CHAPTER XXIII

KITES, GLIDERS, AND AEROPLANES

=Kites.= Perhaps one of the easiest kites to make is one which the children of Annam and Tonking delight to play with. To make it, three light bamboo canes are required--about 2 feet in length--those used for flower-sticks will do quite well. Tie them strongly together as in Fig. 467.

The backbone E F should be quite rigid, but the cross-pieces A B and C D are better if they are slightly curved. A sheet of light paper must now be pasted from A B to C D underneath E F in such a way that it is quite tight under E F, but rather loose between A C and B D.

Fig. 468 shows how the paper should be cut. G H is the exact distance between E and F; J K and L M are wider than distances between A C and B D in Fig. 467, so that when the flaps on the paper are pasted over the cross-bits the paper is loose between A and C and between B and D (Fig. 467). The secret of the balance is to have the flutter at the edges quite equal. Fig. 467 shows how the string is fastened.

=A Box Kite.= This is a very common form of kite and quite easy to make. Take four laths from 27 to 30 inches in length and four pieces about 13 inches in length. The smaller pieces are fastened together with nails and glue, as in Fig. 470 (_a_) and (_b_). To the ends of these the long pieces are nailed and glued, as in Fig. 470 (_b_). Mark off the long pieces into thirds and over the two end thirds sew strips of light material. Tie on the string as shown in Fig. 469. This kite is said to be an American invention.

A similar kite may be made triangular in form.

Fig. 471 shows another form of the box kite. Here the material covers a little less than 1/4 of the strip A B. Cross-bars E F and C D are tied across the middle and to the four sides, and wings are sewn on to them.

Figs. 472 and 473 are modifications of the triangular form of kite. In both these kites the long strips of wood are from 2-1/2 to 3 feet in length.

Notice that in Fig. 472, A B is the same length as D E, F G = D H; E H = about 1/4 of E D.

In Fig. 473 A B = C D. C E = about 1/4 of C D. F G equal about 1/3 of A B. F C = C E. A H and J K are light frames of stripwood covered with calico. The diagrams show how these kites are put together.

=A Chinese Kite.= The kites used in China are very light and flimsy compared to our kites, as they are made of tissue paper and bamboo.

In making one it is better to use somewhat stronger paper. The paper is cut out as in Fig. 474, the two upper sides being slightly shorter than the two lower. Leave two rectangular pieces A, A, at each end of the shorter sides. A piece of split bamboo, slightly flattened, is glued firmly to the paper from B to C. A second piece of bamboo tapering at the ends is used as a cross-piece D. This is bent as in the figure so that where it crosses the backbone, B C, it is only a few inches from the apex, B. It is tied to B C at D. Its tapering ends are pasted down to the paper by means of the two flaps, A, A. Bamboo B C should not be more than 1/3 inch in width, piece D, 1/4 inch. To prevent the paper getting torn in a good breeze, tie fine cotton round the border of the kite--_i.e._ from B to A, to C, to A, and to B again. Paste a thin margin of paper over the cotton, enclosing it, and to the kite. This must be done so that the face of the kite is perfectly flat; it must not bag in any way.

=To fly the Kite.= Much depends on the way in which the 'belly-band' is tied on. Its upper string is tied to D, and the lower to the backbone, B C, almost anywhere below a line from A to A. If the two strings are very near together, the kite behaves in a more lively manner, darting about in all directions.

The kite must be coaxed into the air by a series of jerks and pulls when the apex of the kite is facing upwards. It is inclined to turn round at first and some patience is required to learn when to pull and when to jerk. If one pulls at the wrong time it will dart down and then unless sufficient string is quickly let out, it will fall to the ground.

When once the kite is up, it does not keep stationary like an English kite, but is always darting about; a skilful flyer can make a kite dart down and almost touch the roof of a house at a great distance off, and then dart up again almost overhead.

It is not an easy kite to manage, but when once the art of flying it is mastered it is never forgotten.

=Gliders.= The earliest type of toy flying-machine consisted of a two-bladed tin propeller spun on a frame by unwinding string, as with a top, and suddenly let go. It is easily made, as shown in Fig. 475, where A is a tin propeller nailed by nails C and C to a large reel B. In making this toy the nails must be driven into the reel first, their heads are then cut off and they are tightly fitted into holes in propeller A. D is the axle on which the reel spins and the handle for holding it; E is a washer. This flying-machine is worked by smartly pulling a length of string wound around the reel.

