Tank Pillowing

RV7Factory · #1 10-31-2006, 12:09 AM

Since this seems to be an issue not specfic to any model I will post this here.

Despite my best efforts during construction (it was perfect before riveting), I have some slight pillowing of the tank skins between the first two screws which attach it to the splice plate. I understand this a fairly common issue, and I have searched but not found a resolution to my particular case.

Here is what I got...

You can see the tank skin pillowed about the thickness of the skin between the first two screws. The spar isn't sagging, there is no excess sealant in this area interfreing with the splice plate, the tank is screwed/bolted to the spar, and it occurs on both wings in the same spot but nowhere else.

I have been able to improve it somewhat by forming the tank skin by hand, but other than filler

, does anyone have any suggestions on how to further improve the fit?

Thanks,

ww2planes · #2 10-31-2006, 01:15 AM

I had the same problem and just grabbed the nearest shrinker and very very gently brought the pillows home. Be careful and only a small amount at a time. Practice on some scrap and see just how much this thing can do.

TShort · #3 10-31-2006, 05:26 AM

Have you tried pushing it down with the screws just a little loose and then tightening?
If that doesn't work maybe slightly enlarge the holes for the screws in the direction of the pillow and then push down and retighten?

I guess if they're on for good (knock on wood!) you could put a little proseal in there and then clamp it down while the proseal dries...

Thomas

treeez · #4 10-31-2006, 05:46 AM

Bill, can you tell more about a shrinker. I'm not familier with that tool or procedure. Thanks, Mike

cytoxin · #5 10-31-2006, 06:00 AM

mine did this as well, i have yet to try to fix it. i did remove the nutplates and arch them. helped a small amount but still have some . seems to me its more like a flat spot where the nutplates are but i wondered how many were like this.

Rick6a · #6 10-31-2006, 06:04 AM

Quote:

Originally Posted by RV7Factory

.......some slight pillowing of the tank skins between the first two screws which attach it to the splice plate......any suggestions on how to further improve the fit?

Brad,
You could approach the problem from an alternative perspective.
Here is one possibility.

ww2planes · #7 10-31-2006, 10:24 AM

The shrinker is a device that will actually grab the metal and shove it together or if you switch jaws you can do the opposite. It is usually table mounted and is very simple. You put the metal into the jaws and pull on the handle. As the jaws come together they grab the metal and litterally compact it in the area that has been grabbed. It is terribly effective and only a small amount of work will move a lot of metal. You do not want to work your skin a whole bunch and whatever you do dont over do it because you want to keep the strength in the metal. Dont be afraid to use it just be careful. I have seen these tools in several of the suppoliers catalogs. For me it was the purfect fix. I used it in the same area that you have and along the trailing edge of the tank. No shims or proseal to mess with and the tank matches the wing nicely.

sf3543 · #8 10-31-2006, 01:26 PM

I like Rick's solution of using shims on the leading edge skin abutting the tank, but here's a couple of things you could try, first:
Get some aluminum tape and put on a layer all around the flange supporting the tank edge. The ply is thin, but by doing this, you will fill up the extra space all around the radius of the tank and this may cause the pillowing to disappear. I'm guessing you could probably even try two layers of tape without seeing a noticeable edge on the tank skin, expecially if you have the edge chamfered.
Also, either in conjunction with the above or separately, try tightening down the screws on the top of the wing first. If nothing else, you might be able to move the pillow effect to the bottom where it is less noticeable.

RV7Factory · #9 10-31-2006, 03:07 PM

Thanks for all the suggestions!!! I appreciate it.

Rick6a, as usual, you go above and beyond with your assistance. Thanks!

I will try a few of the less invasive things first and see if I see any difference. If I don't see any improvement, then I will go to the shim, which ironically was something I already did on one wing to improve the fit at the aft end of the tank.

I'll post my findings here soon.

RV7Factory · #10 11-14-2006, 11:17 AM

After trying a few of the suggestions, with moderate results, I decided to go the shim route. It worked great. Thanks Rick!!!

AFTER...