a case where you're just trying to bare a spot I think you could tape it off
and gel the area you want.. scrape and then rinse well WITH WATER without
effecting too much beside it.
I generally fix most tanks from the outside, when I find a leaking lap seem,
with great success by cleaning the entire joint area as well as the entire
perimiter of the effected tank bulkhead to skin area and lay up a fillet
around the entire thing. It's just trying to get the area clean enough to do
so while working thru a limited access hole you've cut out of the lower wing
skin. This stuff Polygone might be the ticket for that. If you've got a
really bad tank and you're already inside a tank and trying to clean it up
to reseal, I don't think it would be real issue as to what it did to the lap
joints as long as you rinse the heck out of it once you have things clean.
The stuff stops working after 4 hours anyhow according to the product info
and is organic based, unlike paint stripper that can continue to work for
ever when it gets in places you don't want it. In a tank that bad the
correct approach..... you'd have already drilled off the top skin. Lay the
Polygone to the entire thing and then get it all cleaned up and rinsed.
Scotchbrite the hell out of every rib/bulkhead flange and mating skin areas,
clean with acetone and then butter everything with Proseal coming off every
flange and out onto the tank skin and filleting the unflanged rib sides.
With them filleted on one side to the skin, buttered to the skin on the
flange side and all the rivets coated over, it doesn't matter how good the
seal is under the flange. Build your "bridges" to fill the stringer cutouts
on the outboard solid rib and all your corners and let that tack and then
lay down the top skin with a nice rim of new Proseal dipping all the rivets
as you go.
----- Original Message -----
From: "Paul Michel" <n616pm@gmail.com>
To: <rebel-builders@dcsol.com>
Sent: Wednesday, November 23, 2011 10:03 PM
Subject: Re: [rebel-builders] Polygone - Proseal Polysulfide eater! Product
Review
Wayne
Did this stuff seem to work its way into the lap joints also? Should it
effect the integrity of any seal between the numerous pieces of tank
structure? I guess in your problem that wouldn't matter but in a clean
and
reseal it may.
Paul in Sunny North Florida
On Wed, Nov 23, 2011 at 7:38 PM, Wayne G. O'Shea
<oifa@irishfield.on.ca>wrote:
Was into a real mess on this wing tank fabrication that I'm currently on.
The previous builder had built wet tanks.. skipped a LOT of attention to
detail and gave up on trying to fix leaks years later. They cut all the
rib
and stringer structure apart and installed fiberglass tanks, leaving the
wings with no compression or tension strength in the first 3 bays, which
unfortunately had the new aircraft owner in a terrible place. In between
that work they had tried the sloshing compound fiasco and it was
everywhere
as well. It was bonded REAL nice to all the flat surface though, but of
course it will never seal gapping holes or skin overlaps that were never
prosealed in the first place.
So once I had the wings all torn apart... the tanks out, wing ribs
removed..
top and bottom tank skins gone and wing skins cut back.... rear fuel tank
bulkheads tossed in the big round can, I still had a pair of main spars
and
their skin overlaps coated in all this crap. So while browsing ACS to
order
some new Proseal 890B-2 I noticed a product called Polygone..........
"PolyGoneT stripping agents are unique formulations that remove
polysulfide
(PRC) and silicone RTV sealants from metal, ceramic, and some plastic
substrates. The top polysulfide producers include PRC DeSoto (now PPG),
AC
Tech, and Flamemaster. The top silicone producers are GE, Dow, and
Wacker.
Both polysulfide (polysulphide) and silicone RTV are difficult to remove
completely since they actually bond into surface/substrate. The
typically,
sealant removal method requires scraping that results in damaging the
substrate. There are also products that try to "disslove" the sealants
but
due to their inertness, this does not work. PolyGone however, reacts with
the polymers chemically and breaks them down so they can be rinsed away
without damage to the surface/substrate. This offers significant
advantages
over other removal methods. PolyGone emulsifiers are specialty blended
chemistries that wet and penetrate the polymer and relatively quickly
emulsify it. This emulsification prevents redeposition of the reaction
by-products and allow for water rinsing"
Figured what the hell, I'll give it a try and if it saves hours and hours
of
labour trying to mechanically remove the mess.... or risking my eyes to a
gallon of MEK then the $210 per 5 lb pail of the stuff would be a great
investment. Well today and yesterday I gave it a whirl. I brushed on the
gel
(that stays absolutely in place even upside down) and then poked it
around
with the brush every 30 minutes as per the directions. This stuff doesn't
just lift the sealer it actually emulsifies it and pulls it up out of the
aluminum pores. After about 4 hours I used a plastic scraper to remove
the
majority of the sealant and slosh. Stubborn spots I recoated and left
overnight. Today I scraped most of that off easily and a few spots needed
another splash of remover and about an hour later I had everything
looking
like shinny new aluminum ready for a good scotchbrite crosshatch and new
parts to rivet / seal in.
The nice thing is that this stuff has no odor or fumes and it can be
rinse
with water if you like (or you can use acetone). It also eats and removes
epoxy primer, as you can see in the pictures where the third bay was
painted
and not part of the original 2 bay wet wing.
Never again will I fight like mad, trying to mechanically remove the
proseal
from a badly prepped area of skin / rib or bulkhead to fix a tank. Even
at
a
cost of $210, for a 5 pound pail, I figure I saved the customer at least
double that in labour by using it. Now that I've seen how far it went, I
probably could have got away with about 3 x 6oz packs @ $21.50each.
instead
of the 5 lb pail. Oh well... if someone has a spot they need to clean
send
me an email and I'll put some in a heavy ziplock container or similar for
you. It has a one year shelf life, if kept cool and in the dark.
Before..
http://www.irishfield.on.ca/gallery/polygone1.jpg
The stuff...
http://www.irishfield.on.ca/gallery/polygone.jpg
Stuff starting to eat..
http://www.irishfield.on.ca/gallery/polygone2.jpg
http://www.irishfield.on.ca/gallery/polygone3.jpg
http://www.irishfield.on.ca/gallery/polygone4.jpg
After first scrape...
http://www.irishfield.on.ca/gallery/polygone5.jpg
Second coating..
http://www.irishfield.on.ca/gallery/polygone6.jpg
A little plastic persuasion..
http://www.irishfield.on.ca/gallery/polygone7.jpg
After wiped with Acetone..
http://www.irishfield.on.ca/gallery/polygone8.jpg
Regards,
Wayne
PS... and yes Gary you can use it if you need something for the RF
magazine!
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