Subject: sealing fiberglass fuel tanks
From: rotaryeng
Date: 9/19/2012, 7:05 AM
To: AAAA Put this in the To box

 I am off the tax thing for a bit- I get too wound up thinking about it. So,
 back to my therapy- my Wheeler.

 I bought the kit with the wings closed up but far from complete. I have
 been working on the wings, and yesterday set the wing up in the 5 degree
 position it will be in while on the plane.
 I filled the tanks with water (yes water) to see if they would leak. They
 did in a couple of places. It took about15 hours to leak out 40 gallons. 3
 gallons per hour is a lot.

 The water came from the ribs at the ends of the tanks, where the ribs are
 joined to the top and bottom skins. It leaked around the ribs.

 Have any of you had experience with the epoxies and do they work? I will no
 doubt have to open up access holes in the top of the wings, but I want to
 know what the fix is before I get started.

 I can build a jig that will let me rotate the wings so if I get the epoxy
 inside I should be able to rotate the wings for the 40 minute cure time and
 coat the inside of the wings. This would have the added benefit of another
 layer of protection from ethanol if for some reason the fuel gets
 contaminated with ethanol laced mo-gas.

 FYI I used water because I feared that this would happen. I can evaporate
 the water easy enough, but fuel residue is hard to remove, and I would have
 hated to have had multiple leaks at 4.00 a gallon. I didnt want to use
 pressure because it might damage the wing, and vacuum wouldnt tell me where
 the leaks are. As a former utility contractor, I can tell you that a bit of
 food coloring in water will tell you where a leak is soon enough. For big
 pipes, Tidy Bowl blue works wonders.  I have spent 1/4 of my time since I
 got the plane re-working what was done before I got it. While the closed up
 wing saved some time, I would have preferred to have closed them myself.

 Anyway, if any of you have experience with the sealers, I am all ears.

 Kevin Alderman

Hi Kevin I'm no expert as i am working under the guidance of experienced
builders at my build centre and i closed out my wings less than 2 weeks
back but from what I remember them saying, if there are leaks (we haven't
pressure tested my wings yet) what you can do is close up the tank and put
a vacuum to it at the cap. Then mix up resin and aerosil

Then you go around listening to wherever you hear the air being sucked in
to the tank and smear your resin and aerosil mix and let it be sucked in
partially then reduce the suction. Repeat as necessary once dry. Speaking
of dry, you must make sure all water is evaporated from your water testing
or it will screw up your tank patches.

If you want ethanol resistance then you can use Ashland Hebron 998 resin
and mix that with the Aerosil, or use regular Ashland Herron 992 resin if
you not planning to make the whole thing ethanol resistant. These resins
are vinylester, you must check compatibility with what ever you are using
on your plane.

 If you are planning fully ethanol resistant tanks you will need to at
least 3 coats of 998 everywhere throughout the entire tank, and I think the
biggest issue will be sanding down your tanks insides for a good bond if
you retroactively go through your wing top skins,

Good luck

Alex Molteno

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