Modern aeroplanes are far more difficult to make than this; they need patience, skill and experiment, and besides a knowledge of how to twist and bend wood by steaming it; plenty of cane and whalebone wire, tissue paper or fine Japanese silk, and catapult elastic, which is generally the motive power used in working model aeroplanes. (Messrs Gamage, Holborn, W.C., stock skeins of specially prepared elastic.)

In this chapter only the simple and well-known types will be very briefly described, the boy who is interested must get special books on this subject from his library. In the first place the beginner must know what the three types of machines used in designing models generally are--viz. (1) the glider or motorless model, a glider being a winged structure, which when released from a height does not fall directly to the ground, but descends gracefully at a gentle slope; (2) the monoplane, which is constructed more or less on the lines of a bird; and (3) the biplane or double-winged aeroplane.

Gliders may be either of the monoplane or biplane type. Experiments with gliders will enable boys to find out some of the principles on which aeroplanes are built, and will prepare them to undertake the construction of more difficult forms.

In making one's first glider one cannot do better than copy a bird. On a piece of paper draw a circle, fold it in half, draw a bird on one half, as in Fig. 476, cut it out, when the paper is opened it will appear as in the figure. If this bird is thrown head first toward the ground, it will probably fall. If two little bits of cardboard are gummed on each side of his head, he will make a better flight and land on the ground after making a gentle curve. A still better bird may be cut from cardboard, a half cut is then made along _a b_ to bend it, and the head is weighted with sealing-wax. How well this bird flies depends on the weight, and to some extent on the shape of the bird. Birds of various shapes and with different amounts of sealing-wax should be tried, until one is made that glides to the ground in a long, graceful curve.

In making bird gliders the following points should be remembered:

(1) Draw the bird in a circle as already explained, this ensures that the wings will be exactly balanced.

(2) If the head in Fig. 476 is not long enough for a graceful flight, a longer head cut from cardboard can be pasted on.

(3) If the bird dives quickly down head first, you know that the head is too heavy, or the neck too long.

(4) If the bird rises and then falls the head is too light and probably not long enough.

(5) The wings can be made larger if necessary by the addition of tissue-paper wings gummed on as A in Fig. 477.

=Another Glider.= Cut out a piece of paper 8 inches by 4 inches, A B C D in Fig. 478. Mark B E and D F each 1 inch; make cuts along the dark lines at E and F to the depth of 1 inch. Draw the broken lines along the paper, dividing it into four equal strips. Bend sides A E and C F downward along dotted lines. Bend E B and F D upward along middle dotted lines, and press side C F toward side A E, part way along this line, but leaving the part near the ends A C flat; to this end plane K will be gummed (Fig. 479). K is 6 inches by 1 inch. Cut tail, G, and gum on as in diagrams. It can be weighted at H by gumming several strips of cardboard across or by affixing sealing-wax. Although this is not a very graceful-looking glider it works most successfully, and will describe quite a graceful curve toward the ground.

The child will find it interesting to make a number of these gliders and then go one day to a window or high place and let them glide to the ground and thus find out the bird that has the longest flight. Or a number of children can have glider races and see who can make a glider that alights on the ground farthest from them. Other forms of gliders can be made, but they are all on the same principle, a somewhat long body, wings and weight adjusted to keep them from falling.

Fig. 480 shows a glider made from a dowel rod, with slits in it at each end through which two cardboard planes are passed and fastened. The cardboard must be of light weight and yet stiff enough not to flap. The size of the planes must be found by experiment, for their size will depend naturally upon the weight of the material used. The bigger plane should be in length about twice the smaller one. It is best to fasten the large plane on first and then adjust the smaller one to give a long, graceful flight.

If a split pole can be found it is an easy matter to fasten the planes in. Canes (bamboo) split readily and can be used as centre pole.

This glider can fairly easily be made into an aeroplane and worked with a propeller. It may be mentioned here that model aeroplanes are generally worked with the propeller in front and not in the rear.

