Fibreglass tank repairs

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Ron Hulton

Jul 18, 2005
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I have just acquired a fibreglass Interstate tank and it would appear as if someone has tried to line the inside of the tank using fibreglass resin. I have been able to chip away quite easily what i can see and reach through the gas filler . I tried soaking a sample piece in gasoline to see if it would dissolve but no luck. I took another piece and soaked it for 4 hours in Acetone. While it did not dissolve the piece it did crumble when i tried to pick it up .. My question would be ...... How long could i safely leave a solution of acetone in the tank for before it damaged the tank composition itself? Secondly , for those who have relined their own tanks using Redkote,Caswell or any other of the sealers, could i get a suggestion as to which one may be the best and which ones to stay away from. I'd certainly be interested in anyone's thoughts or experiences in getting this resin out of the tank.

Thanks in advance
I had a similar problem with a Fastback tank that was coated with some sort of sealer that, well, did not seal. It was flaking off and the ethanol in the gas here in California was attacking both the coating and the fiberglass, causing a sticky build up on the carb slides (and the rather exciting problems that can result from this).

I took several handfuls of small 3/4 inch drywall screws and placed them in the tank and shook it for several days. This scoured out all of the old, flaking coating (it was a carmel color and was easily distinguished from the tank itself). I then coated the inside with Caswell. The instructions with the Caswell said one can was sufficient to coat two tanks, however I found using only half a can was insufficient for a Fastback tank, and ended up using the whole can. There was a bit of excess that poured out, but I feel it is bettier to overcoat and have some waste, than to undercoat.

Tank does not leak, and there is no indication that the Caswell is deteriorating to any degree. It has been almost a year since it was coated.
The Hirsch liner I used in a Norvil Fastback tank held for two and one half years. It found a pin hole somewhere and the gas did it's evil. :evil: That's the problem with liners you can't see what you are doing in unseen spots and the job is only as good as it's thinest spot. :cry: MEK is the solvent for this liner so that and drywall screws will remove it just add lots of shaking and time. I don't know if it's good for the glass as made by Norvil in the 90's though.. The tanks are rough inside and fibers can be found sticking into the air inside the tanks. It is thought that these fibers provide wicks that guide the gas to the guts of the lay ups that make up the tank. Good old stock tanks seem to have a brown liner right from the factory and no stray fibers. The only for sure fix is to cut the tank open and re-line it with Purine resin and or purpose made epoxy. Not fun, and almost the 500.00 bucks of labor towards a steel or alloy tank. Hours of time brought years of use but I choose to be done with glass tanks more for you.
Yeah, the factory glass tanks had a resin lining applied at the factory. My black tank (originally orange) had a brown or orangish colored liner. My Fireflake Royal Blue tank was lined with a blue resin. I think they used the same color as the gelcoat.

My black tank lasted two years after being professionally lined by a guy in Cali. As with Greg's tank, the fuel seems to have found some pinholes and the paint started bubbling. It might be possible to reline it but I don't feel like bothering.

I lined the blue tank myself with the Caswell epoxy. It's been two years now, and so far so good. It seems to be holding up fine to our Colorado-blend ethanol fuel. If this one craps out I have a couple of steel tanks on the shelf. They're both full of rust though and will need a fair amount of work.

One good thing about fiberglass: no rust! :lol:

I have used Caswell epoxy on a fibreglass tank and RedKote on a steel tank. Both are holding up well. I know two people who have used RedKote on fibreglass tanks with good results. (4-5 years and still tight).

The key to this is like painting. It's in the preparation. Take your time. Use small amounts of solvent with screws or nuts or chain and repeat several times rather than a large amount doing it once. Let the tank sit for a couple of days to dry out before lining and let the lined tank sit at least a week before you add fuel. It will be dry to the touch but thoroughly cured.

Debby, I'd be cleaning out those steel tanks and lining them now. If the paint needs redone, take them to a metal stripper and let them clean them inside and out, then line the inside and prime the outside. If they are already rusty, they may have holes in them by the time you are ready to use them or decide to sell or trade them.
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