BY RAYMOND FRANCIS YATES
WITH NUMEROUS ILLUSTRATIONS FROM DRAWINGS AND PHOTOGRAPHS
NEW YORK THE CENTURY CO.
Copyright, 1920, by THE CENTURY CO.
PRINTED IN U. S. A.
TO LAVERNE YATES A BUILDER OF MODEL BOATS
EVERY boy likes to build boats. The interest in boats seems to be born in the race. The little three-year-old chap is instinctively attracted by a puddle of water in which to sail his "boat," which may take the form of a piece of shingle or common board. Few men have passed through their boyhood days without having built boats at some time.
The author was an ardent boat-builder, and he well remembers how he combed the Children's Department of the local library in search of a book that would tell him something about boats, and especially for information regarding the construction of models. He found books on model airplanes, toys, electricity, radio, and chemistry, but alas! nothing about model boats. He vowed then that when he became a man he would write a book on model boats—a book that would contain all the treasured information he had accumulated during his boat-building years.
This book is the result of that vow, and the author earnestly hopes that it will gladden the heart of every boy who builds and sails a boat. There are probably few happier moments in a boy's life than when he sees his little model steamer proudly make her way across the park pond, or his little sail-boat respond to the summer breeze.
The author takes this opportunity to thank his wife, who acted as his amanuensis in the preparation of this manuscript.
RAYMOND FRANCIS YATES.
I WHY A BOAT FLOATS 3
II THE HULL 12
III HOW TO MAKE SIMPLE BOATS, WITH AND WITHOUT POWER DRIVE 26
IV STEAM AND ELECTRIC PROPULSION 42
V AN ELECTRIC LAUNCH 66
VI A STEAM LAUNCH 75
VII AN ELECTRICALLY DRIVEN LAKE FREIGHTER 91
VIII AN ELECTRIC SUBMARINE-CHASER 98
IX BOAT FITTINGS 107
X THE DESIGN OF MODEL STEAM-ENGINES 126
XI A MODEL FLOATING DRY-DOCK 135
XII OPERATION OF FLASH STEAM POWER PLANTS FOR MODEL BOATS 149
XIII SAILING YACHTS 164
XIV TWO-FOOT SAILING YACHT 184
LIST OF ILLUSTRATIONS
A two-foot steam boat Frontispiece
Getting ready for a trip 72
All ready to go 73
A powerful gasolene blow-torch 112
Just after the race 113
A twin-cylinder steam engine for model marine use 168
A cup-winning model sail boat 169
BOYS' BOOK OF MODEL BOATS
BOYS' BOOK OF MODEL BOATS
WHY A BOAT FLOATS
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 19-1/4 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.
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.
HOW TO MAKE SIMPLE BOATS, WITH AND WITHOUT POWER DRIVE
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 1-1/2-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.
STEAM AND ELECTRIC PROPULSION
BOATS are propelled by two different systems. Some inland-water boats still employ side paddle-wheels, while ocean-going vessels use the more modern propeller or screw.
The paddle-wheel really acts as a continuous oar. Such a wheel is shown in Fig. 33. As the wheel goes around the paddle dips into the water and pushes the boat forward. If the direction of the boat is to be reversed, the rotation of the paddle-wheels is reversed.
Before passing onto the screw, it may be well to explain just how a paddle-wheel causes a boat to move. When a man gets into a rowboat, he generally pushes himself off by placing his oar against the dock or shore and pushing on it. That is just what the paddle does in the water. It dips into the water and pushes against it. It must be remembered, however, that water is unlike a solid substance and it "gives." When a man places his oar against the bank and pushes it, the bank does not move, and all of the man's energy is used in starting the boat. Water, however, does not remain stationary when the paddles push against it, and therefore all of the power it not utilized in moving the boat—part is used in moving the water.
The paddle-wheel is not so efficient in moving a boat as the more modern propeller—or screw, as it is more often called. The screw receives its name from the ordinary metal screw, because its theory of operation is exactly the same. A wood screw, when turned, forces itself into wood. A propeller, when turned, forces itself (and thereby the boat) through the water. A small propeller is illustrated in Fig. 34. This is an ordinary three-blade propeller. (The writer prefers the word propeller instead of screw.)
From the drawing, it will be seen that the propeller-blades are mounted at an angle. This angle of the blades causes them to force water back as they cut through it when the propeller is revolving. This forcing of the water back tends to produce a forward motion of the propeller, and in this way the boat on which the propeller is mounted moves through the water. The propeller is caused to revolve by a steam-engine, steam-turbine, or gasolene-engine, as shown in Fig. 35. Longer boats have more than one propeller. A boat that has two propellers is called a twin-screw boat. A boat driven with four propellers is called a quadruple-screw boat.
When a machine screw is turned around just once, it moves forward a certain distance, as a glance at Fig. 36 will show. The distance the screw moves forward will depend entirely upon the distance between the threads. The distance between the threads is called the pitch of the thread. If the threads are 1/32 inch apart, then the screw will move 1/32 inch every time it revolves.
If a propeller acts in the same way as a screw, then it too must have a pitch. The pitch, or the distance that a propeller will advance in one revolution, is measured in inches. A propeller with a pitch of ten inches should move ten inches through the water at each revolution. However, there is a certain amount of "slip," and a propeller does not actually advance the distance that it should theoretically. The pitch of a propeller is really the distance it would advance in one revolution if it were revolving in an unyielding or solid substance.
