The effect on airplane performance of the factors that must be considered in applying low-drag cowling to radial engines

Mcavoy, William H Schey, Oscar W Young, Alfred W
naca-report-414
1933


This report presents the results of flight tests with three different airplanes using several types of low-drag cowling for radial air-cooled engines. The greater part of the tests were made with a Curtiss XF7Cc-1 (Sea Hawk) with a 410 horsepower. Wasp engine, using three fuselage nose shapes and six types of outer cowling. The six cowlings were: a narrow ring, a wide ring, a wide cowling similar in the original NACA cowling, a thick ring incorporating an exhaust collector, a single-surface cowling shaped like the outer surface of the exhaust-collector cowling, and polygon-ring cowling, of which the angle of the straight sections with the thrust line could be varied over a wide range.

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http://naca.central.cranfield.ac.uk/reports/1933/naca-report-414.pdf