The Buttercup was designed by Steve Wittman back in the late 1930s. Besides managing the Oshkosh, WI, airport, Steve was one of the premier air racers of that day. (He raced for the last time at the age of 85.)Steve wanted to demonstrate how much performance he could get from a small-sized engine. The Buttercup became the utility plane that he and his wife flew to support his air racing activities, and handily out-performed airplanes like the Piper J3 Cub and the Aeronca.
Steve never provided plans for this design, but Earl Luce reverse engineered them while re-creating the Buttercup (in the photo, displayed at Oshkosh) in 2002.
The Buttercup fits within the "light-sport" airplane rules, while providing better performance than many newer designs. As we were looking at various LSA designs at Oshkosh, Arlington, and elsewhere, my wife and I searched in vain for something with more luggage space than a shoebox: we need to carry just a bit of kit with us for weekend trips. And then we found the Buttercup! It's got a real fuselage, with real seats, and holds 60 pounds of stuff in a large baggage hold behind the seats.
Oh, and did I mention that it's a STOL aircraft? Wittman used the Buttercup to try out new design ideas, and fitted it with a movable leading-edge coupled to the flaps, for outstanding slow-flight performance.
Other basics: It's a "rag and tube" design: wood wings, steel-tube welded fuselage, two seats side by side. Steve originally used a 50 HP engine. Earl's plans show an engine mount for a 100 HP Continental, but some hot-rodders are using other small engines such as the Lycoming O-235.
