Minor fuel tank pillowing

[bullojm1]

I installed my right tank for the first time last night, and noticed some slight pillowing on the top skin of the tank between the screws -- no more than 1/32". Is this small amount of pillowing normal, or can it be reduced to nothing? I don't want to chase something that can't be fixed! My one thought as to what could be causing it is too much sealant on the outside outboard rib, interferering with the joiner plate to the leading edge, causing the joiner to push the tank skin away from it.

Here is a pic of the pillowing:

http://rvplane.com/showthumb.php?picname=IMG_6810.JPG

Thanks for any advice.

[TShort]

Similar problem with resolution / tips:

http://www.vansairforce.com/communit...ight=pillowing

see entire thread...

Thomas

[Rick6a]

Originally Posted by bullojm1

I installed my right tank.......noticed some slight pillowing on the top skin of the tank between the screws...can it be reduced to nothing?....Thanks for any advice.

Mike,

I am beginning to think this may be something of a design gremlin. I received the RV-8 wing kit the first week of December, so I must conclude my kit is the most recent iteration of the design.

I suspect the problem is aggravated by 2-1/2" screw spacing in an area that has a significant curve to it. Note that the adjacent AD rivets have half as much spacing....around 1.25."

When I fitted the tanks, BOTH wings had minor pillowing in virtually the same location....almost exactly 3" aft of the upper leading edge. Everywhere else the butt gap between the tank and the leading edge assembly was near perfect. I know for a fact that in my case the pillowing has nothing to do with proseal interference or anything else. I even beveled the edges of the doubler strip to help relieve any possible conflict. In any event, the pillowing can be easily eliminated. A previous post will direct you to a thread that addresses this very issue. When I get around to removing the tank shown, I will pull the gap out (via the leading edge assembly) like I fixed it on the other wing. You are not the only one to experience this phenomena!

[bullojm1]

Rick,
I have uniform pillowing between most of the screws, with the worst one at the leading edge. I have a good feeling it is proseal interference. I will probably wait until the top wing skins are on before I try to fix it. I also agree that the forwardmost pillowing is because of the aggresive curve of the leading edge and not compensating for it by a closer screw pattern.

Thanks for the info.