Bottom Outboard Wing Skin "oil canning" question

[snoopyflys]

Most of the threads I have found discuss oil canning of control surfaces. My question is with the bottom skin, specifically the bay just outboard of the lap joint. This is the only bay that has oil canning, the remaining bays appear to be "drum tight" as Mel has said before. Is this a structural concern or one of those cosmetic things that would cause more harm fixing than leaving well enough alone? This is my first encounter with this and look to the VAF for guidance.

Thanks,

[Bill Wightman]

Non-structural if its only oil-canning. If it really bothers you, the skin could be drilled off and replaced.

[mototopo]

Hi Dan,
I had the same issue on my left wing (top skin, 2 most outer bays). I discovered the oil canning before riveting the skin on, but it was really evident. I contacted Gus at Van's who told me it was just a cosmetic issue. He suggested me to verify the rib flange bent to reduce/remove it. In the event it was still there once riveted he suggested me to rivet or bond a stiffener (like on the elevators or on the bottom tank skin) between the ribs in the offended bays. Or simply leave it as is, is not a structural problem (at least in my case on the most outer bays). Just for peace of mind you may try to contact Van's.

P.S. Once riveted my the skin was drum tight so I didn't needed any further repair.

[snoopyflys]

Thanks for the reply Tom and Claudio. The issue did not present itself until I riveted the skins, no evidence during the many clecoing exercises I went thru. Amazingly all of the skin holes lined up with the underlying wing skeleton except for the spanwise rivets along the main spar. These rivet holes lined up after putting the wing in the cradle, let Mother Earth (gravity) pull the last 32nd together, cleco the entire span then rivet one at a time from the wing root to the tip. Wonder if my riveting technique contributed to the oil canning?

I plan to contact Vans today for further piece of mind and direction.

Thanks again.

[mototopo]

I had the same line up problem along the main spar riveting the inboard bottom skin. The suggestion from Van's was to start riveting from the main spar down to the rear spar. It was a little tricky (mainly on some rivets on the rear spar where I had to use some pop rivets) but that solved the line up problem. I have still not riveted the outboard bottom skin (waiting for inspection) but on the inboard one I don't have any oil canning.

I don't think the rivet sequence caused the oil canning. I noticed that just a minor touch up on rib's flange bent resulted in dramatic improvement against oil canning on my top skin.

By the way, adding a stiffener in your wing should not be so much difficult and will probably solve the problem.