I was checking the formula that was posted on stab & rudder volumes to see how it related to some of the planes that I fly, specifically on one of my hand launches that has a bit of a Dutch roll to it. Sure enough, the rudder seemed to be undersized. I added a lower fin (like a "x" tail) and it flies much better. The formula for the rudder was: .02 = area rudder x tail moment/wing area x span The formula for the stab was: .46 = area stab x tail moment/wing area x mean average chord What was interesting about this was as the tail moment decreases, the area increases. There must be a point where this formula falls apart, however. There must be some nether zone between where the tail moment is short, the stab and rudder area large....and a flying wing. It does work going the other way, ie. the stab and rudder areas of the Logic. Some of the free flight designs don't exactly follow this formula however, especially the high aspect ratio F1A Nordic gliders. Must be more to it than the first run through... JE -- Erickson Designs John R. Erickson, AIA Architecture, CAD, Consultation W/F (661) 288-2959 RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
