fiberglass tank questions

[slategrey66]

so what are the dis-advantages of having a fiberglass tank? if you knock your bike over or drop it on accident can the tank break open and spill gas out? or is there a internal metal core? just very hesitant on purchasing one without knowing how delecate they are compaired to obvious strong stock metal ones.

 

[Ringo]

Yes. That's the gamble you take for shaving some pounds. Alloy tanks aren't much better than glass tanks- they can crack upon impact. If it's a big concern for you, you should stick with a steel tank.

 

[killian101]

A lot of newer high end tanks (like these for newer Bonnies: http://www.farleyandace.com/Tank.html) will have a bladder built in to reduce the risk of fire and what not. Though, nothing is a 100%. If you plan on getting a fiberglass tank, spend the money on a good one.

 

[beachcomber]

I've used Fibreglass tanks since the 60's - and still do.

Just "dropping" the bike [ off the stand say ] onto the tank will cause NO structural damage. We've had our Cobra [ replica ] race cars hit Armco at 100 mph plus and come away better than a steel / alloy bodied car.

The only real chance of damage is if you slide down the road with the tank in contact with the tarmac - and even then you are unlikely to puncture / rub away the GRP.

In the UK Fibreglass was banned as a fuel tank material for a few years, until a study was done [ as opposed to a knee jerk reaction ] to prove that GRP was indeed stronger in most situations than steel - and certainly alloy.

An alloy tank will certainly be lighter than GRP in this application as the tank would certainly be thicker than say a GRP seat.

Of more concern would be to ensure that your tank is made from a material that wll withstand the attack of Ethanol fuel - most modern manufacturers have that one sussed.

Gordon Murray [ McLaren designer ] designed and bullt a speciality [ Kit ] car based on Mini components - the monocoque was entirely fibreglass !

An alloy tank would certainly be susceptible to a puncture type contact, whereas a GRP tank would not [ ex. CRASH HELMETS ! ]

Attached pic is of one of my Porsche 356 Speedster replicas after the customer was hit by a GM Astra van at 40 mph - the Astra had to be towed away !

 

[teazer]

There is no perfect, light, crash proof tank. Like BC I have used GRP tanks since the sixties on the street as well as race track and have hit the road a couple of times at speed. GRP will typically de-laminate in crash, the same as a helmet and that's impossible to fix if it's bad. It will absorb a large impact and doesn't typically split as such.

Steel tanks are cheap and absorb impact damage by deforming, but it the tank scrapes on the road, you have sparks and fuel leaking and you know that's not good. For cars, plastic molded tanks are safest - they melt slowly and release fuel in case of a car fire where steel tanks may explode as pressure builds up from heat.

Alloy tanks are great. They look sexy and sophisticated and like a slim sexy sophisticated lady, they don't always age well. They must be isolated from the frame or they will age harden and crack. Look after them and they should last a lifetime.

With a GRP tank, ask the supplier what they did to protect it from ethanol leaching. The best answer is epoxy coating or epoxy resin which makes the glass hard to work. Worst are normal polyester or vinylester resins. We used to make tanks out of isophthalic resin for use on methanol burners, but they still go soft. If they don't seal the tank, get a caswell kit and that will seal it perfectly.

 

[rockcitycafe]

no sealer at the moment is working with ethanol, sealpack makes a buna-n rubber sealer, but because of the cost and complexity of applying it, no one I know of is using it. when you buy a fiberglass tank, put $100 a month into a bank account and by the time the glass fails, you might have enough saved for an alloy tank

 

[beachcomber]

A one off fit [ ie tunnel ] alloy tank - based on an existing former shape - ie Manx, Goldie, 7R. will set you back anout £400- £500 here in the UK.

Up until his retirement - only last year - there was a supreme ali basher locally to me who would make you a tank for £250 ! The only problem was time scale. You didn't even dare ask for a delivery date - just give him the order and waited !

His work was absolutely the canine's cajones - most of his work was for the major Japanese factory museums. It was nothing to visit his workshops and see works TZ Yamahas rubbing shoulders with 4 and 6 cylinder CR Hondas.

His best work for me was a one off tank for my Guzzi LeMans Cafe Racer I built 20 odd years ago.

Bizarrely GRP tanks are now around the £300 + mark.

