vessel at the upper edge of floors. If frames are of channels, zee bars, or bulb angles, these may be run along the lower edge of the floors to the keel and a reverse angle bar be fitted to upper edge of floors on the opposite side to the frames. Such reverse bars overlap the frames at the outboard floor ends. (Fig. £2d.)
32
The Desiijn and Construction of Po7t'er Work Boats
In the Machinery Space
Sometimes the channels, bulbs or zee The saving in furnace work and fitting portion to their sectional depth ren-
bars are split at their junction with expense of the attached members of ders it necessary to support them at
the floor ends and the upper portion the ships' structure is considerable. intervals by stanchions extending
forged to join the reverse bar on floor Where hatches or trunks necessitate to the vessel's bottom. The unsup-
tops, while the lower half joins a cutting deck beams the severed beam ported beam length should not exceed
frame angle at lower edge of floors ends are connected by angle clips to IS feet for ordinary construction and
(Fig. S2c). a strong longitudinal coaming plate must be less than this if heavy deck
which forms a girder supporting the loads are carried.
deck sides between the hatch ends. Stanchions may be disposed longi-
Floor plates in machinery space Heavy girder beams at the ends of tudinally on alternate frames or they
should be thickened by 0.04 inches these deck openings take the abut- may be widely spaced with girders
and the reverse bars be doubled at ments of longitudinal coamings and under deck beams connecting their
their tops. In the peak tanks at the are built up of a plate witli upper and heads. Closely spaced stanchions, as
forward and after ends of vessel, lower angles. These heavy beams the former are termed, may be of
floors are deepened to form stron.g are usually bracketed to web frames. solid round bars or of extra heavy
brackets .'.t the acute lower interser.- In forming beam brackets to frames wrought iron pipe welded to forged
tion of the hull sides. The reverse it was formerly common to split the heads and heels. This type should
angles are also fitted at their tops, beam section, bend tlie lower por- be fitted at the corners of all hatches
ana floois in after peak tanks some- tion downward and weld a piece of
times support the shaft tube which plate into the forked opening at beam
pierces them. ends thus formed. This expensive
All floors may be lightened by cir- method has been replaced by . rivet-
cular or elliptical holes cut at their ing beam and frame ends to a bracket The heel is forged to a flat palm in
neuiral axes. Care should be tak'ir. plate (Fig. 52) whose inner edge may this case, but if the stanchion steps
that depth of lightening holes does, be flanged (Fig. S3), and into which on a steel flat the heel is connected not exceed one-half the depth of the
and large deck openings.
Fig. SSa shows a closely spaced pipe stanchion with head having a vertical palm connected to a bulb angle beam.
flrtMll4»tsV>l^
A+Huior't'ahilP
Lon(\i'todina\ E\«vation
LonnlTudinol J \ f
I + H
LO
id)
le)
3 MMM
Inner
FIG. 55— STEEI. STANCHIONS AND STANCHION HEADS
plate. Deck beams gl^-^Jl" p
are of angles, bulb fe|,_^_ r'
angles, channels or
bulb Tees, fitted in
one length across
the deck and brack- eted at the deck
side.- to ihe frame
heads. -Angles, bulb
angles or chamiels
face in opposite di-
r e c t i o n to the
frames .so that they
may be connected
back to back at
the beam brackets.
When the deck is
of steel plating,
beams are fitted on
each frame while
with a wooden deck the steel beams lightening holes may be cut.
are on alternate frames. The depth ("d" Fig. S3) at the in-
It is common to bend or "crown" ner bracket end on deck beam should
deck beams upward in a circular arc not be less than six times the diame-
so that the heiglit at center above ter of rivets connecting the bracket
sides is J^-inch per foot of deck width to the beam; while the depth "h"
at the particular beam considered, and length "w" of bracket sides on
This camber was formerly claimed to frame and beam respectively, should
contribute transverse deck strength be three times the beam depth.
due to the arching efi^ect. The fal- In holds of considerable depth it
lacy of this theory is tliat all arch becomes necessary to introduce widely and the foundation channels extend
at least three frame spaces. It is desirable to fit all stanchions above the longitudinal girders in a ship's bottom known as "keelsons".
Shallow draft hulls have the stanch- ions on frames in the longitudinal trusses. Bracket plates connect the stanchions to the upper and lower chord shapes and to the diagonal angle braces.
to an angle clip by a vertical palm similar to the head here shown. If the deck beam is of channel section the stanchion head may have a horizon- tal palm as in the heel here shown. The objection to closely spaced stanchions is the degree of obstruc- tion to cargo stow- age which they in- troduce. Widely spaced stanchions of tubular or oth- er sections (Fig. S5-b-c-d-e) are now fitted to most ves- sels carrying hold cargoes. Longitu- dinal and transverse bracket plates connect the heads to the beam girders and deck beams (Fig. SSb) ; while the heels are bracketed to foundations on the inner bottom plating or the floor tops (Fig. 55). In the latter case, brack- ets clii)ped to the reverse frames afford double angle connection to tlie floors
thrusts are taken at the ends which spaced "hold beams" which tie the
in this case are tne relatively fle.vible ship's sides together and end on
.ship's sides. Camber is now em- "stringers" or heavy longitudinal side
ployed for drainage purposes only, girders. Strong vertical and hori-
but since a ship is very seldom on zontal brackets are fitted at hold
an even keel. ^ en this is scarcely beam ends to these stringers and to
warranted, since the water often ac- web frames which should coincide in
cumulates on the high side of deck spacing with the hold beams. Hold
houses and coamings amidships. beams are usually built up of a plate
Flat deck beams or those with with double upper and lower angles
straight ridged sides rounded at the or of two channels back to back,
center line, are becoming widely used. The long length of beams in pro-
CHAPTER VIII
Design of Longitudinal Framing
^^^^^HE principal strains set up in m C^\ ordinary vessels are longitu- ^ J dinal in character and can be
^^^^ best understood if it is as- sumed that a wave of the vessel's length has its crests at the bow and stern ; or this same wave has a crest amidships and a trough at the bow and stern.
The length of a wave is measured be- tween the highest points of two suc- cessive crests or the low points of two successive troughs. The height of a wave is the vertical distance between the lowest point of a trough and the highest point of a crest. This height is taken as one-twentieth of the wave length, so that a 100-foot wave would be 5 feet high. The profile of a wave is -a curve called a "trochoid," gener- ated by a point on the circumference of a rolling circle.
Wave Action Causes Strain
When the vessel's water line has a wavy contour, the maximum longitu- dinal strains are set up in the vessel by a wave of its length. Where the crests are at the bow and
the keel. The cross section of the ves- sel is that of an equivalent girder and the longitudinal bending strains can be taken only by the hull planking or plat- ing and such longitudinal framing as may be fitted.
When the wave crest is amidships, the deck tends to hog and the bow and stern to sag. Tension is here set up in the deck and compression at the keel. In either case the midship section is that most greatly strained and the change from tension at the top to compression at the bottom, or vice versa, is gradually reduced from maxi- mum intensity at the extreme top and bottom to zero at a point about halfway between the keel and the deck. The plane of zero stress is called the neutral axis.
If the moment of inertia of the midship section were calculated about the neutral axis and the greatest bending moment for hogging and for sagging were derived from curves showing the longitudinal distribution of hull weight and buoyancy, the stress in the ex-
stern and the trough is amid- ships it will be seen that displace- ment is concentrat- ed at the ends and lacking amidships. Since the vessel's weight is greater at midlength due to the machinery and cargo, the tendency would be for the unsupported middle body to sag. The hull in this case resembles a beam supported at the ends and with a downward load midway between the supports. This sets up compres- sive strains tending to crumple the deck and tensile strains tending to stretch
S+ern
,Hull Plank
Stem
/Tmniverie Frames Widely &i>Aced.
Ofiok Lc»n<)i+i/el/r»al4-
BoTtom l.onO)ifud\na\6
FIG. 56-
LONGITUDINAL STRINGERS AND SHELVES FOR WOODEN TUGS AND FRAMES FOR SHALLOW STEEL VESSELS
treme deck and keel structure could be calculated from the well known formula : SI
M equals
c where M is the bending moment in foot pounds or tons. 6" is the stress in pounds or tons
per square inch. / is the rectangular moment of inertia of the midship sec- tion. c is the vertical distance from neutral axis to upper edge of deck or lower edge ©f keel.
Strength of Framing Defined
Ordinarily it is not necessary to per- form this complicated and extensive calculation for strength, since the ex- periences of years have established the proper sizes and disposition of the hull structure. For steel vessels this has been particularly well accomplished by the large marine insurance societies such as the American Bureau of Shipping, Lloyd's Register of Shipping, The Bureau Veritas, etc. Here the various structural members are tabulated ac- cording to the di- mensions of the vessel and if these are known it is a simple process to select the proper scantlings. Large wooden vessels have been similarly tabulated but not so thoroughly, since wood as a ship mar- terial has been so broadly replaced by steel. In smaller vessels the reverse is true and wood will doubtless con- tinue the material composing hulls less than 100 feet long. At the conclusion of these chapters a tabular scantling
Comityoofiort.
33
34
The Desian and Cotistrurtiou of Power Work Boats
table for commercial power boats will be appended and duly explained, with a view to facilitating the construction of commercial power boats.
If the above theory held in practice, the longitudinal framing would be strongest on the vessel's bottom and at the deck and little or none would be needed at the sides. This is not quite true in practice because the vessel may be subjected to hogging and sagging stresses whole it is rolled over at an angle. The sides would here contribute toward resisting the longitudinal strains and even disregarding this condition it is necessary to reinforce the ordinary transverse frames by side longitudinals to withstand the local bending intro- duced when striking or rubbing against docks or other vessels.
Keelsons
Longitudinal girders on the vessel's bottom are termed keelsons and should
arc covered by the false keel. The keel- son timbers are also bolted together by vertical bolts between the frames and by horizontal bolts uniformly spaced to clear the vertical fastenings.
Notched Keelsons Not Necessary
Sometimes the keelson timbers are notched over the inner frame edges with a view to reducing the tendency to trip in the latter. The added labor in constructing notched keelsons and the weakened cross section caused by cutting away material at the notches together with the difficulty of obtaining accurate joints, render it doubtful wliether this elaborated construction is justifiable.
In all cases where wooden longi- tudinals are composed of more than a single timber and it • is impracticable to extend these in one length from stem to stern, the butt scarphs in the various timbers should be carefully dis-
• rioll y>\ank6eami
FIG. 57— CROSS SFXTTONS LONGITUDTNAI. SHOWING FRAME CONSTRUCTION
extend as far for and aft as possible. They are ordinarily not more than 8 feet apart at the midship section. There is usually a center keelson fitted in conjunction with and directly above the keel. Side or "sister" keelsons are between the center keelson and the lower turn of bilge. "Bilge keelsons" are at the turn of bilge. "Engine keel- sons" are fitted under the main engines and should carry the machinery vibra- tional strains to the other framing.
Fig. 49 indicates the disposition of keelsons in a large wooden vessel (from 100 to 300 feet long). The center keel- son is composed of two or more limbers side by side and superposed in pyra- midal fashion. Long vertical bolts pass through each keelson timber and each transverse frame, the bolt ends being riveted over countersunk ring washers. Those timbers directly above the keel are vertically bolted to it at each frame and the countersunk lower bolt heads
posed so tliat no two joints are at or near the same point. By this means the loss in longitudinal strength at the butt joints is not such as to materially weaken the girder.
Other forms of wooden and steel center keelsons in vessels with trans- verse framing were discussed in con- junction with keels in Chapter V.
Side or sister keelsons are fitted in large wooden vessels as in Fig. 49. Where there is but one on each side of the center line the hold stanchions should step on it and be connected thereto with natural crook timber knees or forged metal brackets. Where prac- ticable the side keelsons should form part of the engine foundation framing, particularly in small vessels. If the alignment of the engine bed casting does not conform with the top of the continuous side keelsons, auxiliary tim- bers of proper shape and dimensions should be bolted on top of the keelsons
to receive the engine, or should rest on the tops of transverse framing imme- diately alongside the side keelsons, be- ing side bolted thereto.
Engine Keelsons Should be Long
When it is not practicable to incor- porate the side keelsons with the engine keelsons, the latter should be of con- siderable length. The timbers to which the engine is bolted are usually too close together to pass the large flywheel of most internal combustion engines. For this reason these local timbers are bolted to and inboard of a keelson on each side and the difficulty of pass- ing the flywheel is obviated by the thickness of the foundation timbers.
If it is not feasible to extend the engine keelsons all fore and aft they may butt against forged angle collars on the forward and after engine room bulkheads, particularly if these are of steel.
It is not customary to fit more than than one side keelson in large wooden vessels, since the ceiling timbers on the inside of transverse frames from the center line to the bilge are made extra heavy. Care should be taken to stagger the end joints of adjacent and neighboring ceiling timbers in the same way as for center and side keelsons, in order that no serious local weakening may result.
Steel side keelsons, one or more in number, are fitted in transversely framed vessels as in Fig. 58 (a) to (c). They consist of continuous longitudinal steel shapes on the floor tops, with or without intercostal plates extending between the floors to the sheel plating. Types (a), (b) and (c) are fitted in large vessels. They consist of continuous angles, bulb angles or a built up girder connected to the floor tops by a reverse bar clip having at least three rivets. The inter- costal plates have their upper edges riveted between the continuous keelson angles and are notched to permit pass- age of the frame, reverse frame and reverse slip. A vertical clip joins the intercostal plates to each floor while lightening holes may be cut to save weight.
Bilge keelsons are usually part of the heavy bottom ceiling timbers in large wooden vessels (Fig. SO). Small wooden vessels usually have two or more square bilge keelsons sprung into place and through bolted to the frames (Fig. 49).
Steel bilge keelsons consist of two angles or bulb angles fitted back to back on the inner edges of transverse framing at the bilges. (Fig. 52 (c) and (d).
Steel engine keelsons (Fig. S3) are longitudinal plate girders on tops of the floor plates, with angles at the lower edges riveted to the reverse
Dcshiit of Longitudinal Framing
35
frames. The engine base is bolted to continuous angles on the upper edges of the engine keelsons.
Where possible, as in the case of wooden vessels, one of the engine keel- sons should merge into a side keelson, the keelson plate being deepened locally to the proper height for receiving the engine base. Transverse brackets clipped to the keelson plates and the reverse frames should support the engine girders at each frame.
Keelsons in shallow draft vessels con- sist of the lower truss chords previ- ously described (Fig. 51 and 54) and the bilge log or the bilge angle.
Stringers
All longitudinal girders on the ves- sel's side above the bilge are covered by the term "stringers". The location determines the nomenclature of each stringer, so that :
(a) Hold stringers are those between the bilge and the lowest deck.
(b) Stringers at sides of decks or on tiers of beams in the hold are called "uper deck stringers", "lower deck stringers", "hold beam stringers", etc.
(c) Stringers located midway between two decks are "between deck stringers".
(d) Short stringers at the vessel's ends are called "panting stringers".
Large wooden vessels usually have heavy ceiling on the inner edges of the side framing, rendering it necessary only to fit stringers on top of the deck beams at their endings on the frames.
Upper deck stringers are sometimes called "margin planks" and are fitted to wooden vessels. If the frames extend through the stringer to form bulwark stanchions, a continuous stringer timber is fitted inboard of a notched margin plank fitting closely around and be- tween the frame heads. This notched plank may be dispensed with by fitting filling blocks between the frame heads and the continuous stringers inboard of these. When the frames do not pierce the weather deck, tlie rail is on top of the continuous margin plank.
Lower deck stringers in wooden con- struction consist of one or more con- tinuous timbers, side by side or one above the other such as the hold beam stringer.
Side stringers may lie fitted in line with the lower fender with through bolts thereto.
All wooden stringers should be se- curely through bolted to every frame and to the beams on which they lie. The vertical bolts should pass through shelf timbers if these are fitted under the 1)eams. Timbers should be in long
lengths with scarphs in adjacent tiniljers widely separated.
Clamps
Clamps are heavy timbers on the inner edges of frames under the end- ings of beams. They may be of a
Continuous Ke«lson San.
"R'derTld-tS
frame edges, to which they are securely joined, with short angle clips in addi- tion to the reverse frame angles. An intercostal plate may fit between the stringer angles and between the frames to the shell plating where an intercostal clip secures its outer edge.
Su'a Kcclbois It - Double Bo1t{jm„.
lrtn»r "Bottom^
- .n\erc06ja\ KeeUon Tlati
nTe.rU)>ta\ SViell flntjle'' (.<») CW CCJ
, WatertKiVit or/ ^BracV:eTF'loor'
FIG. 58— STEEL SIDE KEELSONS WITH TRANSVERSE FRAMING
single plank with its long side vertical and notched under the beam. Or sev- eral timbers may be used. Through bolts should be used transversely through clamps and frames or vertical- ly through clamps and beams.
One or more timbers under beam ends may be fitted inboard of clamps and are called the "shelf". Tliese assist in tying the beams to the frames and are through bolted to both.
The forward and after endings of stringers, clamps and shelves should be as in Fig. 56, with overlapped termina- tions to breast hooks or to filling blocks between the deck beams and to the stem logs.
Steel deck stringers are heavy hori- zontal plates at the sides and securely riveted to ends of deck beams. A continuous outer angle connects these stringer plates to the shell plating. In lower decks the frames usually pass up through slots in the outer edge of the stringer plate and the continuous stringer angle is fitted along the inner frame edges, being riveted to the stringer plate and to the reverse frame.
Good practice calls for side stringers at least every 8 feet and this may require additional short stringers in overhung sterns, where the extreme slope of the ship's sides creates ex- cessive length of unsupported side framing between decks.
Panting stringers are fitted at the bow between the endings of continuous side stringers. Heavy breast hooks or bracket plates connect the ends of these at the stem. These panting stringers serve to reinforce the fine forward hull against the heavy local strains set up by en- countering waves.
Cartings
Wherever it is necessary to cut hatches or other large openings in the decks so that the beams must be cut, a seri- ous loss of deck strength results. It is necessary to compensate for the weakness so caused by butting the short cut beams on longitudinal girders which span I)ctween the intact beams at tlie ends of the hatch or opening. In wooden vessels these longitudinal girders are called "carlings".
. Hatch Cover
• Meldine)
IJ«elcMart)iii'PJuHle
-Fencer
ShetrT\<\nk
Outside Tiankinj
Coaming T'late-'
FK;. 59— HATCH AND COCKPIT COAMING CONSTRl'CTION
The space between frames, stringer angle and shell plating, should be filled with cement or by a tightly fitted wooden block.
Between deck or hold, stringers of steel may lie of two angles or bulb angles fitted liack to back on the inner
Carlings are heavy strong timbers, always in one length and should always l)e supported by stanchions at their ends. When more than 10 feet long, an extra stanchion should support each carling midway between the ends. These stanchions should have heavy timber
36
The Design avd Construction of Power Work Boats
knees to the carliiig and the beam at their heads. The short deck beams should be morticed to the carlings at their inljoard ends. Heavy horizontal timber knees should connect the ends of carlings to the beam at ends of the opening against which they butt. Natur- ally these knees should not ordinarily obstruct the hatch opening but should be fitted on the outboard side of car- lings under the deck planking. All connections where possible, should be through bolted.
Coamings and Sills — Wood
The edges of all deck openings should have heavy coaming timbers fitted above the carlings and deck beams at ends. These coamings reinforce the carlings and prevent wash of considerable mois- ture into the hatches. They are rab-
Lonq
itwdmal Wamma V^'''*' •Single ■BaHbn
"Bee ftuf
ForTank Vessels. Suitable For Ordina.-M ■&^\\! Ca<-il<i Ul'\Ms '^ut^. Of P».Uoni S^n ■Bet-u.^f -1 Tr.r.«y«r« >cirtini f€ilini U LB»ttem fff H»U.)
TVansvaoc f^raff\c.
employed in smaller fishing boats, the coaming may be a continuous heavy oak plank extending above the deck as in Fig. 59c. This is securely bolted to a carling which fits between the coaming and the inner edges of the frames. A heavy cap rail may be let over the upper edge of the coaming plank and a ]4 round molding is fitted at the junction of coaming with deck planking.
Steel hatch coamings are shown in cross section by Fig. 59 (a and b). The upper edges are fitted with angles or a special steel molding in which the wooden hatch covers rest. Steel hatch covers will be later taken up. The ends of cut deck beams are clipped to the coaming plate, as shown, and a margin plate is fitted on deck all around the hatch opening. This margin plate is
lb)
WiTh Double Botfortl-
FIG. 60— CROSS SECTION OF A TUG WITH LONGlTtJDINAL FRAMING
beted at their upper inner edges to receive hatch covers and are fitted with lugs to support the ends of portable hatch girders under these covers. Coamings should be through bolted to the carlings.
When carlings are fitted below the lower edges of deck beams, heavy fill- ing pieces should be fitted between the ends of deck beams which extend over the carling. This provides solid timber between the carling and the coaming or lower deck house sill which rests on top of the inboard beam ends.
All through bolts in wood construc- tion should pass through solid timber, for if there were a space between the timbers in which the bolt heads are embedded, the two timbers would spring when the bolt was tightened.
Cockpits in Small Boats With wide open cockpits such as are
connected to the coaming plate by the riveted coaming angle.
The lower edge of coaming plates should be fitted with angles or chan- nels to form a stiff girder at the sides of the hatch. Sometimes this lower edge of coaming plate is flanged over, as in Fig. 59b.
Deck girders over the heads of stanchions and supporting the deck beams are fitted of wood or steel if the stanchions are widely spaced. Shallow draft hulls which are not deep enough to be rigid have longitudinal trusses in the holds. These consist of a con- tinuous lower girder or chord on the bottom, and upper chord under the deckbeams and stanchions between these chords at intervals of from 3 to 6 feet. Diagonal braces extend from the foot of one stanchion to the head of the next in zig-zag manner. These hold
trusses may be wooden or of steel angles and bracket plates.
Longitudinal Frames — Wood
The fitting of most of the internal hull framing in a fore and aft direction is becoming very popular and properly so. In light pleasure boats these longi- tudinals are peculiarly desirable with "V" bottom hulls. This is because the relatively slight curvature of any cross section permits the use of wide planks and light longitudinals are fitted over each longitudinal plank seam.
In power workboats with shipshaped hulls it is impracticable to fit planks wide enough to allow for sufficiently heavy longitudinal frames at each seam. To lighten the frames in keeping with the plank width should not be attempted without study. Fig. 57 (a) and (b) shows the application of heavy longi- tudinal framing to workboats. Trans- verse frames at intervals of from 4 to 8 feet are fitted inside the longitudinal frames which are spaced from 12 to 18 inches apart. It is necessary to fit filling pieces between the hull plank and the widely spaced transverses, so that the plank seams between longitudinals are properly supported.
It would be simpler to run the hull planking transversely or diagonally across the longitudinal frames as is done in some barge construction. This is not recommended for vessels which are self-propelled unless the bottom is sheathed with metal, because the rough- ness of the surface is increased with respect to the direction of travel and more power is lost in skin frictional resistance.
Longitudinal steel framing is not used in vessels of smaller sizes, but has been considerably employed in barges and box-shaped hulls. In steel ship- building this is known as the "Isher- wood" system, having been patented under that name.
Fig. 60 is the cross section of a tug built on the longitudinal system of framing. Continuous bulb angles spaced from 20 to 27 inches apart extend fore and aft on the inside of the shell plating and under the deck. At the ves- sel's ends where the girth of section is less than amidships, it is necessary to stop some of the longitudinals at the peak bulkheads to which they should be bracketed. It is common to stop all longitudinals at these peak bulkheads and to substitute ordinary transverse framing from these points to the stem and stern, respectively.
Heavy transverses which are merely web frames spaced from 10 to 12 feet apart, are fitted as in Fig. 60 to resist transverse and local stresses.
CHAPTER IX
Bulkheads Demand Careful Planning
'LL vertical partitions in a ves- sel are called "bulkheads." They are what correspond to the interior walls in an ordi- nary house. They are classified accord- ing to their strength and purpose as :
(a) Structural: Non watertight, watertight, oil tight.
(b) Divisional, partitions, etc.
Bulkheads running across the ship are called "transverse" and those ex- tending fore and aft are "longitudinal bulkheads."
Steel or wood may be used in bulk- head construction. Watertight bulk- heads are fitted in the holds of most vessels, their object being to minimize the danger of sinkage by confining the seawater to any compartment in which the hull may be damaged by collision, grounding or other accident. Transverse bulkheads are most effec- tive for this purpose. Tanks contain- ing fresh water, water ballast or for fish preservation in trawlers are also fitted with watertight bulkheads. The number of watertight bulkheads in- stalled varies with the size and type of vessel.
The Collision Bulkhead
Nearly all vessels have one trans- verse watertight bulkhead called the "collision" or "forepeak" bulkhead. This is fitted near the bow and should be on a transverse frame. In large vessels the distance abaft the stem is one-twentieth of the vessel's length, but in vessels less than 125 feet long this distance is greater (from one- eighth to one-si.xteenth of the length).
