Best product to line fiberglass tank

Fast Eddie said:

They get them made, to their spec. One difference from others is in how they mount to a Dresda modified frame.

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Pray tell?

Matchless said:

Pray tell?

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They weld brackets to the frame and bosses to the tank and use rubber bobbins.

They’re also made using racing experience, so I’d have a lot more faith in one lasting than something knocked up ‘elsewhere’ …

The problem with sealant in a fibreglass tank seems to be at the filler cap
A mate of mine successfully sealed his fastback tank only to find the fuel and maybe the vapour?
Had got between the tank and the liner at the filler cap neck
Then it had crept it's way down blistering the tank
Perversely it never leaked,I believe the liner was still intact when the tank around it got destroyed
He gave up and bought an aluminium fastback tank from RGMs

...2 weeks late, but i have sealed my Ducati fiberglass tank with Caswell half year ago: so far no problems. LMK if you have questions about the process.

Tornado said:

CASWELL has a good reputation, at least in steel tanks. It is an epoxy resin based sealer. Epoxy resins are generally highly resistant to fuel and ethanol. But the sealers need to make a strong bond to the surface. In an old glass/ polyester resin tank, there are a decades of contaminants builtup on and in the tank surface. The surface needs to be abraded and washed multiple times to help expose clean material and roughen up to permit a good secondary/mechanical bond with the fresh epoxy sealer.
Lots of wood screws, lots of shaking or tumbling an hour or more of whole tank in a cement mixer or even household dryer, wrapped in a duvet or big peice of open cell foam, should do it. Keep going until you see clean material inside. Flush thoroughly with isopropanol or other high flash point surface prep cleaner. Dry completely, hairdyer or sunlight on warm day etc. Proceed as per sealer directions, but Id skip any metal etching treatment steps.

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I have built a few surfboards in the past, one additional thing to add: just before sealing with Caswell, do another last Acetone rinse. It makes the old resin tacky, and that enables a chemical bond with the fresh resin, instead of just a mechanical bond.

Marian said:

...2 weeks late, but i have sealed my Ducati fiberglass tank with Caswell half year ago: so far no problems. LMK if you have questions about the process.

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Your method involves a black cat eh? Very cunning!

I have used Caswell on multiple fiberglass tanks.
I have two over 5 years with no issues.

_V_ said:

UPDATE: getting an alloy tank.

Fiberglass tank will be for display purposes in the garage.

Thanks to everyone for responding.

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If you slice it down the middle it will mount up nicely on the wall.

Son of Siredward said:

I have used Caswell on multiple fiberglass tanks.
I have two over 5 years with no issues.

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I have used Caswell a number of times but only twice on fiberglass tanks, Once was on a newer tank and the coating seems to be holding well.

The second use of Caswell was less successful with the coating failing in use. This was an original 20M3 tank that had already started to leak badly. I used the Caswell generally as per instructions including cleaning the inside thoroughly with sheet metal screws and acetone several days before applying the coating. I suspect I should have done this closer to application of the coating. The second mistake was that I removed the plugs I used on the petcock holes while the coating was still somewhat pliable but forgot to run a tap though the hole until the following morning when the coating was quite hard. I suspect I chipped the coating some at the edges of the petcock, probably allowing the petrol a path between the coating and tank resin. I think that this, coupled with what appeared to be a failure of the layer to adhere to the tank resin, caused a renewal of the leak.

Of course by this time I tried to coat the tank it was in trouble, being in service for 50yrs with lots of leaded and unleaded fuels, including ethanol and mtbe additives. It is interesting that this tank first started to leak at about the time mtbe was replaced with ethanol.

I would try to treat a fiberglass tank again wit caswell but would give the greatest attention to prep of an older tank.

I presumed the question was about the internals of the tank, not the exterior. In either case, there needs to be a bond established between the coating and the polyester. Acetone will dissolve many organics, but methyl ethyl ketone might be better. When I did it, I used the tank for methanol - petrol is hydrocarbon and not an alcohol. It is probably less likely to cause a fail in service.