Fixing a fiberglass tank

I was asked to make a fiberglass tank immune to ethanol and stop it leaking from the filler and from the two fuel outlets. The owner had used POR-15 to seal the tank, this stuff had buggered up the threads of the filler not letting it close completely and it had leeched into the two petcock bungs preventing the valves from seating correctly. The owner had obviously put the big arm on the valves dislodging the bungs from the fiberglass letting gas seep past. The owner had then "painted" resing on the bottom of the tank in the hope it would be OK, it was not!

Here is a before piture of the bottom



I cut the bottom out and right away I could see the POR-15 peeling of the inside top



This is on the bottom, is POR-15 really sealing with all these pinholes?



I chiseled some of the sealant off...



Here is a clump of sealant removed from the bottom:



Here is the new hardware I will use:



A few pictures of what I could remove, in some spots, the POR-15 had adhered well and in others, not...





I then covered all the insides with fiberglass cloth and used Vynil Ester resin which I was told resists ethanol. There were at least two coats and at some points 4 or 5. I painted Hirsh sealant all over the insides since at that point I could do it easily. Then I put the two halves together and glassed over the "seams" as well as everywhere over the bottom. I again sealed the whole tank with a second coat of hirsh sealant and dried it out overnight with a fan. I think it should be OK for weird fuels now.





Now it needs a new paint job.

Things I have learned with this repair. Vynil Ester resins stink (I think polyester does too, but a bit less), next time I will cut really close to the sides, it will be easier to mate the two halves after doing the insides.

Jean

I used POR-15 on a couple of my Bultaco tanks. POR-15 specifically says not for fiberglass. That didn't stop me. Needless to say it didn't work as I had hoped, but I obviously don't blame the POR-15.

They've finally made it legal to sell non-ethanol gas in this state :roll: so once I find some it should be better.

Nice job, Jean.

I also used POR 15 in a "new" glass tank with the same result. Only difference is the POR15 agent in Australia said it was OK for glass tanks as long as the tank was cleaned using their cleaners. RUBBISH !
Their tank sealer is crap, it's just a fancy paint. (some of their other products are very good though)
POR 15 sealer peels off with petrol (fuel) that doesn't have ethanol and is possibly worse with ethanol.
After I removed as mucch as possible I coated the tank with Hirsch and all is good after 3 years.

The POR 15 in my tank looked exactley the same as yours with bubbles everywhere. Crap!
Be warned, don't use POR15 tank sealer.
I heard a story regarding a certain US vee twin manufacturer using POR 15 in their new bike tanks and all had to be replaced under warranty.

Graeme.

Jean, very nice job.

My understanding is that a phenolic resin such as Novalac is needed to resist the ethanol. Caswell sells it in small quantities. Maybe there's such a thing as phenolic vinyl ester.

My understanding is that a phenolic resin such as Novalac is needed to resist the ethanol. Caswell sells it in small quantities. Maybe there's such a thing as phenolic vinyl ester.littlefield

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You're getting warm! Epoxies are a subset of phenolic resins. Now If you can just figure out how to make it affordable.

http://www.derakane.com/downloadSer...8C6F0CA949A85256FCE004B0275\$FILE\470-300.pdf

Notice this stuff is used to make coatings to line tanks to hold gasohol.

Jean's idea of opening the tank and brushing it on is a good one. You should be able to reassemble the tank using this stuff as a binder.

Good job Jean, and thanks for sharing this. I plan a similar repair when I get a donor tank to mess with but plan to use some different products. I will report back, but by now it will probably be next winter!
Russ

Jeandr said:

next time I will cut really close to the sides, it will be easier to mate the two halves after doing the insides.

Jean

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What did you use to cut the tank open?

swooshdave said:

Jeandr said:

next time I will cut really close to the sides, it will be easier to mate the two halves after doing the insides.

Jean

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What did you use to cut the tank open?

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Actually, a dozuki nokogiri (Japanese wood saw) and a Dremel with a cut off wheel, now I have my eyes on one of those oscillating saws if I do another tank.

Jean

Jeandr said:

swooshdave said:

Jeandr said:

next time I will cut really close to the sides, it will be easier to mate the two halves after doing the insides.

Jean

Click to expand...

What did you use to cut the tank open?

Click to expand...

Actually, a dozuki nokogiri (Japanese wood saw) and a Dremel with a cut off wheel, now I have my eyes on one of those oscillating saws if I do another tank.

Jean

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Like this?

Exactly, but since I will probably not use it as much as a pro would, I would buy a cheaper one (saw [pun intended] one for $69)

Jean

Jeandr said:

Exactly, but since I will probably not use it as much as a pro would, I would buy a cheaper one (saw [pun intended] one for $69)

Jean

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Harbor Freight is normally for $69 but they are on sale right now for $39...

I really like that gascap! Is it chrome or ss? I wanna use something like that if I ever build an old bobber type bike

pelican said:

I really like that gascap! Is it chrome or ss? I wanna use something like that if I ever build an old bobber type bike

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I got it on e-bay it is non locking and vented. The good thing is can be screwed in anything. On this tank, I embedded a steel ring in the top of the tank so there is no way the screws will pull out. I think the only thing wrong for a street bike is that smeone could walk away with the cap so for street use, a locking cap may be better.

Jean

Did you make the flanged nuts for the taps?

swooshdave said:

Did you make the flanged nuts for the taps?

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Of course. I used a ¼" NPT coupler, cut it in two and soldered them to two pieces of copper (I used a copper pipe, cut it open, flattened it) then made everything round on the lathe. Before I put them in place, I drilled a series of holes along the outside edge of the copper plate to give the resin and glass a better grip. The whole thing is very solid.

Jean

Jean, is this tank now being used? if so, how is the vinyl ester resin holding up?
thanks, Don

DonOR said:

Jean, is this tank now being used? if so, how is the vinyl ester resin holding up?
thanks, Don

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I just got an e-mail from the user and he said he was very happy with it.

Jean

Jean,
Would you be interested in repairing a tank I have?
Thanks

I just cut the bottom off my Fastback tank and found 2 layers of sealer from over the years totally delamenated from the original tank surface. All of it easily peeled off from both halfs and exposed the original inside of tank surface ready for etching and sealing...I've been looking around for the proper product and came across "Bill Hirsch" products... http://www.hirschauto.com/prodinfo.asp?number=CRK-01
Has anyone used this? It sounds like the way to go.

I used Hirsh sealer on two tanks, but by opening them up, I was able to paint on one coat before putting the two halves together, then I sloshed another coat after the tank was put back together.

Jean