Al, I've had mogas in my tanks for 8 years and flying for 7. I even burn 10% ethanol mogas in the winter. EZ-Poxy II (was Safety-Poxy II). I recently had my first leak, a pinhole near the very bottom of the left fuel sight gauge. I attribute it to leaving the plane out in the sun with no cover, as I've been flying to work almost every day this summer. Normally it is hangared during the day except when flying. It was easily repaired by draining the tank, roughing up the surface a little including the plexiglas, and applying some epoxy. I didn't even apply a slight vacuum to the tank. I probably will replace the sight gauges sometime in the near future. So now I'm taking the extra time to put the cover on the plane, mainly just to keep the direct sun out of the cockpit. --- Not sure where to go with this because there are only a few here with epoxy fuel tanks, and on the Velocity list very few interested in the use of mogas. I’m suspecting fuel compatibility
isses.
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.
- 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.
- 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.
- 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.
- 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 there experience, and talked to reps of various epoxy manufacturers about auto fuel compatibility. All the evidence said go with the EZ-poxy.
Any others with composite tanks having any trouble? Anybody using Exxon-mobile fuel? Know of any new additives that are 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.
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