Boys' Book of Model Boats

BEFORE taking up the construction of any of the model power boats described in this book, it will be well for the young boat-builder to become acquainted with such terms as buoyancy, displacement, center of gravity, etc. Knowledge of these subjects is more or less necessary if successful boats are to be made. Aside from this, they are terms that every boy who claims an interest in boats should understand.

"How does a steel boat float?" is a question that many boys ask. The reason they usually designate a steel boat is probably because steel is so much heavier than water. But many things heavier than water can be made to float if they are in the form of a boat. Concrete, for instance, is now being used in ship construction, and this substance, when reinforced with steel rods, is very much heavier than water.

Before learning how a boat floats, what is known as "specific gravity" must be thoroughly understood. Gravity is a force that is continuously "pulling" everything toward the center of the earth. It is gravity that gives a body "weight." Some substances are heavier than others; or, to be more correct, it is said that the specific gravity of one substance is greater than that of another. It will be well to keep in mind that specific gravity merely refers to weight. It is simply a scientific term. The specific gravity of a substance is always expressed by a figure that tells how much heavier any substance is than water, because water has been chosen as a standard.

The specific gravity of water is 1. The specific gravity of gold is 19.26, meaning that it is about 191/4 times heavier than water. The specific gravity of a piece of oak is 0.86, which shows that it is not quite so heavy as water. One cubic foot of water weighs 62.42 pounds. It will be understood that a cubic foot of gold would weight 19.26 x 62.42, because it is 19.26 times heavier than water. A cubic foot of oak, however, would weigh only 54 pounds, because it has been found that it has a specific gravity of only 0.86 which is less than water.

A cubic foot of oak (see Fig. 1), with a weight of 54 pounds, will float when placed in water. The cubic foot of brass (B), however, will not float, because it weights 8.1 times as much as water. For the present, then, it can be said that a substance lighter than water will float in water, but that substances heavier than water, such as iron, lead, gold, silver, etc., will not float. If the cubic foot of oak (A) were placed in water, it would sink to the depth shown at C. When the block sinks into the water, a certain amount of water will be forced away or "displaced"; that is, the block in sinking occupies a space that was previously occupied or filled with water. The oak block sinks to within a short distance of the top because the oak is really just a trifle lighter than water. If a pine block were placed in the water it would sink only to the distance shown at D, since the weight of pine is less than oak, or only 34.6 pounds per cubic foot. A pine block will, then, displace only about 34.6 pounds of water, which leaves nearly half of the block out of the water. Thus, it will be seen that for a given volume (size) a cubic foot of wood will sink to a depth corresponding to its weight. Different kinds of wood have different weights.

If a cubic foot of brass is placed in water, it will sink rapidly to the bottom, because the brass is much heavier than water. How is it, then, that an iron or concrete ship will float? If the cubic foot of brass is rolled or flattened out in a sheet, and formed or pressed into the shape of a boat hull, as shown in Fig. 2, it will float when placed upon the surface of the water. Why is it that brass is caused to float in this way, when it sank so rapidly in the form of a solid square?

It will be remembered that the pine and oak block were caused to float because they displaced a greater weight of water than their own weight. This is just what causes the brass boat-hull to float. If the amount of water actually displaced by the hull could be weighed, it would be found that the weight of the water would be greater than the weight of the hull. It will be understood that the space occupied by the brass boat-hull is far greater than the space occupied by the block of brass before it was rolled out and formed into a hull. What is true of brass holds true of iron, steel, etc. A block of steel will not float, because the water it displaces does not weigh nearly as much as the block. If this block, however, were rolled out into a sheet and the sheet formed into a hollow hull, the hull would float, because it would displace a volume of water that would more than total the weight of the steel in the hull.

In the case of the brass boat-hull, it would be found that a greater portion of the hull would remain out of the water. The hull, then, could be loaded until the top of it came within a safe distance from the water. As the load is increased, the hull sinks deeper and deeper. The capacity of big boats is reckoned in tons. If a boat had a carrying capacity of ten tons it would sink to what is called its "load water-line" (L.W.L.) when carrying ten tons. As a load or cargo is removed from a vessel it rises out of the water.

