Tank sealer on my fiberglass tank?

[CJF]

I have a fiberglass tank for my race bike project and I'm wondering if I need to seal it. I have seen so much different info on whether this needs to be done and what products should be used. The place I bought the tank from said that it was made to allow for pump gas to be used in it, but I'm not sure I want to find out they were wrong. Anyone heard of certain types of fiberglass not needeing to be sealed?

[Buffalo-guy]

From what I understand, the newer generation resins can withstand the high percentage ethanols and alcohol in today's fuel. The older style fiberglas in my 73 Duc, started weeping after one years exposure to today"s gas. My Italian bike expert friend, says that Caswell sealer is the way to go. Easily attainable. I got mine on line. Hope this helps. Cheers.
Fred

[diamondj]

Polyester resin used for tank construction typically won't stand up the the ethanol content in pump gas. Epoxy resin usually will. Trouble is you can't usually tell which resin the tank mfg used until your tank starts to weep gas. True race gas should not have ethanol in it. I have also heard good things about the Caswell sealer when used in a fiberglass tank as well as KBS:

http://www.caswellplating.com/aids/epoxygas.htm

http://www.kbs-coatings.com/Gold-Standa ... _39-1.html

Sealpak sells tank sealers for airplanes and can sell you a kit for a motorcycle tank but they are VERY expensive:

http://www.sealpakcoinc.com/welcome.htm

Jim

[tz375]

Some of the Sunoco race gas blends use ethanol as the oxygenator.

[ja-moo]

I was under the same impression that the epoxy sealers weren't effected by the ethanol. As I have been using vinyl ester epoxy resin on the tanks I build. And it has worked fine for years. Untill last year, when it seems the gas companies changed their formulas and I found that even the vinyl ester was softening up, so now I an sealing my tanks.

I have used POR 15, KBS and the Caswell. The POR 15 and KBS seem to be pretty close in make up and takes quite a while to "set" with forced air recommended. (a few days)

The Caswell is a 2 part that sets in 30-40 minutes. (at 70 deg) It is a lot thicker, so takes more time to get everything coated. I haven't seen it in action as I just coated a tank, but I don't see any reason it won't seal as well as the other 2 sealers.

[krwalsh]

Some of the epoxies will be softened by ethanol, and unless you know which resin your tank was manufactured with, you won't know until your tank starts leaking or you start getting goo in your carbs. You have a couple choices: never use fuel with alcohol, or coat the tank. The ethanol is hard to avoid, as you may not know you're buying it. So, unless you know you'll always use race fuel that is alcohol free, I'd coat the tank. The POR products work, but for fiberglass airplanes they typically slosh the tanks with a product called Jeffco 9700.

[tz375]

http://www.aircraftspruce.com/catalog/a ... cotank.php

the $542 for 3 gallons to coat a complete plane is a bit much though.


They also list this stuff
http://www.aircraftspruce.com/catalog/appages/bunan.php

At only $94 a pint.....

I used to use an ISOPHTHALIC RESIN like this:http://www.mertons.com/Epoxy/polyester_ ... halic.html when I made tanks for Methanol.

They still went soft over a weekend but didn't seem to leach out.

From what I have read, it looks as if vinylester resins may be more corrosion resistant. Any Chemical Engineers here to shed some light on this.

[CJF]

It looks like sealing the tank is the way to go for me based on everyone's feedback. Now, what to use?

I guess the options are epoxy sealer or this other option used on aircraft. The lower cost option for $94 looks like it is a "synthetic rubber" based on the product description. I have definitely heard of others using the epoxy coatings mentioned, but this is the first I have seen the synthetic rubber coating.

Anyone know the difference between airplane fuel and other fuels? Wondering if this synthetic rubber coating may be better way to go than epoxy, but not sure if it would just be good for airplane fuel.

[krwalsh]

For "airplane fuel" you're basically talking about 100LL. It is 100 octane, low lead, or avgas. It never has alcohol in it, which is typically the gremlin that gets you on composite tanks. The tanks on our plane (hell, the whole plane!) are made of fiberglass and epoxy. The key being the epoxy (EZPoxy, in this case) is fine with Avgas. It has been reported as also fine with mogas, although the levels of alcohol it can tolerate is somewhat of an open question.

[CJF]

I ordered the tank sealer from Caswell. I'm thinking I'll coat the gas tank and the integrated oil tank in my seat just to be safe. The parts are too damn expensive to melt away. Thank for the advice.