Cured Vinyl ester resin is advertised to be ethanol proof. However, ethanol
with 6-percent water is a solvent for cured Vinyl ester resin. Ethanol is
hydroscopic; In vented aircraft fuel tanks the ethanol contained in most
automotive fuels will draw water vapor from the air at the top of the tank.
This hydroscopic action continues until the Ethanol reaches saturation at
6-percent water. The solvent action is slow.
In my KR-2 the Vinyl ester wing tanks started leaking before first flight.
During the replacement process with aluminum tanks, minor solvent damage was
found and repaired for the Diehl wing skins. The Diehl wing skins are also
constructed with Vinyl ester resin.
My recommendation is: Do not use automotive fuel containing Ethanol in
Vinyl ester fuel tanks. Automotive gasoline, per se, in not a problem
provided you use the proper octane for your engine. The problem is the d**n
Ethanol.
Sid Wood
[email protected]
California, MD, USA
-----Original Message-----
From: Mark Langford
Sent: Friday, August 12, 2022 8:49 AM
To: [email protected]
Subject: Re: KRnet> Wing tank fittings
Brett Lombardi via KRnet wrote:
I’m building a pair of fiberglass wing tanks and looking for the fuel tank
fittings. Have searched Spruce, Wag, Amazon, Summit Racing, etc. with too
many options. Anyone have specific advice on fittings/kits/attachments for
fiberglass wing tanks that they have used?
There are various ways of doing that, but I cut out some 1/4" aluminum
plate (same thickness as the tank walls), drilled and tapped an NPT hole
in it, and sandwiched the plate in a matching cutout in the tank walls,
then put several layers of fiberglass cloth over the plate and walls
inside and out to make it part of the tank wall (or bottom). Cover the
NPT hole before glassing with electrical tape to keep epoxy out of the
threads. That worked fine for me. There are other store-bought
solutions that have o-rings and such, but this was cheap, quick, and
required no shipping charges.
While we're on the subject, hopefully you used some kind of epoxy on the
internal glass that is impervious to ethanol so you can burn auto fuel.
The commonly used West epoxy is supposed to be fuel-proof, and there
are vinylesters that are also (but they sure do stink up the shop!). I
can send some part numbers later, if you'd like....
-- -------
Mark Langford
[email protected]
http://www.n56ml.com
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