What if the hull of a boat has a hole in it? If the hole is below the water-line, water will leak in and in time completely fill the inside of the hull, causing the boat to sink. Also, if too great a load or cargo were placed in a boat, it would sink. It must be understood that water leaking into a boat increases its load, and if it is not stopped it will cause the boat to sink.

The center of gravity of a boat is a very important matter. First, attention will be directed to the meaning of "center of gravity." If a one-foot ruler is made to balance (as shown in Fig. 3) at the six-inch mark, the point at which it balances will be very close to the center of gravity. The real center, however, will be in the middle of the wood of which the rule is composed. It should constantly be kept in mind that this "center of gravity" is a purely imaginary point.

Look at Fig. 4. If wires are arranged in a wooden frame, as shown, the point where the wires cross will be the center of gravity if the square formed by the wooden strips is solid. Every body, no matter what its shape, has a center of gravity. The center of gravity is really an imaginary point in a body, at the center of its mass. Oftentimes engineers are heard saying that the center of gravity of a certain object is too high or too low. Fig. 5 shows the center of gravity in a boat. If the center of gravity in a boat is too high (as illustrated in Fig. 6) the boat is said to be topheavy and unsafe. When a boat is topheavy or its center of gravity is too high, the boat is liable to capsize. In fact, some very serious marine accidents have been caused by this fault.

The center of gravity (or center of weight) in a boat should be as low as possible. A boat with a low center of gravity will be very stable in the water and difficult to capsize. This is true of model boats just as much as it is true of large boats. The model boat builder must keep the weight of his boat as near the bottom as possible. For instance, if a heavy cabin were built on a frail little hull, the boat would be very unstable and would probably capsize easily.

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MODEL boat-hulls are generally made by one of two methods. One method is that of cutting the hull from a solid piece of wood. The other method is commonly known as the "bread-and-butter" system. The hull is built up of planks laid on top one of another with marine glue spread between them. The last-mentioned method (which shall hereafter be called the built-up method) possesses many advantages over the first.

Cutting a model boat-hull from a solid piece of wood is by no means a simple or easy task, especially for beginners. Of course, after several hulls have been produced in this fashion, the worker becomes practised in cutting them out.

The construction of hulls on the built-up principle will be described first. For the sake of convenience, the drawings of the boat-hull shown in Figs. 7 and 8 will be followed out. Before going further it will be well to understand drawings of boat-hulls; that is, how to know the lines of a boat from a drawing. By the "lines" is meant its shape. Marine architects employ a regular method in drawing boat-hulls. Fig. 7 shows the side of a boat and half of the deck plan. It will be seen that this drawing does not tell much about the real shape of the boat, and if a hull were to be produced according to the shape given, the builder would have to use his own judgment as to the outline of the hull at different places. For convenience, the boat is divided into ten sections, represented by the lines 0 to 10. It will be seen that the shape of the hull at section 2 will be different from the shape of the hull at section 8. Again, section 0 will be much narrower than section 5.

Now look at Fig. 8. Note the shape of the cross-section of the hull at the different sections. For instance, the line at section 1 in Fig. 8 represents the shape of the hull at section 1 in Fig. 7. It must be remembered, however, that this is only half of the section, and that the line 1 in Fig. 8 would have to be duplicated by another line to show the true shape. The cross-section of the boat at section 0 is shown in Fig. 9. One half of the drawing in Fig. 8 represents the forward half of the hull, and the other half represents the stern half of the hull. If the shape of the boat at section 10 is desired, the line 10 in Fig. 8 could be traced on a piece of tissue paper. The paper could then be folded in half and the line first made traced on the second half. This would then produce the section of the boat at point 10. Thus, by closely examining Fig. 8 the shape of the entire hull can be seen.

If pieces of wire could be used to form the lines of the hull at the various sections, it would appear as shown in Fig. 10 when assembled.

