I have been having fun with a used Avistar lately. It's a fun little airplane with a great inverted flatspin. The only thing I really don't like about it is that at high speeds when you give elevator it likes to "balloon" up to a very high AOA very quickly. While this makes for snap roll I am worried that any engine bigger than the old worn out LA 40 on it will snap the wings in half if I give it too much elevator at speed.

Is this just a semi-symmetrical trainer trait or is there something I can do to prevent the "balloon."

A flat bottom wing will do worse as will any high winger heading into to the wind. Cut down on the elevator travel.

If it's semi-symmetrical it really shouldn't balloon too badly.

It COULD be that the wing is not sedure enough, and when you pull up at high speed, the wing lifts at the LE which will change the incidence for a second resulting in a bad balloon.

Try adding a few more rubberbands on each side of the wing.

Hope the wing halves were epoxied together and not solely using the little metal straps and trim tape.

If your wings are epoxied it should be fine. I rag the hell out of mine (running OS 46LA) and have had no problems.

I found with my Avistar that it doesn't really need that much elevator throw. I maxed mine out and it was overly responsive under the conditions you state. I recommend toning them back down and it will fly much better. The Avistar is a really fun plane. I wish you could get more throw on the ailerons for faster rolls.

I believe MinnFlyer nailed that one. I remember someone saying 2 rubberbands for each pound of plane. Thats 10 for the Avistar and two more just in case. Also don't try hanging on to those rubberbands too long, they get weak and new ones cost less than a plane. Joe

I have been doing some very harsh manuvers so I have been using 16 #64 rubber bands. The wing is epoxied correctly. Before I put my OS 50 SX on it I plan on fiber glassing the wing joint. What would be involved with turning this into a bolt on wing?