To make a simple propeller, first cut out of thin sheet brass three blades as shown at A, Fig. 37. Sheet brass with a thickness of 1/32 inch is very suitable for this purpose. Next, a block, as shown at B, is carefully carved out so that the propeller can be hammered down into the depression. The same block is used for the three blades, so that each will have the same curvature. The block should be cut from oak, since this wood will not split or lose its shape when the forming is done.
The hub is made next. This is shown at C, Fig. 37. The hub, of brass, is made according to the stream-line method. It is filed to shape from a piece of round brass stock. A hole runs lengthwise in the brass, as shown, and a set-screw is used to hold the hub of the propeller-shaft. The method of cutting the slots in the hub is shown at D, Fig. 37. The hub is clamped between two boards placed in the vise, and a hacksaw is used to cut a slot in the hub. The hub is then turned around one third of a revolution, and another slot cut, using the same saw-marks in the boards, so that the angle of the second slot will be the same as the first one. The third slot is cut in the same manner. The three blades that were cut out are now fastened in these slots and held there by solder. This completes the propeller and it is now ready to be fastened upon the propeller-shaft.
Let us consider the general method of putting the propeller-shaft in place. The young boat-builder will readily understand that it would be very impractical merely to bore a hole in the hull of the boat to put the propeller-shaft through. In this way water would surely leak into the hull and the boat would sink in a short time. Some method must be evolved to keep the water out of the hull, and yet allow the propeller-shaft to revolve freely.
The propeller-shaft is arranged within a brass tube, as shown at Fig. 38. The brass tube should be about 1/8 inch larger in diameter than the propeller-shaft. A little brass bushing must also be arranged at each end, as shown. When the propeller-shaft is mounted in place in the tube, there will be a space between it and the tube. Before the propeller-shaft is put in place it is well smeared with vaseline, and when it is placed in the tube the space between the shaft and the tube will be completely filled with it. This will prevent water from entering. Owing to the fact that vaseline is a soft, greasy substance, it will not prevent the rotation of the propeller-shaft. The brass tube is placed through a hole bored in the hull of the boat. The hole should be a trifle smaller than the diameter of the brass tube, so that the tube can be forced into the hole.
One of the simplest methods of propelling a boat is by means of rubber bands. Such a boat is shown in Fig. 39. This is a small wooden hull fitted with a two-blade propeller. The propeller is shown at Fig. 40. It is cut in a single piece and held to the propeller-shaft merely by a drop of solder since there will not be much strain upon it owing to the low power of the rubber-band motor. The opposite end of the propeller-shaft is bent into a hook, and the rubber bands run from this to another hook placed at the bow of the boat. The rubber bands may be similar to those employed by model airplane builders. The motor, of course, must be wound up by turning the propeller around until the bands become twisted into little knots, as shown at Fig. 39. Boats driven by rubber bands cannot be very large unless a great number of rubber bands are used. Even then the power is short-lived. However, building a few small boats driven by rubber-band motors will do much to teach the young boat-builder some valuable lessons in boat construction.
Probably the best method of propelling model boats is the electric method. By building a boat large enough to accommodate two dry batteries or a small storage battery and a little power motor, a very reliable method of propulsion is made possible. The boat must have sufficient displacement to accommodate the weight of the dry-cells and storage battery. A boat two feet long, with a beam of 4-1/2 inches, is large enough to accommodate one dry-cell and a small motor, providing the fittings of the boat are not too heavy.
A suitable power motor for small boats, which will run with either one or two dry-cells, is shown in Fig. 41. The connections for the motor are given clearly in Fig. 42, and a suitable switch to control the motor is shown at Fig. 43.
Owing to its greater power, the storage battery is to be preferred. Dry-cells are extremely heavy and occupy considerable space. They are also costly, since they do not last long and cannot be worked too hard unless they polarize.
A very suitable method of mounting an electric motor is illustrated in Figs. 44 and 45. It will be noticed that the motor is inverted. A small pinion or gear is mounted upon the armature-shaft of the motor. A larger gear (about three times the diameter of the small one) is placed upon the propeller-shaft. This gives a speed reduction of three to one. It will be seen that the propeller-tube is strapped within a strip of brass to a small cross-piece nailed to the bottom board of the hull. The hull is of the built-up type, and the other three boards that go to make it up are not shown. When the three boards are glued in place, a brass strip is run across the top board and the base of the motor is screwed to this. This holds the motor rigidly in place so that it will not move when the power is turned on. The brass strip used should have sufficient thickness to hold the motor rigid. It will also be seen that the motor is tipped slightly so that it will come in line with the propeller-shaft.
It is not always possible to obtain small gears. For this reason the model boat builder may find it necessary to use a different method of fastening the propeller-shaft to the motor. A very good method of doing this is shown in Fig. 46. Here a coiled wire spring is used. This is wound to shape on a rod, and a drop of solder holds it to the propeller and motor shafts. In the method of propulsion shown in Fig. 44 the armature-shaft of the motor must be perfectly in line with the propeller-shaft, or the gears will bind and unsatisfactory operation of the motor will result. With the little spring the motor will not have to be mounted exactly in line with the shaft, and it will also be possible to mount the motor standing up. Of course, if the motor is mounted in this way it will be necessary to make the propeller-shaft longer, as is shown in Fig. 47.
Still another method of driving the propeller is illustrated in Fig. 48. This method is so simple that the author feels explanation to be unnecessary.
