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Report No. 391. The Aerodynamic Characteristics of Eight Very Thick Airfoils from Tests in the Variable Density Wind Tunnel, by Eastman N. Jacobs, I4 pages, illustrations, quarto. Washington, Government Printing Office, I93I, price ten cents. A group of eight very thick airfoils having sections of the same thickness as those used near the roots of tapered airfoils were tested in the Variable Density Wind Tunnel of the National Advisory Committee for Aeronautics. The tests were made to study certain discontinuities in the characteristic curves that have been obtained from previous tests of these airfoils, and to compare the characteristics of the different sections at values of the Reynolds Number comparable with those attained in flight. The discontinuities were found to disappear as the Reynolds Number was increased. The results obtained from the large-scale tests in this series indicate that the N. A. C. A. oo21 airfoil, a symmetrical airfoil having a thickness ratio of 21 per cent., has the best general characteristics.
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Price, ten cents. This report contains the results of a series of tests with three wing models. By changing the section of one of the models and painting the surface of another, the number of models tested was increased to five. The tests were made in order to obtain some general information on the