RCM trainer 40...K&B .40...and not enough reinforcment on the wing center section...combined with full throttle snap rolls from wide open level flight...

SNAP...wooggaa woogga wooga...whump![X(] (that's the sound it made as it spiraled in from about a hundred feet )
One wing panel stayed on and the other fluttered down like a Maple seed...
I did pull the throttle back just before it hit though, to keep the dirt out of the carb...unfortuately, the carb got broken off at the front housing. (funny that the plastic Perry carb neck didn't break...the alum. front housing did!)