Clockwork can often be employed for propulsion purposes, but this method is not very satisfactory. It is also very difficult to obtain suitable clockworks to install in a boat. Oftentimes it will be possible to salvage the works of an old alarm-clock, providing the main-spring is intact. It is a very easy matter to mount the clock-spring and connect it to the propeller. Any one of the aforementioned methods can be employed.
Steam propulsion has its advantages; but, on the other hand, the writer is not inclined to recommend it as strongly as the electric method for reliability. Of course, steam is a more powerful agency in the propulsion of small boats and thereby greater speed is attainable by its use.
Here is a very simple small power plant suitable for driving boats up to 3-1/2 feet in length. The boiler is shown in Figs. 49 and 50. The method of assembling the boiler is pictured clearly in Fig. 49. A brass or copper tube about 2-1/2 inches in diameter is used. Two end pieces are cut to shape and forced into the boiler ends. A hole is drilled in the center of these pieces before they are put in place. After the end pieces are forced in place solder is carefully flowed around their edges. The brass rod is then threaded at each end and placed concentrically within the boiler, as shown in Fig. 49. A nut is placed on each end of this rod and tightened. The nut is then soldered in place. This brass rod, called a stay-rod, prevents the end of the boiler from blowing out when the steam pressure has reached its maximum value. Three holes are drilled in the brass tube, as shown. One is to accommodate the steam feed-pipe that goes to the engine; another is for the safety-valve, and still another for the filling plug. The safety-valve and filling plug are both shown in Fig. 51. The little spring on the safety-valve is adjustable, so that the valve can be regulated in order to prevent it from blowing off at pressures lower than that at which the engine operates.
A suitable firebox for the boiler is shown clearly in Fig. 52. This is cut to shape from stovepipe iron and held together with small rivets. Holes should be punched or drilled in the side of the firebox to give the burner a sufficient supply of air. The burner is illustrated clearly in Fig. 52. The fuel-tank can be made from an ordinary tin can with the cover soldered on, and a hole made for a cork by means of which it is filled with denatured alcohol. A little pipe runs from the fuel-tank to the burner. It is advisable, if possible, to place a small valve in this pipe to cut off the fuel supply when necessary. The only other method of putting the burner out would be to stand it on its end. The burner consists of a rectangular tin box with a top cut out as illustrated. A piece of brass or copper gauze is placed in the top. Asbestos wool is used to fill the can, and the alcohol is drawn into the wool by capillary attraction, where it burns with a steady hot flame at the surface of the copper gauze. In the corner of the can near the feed-pipe another small piece of copper gauze is soldered as shown. This covers up the feed-pipe entrance so that the asbestos will not plug up the pipe.
The engine to be used in connection with the boiler just described is shown in Fig. 53. This is a very simple engine of the oscillation type, and there should be little trouble in making it. A more mechanical drawing of the engine is shown in Fig. 54. The details of the engine are shown in Fig. 55.
The cylinder of the engine should be made first. This is made from a piece of brass tubing with an internal diameter of 3/4 inch. Two end pieces, or a cylinder-end cover and cylinder head, must be cut to fit inside the cylinder. These should be cut to shape from 1/16 inch brass, and a hole drilled in the cylinder head 1/8 inch in diameter to accommodate the piston-rod. The cylinder head is then soldered in place. The cylinder-end cover should be left until the piston-rod and piston are made.
The piston head is cut to shape from a piece of 3/16-inch sheet brass, or it can be cut from a piece of 3/4-inch round brass with a hacksaw. The piston-rod is soldered into a hole in the piston-head. A small square piece of brass is placed on the opposite end of the piston-rod to act as a bearing. This little piece is cut and drilled as shown in the drawing. Before it is soldered in place on the piston-rod the cylinder-end cover should be placed on the rod. Both the piston and the cylinder-end cover can then be placed inside the cylinder, and the piston-end cover is soldered in place. Before final assembling the piston should be made to fit nicely into the cylinder. This can be brought about by applying emery cloth to the piston-head until it slips nicely into the cylinder with little or no play. Thus a steam-tight fit is made, and this contributes greatly to the efficiency and power of the engine.
The cylinder blocks are shown in Fig. 55. These are cut and brought to shape with a hacksaw and file. With a half-round file one side of one of the blocks is filed slightly concave, so that it will fit on the outside of the cylinder. Two 1/8-inch holes are drilled in this piece as shown in the drawing. The hole at the top is the steam entrance and exhaust for the engine; that is, when the cylinder is at one side steam enters this hole, and when the crank throws the cylinder over to the other side steam leaves through the same hole after having expanded in the cylinder. This cylinder block is soldered to the piston as shown in Fig. 56. The pivot upon which the cylinder swings is then put in place in the hole at the bottom of the block. Solder is flowed around the pivot to hold it securely in place.
The second cylinder block is now finished according to the drawing. This has two holes 1/8 inch in diameter bored in it. One of these holes is the steam inlet and the other the exhaust. When the cylinder is at one side of its stroke the hole that was bored in the top of the steam block which was soldered on the cylinder is in line with the inlet hole in the block under consideration. Steam then enters the cylinder and forces the piston down. This turns the crank around, and the crank in turn pulls the piston over to the opposite side, so that the hole in the first piston block of the cylinder now comes in line with the exhaust hole on the second cylinder block. The steam in the cylinder escapes and the same operation is repeated over again. Of course, it must be understood that this steam admission and exhaust takes place very rapidly. The hole in the second cylinder block, which goes over the pivot, must be made a trifle more than 1/8 inch in diameter, so that it will slide freely over the pivot.
