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

Those big tanks in the ground at the gas station are now vinyl ester.
It
seems that tanks made of vinyl ester or lined or doubled up with vinyl
ester
would do fine. Or if you have a TIG machine, or better yet, a friend
with
a TIG machine, repair the damage with whatever epoxy you built with and
make up some nice aluminum tanks. Or, race car fuel cells come in many
interesting shapes and sizes and the smaller ones are cheap enough. You
can order
the bladder without the steel can. Check out ATL
http://atlfuelcells.com/

(http://atlfuelcells.com/)

and


http://www.buycheapr.com/us/result.jsp?ga=us3&q=racing+fuel+cells


http://www.buycheapr.com/us/result.jsp?ga=us3&q=racing+fuel+cells


Lynn E. Hanover


I think teflon is over kill. I am not sure it is easy to weld. Reliable
bonding is a problem. Polyethelene is what most solvent bottles are
made
from if they are not glass. It is a well behaved thermoplastic and can
be
welded. Harbor Freight has soldering iron like tools for plastic
welding;
hot gas jet. McMaster has poly sheet in the catalog.

Murry I. Rozansky

Thanks for the harbor freight tip. I am going over there today
to get some polishing pads.

Paul Lamar

Teflon is HEAVY, Virg

Depends on how thick it is.

I got the plastic welding tool at harbor freight. Just a soldering iron
with a flat tip at 45 degrees. 500 F.

Ill try it out when I get some neoprene fabric.

Paul Lamar



Hi Paul, the one I have has a quick connect for compressed air and a
regulator for a hot gas jet. Its non contact like a welding torch.

Murry I. Rozansky


I did not see that one. Should I take another look?
I figure teflon tape will keep the neoprene from sticking
to the soldering iron.

Paul Lamar




There is a super coupon on their web site for 67102  for $12.99.  They
have two gas jet type on the web site but not the one a got a while back.

Murry I. Rozansky


I have to fetch Robin from LAX tomorrow so I'll stop by and
check it out.

Paul Lamar