Wind-tunnel investigation of two airfoils with 25-percent-chord Gwinn and plain flaps

Ames, Milton B , Jr
naca-tn-763
May 1940


Aerodynamic force tests of an NACA 23018 airfoil with a Gwinn flap having a chord 25 percent of the overall chord and of an NACA 23015 airfoil with a plain flap having a 25-percent chord were conducted to determine the relative merits of the Gwinn and the plain flaps. The tests indicated that, based on speed-range ratios, the plain flap was more effective than the Gwinn flap. At small flap deflections, the plain flap had lower drag coefficients at lift-coefficient values less than 0.70. For lift coefficients greater than 0.70, however, the Gwinn flap at all downward flap deflections had the lower drag coefficients.

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http://naca.central.cranfield.ac.uk/reports/1940/naca-tn-763.pdf