Fig. 62.—Umbrella Ribbing Plane
The Cane Plane.—Another form of construction that is very light is that shown by [Fig. 61]. Here a length of thin cane is bent to the form of the outline, the ribs being bent to align with the leading and trailing edges. Gluing and binding is used here. Such a plane can be made light, but it always has an appearance anything but neat. It cannot be advocated for machines over 30 in. in span.
The Umbrella-ribbing Plane.—Umbrella ribbing can be utilised, in conjunction with piano wire, for plane construction as shown by [Fig. 62]. The channel of the ribbing should be thoroughly cleaned with emery cloth, so that the leading ends of the ribs can be soldered therein. Three spars should be used for spans over 30 in.
For the planes of model flying machines steel wire offers exceptional advantages, as it is practically unbreakable and can be bent to any desired shape. Another advantage is that it offers a minimum resistance when travelling in the air. To the uninitiated, the making of steel-wire planes is a difficult undertaking; but if the following instructions are carefully carried out the planes will prove very satisfactory.
First procure a piece of wood about ½ in. thick and slightly larger than the plane to be made, and draw on it a plan of the plane as shown in [Fig. 63]. For example, it will be assumed that a plane 30 in. span and 5 in. wide, having four ribs, is to be made. For planes approximately this size, No. 17 s.w.g. steel wire is employed. Before beginning the work the wire should be straightened as much as possible. Then lay the wire over the plan, beginning at A ([Fig. 63]) and passing round to B. As the wire is bent to the shape of the plan, it must be fastened down to the board by means of small staples. Then cut four pieces of wire for the ribs C, D, E, and F, allowing ½ in. each end for turning at right angles as in [Fig. 63].
Fig. 63
Fig. 64
Figs. 63 and 64.—Making Wire Planes