FIG. 16. A good method of building a wooden plane.
The best method is illustrated in Fig 16. A piece of wood of the same length as the completed plane and having a cross section like that at A is glued to the forward under edge of a flat plane B. After the glue has hardened, the plane is worked down to the shape shown at D which is very close to the stream line form. The plane is then varnished to prevent it from absorbing moisture and losing its shape. The ends may be covered with thin Jap silk, carefully glued on to prevent splitting. The Wright brothers cover the blades of the propellers on their aeroplanes with silk for the same purpose.
Air does not flow smoothly when changing from an interrupted flow to an uninterrupted flow around a square corner and so by rounding the ends of the planes, the disturbance at that point is somewhat eliminated.
Planes having rattan or piano wire edges cannot very well be of any other shape than those which are illustrated in Fig. 17.
FIG. 17. Various shapes a plane may take.
It is a good plan to give wooden planes the shape shown by 3 and 4 in Fig. 17, as the disturbances mentioned above are not so marked.
FIG. 18. An edgewise view of several planes showing the different ways they may be bent to secure stability.
The planes of large man-carrying machines possess the same characteristics, but not to such an alarming extent as in a model. The Voisin aeroplanes overcome the objection by the use of vertical panels set between the planes.