Fiberglass Fuel Tank Question

S

snowman0650

New Member
I am wanting to take a CB200 Fuel tank and form it into the shape I want for my cb350. I want to add to the size on the sides, top and length. I stripped the paint off the tank so I have bare metal, and what I planned on was to scuff with 80-120 grit, add a layer of vinylester fiberglass to the metal, then coat it with urethane foam to build it up to the size I want, sand it smooth and put several layers of glass over the whole thing. Basically, a nicely shaped Cafe tank with a metal bladder.

Is there a better way? I am wondering about the bare metal should I prime it, just put the urethane foam on it without the glass layer, or something different?

Thanks for the input,

Jim
 
That's a real quick way to create a rust trap...

There is no mechanical bond between the resin and the steel when you lay fiberglass over steel. There will eventually be a point where the fiberglass and the steel part ways and then there's a gap where moisture will condense. You know the rest...

Reshaping a steel tank needs to be done with steel.

-Deek
 
Best bet is to just carve a tank from foam and lay your glass on it. Then remove said foam and finish. There's a bunch of how to's on the site.
 
I've seen people weld additional panels to tanks just for the looks (see here: http://www.dotheton.com/forum/index.php?topic=36255.msg461291#msg461291). It would still fit the same and have the same volume, but the outside would appear different. Is this what you're trying to do? Also, have you just considered getting a different tank? CB350 frames are not that big so a lot of other tanks could probably be made to fit with a little massaging.

Edit: Or do what Mr. Yinzer suggests above. If you're going to glass a tank though, use professional materials and be prepared to line it.
 
I would definitely prime and paint the metal first, don't want any moisture trapped in the foam to rust out the tank.
 
As stated, no real bond between the metal and resin, can be popped apart by apply a slight amount of pressure.
 
Hummm, I guess I did not consider the rust aspect, I thought the bond between the metal and fiberglass would be stronger and more permanent. I will rethink my approach, I have a foam mold that I can wrap, but I thought that would be a bigger process then having the inlet, mounts, and petcock all set. And the whole ethanol eating the fiberglass issue....

Thanks,

Jim
 
snowman0650 said:
...I thought the bond between the metal and fiberglass would be stronger and more permanent...
Click to expand...

Nope. Witness the hundreds of Triumphs and MG's with fiberglass fenders that consequently ate the real fender underneath. Plus every douchebag V8 with a fiberglass hood scoop on a steel hood (and no blower)... don't slam those hoods!

-Deek

[EDIT] I just noticed SEM sells an epoxy fiberglass to metal adhesive. I have no experience with it at all but if you wanted to be a guinea pig, go for it! Every SEM product I've ever used is top notch... if they say it will work, it probably will. In this case you wouldn't bond the fiberglass directly to the tank, but glue it on afterward.[/EDIT]
 
Part of the problem is that the two materials expand and contract differently, so the mechanical bond that it has eventually breaks from all the expansion/contraction. It will eventually fail. Your best best (and the way I'm approaching it) is to create the fiberglass shell as a separate unit that can be attached to the tank instead of being bonded to it. I'm only half way done so still a work in progress, hoping it will work. Kind of like the false tank on modern sportbikes.
 
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