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THE BUILT-UP SHIP MODEL
By Charles G. Davis
Dover Publications, Inc.Copyright © 2014 Dover Publications, Inc.
All rights reserved.
THE BUILT-UP SHIP MODEL
THE language of the sea and the men who have to do with the building of ships, is so full of strange names and technicalities, totally unintelligible to the layman, that many writers on nautical matters pass up all such as so much Chinese or Arabic; and the result has been misleading statements such as that it is only we, of this twentieth century, who have gone carefully into calculating and planning out our ships before building them. The public at large has been led to believe that the best they ever did in the eighteenth century was to whittle out a block model and saw it into sections to get the shape of enough frames to determine the ship's shape, or, to unscrew the horizontal lifts, or layers, of wood, the model was made of, and so plot the shape of the frames.
If one will but take the time to investigate this subject, and educate himself sufficiently in the study of naval architecture to comprehend what is written in some of the really wonderful books that have been published in the 1700's, he will find that the old shipbuilders made as many calculations and plans then as they do now. In those days the nation's greatest scientists were ordered by the king to study the subject, in order to make every test of the ships that could be made. They even went to sea on the ships to study their subject at first hand and all sorts of experiments were made not only in England but in France, Holland and Sweden.
There were, of course, men at that time, just as there are now, who built by "rule of thumb" methods. Men who built from crude models and even from no model at all. They simply framed the ship to suit the eye. Such men left no records by which their work might, in later years, be reproduced; but the men who planned their work have fortunately left us much information, both on big ships and sometimes on small craft.
This makes it possible for us to now build up small replicas of their ships from the shape of those ships which have been printed in books of plans, or whose measurements are given in tables of offsets. Where the man of today gets confused is when he tries to figure out, piece by piece, how these ships were built, as this phase of the subject, except in a few cases, has not been preserved in its entirety. Some few plans, such as the framing plan, or a deck plan, are shown, but the hundred and one knotty points that come up are not explained. It is like having bricks to build a house, but no mortar. In this work we will try to supply the mortar so that the bricks will not fall down for want of something to hold them together.
No one historian has given us all the data and it is only by reading the works of many of them and compiling the rules of old-time shipbuilding, that we have found the required information. Take the subject of fastenings, as an example, a most vital part of ship construction, and try to find any definite rule to go by. It was part of the shipwright's education to know how many iron spikes and how many treenails were to be put into each piece of wood; how many drift bolts and how many clinched bolts each different joint required and of what size. What then was common knowledge among all associated with shipping matters, was not considered worth treating on. The sizes of the various timbers and the more intricate problems of how to lay out and cut the shape of cant timbers, wing transoms, hair bracket rails, harpin moulds, etc., we find treated at great length, as they were problems in geometric projection on which authors loved to air their knowledge.
In my youth I had a peculiar position where I had a chance to observe this. I was apprenticed to study naval architecture under a man fresh from a naval college, just staring in business, where everything was higher mathematics. I listened to him all day and then went home at night to where my future father-in-law, a practical shipbuilder, was doing the actual wood cutting and fastening. This was a combination of theory and practice that would be hard to beat. I once spent a Sunday morning in a City Island mould loft, at a shipyard whose proprietor was demonstrating to my naval architect employer that the moulded edge of a transom took on the curve he said it did, in contradiction to the way the architects' plans had it drawn in,—and the practical man proved his point.
Now let us build a model of a ship, a real model, one that we and our descendants can look at with pride. Anyone who thinks such a model undeserving of this esteem has but to try his hand at it once and he will soon admit it is an undertaking. It is not like whittling a boat out of a block of wood. There you have something rigid, solid, something that will hold its shape, but in putting up a frame of a ship, piece by piece, you have the problem of keeping the whole structure straight and true. On a real ship a chalk line down the center, from stem to sternpost, gives you a line to drop plumb-bobs from and see that each frame is set up true, the frames being held by shores to the ground and set up by wedges. On a model, a straight edge over the top is the best means, as it leaves the frames all free and clear so you can get at them and gives something to which the frames can be temporarily braced, until most of the frames are in when it may be removed.
Another method is to first set up at intervals along the keel, temporary wooden moulds and then tack a slat of wood down the center, fastened at bow and stern, to hold them in place, one edge of the slat being faired up to a straight edge and lined up on the center marks made on each mould so as to be sure they all set true in line as they must in order to make a fair ship. Then around the outside of these moulds bend small wooden battens, tacking them fast to each mould. With these battens in place you will find it easier to set up each set of frames as they are ready to go in and you can visualize better the amount of bevel to which each frame's edges, both inside and outside, must be cut. Each frame should fit true against the battens, for if it does not do so, when it is put in it will have to be shaped off afterwards so that when the planking is put on it will lay in a fair surface, showing no bumps from forward to aft.
