Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/430

App. VIIIb. good, because owing to the boomerang coming (translationally) to rest at the highest point of its flight path, its efficiency from an aerodynamic point of view becomes very poor, and the duration of the flight is correspondingly shortened. By initially inclining the plane of the boomerang when thrown as in Fig. 197, the flight path becomes (in plan) a loop of approximately circular

Fig. 196.

form. Fig. 198, and its velocity is nowhere unduly lowered. If the boomerang be supposed to lose none of its velocity, either rotational or translational, and neglecting the "disc effect," it would be possible to find conditions such that the flight path would be truly circular, the precession taking place about a vertical axis, as in the case of a spinning top, or more exactly

Fig 197

a gyroscopic conical pendulum. Fig. 199. It is commonly the object of the thrower to approximate as closely as possible to such a circular path.

In making the comparison between a boomerang in flight and a gyroscope pendulum it is necessary to suppose the said pendulum loaded with a heavy counterpoise, in order to simulate the conditions as to the direction of torque and of precession; thus any influence acting to hurry the precession reduces the