wing" integral aircraft tanks are plagued with seepage or worse at some
point in their lives, in Rebels and everything else. My plans:
First, I'll again review all the discussions about sealing tanks in
general, including Wayne's recent detailed suggestions, comments about
suspect areas, etc. Among his many other points, for new construction, I
liked his idea of putting in access ports even before the bottom skin goes
onto the wing, anticipating a need to get in later, but doing a more
certain job of sealing the ports while it's easy to get at both sides,
including the "bath tub" phase before the top goes on. (As noted before, I
didn't have the joy of building my original tanks.)
Before cutting ports (any day now) I have rinsed the insides with a mild
degreaser in warm water, mostly to assure all fuel is out, then warm rinsed
and blow dried that (with a heat gun far away, blowing warm air through a 5
ft. long 1" polyurethane tube, duct taped into the filler neck) realizing
that the real good cleaning will have to wait until after I'm into the
tanks and done with machining.
My plan is to do the machining with the wing off, on a table, bottom side
up, of course. When cutting and drilling, I'll try to get a "bib" or
"napkin" inside under the work area as soon as possible in the process, to
catch as much of the cutting and drilling filings, etc., as possible. I'll
remove, dip and reset a couple of bottom rivets that are still suspect,
forcing Pro-Seal into the holes to capture the old rivet tails, dipping the
new rivets.
Once the port holes are cut, I'll clean everything inside as much as
possible (lint-free processes, of course) then do good surface prep of
exposed metal around the edges of the existing Pro-Seal, and making sure
everything is as clean as possible again before applying PR-182 adhesion
promoter to the existing Pro-Seal. (See PR-182 at *
http://tinyurl.com/6rjz2ft* for example.) Then I'll apply another layer or
two of Pro-Seal over everything, with particular attention to suspect
locations, filleting out over the prepped bare metal. Finally, I'll
overcoat everything with the less viscous, brushable Pro-Seal Type A top
coat.
To close up, I'll make sure all parts, surfaces, rivets and clecos are
properly prepped. I plan to close up the doublers and covers with the wing
turned over again right side up, bottom down, working from the bottom side,
below. I will knock myself out covering and dipping everything through that
process, and will also use adjacent-bay ports to make sure the neighboring
ports are well covered and brush top coated from the inside. (Getting
around the baffles may be problematic, but....) The outboard port under the
filler neck will be done last, so I can attempt to add a brushable top coat
through the filler neck even on that one.
Of course, throughout I will observe temp and curing controls and
frequently apply secret incantations, make fervent appeals to various
deities, etc. I'll probably wait at least 10 days for a good cure (all the
while taking large doses of anti-anxiety medication) before air testing,
then final rinse and dry, check finger strainer & sump fittings, etc.
Or something like that. Then I'm going to paint the whole thing,
reassemble, and [gasp!] re-weigh, of course. Should be flying again
sometime before 2013. :-(
Ron
On Tue, Jan 24, 2012 at 10:51 AM, Roland Kriening <kriening@rogers.com>wrote:
I like the idea of access ports and would also go with CNC cut plates, if
only they didn't want to charge me over $100 for shipping. Seems once they
sense a border crossing, the opportunity to make some extra money grabs
hold. So much for living on the same continent.
Seems like an academic yet simple question Ron, but how would one ensure no
leaks from the six new plates. I always try to think things through
thoroughly before cutting (learned the hard way $$$). Cutting into the
bottom of a tank really scares and newbie like me. I really like your idea,
but I do see a lot more proseal in my future. Can you share your thoughts.
Perhaps I am over thinking this again.
Roland
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