Fiberglass diesel tank? Is it possible?

[Christian]

Hi all!

I have a question extensive search on the net has not been able to answer.
We have an old Volvo C304 / TGB1314 that we have modified to diesel in our quest to make a good expedition vehicle. We have planned to have two 100L (approx. 25 gal) diesel tanks, each located either side between the front axle and the first rear axle attached to the frame rails, just like on a "real" truck.

Well, suitable tanks we have found are for boats etc. and quite expensive, so I thought it might be possible to makek our own tanks in fiberglass.

My idea is as follows: Take some big blocks of styrofoam and shape it so it fits just like I want it to (of course leave space for the fiberglass to cover it) and wrap the styrofoam in cling film. Then start covering the whole thing in fiberglass. Afterwards I would cut out the main hole in the tank, pour in some acetone or similar to dissolve the styro. If the cling film is a problem I can coat the inside with a propriate product.

Glassfiber tanks are used in boating and on motorcycles, so why not on trucks?

I think fiberglass is equally strong as a steel or aluminium tank provided that I put enough layers on. It will not be heavier or more unsafe IMO, but I would really like yours?

 

[milo12]

It could be done but in my opinion it is too much work. I would weld up a steel or aluminum tank. If you choose a fiberglass tank vinyl ester resin is much more chemical resistant than epoxy. Note vinyl ester will attack styrofoam.

 

[ntsqd]

There are shops that can make a metal diesel fuel tanks to order. May not be any savings over those that you've found. You would need to get some quotes to know for sure.

Latex paint will keep the polyester resin from eating the stryofoam. If you start out with a large block of foam you will have a huge mess when you try to dissolve it. Gasoline will dissolve it too, but the resultant goo is nearly napalm. I'd suggest that you use foam sheets and build up a hollow form rather than making it solid.

I think that for ease of field repair-ability that I personally would prefer a metal tank.

 

[Christian]

Thanks alot for the answers!

As for welding one in steel or aluminium, I am okay at MIG, but not skilled enough in TIG yet. MIG welds are not suited for at tank, they almost always leak. So I would have to have somebody else TIG them. I know that building them from fiberglass might be labour intensive, but it would only hurt my TV-time, and I make that sacrifice willingly!

The tank I found that fitted costs around 800 $ here. I think that is a lot, and money I could easily spend elsewhere on the project. Having someone custom built them will end up in the same price range as a good welder/fabricator costs at least 60 $ and up to above 100 $ here.

I have the guidance of an old boat builder, who is very knowledgeable in glassfiber, so he will guide me in choosing what to use.

The point that you can easily make any shape is a good one. space is at a premium, so I cannot "just" use some old truck tanks and be done with it.

I have read several posts on boat builder forums about the issues with ethanol, but thanks for the heads up!

As for field repair, carrying a small glassfiber repair kit in a glassfiber camper would be a good thing anyways, so it could easily double as emergency tank repair kit. A Steel or aluminium tank cannot be welded on the side of the road, not if a proper seal is needed, and proper safety precautions cannot be taken either. And I suspect that in a lot of rural areas it would be near impossible to fix an aluminium tank fixed. So fiberglass might be just as good in these situations. Please correct me if I'm wrong, I'm just guessing here.

Thanks for all the good advice, and please keep them comming!
Maybe I should wish for the West book for Cristmas?

Best Regards,
Christian

 

[ntsqd]

I would not say that MIG is unsuited for building liquid tanks, just that care must be taken at the starts and stops. Most large diesel tanks in the U.S. are manufactured using the MIG process, or possibly the very similar Submerged Arc process.

There are products made to seal leaking fuel tanks. POR-15 makes one, as does Kreem. Both isolate the metal from the fuel to control rust. A friend has used the POR product on a MIG welded tank with excellent results. (Tow truck operator deformed a corner of the custom tank with his J-hook and started a leak.)
It might be worth looking into if they will adhere to fiberglass or not. If they will, then they should head off any problems with chemical attack of the resin. They do require that the tank be able to be rolled around to get full coverage.

I like the idea of fully coated plywood in the tank for structural reasons.

 

[Christian]

Why this approach isn't taken with h2o & waste tanks more often surprises me, with general wood working skills you can build strangely shaped tanks to fit weird voids when space is tight - not as easy as buying a poly tank...but when a standard rectangle just won't do...

Exactly! I have the same idea for tanks that fit inside the frame rails above the rear axles, but leaves room for the axle articulation.

Well i still have a lot to do before I get to the tanks, but research is always good!

 

[milo12]

Here is a link to add to your research.

http://www.boatdesign.net/forums/boat-building/epoxy-fuel-tanks-278.html

Lots of info from people that have done what you describe. The main lesson seems to be it is not as simple as it appears, lots of bad info too.

Good luck and have fun with your project.

 

[Ursa Minor]

Resins

Just a note, if you get your resins from a composites supplier, rather than hardware store or similar, they will have specific resins for fuel tanks - John

 

[Christian]

Thanks for the replys about resin and links etc. I will have the supplier here in DK guide me on what to use if we go forward with glassfiber tanks. As someone pointed out at the beginning of this thread it is a lot simpler on a truck like ours where you can see what is going on. We are not hiding the tank in the structure as in boats. One side-effect is that making the tanks from the outside makes it rather difficult to make baffles in them though.

 

[inked33]

mig welding gas tanks is fine and actually done quite often. i have built more gas tanks then i care to count all using mig when i was the welding foreman at a company that manufactured horizontal directional drilling machines. the most important thing is to overlap your welds start/stops. just to make sure theres no leaks pressure test it with soapy water. whatever you decide to build with good luck and post pics when your done

 

[Peter_n_Margaret]

I made diesel tanks for the OKA with roto-moulded polyethylene and spin-welded threaded fittings.
A friend hot air welded tanks using the same material.
Light & very tough.

Cheers,
Peter