Airtronics was the company that produced the Aquila Grande back in the seventies and they also thought about aerodynamic efficiency and replaced the Aquilla Grande with the E 205 equipped Sagitta 900 (http://www.dchobby.com/thermal/sagitta900.html). Later came the Legend with full house controls and the S 3021 airfoil. In 1995 Tim Renaud from Airtronics asked Selig to design an airfoil for beginner gliders. It should be better than the Aquila-type airfoils and to make it easy to build it should have a flat bottom on the hindmost 75%. At the same time it shouldn’t accelerate as the best of today’s airfoils. In other words he ordered an airfoil that could sink slow at slow speeds, have a fair gliding angle at low to moderate airspeed, but it should still create drag to act as a moderate brake when speeded up. The result was the S 7055 that looks a lot like the old Clark Y – just a bit thinner. Surprised? Go back and read what I wrote about Clark Y. Be aware that the Clark Y DOESN’T has a flat bottom from leading edge to trailing edge – there is no such thing as a “flat-bottomed Clark Y” (do I repeat myself?). If you’re designing a glider for a beginner, consider the S 7055 or Clark Y. S 7055 should be a good airfoil for gliding in moderate wind because of the sinking speed and the penetration should be a bit better than that of the Clark Y (I hope the AMA team is listening – will there be a Dassel 2 with S 7055? It should be better than E 193 when ballasted!).