Читать книгу Boys' Book of Model Boats - Raymond F. Yates - Страница 8

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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.