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Fibreglass Petrol Tank

09/12/2010 3:15 PM

I have a fibreglass (GRP) petrol tank on a '73 Norton Motorcycle. Apparently the ethanol additives in modern petrol / gasoline damages the polyester resin from which the tank is made. As it happens my tank also has a slight leak around a pet-cock, so the plan is to thoroughly clean the tank and then reseal it, most likely with epoxy.

With a vented tank of this age and the porosity of raw fibreglass, there are residues of petrol (staining and emulsified). Naturally these have to be dissolved / cleaned away before any sealant will securely adhere. Ideally surface etching of the resin would probably help adhesion. But what will do this without also eating through the polyester resin ?

I made enquires re. steam cleaning and also vapor blasting but access is particularly poor on a motorcycle tank, and the outside is painted. Simply put, even with extended pipes the nozzles are too big and the bridge shape of the tank too convoluted to get a clear shot.

Re Sealing : I'm tending towards using epoxy, or perhaps vinylester resin to reseal the tank because I read of so many failures with proprietary tank sealants (often after a few years). Indeed I looked the same type of tank today, and that had been sealed with some sort of flexible membrane - that was lifting !

There's a lot of us in this predicament, as GRP tanks were commonly used in the motor, motor-cycle and leisure marine industries. New tanks are either unavailable or extremely costly, and then again not-original. We would really appreciate help with this. Thanks, Pete

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#1

Re: Fibreglass Petrol Tank

09/12/2010 4:26 PM

http://www.caswellplating.com/aids/epoxygas.htm, check this stuff out.

As far as cleaning the inside of the tank, I would give it a quick wash with acetone, it will emulsify the remaining gasoline oils. Followed by a couple of washes with denatured alcohol. Since you can't really see the inside of the tank very well, I guess a smell test would be the best way to determine if all gasoline residue is out.

Oops, just occured to me, unless you are repainting the tank, don't get acetone on the paint it will lift it. If you are not repainting the tank, use denatured alcohol alone. It will probably take several treatments, but it won't damage the paint.

I didn't read the entire site above, they may have a better way to pre-clean the inside of the tank.

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#2
In reply to #1

Re: Fibreglass Petrol Tank

09/12/2010 6:04 PM

Hi Kramarat and thanks for your speedy link and advice. From what I gather - from classic bike forums, Caswell seem to have the best reputation for tank sealers..., although I'm amused by their dig at Kreem and POR-15.

Re. cleaning : I removed the pet-cocks, which are externally stained from petrol (seepage), and have immersed one in a jar of acetone for a week. Alas, aside from tinting the clarity of the acetone to that of weak tea (without milk or sugar !) the stains on the pet-cock are not visibly touched. I fear that if I were to leave the fibreglass tank full of acetone for this long - I'd not have a structural tank left to reseal !

I haven't tried denatured alcohol (methylated spirits). I think I have some in the garage so I'll try it overnight on the other pet-cock.

On a older but similar CR4 thread (which led my to asking this more specific question) - a very smart and most picturesque lady, suggested electrolysis. However, I assume that would only work (into all the corners) with a metal tank.?

I wonder if ultrasonic cleaning might be a way ? (though I know nothing about how to do this in practice).

Again Thanks, Pete

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#4
In reply to #2

Re: Fibreglass Petrol Tank

09/13/2010 5:59 AM

I think the stuff kramarat found is the way to go. I'm not crazy about the drywall screws, but I'd follow the directions anyway.

If your petcocks have any rubber seals in them, a week in acetone may have killed them.

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#6
In reply to #2

Re: Fibreglass Petrol Tank

09/13/2010 7:03 AM

Even if you've removed all traces of old petrol, the plastic itself, may be discolored. I don't know if you'll be able to remove all of the stains.

You didn't say if the pet cock valves are metal or plastic. If they are metal, and you just want to improve the appearance, a soak in some jewelry cleaning compound might help.

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#3

Re: Fibreglass Petrol Tank

09/12/2010 11:34 PM

Mix a few liters of hot water with a few spoons of caustic soda. By hot I don't mean boiling - I mean hot enough to melt grease in a fry pan.

Add the caustic soda slowly otherwise it will tend to fume and perhaps spatter in the water, then slosh it around inside your tank for a couple of days...

That will remove any crap and it will "etch" out the oily / plasticised grunge from the tanks inside.

Then flush with clean water.

Also wear fully enclosing safety glasses and work in a cross wind....