The moulds may be taken out when you have enough frames in to hold the boat's shape true, and frames may then be substituted in their place.
First of all, however, some base on which to build our ship must be provided, something that will hold its shape true and not warp. If we were only building a small vessel, a pine board as long as the model and as wide, with cross battens or cleats of wood screwed fast across it, underneath, at about four intervals to prevent its warping, would do and then down the center of this, on top, fasten a straight, square stick, about an inch square, on which to lay the keel.
So many model builders, when they first start in the game, try to build three-decked, one hundred and twenty gun line-of-battle ships, and nine-tenths of them fall by the wayside. That is a job that should be reserved until one has thoroughly mastered the art of shipbuilding, for the problem is much aggravated by the two additional gun decks. A single-decked vessel, like a frigate, is enough to stall many men, so we will first try our hand at one of these single deckers, a little brig-of-war called the Lexington, that was in America's first naval fleet fitted out at Philadelphia in 1775. In learning how to build her you can find out all that is necessary to build any single-decked ship, such as a frigate or sloop-of-war or a merchant ship. The only difference is in the plans you use to build from. The dimensions of the Lexington are: length on gun deck, go feet, 0 inches; length on keel, 76 feet, 5 inches; beam, 22 feet, 8 inches; depth, 9 feet, 0 inches; tonnage, 166 tons.
The first step in making a built-up model after we have decided what ship we are going to build, is to get a set of plans of that ship to build by. Shipbuilding is an intricate job, far more so than any other kind of construction I know of, and wooden shipbuilding is worse than steel ship construction as the fastening of wood members is an art in itself. Wood shipyards had certain gangs of men trained to one class of work,—broad axe men, sawyers, plankers, framers, fasteners, —yes, and it even became so specialized in a certain section that in later years to bore a hole you had to send for one of the Wood Borers Association's men to do it. These men had all kinds of augers and specialized in nothing but boring holes. It may sound simple enough to bore a hole but if you have ever bored by hand keelson bolt holes through four, five and six feet of oak you will know that it is an art to do so and not have your auger "run" and become jammed.
But to return to our plans; if we were given a set of ship plans, showing her shape and her lines; and another set showing her construction, her spar plan, rigging plan and a sail plan, are we ready to begin and build her or not? The answer is no. To cut wood we have to lay those plans out, full size on a clean board floor, or mould loft, as it is called, and interpolate all the frames between the few shown in most plans. In a mould loft they make the full-sized patterns or moulds of thin wood, ½ inch or ¾ inch stuff, of every piece of wood that goes into the ship. These go out to the shipyard and there the sawyer gang lays the patterns out on the timber, marks out the shape by cutting a small grooved mark, with a race knife, all around the edges of the pattern on the timber and then the sawyer gang saws it out to that shape and gives it to the shipbuilders. This is comparatively simple, because it is merely cut out, square-edged, to the shape given. But suppose it is part of a frame in the ends of the ship. There, instead of the edges being sawed out square, they take a bevel, as they all do, and that bevel is not the same all the way. That is where complications arise. The men in the mould loft, when they get out a pattern for frames, and it takes eight or ten separate pieces to make one frame, have to mark on the pattern the number of degrees the edge is to be beveled, or mark the angle itself on a small board that goes with the pattern. It may be six degrees at one end and diminish gradually to four degrees at the other end. To cut this the saws are made to tilt from the vertical, being operated by a screw gear, by hand, and can gradually change their angle while cutting. Without laying down the full-sized plans it would be impossible to find out how much bevel there would be. That is why we cannot build a wooden ship from just an ordinary set of plans.
Another point is that all the frames are not drawn out and to cut timber it is necessary to have some definite shape,—a pattern, to cut to. So if our plans do not show the shape of every frame or every other frame, at the least, we must draw them out. So I have taken the ordinary plans (lines and sail plan) and drawn out all the other plans necessary to build from. This is what every shipyard has to do in its mould loft. They have to "LAY THE SHIP DOWN," as it is technically termed, but which is nothing other than drawing her plans out, full size, on a clean, white painted, or clean, wood floor.
