Fibreglass Petrol Tank

There is a good article about it on here. Hitchcocks Motorcycles -

 

Ethanol is a real pain. I have a mate who builds cafe racers - he had a GRP tank for a little Honda that he was building. Ethanol had made such a mess of it that he ended up cutting the base out and making an alloy tank to go inside it, so it looked like the original but had a solid tank hidden within. Hopefull tank sealants have now caught up with this sort of problem and will stop it happening...

 

Glassfibre tanks were banned for motorcycles in the early 70's/ When did they become legal again?

 

an alternative to Red's link is Novolac epoxy vinylester resin - DION® 9400 - Reichhold if you can get hold of it.

Failing that, just make sure that your barrier coating solution is vinylester based as ethanol will attack epoxy and polyester. Its always worth painting two coats on the second a different direction to the first just to make sure you have coverage and don't miss anything.

 

I used Caswell on my Pantah tank after the incompetent tank maker that Radical Spain used failed to fix the leak. It is clear when mixed, and did the job perfectly. It was actually pretty easy to mix, but make sure you follow the instructions, especially temperature. I got mine from Hitchcocks, they use it to seal the Enfield tanks they have made.

 

I used a half quantity mix as they suggested would be correct for my volume. However, because of the shape of my tank the surface area was larger, so I mixed up the rest of the tins for a full coat. The only hassle is sitting and revolving the tank for half an hour. I just put Top Gear on and watched that! It's been perfect ever since. The worst part is now Hitchcocks send me a catalogue of Enfield stuff every know and then, and I'm tempted to build a little Royal Enfield cafe racer

 

The Road Vehicles (Construction and Use) Regulations 1986

but

Directive 70/221/EEC - Automotive - Enterprise and Industry

Which says... "Tanks and reserve tanks for liquid fuel I. 1. Fuel tanks must be made so as to be corrosion resistant. They must satisfy the leakage tests carried out by the manufacturer at a pressure equal to double the working pressure but in any event not less than 1.3 bars. Any excess pressure or any pressure exceeding the working pressure must be automatically compensated by suitable devices (vents, safety valves, etc.). The vents must be designed in such a way as to prevent any fire risks. The fuel must not escape through the fuel tank cap or through the devices provided to compensate excess pressure, even if the tank is completely overturned : a drip shall be tolerated."

But doesn't specify a material... so as long as you can prove the tank is made to the European standards, it should be OK. Although you may come across people who will argue that point.

I would also say that the majority of metal tanks, especially steel ones, are definitely not resistant to corrosion now that the ethanol content is so high, so how do they get through the legislation? Also "corrosion resistant" is a very wooly term - corrosion from what? Petrol? Rain? Typical EU legislation - deliberatley written to be vague so that lawyers can earn loads of money arguing over it...

 

In isolation that would be the case but in reality the EEC directive you've quoted only applies for the year span that the directive is active.

So, no most steel tanks of old would be illegal if manufactured today but would be exempt from this directive if on a vehicle of the appropriate era. Also within the wider directives as a major manufacturer you have to submit components to specific tests or certifications which you bypass on small series production (which is why some manufacturers produce limited editions of say 100 as the classifications become completely different).

Although it doesn't stipulate material it does state that fuel shouldn't escape which also means when the vehicle is in an accident (current directives) which again means that manufacturers stay away from things like composite tanks just in case - also on cost grounds as a light weight composite is expensive in this context (fuel cells and the like).

What you're not seeing with this directive is that a mainstream manufacturer has to subject their vehicle to an environmental chamber (salts / vibration rigs / temperature oscillations/ chemical and gas attacks etc to simulate everything that can get thrown at it ) to validate warranty and service life, and in this respect if that tank rots out or fails in say 10 years of sumulated use (most cars tested are lifed at 80K / 8 years as a mean average) then it can't be certified as meeting directive. Or you stamp it not for road use and use that defence. Still doesn't mean that its good to race professionally with though as the racing regs all have a standard to meet.

Bimota and several others get round this with the ABS tank under a dummy skin which is actually a really good way of doing it. But for the self build project builder shouldn't need to concern himself with this.

To put it in perspective - do what you like as you're only building one of them

However for ducati for example to recreate the grp fuel tank of old, it would have to be made from GRP and either lined with a puncture proof fuel cell or have a dummy tank cover over a jerry can tank or similar. All those tests have guidelines and cost a fortune to get that little stamp that says TUV or EEC etc. but without them you can't release the part for fear of any legal comeback.

This is why for example you wouldn't be able to release a cafe sracer style bike with flat slides on, as it would never get through emission regs under current guidelines.

In a nutshell the above said GRP tank, - seal it, keep on top of it with a yearly or bi annual inspection and enjoy.
If it's not thick enough, when you go down it might crack and piss fuel everywhere. But that's another bag of worms and in truth none of us ride with the "what if I come off today" attitude.

 

Fair enough Sev... I knew someone out there would have a better understanding of the "big picture" than me.
Thinking about it, the Laverda has a plastic fuel tank - under the rear bodywork and seat - so there must be some way of getting it past the legislation...