top tank skin removal

[Ron Shannon]

I've previously reported problems with leaks in 254R's tanks, including
numerous attempts to repair from the outside with suction, etc., all to no
avail. The time for surgery has come, before painting.

I was planning to cut a football-sized access hole in the bottom of each
bay and try to clean and re-coat everything inside with Pro-Seal through
those holes, as Craig and others have done. The cleaning in particular has
me a little bamboozled -- these tanks have held fuel for 17 months, or at
least held most of it. However, after Wayne's Polygone revelations,
removing the existing Pro-Seal entirely seems like it may be a realistic
option. So... I'm reconsidering removing the top skin instead, to clean
down to bare metal and re-do the whole thing, with better access and vision
than I could ever have through bottom access holes.

The question now: how hard is it to remove the top skin -- without mangling
it? This probably breaks down to A) potential difficulties removing rivets
that are smothered in Pro-Seal on the inside and B) dealing with skin
adhesion from the existing Pro-Seal.

As for rivet removal, presumably all that's needed at first is to liberate
the skin. The rivet tails can be wiggled out later as inside Pro-Seal comes
off and, if a few 5/32 rivets are needed to button up, it wouldn't be the
first time. But it seems that to open things up enough to pull the top skin
out, I'd have to also take out a few rivets outside the tank perimeter, and
leave those tails rattling around in the wing, etc. Regarding
sealant-to-skin adhesion, in the recent Polygone thread, Wayne was
encouraging about breaking the grip of the Pro-Seal by "slicing" the skin
off but... I have doubts.

Given the virtues of Polygone, I think I'd rather remove all the Pro-Seal
and re-seal the whole thing starting from clean, well-scuffed metal, with
good access and vision, by pulling the top skin. Comments, tips, and
appropriate incantations would be appreciated.

Ron




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