There is also a watertight bulk- head at each end of the machinery space and usually enclosing compart- ments in which fuel is carried in separate tanks. When (in the case of steel vessels) the fuel tanks are part of the hull, the bounding bulkheads must be of especially tight construc- tion to prevent leakage.
In a previous article the need of reserve buoyancy and the purpose of bulkheads was demonstrated by as- suming that a central compartment of a box shaped hull was punctured and that the bulkheads in this com- partment prevented the inrushing
water from flooding the entire hold. The vessel then sank until the volume of water which the damaged compart- ment had originally displaced, was re- gained by the intact parts of the hull on each side of the damaged compart- ment. The symmetry of the regained buoyant volumes caused the vessel to settle parallel to her original water plane.
Fig. 61 shows what occurs to a vessel when damaged in the more usual and less favorable manner of having a compartment near the bow or stern torn open to the sea.
Suppose that the water plane (VV-L) is that at which the vessel floated before the compartment (RSTV) was damaged. The point (B) will represent the center of buoyancy of the original underwater volume (DEFV) and the point (G) is the center of gravity of the vessel's structure and contents. These two points are located on the axis (X-X) which is perpendicular to the original water line (W-L). Now when the sea water enters compartment (RSTV), the displaced volume is de- creased by the portion (HFTV), and the vessel may be assumed to settle to the water line (w-1), which is parallel to (WL). The volume (OliPH) between these water planes must equal the lost displacement (HFTV) and the new intact under- water volume is (ODRT). The point (B') halfway between the bulkhead RT and the end OD is the center of buoyancy of this new imderwater volume and it is to the left of the original center (B). If the vessel floated at (w 1) after damage as assumed, the force of buoyancy would act through the point B' and upward on the line (y-y) which is perpendicu- lar to the line (w-1). The vessel's weight would act downward through the center of gravity (G) and along the line (x-x). This line is also per- pendicular to the line (w 1) so that we would have two equal forces act- ing in opposite directions as shown and separated from each other by the distance (h) between (x-x) and (y-y). These two forces form what is called a couple and would tend to rotate the vessel in the direction taken by the
37
hands of a clock (called clockwise). It will also be seen that when these two forces act in the same straight line there will no longer be a tend- ency to rotate the vessel and since the forces are equal but opposite, the vessel will then come to rest.
Accordingly let W'L' be the in- clined water plane to which the vessel will incline or "trim" when the forces of buoyancy and the vessel's weight are again vertically in the same straight line (z-z). The final under- water volume (ARTD) will equal the original displaced volume (EFVD) and (B") is the final center of buoyancy.
It is possible to calculate the posi- tion of the inclined water plane (W'L') and consequently the effect upon the vessel of flooding any com- partment. This calculation is involved and of too great length to be con- sidered here. For a complete dis- course on this subject refer to Att- wood's text book on "The Theoreti- cal Naval Architecture" or to Biles' "Design and Construction of Ships."
Notice that the freeboard is less at the damaged than at the intact end of the vessel and that the draft S V is greater at the damaged end than the draft A D at the other end.
The quality which a vessel has of inclining in the above manner is known as "changing trim." The dif- ference in feet and inches between the draft S V at the low end and A D at the high end is called the "change of trim" and is equal to the sum of F S and A E. But F S and A E arc the changes in draft from the original water line W L to the new water line W' L'. Therefore, the "change of trim" is equal to the sum of the changes in draft at the forward and after ends of the vessel. Change of trim may be produced by moving a weight from its position on the vessel, to a point nearer the bow or stern. The weight which must move one foot to cause a change of one inch in trim, is called the moment to change trim one inch.
Large ships are so designed that if two adjacent hold compartments should be flooded, the change of trim will not be excessive and the vessel
3S
The Design and Construction of Poivcr Work Boats
FIG. 61— WHAT HAPPENS WHEN THE BOW OR STERN COMPARTMENT IS
FLOODED
will float, or if three remote com- partments are flooded the vessel will not sink.
Small vessels can with difficulty be made to conform to such require- ments, since the increased number of bulkheads necessary would make the hold compartments too small to carry cargo economically.
Again, wooden bulkheads or steel bulkheads in wooden hulls cannot be made absolutely watertight in case of hull damage. This is because the seams of the hull planks would ordinarily "start" for some distance on each side of the point of impact, permitting the water to leak around the margin of the bulkheads to the other compartments.
Bulkheads serve to retard the leak- age and to save the vessel if action is quickly taken and the pumps have sufficient capacity to discharge the
water as it leaks in. Steel bulkheads in steel vessels can be made water- tight, but do not necessarily make the vessel "nonsinkable." This term is a fond dream concocted in the fertile imagination of laymen.
In very small vessels such as life- boats where the holds are not used to carry cargo, watertight metal tanks are sometimes built into the hold compartments and they afford suffi- cient buoyancy to float the boat if the exterior hull is damaged. If these tanks are also punctured, their utility ceases and the boat will sink.
Wooden Bulkheads
Fig. 62 is a transverse watertight bulkhead in the hold of a wooden vessel longer than 125 feet. The ceiling which contributes to the longitudinal strength of the vessel, should not be cut at the bulkhead
JBi
'L
^S3 — ^
i
Tran6\/erse 6ect'»on
Loncfifuciincil Elevation.
FIG. 62— TRANSVERSE WATERTIGHT BULKHEAD OF WOODEN VESSEL LONGER THAN 125 FEET
which fits closely inside of the in- ternal longitudinal hull timbers. Two thicknesses of tongue and groove planks with a layer of canvas in thick white lead, tar or paint between them, form the bulkhead proper. The seams of these two thicknesses of planking are at right angles to each other, one set running vertically and the other horizontally; or both sets being at complementary angles of 45 degrees to the vertical ship's center line.
The bulkhead planks are through bolted between two deck beams at their tops and between heavy bulk- head margin timbers all around their edges. Canvas strips thickly coated with thick lead and called stop waters, are fitted between the bulkhead plank- ing and the margin timbers. In very heavy construction all the bulkhead planking and margin seams should be calked, particularly if one of the compartments is to form a permanent water tank.
A steel angle iron properly forged to fit closely around the bulkhead edges may be substituted for the mar- gin timbers and canvas stop waters or calking should also be used in the seams where the bounding angle fits against the bulkhead planking and the longitudinal ceiling.
Heavy stiffening timbers should re- enforce the bulkhead plank on each side. They should be spaced about four feet apart and should be logs whose square section is at least four times the bulkhead thickness. The stiflfeners extend vertically on one side and horizontally on the other side of the bulkhead. Heavy natural crook timber knees or forged metal brackets connect the ends of bulk- head stiffeners to the deck and ceil- ing. Where practicable, stiffeners should terminate on keelsons and stringers.
The thickness of bulkhead planking for the above construction varies from one-half inch for each layer (one inch total thickness) in small boats (30 to SO feet long); to four inches for each layer (eight inches total thickness) in vessels 325 feet long.
These larger bulkheads may be con- structed of one thickness of six to eight-inch planking, calked on both sides, but the strength and tightness are not equal to those obtained with the double layers at riglit angles to each other.
Transverse Watertight Bulkheads
The transverse watertight bulkheads of small vessels in which the ceiling planks are not fitted for strength, may be constructed as in Fig. 63. In this case the only longitudinal fram- ing which passes through the bulk- l-.ead consists of keelsons, stringers.
Bulkheads Demand Careful Planniiig
39
clamps and shelf logs. The bulkhead planks extend out to the hull plank- ing with double frames and beams forming the margin logs. Canvas stop waters are bolted between the bulk- head planking and the marginal fram- ing. Steel angle bar staples are forged to fit around the longitudinals which pass through the bulkheads.
In this connection it may be re- marked that watertight bulkheads were not fitted in holds during the period when wooden ships were pre- dominant.
Longitudinal watertight bulkheads of wood are not often fitted. The construction is identical with that for transverse bulkheads when they are used.
Engine Bulkheads Fireproof
It is desirable to render bulkheads in the engine room fire resisting and this is accomplished by covering the side toward the engine room with a layer of asbestos mill board or other insulator. Galvanized sheet iron is tacked over this insulation. Yellow pine or fir planks are used for water- tight bulkheads.
Divisional or minor wooden bulk- heads serve to divide the interior of vessels into the various compartments for berthing, messing, storage, etc. They may be longitudinal or trans- verse and built of vertically staved tongue and grooved planks, panels or composition wallboard tacked over wooden staves.
When extending athwartships it is desirable that they fit against a trans- verse deck beam (Fig. 64-a). The lower ends of bulkhead stavings are set into a grooved sill as shown and the planks driven home then blind nailed at top and bottom. If the height is more than seven feet (un- supported planks) and the thickness is less than one inch, an intermediate horizontal studding should be fitted between vertical stiff eners of 2 x 4-inch timber spaced not more than four feet apart.
This same reasoning applies to panels (Fig. 64-f), but the studding should be lighter and the paneling be fitted on both sides thereof (Fig 64-k).
Bulkheads In the Cabins
Divisional longitudinal bulkheads in living spaces extend to a scantling which is grooved to receive the bulk- head sheathing and is fitted under the transverse deck beams (Fig. 64-b). This leaves an open space for ventila- tion between the top of the bulkhead and the deck above. This space may be left open or fitted with a grill of wood or metal.
Galleys, pantries, baths and toilet
■^c^^'^''
Vertical STif^ENCR.
SlOe JTRtN&«R.
BuuKHEftD ■pLANlCINtr,
t 1 1^ Sr«pi.E flwaiUE.
Jk ll£l \.l<&ELi.ON'
Keeu
PlTHW/^ieTSHlP View LON&ITi^DIVrtL El^vAT'ON.
FIG. 63-TRANSVERSE WATERTIGHT BULKHEAD FOR SMALL WOODEN VESSEL
spaces should be completely shut oflf from the other compartments by ex- tending the longitudinal bulkhead sheathing between the beams to the deck or cabin top overhead as in Fig. 64-c. A quarter round or other mold- ing is neatly fitted around each beam.
Galvanized sheet iron, zinc or lead should line the bulkheads in shower or bath compartments to protect the wood from the splash. Tongue and groove bulkheads may be of V cham- fered or of beaded planks (Figures 64-d and e respectively) and vary in thickness from ^-inch to IJ^-inch.
Bulkheads of composition wallboard in combination with staving are shown in Fig. 64-g and h. The wall- board varies from 3/16 inch to S/16- inch in thickness and the sheets are securely tacked to the staving. A molding strip is nailed over the wall- board seams and may be of stained wood, thus affording a paneled affect. When the staving is solid as in Fig. 64-g, the thinner wallboard is em- ployed, but heavy board should be
used with widely spaced staving (Fig. 64-h). These staves are from J^-inch to lJ4-inch thick and from 3 to 4 inches wide. A clear space of from two to four inches may be allowed between staves.
Divisional bulkheads may be fitted in the deck houses and superstructure of steel vessels. The construction is the same as in the case of wooden boats and the object of using wood is to lighten the minor bulkheads, thus reducing the total structural weight and gaining carrying capacity on a fixed load displacement.
Steel Bulkheads
These may really be made water- tight or oil tight in steel vessels and they are more nearly so than wooden ones in wooden vessels. The common practice is to make the bulkheads en- closing the machinery space of steel, for fire resisting and to build the bulkheads in holds outside the engine room of wood in wooden vessels.
Where continuous inner wooden
[ l-0e«M
tbl
(c)
(d) m^m^^. iii.,i {fj
T&G- or Bnel
gfe%^ ^%a ^^ \gmii u^ vm (h)
sa
FIG. 64— CROSS SECTIONS OF VARIOUS MINOR BULKHEADS FOR CABINS, ETC.
40
The Design end Construction of Power Work Boats
(b)
(c)
Web S>t<f{ener
FIG. 65— STEEL BULKHEADS AND FASTENINGS FOR WOODEN VESSELS
ceiling is fitted for strength of recesses filled with cement or wooden
wooden vessels, the steel bulkheads plugs. These radiating bolts on
fit inside the ceiling (Fig. 65-a) and opposite sides of the bulkhead should
have double steel margin angles, be staggered as shown in (Fig. 6S-a
Sometimes wooden margin timbers and b), to prevent local weakening
are fitted on both sides of the steel of the frames due to material cut
bulkhead plating which is bolted to away. They should also clear the
them. (Fig. 6S-b). bolts or spikes which fasten the hull
Canvas stopwaters in white lead are planking to the transverse frames,
inserted between the margin angles Bulkhead plating in holds varies in
or timbers and the ceiling. Through thickness from 5 pounds per square
bolts spaced between the ones join- foot (J^-inch thick), to IS pounds per
ing the margins to the bulkheads, ex- square foot (5-^-inch thick), the width
tend to the outside of the transverse and depth of bulkhead regulating the
frames, where the bolt heads are thickness,
countersunk over washers and the The number of plates in a bulk-
7T'
A
L_
mrr
FIG 66-SHOWS METHOD OF FITTING "SHOES" AT BULKHEADS WHERE KEELSONS AND STRINGERS ARE CUT
head is governed by the maximum width to which the steel mills can roll and varies according to the thickness, width and length of the plate. This is governed by the size of steel billet from which the plate is rolled and the width of the plate rolls.
Use Standard Plates
The steel companies publish tables stating the standard widths of plates for each thickness and the layout of bulkhead plating should be such that standard plates may be used where possible. This will reduce wasted ma- terial and extra expense involved by sheering and planing the plates.
The seams of bulkhead plating are lapped and single or double riveted. The plate edges of seams in water- tight bulkheads should be planed to a slight bevel and should be calked after riveting. Calking of steel plates will be taken up in connection with shell plating, as will also riveting. The scantling tables appended to this series of articles, sets forth the proper thickness of steel bulkheads, the size and spacing of rivets and stiffeners. Rivet holes in seams should always be punched from the "faying" surfaces which are those bearing together at the seam.
Bulkhead plating is so thin relative to its depth and width that structural stifTeners consisting of angle bars, bulb angles, channels or deep web plates in conjunction with angles must be fitted. (Fig. 65-c and d). These are usually fitted vertically at intervals of from 18 to 27 inches.
Deep bulkheads have horizontal stiffeners on the opposite side of plat- ing to which vertical ones are fitted. Horizontal stifTeners are spaced about four feet apart.
Bulkheads In Steel Vessels Transverse watertight bulkheads in steel vessels are similar to those in wooden ones except that the marginal angles are riveted to the shell plating and the stifleners are bracketed at their ends. No stop waters are fitted and all the angles and rivets are calked. Fig. 66 is a transverse and longitudinal elevation of this type of bulkhead.
Keelsons and stringers may be cut at the bulkhead and secured there- to with bracket plates and angle clips or may pass through openings in the bulkhead plating and then be made watertight with forged staple angles or "shoes" as in Fig. 66. These alternatives also apply to longitudinal frames where the vessel is so con- structed.
Observe that the vertical stiffening angles are on the side of bulkhead plating away from that on which the
Bulkheads Demand Careful Planning
41
plating is joggled for seam laps; that the vertical seams of bulkhead plates are located between stiffeners and that in the case of a vessel with wooden decks (Fig. 66) a steel deck plate is fitted under the deck planks for one beam space on each side of the bulkhead so that the upper stiflf- ener brackets may be riveted to it.
Where it is necessary for piping to pierce watertight bulkheads, a flanged joint is fitted at the bulkhead plating.
Tank Bulkheads — Steel
Compartments designed to carry water, oil or other fuels in bulk, re- quire heavier bulkhead construction than was the case in those where safety against sinkage was the main object of installation, The severe stresses due to washing of the con- tents from side to side calls for closer subdivision so that longitudinal bulk- heads are usually fitted on the vessel's center line and "swash bulkheads" are fitted to cut down the surge of the fluid.
These swash bulkheads are merely flanged plates, stiffened vertically and extending between the ends and sides of the compartment (Fig. 67-a) or m.ay be continuous light plates with large holes cut in them (Fig. 67-b). Vertical angles about 24 inches apart stiffen the light swash plates and con- nect them to the watertight bulkheads at the tank ends and sides. Swash bulkheads are spaced from 8 to 12 feet apart.
Longitudinal watertight or oil tight bulkheads should have their lower plating formed by deepening the cen- ter or side keelson plates and these plates should always be continuous. All transverse framing on the vessel's bottom should be cut at the longi- tudinal bulkhead and connected to it by bracket plates. Sometimes deck beams extend through the top of longitudinal bulkheads and forged angle stapling is fitted around the beams to prevent leakage. More often the beams are cut and bracketed to the bulkhead, resulting in lessened expense of construction and ample strength.
Longitudinal centerline bulkheads have double angle bars all around their margins, affording connection to the keel plate, deck plating and trans- verse bulkheads against which the longitudinal bulkhead terminates.
Longitudinal bulkheads forming wing tanks are located on side keel- sons and usually have a single large margin angle.
The lower plating of watertight and oiltight bulkheads is usually heavier than the upper strakes because of the greater pressure imposed on the lower portion of the bulkhead by the
"hydrostatic head." In any fluid the pressure increases with the depth and is equal to the weight of a cubic unit of the liquid multiplied by the depth of the surface acted upon below the surface. Thus the weight of fresh water is 62.5 pounds per cubic foot and the pressure on an area one foot square at a depth of 10 feet below the water surface would be 10x62.5 or 625 pounds.
Center of Pressure
It is usual to assume that all the pressure load on a submerged sur- face is concentrated at a point called the center of pressure. This is located on the surface at the level correspond- ing to the center of gravity of an area formed by a curve showing the variation of the pressure load with
.lioiolloiiO
^iOjiOiiO o
the depth. If the surface is rectangu- lar, the pressure load will be equal to the pressure per square foot times the area of a strip one foot wide whose center is at the depth con- sidered. By computing the pressure at successive depths and plotting it to scale at that depth, a series of points will result, through which a curve may be drawn. This curve of pressures is a straight line since the widths are constant and the center of gravity of the triangular area be- tween the pressure curve and the bulkhead is two-thirds of the sub- merged depth below the surface. It is possible to calculate the strength of bulkheads, but the assumptions made require considerable detailed computations. Ordinarily the thick- ness of plating and size of stiffeners
=¥==i
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Cej (f)
(hj
FIG. 67— CONSTRUCTION OF TANK BULKHEADS FOR OIL AND WATER; ALSO METAL BULKHEADS FOR MINOR COMPARTMENTS
42
The Design and Conslrnclion of Poiver Work Boats
is taken from previous successful practice.
The vertical stififeners of longi- tudinal bulkheads are located at each transverse ship's frame and are of the same size as those for transverse bulkheads of the same depth.
Web stiffeners are on every fourth transverse frame of longitudinal bulk- heads and on every keelson at trans- verse bulkheads. These web frames are formed of a tapered plate secured to the bulkhead by a vertical angle and having double face angles on their vertical outer edges. Flanged bracket plates connect the lovifcr end of web stiffener plates to the trans- verse floor plates and to the deck plating.
Wing Tank Bulkheads
In deep tanks it is necessary to support the vertical stiffeners midway of their depth. This is done in wing tank bulkheads by angles sprung be- tween the side stringers and the bulk- head on alternate frames (Fig. 67-c). Bracket plates connect these stay angles to the stiffeners and to the side stringers if the latter consist of two shapes on the inside of frames. If the stringer has a wide shelf plate as shown in the figure, the stay angle
is riveted directly on top of this plate.
The intermediate stiffener support for bulkheads on the ship's center line and for deep transverse bulkheads, is provided by a plate shelf as in Fig. 67-a. Brackets support this shelf from the bulkhead at every stiffener.
Bulkheads in vessels with longi- tudinal framing have horizontal stiff- eners at the same level as the hull side frames and bracketed to these at their junction. Deep vertical web stiffeners are at every deep "trans- verse" at distances of from 8 to 10 feet apart in the tanks.
Minor Steel Bulkheads
Minor compartments may be en- closed by three types of steel bulk- heads extending transversely or longitudinally:
(a) Steel plate.
(b) Deformed steel.
(c) Wire mesh.
Minor steel plate bulkheads con- sist (Fig. 67-d) of an upper and lower coaming plate connected to the decks by angles. Lighter plating is fitted between these coamings with vertical butt seams which are covered with a wide butt strap as shown. This con-
struction has a paneled appearance on the side where these seam straps are. Vertical stiffening angles support these bulkheads at intervals of three feet and wooden sheathing or paneling may be fitted on the stiffener side by nailing it to furring strips bolted to tiie stiffeners.
Partitional bulkheads of deformed steel are shown in Fig. 67-e, f and g, being composed of galvanized sheet metal which is corrugated or paneled. The corrugated types (Fig. 67-e and f) require no vertical stiffening but present difficulty in fitting at the decks. The upper and lower mar- gins may be of wood or steel angles and the corrugations are nailed, riveted or spot welded where they touch these margin moldings. The space between the margins and the hollows of the bulkhead sheathing may be filled with wood blocks or with light cement.
Sheet metal panels may be nailed to wooden framework to form a very attractive bulkhead (Fig. 67-g).
Spaces requiring ventilation and light such as galleys, bakeries, etc., may be fitted with partitions of heavy galvanized wire mesh with a metal frame bolted to angles at the decks. (Fig. 67-h).
CHAPTER X
Hull Planks — Fenders — Bilge Keels
*'^^^J HE hull planks of wooden ves- m C^ sels are usually put on with ^ M the longitudinal seams butted,
^^^^ forming a smooth exterior surface. These are called "carvel" planked hulls (Figs. 57, 62, 63 and 65).
Small boats are sometimes "clink- er" built, that is, the longitudinal hull plank seams are lapped and riveted together. Clinker built boats are not caulked and require careful work- manship to construct properly since the frames must be notched to fit the inside of planking.
The more commonly employed car- vel system of hull planking has all seams calked with one or more threads of cotton or oakum, the num- ber of threads depending upon the plank thickness. Calking and fasten- ing of planks will be subsequently discussed.
One or more planks immediately next to the keel are made thicker than the rest of the hull planking and are called "garboard planks" or simply "garboards."
Small vessels (up to 50 feet long) have but one garboard plank from six to eight inches wide and from 154 inch to 2^/2 inches thick. Vessels from 50 to 100 feet long have two garboards from 2j^ to 4j4 inches thick and from 6 inches to 12 inches wide. Larger vessels have two or three garboards up to 6 inches thick. Occasionally, when two or more gar- boards are fitted, the plank next the keel is of maximum thickness and the second or third garboard has a thickness between this and that of the hull planking.
The Garboard Planks
Where oak can be obtained in long lengths, garboards are of this ma- terial, but yellow pine and fir are most often employed. Garboard planks are rabbeted to the keel as has been shown and should be edge bolted thereto if practicable. The ends of garboard planks if 2 inches or more thick should be scarphed, the scarph length being three times the plank width. Garboard plank ends less than 2 inches thick are butted between frames, a "butt block" to which the plank ends are riveted, being fitted
between the frames at the butt. End butts or scarphs of garboard planks should be well clear of those on the neighboring planking, keel and other longitudinals.
The uppermost hull plank follows Ihe line of sheer and is sometimes made of oak. It is usually wider than the remaining hull planks and is cut and bevelled to fit the sheer profile. It is called the sheer plank and is of the same thickness as the other hull planking.
Hull planking between the gar- boards and sheer plank is generally of imiform thickness (from 54 '"ch to 5 inches) depending upon size of vessel. Sometimes in large vessels the bottom planking is from J4 inch to 1 inch thicker than the side plank- ing. The width of these planks
FIG. 68— HOW STEALER PLATES ARE INTRODUCED.
varies from four to eight inches in vessels with curved frames. Greater widths than eight inches are not employed in this case because it is difficult to fit the inner surfaces to the outer edges of the transverse frames. Thin planks may be steamed and bent to this transverse curva- ture but thick planks are slightly hollowed with an adz, since they tend to split when bent transversely as well as fore and aft. Vessels with straight or slightly curved frames such as barges and shallow draft craft have planking up to 12 inches wide, the objections to transverse bending being absent.
Tapering the Planks at the Ends
In fitting hull planks they are spaced off (girthed) on the midship section and are of maximum width at this
43
section. The number of planks is then counted and the girths of several end sections of the vessel are divided into the same number of parts. The planks are tapered to fit fair at or near these points of division, but should not be too greatly reduced in width at the end frames. A minimum width for the reduced ends of one- half the midship plank width is good practice.
Where the girth of end sections is so much less than the midship section that excessive reduction in plank widths would result if the same number of planks were used at the vessel's extremeities, the number of planks may be reduced by fitting one wide plank at the ends of two narrow ones. Such a plank is a "stealer" and is fitted with a butt block covering the two planks which it replaces.
The extreme forward ends of hull planking fit into a rabbet on the stem and the workmanship at this point should be very accurate. The after ends of planks in transom sterns cover the ends of the transom planks and are fastened to the transom rim log. A sheet metal flashing is tacked over the after plank ends at transoms to protect the ends of wood grain against wear and decay. In overhung or fantail sterns where the after plank ends terminate on the horn timber, the plank ends are notched to a rab- bet on that timber, care being taken that the nibbed ends are not too nearly a feather edge.
