Source: 2009 Q1 Beartracks, Rex Ervin
I constructed a set of Stewart wingtips for my Bearhawk. They are STC’d for the Piper J-3 to PA-22 airplanes. They give the Pipers quicker take off, climb, and cruise, also a flatter glide and lower landing speed. They are formed simply by the the junction of two planes. The upper “plane” is a continuation of the airfoil outward to where it meets the lower plane. The lower plane is flat and angles upward and outward at a predetermined angle off of the flat portion of the wing. The angle is determined by extending a line parallel to the spar outward 12″ from the deepest vertical part of the airfoil(about 4″ behind the spar on a Bearhawk). Then drop a line back down to the bottom of the wing directly below the upper point at the deepest part of the airfoil. The angle formed between that line and the bottom surface of the wing is the angle used to form the bottom surface of the wingtip. The bottom surface matches the slight droop of the flaps and ailerons. The elliptical shape of the tips is automatically established by the junction of the airfoil “plane” of the upper surface and the mostly flat plane of the bottom surface. Even if they don’t help the Bearhawk, I’ve had fun learning how to work fiberglass.
Rex Ervin, QB#43