The engine is mounted on a very simple frame, which is a piece of 1/16-inch brass cut and bent as illustrated. After it is cut and bent to shape the second cylinder block is soldered in place. The cylinder can then be mounted. It will be seen that the pivot goes through both the second cylinder block and the engine standard. A small spring is placed over the protruding end of the pivot and a nut put in place. By turning this nut the pressure on the face of the two cylinder blocks can be adjusted, and the model engineer must always remember that the pressure on these springs must be greater than the steam pressure in the feed-pipe. Otherwise the steam pressure will force the cylinder-block faces apart and steam leakage will result. On the other hand, the pressure of the spring should not be too great, since that would interfere with the free movement of the engine cylinder.
Nothing now remains to be made except the crank and the flywheel. The crank revolves in a small brass bearing which is soldered in place on the engine standard. It will be seen that the sheet brass that makes up the engine standard is not thick enough to offer a good bearing for the crank. The crank is bent to shape from a piece of 1/8-inch brass rod, and the author advises the builder to heat the brass rod red-hot while the bending is done. This will prevent it from fracturing, and will also permit a sharp bend to be made.
The flywheel is a circular piece of brass 1 inch in diameter. Its center is drilled out and it is soldered to the crank as illustrated in Fig. 54. Two other holes 1/8 inch in diameter are drilled in the flywheel as illustrated, and two small brass pins are cut out from 1/8-inch brass rod and forced into these holes and then soldered. These provide a method of driving the propeller-shaft that is shown very clearly at Fig. 57.
The steam feed-pipe that runs from the boiler to the engine can be of small copper tubing. It may be necessary to mount the engine on a small block, as shown in Fig. 53. After the steam in the boiler has reached a sufficient pressure the engine crank should be given a couple of twists in order to start it. Before operating the engine a little lubricating oil should be run into the cylinder through the inlet or exhaust ports. The cylinder should always be kept well lubricated. The contacting faces of the cylinder blocks should also be kept lubricated.
Caution. Always keep water in the boiler. Never permit it to run dry, as this would cause a boiler explosion. When the engine is started and cannot be made to run, take the burner from under the boiler so that steam will cease to be generated. With the safety-valve the model boat builder need have little fear of an explosion. Nevertheless the foregoing directions should be carefully adhered to.
AN ELECTRIC LAUNCH
THE little electric launch to be described is of very simple construction, and when finished it will provide the builder with a very shipshape little model from which he will be able to derive a good deal of pleasure. It has a speed of from 2-1/2 to 3 miles an hour when equipped with dry batteries or storage batteries. The hull is of the Sharpie type, and this offers very little trouble in cutting out and assembling.
The general appearance of the boat and hull will be gathered from the drawings. The pieces necessary to assemble the hull are shown in Fig. 58. Only five pieces are necessary: two side pieces, a stern piece, a bow piece, and a bottom piece. The length of the boat over all is 40 inches with a 7-inch beam. The widest part of the boat is 1 foot 10 inches from the bow.
After the pieces that form the hull are cut they are thoroughly sandpapered to produce a smooth surface. The heavy imperfections in the wood can be taken out with coarse paper, and the finishing can be done with a finer paper. It is understood that sandpapering should always be done with the grain, never across the grain. The sides of the boat are cut about 1/4 inch thick, but they are planed thinner in places where the bend is most pronounced. The side pieces are 2-3/4 inches deep at the stern and 2-1/4 inches at the stern. There is a gradual curve from the bow to the stern, which is more marked toward the head.
The stern piece is thicker than the side pieces, being made of 1/2-inch wood. It is cut to the shape shown at Fig. 58, and beveled along the bottom edge to enable it to be fixed on the slant. The bow piece is a triangle 2-3/4 inches in length.
After the parts are thoroughly finished with sandpaper the stern piece is fixed in position. In making all the joints on the boat the builder should see that plenty of fairly thick paint is run in while the joint is being screwed up. This will help greatly in making the boat water-tight. Plenty of 3/4-inch brass wood-screws are used in assembling the hull. All the holes for the wood-screws should be countersunk so that the heads will come flush with the surface of the hull. Now one of the sides should be screwed to the stern piece, at the same time bending the bottom and side to meet. This is done gradually, inch by inch, and screws are put in place at equal distances. When the bow is reached, the side piece is beveled to fit the bow piece, which should already have been screwed into place. The other side of the boat is treated in a similar manner, and the young worker should take care to keep the side and bow piece perfectly square and upright. This may sound easy on paper, but it will be found that a good deal of care must be exercised to produce this result.
After the hull has been assembled it is given a good coat of paint inside and out. When the first coat is dry the holes left by the screw-heads are carefully puttied over, and the hull is given a second coat of paint. This procedure will produce a perfectly water-tight hull.
The stern tube is 3/8 inch, outside diameter. A hole is bored in the bottom of the boat to receive the stern tube. This job must be done cautiously; otherwise the bottom of the boat may be ruined. It is best to screw a substantial block to the inside of the boat. This block should be cut to fit the bottom and will act as a support for drilling. It will also help greatly to make a water-tight joint around the tube. The distance from the point where the stern tube passes through the bottom to the stern should be about 12-1/2 inches. The stern tube should be mounted as nearly parallel with the bottom as possible, since on this depends the speed of the boat. As the angle of the propeller-shaft increases, the speed of the boat will decrease. In drilling the hole the boat-builder should be careful to keep the drill running along the central line of the boat.
