On a stunt design with a w.s. of around 55" how thick should the high point of the root rib be if the cord length (not including flap measurement) is 10.000"? And same question for tip rib of 8.375" . Also hinge line distance of 17" would be about right? Power supplied by ST 46 with bristunt ABC P&L set and head supplied by same (might try saito 40 also later )
I think you guys have covered most of the airfoil possibilities as far as thickness goes. But based on some recent experience, I think that it makes almost no difference if you don't get the first 3/4" or so right. The "as delivered" ARF Strega is has a hugely thick wing, far more than even I had considered using, OK wing loading (about the same as my NATs airplane) and relatively large flaps. But the leading edge is pointy and it won't fly even mild corners, even at sea level and reasonable temperatures, without being on the edge of stalling. Blunt it a little, and no problem. As described here:
http://www.brodak.com/files/file/Strega_Building_Wing_Instructions.pdf It's essentially as Al described in his 1973 AAM stunt column - if it comes to a point (say, less than 1/8" LE radius) it "buffets" (i.e. stalls) in the corners, and you can fix it by sanding back through the sheeting to the underlying LE wood and rounding it off.
I also think the other issue is the "departure angle" of the leading edge shape. The ARF Strega airfoil also seems to be designed to fair smoothly into the 1/4 square at about a 45 degree angle, essentially going straight back at 45 degrees until it needs to start turning to fair in with the high point. Sort of like conformally mapping the Nobler airfoil with the x ordinates not scaled, and the Y ordinates scaled by 150%.
Point being, no matter what you do to the rest of it, if the LE radius isn't sufficiently blunt, you're going to have problems.
And before anyone jumps on me for jumping on ARFs again, or Cardinal/Tsunami/Stregas, I would note that the Vector 40 and the T-Rex "Bradleymobile" ARFs don't have the same issue at all - Brad's being particularly blunt, not quite to "Intimidation"/"Excitation" standards, but noticeably blunter than most.
Brett