Fiberglass fuel tank?

[Eric Hahl]

I'm building the Tamiya Porsche 934 model and doing some research and came across some pictures of the fuel tank. Looks fiberglass to me. Wouldn't fuel eat that away? Did they coat the inside with something else?

[VINMAN]

A few year back, a lot of boats were using FG fuel tanks. Once they introduced the ethanol crap they started having issues with the tanks disintegrating.

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[Eric Hahl]

I would have thought the resin would get eaten away. Learn something every day.

[sc_rufctr]

Yes it was FG but it has a bladder inside.

(FWIW A Ferrari F40 fuel tank bladder has a service life of 10 years)

[herr_oberst]

Lots of dirtbike tanks in the '70s were fiberglass. Once Preston Petty made his famous front fender available though, that horse was out of the barn.

[VINMAN]

They never had any issues until the ethanol.

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[Jeff Higgins]

I have a carbon fiber tank on my 1993 Ducati 900 SS. Same laminating resin as would be used to make a fiberglass tank, a two part epoxy of some kind. Many old British bikes used fiberglass tanks as well. And, as Vinman says, lots of boats are built with them. I believe some light aircraft may use them as well.

The two part epoxy laminating resins hold up just fine. Unfortunately, most of these tanks are built in two pieces that must be joined somehow. My tank is a kind of "tortoise shell", as are most motorcycle tanks, with the visible top part all one piece and a more or less flat bottom, with a flange around it, inserted underneath. The seam is then glued with whatever the manufacturer chooses.

It turns out that these glued seams are the failure point. In my case, and in the case of many boats, ethanol based fuels dissolved whatever glue was used. I had to separate mine and re-glue it with something ethanol proof (I used JB Weld). Imagine this problem in a fiberglass boat, where many tanks are laminated into the hull after being glued together. For the most part impossible to repair.

So, yeah, the laminating resins hold up just fine, even to ethanol. The real lynchpin is whatever was used to glue the two halve together.

[Eric Hahl]

Originally Posted by sc_rufctr

Yes it was FG but it has a bladder inside.

(FWIW A Ferrari F40 fuel tank bladder has a service life of 10 years)

Thank you! Exactly what I wanted to know. Now I know how to paint it to make it look real.

[Jeff Higgins]

When I first started doing track days in my 911, we had a guy who actually took his Ferrari F40 out on the track. We all watched that car burn literally to the ground when one of those fiberglass tanks failed. The driver and instructor were lucky to get out alive. He never hit anything, had no incident of any kind that would have ruptured it. It simply failed and dumped all over the exhaust. Drivers following it, and the corner marshals, saw it was on fire long before the occupants knew. By the time they figured it out and got the car stopped it was over. Totally engulfed. Amazing they got out.

[sc_rufctr]

Originally Posted by Jeff Higgins

When I first started doing track days in my 911, we had a guy who actually took his Ferrari F40 out on the track. We all watched that car burn literally to the ground when one of those fiberglass tanks failed. The driver and instructor were lucky to get out alive. He never hit anything, had no incident of any kind that would have ruptured it. It simply failed and dumped all over the exhaust. Drivers following it, and the corner marshals, saw it was on fire long before the occupants knew. By the time they figured it out and got the car stopped it was over. Totally engulfed. Amazing they got out.

I wonder... How old were the fuel tank bladders in that F40?

This is the scene of a crash in Australia. Note: You can see the fuel tank but there's no obvious fuel leak.

[doug_porsche]

So the 934/935's had fiberglass fuel tanks, aluminum roll cages, powerbands that gained hundreds of HP in a couple hundred RPM.

what a time

[Bill Douglas]

Skip Newsom's Commando has a fibreglass tank that would be nearly 50 years old. So must be OK. Surprising though.

[schwarz633]

The Norton Commando I bought new in 1972 or so (not 100% of the year, it had the Combat engine) had a fiberglass tank. I got hit by a truck from the side and my foot broke the petcock out of the tank. The same year replacement Commando I got new had a steel tank.

[juanbenae]

Originally Posted by herr_oberst

Lots of dirtbike tanks in the '70s were fiberglass. Once Preston Petty made his famous front fender available though, that horse was out of the barn.

my pops' buddy we rode with bought a brand new Ossa back in in like 72-73. it had a bunch of fiberglass body work including the fuel tank, front and rear fender with some integrated numberplates.

Ol uncle Lee was not such a good rider and within 3-4 rides the thing was trashed. broken, shattered body work hanging and falling off while blowing in the wind...

[Jeff Alton]

Been used in fuel tanks for decades..... Marine, motorycyle and yes, some automotive....

Cheers

[sc_rufctr]

Originally Posted by Eric Hahl

Thank you! Exactly what I wanted to know. Now I know how to paint it to make it look real.

They way I'd do it: Use translucent yellowish paint to get the fiberglass look and then black paint on the other side so it shows through.

Not like this.

[cstreit]

Originally Posted by Eric Hahl

I'm building the Tamiya Porsche 934 model and doing some research and came across some pictures of the fuel tank. Looks fiberglass to me. Wouldn't fuel eat that away? Did they coat the inside with something else?

Wait - so thats the model?!

[herr_oberst]

The orange one above is the model.

I just figured out how they get that enormous bladder into that tank...du'h.