As before mentioned, the stern tube is a piece of brass tubing 3/8 inch in diameter and 8 inches long. It is filed square at both ends, and a brass plug is fastened with solder in each end. The tube is then filled with melted vaseline, which is allowed to cool. The hole in the hull around the tube is then well smeared with thick paint. When this is done, a layer of red lead or putty is placed around the joint both on the inside and the outside of the boat.
While the putty is drying the spray-hood or turtle-deck can be made. This is bent to shape from a piece of tinplate and extends half way down the boat. When the turtle-deck is finished, it is best to lay it aside, before finally fastening it in place, until the entire boat is completed.
The wooden part of the deck is made of 1/8-inch wood and scribed with a sharp knife to represent planking. This method of producing planking was described in detail in Chapter II.
Toward the stern of the boat and just behind the motor a hatchway is fitted to give access to the batteries and starting switch.
The finished Sharpie hull without its driving batteries or motor should weigh about 1 pound 3 ounces. The hull being finished, let us consider the electric propelling equipment.
A 1/8-inch cold-rolled steel driving or propeller-shaft is used. The shaft is 13 inches long and a gear-wheel 1 inch in diameter is fixed to one end of this shaft. This gear-wheel meshes with a brass pinion on the motor-shaft. This forms a 3-1/2 to 1 reduction gear, which produces a greatly increased speed of the boat. The other end of the propeller-shaft rests in the skeg bearing. In this present case this consists of a tube about 1/2 inch long, which is made for a revolving fit on the propeller-shaft and supported by a sheet-metal bracket. This is shown in Fig. 63. The end of the propeller also revolves adjacent to the bearing in the skeg.
The propeller is a three-blade affair with a diameter of 2-1/4 inches. It is attached to the propeller-shaft with a set-screw. The motor is a very simple type obtainable in the open market. It is similar to one shown in Fig. 41. As before mentioned, either dry or storage batteries may be used as a source of current. The writer strongly advises the use of storage batteries if possible. The initial cost of these batteries is greater than that for dry batteries; but, on the other hand, the small storage battery can be charged repeatedly and will outlast many dry batteries. If the boat is used much the storage battery will probably be the more economical of the two.
The steering gear of the boat is very simple. The rudder works in a bearing that is screwed to the stern piece. The end of the rudder-shaft is tapped, and a brass screw is used to clamp it in position after setting it with the fingers. The rudder-shaft is a 3/4-inch brass rod. The lower end of this rod is slit with a hacksaw and the rudder is placed in this. Solder is then flowed along the joint.
Of course, the builder may paint his boat whatever color he may select; but a maroon hull with a white-enameled spray-hood or turtle-deck makes a very pleasing combination. Fig. 60 shows a rough plan of the general arrangement of the power machinery. Figs. 61, 62 and 63 will do much to give the reader a clear idea of the method of construction which could not be gained by reading a description.
The general appearance of the boat can be improved materially in many ways. For instance, a little stack or ventilator may be added to the turtle-deck, and a little flag-stick carrying a tiny flag may be placed on the bow and on the stern.
The motor current should be turned on only when necessary, for dry-cells deteriorate rapidly when in use, and small storage batteries quickly lose their charge, although they will last much longer than dry-cells and give much better service.
A STEAM LAUNCH
THE steam launch Nancy Lee is an attractive little craft when finished and it is capable of attaining considerable speed. It is really designed after the cruising type of motor-boats. This type of boat is particularly adaptable for simple model-making, owing to the elimination of awkward fittings. The power machinery is of very simple construction and presents no real difficulty.
The following materials are necessary to construct the Nancy Lee:
Large wood block for hull. Thin white pine for deck, etc. Sheet-metal tube, rod and wire for the boiler, engine, etc. Lamp-wick, paint, screws, and brads Miscellaneous fittings
The actual expense necessary to construct the boat is very small.
Having obtained the block for the hull, you are ready to start work. The hull, when planed on all sides, should be 30 inches long, 6-1/2 inches wide, and 3-3/4 inches deep. A center line is drawn down the length of the hull, and five cross-section lines are drawn at right angles to the center line 5 inches apart. On these lines the builder should mark off the greatest lengths of the boat, taking the dimensions from the half-breadth drawing shown in Fig. 64. It will be noted that the deck is wider than the L. W. L. forward and narrower than the L. W. L. at the stern. The block should be cut to the widest line on the half-breadth part.
The half-widths in Fig. 64 are drawn each side of the center line on the block. The block will be cut out to this line and planed up as true as possible. The builder should then project the section lines with a set square on each side of the boat, mark off the profile from the sheer plan, Fig. 65, and cut the block to this line, afterward planing it up true.
The blocks should now appear as sketched in Fig. 66. It is now ready for the shaping of its exterior. A plane, a chisel, and a draw-knife are the only tools necessary to bring the hull to the correct shape. The cardboard templates must be cut, one for each half-section, as shown in the body plan, Fig. 67. These templates serve to show the proper outside shape of the hull. The block for the hull must be cut away until each one of these templates fits properly into place. The various stages are indicated in Figs. 68 and 69.
The interior of the board is gouged out with a gouging chisel, and if the builder desires a uniform result he should make inside templates. In gouging out the interior of the hull the chisel or gouge should be handled very carefully; otherwise it is liable to slip and spoil the entire hull.
The next job is to cut and properly fit the raised portion or forecastle. A piece of wood 1-1/4 inches thick, 15 inches long, and 6-1/4 inches wide must be prepared and laid in place on the hull. The shape of the hull is marked off with a pencil and the wood sawed along this line. The inner portion is also cut out, thus making a V-shaped piece which must be glued and screwed in place, as shown in Fig. 70.
