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.
When I was about to close the strakes 8
years ago (could it be that long?), Jeffco was just beginning to be used for
sealing strakes. It has since become the standard for Velocity. At the time,
one of the people I had talked to was a chemist at Composite Design Company,
makers of EZ-poxy. She was doing studies comparing EZ-poxy with Jeffco and
West Systems; and assured me that EZ-poxy had equivalent or better fuel
compatibility than either of the others. She may have been biased, and that was
then and this is now, but in any case, with the good experience of long term
use in EZs, I stayed with what I had.
I can’t imagine cutting open the
strake to coat with something else at this point.
Al
-----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.
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.
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
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.