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