Pressure distribution over thick tapered airfoils, NACA 81, USA 27c modified and USA 35

Reid, Elliott G

At the request of the United States Army Air Service, the tests reported herein were conducted in the 5-foot atmospheric wind tunnel of the Langley Memorial Aeronautical Laboratory. The object was the measurment of pressures over three representative thick, tapered airfoils which are being used on existing or forthcoming army airplanes. The results are presented in the form of pressure maps, cross-plan load and normal force coefficient curves and load contours. The pressure distribution along the chord was found very similar to that for thin wings, but with a tendency toward greater negative pressures. The characteristics of the loading across the span of the U. S. A. 27 C modified are inferior to those of the other two wings; in the latter the distribution is almost exactly elliptical throughout the usual range of flying angles. The form of tip incorporated in these models is not completely satisfactory and a modification is recommended. (author)

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