Group,
After over 11 years of building on a Glass Goose, I may be finished. Not
finished in a good way, though. I filled my wing tanks several months ago
and was delighted to fire up my Renesis. Today, a month later, I noticed
the leading edge cap separating from the wing near the wing root and leaking
out of it. With further investigation, I also discovered leaks on the
bottom of the opposite wing at the shear web. The residue of the leaks is
yellow-tan in color and sticky. My conclusion is that the alcohol in the
gas has had an adverse affect on the epoxy. I'll call the epoxy maker on
Monday to get his words. I read about the effects of alcohol on epoxy on
the internet several years ago but was assured that it wouldn't affect a
tank that was Jeffcoed. Sealing the tank is the least of my concern. What
makes me think the wings are now unreliable is that the fuel has wicked up
into many areas of the wings' integrity so, at this time, I don't think I
can trust them. I offer this as a warning to those that can use it. Do any
of you have any ideas or words that can help save this poor little airplane.
Sandy McNabb
 Renesis in a Glass Goose (retired)

Sandy,
 What kind of Epoxy did you use, was it EZ Poxy? I am
 assuming you jeffcoed the tank based on what you wrote am I correct?
Does anyone know of any protection for composite built aircraft for the
 problem described here with alcohol laden fuel or ethanol? FYI, fuel
 bladders is not a workable solution for most composite airplanes.
James Ealey
I am interested in your reasons on why fuel bladders is not a
 workable solution for most composite airplanes. Are you speaking
 of the blue foam Rutan method?
Paul Lamar

Yes, the Rutan designs are what I was referring to with the blue foam.
 With these designs unless you get specially made bladders and you are
 will to eat the weight penalty you will
 definitely lose something that the design offers in performance.
James Ealey
Auto fuel is a 25% savings in fuel cost. I don't have a weight per square
 foot yet on the McMaster neoprene nylon material but it can't be much
 at only .022 inches thick. I'll order $5 worth and weigh it and do some
 fuel tests on it.
Custom built was what I had in mind for the fuel cells. One can hammer
 ribs out of sheet steel and use them to clamp and heat the joints.
 I suspect something like 250 F will do the job.
It will take a bit of trial and error to learn how.
Paul Lamar

James,

I have a wet wing with fuel in the whole leading edge rib sections. A few
holes are cut in the lower rib to let the fuel flow. The building plans call
for sealing the surface area of all of those D sections plus the holes. It
is a daunting task and I doubt I can accomplish it with 100% certainty.
Worst get the outer skin is added later and those joints can't not be
properly sealed.
 Since I am exploring using high ethanol content fuel, I'll be hiring
someone to weld thin 0.3mm Teflon bladders for me. With the absence of
JeffCo coating the weight increase will be nelgible. I haven't figured out
the connection method between them yet. Probably need some male/female tube
connections welded on. Bladders can be designed to collapse if desired.
Sandy, I wouldn't scrap the wings yet.  Chances are the ethanol is reacting
with the epoxy surface or remaining wax.  I don't know which type of resin
you used but some of the vinyl-esters are specifically designed to hold
solvents. Chances are good you can drain the fuel heat up the wings to 25C
and evaporate the remaining solvent out of them.
If you are concerned with the integrity of the wings, make a jig and load
test them with sand bags. After passing that test you can make a plan to add
bladders.
Water infiltrating into fuel tank depends a lot on the tank material, vent
air temp and humidity. Naturally amphibs. operate in a humid environment.
Having the wing tanks feed a low sump tank is also a good idea. Pump
pick-ups should be at least a half a gallon volume above the bottom of this
tank.
Doug in Japan


Jeffco are located in California but i am not sure if they stay in business,i personnaly use Jeffco epoxy as lining and all Velocity i builded and i dont have no informations about ethanol reaction but if someone can be in touch with Velocity they do sell this stuff for fuel lining coating they might know more about it


Jean Prudhomme