end edge effect on the one hand, and the frictional equilibrium on the other, assisted it may be by an auxiliary fin, or by the upturned corners, as described in § 6.
The backbone (Fig. 18) is of triangular section, and serves for the attachment of the various functional parts, also supporting the ballast, by which the centre of gravity is brought to its correct position.
The construction adopted was of a most substantial description, in no way suggestive of the lightness it is customary to associate with a flying model, the backbone, tail-plane and fins being of white pine, and the aerofoil of thoroughly seasoned and dried pitch pine[1]; the ballast being made from a strip of
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Fig. 20.
sheet lead, wound spirally round the backbone, and nailed or otherwise secured in position.
A small cross-piece serves the purpose of supporting the nose of the aerodone on the runners of the catapult during launching.
§ 12. The Author's Experiments (continued). The Catapult.—The catapult employed for launching the aerodone is illustrated in Fig. 21; briefly this apparatus consists of two runners, on which the aerodone is free to slide, separated by distance pieces arranged at intervals along its length, leaving a groove about 1 inch in width by which the backbone of the aerodone is guided
24
- ↑ Pitch pine is not a particularly suitable kind of timber, owing to its being liable to develop a twist. Mahogany would be better in this respect, but it is more easily injured by impact.
