The Monocoque Type.
The monocoque system originated in France, several constructors having produced machines incorporating this feature. The most successful machine produced on these lines was the Deperdussin, and many will recall the excellent streamline form of the machine exhibited at the 1913 Aero Show. These bodies were built over formers of various sections, which were removed when the glue joining the different layers had set. The resultant shell, which was about four millimetres thick, was then covered with fabric and varnished. Several factors militate against its extensive adoption as a method. It is rather costly, and does not seem to be suited to rapid production. In addition, the attachment of such members as the chassis, wings, and interplane struts, is more complicated. It should be noted, however, that various modern machines are similarly built. The Borel firm produced a machine with monocoque body, this being composed of three-ply covering on ribs running diagonally the length of the body, and although this is not such a lengthy operation as the Dep. system, it has not survived, unless one considers flying-boat construction as its modern version. A slight variation of the monocoque system is used for the bodies of some modern aeroplanes. The framework consists of very small stringers arranged at various points on light formers cut to the fuselage section. To this structure is applied two thicknesses of three-ply in the form of strips about 3¼ ins. wide, each thickness being disposed diagonally in opposite directions, as shown by [Fig. 68]. This is covered with fabric, the total thickness being no more than 1½ mm., and as this is made up of six layers of wood and one of fabric, the fineness of the ply-wood will be realized.
Fig. 68.—Arrangement of three-ply bands in monocoque fuselage.
It should be noted that the ply-wood strips do not completely encircle the formers, but are jointed at the top and bottom, a light longeron being arranged at these points.
A detail which would appear to be of great utility at the present time is the arrangement wherein the nose of the body containing the engine and accessories is a separate unit, and in the event of engine breakdown can be detached and another substituted.