Notice that in Fig. 8 there is a load water-line, which the vessel sinks to when loaded, and the second and first load water-line, which the vessel sinks to when only partially loaded or when carrying no load aside from its regular necessary equipment. The keel line of the boat is the line that runs along the bottom from bow to stern. (The bow of the boat is the front and the stern the back.)

Motor-boating and marine magazines often publish the lines of different boats, and if the young boat-builder understands how to read boat drawings he will be able to make a model of any boat that is so described.

Directions will now be given regarding the method of producing a boat-hull similar to the lines shown in Figs. 7 and 8, by the built-up method of construction.

First, it will be necessary to procure the lumber. Several clean white pine boards will be very suitable to work with, and will not require much skill in handling. Let us assume that the boat-hull is to measure 22 inches in length, with a depth of 4 inches. The beam, which is the width of the boat at its widest point, will be 5 inches. (It will be well to remember what the term "beam" means, since the term will be used constantly throughout the book.)

On a piece of heavy wrapping-paper draw the deck plan full size, that is, 22 inches long by 5 inches at its widest point. Next cut out along the pencil line with a pair of shears. Now lay the paper outline on a plank and mark out the pattern on the wood. Repeat this process with three more planks. When this is done, cut out the boards with a keyhole saw.

After the boards are cut out mark them as shown in Fig. 11. The space marked out on the board must be sawed out in two of the boards, to form the inside of the hull, if the boat is to carry some form of power, such as a battery-motor, or steam-engine. After the lines are marked out, make a hole with a 3/4-inch bit, as shown in Fig. 12. Insert the point of the keyhole saw in one of these holes to start it and cut out the piece. Treat the second board in the same way. The third board must have a smaller portion cut out of the center, owing to the fact that this board is nearer the bottom of the hull, where the width of the boat is narrower. The width of the piece cut out in the third board should not be more than 2 inches.

When this work is done, a very thin layer of glue is placed over the boards, and they are then laid one on top of another. The boards are then placed in a vise or clamp and allowed to remain there over night. In applying the glue, the builder should be careful not to put too much on the boards. Too much glue is worse than not enough. It should be merely a thin film.

After the boards have been glued together the crude hull will appear, as shown in Fig. 13 .

At this point the hull sections from 0 to 10 must be marked off. By referring again to Fig. 7 it will be seen that the sections 0 to 1 and 9 to 10 are not so far apart as the other sections. Section 0 is 1 inch from the bow of the boat and section 1 is 1 inch from section 0. Sections 2, 3, 4, 5, 6, 7, and 8 are all 1 inch apart. Section 9 is 1 inch from 10 and 10 is 1 inch from the stern. Lines should be drawn across the deck to correspond with these sections, which can be measured off with a ruler. It will now be necessary to cut some templates, or forms, from cardboard to guide the builder in bringing the hull to shape. It will be an easy matter to make these templates by following Fig. 8. A template of section 9 is shown in Fig. 14. It will be necessary to make eleven templates, corresponding to the sections 0 to 10. The templates should be cut from heavy cardboard so they will hold their shapes.

The hull of the boat is now placed in a vise and roughly brought to shape with a draw-knife. After it has been brought to shape by this means a spoke-shave is used. This little tool has an adjustable blade by means of which it is possible to regulate the cut. When the builder starts to use the spoke-shave he should also start to use his templates or forms, applying them sectionally to determine how much more wood he will have to remove to bring the hull to shape. For instance, when he is working in the vicinity of sections 5, 6, and 7 he will apply these forms at the proper points occasionally to determine when enough wood has been removed. This procedure is followed out the entire length of the boat, care being taken to see that both sides are the same and that too much wood is not removed, since there is no remedy for this mistake. The builder who proceeds carefully and is not in too great a hurry to finish the work need not make this mistake.

Of course, it will not be possible to bring the hull to a perfect finish with a spoke-shave. This can be done, however, by the use of a coarse file and sandpaper. The coarse file is used to take the rough marks of the spoke-shave away, and the marks left by the file are in turn removed by the sandpaper. The sandpaper must be applied unsparingly and always with the grain. It will be necessary to use considerable "elbow grease" to obtain a good finish.

