Fiberglass Tip Tanks Question

Got a problem here, and I'm wondering if anyone else has run into it before.

Five years ago (or so) the previous owner of our Cherokee 235 repainted the
fiberglass wingtip tanks.

Apparently he had an automotive body shop do the fiberglass work, and around
the filler necks they used a fiberglass that was NOT impervious to gasoline.
Thus, the fiberglass resin turned kinda mushy, and little chunks of it
started coming out. Paint wouldn't stick to it, and it just generally
looked like crap. Eventually it could have become an airworthiness problem,
as the filler necks might have come completely out of the fiberglass.

My A&P has now dug out all the gooey fiberglass, and replaced it with a
gasoline impervious epoxy-based filler. After sanding, it looks PERFECT,
and I have just purchased the paint ($80 a PINT for Imron now!) to paint the
tops of both tips.

Question: In another aviation forum, someone mentioned that the gasoline
vapors can actually go THROUGH fiberglass, and get at the underside of the
paint. It then works on the paint from the underside, softens it, and the
surface starts to break down.

If this is true, then what I have done will only solve the problem right
around the filler necks. Has anyone ever heard of this? Did I fix the tip
of the iceberg here? Is there a better "fix" for the problem than what
we're doing?

Thanks!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On 23-Sep-2003, "Jay Honeck" wrote:

Question: In another aviation forum, someone mentioned that the gasoline
vapors can actually go THROUGH fiberglass, and get at the underside of the
paint.


Jay,

This sounds like a bit of aviation-style urban legend. If the gasoline
molecules could penetrate the fiberglass then the tanks would "seep". It's
the same molecules whether in gas (vapor) or liquid state. I think you are
OK.

--
-Elliott Drucker

Jay,


Not sure I have ever heard of fiberglass that was not fuel resistant.
Most glass resins I have ever heard of are polyester based and
definitely hold up against most fuels (chemists please feel free to
chime in). More likely there was a blending/curing problem or they used
some old resin that had a contaminant or moisture problem. If the
catalyst proportion was too low and/or the temperature during the cure
was low, there may have been a very slow cure period. Once fuel or other
solvents gets to glass that is not fully cured, it will start to
delaminate (as you described). However, even in this case, the mix
usually hardens way before you ever gas up since it takes some time to
prepare for paint, paint, mount, and then refuel. Most I have seen a bad
mix take to cure is 12 hours or so. If it took any longer, one usually
starts over and scraps the first attempt.

Another possibility is that the tank actually contained fuel during the
process. Don't laugh. I have seen similar situations. Fumes from the
fuel will disrupt curing and cause all sorts of ills as they get
absorbed in the resin.

You wrench used epoxy-based filler? New one on me. I never knew that was
approved for use on fuel tanks. After sanding I'll bet the old
fiberglass job looked perfect too! Time will tell.


Mike

Jay Honeck wrote:
Got a problem here, and I'm wondering if anyone else has run into it before.

Five years ago (or so) the previous owner of our Cherokee 235 repainted the
fiberglass wingtip tanks.

Apparently he had an automotive body shop do the fiberglass work, and around
the filler necks they used a fiberglass that was NOT impervious to gasoline.
Thus, the fiberglass resin turned kinda mushy, and little chunks of it
started coming out. Paint wouldn't stick to it, and it just generally
looked like crap. Eventually it could have become an airworthiness problem,
as the filler necks might have come completely out of the fiberglass.

My A&P has now dug out all the gooey fiberglass, and replaced it with a
gasoline impervious epoxy-based filler. After sanding, it looks PERFECT,
and I have just purchased the paint ($80 a PINT for Imron now!) to paint the
tops of both tips.

Question: In another aviation forum, someone mentioned that the gasoline
vapors can actually go THROUGH fiberglass, and get at the underside of the
paint. It then works on the paint from the underside, softens it, and the
surface starts to break down.

If this is true, then what I have done will only solve the problem right
around the filler necks. Has anyone ever heard of this? Did I fix the tip
of the iceberg here? Is there a better "fix" for the problem than what
we're doing?

Thanks!


__________________________________________________ ____________________
Posted Via Uncensored-News.Com - FAST UNLIMITED DOWNLOAD - http://www.uncensored-news.com
The Worlds Uncensored News Source

You wrench used epoxy-based filler? New one on me. I never knew that was
approved for use on fuel tanks. After sanding I'll bet the old
fiberglass job looked perfect too! Time will tell.

Thanks for the advice on the tanks. I wasn't aware that epoxy-based fillers
might not be approved for fuel tanks.

