Читать книгу Carpentry and Woodwork - Edwin W. Foster - Страница 15

Table of Contents

Making and experimenting with aeroplanes calls for much patience and often ends in disappointment—the lot of inventors generally. This is no reason why work should stop, as all progress is made by attempting the supposedly impossible, but it will be restful after a while to turn to the ancient and gentle art of kite making.

Incidentally, something may be learned about the effect of wind on plane surfaces that will prove helpful in aeroplane work.

The aeroplane kite shown in Fig. 50 is simple and effective. It may be given the appearance of a Blériot monoplane by modifying some of its features, as shown at b, the planes having a slight upward slant. The arrangement of the frames is clearly shown in the drawing. Spruce or white pine may be used, as lightness is an essential.

The method of fastening the sticks is important. It is not wise to halve them, as their strength will be reduced below the safety point, and nails are likely to split them. Bind them securely with strong linen kite cord or fine soft wire.

Kite a is open to criticism on account of the single stick connecting front and back. The second form is better, and the two long sticks may be correspondingly lighter without reducing the ultimate strength of the frame. The method of joining three sticks, as at the forward end, is shown in detail in Fig. 50. Wherever a butt joint occurs, join the two pieces by means of small strips of tin cut to size with a pair of tinsmith snips. Drill holes through tin and sticks, pass fine soft wire through the hole, and twist tightly with a pair of pliers.

The planes or sails may be of light, strong paper, or some light fabric, such as lawn or cheap silk. The fabric should be cut to size, allowing two inches each way for the hem. Pieces of cord are fastened to the hem, and tied to the ends of the sticks through small holes drilled for the purpose, or tied to notches cut with the knife.

The advantage of this method is that the sails, or planes, may be drawn tightly or removed without loss of time. In this way a number of fabrics can be used for experimental purposes. Paper, on the other hand, must be lapped over sticks and wires, and glued.

Propellers may be fastened to front, rear, or both, to create the appearance of a real aeroplane.

The restraining action of the cord holding one of these kites up against the wind brings into action the same force that supports the glider or aeroplane, and the sails, especially fabrics, assume the curve of a boat sail, when close-hauled and sailing into the wind.

The forms that are possible are infinite, and limited only by the imagination of the designer.

It is well to begin with one of the standard types, and leave experimental forms until some experience has been gained.

The Americanized Malay, Eddy, or parakite is shown in Fig. 50. The two sticks are of equal length, bound together with twine or soft wire. Distance c e should be from 14 to 18 per cent. of the total length c d. The vertical stick remains straight, but cross stick a b is bent back like a bow, the distance e f being 10 per cent. of the total length of either stick, and maintained by a string from a to b. The four points a c b d are joined by a cord drawn taut, to make sure that the sticks are at right angles.

Fig. 50.

The material should be cut as shown, the amount lapped being uniform all around. This is important, as a slight difference in weight between the two sides would result in erratic flying. For Eddy kites up to three feet in height a light-weight wrapping paper will answer very well. Larger sizes require nainsook, lawn, or China silk. Like all the kites described here, this is a tailless one, and the method of fastening the bridle is shown. Make a small hole in the covering, pass a cord through, and tie it to cross the stick at its centre. Fasten the other end about half an inch from lower end of upright, and make a loop at o for attaching the line.

The kite line should be the light and strong linen twine made especially for this purpose, and sold by toy and sporting goods dealers. A ball containing 600 yards of cord, strong enough to hold any three-foot kite, will cost about fifty cents.

For larger sizes, it pays to make a reel, to save time drawing in and to avoid bad tangles. A simple form of reel is shown in Fig. 51.

The frame has a generous-sized hole bored as shown at h. Cut a small branch in the form shown, i, and use this as a stake. Drive it into the ground through h, and use it as a pivot to shift the reel as the wind changes. With this arrangement the kite cannot drag the reel, and it is possible to leave the apparatus with the kite in the air. The writer was driven to using this device after seeing his reel go tearing across the fields until stopped by a four-foot fence. The pull exerted at the reel by a train of three or four kites is sometimes sufficient to give a boy all he can do to hold it. The height to which a kite will go is illustrated by the diagram. S is the starting point, and s t the direction of the string at the start, when but little cord has been played out. The position of the kite at various times is indicated by letters a b c d e, the actual path being shown by dotted line. The solid, curved lines from s to these points show the position of the cord as it is played out. This is a mathematical curve resulting from the weight of cord and kite, wind pressure on cord, and lifting power of the plane.

It will be seen that the kite finally moves along horizontally, no matter how much cord is played out. This occurs when the lifting power equals the force of gravity and wind pressure. In other words, the kite can do no more without an increase of wind.

To make it go higher, we must raise point s by tandem flying, attaching another kite and cord to the first one, as shown at x.

Three or four Eddy kites may be flown in this way, the lines of equal or unequal length joined at a common point to the main line; and, strange as it may seem, if they are well balanced kites they will not interfere with each other. In fact, there seems to be an electrical repulsion among the lines, so that they spread out like a broom.

This is one of the most interesting discoveries in kite flying, though badly upset in actual practice, when one member of the team becomes erratic and proceeds to make a braid of the four cords by diving under and over the others to bring about a general demoralization. For this reason, it is wise to test each kite separately, first, to discover any possible tendency to freakishness.

A weird experience may be enjoyed by leaving the tandem out after dark. Run the main line down by slipping it under your arm, and walk out until you reach the junction of the four lines, where a light-weight lantern can be attached. Let go, and see the lantern apparently drawn up into the air by noiseless, invisible hands.

Flags and other devices may be attached as indicated in the drawing; a light stick at a b will keep the flag from blowing up into a heap, and loops at a and c are tied in the main line to avoid sliding.