Wing strength
When preflighting a small airplane, especially an ultralight or small experimental, I sometimes push the wing tips upward hard to listen for any unusual noises or feel for internal damage. I always figured that I cannot put enough force on the wing to hurt it. However I have a lot of leverage at the tip and maybe it is not a good idea. I might be putting more force on the wing this way than it is designed to handle. Or maybe if it can handle this it is strong enough for flight.
Is there anybody out there in cyber land who can shed light on this subject? At least before I break something?