Cutting into glassed in fuel tank

[jmm4jmc]

I have a fiberglass/foam core hull with four glassed in (gas) tanks. The glass over four of the tanks in the pilot house floor is spongy. Seems the fuel has eaten away at the foam. Just a guess. What is the easiest way to cut into the fiberglass top to inspect the tank with out worrying about explosion. Air saw? My goal is to check the insides of the tanks for any structural damage etc, then abandon. I will then put in a plastic tank in another accessible location.

Any thoughts or advice would be much appreciated.

Jim

[Herman]

fill the tanks with water, then cut open (with reciprocating or oscilating saw, as that will make the least mess). It is better to have a (limited) flood, than a gasoline explosion.

Do protect yourself, however. Wear rubber gloves. Electricity and water...

gasoline fuel and polyester do not mix well. Diesel and water are ok in certain circumstances. For gasoline there are some limited options.

[jehardiman]

Originally Posted by Herman

fill the tanks with water, then cut open (with reciprocating or oscilating saw, as that will make the least mess). It is better to have a (limited) flood, than a gasoline explosion.

Do protect yourself, however. Wear rubber gloves. Electricity and water...

gasoline fuel and polyester do not mix well. Diesel and water are ok in certain circumstances. For gasoline there are some limited options.

Yes, to fill with water is the correct method. But plumb it up so that you can compleatly fill the tank and force the gas out the vent.

In most tanks there will be 1/2" or so of gas/sediment mix below the pickup. Drain the tank completely if it has a sump valve, then fill the tank almost full with water (hot if you can). Give it time to let the gas float on water, then slowly overfill the tank, forcing the residual gas out the tank vent outside the hull until water is comming out to prevent fumes inboard (remember to collect the overflow...EPA regs and all that). Make a quick cut at a known submerged spot high in the tank big enough to get a ventlation suction hose into then start pulling fumes out of the tank as you drain it. Depending on the temperature, pull ventlation for a day or two to get all the surface flim offgassed and any that may have saturated the core before making a "hot" cut. Remember that gas fumes are the issue here and that they are havier than air and will collect in the low/enclosed places.

At the end of the repairs, wipe down the inside of the tank with alcohol before sealing it, and add some "dry gas" or alcohol to suck up and residual water.

[jmm4jmc]

Thanks guys for the info, very helpful