The oval air-vents shown in the drawing can be cut at this time. The hull is neatly finished by cutting in the sheer or curvature of the hull and sandpapering it all over. A cross-beam or support, C, Fig. 70, is cut and fitted as illustrated. This particular piece supports the fore-deck, and also carries the main-deck, as well as bracing the boat together. This piece should be 3/16 inch thick and cut from solid oak.
The decks can be made of a good quality of white pine. The builder should select clean pieces, free from knots and blemishes. It only requires to be cut to shape and then fixed to the hull with a few brads. The edge should be cleaned up flush with the hull by the aid of a plane. The opening for the cock-pit, shown in the drawing in Fig. 71, is to be cut in the deck. The coamings and seats are cut to the sizes indicated in the drawings. They are then glued and pinned together. When fitted to the deck the result will be somewhat as shown in Fig. 71.
The fore-deck is prepared in a similar manner; but, since this is to be removable, two battens must be fitted to the under side to keep it in place. The openings for the hatchways can be cut and the hatch-covers made by cutting another piece of wood 3/16 inch thick to form an edging. A cover piece to go over the small pieces, removed from cutting out the hatch opening, is shown at Fig. 72. A coping-saw will be found very useful for this work. The covers are neatly rounded on the edge and nicely finished.
Fig. 73 will give the reader a very good idea of the appearance of the boat at this stage. It will be seen that the sketch shows the deck broken away so as to render the cross-batten visible, which also shows the fair-lead at F, Fig. 73. This is cut from two small pieces of 3/16-inch stuff, glued and pinned in place. The forward deck is completed by the addition of cowl-ventilators, cut from hard wood and screwed in place. The flag-mast is made from a short piece of 1/16-inch wire. The details of the mooring-cleats are shown in Fig. 74. They are fashioned by using a small screw-eye and soldering a short piece of brass wire through the eye. An oblong metal plate is then cut and a central hole drilled. This plate is soldered to the shank of the screw-eye and the cleat is complete. One of these devices is to be fitted to the fore-deck and two on the main-deck and stern.
The rudder and steering gear will be considered next. Fig. 75 shows the stern of the boat with the rudder gear mounted in place. It will be noted that the rudder-blade is merely a piece of sheet brass cut to shape and soldered into the rudder-post M, which is slit to accommodate it. The rudder-post is hung in two screw-eyes on the stern of the boat. A small wheel about 1 inch in diameter, with an edge filed in it, is soldered to the top of the rudder-post. A fine cord or string, well stretched and oiled, is attached to the wheel and led through two screw-eyes on the deck. From this it is led through an opening in the coaming to a drum on the steering column, which is turned by another small wheel similar to that used on the rudder-post, but with a round edge. The steering column is merely a piece of 1/8-inch wire, held in place by two small screw-eyes fixed in the coaming and with a tube-brush soldered on to keep the wire in position. The drum is simply a hard-wood bushing driven tightly in place.
The power machinery for the Nancy Lee must be considered at this time. This is really one of the most interesting parts of the construction. The general appearance of the power plant can be seen by referring to Fig. 77, which is a view of the complete boiler and engine mounted together on the same base. The boiler is shown at A and the safety-valve and filler at L. The base or firebox B protects the burner from stray drafts of air, and also supports the boiler.
The lamp or burner consists of a receptacle C for containing the denatured alcohol. The denatured alcohol is inserted through the filler-tube E, which is kept closed with a cork. The upright tube D is fitted so that air can go into the receptacle containing the alcohol. Three burners are necessary to fire the boiler. These are fitted as shown in F, and they give sufficient heat to produce steam enough to drive the cylinder G. The steam is conducted to the cylinder through the short pipe K. The steam-cylinder has the usual piston and rod, which drives the circular crank H. This crank is mounted on a crankshaft carried on the metal tube M. As will be noticed, the cylinder is of the simple oscillating type mounted on a standard, formed as part of the boiler casing, and stiffened by two angle-plates L.
A heavy flywheel, J, is now fitted to the inside end of the crankshaft. This wheel should be a lead casting, and as heavy as possible. A heavy flywheel contributes much to the operating efficiency of the engine. The propeller-shaft and crank are shown at N in the insert.
The boiler is made from a strong tin can about 1-3/4 inches in diameter and 4-1/2 inches long. It is cleaned inside and out, and all the seams are double-soldered. The lid is also soldered on the can. This little boiler, although not elaborately made, will be found capable of standing up under considerable steam-pressure, and so no fear need be had of accidents by explosion.
A little safety-valve and filler-plug suitable for use on the boiler are shown clearly in Fig. 78. A piece of sheet tin is cut out to the size and shape illustrated in Fig. 79 at A. The piece is bent up at the dotted lines and the seams are soldered. Two angle-plates, B, are then cut and fitted and soldered in place. Next a piece of brass tube with a 1/8-inch bore and 1 inch long is cut and soldered in place for the bearing of the crankshaft. A lead flywheel 1-1/4 inches in diameter and 1/2 inch thick is then mounted firmly on a piece of straight steel wire 1-3/4 inches long, which acts as a shaft.
The shaft is made to run freely in the crankshaft bearing that was previously soldered in place. The cylinder is shown in section in Fig. 80. If the reader will refer back to the construction of the engine described in Chapter 4 he will readily understand the operation and construction of this particular engine.
