The attached paper is the first time I have ever seen a study of a Gurney flap with an airfoil suitable for light aircraft. The NACA 23018 is often used as the root airfoil on tapered cantilever wings, usually transitioning to a thinner NACA 230XX section at the tip. A constant-chord NACA 23018 airfoil is used on the Sky Pup ultralight. From the numbers in this study, the Gurney flap looks like an interesting option for a low and slow aircraft to get more lift at high angles of attack with little drag penalty in cruise and no mechanical complexity at all. What do you think? Cheers, Matthew
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