REFLECTOR: Auto fuel - composite compatibility

[Al Gietzen]

For those using, or plan the use of mogas.  I’m suspecting some fuel
compatibility issues.

 

I first put fuel in the tanks nearly 2 years ago and used Chevron regular.
Everything was fine.  When I moved the plane to the airport 3 months ago
(tanks empty) I filled with Exxon-Mobile.  Four troubling things have come
up in the past few weeks. 

 

1.	I have Vance Atkinson site gauge that has a white plastic back plate
for easier reading of the fuel level. The small hole through the backing has
been swelling shut so the sight gauge no longer works. I contacted Vance who
said that there are hundreds of these gauges in EZs using mogas without
problems, but he has had 3 incidents like mine in the last three months. 
2.	A couple of weeks ago there was suddenly a pinhole leak in one of
the gear well enclosures.  These enclosures are part of the fuel tank wall,
and are parts that come with the Velocity kit.  These are also made and
coated with EZ-poxy. 
3.	Looking in through the filler cap I see reddish-purple splotches and
streaks on those gear leg enclosures.  Poking and scratching with some
safety wire on a stick does not indicate any softness of the surface.  All
other surfaces look fine.
4.	Yesterday, under the leading edges of one of the strakes, I noted an
area with some slight surface irregularity.  Pushing on it suggests some
sponginess.  This is ½” foam core material, and indicates the possibility of
a pinhole leak in the inner skin, and fuel softening the PVC foam.  PVC foam
is supposed to be unaffected by fuel. 

 

My tanks (strakes) were made and coated with EZ-poxy back in 1998.  At the
time I polled EZ flyers about their experience, and talked to reps of
various epoxy manufacturers about auto fuel compatibility.  All the evidence
said go with the EZ-poxy (see my posting of July, 1998). 

 

I realize that his may be only my issue and not related to brand; but - -
Any others having any trouble with auto fuel?  Anybody using Exxon-mobile
fuel?  Know of any new additives that may be an issue?

 

I’m thinking I should drain this fuel ASAP, but then what?  Other brand?
That expensive Avgas?  Regardless I may be faced with cutting open a strake
at some point, but right now we are trying to get first flight done this
coming weekend.

 

Al

 

 

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