Spinning Characteristics of Wings V : N.A.C.A. 0009, 23018, and 6718 Monoplane Wings
This is a 1938 NACA technical report, issued by the National Advisory Committee for Aeronautics, on how monoplane wing sections of three profiles behave in a spin, written for aeronautical engineers and aircraft designers. The first picture is a set of line graphs plotting the effect of pitching-moment coefficient on the aileron movement needed for spin equilibrium, with curves labelled by wing section; the second is a photograph of a rectangular wing with rounded tips mounted on a spinning balance, its wooden blade and metal struts set against a dark tank wall, showing the test rig a designer could imagine for model wind-tunnel work.