If the planks cannot bend to the hull form due to the warped nature of the surface, it is necessary to "steam" them. This is done by build- ing a box long enough to take the longest planks and closing the ends. The whole is then calked and a steam pipe introduced at one or both ends with a drain pipe at the center. After the planks or other timbers which are to be bent, have been put into the box, usually through one end, the steam is turned on and permitted to flow until the planks have become pliable. This time is less for timbers of small section than for large tim- bers. A hot water bath may be used for light planks instead of the steam box.
44
The Design and Construction of Pozver Work Boats
Hull planking may be secured to the framing by:
(a) Screws
(b) Rivets
(c) Spikes
(d) Bolts
Screws and rivets are used in small vessels where the plank thickness is not over two inches. Brass screws are best and should have heads countersunk in the planking, the holes being closed with wooden plugs in thick white lead. The screws should extend two-thirds of the way through the framing.
Copper or galvanized iron rivets should have their outer ends over
more than eight inches wide have three.
The butt joints of hull planks should be between frames and butt blocks are fitted between the frames at the plank ends. The plank ends should be through fastened to the butt blocks and butt joints should be widely placed in neighboring planks, to pre- vent loss of strength in the hull structure.
Hull Plating
The various methods of fitting hull plating to the frames are shown in Figure 68 (a to f). The "in and out" system of plating (Figure 68 a and b) is perhaps the most common, the
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FIG. 6S-A— METHODS OF FITTING HULL PLATING TO FRAMES
washers in countersunk holes plugged as for screws. The inner rivet ends extend through the frames and are hammered or clinched over washers. Galvanized iron spikes with round heads may be used in very heavy planking in conjunction with through bolts. One or two spikes and one bolt are introduced in each plank at every frame. The spikes should be driven in holes drilled slisfhtly smaller than the spike and the 'ke shank may be "ragged" or rou^. '.o re-
duce the tendency to w out.
Planks up to eight inches wide have two fastenings per frame. Those
longitudinal seams being lapped as shown necessitate that the plates be fitted in this manner. The frames may be joggled so that the shell flanges fit over the staggered shell plates (a). If the frames are bent to a fair curve liners must be fitted between their shell flanges and the outer hull plates (b).
Joggled hull plates (c) avoid the use of shell liners with "faired" frames. Clinker plates (d) are not extensively used but it is necessary to employ this system at the vessel's ends when "stealers" which will be taken up shortly, are introduced.
Flush plating (e and f) is not commonly employed. Yachts and other vessels where the appearance of plate seams would be undersirable, are built as in (e).
The lowest "strake" of plating next to the keel, is the garboard strake and is sometimes thicker than the other bottom plating. It is edge lapped to plate keels and flanged to bar keels.
The uppermost continuous hull plate against which the upper deck stringer is fastened, is the "sheer strake." It is heavier than the lower side plating and extends above the deck to a height permitting two rows of rivets in the sheer strake butt joints to be above the stringer angle. In large vessels the strake of plating below the sheer strake is made heavier than the remainder of the hull side plating to the upper turn of bilge. Ordinarily the side plates from sheer strake to bilge are of one weight and the bot- tom plates • from the garboard strake to the bilge are of one weight, slightly heavier than the side plating.
Since the greatest tensile and com- pressive stresses are amidships, the plating at bow and stern may be lighter than that for a distance of one-fourth the vessel's length on each side of the midship section. Where severe local stresses are encountered due to panting at the bow and around the propeller bossing at the stern, the hull plating is made the same thickness as amidships on the same strake.
If the vessel is to operate in heavy ice floes doubling plates are fitted at the bow near the water plane. Doub- ling plates are also introduced where openings in the hull entail loss of strength, such as at large ports or sea suction and discharge orifices for machinery piping connections. At the points where long bridges, forecastles and poops end, diagonal doubling plates are fitted to prevent weakness arising from the sudden loss of ma- terial in the cross section of the hull.
Where the girthed section of the hull is so reduced at the bow and stern that the number of plating strakes fitted amidships would be- come very narrow, stealer plates are introduced to replace two strakes (Figure 68-g).
Laying Out the Hull Plates
The laying out and ordering of hull plates is done by arranging the stock widths as obtained from the plate tables of the steel company, on the girth of the midship section. Care must be taken to include the width of lapped joints in the width of strakes. It is undesirable to rivet more than two thicknesses of metal
Hull Planks — Fenders — Bilge Keels
45
together because of the difficulty in making tight rivet connections. For this reason the shell angles of keel- sons, tank margins, stringers or other longitudinal framing should be lo- cated between the longitudinal seams of the hull plating.
If the vessel has a flat bottom and sides, the plating can be ordered from a drawing called the "shell ex- pansion." This drawing is made by "expanding" the transverse frames at their proper position on the ves- sel's length and drawing in all frames (transverse and longitudinal), decks, keelsons, stringers, bulkheads, margin angles of double bottoms, bilge keels, side fender angles, etc. For the length of the parallel middle body the bot- tom plates are then drawn in with their edges parallel to the center of keel and having the width at the mid- ship section. The side plates are drawn in parallel to the expanded sheer line in the same way. The girthed frames beyond the parallel middle body are divided into the number of equal parts in which there are plates on the midship section, and fair lines representing the center line of longitudinal plate laps are drawn through the points of division. Steal- er plates as necessary are introduced at the extreme ends.
The above shell expansion cannot be applied in ordinary plates for ves- sels having the usual shipshaped hull, because such a hull has a "warped surface" which means that it cannot be "expanded" or rolled out onto a plane. Plates for these vessels are ordered from a model on which the shell has been laid out just as it would appear when fitted in place. The longitudinal seams of hull plating are single riveted in small vessels, double riveted in medium sized ones and treble riveted in larg- est ones. Butt joints of hull plates are double, treble or quadruple riv- eted. At one quarter of the vessel's length, from the bow and stern, the shearing stresses in the hull plating are maximum, so that in large ves- sels it is common to introduce an additional row of rivets in the hull seams at these localities.
The size and spacing of rivets is given in riveting rules published by the American Bureau of Shipping.
Hull rivets usually have counter- sunk points on the outside, the rivet filling the hole in the plate and being slightly convex. The countersinking extends nearly through the plate. All rivet holes should be punched from the faying surface and slightly small- er than the rivet diameter. The holes should then be reamed to proper size for the rivet, the reaming re-
FIG. 69— CONSTRUCTION OF FENDERS AND BILGE KEELS
moving the weakened steel imme- diately around the punched hole. No holes in curved or furnaced plates at the bilge or the stern should be punched. These holes are drilled after the plate has been fitted to the hull. Where two thicknesses of plating are riveted together, the size of rivet should be governed by the thicker plate.
Fenders
All harbor vessels should be fitted with side fenders to protect the hull when rubbing against docks or other vessels. These fenders are construct- ed of heavy wood securely bolted to the hull structure and having a flat or oval facing strip of metal which is spiked to the fender logs with round spikes having countersunk heads. The number of fenders varies with the freeboard and they are usually from three to six feet apart.
The upper fender is at or near the upper deck and follows this deck from stem to stern. The lower fender is near the water line at the lowest point of sheer and is usually parallel
Shelter Dec hed Ve^el-
to the upper fender over that portion of the hull which is vertical or nearly so. The lower fender is not neces- sary at the bow or stern where the sides overhang to such a degree as to render it superfluous.
Tugs are an exception to this rule since they have the lower fender run- ning to the bow with sometimes an additional bow fender. Tugs also have the space between the upper and lower fenders filled with wood as in Figure (69-a). This minimizes the likelihood of damaging the hull if the fender on a vessel alongside is between those on the tug. This crude precaution is improved upon by "swinging" fenders of hard wood which are suspended from pad eyes as in (Figure 69-b). When not in use these fenders are swung up on the deck to reduce the resistance which would be considerable if their ends dragged in the water. Fenders of steel with hollow half round sec- tion may be riveted to the hull (Fig- ure 69-c). The space between these steel fenders and the hull may be empty or filled with cement.
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FIG. 70— HOW DECKS ARE CLASSIFIED
46
The Design and Constntction of Power Work Boats
The degree and period of rolling in a seaway may be considerably re- duced by "bilge keels" which serve as a paddle surface in the direction of roll. The further these bilge keels are located from the center about which the vessel rolls, the greater will be their effect. Care must be ob- served that they are far enough under the bilge curve not to project beyond the vertical hull sides and thus strike docks, etc. They must also be far enough up on the bilge so that their outer edge is not below the line of the vessel's bottom. These consid- erations limit the width of bilge keels, whose construction is shown in cross section by Figures 69 a-b-d-e-f and g. These keels are located at the mid- dle of the vessel's length and lie in a diagonal plane. They should co- incide with the flow of the stream lines so that they do not introduce resistance to propulsion. Usually it is satisfactory to place the bilge keel in the plane of a bilge diagonal. Their length is from one-third to one-half that of the vessel and the ends should be faired into the hull surface by a curve which gradually reduces their width.
Sometimes bilge keels carry away (are torn loose) in heavy weather or by striking a submerged obstacle. For this reason they are attached to steel hulls with tapped rivets so that no serious leakage will occur in this event. If the bilge keels are formed of a plate attached to angles or tee bars, the rivet connections to the hull are stronger than those between the bilge keel plate and the connecting bar so that if the plate is torn off
the hull rivets will hold the structural bar.
Wooden bilge keels and fenders are usually through bolted to the vessel's frame and sometimes to clamps, stringers and bilge keelsons. (Fig. 69-a).
Steel fenders and bilge keels are riveted to the shell plating and may be of a single bulb angle or tee angle (Figure 69 e and f). They may be formed of a bulb plate con- nected to the hull by single or double angles or a tee bar (Figure 69 b and d). Sometimes a plane plate is em- ployed, the outer edge of which is re-enforced with a steel half round bar on one or both sides (Figure 69-d). Large vessels have bilge keels formed of two flanged plates with a stiffening bar at their outer edge and the space between the plates filled with yellow pine in pitch or with cement (Figures 69-g).
Decks may be classified according to their location as those in the hull proper and those in the superstructure above the hull. Their number varies from one in small vessels, to eight in the largest. The names of decks vary with their location and the purpose which they serve, there never having been a standardization of the terms applied. It is becoming popular to letter or number them in order, from the topmost down or the reverse. The confusion in naming decks forming a part of the hull has not been as serious as that concerning those in the superstructure.
Hull decks contribute structural strength to the vessel, while super- structure decks are merely light plat- forms or shelters.
If the vessel's sheer line is con- tinuous from bow to stern, the up- per hull deck is made watertight ex- cept inside of deck houses which may be built upon it. This upper deck is usually the most strongly constructed of them all (Figure 70-b). When the continuous upper deck is not the main strength deck, the next deck below it constitutes the top of the hull proper. Then the hull sides between the second or "main" deck are lightened and merely serve as a shelter to the space between these two decks. Such a lightened upper deck is a "shelter," "shade," or "awning" deck and is found in vessels carrying cargo above the main deck. The freeboard of such vessels is considered from the second or main deck to the water Iilane (Figure 70-a).
Cargo vessels often have "deck erec- tions" (Figure 70-c) where the hull sides are extended above the main deck to produce a "forecastle," "poop" or "bridge." If these erections (some- times called islands), are short, they do not assume the stresses set up in the hull by hogging or sagging on the waves, being therefore of rela- tively light construction. When longer than one-tenth of the hull length, however, it is necessary to strengthen their construction since the hull stresses are transmitted to their structure. The depressed spaces on the main deck included between the poop, bridge and forecastle, are termed "wells."
Poop decks are sometimes only half of the normal deck height of eight feet above the main deck. Such low- ered poops (Figure 70-d) are called quarter decks.
CHAPTER XI
Decks for Wood anci Steel Boats
'LL decks exposed to the weath- er should be properly drained and should afford a foothold when wet. The first of these results is obtained by fitting drainage pipes or "scuppers" in gutters or "water- ways" around the deck margin and by the introduction of large openings or "freeing ports" in the bulwarks if the vessel has these.
Rounding decks up athwartships is frequently resorted to for drainage purposes. The round up (called "camber" or "crown" of the deck) is a measure of the deck height at the center line above the level at the ship's side and a customary de- termination thereof is one-quarter inch per foot of deck width at each point in the length. The deck is then arched to the arc of a circle which passes through the points at each side of the deck and the raised point on the vessel's center line. (Fig. 71-a.)
Instead of this rounded form, the decks may be sloped on each side of the center line where a circle joining the sloped sides eliminates the sharp ridge which would otherwise appear. (Fig. 71-b.)
Since a vessel is very seldom on an "even keel" that is perfectly up- right, and because even with cam- bered decks the water does not drain well when the vessel is listed, the decks may be perfectly flat athwart- ships. (Fig. 71-c.) This avoids the expense of sawing or bending wooden or steel deck beams and affords a deck which is satisfactory for all practical purposes.
"Sheer" is the upward curve of the decks at the bow and stern of a vessel and is common to most vessels. The lowest point of the curve show- ing the deck elevation is called the "lowest point of sheer" and is located amidships or else between the mid- ship section and the stern. (Fig. 71- d.) The heights of the forward and after deck end" above the lowest point of sheer are called the "rise of sheer forward" and "rise of sheer aft," respectively. The rise of sheer is greater at the bow than at the stern, while the degree of sheer is greater in small than in large ves-
sels. The lowest point of sheer is usually between the midship section and the stern.
IIoiv Sheer Is Determined
Amount of sheer is arbitrarily de- termined and is governed by
(a) The type of vessel
(b) The appearance
Given a certain depth of hold it is apparent that the raised forward and after deck will result in greater free- board, so that the decks will be relatively dryer in rough water. Double ended vessels such as ferry boats have a "reversed sheer," i. e., the deck is higher amidships than at the ends.
Straight sheer lines (Fig. 71-e and f) are becoming very common in vessel design. The principal advan- tages are (a) simplicity of construc- tion, (b) increased depth of hold amidships for a given freeboard at the bow and the stern. Naval vessels, power yachts and the famous Eng- lish "turret deck" ships first em- ployed straight sheers.
There are three methods of adapt- ing this design to vessels. The first is applicable to small vessels oper- ating in choppy water where more freeboard is needed forward than aft. The deck is pitched as in (Fig. 71-e) and the degree of rise varies from one foot for every 25 feet of length, down to one foot in SO feet of leng*h. The larger pitch applies to shorter ves- sels.
If the profile of the vessel with sheer lines the deck is horizontal (Fig. 71-f) and a forecastle is constructed at the bow. This forecastle may be from 18 inches to eight feet above the main deck. The low forecastles are used in small boats and the ones of maximum height in larger vessela
If the profile of the vessel with straight sheer appear inferior to that with curved, the bulwark rail may be curved as in (Fig. 71-g) and the deck made straight.
Wooden Decks
Wooden decks are most frequently employed in all types of vessels, mainly because of the good foothold which they afford when wet. In many
47
steel vessels the weather deck is of wood and decks in the hold are of steel either bare or covered with a suitable material.
The thickness of deck planking and method of its installation depend upon the deck where fitted. If the deck is a part of the hull and contributes to the vessel's strength, and if the traffic on the deck is heavy so that excessive wear in the deck planking may be expected, the planks are made from two to four inches thick. The width of deck planks varies from 2J^ to 6 inches.
All decking should be laid with the grain of the wood vertical and wher- ever planks rest on beams, plates or other structural members, the bear- ing surfaces should be painted before the planks are laid. The plank seams may be straightened parallel to the longitudinal center line of the deck, or they may be curved parallel to the side of the deck.
The outer boundary of deck plank- ing is fitted with a wide "margin plank" against which the deck planks are butted with "nibbed" ends at the bow and stern or where curved deck openings cut the plank seams at an acute angle. (Fig. 72-a and b.) Planks laid parallel to the deck side have a wide "kirig plank" on the center line against which the plank ends are nib- bed over wooden butt blocks fitted underneath.
Material Used for Decks
Yellow pine, white pine, teak, ma- hogany, oak or fir are the woods used for decking. Of these the pines and fir are most general in commercial vessels. Oak is some- times used for margin or king planks. Teak and mahogany are employed in yacht work.
The lumber should be close grained, free from knots, checks and other defects and well seasoned. Planks should be planed smooth on all four sides, the vertical edges being slightly bevelled to allow for calking.
Planks up to IJ^ '"ch thick may be blind nailed or screwed to the wooden deck beams, screw heads being count- ersunk and plugged with wood. Light wooden decks on steel beams or
48
The Design and Construction of Poiver Work Boats
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FIG. 71— DRAWINGS SHOWING CONTOUK OP DECKS AND SHEER
plating should have wooden nailing strips bolted to the beams under the planking.
Decks from two to four inches have carriage bolts (round headed) countersunk in the planking with the nut under the beam. A cotton thread dipped in white lead is fitted as a ring under these bolt heads and is called a "grommet." Deck plugs over bolt heads should have their grain parallel to that of the planking and be dipped in white or red lead.
Planks from 1^ inch up to 4 inches thick have the seams calked with from one to three threads of cotton or oakum, after which the seams are filled (payed) with pitch or seam cement. The deck surface is then planed and sandpapered smooth.
Planks on weather decks less than 1J4 inch thick are of tongue and grooved material over which canvas
(No. 6 or No. 8) is tacked on thick paint, marine glue or felt. The can- vas must be tightly stretched before tacking with galvanized or copper tacks and is finally given three coats of lead paint, the final coat being buff, gray or other approved color.
Fig. 12) (a to h) shows wooden deck construction, (a) to (d) being for superstructure decks, (e) and (f) for main decks, (g) and (h) for lower decks and cockpit floors re- spectively.
The superstructure deck planking is laid on beams spaced from 15 to 20 inches apart and resting on the house cap log as shown. The inner house sheathing or panelling extends be- tween the beams, filling blocks being fitted in the space over the cap log. Lead sheets are tacked on; the can- vas under all deck fittings, or wooden blocks may be substituted to protect
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FIG. 72— METHODS OF LAYING DECK PLANKS
the canvas and prevent cutting it with the sharp base of the metal filling. Scuppers are located to drain these decks.
Main decks (Fig. 12>-^ and f) in wooden vessels have extra heavy beams, particularly in tugs or other vessels which must withstand side crushing. These beams are from 18 to 24 inches apart and their attach- ments have been discussed under stanchions, clamps, shelves and knees. These decks are always calked water- tight.
Lower decks (Fig. 73-g) are water- tight in living spaces but not in cargo holds. When such lower decks are very short platforms, they are called "flats" and may be fitted locally over hold beams or built up as separate structures on suitable stan- chions, carlings and beams only partly across the hold. Flats in the engine room may have gratings or corrugated plating substituted for the wood planking, or sheet copper ham- mered rough may serve to protect the wood against the damage due to placing heavy machinery parts on the fiat when conducting repairs. Copper is not recommended because of the slippery surface caused by grease.
Linoleum Is Good Covering
Linoleum forms an excellent cov- ering for hold decks in living quar- ters since it is warm, easily cleaned and neat appearing. It varies in thick- ness (good quality Navy) from % inch to ]4 inch and should be care- fully laid at a temperature of about 70 degrees. In unrolling cold linoleum cracks will develop. The linoleum should be rolled out flat in the com- partments where fitted and be allowed to lie unfastened for several days. After this it may be cemented or nailed to the deck (steel or wood) and no bulges will develop. All hatches or other deck openings in the linoleum should be fitted with sheet brass bounding strips at least }i inch wide.
The decks in galleys, toilets and lamp rooms should be cemented and are usually tiled. In wooden vessels the deck planks are first covered with watertight sheet zinc or lead which is flashed up the bulkheads to a height of 6 inches. Then from }i inch to l]4 inch of neat cement mortar is placed on the metal and finally the nonporous or glazed tiling is placed on the cement. The tile is hammered down level by striking a plank laid thereon and a thin grouting or cement wash is applied to fill the cracks be- tween the tile. It is well to use rounded tile in the edges formed at the bulkheads and to carry the tile
Decks for Wood and Steel Boats
49
up the bulkheads. This permits wash- ing down the deck. Drainage scup- pers should always be installed in cemented or tiled spaces.
Cockpit floors (Fig. 73-h) are be- low the level of the main deck and are not usually fitted in vessels more than 65 feet long. They should always be at least six inches above the load water line so that the sea water can drain freely through scup- pers if waves should be shipped. Such cockpits are termed "self bail- ing." Sometimes ball or flap check valves are fitted in the scupper pipes and these prevent the sea water from flooding the cockpit by washing back through the drain pipes. A water- tight base board is installed all around the edges of cockpit floors to a height of from six to twelve inches, while tongue and groove vertical ceil- ing sheaths the sides of cockpits up to the main deck. A deep coam- ing extends all around the cockpit at the main deck. (Fig. 5>'9^c.)
Decks — Steel Vessels Steel vessels' decks may be wooden planking on steel beams, steel plating on steel beams or composition ce- ment material on light steel plating. In (Fig. 74-a to c) the construction of superstructure decks and decks on house tops are shown. (a) is house top with tongue and groove planks nailed to wooden battens which are fitted in the bosom of the steel beam angles. These angles have their horizontal flanges at their lower edges and are riveted to margin plates around the upper deck house and coaming. The wooden beam strips are side bolted to the vertical steel beam flange with countersunk bolts. The house top overhangs the side and end house bulkheads and a con- tinuous molding angle is clipped to the overhung beam ends. A margin plank extends around the deck edge and the canvas covering is lead flashed to it. The scuppers are close against the margin plank and their pipes pass through the overhang to the deck below.
Fig. 74-(b) shows a house top which overhangs to the vessel's side, forming a shelter to the deck below. The beams of the lower deck house are similar to those in 74-(a) and terminate in a steel stringer plate which is riveted through a stringer angle to a sheer plate. Stanchions of pipe, solid round bars, angles or other structural steel shapes support this marginal deck girder from the deck below. Three alternative con- structions of the margin girder are shown.
Fig. 74- (c) is a steel house top with light plating joggled over steel
beams and riveted to them. The plating is 7.6 pounds to 10.2 pounds per square foot (3/16 inch to % inch) in small vessels such as tugs and has an overhang formed by two angle bars as shown or by a channel (Fig. 74-d). Sometimes no overhang is introduced, the house margin being plain as in Fig. 74-(l) or having the house side plating extended up to form a waterway. (Fig. 74-m.) The house top plating in large vessels may
which a cement or bituminous com- pound is laid as a substitute for wood.
Decks planked with wood may have their beams fitted on alternate frames, the timber being stiff enough to sup- port itself over the intervening span with ordinary loads. Steel plated or cemented decks should have beams on every frame.
A wide heavy "stringer plate" forms a marginal girder for all decks in steel vessels and is connected to the shell
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FIG. 73— CROSS-SECTION OP WOODEN DECK CONSTRUCTION
be covered with wood planking or a composition deck cement (Fig. 74-e). Half round steel molding bars are usually riveted at deck edges for ap- pearances as shown in the figures.
Hull decks exposed to the weather in steel vessels are more strongly built than the superstructure decks. They may be composed of steel beams partially plated over and covered with wood planking; of steel beams cov- ered with steel plating; or of steel beams covered with light plating on
plating by a continuous stringer angle (Fig. 74 (f) and (g).) In lower decks where the frames pass up through the stringer plate, the con- tinuous stringer angle is fitted in- side the frames and riveted to the reverse frame or to a clip on the frames if these are of bulb angle. (Fig. 74-h.) Intercostal clips join the edge of such stringer plates to the shell plating and the space be- tween frames outside of the con- tinuous stringer angle is filled with a
50
The Design and Construction of Power Work Boats
T?e.moyeD To ihou Sr£e.L Beoms.
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PIG. 74— CONSTRUCTION OP DECKS OF STEEL VESSELS
wood block, cement or a forged or a cast shoe of angle section.
Tie plates from six to eight inches wide are fitted under the deck plank- ing and serve to connect the deck sides and ends. Margin plates are fitted around all deck openings to take the planking ends and to re-enforce the locally weakened structure. (Fig. 74-n.) The deck planks are cut to fit over all deck plates and are bolted to the deck beams as in the case of wooden vessels.
Covering for Steel Decks
A waterway angle (Fig. 74-f and n) is fitted from 9 to 12 inches inboard of the stringer angle against the margin plank or the composition deck covering. The object of fitting planking or other deck covering over steel decks is to afford a secure foot- hold when the decks are wet.
Asphalt cement mortar or numer- ous patent compositions may be sub- stituted for planking. If asphalt is
used it should be specified to the consistency employed in the street paving of cities in the locality in which the vessel is to operate. This will insure good wear and provide against undue softening in warm weather.
Bonding clips of flat metal are bolted or spot welded to the deck plating before putting on the deck covering (Fig. 74-p). The thickness of composition deck covering ,b from one to two and one-half inches.