I think the reason he used it was that it is so fuel resistant throughout
the hardening process. Because of this property, he was able to fill the
voids in the fiberglass without having to drain the tanks, which saved
significant time and effort. There were no holes that went all the way
through to the gasoline compartment itself. Because I caught the problem
early, the repairs were considered a cosmetic repair rather than an
airworthiness issue -- perhaps that's the difference?

Our A&P is an EAA'er from way back (he's built several planes), is a
lifetime member (and former Grand Champion winner) of the Antique Aircraft
Association in Blakesburg, and a member of that elusive group known as the
"Quiet Birdmen". He is also the guy who rebuilt our O-540 last year. To
say I trust the guy implicitly would be an understatement -- but now you've
got me wondering.

I think the reason the fiberglass degraded goes back to a poor job being
done five years ago. I spoke with the guy who sold the previous owner the
plane (our plane is one of those gems that never seems to leave the
airport -- it just gets sold "internally"), and he said the tips were a
point of contention at the time of sale, because they had some hangar rash
and scratches on them. The seller agreed to re-do them (he owns a body
shop), but -- when the buyer removed the tips and tried to have them re-done
without any advanced warning -- the seller was unable to get to them right
away. (His "Corvette guy" was on vacation, or something...)

In a huff, the buyer took them to an out of town body shop, owned by a
friend, who did them right away. Apparently the seller didn't think too
highly of this shop, or their reputation -- so I guess I can believe trouble
was brewing from the get-go.

Well, anyhow, next step is paint. We'll see how long it holds up. (At
least now it's been done by a guy who will stand behind his work...)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Mike Spera wrote:

Jay,


Not sure I have ever heard of fiberglass that was not fuel resistant.
Most glass resins I have ever heard of are polyester based and
definitely hold up against most fuels (chemists please feel free to
chime in).

Polyester resin can not be used with fuels. The wing skins of
my Aerocomp are made with polyester resin. The wet portions
of the wing are exposed to fuel and have to be coverd with
fiberglass mat and vinylesther resin.

"Mike Spera" wrote in message ...
Jay,


Not sure I have ever heard of fiberglass that was not fuel resistant.
Most glass resins I have ever heard of are polyester based and
definitely hold up against most fuels (chemists please feel free to
chime in).

I('m not a chemist, but there are evidentally some out there. I have
a small leak in my tip tank (which itself is metal) but it is disolving
the fiberglass fairing.

Jay,

Just because I have not heard of it being approved does not mean it
isn't. Could very well be. The home builders know WAY more than I do
about epoxy fillers (like 100% more than me). Besides, who cares if it
is approved or not if it holds up? Sorry for the overly strong reaction.

That tank repair will probably outlast the plane....

See Ya,
Mike

Jay Honeck wrote:
You wrench used epoxy-based filler? New one on me. I never knew that was
approved for use on fuel tanks. After sanding I'll bet the old
fiberglass job looked perfect too! Time will tell.


Thanks for the advice on the tanks. I wasn't aware that epoxy-based fillers
might not be approved for fuel tanks.

I think the reason he used it was that it is so fuel resistant throughout
the hardening process. Because of this property, he was able to fill the
voids in the fiberglass without having to drain the tanks, which saved
significant time and effort. There were no holes that went all the way
through to the gasoline compartment itself. Because I caught the problem
early, the repairs were considered a cosmetic repair rather than an
airworthiness issue -- perhaps that's the difference?

Our A&P is an EAA'er from way back (he's built several planes), is a
lifetime member (and former Grand Champion winner) of the Antique Aircraft
Association in Blakesburg, and a member of that elusive group known as the
"Quiet Birdmen". He is also the guy who rebuilt our O-540 last year. To
say I trust the guy implicitly would be an understatement -- but now you've
got me wondering.

I think the reason the fiberglass degraded goes back to a poor job being
done five years ago. I spoke with the guy who sold the previous owner the
plane (our plane is one of those gems that never seems to leave the
airport -- it just gets sold "internally"), and he said the tips were a
point of contention at the time of sale, because they had some hangar rash
and scratches on them. The seller agreed to re-do them (he owns a body
shop), but -- when the buyer removed the tips and tried to have them re-done
without any advanced warning -- the seller was unable to get to them right
away. (His "Corvette guy" was on vacation, or something...)

In a huff, the buyer took them to an out of town body shop, owned by a
friend, who did them right away. Apparently the seller didn't think too
highly of this shop, or their reputation -- so I guess I can believe trouble
was brewing from the get-go.

Well, anyhow, next step is paint. We'll see how long it holds up. (At
least now it's been done by a guy who will stand behind his work...)


__________________________________________________ _____________________________
Posted Via Uncensored-News.Com - Accounts Starting At $6.95 - http://www.uncensored-news.com
The Worlds Uncensored News Source

That tank repair will probably outlast the plane....

I sure hope so!

Thanks for the good advice, as always...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"