You are so right, Dick. As Sal is with his statement. Sigh... ;-)
As to tucking, just the discussion last year about tucking (I think of a Mambo) was one example I thought of when remembering your reasonings. I didn't apply it to this case, though. I only thought of the center of lift moving forward when AoA increases. I excluded small AoAs because I would avoid them, anyway, with undercambered airfoils on wings and stab (to avoid the bottom side stall).
Undoubtedly, IM's wings will produce a big down-pitchting moment. Even if the stab might contribute and aeroelastic effects as well, I guess the wing to be the biggest player in that game. While the center of lift (CoL) is at 30% chord in slow flight, the airfoil measurements stop at Cl=0.3 where the CoL is at 65%. Here's where bottom-side stall begins and I don't know how that affects CoL.
But...this stall makes for quite noticeable drag, which may prevent even bigger airspeed. At least the original IM could have had so much drag and so weak engines that there was no risk of tucking under. In fact I even think they could have put up with pitch instability to have a really lifting stab due to lack of engine power in 1913. Anyway, Sal, you could lay out the drives of your IM model (battery voltage, motor Kv, prop pitch) to avoid too much speed, which would be 40 mph for a 0.3 lift coefficient. A dive wouldn't do much for more speed due to the big drag emerging then.
Aside from undercamber, the stab's size (33% of wing area like a very stable and damped model) might have been intended to avoid tucking. Maybe they knew about this problem, after all they used those thin undercambered airfoils exclusively. The more camber the more pitching moment, even at zero lift. Since the moment increases with square of speed, independent of AoA, it can be counteracted only by a big stab whose lift increases with square of speed as well (or by a reflex in the airfoil).
I like such speculations but by and by they begin to suck. Should I quantify things, a moment plan, a simulator model?
Last edited by UStik; 06-26-2015 at 10:33 AM.
Reason: personal year-2000 problem