Fuel Tank

[Destroyer]

Originally Posted by jasoncooperpcola

Wont expanding foam collapse the tank some and not allow for hydrocarbon swelling?

Good questions. My answers would be
1) I don't think so
and
2) I don't think so.

If you just foam the bottom of the tank and maybe a quarter to a half up the sides that shouldn't collapse the tank at all. And since the top and the sides would be free of foam any expansion should be able to happen without a problem.

Remember the original question was what was the best way to mount the tank. Foaming is ideal, since the expanding foam locks the tank in place. The problem with foam has always been if you need to remove a foamed in place tank it's a real bear. But by wraping the tank in a plastic film, you solve that problem. The foam adhears to the plastic film, not the tank, so removing the tank is as easy as simply cutting the film and lifting the tank out.

Understand this is just my opinion, but really, I cannot see any downside to it. Can anyone else see any problems? I see this as one of those "so simple it's a wonder why no one thought of it before" type of problems.

[cterrebonne]

Originally Posted by Destroyer

Good questions. My answers would be
1) I don't think so
and
2) I don't think so.

If you just foam the bottom of the tank and maybe a quarter to a half up the sides that shouldn't collapse the tank at all. And since the top and the sides would be free of foam any expansion should be able to happen without a problem.

Remember the original question was what was the best way to mount the tank. Foaming is ideal, since the expanding foam locks the tank in place. The problem with foam has always been if you need to remove a foamed in place tank it's a real bear. But by wraping the tank in a plastic film, you solve that problem. The foam adhears to the plastic film, not the tank, so removing the tank is as easy as simply cutting the film and lifting the tank out.

Understand this is just my opinion, but really, I cannot see any downside to it. Can anyone else see any problems? I see this as one of those "so simple it's a wonder why no one thought of it before" type of problems.

Other than the foam melting the plastic, But you can use other types of plastic, PVC, Vinyl, etc. Or maybe that it might hold more moisture against the tank. But if its a plastic tank it won't matter and you can always cold tar aluminum if you are worried. Sounds like a good idea. You might be on to something.

[awthacker]

The downside to it for my application is that the foam will soak up and become saturated with water. The 1" PVC pipe from the cuddy to the bilge appears to be a plan gone wrong. Water has for years been getting trapped against the bulkhead and rotted the bottom of it out. So I cut the bottom of the bulkhead away, and fiberglassed it to seal the wood from further ater damage. I removed the PVC pipe and water will freeflow from my cuddy to my bilge along the hull bottom. I can't have foam in there or it will get soaked, as well as impede the movement of water.

Maybe I could build a raised shelf and cover it with a shower pan then rest the tank on top of that? But I was thinking more along the lines of installing some 1x4's above and in front/back of the tank to keep it from moving or floating.

[Destroyer]

Originally Posted by awthacker

The downside to it for my application is that the foam will soak up and become saturated with water. The 1" PVC pipe from the cuddy to the bilge appears to be a plan gone wrong. Water has for years been getting trapped against the bulkhead and rotted the bottom of it out. So I cut the bottom of the bulkhead away, and fiberglassed it to seal the wood from further water damage. I removed the PVC pipe and water will freeflow from my cuddy to my bilge along the hull bottom. I can't have foam in there or it will get soaked, as well as impede the movement of water.

Maybe I could build a raised shelf and cover it with a shower pan then rest the tank on top of that? But I was thinking more along the lines of installing some 1x4's above and in front/back of the tank to keep it from moving or floating.

Hmmmm.... Well, wrapping plastic around foam can work from both directions. Why not put a 1/2" or 3/4" PVC pipe in the bilge area for any water to flow thru, then put Visqueen or some other kind of plastic sheeting over the pipe all the way to the top of the bulkhead, shape it as best as possible with duct tape to mirror the cavity where you're going to put the tank. Wrap the tank and put the tank where you want it, put some heavy weights (sandbags?) on top of the tank to keep it from shifting as the foam expands and then pour the foam mixture between the tank and the plastic sheeting. The foam will expand and take the form of the cavity on the bottom and the form of the tank on the top, the plastic sheeting will become a permanent water barrier between the foam and the bilge area, and the plastic pipe will become a conduit for water from the front of the boat to the rear...

OR

You could make a rectangular box out of 2x4's or 2x6's or whatever, that equals the height of your tank. Fiberglass or polyurathane the wood to seal and protect it. Then put the tank where you want it, place the box around the tank and fiberglass it in place. Take two additional boards, place them across the top of the tank and screw them onto the rectangular box to lock the tank down and you're good to go.