It's not the spinning that may break the aircraft, it is the recovery.
Let it go too long and build up too much airspeed and pull too hard and,
yes, something may break.

On Sat, 02 Apr 2005 21:46:19 -0400, Dave
wrote:
- It is gentle on the aircraft...

Cub Driver wrote:
Chandler AZ has two Super Cubs. Since I'd never flown at that time, I
asked to do my spin training in a PA-18. They refused because the Cubs
(unlike the Great Lakes trainers they use for aerobatics) have gyro
compasses, and they didn't want to tumble the gyros.
Similarly, Hampton NH prohibits spins in its J-3/L-4 Cubs because of
the age of the aircraft.
So there are two FBOs that don't seem to agree with the gentility of
spins. And I have to say that when I did the spin training in the
Great Lakes, though it was milder than some of the aerobatics I did
later, it was not totally benign. After 90 minutes of it, in the heat,
and driving back to the motel past the stockyard, I sometimes felt
that my own gyros were about to tumble.