For the aerodynamics heads out there here is some fascinating research from Stemme, the company that makes one of the more amazing motorgliders in the world. They are looking into reproducing the stall-mellowing effects of having self-actuated, top surface, partially porous flaps that mimick the effect of feathers on birds' wings to prevent stall separation from progressing forward on the top surface, well beyond the critical angle of attack: http://www.bionik.tu-berlin.de/user/giani/vortrag/sld002.htm The 'slide show' format of their presentation is very clear (be sure to read the text at the bottom of each page), and should do a great job of explaining this concept, so even if you're not an engineer, have a look! You'll very likely 'get' it. Enjoy watching these german experimenters in their efforts to preserve Lift, Scobie in Seattle RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]