Hi Sid. I built my fuel tank with vinylester also. My plane got water
in the tank( Gas cap seal broke )during a 5 day move from Montana to
Ohio. After emptying the 100 low lead from the tank, I used auto gas
from a can for my mower, to rinse out any remaining water. In drying
the inside of the tank, after that, I found the rag sticking to the
inside of the tank. The vinylester resin had softened and was sticky
and gummy on the surface, much like it was laid up hours ago. I left
the tank open for a week or so, and it was no longer sticky. I have
only used 100 Low Lead before this, and ever since.
-----------------------------------------From: "Sid Wood"
To: m...@n56ml.com, krnet@list.krnet.org
Cc:
Sent: Friday August 12 2022 11:54:55AM
Subject: Re: KRnet> Wing tank fittings
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
smw...@md.metrocast.net
California, MD, USA
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