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#5

Re: Fibreglass Petrol Tank

09/13/2010 6:58 AM

When I was restoring antique cars we use a tank sealer called (Lion Sloshing Compound) I think it was also used on aircraft applications. It sealed and protected the inside of the tank. It may have been called lion oil any way it coats and seals. Not sure if it handles alcohol or not. Might be worth a try. Polyester resin if properly cured is inert to just about anything but again do some research. Hope it helps.

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#7

Re: Fibreglass Petrol Tank

09/13/2010 7:58 AM

Actually friend, it is to your best interest to have a new tank made out of metal.

A metal tank will out last any fiber formed tank in exposure and usage of such tanks.

Yes it will cost you a small amount of money, but well worth the safety in hand over the fiber formed tank.

From a fellow motor cycle enthusiest,

Maximo

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#8
In reply to #7

Re: Fibreglass Petrol Tank

09/13/2010 8:10 AM

A metal tank shouldn't crack open if you crash like a glass tank will. I say "shouldn't" because butt welded alloy tanks look great but questionable welds can let go over years of vibration.

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#9
In reply to #7

Re: Fibreglass Petrol Tank

09/13/2010 8:32 AM

You are right. But, I would still treat the original tank and keep it.

If he ever wants to sell it, it will be important to be able to have it as close to original as possible.

Plus, if he ever gets in an accident bad enough to smash the fiber glass tank, he'll probably be dead anyway.

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#10

Re: Fibreglass Petrol Tank

09/13/2010 9:43 AM

Hi and thanks to all contributors.

The reason to reseal it, is because of the additives in modern fuel, and the inevitability of those causing damage.

The tank is now 37 years old and aside from the aforementioned minor seepage - is in good shape, with no signs of impact explosion ! Query : would the sparks off a sliding steel tank not be hazardous ? Interestingly my helmet is also made of fibreglass

Originality is regarded as desirable in classic vehicles (and in their valuations). And without wishing to sound glib.. If I had wanted a newer motorcycle (without the characteristics of a 'classic') then I wouldn't have bought this one!

There are other reasons for keeping the original fibreglass item ; a) economics, b) because I prefer not to subscribe to throw-it-away-and-buy-another philosophies, c) no rust, d) less weight, and particularly important to an old timer like me, e) the fibreglass is nowhere near as cold on the legs.

At $229.95 for a pint of Lion Sloshing Compound, my economic argument is on wobbly ground. However, that product is for aviation gas and jet fuels, which subject to legislation preventing ethanol. As it is a fibreglass tank would be fine for those fuels.

Cleaning with caustic soda is a thought, which I think is worth exploring.

Again Thanks, Pete

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#11

Re: Fibreglass Petrol Tank

09/13/2010 10:04 AM

This is the motorcycle tank in question, around about 27 litres (6 gal imp.)

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#13
In reply to #11

Re: Fibreglass Petrol Tank

09/13/2010 10:58 AM

Nice paint job. I understand why you want to keep it.

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#19
In reply to #11

Re: Fibreglass Petrol Tank

09/14/2010 7:17 AM

You definitely don't want to spill acetone on that!

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#12

Re: Fibreglass Petrol Tank

09/13/2010 10:44 AM

I'm not a chemical engineer or anything, but looking at that tank, if you want something to put some miles on and are concerned about the fuel, I think I would take that tank, clean it out with soapy water, wrap it in bubble wrap put it on a shelf and buy a used tank to ride with, the tank takes a beating, the paint looks real good and can only get worse.

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#14
In reply to #12

Re: Fibreglass Petrol Tank

09/13/2010 12:12 PM

Hi Norton 850,

Perhaps you can find me an affordable interstate tank over there in the US and ship it across to me here in Blighty, all in for a couple hundred dollars ?. Good tanks over here are rarely sold. A new tank will cost a $1000 with nice paint and sign writing.

I'd love to have one made in aluminium but again my budget is in a sorry state.

Aside from which aren't these bike made to be ridden !?

Thanks, Pete

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#15
In reply to #14

Re: Fibreglass Petrol Tank

09/13/2010 2:13 PM

I'll look around

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#16

Re: Fibreglass Petrol Tank

09/13/2010 2:37 PM

Theres a couple on ebay

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#20
In reply to #16

Re: Fibreglass Petrol Tank

09/14/2010 3:08 PM

I'm watching out for one on e-bay, but particularly want the larger capacity 'Interstate' model, but I do appreciate your keeping an ear to the ground for me. Thanks, Pete

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#17

Re: Fibreglass Petrol Tank

09/13/2010 3:00 PM

The product you want according to the aircraft industry is 'This new Randolph 912 Sloshing Sealer is recommended as a superior product to 802 Sloshing Sealer in fuel tanks using fuels containing alcohol.' I researched this from the Aviation industry both Home Built and factory Built.

