REFLECTOR: EZ poxy & ethanol

[Al Gietzen]

I suspect the story is likely more complicated than this on failed or that
one did not.  Way back when, about 1999, as I was completing my strake tanks
the issue of auto fuel compatibility came up, and Jeffco was being suggested
as more chemically resistant.  At that time I drew upon the experience of
EZ-flyers that had use mogas for many years.  I also discussed with a
chemist at whatever company was making the EZ-poxy at that time.  The result
was that I chose to stick with the EZpoxy.

 

The chemist (who I recognized may have been biased) was confident that the
EZpoxy was just as chemically resistant as any other epoxy system available
- under the same conditions. One factor that was important was that any post
cure above the typical room temp of about 70F improved the chemical
resistance. Before there was ever fuel in my tanks, I'm sure there were many
hours on exceptionally warm days that the temp was about 100F in the shop. 

 

I raised the question of coating with Jeffco.  She pointed out that the
adhesion of the coating was purely 'mechanical'; there would be no chemical
bond - and on that basis the risks were greater of the coating peeling than
any risk of damage to the EZpoxy.

 

So just as the stability of the EZpoxy has some dependence on post-cure; the
stability of a Jeffco coating can depend on the preparation of the surface.
Clearly a thoroughly roughened (course grit paper) surface; everwhere - and
a thick coat of Jeffco that has some strength of its own would be a
precondition to success.

 

My decision came before the ethanol mandate; so at that time the MTBE was
one of the question marks. And there are other additives that we don't even
know about, which may depend of the brand of the fuel. I know of a Long-EZ
flier that used auto fuel with 10% ethanol in major brand fuels for 10 years
without a problem.

 

The one issue I've had was the white plastic backing in the site gauge
softened and swelled, plugging the holes to the tank.  I went to the trouble
of installing the little metal eyelets provided as a cure, but that was only
a temporary solution.

 

I wouldn't go so far as to say that ethanol is not a concern; but I think
levels of 10% or less have been pretty well proven not an issue with EZpoxy.
Here is a link to listing of sources for gasoline without ethanol. Perhaps
there is one near you (but you're out of luck in California).  

http://www.pure-gas.org/

 

Al

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