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73— CONSTRUCTION OP CEILINGS DOUBLE BOTTOMS
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PIG. 75— CONSTRUCTION OF CEILINGS
Steel weather decks are sanded while the paint is wet to provide a footing.
Watertight lower decks are fitted over deep tank tops and are com- pletely plated over with steel beams on every frame. Where side deck margins butt against the hull plating or steel bulkheads pass through them, it is necessary to fit a continuous stapled margin angle around the frames and the bulkhead stiffeners (Fig. 74-i). It may be necessary, particularly if the hull has a slope as at the stern, to cut the frames or the bulkhead stiffeners and bracket them above and below the deck (Fig. 74- k). In this case a continuous mar- gin angle passes all around the deck and the frame; brackets are cut to clear this angle. These brackets are at least three times the depth of the frame or stiflfener angles to which they are fastened and have their inner edges flanged.
All steel deck beams except those
Decks for Wood mid Steel Boats
51
abaft the transom (in overhung sterns) extend athwartships. The beam at the frame to which the stern- post is connected is called the tran- som beam. Aft of this the beams radiate (Fig. 74-n and o) to coincide with the cant frames previously de- scribed. These "cant beams" are bracketed to the transom beam and to the cant frames.
In cargo holds it is necessary to prevent package freight or bulk solids from getting between the vertical floors and keelsons of the ship's bottom. This is done by building a wooden platform called a "ceiling" on the floor tops (Fig. 75-a). Ceiling timbers are framed together in sec- tions which can be removed for in- specting, cleaning or painting the
bilges. The planks do not contribute strength in steel vessels and are about two inches thick. If dry bulk cargo such as grain or coal is car- ried, the ceiling should be "dust tight" by building it of two thicknesses of one inch planks with the seams stag- gered. Where keelsoms project above the floor tops in single bottomed vessels, it is necessary to fit padding timbers to protect the structure and cargo from damage.
Ceiling on double bottoms is raised some two inches above the inner bot- tom plates by "sleepers" of 2x4 timbers which extend athwartships and are spaced about four feet apart. This is to permit moisture on the inner bottom to drain the bilges without damaging the cargo. Fill-
ing timbers are fitted between the frames where the ceiling joins the hull sides and "cargo battens" are installed inside the vertical side fram- ing and on the bulkhead stiffeners in package or miscellaneous cargo holds. These battens may be in built up sec- tions bolted to the reverse frames, in single strips bolted to the reverse frames or in single strips supported by "batten hooks" (Fig. 7S-b). Cargo battens in steel ships longitudinally framed are fitted vertically (Fig. 7S-d). The battens are usually l^x 4-inch timbers spaced about 6 inches on centers. Large wooden vessels have perma- nent ceiling inside the frames. Tank vessels have no ceiling, the liquid cargo occupying all the spaces be- tween the framing.
52
The Design and Construction of Po7vcr Work Boats
ONE OF THE FAMOUS "AKK MODEL" FISHING BOATS BUILT AND OPERATED BY THE SOUTHWEST FISH COMPANY OF VERMILION, OHIO
CHAPTER XII
Constructing tne Deck House
OECK houses arc usually fitted above the hull proper to pro- vide living or operating ac- commodations. They are usu- ally of wood in wooden vessels and of wood or of steel in steel vessels. The structure is made as light as possible without being too weak to withstand the rough seas or to support other houses, lifeboats, etc., which may be above them. This light construction is in order not to raise the vessel's center of gravity by the presence of excessive topside weights, for if made too heavy, especially in small vessels with large deck erections, the vessel would be rendered unstable.
The house tops usually follow the sheer line of the upper hull deck, being sheered and cambered or straight and flat as previously de- scribed under "decks." The forward end of deck houses are sometimes perpendicular to the sheer line at that point or else they are at an angle half way between a vertical line and one perpendicular to the sheer at the point where their lower edge strikes the deck (Fig. 76-a). The after ends of deck houses are usually vertical. For structuial simplicity, particularly with straight sheers, the forward and after deck house ends may be square to the deck. Another reason for this will be discussed under "doors and windows."
Deck Houses Generally Rounded
In plan view the forward and after deck house ends may be straight across the deck and joined to the house sides with a radius of from nine to eighteen inches. This is nearly always done at the after end, but the forward end, particularly of pilot houses is more often rounded. In lower deck houses the rounded forward end is laid in by taking a radius equal to the forward width of the deck house. An arc is drawn with this radius, its center being on the vessel's longitudinal center line. This arc is then joined to the house sides by one equal to one-quarter or one- third of the forward house width. Pilot house fronts may also be drawn in this way or by a semi-circle whose diameter is the width of the pilot
house. No gain is experienced by rounded house ends particularly in low speed vessels, and it is be- coming customary to make the house front straight with rounded corners. This affords more room in the house and simplifies construction.
Deck house sides may be parallel to the upper hull deck side, at a dis- tance in from the rail sufficient to afilord a passageway beside the house. This passage is from 18 inches to 24 inches wide in small boats and up to five or six feet in large boats. Sometimes the house side is straight and parallel to the longitudinal cen- ter line, but unless the vessel has a long middle body, care must be taken not to reduce the interior house room too greatly. It may be pos- sible to build the forward house sides straight and parallel, tapering the after sides to keep the outside passage at nearly a constant width.
Height of Deck Houses
The usual height of deck houses, measured from the top of the plank- ing under foot to the top of the planking overhead, is from seven to eight feet. Sometimes in shallow draft river vessels the height is more than this, as much as 10 or 12 feet. Pilot houses are usually higher than other deck houses which may be abaft them on the same deck. This permits of placing transom windows in the after end of the pilot house above the top of the other deck houses, so the helmsman can see astern. Pilot house floors are raised above the normal deck level to enable the wheelman to see through these windows and close down over the bow.
Small boats may not have sufficient depth of hold to permit the ma- chinery to be entirely below the upper hull deck. In this case head room and ventilation are obtained by building a low deck house or "trunk" whose height is from two to four feet above the upper hull deck.
The length and width of deck house in a given boat is determined by the accommodations it must en- close as well as the external deck arrangement which is influenced by
53
the service which the vessel is to engage in. For example, although a certain number of staterooms, gal- ley, messroom, upper engine room and toilet spaces could be placed in one deck house on the upper deck, there must be a passage outside the house on each side of the ves- sel, or a large hatch may be re- quired on the forward deck. These factors will limit the width and for- ward ending of the house.
Then perhaps a mast with a heavy boom and hoisting winch may be needed forward, further affecting the forward end of the house. If the vessel is to tow astern, heavy towing bitts must be placed on deck behind the deck house. These bitts should be located as far forward of the stern as possible to permit of easy steering while towing. This will affect the after end of the deck house.
Wooden Deck Houses
Figure 76-d is a cross sectional elevation of a typical wooden deck house side. The lower coaming or "sill" is of heavy timber and is se- curely bolted on top of the deck planking, the bolts passing througla the beams of the deck below. A stopwater of flannel dipped in thick white lead should fit between the sill log and the deck planking to prevent leakage under the house sides into the cabin. In Fig. 76-t the house is a trunk built over a deck open- ing and the sill is bolted directly to the carling which supports the cut beam ends. Here the deck plank- ing is fitted close beside the outer edge of the sill and the seam thus formed is calked in the same way as for the other deck seams.
A frame work of vertical stanchions is erected on the sill. These stan- chions are from two to four inches molded and usually four-inch sided, having their lower ends notched into the sill and their upper ends into the "cap" or upper coaming timber. The vertical stanchions are spaced from two to three feet apart. At the height of the window sills, it is common to fit horizontal strut timbers between stanchions and
54
The Design and Coiislnictioii of Poivcr Work Boats
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sometimes diagonal brace logs are built into the house framing.
The cap is above the tops of window frames and may be under the house top beams with filling blocks between them, -or may be at the ends of the beams. Various wood house tops have been con- sidered under "decks" in Chapter XI.
Long steel holding down bolts are passed from the upper side of the cap to the under side of the beams or carlings on the deck below. These rods are from l^-inch to ?4-'nch in diameter with nuts over washers on their upper and lower ends. The rod spacing is from six to eight feet and they should be located close to a heavy stanchion so that when tightened up they will not cause a spring in the cap or carling.
How Sheathing is Fastened
Deck house sheathing is fastened outside and also usually inside of the framing. The material used in com-
mercial vessels is usually pine al- though mahogany or other hard woods are still employed in yachts, especially for the inside sheathing. Formerly the sheathing was panelled, but it is now usually of tongue and grooved planks.
The outside sheathing is from fl- inch to ^-inch thick, the planks run horizontally and the whole is usually painted a light color. A half round molding may be fitted at the level of the window sills.
Inside sheathing is panelled in pass- enger vessels but it is becoming more usual to make it of V" chamfered tongue and groove planks built in vertically. The thickness of inside sheathing is from ^-inch to §^-inch and the finish is natural wood or stained. A "wash board" or lower molding plank from four to six inches high and ^-inch thick ex- tends around the inside of deck house sheathing and partition bulk- heads as in Fig. 76-d. A similar
upper molding, notched around the beams is often fitted. Sometimes a quarter round molding strip is sub- stituted for this upper molding.
Care should be taken that the seams of inner and outer sheathing planks are parallel to the edges of doors and windows. All sheathing should be blind nailed to the stud- dings and hammer marks should not show.
The deck overhead in a deck house is sometimes panelled but only in saloons of passenger boats. Usually it is sufficient to finish the under side of the house top planking in a smooth and neat manner. Deck beams are sometimes boxed in with light sheath- ing to make them appear massive.
Where considerations of draft render it desirable to eliminate un- necessary structural weight, the in- side sheathing is omitted entirely or is composed of composition wall board. This compressed pulp ma- terial is from tV-inch to A-inch thick and should be treated so that it will not absorb moisture. It is obtained in sheets from three to five feet wide and should be carefully fitted. Molding strips of stained wood, 54- inch thick by 2 to 4 inches wide should fit over the joints and the intermediate nailings. Wallboard
should be nailed at not more than 6-inch intervals along the edges and intermediate rows of nails should be not over 18 to 20 inches apart so that buckling will not ensue.
Pilot Houses of Wood
Wooden deck houses are sometimes fitted on steel vessels as in the case of pilot houses or of light deck houses in shallow draft steamers. Pilot houses of wood are to minimize the effect of surrounding steel on the compass needle. All metal with- in a radius of IS feet from the compass should be non-magnetic to render the error in reading less marked. Even with this precaution a steel vessel which pursues a fixed course for a considerable period, or which lies at a dock, will become polarized by the earth's magnetic lines of force, so that the vessel itself is one large magnet which will act upon the compass needle just as two mag- nets affect each other. In order to overcome this source of error in the compass reading, compensating mag- nets are fitted in the binnacle stand which carries the compass and the ship is "swung at her anchorage" or turned around from time to time. If the modern gyroscopic compasses are used, these troubles are avoided. Pilot houses are often made of steel regardless of the above discussion, for purposes of strength and be-
Constructing the Deck House
55
cause of the relatively slight in- crease in error when the rest of the ship is steel and when the com- pass is properly constructed and at- tended to.
Fig. 76-f shows the attachment of a wooden pilot house to a steel deck. Observe tlie deck plate to which the house sill is bolted and also the firring strips on the steel deck beams to which the light deck- ing inside of the house is nailed.
The lower deck house or "texas" of a shallow draft river vessel is sometimes attached to a vertical steel coaming plate as in Fig. 76-g. Here the coaming plate is riveted to a deck plate by a coaming angle and the sill timber is bolted on an inverted angle bar several inches below the top of the coaming plate. The outer sheathing should cover the top of the coaming plate and a molding strip be fitted for sightlines as shown. The extreme after end of the "texas" is exposed to constant splashing from the stern wheel and is therefore made watertight. This can be done either with two thicknesses of closely fitted tongue and groove planking running at right angles to each other, or by making the bulkhead of light sheet steel or galvanized corrugated steel.
Steel Houses for Tugs
Deckhouses of steel are sometimes fitted on wooden vessels such as tugs which navigate rough waters. The lower attachment of such a house to the wooden deck is shown in Fig. 76-h where the steel lower coaming plate is bolted sidewise through a heavy sill log. The lower coaming angle is riveted to the coaming plate and secured to the deck by bolts with countersunk heads which pass vertically through the sill log and deck beams below. A can- vas stopwater dipped in thick white or red lead is inserted between the coaming angle and the sill log to prevent leakage.
An alternative construction is given in Fig. 76-k in which a steel deck plate is fitted on the beams under the deck planks. This plate is through bolted to the deck beams and the lower house coaming angle is riveted to it and to the lower coaming plate
Steel houses in steel vessels (Fig. 77-a, b and c) have their side and end bulkheads composed of:
1. A lower coaming piate which is secured to the deck plating or to a tie plate under the deck planking by a lower coaming angle.
2. An upper coaming plate which fastens to the house top with an up- per coaming angle in one of the ways already described.
3. House side plating which fits
between the upper and lower coam- ing plates and is stiffened by vertical angle bars bracketed at their tops and sometimes at their bottoms.
The lower coaming plate is usu- ally %-mQ.h to A-inch thick (weigh- ing from 10.2 to 12.8 pounds per square foot). Its height above the deck beams is from 9 to 12 inches, so that it need not be cut where doors are fitted but the door sills rest on its upper edge. The lower coaming angle is of the same thick- ness as the lower coaming plate. The vertical flange of this angle is deep enough to project above the deck planking, being from 2}/^ to 3j4 inches high and secured to the coaming plate by a single row of rivets. The deck flange of this lower coaming angle is single riveted to the deck or tie plating and is from 2^ to 3 inches wide. The tie plate is from 8 to 15 inches wide and weighs from 7.6 to 10.2 pounds per square foot.
The upper coaming plate is from 7.6 to 10.2 pounds per square foot and from 6 to 9 inches high. The upper coaming angle is of the same thickness and has flanges from 25^2 iiiches by 2J^ inches to 3 inches by 3 inches, single riveted to the coam- ing plate and the house top. The tops of window and door frames fit against the lower edge of the upper coaming plate.
The intermediate house side plating weighs from S.l to 7.6 pounds per square foot (from J^-inch to A-inch thick) and is cut out where win- dows and doors are fitted. Some- times this plating extends to the house top and no upper coaming plate is fitted. The exterior of the house side plating may be flush with butt straps fitted to the seams on the inside (Fig. 77-c) or it may present a paneled appearance by fitting these butt straps on the outside of the seams between the upper and lower coaming plates (Fig. 77-a and b).
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FIG. 77— CONSTIiUCTION DETAILS OF STEKL HOUSES
56
The Design and Construction of Power Work Boats
Doors are of the same material as the bulkheads through which they afford a passage, except that some- times wooden doors are fitted in steei bulkheads. Watertight doors are usually of steel and are fitted to watertight bulkheads. They are ar- ranged to hinge and clamp shut with dogs or to slide vertically or horizon- tally.
Fig. 78-a is a hinged watertight door on a steel bulkhead. The door opening is 2 feet 2 inches wide by 5 feet 6 inches high and has rounded corners to prevent weakness at these points. A continuous forged frame angle is riveted around the opening or "arch" to make up for the strength lost by cutting out the bulk- head plating. This frame angle bears against a rubber gasket on the door, the gasket being secured to the door plate by rabbeted steel strips fas- tened with composition machine screws. The door plate is stiffened by an angle around the edge or the
plate may be "bumped" out as an alternative. When closed the door is held tight by "dogs" which clamp over bronze wedges on the door plate with handles on each side of the bulkhead as shown. The bolt about which the dogs pivot, passes through a bronze bushing and has a nut on one end to permit removal.
Vertical sliding watertight doors are most frequently used in large vessels and may be operated from the deck above or from below. They slide in cast steel guides riveted to the bulkhead on each side of the "arch" and have wedges on the door which bear against sloped flanges on the guide castings and force the door against the bulkhead when closed. The door may be raised and lowered by means of a pinion and rack or by a threaded spindle pass- ing through a fixed nut on the door. The rack shaft or the spindle are turned by an endless chain on a sheave
KI(J. 7S~WATi:i! TICIIT DOOlt.S, All! POUTS AM) DEAD LIGHTS
or by electric motors. Sometimes a releasing device is attached so that the door may drop quickly in case of accident.
The hinged watertight door is most common in tugs and other commercial power boats.
Interior Doors
Interior doors through joiner bulk- heads are similar to those used in building construction, being of wood :iiid panelled. They are usually hcav ier than doors of buildings and should be carefully fitted. Some- times horizontal sliding doors are used where space is restricted, such as in staterooms, but this type is not satisfactory in practice since difficulty in opening or closing arises if the door leaves the guide runners.
Deck house doors of wood or steel sometimes are in halves so that the upper part may be opened for ventilation. The upper and lower halves bolt together and the lock is on the lower half. A sliding bolt holds the upper and lower halves of such doors together. Pilot house doors may have glass fitted in the upper half, but if care is not taken the glass will be broken frequently. Wired plate glass offers a solution of this difficulty.
Deck house doors have their upper and lower edges parallel to the sheer and their sides vertical. This cus- tom renders doors very expensive un- less the sheer is a straight line when all doors are similar.
Occasionally it is necessary to fit a bulkhead in passages for strength only, in which case passage through the bulkhead is afforded by an open "arch" re-enforced by a bounding angle and the door is omitted.
Openings in the sides of the hull
are called "ports" and are employed
for loading cargo or for furnishing
light and air to the living spaces.
Cargo ports are not fitted in wood- en vessels and should be as small as possible in steel ones, that the hull strength may not be seriously reduced. Coastwise vessels with "well" decks have large swinging ports at the sides of the wells. These are not com- mon to power vessels and will not be studied.
Small side ports often also serve as doors to the upper between decks in large vessels and are in halves with a deadlight in the upper por- tion. They are held watertight by strongbacks or by dogs around tlie edges and a gasket is fitted on the
Construcliiig the Deck House
57
rim which bears against the angle framing arch. This type is sekloni employed in power boat construction.
Construction of Air Ports
Air ports (Fig. 78-1)) consist of a circular glass plate in a metal frame which is hinged to a casting riveted or bolted to the hull. The glass is from .>^-inch to J^-inch thick, depending upon the diameter. The size of an airport is expressed by the clear diameter of the glass and ranges from 6 inches in small boats to 18 inches in large vessels.
The rim in which the glass is fixed is usually of polished brass or com- position metal, although galvanized cast steel is sometimes used. The glass is secured to the rim by a circular brass ring of quarter round cross section which is held in place by small machine screws. Cement is usually introduced between the glass and the rim to prevent leakage. Some- times a cast metal cover or "dead- light" is hinged over the glass rim on the inside of the vessel. This is usually hinged up and hooked to the deck overhead. Its use is to close the port hole in case the glass becoiTies broken. A rubber gasket is packed into a groove around the edge of the deadlight cover and a similar gasket is on the frame casting which is riveted to the hull.
Circular ridges on the glass rim bear on these gaskets when the port is closed and when the cover is down and prevent the entrance of water into the vessel. Three hinged eyebolts provided with butterfly nuts are equally spaced around the edge of the port and the cover and swing into lugs on the rim of these. The ports are held tight against the hull by screwing down on the nuts. A gasket is fitted between the airport frame and the hull on the outside, while a ring over this gasket fits securely to the frame. The frame casting passes from the inside of the inner sheathing to the outside of the hull planking or plating. Usually a square wooden frame surrounds the airports on the inside of the hull and in large wooden vessels this frame should be bevelled to afford maximum light diffusion. This is because of the excessive thickness of the hull.
Air ports should be spaced midway between the frames which should not be cut in fitting the ports. Care should be taken not to locate air ports in the hull closer than two
and preferably three frame spaces apart.
Stock air ports are carried by most ship chandlers and can be selected from their catalogs.
Fixed ports or "side lights" admit light only to spaces in the hull which are near the water line or are placed in steel doors of deck houses. The circular glass is in a watertight frame of bronze which is riveted or bolted to the hull and does not hinge open.
Air ports and fixed ports near the hawse pipes are protected by steel bars or as will be studied under "anchor handling."
Wire Glass for Windozvs
Windows of the drop or hinged type are commonly fitted in deck houses. Their advantage is in the increased light and ventilation which they afford, although they are more liable to breakage in rough seas.
This danger was formerly reduced by fitting wooden storm shutters out- side of the windows. The shutters could be taken down and stowed away. Since the introduction of "wired plate glass," shutters are not needed if the panes are of this ma- terial. The glass is poured with a woven wire mesh in it, and acts in the same way as re-enforced con- crete. It will shatter under a direct blow but does not fall out. Pilot house doors should be fitted with wired glass in all cases.
Drop windows when open, fit into a pocket between the inner and outer house sheathing. A recessed grip in the top of the sash should pro- ject above the sill so the window can be raised. The sill may form a hinged cover over the window pocket, to present a pleasing appearance. The pocket is lined with sheet cop- per or galvanized sheet iron with a drain to the outer deck. The sash
FIG. 79— CONSTIiCCTION OF ni.N(iKI) Wl.NllDWS ANU SKYI.KIIITS
58
The Design and Construction of Pozver Work Boats
C. WASHINGTON COLYER, HOCKAWAY BEACH EXCURSION BOAT This craft powered with a 6-cyl., 7^ x 9" Automatic, carries 200 passengers and is operated by a captain
and two hands
slides in a groove in the sides of the frame and the bottom pushes out over a ridge. (Fig. 79-a). Pilot house windows sometimes slide on vertical brass rods (Fig. 79-b). Win- dows with curved panes at house corners are sometimes installed, but should be avoided if possible because of the cost of the special panes and sash.
Hinged windows (Fig. 79-c) have the upper part of the .=ash in two sections hinged together. There is a deep channel at the top of the frame with clearance enough for vhe sash to raise over the ridge on the sill before hinging open. A hook on the house beams keeps the win- dow open. Hinged windows are mostly fitted in the bunk cabins of small vessels or in the after ena of pilot houses which are raised above the deck house enough to permit the helmsman to see astern.
Skylights of wood (Fig. 79-d) or steel (Fig. 79-e) usually hinge up
and may be opened or closed from within by means of a lifting gear. The covers are hinged at the center and the frames must be watertight.
How Skylights Are I'ittcd
Wooden skylights have a wooden coaming bolted to the carlings and end beams of the skylight opening. Engine room skylights should be portable to permit removing machin- ery for shop repairs or renewal. The gabled skylight ends are con- nected at the tops by a heavy rwlge timber to which the hinges are screwed. A drainage groove fits all around the edge of the sashes to prevent drip into the cabin below. This groove drains to the deck at the ends of ridge timber and at the sides of the sashes. Unless the light panes are of wire glass it is necesary to fit a metal grid over them for protection againt breakage by falling objects. A canvas cover or "tarpaulin" fits completely over
MANHATTAN WITH A DECK LOAD
Another Rocliaway Beach excursion boat with same power and capacity as Coli/er
the skylight and is lashed to the coaming in heavy weather.
Steel skylights (Fig. 79-e) usually have circular ports in the sash. The steel coaming is riveted to a plate top which is cut out in way of the hinged sashes, the opening being sur- rounded by an angle bar. The cages of the sash are flanged downward to minimize leakage and a rubber strip or "gasket" extends around the edges. Light metal strips screwed to the sash secure the gasket. Stiff- ening angles or tee bars re-enforce the coaming and tops of the sky- lights. The coaming is riveted to an angle bar and is clipped to the ends of deck beams v.'hich have been cut. A margin plate surrounds the sky- light opening and is riveted to ttie beams and the coaming angle. In small skylights through which it is not necessary to remove machinery or fittings, the deck beams extend across the opening to maintain the necessary strength of the deck.
Skylight lifting gear (Fig. 79-e) may be of several diflFerent types but a usual one consists of a vertical shaft having a handwheei which can be turned from within the cabin. One or more bearings support this shaft and its length varies according to the point from which the sky- light is desired to be opened. A worm at the upper end of this ver- tical shaft actuates a worm wheel keyed to a horizontal shaft. The worm and wormwheel may or may not be enclosed in a casing (Fig. 79-e).
The horizontal shaft has one or more levers keyed to it at one end and pinned to the lower end of a corresponding number of links as shown. The upper ends of the links are pinned to bearings on the sky- light shutters so that rotation of the levers by means of the worm, worm- wheel and horizontal shaft, will raise or lower the skylight shutters. The wormwheel acts as a lock on the worm for any amount of opening of the skylight.
Some skylights have a slotted quadrant bar pinned to the shutter as in (Fig. 79-d). The slots in the ciuadrant engage a pin on the sky- light coaming and the shutter is lifted from the deck above to the renuired amount of opening.
Deck lights (Fig. 78-c and d) are fitted over compartments where ordi- nary airports, sidelights or skylights cannot be provided. They may have a cast bronze frame in which the circular glass is cemented watertight (Fig. 78-c), the frame being screwed to the deck planks or plating. A less desirable type has a thick prism of rectangular glass with beveled edges in thick white lead between deck planks (Fig. 78-d).