A little crank must be cut from 1/16-inch brass, and soldered to the crankshaft after fitting a wire crank-pin to the outer edge. This crank-pin should be of such a size that the joint on the end of the piston-rod shown at A, Fig. 80, turns on it easily. The throw should be only half the stroke of the engine, which is 3/8 of an inch.
The boiler is now fixed in place by bending the lugs B, Fig. 79, so that they just support the boiler nicely. They are then soldered in place. Next fit the short steam-pipe K between the boiler and the steam block on the cylinder. The builder should take care to keep the steam-pipe well up to the top of the boiler.
The lamp should be built at this time. The container for the denatured alcohol is made from a well soldered tin box of suitable size. It can also be made by cutting a sheet of tin to the size and shape shown in Fig. 81. The corner joints are soldered and then a tin lid is soldered in place. The builder should not forget to make the filler-tube E and air-tube D, as shown in Fig. 77, before soldering the top piece in place. The burners should be made as high as the container, and these should be made from little pieces of tin bent to shape and soldered on to a bottom pipe, as shown in Fig. 77. The builder should also remember to cut the holes through this pipe so that the alcohol can get into the burner-tubes, and also to solder the open end of the bottom or feed tube. Before the wicks are put into the lamps, the container should be tested by filling it with alcohol to see that it is perfectly tight at all joints. If it is not the container should be gone over again with solder to assure its being leak-proof.
Before operating the engine with steam, it can be tested with a small bicycle pump through the opening for the safety-valve. The engine should turn over briskly at every stroke of the pump, providing it does not come to rest at "dead center." If it does come to rest at "dead center," where no air can enter the piston, the crankshaft should be given a little twist and the engine will then start. Before steam is applied it will be well to experiment until the engine runs with the air-pump.
Having made the engine run smoothly with air, steam can be generated in the boiler. The wicks should not be placed too tightly in the burners. After they are in place the container may be filled with denatured alcohol, and the burners lighted and placed under the boiler. In a very few minutes steam will be up. At the first indication of pressure in the boiler the engine should be given a twist with the fingers until it starts and goes of its own accord. The constructor should remember to keep his engine well lubricated.
The propeller-shaft is merely a piece of steel wire, perfectly straight and fitted with a crank A, Fig. 82. This crank is similar to the one fitted to the engine, but with a small slot cut out for the crank-pin to fit into. This is done so that, as the crank-pin on the engine turns around, it also turns a slotted crank on the propeller-shaft.
A short piece of tube, C, is now fitted to a flat brass plate, D. The plate is mounted at an angle to the tube, so that when it is in place on the stern of the boat the propeller-shaft will be in line with the crankshaft of the engine.
A clearance hole is now drilled through the hull, so that the propeller-shaft can be put in place. Solder the tube to the plate, and punch four small holes in the plate, so that it can be screwed firmly to the hull. Solder a short piece of tube, as shown at B, Fig. 82, to keep the propeller-shaft in position.
The propeller must now be made. This is easily done by cutting out a disk of brass 1-1/2 inches in diameter, as shown in Fig. 83. The shaded portions of the brass disk are cut away. The blades are bent to shape, care being taken to see that they are all alike. This done, the propeller is soldered to the propeller-shaft.
The only part of the job that remains is to screw the boiler in place under the fore-deck of the boat. This done, the Nancy Lee is ready for her trial. The fore-deck should be made removable by fitting it with pins or screws with the heads cut off, so that the deck only needs pushing into place. This little boat should be capable of attaining a speed of from four to five miles an hour if it is made carefully and according to the directions outlined in this Chapter.
AN ELECTRICALLY DRIVEN LAKE FREIGHTER
A PROTOTYPE of the model lake freighter described in this Chapter will probably be familiar to many readers. It is a type of boat used on the Great Lakes, and, owing to its peculiarity of design, it lends itself very well to construction in model form.
The lines of the boat may be seen very clearly in Fig. 84.
The hull of the model freighter measures four feet over all, and the beam at the water-line is 8 inches. The extreme draft will be in the neighborhood of 5 inches. This model, when completed, will be capable of carrying considerable weight; in fact, it is able to accommodate thirty-five pounds in weight when used in fresh water. This will give the builder an opportunity to install a very substantial power equipment with little regard for weight.
The hull is made according to the built-up principle, and the constructor will have to cut his templates before attempting the shaping of the hull. Owing to the depth of the model, it will be necessary to use about ten planks. The plank that is used to form the bottom of the boat is not gouged out. Every other plank is gouged out with a saw and chisel.
The bottom plank is shaped with a knife to conform to the lines of the boat. In building up the hull with the planks, they should first be smeared with glue, and when put in place a few brass brads should be driven in. As mentioned in an earlier part of this book, iron nails should not be used in work of this nature, owing to the fact that they will rust and cause trouble. The brass brads are placed about one inch apart the entire length of the boards. The hull is finished with a plane and sandpaper, and after it has been brought to shape in this way and finished, a coat of paint is applied. Black with dark red trimmings makes a very good combination for a boat of this type.
The deck is made from a piece of 1/4-inch pine board. Seven hatches are added to the deck. Six of these hatches can be made by merely gluing a square piece of 1/4-inch wood to the deck. The seventh hatch should be made with a hole cut in the deck, so that access can be had to the power motor.
