An ingenious biplane
It will be found a good plan first to lay out the exact form of your plane on a smooth board. Make the depth of the plane one-fifth of its length. It will be noticed that this plane is much more slender than those used last year. Next draw a line at the center the entire length of the board, and mark off one-tenth of the length of the plane from either end. From this center describe a quarter circle at either end, on the same side of the line. This will form your main or entering wedge. The rear corners should be cut sharply away and only slightly rounded.
There is no better material for the main frame than a thin reed, cane or bamboo. The longer ribs may be made of any light lath and the cross ribs of a thin flat strip of the same material. Soak the reed overnight to make it as pliable as possible, or heat it over a flame. Now lay the reed over the outline of the plane, and hold it in this position by driving thin brads on both sides and bending them over the cane. When the outer edge is complete, mortise the ends slightly and tie and glue firmly together.
With the outer frame held rigidly in position, it will be found a much easier matter to introduce the ribs. If you are building a flexed plane first, insert a stick of wood from end to end before placing your cross ribs in position. The thickness of this temporary stick will, of course, determine the curve of your plane. For a three-foot plane, a height of one-half an inch will answer.
The ribs may now be bent over this obstacle and fastened securely to the outer rim by glueing, tying, or nailing. The cross ribs may also be raised by inserting small wedges between them and the longitudinal ribs. When your frame is complete, loosen it from the board and you will find it regular and rigid. Cover it with a very thin cloth pulled tightly over the frame, and glue or sew it in position. A small plane may be covered only on the under side.
Excellent results are being obtained in England with planes built up entirely of wire. If aluminum wire is used, the weight of the wings is considerably cut down, but even ordinary wire will be found lighter than wood. For a plane thirty inches in width, or thereabouts, the wire used should be at least one-sixteenth of an inch in diameter, and should be soft enough to bend easily and hold its position.
It will be found a good plan to plot out the exact shape of your plane on a sheet of paper, and then bend the wire over this outline. The ends may be fastened together readily by binding tightly with fine wire, such as florists use, and touching the joint with solder. Be careful, of course, to keep the joint smooth. The cross ribs of these metal frames may also be made of wire. Bend the ends at right angles and attach to the inner sides of the plane with fine wire, and touch all the joints with solder.
There are several advantages in the metal planes. It is a very simple matter to flex the plane by bending the cross ribs and the ends upward to the desired curve, much easier than when working with wood. Such a frame will stand almost any amount of knocking about without injury. A swift volplane to earth, which would smash any ordinary wooden frame to "smithereens," would have little effect on a model plane. Such frames again are very easy to cover.
It will be found a good plan to sew the cloth to one edge, draw tightly across and sew fast to the opposite side, while a few stitches around the metal cross ribs will give it any curve you desire. A metal frame makes it possible to experiment with various curves. It is an easy matter to bend the ribs up or down and alter the line of the plane at will.
Small stability or guiding planes may be made of a sheet of metal, although such construction is not advisable for the main plane. When your front or entering plane is the smaller one, it is possible to turn it into a very efficient motor anchorage.