CHAPTER XIII
Companions — Hatches — Rails — Awnings
GOMPANIONS are openings in the deck which afford access to the compartments below or above it. They may be in the sides of the deck-house or may con- sist of a hut-like hood over a hatchway having a ladder leading downward.
Fig. 80-a is a sliding companion hatch of wood. It consists of a small house built upon an opening in the deck. A carling at each side joins the deck beams at the ends of the hatch and the intermediate beams which were cut are notched into the carlings. A coaming is bolted all around the hatch to the deck beams and carlings. The front of the com- panion has double doors which vary in height from 30 inches to 6 feet 6 inches. If these doors do not afford full headroom, the top of the com- panion slides back as shown to per- mit entrance.
The sliding top may slope straight back, traveling on girders as shown or it may be rounded as in Fig. 80-b. The minimum width of deck opening should be 30 inches and the length varies according to the slope of the ladder so that the head of an aver- age man would not strike the deck of the opening in coming up.
Companion Slides
Deck houses and trunks of small vessels where the height above the coammg or sill is not sufficient to permit the fitting of doors which are of full headroom height (6 feet 6 inches above the deck), have a com- panion slide or hinged hatch over the low doors (Fig. 81-a and b). The slide is the same, as for companion hatches and has brass metal strips fastened to wooden guide pieces with countersunk screws (Fig. 81-b). The door closes against the front of the sliding top and is usually secured by a hasp and padlock. If the hatch is on a cambered deck and slides athwart- ship, drain holes are cut in the slide strips as shown. If the com- panion top is hinged, the construction is the same except that the slides are omitted and hinges are fitted to the cover at the side away from the door. It is also desirable to install hinged rods at the sides of the hinged cover
so that it may be opened to a degree affording headroom without throwing it completely back upon the deck. Companions of this type are difficult to screen properly and should be avoided if possible.
Fig. 80-b is a full height steel com- panion hatch with deadlights in the sides. The coaming plate and con- nections at the deck are the same as for deck houses and a continuous corner angle bar is riveted to the sides, front and back. The steel
door closes against this angle at the top and sides while a reversed angle at the top of the coaming plate forms a sill. The side and back plates to- gether with the door are of from S.l to 10.2 pound plating (% to % inch thick) with single riveted "equal" angle bars and stiffeners of the same thickness.
Companion doors may be single, double or divided. The latter two types are as in Fig. 81-c and d. They are resorted to where the pas-
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FIG. 80— WOOD AND STEEL COMPANIONS
59
60
The Design and Construction of Pozver Work Boats
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KIG. 81— np:TAIL CONSTliUCTlON OK
sage into which they swing open is restricted. The hinges and locks should be extra heavy and arrange- ments should be made to hold the doors open by brass hooks or by spring catches. Rubber topped buf- fers should be on all doors which open against interior or exterior joiner work having a fine finish.
The deck immediately in front of companion doors is subjected to severe wear so that treads of hard- wood strips are fastened to the decks at this point. Sometimes cast brass or iron plates which are roughened by a pattern or which have a cement or lead filling in grooves, are used in the deck in front of doors.
liow Hatches Arc Classified
Hatches may be roughly classed as watertight, non-watertight, flush or raised. Watertight hatches are fitted over all compartments opening onto decks exposed to the weather.
Wooden hatches are difficult to keep tight. They consist of a coaiu-
COMP.UMO.N SLIDCS AND IIATCIIKS
ing bolted to the carlings and beams around the deck opening. This coam- ing has a rabbet on its upper edge and the hatch cover fits securely into i;. If the hatch is small the top may be in one piece, usually rectangular, composed of tongue and grooved planks with a rabbeted frame and short beams. Hooks on the coaming engage eyes on the cover frame and clamp the hatch closed. Sometimes hinged hasps on the cover fit over staples on the coaming, and pins through the staple hold the cover down. If the hatch is hinged, a pad- lock on one staple may be used and the hooks also be fitted at the sides. (Fig. 81-e.)
Large wooden watertight hatches have sectional covers on portable beams resting in the notched and rabbeted upper coaming timber. A heavy canvas tarpaulin is stretched tightly over the closed hatch by means of an iron bar which is wedged into metal lugs on the coaming. (Fig 81-f.)
Watertight steel hatches when small are called "manholes" or "scuttles" and may open into tank compart- ments below decks as well as to the weather. Manholes to tanks which are seldom entered should be bolted closed as in Fig. 82-a. The opening should not be less than 11 inches wide by IS inches long with circular ends. A forged channel or double angle ring encloses the opening, the cover plate bolting on the upper flange as shown. A gasket of hemp or canvas fits between the cover and the coam- ing ring. The tank, bulkhead or deck plating which has been cut at the luanhole, has a re-enforcing plate or "doublcr" riveted all around the open- ing to compensate for the lost strength.
Manholes of Various Types
Manholes fitted with "strongbacks" arc common to tank compartments. The elliptical manhole plate is in two thicknesses, the upper of which is rarrov<er than the lower. The plates are riveted together and a gasket is fitted on the shoulder as shown in Fig. 82-e. Two shoulder bolts are riveted through the cover plate and "strongback" bars fit over the screwed er.ds of these bolts, extending across ihc narrower dimension of the man- hole. Nuts over washers tighten the cover against a flanged manhole ring.
Hinged manholes fitted with "dogs" are as shown in Fig. 82-c. They may be square, round or elliptical and have a number of forged lugs which engage hinged bolts with wing nuts around tlicir edges. The hinges have an oval slot on the pin to permit of tighten- ing the cover.
This type of fastening is employed for steel watertight or oiltight hatches with hinged covers. A plate coaming from 9 to 48 inches high surrounds the hatch opening and has a coaming angle at the deck. If the coaming height exceeds 20 inches it is necessary to stiffen the plate with brackets and angle clips. A rubber gasket at the upper edge of the coam- ing plate is clamped thereto by an angle or by a flat iron bar. Cast or forged steel lugs riveted to the coam- ing, attach the hinges and the ring bolts.
If the hatch is more than 24 inches square, the cover plate should be strengthened by an angle around the edge. Hatches smaller than this usually have a flat bar around the edge of the cover for strength. Hatches more than 48 inches square should have stiffeners of angles or bulb angles across the cover at inter- vals of 24 inches.
Deck scuttles are of cast steel or composition metal, not less than 18
Companions — Hatches — Rails — Aivnings
61
nor more than 24 inches in diameter. They consist of a flush ring casting, bolted or riveted to the deck planking or plating and having a depressed circular ridge on which a rubber gasket in the cover bears. The cover varies from ^ lo % inch in thick- ness, is roughened on the upper sur- face and has two hinged ring bolts which lie flush in depressions and by means of which the cover may be lifted. The cover is tightened against the ring casting on the deck by means of six bolts with heads resembling horizontal cams, or else by a central bolt which screws into a bossing on a hinged strongback under the scuttle. A special wrench is provided to tighten the scuttle fastening bolts. When the cover is removed a cast iron grating fits into the opening and affords ventilation. This grating may stow in three clips on a bulkhead near the scuttle or may rest in de- pressed lugs under the cover when the scuttle is closed.
Steel cargo hatches usually have wooden covers which rest on portable beams in the hatch opening. A tarpaulin is stretched over the top of the hatch in the manner described for wooden hatches.
Ladders and stairways may be of metal or of wood and are vertical or inclined. Inclined ladders should not extend athwartships in vessels for rough water service, unless this ar- rangement cannot be avoided. This is because of the danger of falling down them when the vessel is rolling. In passengers' living spaces stairways are usually built with a slope of 45 degrees and with good wide treads and ornamental railings. These some- times turn from two athwartship sec- tions to a "grand stairway" opening in the saloon. Curved stairways are not recommended for use on vessels, it being better to change the direc- tion of the stairs by introducing a landing.
All ladders are composed of two side pieces which are parallel and fastened at the top and bottom ends to the decks. Horizontal rungs or "risers" are fitted between the treads pieces and spaced about 9 inches apart in vertical direction. Sometimes "risers" are fitted between the treads to close the openings between them. Sloping ladders have hand rails of ornamental wood or of plain iron or brass pipe.
Fig. 83-a is a typical wooden slop- ing ladder of ash or oak. Angle iron clips are bolted to the sides and to the deck below as well as to the hatch coaming at the top of the ladder. A sheet brass covering is tacked over the door sill at the top of the ladder and the treads have a
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KIU. 82— WATERTIGHT HATCHES AND MANHOLES
protective covering of rubber, linoleum or of brass castings with lead or cement filling in grooves thereon. The front edges of the treads have sheet brass strips to reduce the wear. If risers are installed they are pro- tected by polished sheet brass "kick plates" neatly tacked on. The hand rail is fitted to cast or forged sockets on the outside of the side pieces. The treads should be at least 6 inches wide.
Engine Room Ladders Steel ladders may be similar in con- struction and are generally fitted in the engine rooms. The side strips are from 14 to f^ inch thick and at least 4 inches wide. The treads are cast iron with ribbed or roughened top and bolted to the sides by angle iron clips. "Subway" or similar gratings form an excellent tread for such lad- ders. No risers are fitted and the rails are always of metal.
Vertical wooden ladders have the same construction as that in Fig. 83-a
except that the risers are omitted. Sometimes a strip of canvas is lashed under open ladders to close the open- ings between treads, particularly in side ladders which lead from the deck to the water. Such ladders are sup- ported by forged arms from sockets on the side of the vessel and have wooden gratings at the top and bot- tom. They are arranged to hoist up by a block and tackle on a small davit and to be removed and stowed in the hold during the voyage. In- stead of a pipe rail a rope is led through forged stanchions around the gratings and down the sides of the ladder.
Vertical steel ladders to holds and compartments entered only at inter- vals, are composed of two flat bar strips with round or square bars for rungs. These rungs are riveted into the side bars. Sometimes the rungs are forged to a U shape with flattened ends which rivet to the bulkhead plating. Such rungs are at least 3
62
The Design and Construction of Poiver Work Boats
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FIC. 83— COXSTKUCTION DRTAILS OP LADDKHS A.ND HAILS
inches clear of the bulkhead. Again the bar rungs may rivet through two of the vertical bars which stiffen the bulkhead and also serve as sides for the ladder.
On a non-watertight steel bulkhead forming a chain locker partition or a swash bulkhead in a deep tank, semi- circular holes may be cut 12 inches apart horizontally and 9 inches ver- tically to form a ladder. These holes should be at least 4 inches wide to fit the foot of an average man.
Ladders are fitted on masts and in ventilators or trunks between decks to form emergency exits. Where a ladder without side rails or a vertical ladder has an open passage or a bulkhead at the top, grab rails should be fitted above the ladder (Fig. 83-b), or the rail should extend above the top of the ladder so that a person may stand erect when coming up or going down.
It is often necessary to hinge lad- ders at their tops in order to lift them
out of the way. Means should be provided for hooking the lower ends of such ladders to the deck above when hinged up. The width of lad- ders constantly used should not be less than 27 and preferably 30 inches. Ladders occasionally used may be as narrow as 10 or 12 inches.
Rope ladders with wooden rungs are called "Jacobs ladders" and are used for getting into small boats be- side the vessels.
Rails and Their Construction
Rails should be fitted around the edges of all decks, around all open- ings in the deck except at the point of access, at the margins of all cabin tops or house tops which are fre- quented by persons. Grab rods are fitted at the sides of trunk cabins, around the front of pilot houses, in passageways and at tops of ladders.
Open rails may be of metal or wood (Fig. 83-c to f). Closed rails or bulwarks of metal or wood are
sliown in Fig. 83-g to 1. Fig. 83-c is a rail of standard pipe (galvanized). It consists of 1^-inch stanchions spaced from 3 feet 6 inches t6 4 feet apart having standard flanges screwed to their lower ends. These flanges are screwed or bolted to the deck planks or plating. If such rails are fastened to the upper edge of a sheer strakc, it is necessary to weld the lower end of the pipe to a forged palm as in Fig. 83-d. The pipe rails arc from 2 feet 6 inches to 3 feet 6 inches above the deck, and there may be two or three of them. The top rail is usually from 1 to 1^-inch pipe screwed to the stanchions by a standard "T." Where the rail turns at right angles a sight outlet "L" or "T" may be fitted.
The intermediate rails may be the same size as the top rail and the stanchions, but are usually from J4 to 1 inch in diameter. Their connec- tions to the stanchions are by crosses. Side outlet "T's" are fitted at turns.
Forged or cast rail stanchions may replace those of ordinary pipe (Fig. 83-d), the sizes and connections being as shown. The rails in this case should also be of standard galvanized pipe. Sometimes the pipe rails are replaced by a single wire rope or "life line" passed through the forged stanchions. Occasionally in passenger vessels the upper rail is of wood on metal stanchions as shown.
Metal grab rails (Fig. 83-m) have small forged or cast stanchions screwed or bolted to the sides or top of deck houses. Wooden grab rails are shown in Fig. 83-o and p.
Wooden rails (Fig. 83-e and f) have plain or ornamental stanchions supporting a top rail and having metal clips screwed to the deck. The sides are of light planks or rope netting.
"Bulwarks" or rails solidly enclosed except for deck drainage openings, are fitted on tugs and the lower decks of cargo and passenger vessels. They tend to prevent waves from washing over the deck but are not desirable if heavy seas are encountered, since they trap the water and make it difficult for the vessel to free itself of seas which have been shipped.
Metal bulwarks have plating from 10.2 to 25 pounds (Fig. 83-g, h and k) which is riveted to the upper edge of the sheer strake. A rail of channel or bulb angle is riveted at the top of the bulwark plating and stanchions of forged round or structural steel sup- port both the bulwark and rail as shown. Wooden bulwark rails are fitted on passenger vessels and tugs. In the former case the rail is of 2 x 4-inch or 3 x 6-inch hardwood, bolted to an angle (Fig. 83-k), the bolt heads
Companions — Hatches — Rails — Awnings
63
being countersunk and the holes pkigged with wood. Tug rails arc of oak 4 X 8-inch to 4 x 16-inch.
The height of bulwarks in tugs is 18 to 24 inches above the deck. In passenger vessels the height corre- sponds to that of open rails.
Wooden bulwarks (Fig. 83-1 and n) have stanchions formed by ex- tending the upper ends of frames through the deck. The rails are of the same height as those on steel bulwarks. Small power tugs have low rails of a single log, tapered as shown and with a rail on top. "Scuppers" or drainage ports are cut at intervals in wooden bulwarks.
Azvring Stanchions and Fittings
Awnings of canvas are fitted over open deck spaces for shelter from the sun. They may be stretched over a pipe frame and lashed at the edges; or, in larger vessels, may have a wooden ride bar and spreaders (Fig. 84-a). The canvas is white or khaki colored and of No. 4 or No. 6 weight. Small boats have awnings rolling over a rounded pipe frame or of the "auto- mobile" top type which folds down.
Vessels operating in warm climates may have double awnings with an air space between and the edges of the canvas may overhang the ship's sides.
It is conventional to install a canvas "eyebrow" over the windows at the front of pilot houses (Fig. 84-b). This is painted green underneath but does not afford real protection from the glare of the sun which is re- flected upward from the water to the eyes of the helmsman. The eyebrow serves to keep rain oflf the pilot house windows to an extent but is not really needed.
Canvas "weather clothes" lashed to the rails at the front and sides of the bridge protect the occupants from the wind. They sometimes extend to the
FIG. 84— AVVNI.NG STANCHIONS AND FITTINGS
level of the eye (about 4 feet 9 inches above the deck). Awnings and weather clothes should
always be fitted on the bridge, even though not installed elsewhere on the vessel.
64
The Design and Construction of Power Work Boats
o c
CHAPTER XIV
Masts — Davits — Wmclies — Wmcllasses
XN MOST commercial power boats the sole use of masts and rigging is for cargo hoist- ing and for signaling either liy flags or by radio telegraphy, com- monly known as "wireless." Vessels rigged to carry sails and fitted with engines for propelling them in calms or to assist the sails in a light breeze, are not properly "power boats" and will not be considered in detail here. The rigging is complicated and caries con- siderably according to the method of fitting the sails. In general the sails are carried by from one tO' four masts in vessels which are "square rigged" and from one to seven masts on "fore and aft" or "schooner" rigged ves- sels.
The maats are named up to four and beginning at the forward one as "fore," "majn," "mjzzen" and "jig- ger" or "jury." So, if there are two masts, the forward one is the "fore- mast" and the after one the "main- mast." If there are three masts, the forward one is the "foremast," the center one or second one the "main- mast," and the third or after one is the "mizzenmast." The fourth mast or "jigger" is not common in square rigged ships and has its sails fore and aft as a rule.
Masts and Rigging
Masts are a single pole or in two lengths on modern vessels. If in two lengths, the lower piece is the lower ma'st and the upper section is the top mast. The point at which the topmaist is fastened to the mainmast is also that at which the strong athwantship guys or "shrouds" sup- port the mast. This point in all maists is the "hounds." It is also n-ecessary to fit longitudinal guys called "stays" to the masts. These are "backstays" if cm the after side of the mast, "forestays" if on the forward side and "springstays" if horizontal or nearly so between two masts. The stays and shnouds are fixed and have no blocks or tackle on them except means for tightening or I'oosen'ing; they are termed "stand- ing rigging." Ropes used for hoist- ing and lowering sails, spars or cargo
booms are fitted with block and tackle and known as "running rigging."
Since the wind pressure against the sails tends to bend the masts for- ward, they are inclined backward so the backstays will have a greater spread and the mast be subject to less strain. This backward imclina- tion is from -J^-inch to ^-inch per
foot oif height in common practice and is called a "rake." Pole masts in vessels without sails need not be raked except to conform with cus- tom which has affected judgment of appearances.
Most sailing vessels have a bow- sprit at the stem to afford great spread of the forestays and permit
Fia. 85— IlOW POLE MAST AND BOOM IS KITTKU
65
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7 iic Design and Constrnctiou nf Po7ver Work Boats
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carrying jilisails of larger area. Sonie- 'times the bowspri-t has an extensioin spar or jib boom at its outer end.
The "rig" of a vessel is named from the cut and position of its sails. Where these are rectangular and hung from a spar at their upper edge, the spar being fastened at its middle to the mast, the vessel is called' "square rigged." When Ihe forward verti- cal edge of the sail is attached to the mast, the vessel is "fore and aft rigged" or "schooner rigged."
Pole maisits as fitted to commercial power boats are similar in arrange- ment to !""ig. 85 and are usually ot wood in vessels up to ISO feet long, that is where the pole is of such height as to be obtained in a single length of the proper maximum diame- ter to withstand the stress due to the load'S. The cross section is circular
and is greatest at the point where the mast passes through the upper deck. Here strong wedgmg called the "part- ners" is fitted, the mast tapering up- ward to the hounds and downward to the foundation or "step." The re- dixtion in area at the hounds is about 18 per cent of that at the part- ners.
Steel mas'ts are not usuailly fitted in power boats, being confined to I'arge seagoing vessels. The mast may be a solid steel tube, a built-up tube stiffened inside with angle bars, a structural or built-up "H" section, or a latticed girder. (Fig. 86-a, b, c, d).
The lower end attach^ment of masts is known as the foundation or "step." It is usually fitted on the center keel- son as in Fig. (86-h-i and k), although sometimes where the hold is deep the masts extend to one of the lower
decks or the top of a shaft tumiel. In this case it is necessary to fit heavy stanchions under the deck sup- porting the mast or to .introduce a transverse bulkhead. The foundations must be braced athwartship by heavy knees in single bottomed vessels, but steel vessels with double bottoms require .merely a heavy doubling plate on the tank top at this point.
Wooden masts should be mortised into the foundation timbers. Steel ma'sts are riveted to the foundation girders .by angles as shown.
At the point where masts pierce the upper or main strength deck they must be rigidJy secured against de- flection by a structure call'ed the "partners." This conisists ol deck) beams forward and aft of the mast with connecting longitudinail carlings clo'se to the deck o.penin.g. There should be but one set of "partners," the spar being free to deflect be- tween t.his poiint, the hounds and the foundation. The decking is locally stren.gthened by miargin .planks in wooden vessels or .by doubling plates with an angle rinig or clips im steel vessels (Fig. 86-e-f and g).
Partners on weather decks must be made watertight at the wedges by fittin.g a canvas or metal hoo.d'. Struc- tural masts have stapled partner an- gles without wedgiing and calked watertiight. If the mast passes through a deck house top which is of light construction, the partners are on the next lower strength deck and a flexible canvas hood is tacked wiatertight air.ound the opening where the mast pierces the .light super- structure .deck.
Cargo Booms for W orkboats
The power workboats it is customary to fit cargo booms on. the mast .thus facilitating the loadin.g of heavy car- go. The bo'om is pivoted at its lower end to a point on the mast just above the partners as in Fig. 85. This .point is pivoted in two directions so the outer end O'f the boom can be either elevated' ("topped") or swung ho.rizon tally in transferrin.g the car- go fpom the wharf to the vessel's • deck. Two forged rings (a) are fitted tightly to 'the mast and a strong vertical pin (b) with an eye and shoulder at its Uip.per end is .passed through vertical bearings on the for- ward side of the mast rings. A nut or split pin is at the lower end of tlie large vertical pin. to prevent it from jumpiu'g out. A pronged forging is tightly fitted to the low^er end of the boom and engages the eye in the pin on the mast by means of a strong horizontal bolt or pin (c). The upper mast ring has an addition-
Masts— Davits — Winches — Windlasses
67
al eye (d) for atfachiiiig' the guide pul- ley (e).
The ib'O-om \s usually of wood al- thoaig'hi it may be a steel eyebeam or a latticed steel 'g-irder. At the free enid of the boom is a forged ring (f) with usually four eyelets. The I'ower of these eyes (g) receives the lifting tackle (usually inultiple effect). The uipp«r eye (h) secures the lower block ol tihe "toppinig lift" tackle which naises or lowers the boom. Swinging the 'boom from ship to dock is done by the "varags" which -attach to the eyelets on eaoh side of the end ring. The vamg on the side toward the dock is of fixed length so the iboom -with its load is free to swiii'g toward the wharf but cannot swing lOUitward' beyonid the hatch opening. When the vessel is under way the boo'm is lowered to a hori- zontal position and supported at its outer end by a "boom crutch" (Fig. 86-mi). This is a portable structure of forged bars or structural shapes with a semicincular depression, at the top into whi'ch the boom fits and is held by a cover piece hinged or bolted over. The lower ends of the crutch bolt to flush castings or angle clips on deck.
Davits
Davits are really small cranes and are employed for hoisting or lower- ing anchors, Mfeboats or companion ladders. Occasionally where light cargo is -handled a davit with block and falls is installed on deck at each side of the hatch instead of the cus- tomary mast and boom. Fig 87 (a) show:S a typical' davit made of a forgied round bar. The head is shaped at the sides as two eyes for attacb- mient of guys and stays while a hole is drilled vertically to take the eye b'olt 'from which the lifting gear is hung. A cleat is welded to the davit below the curve of the overhung arm for securing the hoisting line. Sometimes this cleat is served to the davit with wire. A support bearing is situated on the vertical shank just below the curve of outreach. This bearing -should be metalline or bronze bushed as -shown and is usually an independent forging o-r casting se- curely bolted to the deck house, cabin trunk or -bulwark rail, de-pend- in-g upon the locationi and utility of the davit.
If the davit passes througb a deck at the support bearing, a canvas hood is fitted above this bearing to prevent leakage. The lower end of the davit is rounded and rests on a hardened steel butto-n in a step bearing -casting. Some vessels with open bulwarks have the davits at the rail, making it necessary to fit a
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single casting which acts as a coin.- bined support and step bearing. (Fig. 87-ib).
Boat side l-adder an-di car-go- davits are as in Fig. 87 (a and b). Fig. S7-C is -an anchor davit.
Large vessels w-ith heavy bo-ats sometimes have rotary davits of struc- tural I-beams bent to shape. Special davits of the pivoted, link or quadrant types (Fig. 87-d to f) are also used in large vessels but will not be de- scribed in detail since they are too bulky and expensive for use in most smaller vessels.
Life boats should be carried by all power boats and should accommvo- date the maxim-um number of per- sons which the vessel is apt to carry.
The lifeboats for large vessels are usually of the double ended "whale- boat" type of w-ood or steel. They
have a rated carrying capacity of one person -for each 10 cubic feet of hull volume -and- have air-tight compart- ments at the ends and under the thwarts to afford safety against sinkage. The cockpit floor is above the water level and is water tight. Check o-r flap valves which -open out- ward are in drain pipes from the cockpit, so that water shipped over the side will quickly run off and lighten the boat. Oars with rowlocks for pulling and steering purposes are in the boat, als-o a "breaker" or sni-all cask of water and a tin of sea bis- cuit. A light lime with cork buoys is fitted through eyes all around the gun-wale and a portable rudder with tiller is provided.
The entire lifeboat is sto-wcd on wooden or light metal "boat chocks" or cradles and a davit is at each
68
The Design and Construction of Poxvcr Work Boats
end of the boat. The lifting tackle is shackled) to patent quick-releasing hooks at each end of the boat. These hooks will collapse and release the tackle when the boat is water borne or when a tripping device is operated by one of the o'ccupants. The outer boat chock is collapsible or hinges down so the boat will swing outboard with a minimum of hoisting and its at- tendant delay.