Boat-hulls can also be hewn to shape from a solid block, but it will be understood that this method involves more work than the one just described. Of course, the procedure of bringing the hull to shape by the aid of the draw-knife, spoke-shave, and templates is the same, but the hollowing out of the inside of the hull will be a much more difficult job. However, with a couple of good sharp chisels and a gouge the work will not be so difficult as at first appears. The use of an auger and bit will greatly aid in the work. After the outside of the hull is brought to shape the wooden form is drilled with holes, as shown in Fig. 15. This will make it much easier to chip the wood away. After the major portion of the wood has been taken out with the chisel, the gouge is brought into use. The gouge should be used very carefully, since it will easily go through the entire hull if it is not handled properly. For the beginner it is not safe to make a hull less than 1/2 inch in thickness. Of course, it is not necessary to carefully finish the inside of the hull, since it is covered up with the deck and cabin.

The solid hull has one advantage over the built-up hull. It is not affected by moisture and it is therefore not so liable to warp and lose its shape. It will also stand more rough usage.

There is still another method of producing a boat-hull. This hull is known as the Sharpie type. A Sharpie hull is shown in Fig. 16. The method of producing a hull of this type will be seen quite clearly by reference to Fig. 17, which shows the boards and parts cut out ready to assemble. The boards are made from 1/8-inch mahogany, which can be obtained at any lumber-yard. First, the bow piece is cut to shape and carefully finished. Then the two side pieces are fastened to it, as shown in Fig. 18. The screws used should be brass, since iron screws will rust and cause trouble. Three screws should be used for each side board, and they should be driven into the bow piece so that the screws on one side will not interfere with those on the other. The first cross-piece is then screwed in place, as shown in Fig. 19. The second and third cross-pieces are then screwed in place and the back or stern piece attached. The bottom of the boat is then carefully put in place with small screws. It will be noticed that the bottom board of the boat is cut to fit the inside of the bottom. It is held in place with small brass brads. The crevices or seams along the bottom of the boat should be carefully covered with pitch or marine glue to prevent leakage when the boat is in the water. The bow of the boat should be finished off nicely to a point with a heavy file or a wood-rasp.

This type of hull is extremely easy to produce and it is capable of carrying a considerable load. However, it is not a good type to use for all kinds of boats. It makes a splendid little pleasure yacht or submarine-chaser, but for a torpedo-boat destroyer or a freighter it would not be suitable.

The young model boat builder is advised not to try to construct hulls from metal. This is a very difficult task even for the thoroughly experienced mechanic. Wood is much easier to work with and will produce the same results.

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THIS Chapter will be devoted to the construction of very simple types of boats. The boats described will be constructed largely with blocks of wood cut into various shapes and sizes. The results obtainable by this method of construction are surprising, and there are few types of boats that cannot be modeled by following the method. After the model-builder has constructed a few boats along this principle he will be able to duplicate the general appearance of almost any craft he sees by carefully planning and cutting the blocks he uses.

The first boat described is a submarine. This is shown in Fig. 20. Four blocks of wood form the basis of its construction, and these are cut from 1-inch stock, as shown in the drawing. Such a submarine can be made practically any size up to 12 inches in length. Beyond this size they begin to look out of proportion and they are more difficult to propel. After nailing the blocks together as shown in the drawing, a small piece of sheet brass is bent at right angles and tacked to the stern piece. This is to act as a bearing for the propeller.

The propeller-shaft is bent into a hook over which rubber bands are placed. The opposite end of the rubber bands are fastened to a screw-eye driven into the under side of the bow. A heavy piece of copper wire is fastened to the stern of the boat by staples, and bent as shown. A rudder is then cut from thin sheet brass, and the end of it is bent around a piece of wire larger in diameter than the wire used for the rudder-post. It is then taken from this wire and slipped over the wire on the boat. It should be pinched in place by a pair of pliers, so that it will stay in any position in which it is put. The end of the wire is bent over so that the rudder will not slip off. The boat can be steered in a circle or it can be made to go straight, depending upon the position of the propeller.

