On Sep 15, 8:50*am, Brad wrote:
On Sep 15, 8:09*am, Kenneth Kilbourne
wrote:

What causes the buckling/oil canning on the bottom of the ailerons and the
elevator on Grobs? I have looked at 6 ships and they all have the same
problem.
What's the fix?
KK

not sure about the fix, but am guessing the cause is no foam core on
the lower skin, and several ribs that are now giving the "starved
horse" look.

I've seen the same thing on the Grob Astir's on our field.

Brad

"They all do that" is the common refrain. I'm pretty sure it's caused
by the shrinkage of the fiberglass/resin matrix over the decades. Back
in the days when I built 'Old Time' free flight planes with very
pronounced undercamber, the same thing would happen to the silk
covering between the ribs.
I don't think there is a fix worth doing.