RE: Katana 50 by Hangar 9
Many thanks for your insights re the flutter, which certainly wasn't good but I am hoping it's old.
The mechanical advantage I had was highly detrimental and I believe you are right in saying that it was the instigator of the flutter. The main point I would make is that I set this up exactly as per the Hangar 9 instructions, using new servos of the make and model that they recommended. I think it is highly likely that anyone else foolish enough to do the same will have the same problems. Hangar 9 should change their instructions.
Yes, I was incredibly lucky that my plane didn't break up in the air. I shut the throttle the moment I realised there were big problems, probably within about a second of the flutter starting. I think another tenth of a second would have been enough to destroy the plane. The force required to break the wing completely beyond the point it had got to would have been relatively minor. These forces were fairly incredible: enough to break servo arms, rip off an aileron, break the wing and strip two servos completely, in one or two seconds.
I agree that the plane is not really badly designed (I bought this on the strength of my satisfaction with previous Hangar 9 planes, including a Funtana 125 that has withstood all the aerobatics I have thrown at it over a three year period), but there is weak point in the notched main spar at the position of the end of the wing tube. This was not helped by rather inferior glue holding the rib there to the spar.
Anyway the plane is now flying very well (see attached, showing my improvised new colour scheme) on wings that are vastly strongly than the original. Yesterday, I really put the plane through its paces and there is absolutely no sign of any strain.