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. The plane should be cut from a sheet of aluminum, preferably. Fasten this securely to the front of your motor base with nails, or tying in position. The wires of the hooks holding the ends of the motors may be passed through the holes cut to the back of the rear edge of the plane and bent over. Of course it is very simple to anchor double motors, or even multiple motors, in this way.