The horizontal rudders are mounted forward, as shown. They are made from thin sheet brass bent as indicated in the little insertion. A hole is drilled in them as shown, and a screw is placed through these to hold the rudders to the side of the craft. The screws should be tightened so that the rudders will stay at any angle at which they are put. If the boat is to be submerged the rudders are pointed as shown. If the boat is to travel on the surface of the water the rudders are brought up into a horizontal position or parallel with the deck. A little gray paint placed on this model will greatly improve its appearance.

Another submarine, more complicated than the one just described, is shown in Fig. 21 . The body of this submarine is formed by a part of a broomstick or shovel-handle. This submarine is truer to type and can be made with very little trouble. The piece of broomstick or shovel-handle is cut 22 inches in length. It is pointed at each end, and part of it is planed off to form the upper deck. When this is done, a small flat piece is cut as shown, and nailed or screwed to the flat portion. The conning-tower and periscope are placed on the upper deck, as shown. The rudder on this craft is not made adjustable, so that it always travels in a perfectly straight line. The horizontal rudders however, are made adjustable, and the boat is therefore able to travel upon the surface or submerge, depending upon the position of the rudder.

The power plant of this boat is made up of rubber bands. The power transmission to the propeller is a little different than the one previously described. A gear and a pinion are salvaged from the works of an old alarm-clock, and mounted on a piece of brass, as shown. A little soldering will be necessary here to make a good job. By using the gear meshing with the pinion a considerable increase in the speed of the propeller is obtained, and therefore the speed of the boat is considerably increased. The method of holding the power plant to the bottom of the boat is made very clear. In order to bring the boat down to the proper level in the water, a strip of sheet lead can be tacked to the bottom. The builder should take care to get a piece of lead just the correct weight to leave the surface of the deck awash. A coat of gray paint will also greatly improve the appearance of this craft.

Attention is directed to the construction of boats of different types made without power plants. Many interesting little crafts can be produced in this way, and the energetic model-builder can produce a whole model harbor or dock-yard by constructing a number of boats of different types according to the following instructions.

The first boat described will be the tug Mary Ann shown in Fig. 22 and Fig. 23. The blocks necessary to construct this boat are shown in Fig. 24. The hull of the boat is produced by three pieces of wood sawed out to the same shape with a keyhole saw and glued together. After the glue is dry the blocks are placed in a vise and the top one or deck block is planed down as shown. It will be seen that the deck inclines slightly toward the stern of the boat. When this is done the hull is turned upside down and the bottom of the stern planed off as illustrated. The outside of the hull can be finished up with a sharp knife and a jack-plane.

The little bow piece can also then be tacked in place. After this the pieces that form the hull can be nailed together from the bottom and from the top. This is quite necessary, for glue will not hold them in place after the boat has become thoroughly soaked with water.

The cabin and engine-room are shown very clearly in the illustration and little need be said about erecting this part of the craft. The two doors and window on the side of the cabin are made by cutting out small pieces of cigar-box wood and gluing them to the cabin and engine-room. A good substitute for the wood can be found in tin, but of course this would have to be tacked on. The little skylight on the back of the tug is made by a single block covered by two pieces of cigar-box wood.

In order to stabilize the craft and to bring her down to the proper water-line, a lead keel must be nailed to the bottom. The weight of this keel will have to be adjusted until the boat rests properly in the water. The reader will notice that no dimensions have been given for this boat. This is because most boys will wish to build different sized boats, and therefore it has not been deemed advisable to dimension the boats described in this Chapter. What the author desires to do is to impart the principles of construction, so that every boy may use his own ingenuity in regard to size and proportion of length to beam.

If tugs are constructed according to the design outlined above, the model boat builder will also desire to have something that the tug can haul. A very simple barge for this purpose is outlined in Figs. 25 and 26. This is formed of a single slab with the ends cut at an angle as illustrated. A square flat piece is then tacked to the upper deck, which acts as a cover. Four posts are then put in place in the same way as those on the tug. One is placed in each corner. A boat or a scow like this is generally painted red, and the model described can be made to look much more realistic by painting it this color.

