This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt: ... 38, as illustrated in Fig. 8, the raked wing was decidedly superior to the rectangular form into which it was cut down. Nor can this improvement be due to variation in aspect ratio which is negligibly small. The ratio of maximum L/D was about 1.2 to 1. It would seem therefore that experiment is in agreement with practice in imputing certain advantages to raking. But in view of the variation in results with wings of different camber, it would be unsafe to employ a correction ratio of 1.2 in maximum L/D for the raking of any other wing, say an R. A. F. 6 section, until there has been further investigation of this point. Swept Back Wings Another variation in the plan form of wing sections, very largely employed on German machines of recent type, and also on one or two American machines, is that of swept back wings. Swept back wings are mainly used to give lateral stability. It has also been thought that their arrow-like form gave them an increased aerodynamic efficiency, and that longitudinal stability was also improved by their employment. We are not at present concerned with lateral stability. Aerodynamically a recent investigation at the Massachusetts Institute of Technology shows a progressive decrease in efficiency with increased sweep back. As regards longitudinal stability the action is peculiar and not at all as satisfactory as that of the wings with reversed trailing edges. An R. A. F. 6 wing, originally of aspect ratio 6 was em Fig. 9. Wings Used In Experiments On Swept Back Wings The centre of pressure motion is illustrated in Fig. 10. It has the same peculiar characteristic for each of the wings. At small angles the centre of pressure moves forward, thus checking diving, but at large angles the centre of pressure again moves forward, thus tending ...
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