Ordinarily the boat is secured: in the chocks by laslhings fronn a 'carovas cover which stretches over a ridge bar and is fastened all around the gunwale. In tinies of danger when the boat may be needed quickly, it is Ewun.g out over the vessel's side and lashed to a spar fitted with heavy pads, which spreads between the davits. This spar is known as a "pudding boom."
A solid rrt'C'tal rod with shackles and turnbuckles, spans from the head of one davit to^ the other when the boat is stowed inboard. Wire rope guys with turnbuckles and thimbles are secured to the outside of each davit head and to pad eyes on the deck. The davits are thus held in posiition when not in use.
Lifeboats are carried on the house tops Oir trunk top in most power boats. When, the distance between the rail and the deck house is great, causing an excessive outreach of the davit arm by the usual method of boat stowage, skid beams are fitted over the passage at the house side and the boats stowed on a slatted platform over these beams. By this arranigement the davits can be at the vessel's siide and the boats dropped clear of the rail.
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Tvarge vessels should always have at least one lifeboat fitted with a gasoline engine. It may not -be pos- sible to accommodate all the passen- gers in boats but liferafts are then stacked on the deck house to make up tbe s'hortage. These rafts may be of pontoons w.ith slatted wooden pliatforms on top and underneath, with buoyed life lines, oars and row- locks. Modern types resemble large elliptical ring buoys and have rope nets ill the center.
Small power vessels use their life- boats for dinghies and such boats are either flat bottomed or dories. They are lashed bottom up on the cabin trunk and have lig'ht davits, or if light enough, are lifted over the side by hand.
In general, precaution s'hould be taken that wooden lifeboats are put into the water frequently so that the seams will not leak due to drying out of the planking. Metal lifeboats shoaild be kept well painted. Tackle and releasing gear 'sihould be fre- quently overhauled and kept free from paint. The crews of all boats should 1)6 schooled in rapidly manning, launiching and rowing the boats.
Winches for Hoisting Cargo
Winches are machines for hoisting cargo and are fitted at the base of masts or derrick posts close to hatc'hes. They may be hand, steam or electric driveni and oonsist of on€ or more dmums attached through mechanical gearing.
Fig. 88-a is a hand powered winch for small boats. The power is ap- plied by turning crank (a) which is keyed to shaft (b) and also car- ries the pinion (c). The spur gear (d) is keyed to the countershaft (e) which also 'Carries the pinion (f). The Shaft (h) has ispur wheel (g) driven by the pinion (f) and carries the druim (i) on -which the hoisting rope is wound. The entire mech- anism is supported by bearings in the pedestal castings (k) which are bolt- ed to the deck through a bed plate. Gypsy heads may be fitted on each end of the drum shaft (h) and are used for swinging the boom. If the winch is to be used for topping the boom an additional drum is necessary to take the lead from the topping lift. If the winch is of higher power, driven by gasoline, steam or electrici- ty, the principle is similar to this but the crank (a) is replaced by the crank pins of two horizontal steam cylinders, or a worm shaft driven by an electric motor or gasoline engine. .\ countershaft with clutch may drive
Masts — Davits — Winches — Windlasses
69
the winth from the main propelling engine. The winch is conti-olled by throttles or controller for regulating the applied power and has brakes for holding the drums. A clutch is fitted to the shafts of all drums if more than one is on the winch.
Capstans (Fig. 88-'b) are used for handling towlines at the towing titts or on the forecastle and- for warping the vessel. They consist of a drum with whelps driven through a ver- tical shaft by an engiine or motor usually below decks. They may be hand operated by inserting long wooden cap- stan bars into the sockets shown and having the crew push these bars when walking around the barrel. Small elec- tric capstans with motor inside the drum may be obtained and work very sat- isfactorily.
Windlasses are used solely for anchor liandling and warping the vessel. They are hand operated and fitted in co'mibination with mooring bitts on small vessels. Windlasses with independent motor or engine are used on large vessels. The loca- tion is near the bow close to the hawse pipes.
A typical windlass has a 'horizontal shaft sup'ported by bearings in ped- estal castings. Gypsy heads are us- uaMy keyed to the outer ends of this shaft and revolve with it. One or two "wildcats" are on the horizontal shaft inside of the pedestal bearings and a screw operated cone clutch thrown in or out by a wheel causes the wildcats to revolve with the hori- zontal shaft or to remain stationary w'bile the shaft turns. A brake on each wildcat holds it fast if desired. The main shaft is driven through a worm and worm wheel by a motor
or engine which may be close to the windlass on the same deck or, in large vessels, on the deck below.
Fig. 88 (c) and (d) is a diagram showing a typical windlass in rela- tion to the mooring or anchor gear. The anchor cliain is stared in a conv partment called the "chain locker" at the forward end of the vessel. The inner end of the dhain is securely .shackled to a ring or pad eye on the bottom of the chain locker. If there are two anchors it is neces- sary to fit a central bulkhead in the chain locker so the two chains will not become tangled. The chain leads up throiugfli a chain pipe which pierces the deck and has a removable wood- en or sheet steel cover fitting snugly around the chain to keep water out of the chain locker in wet weather.
The chain then passes around the wildcat, which is merely a large chain sheave with jaws fitting the links. The wildcat 'may be on a horizontal shaft as shown or it may be on a vertical shaft under a capstan. From the wildcat the chain passes to the upper end of the chain pipe in large vessels, or thro-ugh a chock on deck at each side of the bow in small vessels. A chain stopper is installed between the wiildcat and hawse pipe on large vessels, to pre- vent the chain frorn running out too rapidly. The chain is attached to a shackle on the upper end of the an- chor shank.
Anchor chain consists of links, the size of chain being designated by the diameter of the bar of which the link is composed. Figs. 88-(e) and (f) show "open link" and "stud link" chain, the two types univer- sally used. A shackle with its pin connection to the anchor is shown
by (Fig. 88-e). Sometimes provision is made for letting go the anchor chain in an emergency by a "pelican hook" (Fig. 88-g).
Hawse pipes are of cast iron or steel and consist O'f a deck ring cast- ing to which is rabbeted- the pipe itself. The deck ring vs extra heavy on the after side to- allow for wear by rubbing from the anchor chain. Doubling plates and closely spaced beams with carlings form a founda- tion under the deck ring casting. The li-olding down bolts are countersunk on the upper ends with gjro-m.mets and washers under the nuts.
The lower end of the chain pipe is bolted or riveted to the hull by an elliptical flange with rolled face and the frames are extra strong at this point. Usually one or more of the transverse frames are out to pass the hawse pipe, in which case short local stringers join the cut frame ends -to the adjacent intact frames. A doubling plate is fitted under the shell flange of the hawse pipe, to strengthen the hull and provide against wearing away when hoisting or lowering the anchor. All airports near the anchor should have heavy bars outside to protect the glass from breakage.
Hawse pipes are not usually fitted on vessels less than 125 feet long, in which case the anchor chain passes throuiglh a mooring chock (Fig. 89-f), I>assing th.rougih the bulwark or fore- castle side. If there is no bulwark, an open chock usually with a -roller on a bronze pin (Fig. 89-g) is used to hold the anchor chain in position. In small vessels the anchor is at- tached to a wire rope or manila hawser instead of to chain.
Photo copyright by Edw. CAJIOUFLAOKD 110-FOOT IIMTI-n ST.XTKS SUBM.VKINE CHASEIt Over 400 of these boaLs ucre built since June, 1017, mostly by yacht and tioat Ijuildeis in the United States — They penetrated every iiart of tlie war zone, and
made a wonderful record for sea^-orthiness and reliability
70
The Design and Construction of Power Work Boats
"IIAAKU.X" A southern Alaska canning; company's herring seiner and cannery tender
CHAPTER XV
Anchors — Bitts — Towing — Deck Drainage
'NCHORS are varied in type (Fig. 89-c-d-e) and are of cast or forged steel. Stocked anchors (Fig. 89-e) were orig- inally the prevalent design. They con- sist of a metal shank with two curved metal arms terminating in strong trian- gular flukes. The upper end of the shank has the usual shackle for attaching the anchor chain and just below this is a stock of wood or bar iron, turned at right angles to the plane of the arms. This type of anchor is still considerably employed in vessels without hawse pipes.
An anchor davit must be used to lift this anchor on deck by means of a block and falls which is hooked to the "catting shackle," located at the anchor's center of gravity on the shank. The anchor is lashed secure- ly to wooden chocks on deck when not in use. Sometimes a "billboard"' or sloping platform is built on each side of the deck close to the bow. The stocked anchor is then lashed in place on the billboard and arranged to launch itself wlien a tripping device is released by pulling a lanyard. With this arrangement the anchor chain may lead from the anchor down over the vessel's side to a hawse pipe, through which the chain re- turns up to the windlass on deck. This, however, is much less con- venient than using stockless anc h o r s as below described. Whenever a hawse pipe is fitted, and sometimes even in small vessels with- out this pipe, a stockless anchor (Fig. 89-A-C) is used. This is the mo.st prevalent of anchors at this writing. It consists of a forged shank with chain shackle at upper end, cat- ting shackle at point of balance and a pin at the lower end. The
flukes are shaped as shown with a swelled body connecting them and hinged about the pin. The flukes can open to 45 degrees on each side of the shank but are prevented from swinging beyond this by stop lugs on the fluke body. Stockless anchors are housed in the hawse pipe when not in use (Fig. 89- A).
Mushroom anchors (Fig. 89-D) are mostly used on small vessels and light- ships. While their holding powers are perhaps the most certain it is difficult to stow them in the larger sizes because of their bulk. Lightships have the hawse pipe through the stem at or near the water line and the anchor can conse- quently be housed securely without fouling the ship's side. A hole cut in the dished blade serves to take the hook on the catting tackle.
The size of all anchors is specified by stating their weight in pounds.
Bitts for Towing and Mooring
Bitts or "bollards" (Fig. 90-A to D) are mainly used for towing or for mooring large vessels. Towing bitts are usually of cast steel (Fig. 90-A) with two posts on opposite sides of the vessel's center line. Strong bolts through the base secure the bitt to a
TUG FOR GOVERNMENT WORK A type of boat in which towmg aiul deck equiiniient is given particular attentioi.
71
heavy foundation under the deck. If fitted on a steel deck the deck plates should be increased in thickness or have a doubling plate under all bitts. On wooden or concrete decks a pad of timbers from lj4 to 3 inches thick should be under the 'bitts. The metal posts are cored out to decrease the weight.
Sometimes in small vessels the tow- ing bitts are single or double hard wood posts with rounded corner edges. These wooden bits extend through the deck planking to the floors or keelsons and are through bolted to a heavy deck beam fitted against their after sides.
Large tugs may have a mainmast to which is secured a strong steel hook for towing. The hawser is looped over this hook and a hinged "keeper bar" is closed over the hook opening so the hawser cannot jump off the hook.
The towing bitts thus far discussed are located aft of the deck house or trunk and are used only when the towed vessels are astern of the one doing the pulling.
Three precautions should be taken : (a) Locate the bitts as far forward as practicable so that the vessel will not be difficult to steer if the tow "yaws" or swings to one side or the other.
(b) Make the deck under the towing bits extra strong.
(c) If the vessel does much towing in open water, have the bitts high enough above the deck so that the hawser may not bear too heavily on the rail at the stern, in which case following seas would come on deck.
Large deep sea tugs have a towing engine which auto- matically winds or pays out the hawser
72
The Dcsian and Conslnntion of Pozver Work Boats
keeping it at a constant tension. They also have a yoke or frame of struc- tural or cast steel which guides the hawser to the bitts or towing engine and keeps it raised above the stern rail. The towing hawser when not in use may be coiled on the ash grating over the rudder quadrant at the after end of the deck, or it may be reeled on
In harbors and fairly crowded wa- ters the barges are towed alongside of propeller-driven power boats and "side bitts" (Fig. 90-B and C) are fitted at about one quarter of the ves- sel's length from the bow and stern at each side of the deck. With a high bulwark rail the bitts are as in (Fig. 90-B), the rail timber being wid-
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spools under an overhang of the deck house top, thus being kept out of the weather. All power workboats should have towing bitts and hawsers for use in emergency.
On the western rivers of th? United States the towboats having stern paddle wheels push the barges which are se- curely lashed together and "stacked" against the wide forward deck. Two strong posts called "stack knees" (Fig. 90-E) brace the towboat bow against the nest of barges.
ened locally to embrace them. Flanges on the bitt casting provide for bolting securely to the rail, bulwark and deck. Sometimes the bitt has only one post instead of two as shown and the cast- ings are always cored out for light- ness.
With a low bulwark rail or an open pipe rail, ordinary mooring bitts (Fig. 90-C) may be used for towing. In small wooden power boats the side bitts may be hardwood posts through
the deck and securely bolted to the framing, clamps, etc.
A set of bitts are usually located on the deck center line near the bow, for riding at anchor or towing when backing away from the vessel being pulled. These bitts of steel or wood usually have the windlass secured to them in vessels up to about 130 feet long. Larger vessels have an inde- pendent windlass.
Niggerhcad on Tugboats
Finally the practice of extending the stem or apron up to form a "nigger head" (Fig. 90-D) is common in tug boats. This may be of steel bolted on top of the deck and extending above the rail, or of wood as shown on the sketch. The size of a bitt is indicated by the diameter of its posts.
"Cleats" or cavels (Fig. 91-A) are used for securing mooring lines on deck or for running lines and lanyards on spars in the rigging. They are of cast steel or cast iron and their size is stated as the length in inches from tip to tip of horns. When on deck they are located at the quarters just inside of the water way or the deck margin.
The lines lead from the cleats on the mooring bitts through "fairleaders" or "chocks" (Fig. 89-F and G) (Fig. 91-B and C). "Mooring ports" or "Bulwarks Chocks" are similar to Fig. 89-F, but usually lead straight through instead of at an angle as shown for this special one which is at the bow.
Open chocks (Fig. 91-B) are usually one forward and aft of each mooring bitt or cleat. Closed chocks (Fig. 91-C) are less frequently used due to the difficulty of passing lines through them. They were designed to prevent the line from jumping out.
Roller Chocks on Large Vessels
Roller chocks (Fig. 89-G) are mostly used in large vessels and have been previously described. They are apt not to function if care is not taken to keep the roller well oiled and the pin clean. Roller chocks are sometimes fitted on top of the rail aft and the towing hawser led through instead of being free to slide on the rail log from side to side. If the towing hawser rests on the wooden bulwark rail in towing, there should be two half round or half oval iron bars on top of the rail to pre- vent excessive wearing of the wood. These guard irons are fastened to the rail log with countersunk head screws.
Scupper Ports for Draining Decks
Decks and housetops exposed to the weather are provided with means for draining the rain or sea water by "scuppers" and "freeing ports."
Scuppers are openings in the deck
Anchors — Toiving — Deck Drainage
7Z
at the low points. They consist of a deck casting with a slotted bronze strainer and have a pipe leading down which carries off the water. Light su- perstructure decks and house tops have the scupper pipes discharge onto the lowest weather deck. The downcomer pipes are of copper or lead, from 1 to 2 inches in diameter and spaced at intervals of 6 or 8 feet around the edge of the deck. Deck house and
trunk tops have the pipes close to the house sides and turned outward at the bottom ends. Light upper decks with wide overhangs have the scupper pipes close to the stanchions supporting these decks at the vessel's sides.
The lower weather deck in small boats is drained directly through long shal- low ports cut into the log rail. If there is a ridge at the deck margin, caused by the deep margin planks, the
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FIG. 90— TOWLNG BITTS A.ND KNEES
FIG. 91— CHOCKS AND CLEATS
waterway thus formed is drained by scupper openings with strainers. Pipes lead from these openings down into the hold and out through the vessel's sides. The main deck scuppers in steel vessels are usually elliptical to fit between the waterway angles and still be large enough to carry off the water. The lower end of the scupper pipe at the ship's side has a casting with a pro- jecting lip and a flap valve to pre- vent sea water from coming on deck through the scuppers. If scupper pipes have right angle turns in them, there is a screwed plug at each corner for cleaning out purposes.
Freeing ports are large openings in high bulwarks to quickly free the deck of water which comes aboard through waves. The ports sometimes have a hinged flap opening out- ward, but modern practice is to just cut a large opening and stiffen the edges with a bar. A grill of iron rods is fitted over such open ports.
74
The Design and Construction of Power Work Boats
Typical "Handliner" Power Fishing Boat
Fleet of Seine Fish- ermen and Hand- liners at Boston Fish Pier.
Unloading a Catch at the Fish Pier.
Crew Opening Mus- sels and Baiting Trawls. There are 400 Hooks to Each Tub.
CHAPTER XVI
Tanks — Auxiliary Machinery — Quarters
CANKS may be used for carry- ing liquid cargo, fish, fuel, potable (drinking) water, lu- bricants, and to afford a stor- age hydrostatic head in gravity plumbing or heating systems.
Large steel vessels have parts of the hull especially constructed to form cargo, fuel and drinking water tanks. Such construction has been consid- ered in previous articles. Concrete vessels also have their tanks formed by the hull.
Wooden vessels are not used for liquid cargo to any extent. While large tanks have occasionally been built in such hulls by calking the wooden ceiling and bulkheads, the practice is not considered advisable because the water is acting on both sides of the hull structural surface so that deterioration is more rapid.
As a rule the tanks in wooden hulls are separate watertight steel compart- ments. These may have flat sides, properly formed to fit into the hull and re-enforced by stiffening plates, or else they may be cylindrical drums which are riveted or welded.
Built-in tanks have their sides, top and bottom re-enforced by angle stif- feners at two-foot intervals, while transverse and longitudinal swash dia- phragms spaced six to twelve feet apart, prevent excessive motion of the liquid contents. Swash plates have holes to permit flow of the liquid through them but not enough metal is cut away to prevent their reducing the "wash." The flat heads are flanged to the side plates and the plate edges should be planed before calking.
Heavy transverse foundation tim- bers or "cradles" support the tanks as indicated while chocks at the sides and ends prevent lateral motion. For painting or coating of tanks see Arti- cle XII.
Cylindrical tanks are composed of a rolled shell with a lap riveted longi- tudinal seam and "bumped" or "dished" heads. Some tanks are "seamless welded," meaning that they consist of two deep capsule shaped ends with a circumferential seam at the middle of the length. This seam
is welded and re-enforced by an ex- ternal butt strap, also welded on. The dished heads have a spherical form and may be welded or lap riveted to the cylinder shell.
All tanks should have filling pipes, drain pipes, gage pipes, vent pipes and manholes or hand holes.
Vent pipes should lead to the out- side air in petroleum tanks and should have a return bend at their upper end, fitted with a wire mesh screen. Natur- ally the vent should connect to the highest point in the tank.
Filling pipes may lead to screw plates in the deck arranged to re- ceive the contents of the tank through a hose or a large funnel with strainer. If such a pipe is too long there is danger of its breakage through un- equal expansion and vibrations of the hull and tank top. Therefore, the fill- ing pipe sometimes ends just below the deck plug and has an independent cap. Such a filling connection may serve as a vent for water tanks if small holes are drilled just below the cap. ;
Gage connections vary according to type of measuring instrument used and are sometimes dispensed with if the contents are measured through the filling pipe by means of a calibrated sounding rod. In this case a small re-enforcing plate should protect the tank bottom where the rod strikes. The kind of gages depend upon size of tank and accuracy of measurement desired. Gage columns of the simple tubular glass type are subject to danger of breakage and should be
protected by vertical rods or a ver- tically slotted metal pipe around the glass columns. Reflex gages consist cf heavy plate glass in a metal frame. The front glass has vertical "V" grooves in it and causes the liquid to appear dark as it rises between the two glass plates. Float gages have a twisted metal ribbon extending from a horizontal dial in the tank top to the bottom of the tank. The upper end of the ribbon strip has a needle attached. A small cork or hollow metal float slides up or down the ribbon as the level of liquid varies, but the float is prevented from turn- ing by vertical guide rods. As a re- sult the ribbon turns the pointer as the float rises or falls. Pneumerica- tors are frequently use^ in large tanks and afford the advantage of having the tank contents observed at some remote point.
Drainage connections are for suc- tion pipes to the point at which the tank contents are utilized or dis- charged. Sometimes a screw plug is fitted to a flange at the lowest point so that the tank may be entirely emptied and dried out.
Sediment chambers may be fitted to fuel tank discharge lines to catch and retain impurities or foreign mat- ter. The suction is at a point near the top of such chambers and a clean out plug is at the bottom. This pre- caution is not considered necessary if the fuel is strained through fine copper screen as the tank is fitted.
All pipe lines should have offsets or bends to permit of expansion without
FIfi. 02— KUi;i. oil WATKI! TANKS, FLAT SIDE TYPE
/:>
7(y
The Design and Construtiou of Pozvcr Work Boats
Vcni Pi/ic
Cvt/NDPICflL fVEL T/INKS
Iti fMGiME Room Wings
ruH Pipe
( ^ yCever Plate
DCTMIL /IT /I OCl/IRO STRIPS WHCflE FUEL SUPPtV P/PE TO EN&IHE CWOSSES FLOOR
'vel FromT^nk
fuel Line ' To Enyt'n*
Screu/ed ' OfCK Plate
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3EDIMEMT CH/IMDEff
DETAIL C Deck C/isting & Filling Pipe
FIG. 93— INSTALLATION AND EQUIPMENT OF FUEL TANKS
Straining or breaking the pipes and connections. Valves and pipes should be within access at all times and clearance around the outside of tanks should be sufficient to permit of clean- ing and painting the tanks and sur- rounding hull structure. No pipes should be threaded to the tank plat- ing but riveted flanges of cast steel or heavy plating should take the screwed connections.
Auxiliary machinery for hoisting purposes has been discussed in a previous article. That for pumping, lighting and miscellaneous purposes is located in the engine room if possible and is usually a part of the engine.
Electric Generaling Sets
Electric generating sets vary from one-half to five kilowatts capacity and are driven by independent internal combination engines or by a silent chain or belt from the main engines. Independent sets of standard com- mercial makes are preferable, since they do not require running the main engine if light is desired when the
Ca.r\vas Pachtnf tn White Letd
MM y»ii»!
Hvll Pianktnf
OCTAIL OF IHLET CONNECTION
FOR Pipe Suctions Fho/i 5Ef\
vessel is not under way. The ca- pacity of the set varies with the num- ber of lights on the vessel. A stor- age battery is usually "floated in the line" from the generator, so that it becomes automatically charged and may afford current when the genera- tor is idle. A switchboard of slate or other nonconducting material is fitted near the generator and has the usual volt meters, ammeters, rheostat, switches, fuses, ground lights, auto- matic cutouts, etc. The various cir- cuits should be arranged to lead direct from the switchboard and to be inde- pendent. This is particularly im- portant in the case of the running lights and the searchlight. A "tell- tale" should be in the pilot house so the helmsman can see that the run- ning lights are in order. All running lights if fitted for electric equipment should have duplicate oil lamps which are used in case of emergency.
The number and location of run- ning lights are regulated by the Bu- reau of Navigation, Department of Commerce, Washington, D. C. They vary with the size and type of vessel.
Searchlights may be of the arc or the incandescent filament type. The latter are considered ample for the average small work boat, since their power consumption is less and they are not expensive or complicated.
Lights in the living quarters should be tasteful and ornamental. Frosted globes add to their attractiveness and soften their glare.
Lights in machinery spaces, pas- sages, holds and on deck are in vapor tight fixtures ard should be guarded by wire. In the engine room, cargo holds and tank spaces, plugs should be fitted so that portable hand lights
may be connected when needed. The cable for these lamps should be suf- ficiently long to insure being able to see any point which may require ex- amination or repairs.
If there is electric power at the docks where the vessel ties up, and the voltage of the ship's circuit agrees with that on shore, it is well to fit plugs outside the deckhouse so that current may be taken from the dock lines if the boat is tied up for ex- tended periods.
The wiring on decks and elsewhere except in the living quarters should be in metal conduit, with standard metal junction boxes. Wood molding may be used in the living spaces.
Pumps and Drainage
Piping for the "Pumping and Drain- age Systems" has the following uses:
(a) Draining the bilges,
(b) Filling and emptying water tanks,
(c) Providing pressure to plumbing fixtures, fire lines, wash deck connec- tions, etc.
The main engines are usually fitted with two water pumps of the plunger or the centrifugal type, driven from the crankshaft or the camshaft. One of these pumps circulates the water for cooling the engine cylinders. It draws its supply from overboard through a sea connection on the hull, near the turn of bilge. Be careful that this location will provide against danger of stopping up due to the ves- sel's grounding and that it will always remain below the water. A strainer covers the pipe opening to prevent solids from entering and clogging the pipe line to the circulating pump. A valve in the suction pipe, close to the sea connection, provides for closing off the sea water in case of damage to the pipe line, or if the pump is to be used for draining the bilges.