=To make Propellers.= These can be made of tin or wood. A tin propeller can be cut from any old tin with a pair of shears or strong scissors kept for the purpose. Cut two blades to the shape shown in Fig. 481.

Next cut an oblong block of wood (Fig. 482); notice that width _a b_ in Fig. 482 must equal _a b_ in Fig. 481, therefore width of _a b_ must be a little less than _a b_ in Fig. 481. Slit each end diagonally as in Fig. 482 for about 1/2 inch to hold the blades. Drill a hole through centre of block for the wire axle _d c_. Insert the blades in the slots, bend the ends over slightly and nail them in the wood to keep them firm. Fix the wire shaft firmly in the block as in Fig. 482. The propeller is now ready to be attached to the glider.

Before this is done, however, we shall consider the making of a wooden propeller. This is rather more difficult to make. Cut a piece of wood to the shape shown in Fig. 483 with a sharp pen-knife. The propeller must then be given the correct twist by means of the steaming kettle. Take hold of the extreme ends of the propeller and hold it over the jet of steam so that steam plays upon the blades at each side of the thick central portion.

When the wood is supple, twist it as in Fig. 484. This sounds easier to do than it really is, the difficulty being to get the twist on one side exactly equal to the twist on the other. For this reason the tin propellers are more satisfactory to make. However suppose the correct twist has been given, the next thing to do is to sand-paper the wooden propeller carefully and file a groove around the middle at A; now wrap a piece of wire, A C, tightly around the propeller in this central groove, and put on the head, B. The propeller is now ready to be fastened to the glider shown in Fig. 480.

=To fasten Propeller to Glider.= Cut a piece of tin to the pattern shown in Fig. 485, bend along the dotted line; make a hole at F for axle, B C, to go through. Bend portion E round the front end of the glider, keep it in its place by bending it with thread coated with glue; portion F with the hole is bent down at right angles as shown in Fig. 486. Now pass axle, A C, through hole F, bend end C into a hook. Put screw-eye D in the rod about one-third of length of rod from the other end (see Fig. 486). Fasten strands of elastic from hook C to D. It is best really to have a hook at D so that the elastic can be slipped over. The strands should be just loose enough to remain taut when unwound. When the propeller is in position the planes will probably have to be readjusted. The tin propeller can be attached in a similar way. These propellers will do for almost any simple design of aeroplanes.

When the motor is wound up for flight, the number of turns to give to the propeller will depend upon the strength and number of the elastic strands used. About a hundred turns is a usual number. Throw the motor forward in a slightly downward direction; because it is a glider it will tend to follow a gentle curve to the ground at first, but the whirling propeller will tend to carry it forward and upward. The first attempts may be failures, but these models are well worth many trials.

=The Hawk Aeroplane= (Fig. 487) is a common flying toy worked as the above by elastic. Cut two blocks of wood, A, A´; make holes in them as shown. Into the square holes fix and glue two square rods C. Through A´ bore a hole for the piece of cane, B B´, to pass through. F is a wire spindle with a hook at one end for elastic; it passes through the hole in block A´, through two beads, and through a piece of cork, F, into which it must be fixed. K is a piece of cane bent as in diagram, passing through a hole in cork, H. The bend is more _permanent_ if the cane is held to the spout of a boiling kettle; the ends of K should be slightly warped in opposite directions. Into block A another wire hook is fixed and bands of elastic are passed over this hook and the opposite one, as in the diagram; the more bands the better.

The cane B B´ is bent round at each end and fastened to the wooden rods, C C, by thread. The cane, K K, is fastened by thread as in the diagram; the thread can pass through a hole in the cork. Spaces T, T, T, T are covered with thin tissue paper gummed to thread and cane by means of overlapping edges. The model is wound up and set going like the previous one. Care must be taken to have it properly balanced, and it must be made as light as possible; the blocks A, A´ may very well be cut from cork. Light bamboo cane can be used for posts, C C. At its best, however, the Hawk Aeroplane is not so good a flyer as the first model described.

An ambitious and clever boy who has once grasped the principles on which flying-machines are made can think out many models for himself and copy some of the more elaborate ones. The biplane makes a very effective toy, but is omitted here because it is somewhat difficult to construct.