The deck-house, wheel-house, and chart-house, as well as the bridge, should be constructed of tin, which may be salvaged from clean tin cans. The bridge is provided with spray-cloths made from white adhesive tape, as outlined in Chapter 9. The port-holes in the deck-house and hull are made by little pieces of brass forced in place over a small piece of mica. The life-boats, which are carried on top of the engine-house, are whittled out of a solid piece of wood and painted white. Life-boats are always painted white, regardless of the color of the boat upon which they are used. The life-boats are held by means of string and small dummy pulleys to davits made of heavy stovepipe wire. A rub-streak made of a piece of 1/4-inch square pine is tacked to each side of the hull just below the sheer-line. The rub-streak should be tacked in place with nails such as those used on cigar-boxes.
The funnel measures 1 inch in diameter by 4 inches long. A small exhaust steam pipe, which can be made from a piece of brass tubing, is mounted directly aft of the funnel. The forward deck fittings consist mainly of a steering-boom, two bollards, two fair-heads, and four life-buoys mounted on the bridge. The main-deck is equipped with six bollards and two covered ventilators, each 1/2 inch in diameter. The foremast is properly stayed in the deck, and should be fitted with rat-lines. The rat-lines can be made with black thread and finished with varnish, which when dry will tend to hold the threads in shape.
The rudder is cut from a piece of sheet brass to the shape shown, and fitted with a quadrant. The engine cabin can be made from cigar-box wood. The windows and doors can either be painted in place, or the windows can be cut and backed up with sheet celluloid. A good substitute for painted doors will be found in small pieces of tin painted a different color from the cabin. The same procedure may be followed in fitting the windows and doors to the forward cabin.
We are now ready to consider the power plant. Owing to the large displacement of the boat, it will carry a fairly heavy storage battery. The electric motor and storage battery are mounted in the manner shown in Fig. 85, which will also give the reader an idea of the appearance of the finished model. As the drawing indicates, it will not be necessary to tilt the motor to any great degree in order to bring the propeller to the proper depth. This is because of the depth of the boat. Instead of a string or belt to connect the motor with the propeller, the shaft of the motor is taken out and replaced by a longer steel rod that will serve both as a motor-shaft and a propeller-shaft. The propeller-shaft extends from the motor through the stern-tube. The propeller used for this model is a three-blade affair, 3 inches in diameter. It must be of this size in order to propel a boat of these dimensions at a consistent speed.
Care must be taken in mounting the motor in this way. If it is not mounted directly in line with the stern-tube the propeller-shaft will have a tendency to bind. However, with a little care no trouble should be experienced from this source. The storage battery used should be of the four-volt forty-ampere hour variety. This boat will be capable of carrying such a battery and this weight should just bring the craft down to her load water-line. The whole deck is made removable, so that the storage battery can be taken in and out at times when it is necessary to recharge it. A battery of this capacity, however, will drive a small motor similar to the type used on the boat for some time.
AN ELECTRIC SUBMARINE-CHASER
THE submarine chaser design given in the drawings and described in the text of this Chapter is a presentable little boat with pleasing lines and deck fittings. There is nothing difficult about its construction, and, considering the amount of work necessary to produce it, it is probably one of the most pleasing boats described in the book. If made correctly it will look "speedy" and shipshape.
The general outline of the boat can be gathered from Figs. 86, 87, and 88. Fig. 86 gives a side view of the craft; Fig. 87 shows the bow, while Fig. 88 gives the deck-plan.
Notice first the construction of the hull. This is made according to the Sharpie type, but the lines are changed to give the boat a more graceful appearance. This is done by changing the shape of the deck and the bottom pieces. Fig. 89 shows the various pieces necessary to construct the hull. It will be seen that the forward portion of the bottom piece is narrower than the deck piece, and broadens out so that it is wider at the stern than the deck piece. The deck piece has a maximum width of 5 inches, while the bottom piece has a width of 4 inches at the forward section. The deck measures 3-1/2 inches at the stern, while the bottom piece measures 4-1/2 inches at the stern. This produces a half-inch taper on each side of the stern. A half-inch taper is also produced on the bow portion.
The hull of the boat can be made from 1/8-inch mahogany. If this is not available, choose some other close-grained wood, free from knots and blemishes. Paper patterns are made to correspond with the general shape of the pieces that form the hull as given in Fig. 89. The pieces, after being marked, are cut to shape with a keyhole-saw. After this is done their edges should be trimmed neatly with a jack-plane.
The two sides pieces are now screwed to the bow piece by small brass screws. After this is done the bottom piece is fastened to the side pieces the entire length of the boat. Next the first cross-piece, as shown in Fig. 90, is screwed in place. This cross-piece should be 4-3/4 inches in length, so that the width of the hull at this point is just 5 inches. The next cross-piece should correspond to the width of the deck piece at the section of the hull where it is placed. The same holds true for the third cross-piece. When the third cross-piece has been screwed in place, the stern piece is put in position.
The joints of the hull should then be smeared with either pitch or bath-tub enamel or a thick mixture of white lead may be used.
After having made sure that the hull is perfectly water-tight the worker can proceed to install the power equipment. This consists of a small battery motor driven with two dry cells. The design and installation of such things as stern-tubes and propeller-shafts have been taken up in detail in an earlier part of this book. The strut that holds the propeller-shaft is shown in Fig. 91. This consists merely of a brass bushing held in a bracket made of a strip of brass 1/2 inch wide. The brass strip is wound around the bushing and soldered. It is held to the bottom of the hull by means of two 8-32 brass machine screws. These screws should be tightened to prevent leakage. It would be inadvisable to use wood-screws for this purpose, owing to the fact that the bottom piece of the boat is thin.