The video shows a hint of what may be a damaged (cracked/kinked) trailing edge in the area where the torsional flexing is occurring.
If the trailing edge of the elevator is compromised, it would have a negative impact on torsional rigidity.
Is he sure that it didn't get damaged in some way while at the fly-in?
If nothing similar to a flutter event was ever noticed (If it happened he likely would notice), I think it is unlikely this was related to improper balance of the elevators.
BTW, you wrote "failure of an unbalanced elevator". Did you mean it had no weights on it, or did you mean not properly balanced?
Any opinions expressed in this message are my own and not necessarily those of my employer.
RV-6A (aka "Junkyard Special ")
Last edited by rvbuilder2002 : 08-13-2017 at 10:26 AM.