The cooling water passes from the circulating pump to the cylinder jack- ets and discharges overboard at or near the water line. Frequently the cooling water discharge pipe is tapped into the exhaust pipe from the mam engine.
The suction pipe to the circulating water pump may be arranged to draw from the bilges by connecting to the bilge manifold. This gives the boat additional pumping facilities in case of emergency, when the sea injection valve may be closed and the bilge water discharged through the cylinder jackets of the main engine.
The second pump above mentioned is not fitted to all engines particu- larly in the smaller sizes. It serves as a bilge pump, drawing directly
Tanks — Auxiliary Machinery — Quarters
77
from the bilge suction pipe lines and discharging overboard. It may also be piped to the sea connection which admits water to the circulating pump, and thus used to provide sea water on deck for washing down or fire pur- poses.
Power tugs from about fifty feet upwards in length usually have an auxiliary gasoline engine which drives a generator and sometimes an air compressor and water pump as well. This pump is piped to the bilges, the fire and deck service and the sanitary service, through a manifold in the en- gine room.
A hand-operated bilge pump should be fitted on all power boats.
The sanitary system is piped to flush closets, urinals, for water supply to baths, wash bowls and even for cooking purposes, on boats operating
tuiaUc o/ Hull
DETAIL OF SOIL PIPE DiSCHnROE CONNECTION
Noie: Drain fiit>^i end Scupper Ouil'is jrein levels w<it mbaue wnier Jine hM4 not i^ fitted withfltp vtlve.
in fresh water. Salt water vessels use sea water for flushing and bathing only, fresh water being taken from the tanks for cooking and potable purposes.
Pressure is provided through an overhead gravity tank which may be on top of the deck house or the cabin trunk. Connections to the sanitary supply tank are a filling pipe, a dis- charge line, an overflow, a vent pipe and a drain plug. It is essential that the tank be protected against freezing. Boats with a ventilating stack may have the tank in this.
Mention has been made of pipe con- nections on deck for washing down and fire uses. Brass capped plugs at the sides of deck houses, with hose racks on the bulkheads nearby, should be on boats from about 75 feet long upward. Vessels smaller than this have fire buckets in racks on deck and chemical fire extinguishers, lo- cated where readily reached in case of fire.
Fire Losses Are Preventable
The majority of fire losses in power boats are preventable by proper de-
sign and the observance of due pre- caution when in service. Most fires are due to one of the following:
(a) Improper ventilation of the fuel tank and engine room.
(b) Leaks in the fuel pipes and fittings because no allowance is made for vibration and expansion, or the pipes and fittings are inaccessible for repair.
(c) Collection of grease, oil and in- flammable gases in the bilges, with no provision for their removal or drain- age.
The first of these causes will be taken up under ventilation; the second has been discussed under fuel piping and the third may be avoided as fol- lows. Fit a sheet metal drip pan under all fuel and oil tanks and under the engines. This pan may be of black or galvanized iron or copper, and of width and depth to catch and retain all drip from the machine under which installed. A slight drainage slope should be given the bottom of the pan and there should be a large well or "sump" at the low end, from which the drippings may be pumped, bailed or swabbed.
All water piping may be galvanized wrought iron with malleable screwed fittings. Valves should have compo- sition seats.
Air pumps, supplying pressure for starting the main engines, blowing the whistle, affording a head in the water or fuel tanks when these are low down in the hull, are sometimes driven from the main engine or by the auxiliarj' gasoline set.
Power boats in northern waters should have some form of heating system. When less than 50 feet long small oil flame heaters, securely fast- ened to the deck may be in each compartment to be heated. The deck and bulkheads near all heaters should be protected against the heat by a sheet of asbestos board covered with sheet metal.
Larger boats have central heating plants of the hot water or steam type, with piping to the radiators in heated spaces. Such heaters may burn coal or oil and should be in the engine room or the galley. A small galvan- ized or black iron smoke pipe carries the heater gases to the stack, when such is fitted. Otherwise the smoke pipe projects above the cabin or trunk and has a metal cap or hood to ex- clude rain water. Sometimes this hood turns with the wind thus in- creasing the draft by ejection effect.
There should be about one square foot of heating surface in the radia- tors to each fifty or seventy cubic feet of space to be heated.
Hot water systems require an ex- pansion tank located in the top of the engine room or the stack. This tank has an overflow connection to the deck outside and is piped to the radi- ators and to the cool water inlet of the heater. The heater should be be- low the level of the radiators if pos- sible, so that the hot water leaves the top of the heater, flows upward through the radiators to the expansion tank and then down to the heater again.
A coal bin or fuel tank is located close to the heater.
The heater is provided with the fol- lowing fittings:
Thermometer,
Pressure gage.
Water gage,
Safety blow valve.
Damper,
Drain plug.
Air relief valves should be on all
Stfniner
^ Sheet fieUL
Scretved . Flanged
DET/\\L OF
scupper from tiled Toilet sppiCe ,
radiators and the entire system should be carefully drained through cocks at the low points, in case the vessel is laid up during freezing weather.
Steam heating systems are similar in arrangement and fittings except that tlie expansion tank is lacking.
In large vessels, thermostatic con- trols may be fitted in the heated com- partments to automatically regulate the temperature.
Radiators vary from ordinary pipe on brackets, to cast iron, pressed steel or brass ones of the upright or the wall type. Pilot house radiators and piping within ten feet of the compass should be brass, because of the effect of iron or steel on the magnetic needle.
Insulating pipe covering should be on all heater pipes, on the exhaust pipes from machinery and on all hot pipes where extreme temperature will endanger personal safety or result in loss in efficiency.
Tubular boilers on large diesel en- gined vessels sometimes derive their heat from the exhaust gases of the main engines, generating steam for auxiliary engines and for heating.
78
The Design and Construetion of Power Work Boats
Oure.7
/l,/e P/iiiM£
FIG. 95— Bl ILT-IN UKFIilCKIlATOIi IN (AniN TKUNK OF 50 TO Tu-FOOT I'OVVEU BOAT
Vessels of this type use electrical pumps, winches and other auxiliaries, the current being supplied by a gen- erator driven by a diesel engine.
Plumbing Fixtures
Plumbing fixtures are too often not installed where their presence would introduce low additional cost while affording real comfort and sanitary surroundings. This applies to nearly all power workboats, which should at least have a self-flushing water closet and lavatories with running water.
If the crew is quartered on board it is imperative that bathing and gal- ley plumbing fixtures be fitted; for a clean and well fed crew means a neat and well kept ship.
Water closet bowls should always be located in a well lighted and ven- tilated space, partitioned off from the rest of the living quarters by odor tight bulkheads. There should be at least one bowl for every twelve or fifteen persons. The discharge or "soil" pipe should be large (at least three inches in diameter). Too much emphasis cannot be laid on this point, for clogged bowls are a cause of dis- satisfaction and disgust. The flushing water should be taken from the sea and the bowls located above the load water line if practicable. This will eliminate the necessity for pump type closets if the boat has a sanitary pres- sure system. Bowls if below the water line, should always be of the pump type.
Urinals are fitted in larger vessels and should be of a type readily cleaned, not subject to clogging.
All sanitary fixtures should be as
close to the ship's side and to the source of water supply as practicable. Lavatory and toilet spaces should be easily entered without undue disturb- ance of the privacy of living quarters.
Water supply pipes may be galvan- ized wrought iron, with valves having bronze stems and seats. Discharge or "soil" pipes may be wrought iron or lead, terminating in cast iron flap valves at or near the water line on the hull. If the pipes have bends (which should be avoided) there should be a clean-out plug at each turn in the pipeline.
The deck in toilet spaces should never be of wood or other material which tends to absorb moisture and odors. Tiling in cement or plain ce- ment are best suited for such decking. Wooden decks should be protected against the likelihood of moisture getting under the deck covering, by having a watertight sheet lead, zinc or galvanized iron pan fitted tightly all around the compartment and ex- tending at least up onto the bulk- heads. This "flashed" metal should extend at least six inches above the top of the tile or cement. Plain ce- ment decks in toilet spaces should have portable gratings of oak or ash.
The corners of all toilet space decks should be generously rounded (coved) and drainage provided at the low cor- ners by scupper openings having per- forated brass strainers. Pipes dis- charge from these scuppers into the soil pipes or the deck scupper pipes.
Where bathtubs or showers are fitted, these should be located apart from the toilet spaces and should have running hot or cold water. The sup-
ply for these is usually from the sea, but on salt water ships fresh water is from the ships' tanks and salt water 1.; provided as well.
Lavatories and sinks in galleys or pantries should have spring faucets to minimize waste of water. They dis- charge into the soil pipes and some- times into the bilge.
All toilet fixtures above mentioned should be of porcelain enameled iron, with nickeled brass fittings so they can be kept clean and sanitary.
Hand pumps of brass or with brass linings, are fitted to galley sinks from the fresh water supply system.
In sone harbors the discharge of waste from plumbing fi.xtures is pro- hibitive and vessels navigating such waters require a large tank in the hold. The waste matter from these tanks is forced overboard by com- pressed air, steam, or a pump for that purpose, after the vessel has got away from the prohibitive waters.
Messing Equipment
Messing equipment is that devoted to feeding the crew, including the storage of unprepared food in store- rooms and refrigerators; the prepara- tion of the food in the galley and the serving of the food.
Canned food supplies or those such as rice, beans, flour, sugar, etc., which keep relatively long without refrigera- tion, are termed "drystores." Lockers or storerooms with shelves and bins for such stores may be located in the hold and should be dry and well ven- tilated.
Vegetables should be placed in grilled boxes or bins, in the open air if possible but with covered tops. Such vegetable lockers may be located on top of the cabin or trunk to which they are securely fastened. They con- sist of oak or pine slats with a rain- proof hinged top. Vegetable lockers of strong wire mesh are desirable in larger vessels.
Small bins or jars in the galley should be fitted to provide an imme- diate supply for cooking.
Perishable supplies such as fruit, eggs and other dairy products, meats, etc., are carried in refrigerators. These should be easily reached from the galley and may be either built into the ship or of standard commercial type strongly secured in place.
Refrigerator capacities average from 2..S to 3 cubic feet of volume for each person for which cold stores are pro- vided.
CHAPTER XVII
Food Storage, Heating and Lighting
'MALL refrigerators in vessels shorter than 100 feet, are usu- ally cooled by ice carried in a compartment within them- selves. Larger ones are cooled by re- frigerating machines, using ammonia, carbon dioxide, sulphur dioxide, ethyl chloride or dense air as the cooling medium. The smallest of such ma- chines have a capacity of one-quarter ton of ice per day. They are driven by electric or internal combustion mo- tors.
The outside refrigerator walls are of steel or wood, usually tongue and grooved, from % inch to 1% inch thick. The inside of these bulkheads has a layer of tarpaper or building paper. A layer of insulating material is inside the paper and is from four to eight inches thick. The best of such materials is pure block cork, usually fitted in two layers with the seams staggered. Sometimes a sec- ond layer of thick paper is between the two thicknesses of cork, while a final paper coat is always inside the insulating material. Ground pressed cork, mineral wool or even air cells are often used to form the refrigera- tor walls but these are not recom- mended. The insulation should be packed tightly and fastened by ce- ment, «o< by nails or other metal fasten- ings which conduct heat. The inside refrigerator walls are of sheet zinc, porcelain enameled iron, glass, or wood soldered or cemented in place.
In designing refrigerators remember that cold air from the ice or the cool- ing coils always settles to the bottom and replaces warmer layers. There- fore, the ice or coils should be at the top of the box to insure circulation. The air in refrigerators should be kept as dry as possible.
If ice is used it is placed in the upper part of the refrigerator on a metal shelf which has pipe drains to the bilges. Air spaces above and at the sides of the ice provide cooling circulation.
Refrigerator doors are double rab- beted with rubber gaskets. Small boats may have refrigerator boxes opening on top located in the holds or under locker seats. A convenient
arrangement where there is a separate galley, is to have the refrigerator in one corner with its top just below the windows of the cabin or trunk. The ice and cold stores may be passed through a window directly into such a box. Still larger vessels with galley on the main deck may have a door in the deck house at the refrigerator. Both these arrangements prevent the soiling of interior of the cabin or trunk when stocking up the ice box.
Dryslorcs
Canned food supplies or those such as rice, beans, flour, sugar, etc., which keep relatively long without refrigera- tion, are termed "drystores." Lockers or storerooms with shelves and bins for such stores may be located in the
iftj-reiv J^AeT/f/^tiS -
seCT/OH TH/?U FffAMS of
FIG. 00— CONSTRUCTION OF KEFKIGERATOR DOOR
hold and should be dry and well ven- tilated.
Vegetables should be placed in grilled boxes or bins, in the open air if possible but with covered tops. Such vegetable lockers may be located on top of the cabin or trunk to which they are securely fastened. They con- sist of oak or pine slats with a rain proof hinged top. Vegetable lockers of strong wire mesh are desirable in larger vessels.
Small bins or jars in the galley should be fitted to provide an imme- diate supply for cooking.
Galley ranges vary from small blue flame kerosene stoves with one or two burners to large ranges burning oil or coal. The small stoves may be in a drawer lined with sheet metal so that the stove is out of the way when not in use. A small fuel tank is usually fitted to such kerosene stoves and sometimes there is a small hand operated air pump to generate pressure in the tank.
Oil burning ranges use fuel oil of
heavy gravity and are used only in vessels with diesel engines or in large vessels. The burner atomizes the fuel by air, steam or mechanical means.
Coal ranges are usually fitted in ves- sels above 100 feet long. There is a fuel locker close to such ranges and they have a tank attached for heating water. This may be piped to the hot water sanitary system if desired.
All ranges are securely fastened in place by screws, angle lugs, or stay rods. There is a nickeled guard rail on top of the ranges to prevent pots and pans from sliding off.
The deck and bulkheads near ranges are protected against the heat by sheet asbestos covered with galvan- ized iron.
A stack over the ranges carries off gases and odors.
Dressers for Food
Beside the ranges, sink and plumb- ing thus far mentioned, galleys have dressers for preparing the raw food for cooking. This dresser may serve as a mess table with hinged stools attached or arranged to stow under- neath. Lockers and drawers under the dresser and the sink afford stow- age for cooking utensils. Racks and shelves on the bulkheads are provided for the dishes. These shelves have covered fronts with a Y-shaped slot in them so that dishes are put in at the top and cannot slide out when on tlie shelf. Cups and other china dishes with handles are hung from hooks underneath the shelving.
The decking of galleys in small boats may be linoleum, while in larger ones it is usually tile.
When meals are not served in the galley there may be a saloon, although this is not common in workboats.
Berthing accommodations are not needed in boats which have short runs but it is well to provide sleeping facil- ities for emergency use. To this end hinged bunks of galvanized pipe may be installed in the forehold or even in the wings of the engine room. The berths may have lashed canvas or spring bottoms and mattresses. Bed- ding is stored in lockers nearby.
Sometimes cushioned seats or "tran-
ro
80
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piQ, 97— INTERIOR OF STACK WITH TANKS
soms" are arranged to slide out form- ing berths when extended. The cush- ions are designed to fit the extended transom and serve as mauresses. Cushions are filled with hair or buoy- ant fibre such as kapok. They may be covered with leather, imitation leather or velvet. The imitation leather is recommended as being durable and best for ordinary workboats.
Lockers, drawers and shelving should be provided wherever possible by utilizing unoccupied corners or spaces under berths and seats.
Means of Ventilation The usual means for ventilation are: (a) Cowl ventilators, (6) mushroom ventilators, (c) wind chutes, (d) vent pipes or "goosenecks," (e) skylights and hatches.
Cowl ventilators may be fixed or portable and are arranged to be turned 'into the wind" by shafting and gears
^^n// VENTILATOR
The Design and Construction of Power Work Boats
operated from below or by handles on the cowl itself. They are of sheet iron, galvanized or painted. Small cowls on yachts are sometimes of pol- ished brass. The cowl is mounted on a fixed trunk fastened to the deck by an angle ring. This trunk may extend to any desired distance below the deck and the part below the deck ring may be circular or rectangular. Sometimes it is necessary to offset the trunk be- low decks so it will not prove an ob- struction. The cowl opening is usu- ally twice the diameter of the ventila- tor trunk and the upper edge projects slightly beyond the bottom of the opening. The metal forming the cowl is bumped and welded or riveted to shape. A split pipe or half round bar re-enforces the edges of the cowl opening.
Mushroom J'cntilators
Mushroom ventilators are not "wind catchers" as is the case with the cowl type. They are merely "up comers," meaning that they release impure air but do not admit a fresh supply. They consist of a short pipe fastened to the deck with an angle ring. A screw down cap covers the top of this pipe and seats on a watertight rubber gasket or a ground joint. A central rod with acme or square screw threads ill a guide is turned from below by a handwheel or crank, thus raising or lowering the cap. The cap projects over and down around the outside of the pipe, so the vent may be opened slightly in rainy weather. Mushroom vents may be of cast steel or bronze. They are usually fitted over toilet spaces or living quarters where mild circulation of the air is preferable to
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FIG. 98— VENTILATING F,QUIPMENT
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11 G. 99— VENTILATING EQUIPMENT
the direct draft afforded by the cowl type.
Types of IVindchutcs
Windchutes are of two types; the canvas ones for ventilating holds and other spaces not requiring permanent vents, and the "airport type" which may be used in living quarters.
Canvas windchutes arc used in cargo vessels and are simply a long canvas trunk which has an opening near the top. Wing flaps at the sides of the opening help catch the air and force it down through the trunk. The en- lire canvas windchute is suspended from the mast or rigging by its hooded top and the lower end passes through a hatch into the compartment which is being aired out.
Airport windchutes are of galvan- ized sheet iron, scoop shaped and de- signed to be pushed through open airports so that air will be deflected laterally into the compartments of the hull. They sometimes have screens at their inner ends.
Ventilators of various types are sold by ship chandlers in stock sizes.
Vent pipes or "goosenecks" are placed over tank spaces and consist of standard pipe extending above the deck with a return bend at the top. A standard pipe flange connects the lower end of the pipe to the deck.
Forced ventilation is employed on large vessels but not in the conven- lional power workboat. Such a sys- tem has a central blower plant taking air from vent cowls and forcing it to remote spaces in the hull through sheet metal ducts or conduits.
.'\ few of the cardinal principles of ventilation might well be discussed and should be borne in mind when designing power workboats.
First: Warm and impure air Is ligliter than cool fresh air. Therefore, the supply ventilator trunks should lead well down into the ventilated compartment, while exhaust vents open from the highest points therein. Skylights form good exhaust but poor supply ventilators.
Second: The motion of air currents
L
Food Storage, Heating and Lighting
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FIG. 100— PIPE AND TRANSOM BERTHS
inside the hull is from aft forward so that supply vents should be at the after end of compartments and ex- haust vents at the forward ends.
Third: A mild air current well dis- tributed is more effective than a
strong current which is local. Do not Fourth: Gasoline fumes are heavier
forget the corners of compartments than air and tend to accumulate in
and see that the circulation is diag- the bilges. Arrange for circulation
onally upward by staggering the sup- low down in engine or fuel tank
ply and exhaust vents about the com- spaces by using an open rather than
partment's centerline. a ceiled type of structure.
82
The Desifin and Construction of Poivcr Work Boats
jMary p. m:rn, power fishing sciioonkr
Owned by Cspe Aim Cold Storage Co. Equipped with 80-horsepower Wolverine engine.
Under command of Capt. Patrick Murphy . This has been
one of the most successful craft in New England waters
CHAPTER XVIII
Painting Structure and Sheathing
^1
•EASURES must be taken to protect a boat's structure against the various elements tending to cause deterioration. Wood will decay or be attacked by marine growth and animals. Steel will corrode, decompose by electrolic action or become fouled with marine growth. First consider briefly the causes and prevention of decomposition in wood. Decay is brought about by micro- scopic plants called "molds" or "fungi." These tiny organisims grow in the wood fiber as parasites, and their growth is aided by oxygen, water, heat and food, just as in the case of other plants. If wood is kept absolutely dry or constantly sub- merged in water, it will not decay. If the wood is in a moist atmosphere at ordinary temperatures, it will decay rapidly. If moisture is held in the wood and cannot escape (as when green timber is painted) decay will set in. Sapwood decays more rapidly than that from the heart.
Different Forms of Decay
Different forms of decay are "dry rot", "wet rot", "sap rot", "brown rot", and "blue stain". The latter is not seriously detrimental to strength of the timber and occurs in the sap- wood of pine or other evergreens. Such timber is treated by dipping into a solution of 5 per cent solution of carbonate of soda heated between 130 and ISO degrees Fahr.
Decay which exists in the heart- wood of living trees, ceases when the tree is cut and does not spread to other sound pieces of wood nearby.
Softwoods which are exposed to the weather wear away. This is known as "weathering."
Where the Teredo Works
There are small marine animals of various kinds in the salt waters of warm climates which attack wood by boring. The teredo worm is best known of these. It has a hard horny head, a long body and a feathery tail of gills. When it has penetrated the surface of a timber, the teredo works along the grain and does not cross seams which have been tarred or calked. Fresh water kills the teredo
worm and vessels are sometimes taken into rivers to eliminate the pest. When properly sheathed with metal, hulls are not attacked by the teredo or that other insect, the wood louse (limnoria). The teredo is not found in cooler salt waters (temperatures below SS degrees), nor in brackish waters.
The wood louse is found along the coasts of New England, the Gulf of Mexico and the northern Pacific states. It lives only in pure salt water. Dirty water will kill it.
How to Prevent Decay
Prevention of decay in timber has its initial step in seasoning or drying out the moisture from the green wood. Green wood contains from half to three-quarters of its total weight in water. Seasoned wood (air dried) has from 10 to 20 per cent of its dry weight in contained water. This re- duction of moisture content lessens the tendency for fungi to grow and assures a minimum of shrinkage and warp after becoming part of the vessel's structure.
Timbers being air dried have a tendency to split or "check." This is minimized by painting or creosoting the ends of the logs, or else by driv- ing "S" shaped wedges about J^-inch thick at the base onto the log ends. Small timbers are sometimes put into a concentrated salt solution where they remain from a day to a week to prevent their checking while season- ing. They may be dried in bone char- coal which also prevents checking.
Kiln drying is usually done in a large heated and ventilated building through which the lumber passes in successive steps. It comes in at one end as green wood and leaves at the other end of the building in seasoned condition. Soft woods can be dried more rapidly and at higher tempera- tures than hard woods, without loss of strength.
Seasoned timber after incorporation in the hull structure is protected by saturating with various compounds to exclude moisture and decay or by coating with elastic waterproof pig- ments. The saturating process is little used in boat building, the preservative
83
chemicals mostly employed being "creosote", chloride of mercury and chloride of zinc.
Creosote is Best Preservative
Creosote (creosote oil or dead oil of coal tar) is the best of these preserva- tives. Owing to its penetrating odor it is only used on vessels where the cargo (if subject to taint) and the living quarters are remote from the treated timbers. Vessels such as shal- low draft lighters or self-propelled barges, which do not carry cargo in the holds, may be creosoted. The wood should be cut and trimmed to fit before being treated. It is then creosoted.
Creosote is a by-product from the manufacture of coke or illuminating gas. It is the residuum of tar after the light oils have distilled off. Its chemical composition is very involved. It varies in weight as purchased and the heavier grades are the best. The timber to be treated has the coal tar creosote forced into its wood cells under pressure.
A number of compounds with trade names such as "carbolineum" are ap- plied with the brush as substitutes for creosote.
The seasoned and cut timber is placed in a heated chamber wherein a partial vacuum is then created. This expells moisture from the ducts and cells in the wood and the creosote oil is forced in to replace it. There are various methods for performing the processing, some more economical as regards use of the fluid or less apt to break down the structure of the wood contributing to strength, than others.
Surface Preservatives
Surface preservative coatings for wood are divided into (a) fillers, (b) paints, (c) varnishes.
Fillers are used to close the pores of woods which are to be given a high polish. As such polished finishes do not find general application except for furniture, models, musical instru- ments, etc., they will not be dis- cussed here.
Paints for wooden surfaces contain a basic pigment of lead or zinc, mixed with an oil, a thinner and a dryer.
84
The Design and Construction of Power Work Boats
FIO. 101-BILGK KEELS AND SHEATHING
White lead, zinc wliite (oxide of zinc) and leaded zincs (mixtures of zinc oxide and sulphate of lead) are used for the pigments. The lead and zinc pigments are mixed in best paints because zinc alone sometimes causes check and scale, while lead gives rise to scales or blisters. These basic pigments in paint are improved by adding small percentages of finely ground crystal salts, barium sulphate (barytes), oxide of silicon (silex) and aluminum silicate (climaclay), being most often used.
The desired tint is obtained by add- ing colored pigments, the more usual of which are lampblack, umbre, ochre, sienna, chrome yellow and Prussian blue.
Pure raw linseed oil is the best for general paint use on wood. It causes rapid drying and gives a hard finish. Boiled and raw oils are mixed for metallic paints.
