Al,
I sure hope this stuff works because this
is what I used to seal the fuel tanks on my Lancair. Jeffco 9700 is what
Lancair specifies, and supplies in their kits. I’ve had mogas in my
right wing for about 8 months now with no sign of leakage. It would be extremely
difficult (if not impossible) to coat the fuel tank after the wings are closed.
Mark S.
From: Rotary motors in
aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Steve Brooks
Sent: Monday, July 31, 2006 12:39
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Auto Fuel
- composite tanks
When I built my cozy, the EZ-poxy was also
recommended for the strakes. Since I used MGS to build the entire plane,
I really didn't want to use the EZ-poxy to build the strakes. For one, it
would have different curing tendencies, and secondly the specifications of the
MGS indicated that strength wise it was a much better epoxy.
After some research, which also included
using products already tested by others before me, I elected to coat my fuel
tanks with a product made by Jeffco. Specially, Jeffco SPF9700-FCR.
I built the strakes using MGS, and then coated the interior with the Jeffco
epoxy.
I'm not sure how difficult it would be to
coat the tanks with it now, but it is impervious to most fuels, and their
various additives. I've had fuel in my tanks for almost 3 years
now. Various different gas stations, and no problems at all with the
tanks.
I don't know how hard it would be to coat
your tanks now, but it most likely would solve your problem. You just
paint the stuff on after mixing it up. It's pretty thick, and tends to
stick pretty well to vertical surfaces. As I recall, I gave mine 2 or 3
coatings. I had zero leaks when I pressure tested the tanks.
-----Original Message-----
[Steve Brooks]
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On Behalf
Of Al Gietzen
Sent: Monday, July 31, 2006 1:15
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Auto Fuel -
composite tanks
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.