Every section which shows the boat's shape, if she were sawed in two at that point, has to be plotted out; not an intricate job, by any means, but a tedious one. The lines, as shown in the plan, are reproduced full size and to facilitate this the naval architect measures off from the paper plans in his office, as accurately as a small scale drawing can be measured, the widths from the center line of the ship to the side and the heights of each line in the sheer plan, measured up from a given base line,—a straight line,—at each given section; the forward perpendicular at the bow; the after perpendicular at the stern transom (the distance between these two representing her official custom house measurement for length); the midship or dead-flat; and the various other vertical sections; and writes all these measurements down in what is called a TABLE OF OFFSET, which is simply these measurements tabulated for convenience. One has to have some system about his work and the men who have to do this kind of work have found it convenient to neatly tabulate the measurements of each section under its given number or letter. You, building only one ship, may do it any way you like. You can take each section and treat it by itself, making a list of its widths from the center line and its heights from the base line, so long as you can reproduce the curve of that section; that is the ultimate object.
These sections are merely a means of reproducing the other curves, the waterlines and the buttock lines. These are as battens drawn from end to end of the ship and show how the surface curves along that line. Great care must be taken, in fairing up these lines, to see that the widths in the plan of the waterlines agree with the width in the corresponding spot in the sections. Give and take, on one or the other, until they do correspond and your eye will detect the one that makes an unfair curved line.
The diagonal lines x, y and z are run just as you would run battens around the frames and give more accurate results than crossing the sections at what more nearly approximates a right-angle intersection or an oblique crossing at some of the waterlines or buttock lines.
The enlarging of the small plan to the full size of the ship, magnifies any slight variation in measurement so that it is in this laying down process the ship's accurate form is obtained, a fair form to build up.
When we have the form of the ship thus accurately delineated, we are ready to proceed with a construction plan and to lay out the thickness of the various timbers in their proper relation one with another. I have done all this for you in Plate No. 3 which shows just how our little brig was put together, and by referring to the photograph of the actual, here reproduced, you can get a pretty clear idea of how it is done.
You must understand at the outset that this is not to be a technical treatise on naval architecture. I will not lead you into deep water but try to show by description and sketches how such timbers as cant frames are put in, and how transom frames are shaped out, and do this without going through pages of projection and technical explanations such as may be found in Steele's "Naval Architecture." I'll try to find a shallow ford where you may wade across and get around this deep water.
Another gap in the necessary information to build, that generally confronts the model shipbuilder, is the question as to how big the various members of a ship's hull should be. Many plans do not give this information which was in the shipbuilder's private notebook. Some of the old descriptions of clipper ships published in the newspapers at the time when they were launched, contain detailed descriptions of their construction, for that was valuable news in the 1850's. Some old works on shipbuilding also give the sizes of all the timbers used in various classes of ships. The "American Lloyds" and the "American Bureau of Shipping," issued books of rules for determining the sizes of various ships timbers, and Samuel H. Pook, naval constructor in the days of sail, has given us condensed rules for determining the size of scantling for ships of war, all being a percentage of the ship's breadth of beam. He also gives the rules for figuring the size of all iron fastenings and much ships' ironwork, such as the chain plates, rudder pintles, etc. These will be found in the Appendix, and by using these rules we may determine, if our plans do not give them to us, the size of scantling for the model we are going to build.
It is the question of fastenings that influences the size of built-up models, because if you try to build on any scale under one-quarter inch you cannot get small enough fastenings. They would be so minute you could not even pick them up, except with a pair of tweezers, and good fastenings are as essential in a model as in a real ship, to hold it together.
Let us take the little 16-gun brig Lexington, of Revolutionary fame, and make a 3/8-inch scaled model as nearly like her as we can. With her plans here given, reconstructed as nearly as may be, we have but the beginning. We have her outline in sheer view, and deck plan or half breadth, and 14 sections of her moulded shape at the marked intervals along her length (Plate Nos. 1 and 2 ) . These sections are spaced so they coincide with some of the actual frames; therefore we have the shape of a few of them. The frames are set up on the keel, in a spacing of two feet, frame to frame. The midship section marked x coincides with frame No. 17. All the other full frames space off every two feet along on the keel. Rule lines vertically, representing them, across both the sheer and the half-breadth plan and plot their shape between those few frames already drawn in as sections. This is not done ordinarily in a small plan drawing, as so many lines would come too close together to be able to identify any particular one; but now we must have each one individually, if we are going to build her. (See the plate where I have so drawn out all the frames that set square across the keel frames NO.5 to No. 33.) In Plate No. 4 (the midship section) all the various members of the ship's construction are designated so you may the better visualize the ship as a whole.
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