The plan outline of several German machines is shown diagrammatically by [Fig. 72]. It will be seen that from the nose the body gradually widens out until the maximum width, generally in the vicinity of the front seat, is reached, from where it tapers to the tail. This shape appears to satisfy aero-dynamic requirements more closely than either of the foregoing examples; but in practice the difference is not appreciable, and in any case the reduction of head resistance does not compensate for the additional work.
Fig. 73.—Fuselage outline.
Fig. 74.—Fuselage outline.
In side elevation the general practice, with exceptions, is to arrange the top longerons parallel to the line of thrust, i.e. the axis of the motor, as in [Fig. 73]. This simplifies erection and affords a convenient datum line for truing up.
Fig. 75.—Fuselage outline.
On the German Rumpler and early Albatross biplanes, the upper longerons are curved, as in [Fig. 74], but in the most recent versions of the Albatross they are level with the line of thrust. [Fig. 75] illustrates an arrangement where the top rails, from a point some distance along, slope down to the nose. By this method the body weight is kept as low as possible and the engine and accessories rendered more accessible. Although it is usual to terminate the body in a vertical knife-edge, formed generally by the rudder post, another arrangement, typical of the Morane monoplane, finishes in a horizontal edge. The German Fokker, obviously inspired by the French Morane, and the Albatross DI, are similarly terminated. This system of tapering to a horizontal knife-edge is not considered the best arrangement from a strength point of view, the flat angle of the bracing wires permitting a certain amount of movement, eventually resulting in slackness and loss of alignment.