Upper wing skins oil canning

The other day I was wiping the winter grunge off the upper wing skin of my RV-9A and I noticed the outer (by the tips) upper wing skin panels seemed to be more "oil canny" than I remember. It's normal for people to go insane during the long Minnesota winters, so perhaps the skins have always been like that. There has always been some clink-ity, clink-ity when the skins are wiped. For you 9 lovers out there how much if any "oil canning" do you notice on the top wing skins?

Bryan

Upper wing skins on RV-9A...

Bryan,

Take a look at my left wing in this photo. In flight, the skins rise up between the ribs, stiffeners, and spars due to the low pressure above the wing in flight. It is a reminder from Bernoulli why our wings lift us off terra firma.


By the way, this photo was taken on my first flight to Oshkosh in 2005. See this web page for the full story of that flight.
http://www.n2prise.org/rv9a151.htm

If you jack up a plane it also does this. ie when the jacks are under the wings.