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Epoxy - auto fuel compatability


I have seen in the past on these postings (and perhaps in VV?) mention that
our standard EZ poxy (or various equivalents; safe-T-poxy, epolite) are not
the best for use in fuel tanks, particularly if the use of auto fuel is
contemplated.  Auto fuels have certain additives which raise the issue.
Having recently decided to use an engine which prefers auto fuel, I had the
immediate question of whether I needed to cut open my already completed sump
tank and re-coat with something; and the later question of what to use in my
main tanks.

I first raised the question with the best experts I know on the subject - EZ
fliers.  At our local EZ-squadron meeting I gathered:

1.  One pilot has been using auto fuel for 13 years in tanks made with the
original RAF (Rutan Aircraft Factory) epoxy, early equivalent to E-Z poxy,
safe-T-poxy. etc.; and has no difficulties or indications of any kind that
there is any problem.

2.  Another pilot used what was then called E-Z poxy and has 10 years of
trouble free use of auto fuel.

3.  A third pilot who used what was then called safe-T-poxy and has used
auto fuel for 7 years with no indications of any sort of problem.

4.  Word was that another pilot not in attendance had used the early RAF
epoxy system and has used auto fuel for 17 years.

I talked to the guy at Jeffco who believed their system 1307LVand either
3102 or 3179 hardener was fully compatible with auto fuel, but cautioned
that it would not bond chemically with the E-Zpoxies so surface prep for
coating was very important; i.e., sand thoroughly.  The guys at the EZ
meeting raised an important point that coating with anything different
system raised the additional issue of the possible disbonding of the

West Systems recently published (I don't remember now exactly where) that
their 105/205 system had excellent long term fuel compatibility.

The chemist at Composite Design Company (who now makes E-Z poxy) said that
her studies have included both the West system and Jeffco.  She believes the
E-Z poxy is equivalent or superior to both for chemical compatibility, and
specifically recommended against using Jeffco; particularly used as a
coating.  She may be biased, but I concluded; quite knowledgeable.

My conclusion, FWIW: leave my sump tank as is, and continue with E-Z poxy
for the main tanks.  Recognize that refiners may recently have, or will,
start using some additive which has yet-to-be-determined effects, so be

Happy building!  I've got to get back to fitting those doors.

Al Gietzen  RGE