What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

wrinkled wings

seagull

Well Known Member
When I put my -12 in the sun, 80+ degrees the wing skins wrinkle almost as though the aluminum was loosely pulled fabric. I understand aluminum has a high coefficient of expansion so I am guessing this is normal? I don't remember seeing other metal planes doing this but I really haven't looked closely. The horizontal stabilizer, vertical, and fuse do not seem to do this. Once the plane is back in the hangar for 30 minutes it looks all normal. Is this typical?
 
What you're seeing is the skins heating up and growing faster than the substructure. Leave it in the sun for long enough and the wrinkles will go away as the whole structure grows.

What color are your wings? This problem is more apparent with darker colors.
 
Last edited:
The wings are maroon on the inner 1/2, the outer half is white.

If the skins are growing faster than the sub-structure will that cause long term issues?
 
Pulling high G-loads, extreme whifferdils and whirligigs and extended inverted flight into outside loops can overstress wings and wrinkle the skins.

Wait......you have an RV-12........... :D
 
Can this stress the rivet holes, long term and cause rivets to start "smoking" ? Might be harder to see on darker colored paint schemes?
 
You see the wrinkling because the skin is flexing in response to the expansion. This minimizes stress on the rivets.
 
Paint color will have an influence on the sun heated temp. of the skins.
It will show up as a slightly loose/wavy look to the skins.
If it was of a structural or longevity concern the build documentation and maintenance manual would have specifications on what paint colors can be used.
 
Pulling high G-loads, extreme whifferdils and whirligigs and extended inverted flight into outside loops can overstress wings and wrinkle the skins.

Wait......you have an RV-12........... :D

I was about to say - go pull some G and straighten them out :D:D
 
My Navy Blue RV-12 definitely oil cans the top of the wing when in direct sunlight. Saw it today, as the fog burned off, four adjacent panels on the top of the right wing.
 
Last edited:
The leading edges of my 26 year old RV-4 are black. They wrinkle in the sun on hot days until the temps equalize. As Scott said, no worries.
 
I wouldn't get too excited about it. In fact semi-monocoque stressed skin aircraft structure can actually re-route stress under load until a condition known as "diagonal tension" arises where one diagonal of the skin basically turns into a truss link taking tension loads and the other diagonal takes compressive loads resulting in wrinkles. The diagonal tension actually turns the thin skin into a very capable tension beam that can withstand more load than a normally loaded stressed skin. So basically the skin panel gets stronger up and til it breaks.

It may not be a bad idea to keep an eye out for smokin' rivets. Mostly if there are any of the pop rivets who have lost their center mandrel with a resulting weaker strength allowing relative motion between the skin(s) and substructure.
 
Back
Top