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#18

Re: Fibreglass Petrol Tank

09/13/2010 9:03 PM

I was wondering about coating the inside of the tank with gel coat compatible with ethanol?

I've used Kreem on more than one metal tank, with results ranging from excellent to terrible. the tank must be properly cleaned & neutralized

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#21
In reply to #18

Re: Fibreglass Petrol Tank

06/15/2011 8:57 AM

Hi gents,

I'm back again, after a complete nut and bolt rebuild of the rest of the bike, but still faced with the same questions (1. what chemical to clean out an old GRP ployester petrol tank ? and, 2. what to seal with to prevent ethanol from disolving it ?)

I've tried cleaning a test piece of GRP by soaking in acetone and it structurally dissolved the ployester. The impact on clearing the petrol deposts were not successful either. Instinctively I feel surface etching is needed..

I've recently read one man's experience of the same problem on his boat : http://egyptian.net/~raymacke/Cbnskif17.htm which continues on pages 18, 27 and 36 (change the number in the address). Clearly a practical type, this gent made an epoxy tank, then used Caswell sealer. Each failed. Cawell is a brand leader and belittles other manufacturer's sealant, so I can only conclude that they are really no better than one another. I've search marine, classic vehicle and aviation websites, by still there's no-one which hasn't reports of ailure.

I had hoped to have a new aluminium tank made - close to the original design, but through staffing problems (craftsman) that supplier let me down, after my waiting 5 months.

I've searched for a decent steel tank, and even bought one for £450 from photos - but the supposedly show-paint job was poor (& I'm being very polite here !) so for that price I sent it back. All other steel tanks I've seen also need repainting which will cost another £400 on top of the same purchase cost is crazy.

And so now, I'm in the last throws of the bike's rebuild (which has really stretch my limited resources and patience) but still have no tank.

So come on you Engineers, Chemists, and/or Material experts, let's try and get to the bottom of this.. Or are you saying in that you give in there is no solution ??

Thanks,

Pete

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#22

Re: Fibreglass Petrol Tank

06/15/2011 4:13 PM

You made me wonder so I went off on a little search

& found this

http://www.por15.com/US-STANDARD-TANK-SEALER/productinfo/TSG/

I wasn't sure so a sent an email asking if it would work on a fiberglass tank

& here's the reply:

Hello Garth,

Absolutely. As long as you use the Marine Clean and the Prep & Ready to clean and prep your tank, you should have excellent results.

Mark Kanya

POR-15 Inc

PO Box 1235Morristown NJ 07962

CR4 Admin - phone number removed

From the Site FAQ: Do not post phone numbers or email addresses. The CR4 Admin will delete all phone numbers posted in threads or comments, and we strongly urge you not to put up email addresses. You can share this information via the CR4 internal messaging system.

Here's the Marine Clean

http://www.por15.com/MARINE-CLEAN/productinfo/MCG/

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#23
In reply to #22

Re: Fibreglass Petrol Tank

06/16/2011 3:29 AM

Thank Garthh,

Your help is most appreciated.

I have used POR chassis paint before, and was pleased with it until I found out from a fuel leak that it wasn't resistant to petrol. This was after I had painted the whole chassis including the engine bay and the tank, the filler pipe and anywhere else on an classic (read 'old') car where fuel may possibly leak. I was not glad !

I have also used their tank sealant once before, on a steel BSA motorcycle tank with light rusting, but sold the bike after a short while so never knew of the long term result.

Alas, a quick search of POR15 on the interweb soon reveals a number of dissappointed owner problems and failures. One claim they make is that it 'stops rust in it's tracks', but on 'hi-speed' website someone discovered otherwise and ended up scrapping their tank. Not exactly my issue but it shows that I have to be wary of manufacturer's claims.

On that point, despite what the sales rep might have said ; on UK supplier ; Frost's website it clearly says and underlines POR15 "Not suitable for plastic and fibreglass tanks". I've just written to ask what they recommend then ?

POR15's technical spec also says it's contains isocyanate which aside from health risk implications is a compound used in fibreglass tooling paint - because the GRP doesn't stick to it - so it's almost a release agent.

I guess that leaves me in a 'I don't have confidence in the product' situation.

Aagh !!

http://www.frost.co.uk/automotive-tanks-products/por15-fuel-tank-sealer.html

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30sqm (7); Anonymous Poster (2); Garthh (2); kramarat (4); lyn (2); norton850 (3); Pretendgineer (1); roy hammy (2)

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