These barges are so easy to construct that the model-builder should make three or four of them at a time. If the pieces for several are cut out at the same time, the construction will be just that much easier. If the boat does not sink far enough into the water, a piece of lead should be placed on the bottom to bring it down. This piece of lead should be placed as near the center as it is possible to get it. Otherwise the boat will list or tip at one end or the other. With a little patience and care the weight can be so adjusted on the bottom as to bring the scow to a perfectly level position. The reader will understand that the water-line of a scow or any boat made according to the directions in this book will depend largely upon the nature of the wood. In the first Chapter of the book it was pointed out that the specific gravity of different woods varies, and therefore the buoyancy will vary.

A model freighter is shown in Fig. 27. The hull of this boat can be formed by two 11/2-inch planks. These will require a little hard work to cut out; but, on the other hand, the effort will be entirely justified by the pleasing appearance of the little craft that can be produced in this way. A bow and stern block to raise the deck are cut out and nailed in place, as shown. A cabin is also placed on the stern of the craft, and this is formed by a block with a piece of cigar-box wood placed on the top. The cigar-box wood should project a little over the edges to form a canopy. The center of the deck can be raised by a third block; and three independent blocks, two large ones and a small one, form the main cabin. Sandwiched in between these blocks are three pieces of cigar-box wood. The remaining details of the craft are so simple that they may easily be made by following the diagram.

Let us turn our attention to model war-ships. A torpedo-boat destroyer is clearly illustrated in Figs. 28 and 29. This is very simple to construct and makes a pleasing craft when finished. The hull is formed by two blocks. One of these forms the raised deck on the bow of the boat. The cabin is built up on this raised deck. It will be seen that the part of the hull that rests in the water is formed by one block. In building boats of this nature the constructor should be careful to keep them long and slender, since torpedo-boat destroyers are always of this type. They are high-speed craft, and their displacement must therefore be as small as possible. Some of these boats carry four stacks and some two. The author prefers four stacks as giving the boat a better appearance than two. The two little cabins near the stern of the boat are placed there merely to take away the plainness of construction. The guns mounted forward and aft are merely round pieces of wood with a piece of wire bent around them and forced into a hole in the deck.

The boat-builder should not be satisfied with one or two of these craft; he should make a whole fleet. This will afford the average boy a great amount of pleasure, since he can add to his fleet from time to time and have official launchings. Each boat can also be given a name and a number. A little gray paint on the hull of these boats and black on the stacks gives them a very presentable appearance.

A battleship is shown in Fig. 30. A battleship should be at least twice as long as a torpedo-boat destroyer. A view of the battleship as it will look in the water is shown in Fig. 31. By carefully examining this drawing the builder will be able to see just the number and shape of the blocks that enter into the construction of the craft. The battleship is provided with four main batteries mounted in turrets, one forward and three aft. A mast is also built, and strings run from it to the top of the main cabin and to the end of one of the turrets mounted aft. A screw is placed through the centers of the fore and aft turrets, so they can be turned to any position. Battleships should be painted gray. It will be necessary to place rather a heavy keel on the boat just described in order to bring it down to the proper depth in the water. Otherwise it will be topheavy and will capsize very easily. A fleet of battleships and battle-cruisers can easily be made according to the foregoing instructions, and the builder should not be satisfied with producing only one.

A pleasure yacht is illustrated in Fig. 32. The hull of this craft is formed by two boards nailed together. The cabins are very simple, being formed by a solid block of wood with a piece of cigar-box wood tacked to the top. The windows and doors are marked in place with a soft lead-pencil, and the stack is mounted midway between the two cabins. A wireless antenna should be placed on the boat, with a few guy-wires from the masts run to various parts of the deck. A lead-in wire also runs down into one of the cabins. The hull of this boat should be painted pure white. The deck can be left its natural color, while the stack should be painted black and the cabins white with green trimmings.

Almost any type of boat can be produced by the use of simple blocks of wood and other miscellaneous pieces easily brought to shape from ordinary materials. This method of construction offers a wonderful opportunity for the boy to exercise his creative faculties.

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