There are a couple of proprietory sealant kits here in the UK which have been tested under real World conditions for many years now and to date have perfect results.

That said, when it came to making a suitable one off tank for our new Yamaha TR1 Cafe Racer "Vindicator" - we took the easy [?] option and kept the original steel tank and made a GRP cover in the style of an AJS7R 6 gallon "TT" tank.

Weight saving is usually not the prime reason for fitting a GRP tank on a road machine - just as well, my Triumph GRP 5 gallon tank weighs THREE times that of my 5 Gallon Manx tank !

 

[slategrey66]

no sealer at the moment is working with ethanol, sealpack makes a buna-n rubber sealer, but because of the cost and complexity of applying it, no one I know of is using it. when you buy a fiberglass tank, put $100 a month into a bank account and by the time the glass fails, you might have enough saved for an alloy tank

yeah i'm very mixed still. i'm thinking about just using a stock cb750 tank and finding someone to hack it up to the style im looking for. well not hack, style, modify..

 

[slategrey66]

what the hell is that metal thing coming out on the left side of the tank?

 

[CB350f Cafe]

I believe it's a breather?

 

[slategrey66]

i think it looks stupid, im sure they could have done it differently.

 

[Gage Werke Composites]

I make aluminum, steel, or stainless steel fuel cells that are covered with a top "shell" of carbon fiber or fiberglass. Works great. Not as much fuel capacity but with my long tanks there's still plenty. And if you drop the bike and damage the top shell you can just replace the top and not the whole tank. Check out the ones I built for my 450 and 100 below. What bike you looking to put a tank on? I might have a design already that would work.

 

[slategrey66]

what do you charge for your tanks? i'd love a carbon fiber one similar to benjis tank.

 

[Gage Werke Composites]

What bike is it for?

 

[slategrey66]

What bike is it for?

1980 cb750

 

[JA-Moo]

no sealer at the moment is working with ethanol, sealpack makes a buna-n rubber sealer, but because of the cost and complexity of applying it, no one I know of is using it. when you buy a fiberglass tank, put $100 a month into a bank account and by the time the glass fails, you might have enough saved for an alloy tank

The Caswell tank sealer has no problem with the ethanol. Cheap (ish) and easy to use.

 

[flatcurve]

1980 cb750

I'd be interested in a tank that could fit a DOHC as well...


Also, as far as tank coatings go, the new breed of phenol novolac or bisphenol-a novolac epoxy resins are supposed to be pretty good at resisting attack from unleaded gas with 10% ethanol and MTBE (which in cold states is present in higher quantities starting in mid fall). I know it's used on large steel and concrete fuel storage tanks (you know, those big things out by the airport) but I don't know how it stands up in fiberglass tanks. I would take special care to not only coat the entire inside, but also make sure that it coats any exposed edges as well, such as around the petcock and filler cap holes. All the sealer in the world won't do any good if your tank starts to delaminate in these areas.


Caswell is a phenol novolac epoxy resin, and just about the only one you can buy as a retail consumer in small quantities.

 

[rockcitycafe]

The Caswell tank sealer has no problem with the ethanol. Cheap (ish) and easy to use.

wait.

 

[Big R]

What about fitting a plastic tank to a frame and making a "shell" out of fiberglass? Plastic tanks seem to have many benefits.......

 

[flatcurve]

What about fitting a plastic tank to a frame and making a "shell" out of fiberglass? Plastic tanks seem to have many benefits.......

The plastic motorcycle tanks I've seen have either been too small, don't fit the bike, or they look ridiculous. And forget about making a plastic tank, because you can't just use any plastic. Modern day gas tanks and portable gas cans are made out of blow-molded high density polyethylene. But the inside surfaces are also treated with fluorene gas to resist attack from gasoline. Without it, they would melt in about six months time. And modifying an existing tank or can would ruin that fluorocarbon layer. It would only be a matter of time before the plastic started to swell and leak. And then you'd basically have the same problems as you would with glass.

Honestly, I think if you're budget minded, fiberglass is the way to go. The Caswell epoxy system uses the right chemicals. Like I said, it's in the same group of resins that they use to coat large storage tanks with. And those guys stand to not only lose a lot of gas if it fails, but also have the EPA fine the hell out of them if there's a spill.

Otherwise, find a source of gas with no ethanol in it.

http://pure-gas.org/extensions/map.html