Substitutes for linseed oil are menhaden fish oil, used in marine paints because it resists moisture. It is apt to darken and to take dust. China wood oil is used for water proofing paints after being tested with driers by heating. Corn oil and cotton seed oil are sometimes used but dry very slowly. Injurious effects are brought about by use of petro- leum or rosin oils. These tend to produce checks and dry slowly.
Paints are sometimes sold in paste form to be thinned when used by add- ing oil. Chief among these are zinc iron and lead oxide pastes.
Red lead is bought dry as a rule and is mixed with free litharge to get best protective results. About 10 to IS percent of litharge is added to the red lead and causes the forma- tion of a hard waterproof skin.
Turpentine is the most commonly used paint thinner although petroleum distillates of about the same weight and quickness of evaporation some- times give good results.
Driers when mixed with paint at- tract oxygen of the air, thus hastening the drying. They are made by boil- ing manganese and lead oxides in oil.
Varnishes are made by melting tree gums in oil and thinning with tur- pentine. For outside work use a "long oil" varnish, i.e. one containing a large amount of oil. The best in- terior varnishes contain small amounts of oil. The best way to select a varnish is by comparative tests under working conditions or by experience of the user or his friends. Many so- called "varnishes" are not at all satis- factory for marine use.
Painting Wooden Hulls
The following is a brief outline of the usual painting procedure for wooden work boats.
All parts of the structure to be permanently covered over, such as where timbers are joined or on the inside of hull and outside of ceiling in a ceiled vessel, should be carefully painted before assembling. Where wood and steel surfaces come together a thick coating of red or white lead and a layer of tar felt should be used.
All surfaces to be painted should be sand-papered smooth. Knots should be touched up with shellac. Wood bruises caused by heads of fast- enings should be plugged with wood if large or puttied up if small. All calking and filling of seams should be done before painting begins.
First fill all seams over calking, plane the surface fair and smooth, mark on the "water line" which is
really above the level at which the boat floats. This line is the upper limit of the "boot topping."
The hull below water if not sheathed with metal, should get at least two coats of good copper paint, but do not apply this paint to iron surfaces.
The hull above water should receive a priming coat and two finishing coats of the selected color. Black, white, dark green are the usual hull colors used for work boats. Boot topping is red or bright green.
Wood rails, fender logs, wood decks, gratings and trim are usually finished natural. All these except decks and gratings should be varnished.
Deck houses and superstructure are sometimes of the same color as the hull above water. Often lighter shades are used, white, gray, reds and buffs being most frequently employed. Canvas decks are finished in grays or buff after laying.
Spars are usually varnished. Stacks may be any distinctive color with markings or insignia. Life boats are of the same color as deck houses. Rails, fixed awnings, life rings, etc., are mostly white.
Inside finishes should be in light shades, such as white, french gray, light green, light buff or natural varnished.
Two or three coats are the usual practice for all painted surfaces.
Painting Steel Structures
When steel is received from the mills it has a coating of "mill scale" or iron oxide which protects it temporarily. After being built into the hull most of this scale has rusted off. Before any steel parts are riveted together, clean the contact surface with wire brushes and apply a thick coating of red lead or other steel priming paint of approved commercial grade.
All surface irregularities can be filled smooth with good trowel cement made for steel. The first coat is the red lead or other selected anticorro- sive, after which parts above water re- ceive two finishing coats of the de- sired color.
The final coat below water line is "anti fouling" paint containing chem- icals, principally mercury oxides, iron oxides and zinc oxides dissolved in shellac and alcohol. Anti fouling paints dry quickly and can be put on during a day in drydock. The usual marine growths are retarded in their tendency to attach to the vessel by these paints, but the effect wears off and the paint must be renewed after the steel has been scraped, usually once every six or nine months.
Wooden hulls to be used in salt
Painting Structure and Sheathing
85
water infested by marine borers should be sheathed with metal or wood.
For a time sheet copper was used as the only metal sheathing. It is still employed in high class work but not so extensively as heretofore, due principally to the prohibitive cost of raw material. Yellow metal (copper alloys) has also found extensive use.
For power workboats an excellent and relatively inexpensive metal sheathing is galvanized sheet iron. This has an added advantage of greater strength and consequently less danger of being torn when strik- ing subsequent obstacles.
All metal sheathing is from 1/32- inch (about No. 20 B. & S. gage) to 1/16 inches thick.
The wooden hull is calked and then coated with thick pitch to the top limit of the metal sheathing. This is usually from 4 to 12 inches above the load water line. A layer of tar felt is sometimes used under the sheathing instead of pitch.
The metal sheets are then fastened on with tacks of similar material. Care should be taken that all seams lap and are tight. No buckles should be in the sheathing and this is avoided by fastening successive sheets from the center to the edges. The entire area of each sheet is studded with tacks at intervals of four to six inches in each direction.
Sometimes if the sheathing is on too tightly it will split after the vessel has been launched. This is due to expansion of the hull planking when absorbing a certain amount of sea water. If there is no danger of dam- age to the wood from borers where the boat is built, it is well to launch the hull before sheathing is applied and later haul it out for sheathing before delivery.
Hotv to Prevent Galvanic Action
If the propeller and other under- water fittings are bronze when iron
i
±
-s-
M/^^ 7'i^/yH
F/TC/t' £)/Z
FIG. 102— HOW WOOD SIIE.4THING IS FITrED ON WOODEN TIULLS
sheathing is used, or if of iron when copper or brass sheathing is fitted, protection against galvanic action in salt water should be provided by us- ing zinc strips on the iron or steel parts near the copper or bronze. These strips are rapidly eaten away and must be renewed about every six or nine months when the boat is drydocked. It 'S best to avoid this source of weakness by making all underwater fittings of the same or electrically similar metals.
Wooden rudders are sheathed in the same manner as the hulls to which fitted.
Where bilge keels or false keels are used, they are apt to wear off or break off frequently. The hull sheathing should therefore be between these appendages and the hull itself
and the sheathing for attached parts is put on after they have been fast- ened in place. (Fig. 101).
Wood sheathing was formerly used in large wooden ships and is still often employed on barges or very heavy workboats. It is usually of the same wood as the hull planking and is fitted with the seams and butts of the sheathing planks staggered with those of the hull timbers. (Fig. 102).
The sheathing is bolted • to the planking and is of about half the hull plank thickness. Thick pitch is ap- plied between the outside of hull and the wood sheathing. Lag screws with heads in recesses which are plugged attach the sheathing to the hull planks and should not extend through the latter. Plank sheathing may be creo- soted to advantage.
86
Tlie Design and Conslrnclion of Power Work Boats
" Elizabeth C." of Greenport, N. Y. A 16 ton Auxiliary Schooner owned by Capt. S. B. Bushnell. Carrying a cargo of 200 bushels of potatoes. Mainpower plant four cylinder 40 H. P. Frisbie engine equipt with a Paragon Reverse Gear. In service seven years.
_ - CHAPTER XIX
How Concrete Power Boats Are Built
CONCRETE as a boat building material has been employed to some extent for years, particu- larly in barges and for small boats. The results in service of such vessels have shown that a very long life may be anticipated, that hull repairs are practically eliminated and that such ves- sels are highly satisfactory. When one takes into account that very little is known of this material in ship work, such results would seem to warrant a hearty endorsement of con- crete small boats of every type, espe- cially if num'bers are constructed from the same design.
Several widely advertised boats have been crudely designed although successful with respect to strength, carrying capacity and seaworthiness. This may have resulted in a popular impression that graceful designs can- not be made of concrete. As a mat- ter of fact, the concrete vessel can be as well designed as those of other materials and it possesses the added advantage of being monolithic (seam- less), a result striven for since the origin of shipbuilding.
Concrete itself is a mixture of Port- land cement with coarser aggregate such as sand and gravel or stone. In marine work, lighter materials are sometimes substituted for the sand and gravel, thus lightening the con- crete without appreciable loss in strength. In an ideal concrete the particles forming the mass are grad- ed as to size, the theory being that the voids between the coarse ma- terial are filled by the finer and that the cement fills the smallest voids and thoroughly coats each particle in the mass. The ingredients are mixed with water to a pasty consistency, then poured between wooden molds or "forms" and allowed to harden or
"set." The amount of water used has a marked effect on the ultimate strength, best results being when the mixture starts to flow on a slope of 3S degrees from the horizontal and will just stay on a shovel. Concrete alone is strong in compression but weak in tension. Steel rods or mesh are therefore imlbedded in ,the mass and so disitributed as to absorb all tensile sitresses. This steel is called the "re-enforcing" and concrete so Strengthened is termed "re-enforced concrete." Sheering strains are also absorbed by the steel rods which run in two directions; longitudinally and transversely. Sometimes wire mesh or metal lath is used in con- junction with steel rods to prevent formation of hair cracks. The steel should be well protected against cor- rosion since it will expand and crack or "spawl" the surrounding concrete and give rise to rust streaks. There is no danger of this if the rods are at a depth of 154 times their diameter from the surface and have been well coated with the cement. Pockets and porous spots are avoiided by tamp- ing the concrete around the steel and vibrating the rods during pouring.
Since there is scant data to deter- mine structure from previous boats such as has been the case in steel or wood designs, it is necessary to make careful strength calculations not only for hogging, sagging and sheer but also to ensure ample strength in resisting local strains.
First the usual weight, buoyancy, load, sheer and bending moment curves are calculated for both light and load displacements with the ves- sel assumed floating on a wave whose length from crest to crest equals that of the vessel. This well known and lengthy calculation is clearly ex-
87
plained in books on naval architecture as previously noted. In these calcu- lations the vessel is taken as a float- ing girder and the strength of sec- tion most severely stressed is de- rived from the formula: S I
M =: C
Here M is the bending moment in foot tons.
S is the maximum unit tensile or compressive stress.
I is the moment of inertia of the midship section.
C is the distance from neutral axis to extreme upper or lower point of the section under stress.
For cargo vessels and others of ordinary form,
M = W X L
30 to 35
Where W is the displacement in tons,
L is the length of vessel in feet.
30 or 35 are constants.
For vessels of unusually shallow hold depth the constant may be as low as 20.
The unit stress S is taken as 16,000 pounds per square inch tension for re-enforcing steel and 850 pounds per square inch compression for con- crete. The section of greatest sheer is at about one-fourth of the length from each end. The greatest allow- able sheering stress is 250 to 300 pounds per square inch in the con- crete.
Longitudinal hull girders are in- cluded in the calculations for moment of inertia in hogging or sagging. Transverse frames are not but should be spaced as determined from local "slab" calculations. Here the hull sur- face is divided into rectangles prefer- ably twice as long as they are wide.
88
The Design and Constriicfion of Poivcr Work Boats
Then from slab streng-th formulas (see "Hoole & Johnson" on re-en- forced concrete) the stresses and pro- portions of concrete and steel are determiined.
Deck strains in slab calculations are obtained from deck loads or if none are carried, a head of water of four feet may be taken on the main deck as representing a wave which has come aboard.
Slab loads on the sides are due to the combined downward thrust of deck load and the side thrust of the water outside, whose head is equal to the molded depth.
Bottom loads are net from down- ward weight of hold cargo, down- ward thrust of deck load through sides and stanchions and upward thrust of buoyancy on outside due to head equaling the molded depth.
In all calculations the number of steel rods is found by assuming them to be of standard commercial dia- meters (from one-sixteenth of an inch
upward in round bars). After the total sectional area of steel has been calculated to withstand the tensile and sheering stresses, the number of rods and their spacing are de- rived by dividing this required total area by the area per rod of the selected size. Usually it is most economical to use rods between %" and Yi" in diameter. Larger rods are used in stanchions and framing. Smaller rods are used in hulls of un- usual thinness (less than 154" thick).
Types and disposition of re-enfor- oing will be considered under "Con- structions."
The theories and factors affecting calculations for strength of re-en- forced concrete are complex and can- not be discussed here at length. Pros- pective builders or owners are re- ferred to the numerous articles and typical plans on concrete ship de- sign published within the past year. Radical departures from these de- signs or even conventional ships
FIG. 103— TYPICAL SECTION OF A CONXHETE HULL UNDER CONSTRUCTIO.N
where best results are desired should be referred to some competent author- ity on the subject of concrete ves- sels.
Fig. 103 is a typical section of a concrete hull under construction on the building ways. Notice that the concrete hull with its reinforcing bars and structural framing is encased in wooden molds or "forms" which are supported by cribbing, scaffolding, trusses and suspension rods.
The inner surface of the outside forms is smooth and shaped to the exact molded surface of the hull These outer forms are of varied con- struction but (for medium sized ves- sels) are from 5^-inch to 2-in<;h thick pine or fir planks with closely fitted edges. Tongue and groove lumber may be used on flat surfaces.
The framework and scaffolding out- side of the forms should be strongly designed but readily removable with- out material damage to the timbers. The forms may be in panels with framing all around the seams to pre- vent getting out of line. When the hull has been molded and the con- crete has hardened or "set", the forms are removed or "stripped" by taking down the scaffolding and sections of form above the bilge, then un- bolting and stripping the bilge forms ; and finally the bottom forms are stripped as follows: First take down alternate cribs under the bottom, strip the forms which the removed cribs had supported, replace the cribs under the exposed concrete, after which the remaining cribs and panels may be taken down and all the cribs replaced under the bare hull.
The reinforcing steel is placed in- side of and supported by the outer forms. Then the inside forms are put up as the pouring of concrete pro- gresses. Owing to the cut up and framed nature of the inner hull sur- face these forms are in small sec- tions so they can be quickly erected, and also to permit their removal through whatever size hatch, scuttle, door or other opening may be in the particular compartment after molding is finished.
When the forms have been erected and the reinforcing steel and all fittings piercing the hull are in plact the next operation is molding the concrete. A coating or wash of lime is applied to forms so they will not adhere to the hull. Then the con- crete is molded by (a) pouring, (b) gunning or (c) a combination of the two.
Before taking up molding, consider the various types of reinforcing mem- bers and their disposition within the
How Concrete Pozvcr Boats Are Built
89
concrete. The main strength is in the basketlike network of rods encased by the hull. This is augmented by girders, beams, frames, floors, keel- sons, stanchions, stringers and bulk- heads; so that the surface of the hull consists of a number of relatively th'in panels or "slabs" supported by the internal framing. Usually the hull steel runs longitudinally and trans- versely, although some ships have been built with the rods diagonal and and at right angles to each other.
There are many kinds of rods and more methods of spacing and securing them in place. Rods or bars are of two principal kinds, (a) the plain rounds and (b) the deformed bars. The plain round bars are sufficient for all practical purposes. Some en- gineers contend that deformed bars are more securely bonded to the con- crete and perhaps this is so. At any rate, the round bars if properly spaced and secured give excellent service and are therefore considered by the writer as answering all requirements.
Regardless of the type of rod se- lected these must be supported at the correct distance from the surface of the concrete and at their proper spacing between centers in both di- rections. If rods are not securely held in place they will sag toward or to the surface of the concrete, thus becoming exposed when forms are stripped and requiring the concrete to be cut out at such spots so the rods can be bent into place. The rods are also apt to slide on one another and become irregularly spaced when molding takes place. This will locally weaken the structure and pro- duce undesirable voids. The sim- plest and usual way to support bars is by small concrete blocks or metal clips between them and the outer forms (Figs. 104 and 105). These are spaced closely enough to carry the rods without appreciable sag and remain imbedded in the concrete after forms have been stripped.
The rods are prevented from slip- ping on each other by wiring them together at alternate intersections or by welding them at these points. These are the methods usually em- ployed for shore structures of con- crete where most of the surfaces are flat slabs of simple curvature. They have been used in many concrete vessels but are not considered the most positive and economical for this purpose. Some type of molded guide bar of flat iron, angle or other struc- tural shape which can be bent to the curvature at any transverse section and then slotted or punched to re- ceive the rods, would be better.
//a/i>e fvK/fs
FIG. 104— MET.VL CLIPS USED TO SUPPORT LONGITUDINAL RODS
Such a system has been employed satisfactorily in a number of con- crete hulls with excellent results and is shown in Fig. 106. The supporting framework of transverse and longi- tudinal angles is riveted together and erected in the forms. The spacing of these angles is about four feet in each direction and they are very light. The round bars are then threaded through or laid into the punched slots by unskilled laboi.
Bulkheads are constructed and re- inforced the same as the shell. All door frames, pipe stuffing boxes or other aperatures must be located in the forms before molding begins.
The number of rows of reinforcing
wires of light steel rounds (from J^ inch to y% inch in diameter) absorb the sheering stresses in each member. The girders and stanchions are calcu- lated to withstand the loads on deck, side and bottom slab areas which they support. For stanchions this area is the distance between them in each direction. For frames it is their spacing on the ships side in bending and half the distance between ships side and the first row of stanchions in compression. For beams and gird- ers it is their spacing times their span. Details of beam and column calculations are in texts on rein- forced concrete construction.
Reinforcing rods should be as long
/,Vi/P£ I'^a/rir^i
v/zmzm^'^ '':':-:...mm^
FIG. 105— METHOD USED IN HOLDING RODS IN PLACE FOI{ POURING FORMS
depends on the steel required. A general rule is that diameter of rods ihould be less than one-fifth of the thickness of concrete in which imbed- ded. Fig. 104 shows two rows of longitudinal and one row of trans- verse bars. Figs. 105 and 106 show one row of bars in each direction. Sometimes wire mesh or expanded metal is fastened to the outer row of bars to prevent the formation of hair cracks in the concrete.
Columns or "stanchions" and gird- ers are constructed as in Fig. 107. Extra heavy rods (from J4 inch to 1^ inches in diameter) take the prin- ciple stresses being run up and hooked over as shown. Stirrups and binding
as possible and the lapped or butted ends should be well staggered to prevent local weakening of the structure.
The simplest way to join rod ends is by lapping them at lleast 40 diameters and binding them with wire. Special clamps are made which grip the butted ends of rods similarly to an outside pipe nipple. Best of all the butted ends can be welded.
Since the girth of cross sections on the hull becomes less toward the bow and stern than it is amidships, the rod spacing will vary throughout the length of all types of vessels ex- cept those with box sections such as the simplest barges. When the rods
Ojre/z. Fbami
FIG.106— MOLDED GUIDE BAR PUNCHED TO RECEIVE RODS. THIS IS A VERY S.WISF.VCTORY .METHOD USED WITH EXCELLENT RESULTS
90
The Design and Construction of Power Work Boats
T
/i-aXt-UL-i.lli-fili:liJT-i-'-'=KiJJ>yjJ.tiJ
FIG. 107— CONSTRUCTION OF STANCHIONS AND GIRDERS
Corracre Ponat Tiy6.
• SoHT^i-f-re
Bom Pure
Sect/oa/ 'Afi'
FIG. 108 AND 109— BOW AND STERN CONSTRUCTION FOR A CONCRETE WORKBOAT
come closer than half their spacing amidships, they are dropped.
Rods at the stem and stern are run over to the other side of the hull and hooked into the steel struc- ture at these points. Fig. 108 shows bow construction for the workboat of concrete. A "V" shaped steel plate or a "T" bar form the cut- water and are anchored into the con- crete as shown (107-b and c). The rod ends pass through the anchors and hook over.
Stern construction is a point to be carefully studied. If the conventional "deadwood" type is followed, it is necessary to support the forged or cast steel stern frame by large steel plates anchored into the hull. There must also be a deep and heavy block of concrete which contributes no strength, reduces the cargo dead- weight and is very crude.
Fig. 109 is a type considered stronger, simpler and lighter. It was used in two classes of concrete ves- sels designed by the writer and has proven successful. The line of counter is produced to its intersection with the keel '.vhich it joins by a circular arc. The cross sections at any point of this stern are "V" shaped. Care should be taken not to have flattened sections which would cause eddying in the vessel's wake and render it difficult to steer properly. The rud- der is balanced and supported by a cast steel bracket which has a large palm through bolted to the hull. A strut supports the propeller, being se- cured as shown for single or twin screw vessels. Iron pipe or sheet steel tubes form the rudder trunk and also receive the stern tube.
All hull fittings are similar to those previously described and are bolted through the concrete with wooden pads on the deck to which they are attached. Short lengths of pipe one- eighth inch larger in diameter than the bolts are inserted in the forms before molding and the flanges for attaching the fittings can be drilled from templates taken of these pipes after the concrete has set. No anchor bolts should be used if pos- sible and then only where the at- tached equipment is not likely to need removal for repairs or replacement.
Portland cement, sand, coarser ag- gregate and water are used. The ce- ment should be such that about 78 per cent of it will pass through a wire gage of 200 openings per inch. The sand should be clean (free from loam or other impurities) and should feel sharp when rubbed between the fingers. The coarse aggregate should be not over J4 inch in size while
How Concrete Power Boats Are Built
91
for hulls less than 2J4 inches thick, it should be under % inch.
The proportions used vary con- siderably but the following will be found good for all watertight parts of the hull such as shell, bulkheads, water- tight decks, tanks etc.
Two-thirds of a part of cement, one part of sand, one and one-third parts of gravel. The aggregate components are screened to size before mixing and are thoroughly mixed while dry before adding the water. Concrete mixing machines are used for large work and the work of molding should not stop when it has been once start- ed on watertight work. The mixture or "batch" is poured through chutes and conveyed to the proper point in wheelbarrows. The first of these schemes is best calculated to produce good results.
The concrete is carefully tamped in place and the reinforcing rods are vibrated during pouring to release all air bubbles and prevent formation of voids.
A leaner and cheaper concrete (1 part cement, 2 parts sand and 4 parts gravel) may be used for stan- chions, girders and other structural members where strength but not watertightness is required.
Fused shales and clays have been used for hull concrete and found amply strong. They result in a reduc- tion of weight from about 145 pounds for ordinary sand and gravel to be- tween 100 and 120 pounds for the fused aggregates.
Thus far the concrete has been used for hulls only, deckhouses and other superstructure having been of wood or steel. There is, however, no reason why concrete cannot be used above decks except in the light- est partitions.
There are many reasons why con- crete barges and workboats should be used in the future, especially if the main points of design for par- ticular sizes and types become less numerous through compromise and quantity of production.
Regardless of whether power boat hulls are wooden, steel or concrete, the writer feels that their present number
and types will be constantly increasing. When we begin to realize the many advantages of power workboats over those propelled by steam, besides the many uses which could profitably be found for such craft, particularly in the central and eastern portion of these United States; when we awake to their even greater importance than their nu- merous blood sisters, the pleasure power boat, a prosperous future presents itself.
Power workboats could and should be used wherever there are waterways.
They relieve congestion in crowded sec- tions and can do the transporting more cheaply than the rail or truck methods. They promote commerce and can bring the market to many now isolated pro- ducers, whether these be farmers, manu- facturers, fishermen, commuters or any others who rely on cheap means of transportation.
It is hoped that the details described herein will work for more and better power boats and will answer some of the many questions constantly to be met by the practical boat builder and owner.
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riG. 110— DETAUa FOR ATTACHING MISCELLANEOUS FITTINGS
I uu u
APPENDIX I
Working Tables of Scantlings for Power WorKDoats
from 20 to 100 Feet m Lengtk, Including Tugs,
Tenders, and OtKer Heavy Duty Vessels
For Scantlings of Sizes Between Those Given, Use Averages to Stand- ard Timbers
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in n
APPENDIX II
Designs and Details Typical Power Workboats
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112
Power Towboat for Harbor Work
Length over all, 73 feet
Beam, 18 feet 4 inches
Draft, 8 feet
Power, 250 horsepower oil engine
Propeller, 6 feet 6 inches
An oil-burning engine of 250-liorsepower turns a 63^^ foot propeller
^ I ""HE accompanying plans are those of a power towboat ^ designed by R. E. Winslow, of Bristol, R. I. She is 73 feet over all, 18 feet 4 inches beam and 8 feet loaded draft. The follows the general design of the smaller type of steam harbor towboats, but has many interesting features and by using a gas engine running on iow cost fuel she will be able to handle tows that would not pay a big steam tug to handle, as well as saving money owing to the smaller crew and no fuel expense except when under way.
She is designed to handle any ordinary work in a har- bor such as a 20 per cent larger steam tug would be required to do, and can go in shoaler water than a steam tug of similar power. She would be especially adapted to canal towing and river work and still is seaworthy enough to do sound and coastwise work. Her freeboard to deck at bow is 6 feet 10 inches and least 2 feet 11 inches; at stern 3 feet S inches; so she will be quite seaworthy and still not high enough out of water to save unnecessary windage.
113
FOURTEEN DAY USE
RETURN TO DESK FROM WHICH BORROWED
„. /fGINEERING LIBRARY
Ihis book IS due on the last date stamped below,' or
on the date to which renewed.
Renewed books are subjea to immediate recall.
LOAN
'JUN 2d m
LD 21-100m-2,'55 (8139822)476
General Library University of California Berkeley ^m
X
YF 00372
mm
46i;333
UNIVERSITY OF CALIFORNIA LIBRARY