Fuel Tank Woes in Missouri

[Jerald Folkerts]

Probably for Wayne, but anyone please jump in.

I'm building an SR 2500, stock Super Rebel with an extra
fuel bay (four bays total). Yesterday, I tried the balloon test on my
almost completed right wing and couldn't get the balloon to stay inflated.
I pretty well isolated the problem to the bottom corner near the fuel filler
cap, in the first bay outside the tank (top wing skin is still removed) near
the spar. I added approximately 10 gal of water to the tank, and yes, found
water seeping out between the wing/leading edge skin and the bottom spar
flange in the first bay outside the tank. Next, I took my air gun and put
it next to the wing skin and spar flange while looking through the filler
cap with a flashlight. I had bubbles in four locations along the
spar/bottom tank skin mating area in the first bay. The last set of bubbles
was next to the first rib over, so I have to assume I have a leak in the
next bay over as well. For some reason, I must not have good adherence
between the tank skin and the spar flange. Before assembly, I cleaned and
scotchbrited everything with good cross hatching etc. Perhaps I had an area
such as the spar flange that never got sufficiently cleaned or something.
Don't know. I trusted the proseal, and there was an approximate 1/8" bead
evenly across the flange where it flowed out during riveting - perhaps too
much squeezed out? I didn't filet it up any more than that. I did cover
the rivet tails.

So, I have the top and bottom tank skins riveted on with a
problem on the bottom skin. Of course, the leading edge is also riveted on
in the tank area. I have two access panels, already riveted on the bottom
in the 1st and 4th bay. Ted recommended I cut holes in the upper skin,
clean with dremel and roloc pad etc., then add a large filet where I have
the leaks. In looking at it, I don't believe I have sufficient access
between the stringers to get much of a hole and allow room for an overlap
(doubler). Another option might be to enter through the last fuel tank rib
(up front), then add a doubler to it, but it would be on the outside. I
could probably reach the rivet tails through the fuel filler cap. That only
works if my problem is confined to the first bay - something I can't
confirm. If I had to remove a skin, would you remove the top or bottom?
What are the risks involved in that? I need good ideas and am going to
ponder this a while before I dig in.

If anyone wants to call and discuss, my phone is
314-791-3536.



Thanks in Advance,

Jerry Folkerts

SR 2500 #093



www.mykitlog.com/jfolkerts









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