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Aviation History
1939
1939 - 1724.PDF
JUNE I, 1939 fi& ®m 567 Fig. 1. A " corner in wind tunnels " : The large building on the left contains the full-size tunnel at Langley Field. The new 12ft. free-flight tunnel is inside the steel sphere seen at the end of it, and a corner of one of the high-speed tunnels can be discerned beyond. RESEARCH-ANCIENT and MODERN From the Wright Brothers to the N.A.C.A. : 27 m.p.h. to 500 m.p.h. : Dr. Lewis's Wilbur Wright Lecture THERE have been many Wilbur Wright Memorial Lectures at the Royal Aeronautical Society. In fact, this year's was the 27th. But there have been few which equalled in general interest that given last Thursday by Dr. George W. Lewis, Director of Aero nautical Research, National Advisory Committee for Aero nautics. It may be that the juxtaposition of the oldest and most modern research equipment helped to create this impression. And it did give an opportunity to admire and marvel at the foresight and thoroughness of the Wright Brothers who, as the lecturer pointed out, included in their research programme all but one of th& important variables m 1901! Dr. Lewis dealt in his lecture with the Wright Brothers' wind tunnel and its equipment and results; with the new 8ft. 500 m.p.h. tunnel; with the new low-turbulence tunnel; with the new gust tunnel; with the 5ft. free-flight tunnel; and with the latest N.A.C.A. 12ft. diameter free-flight tunnel contained in a spherical steel shell. Describing the Wright Brothers' wind tunnel, the lecturer explained that it was 5ft. long, with a square test section of 22in. sides. The speed attained was 27 m.p.h., or 40ft./sec. The original plottings of profile and plan form of some of the aerofoils tested are reproduced in Fig. 4. Dr. Lewis called attention to the fact that models 7, 8 and 9 were plates with camber forming part of arcs of circles, the camber being varied systematically; while models 10, n and 12 had the same amounts of camber, but had the maximum camber placed farther forward. The aspect ratio was 6: 1 (rin. chord, 6in. span), which is now standard in research laboratories. In Fig. 5 is shown, from original sketch and photograph, the lift- measuring balance, and in Fig. 6, the balance for measuring D/L. This latter balance measured directly the ratio of drag to lift as the tangent of an observed angle, "a method," the lecturer said, " which may appear tempting even now to the wind tunnel investigator, overburdened as he is with the calcu lation of induced interference effects." The Wright Brothers measured the lift against a set of resist ance plates which had previously been calibrated against the drag of a square flat plate of known area. The drag was measured as a percentage of the lift. Direct measurement of actual forces to be expected on the full-size machine was not made then, but came in 1902, when a glider was built and tested against a wind of known velocity. The weight being F«- 2 (left) is a replica of the Wright Brothers wind tunnel of 1901. In Fig. 3, on the right, is seen the free-flight tunnel in operation. The man in the foreground controls the tilt and air speed, while the model is controlled by the man on the right
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