Fuel tank install with water under to bilge

[kcassells]

Hey general population. I see a lot of guys putting fuel cells/tanks and letting water run under them back to the bilge.
To me a gas tank is supposed to be placed into a "coffin" as a sealed unit. Not using the hull as a base structure to support the tank.
I know it's your boat and you can do what you want.
How do all you rehabbers feel about this and what's your opinions.
I am interested in this and would like to see the overall population make comments.

 

[JASinIL2006]

My boat was built to allow water to run under the fuel tank (from the ski locker) and out the back into the bilge. I kept it that way when I restored it.

 

[GA_Boater]

The coffin is meant to contain fuel from a ruptured tank or hose so you and the passengers don't spend eternity in one.

 

[chevymaher]

Way mine was built as well. I was concerned when you mentioned it. But if it was sealed no drainage from the skii locker if changed. And I looked hard nobody ever changed it in any rebuild I ever saw.

Sealed areas with vapors are the real grenades. All the gas in the tank is being pumped to the bilge anyway. There is a dozens of places it could leak from in there. I googled it and found zero problems with tanks being that way. Fuel pumps filters and hoses. Fuels systems both carb and fuel injection now there are your fire and explosion culprits 99.9% of the time.

After massive reading I kinda came to the conclusion. In a small boat with no cabin. Open air there is little danger. Hard to build up vapors in a bucket in the middle of a open field. Have you ever tried to light gas not happening in the liquid state. With no sealed room it is removed by a simple breeze. If your tank is leaking bad enough to be a issue it gonna smell like gas.

Problem is when the tank and engine compartment are sealed under the deck. Now there is a large area that gas vapors can fill and that is alot of boom. In a space sealed so you don't smell it and have no warning. In a larger boat like that the coffin system seals the area the vapors can gather to a small as a area as possible.

I based my decision to leave the way it is on 2 things.

1. There are now and never were reports of boats going boom from gas tanks being in this configuration.

2. Gov agencies are nasty unthinking unfeeling people. Love to push people around over the simplest stupid things. If there was any issue at all they would not let boat manufacturers build them that way to this day. I am sure they have tested and exploded boats on purpose trying to make a problem that don't exist.

 

[tpenfield]

The fuel tank bays on both my recent boats we not fully sealed coffins. They were open at the top. Leaking fuel could not readily get into the bilge because of solid bulkheads both front and back of the tank. But any fumes from the tank could/would vent to other areas of the boat.

Water from the forward section of the boat was/is channeled under the fuel thank by via a sealed conduit/hose.

The tank essentially rested on the hull although supported by neoprene strips.

So, not a fully sealed ‘coffin’ is not typical on all boats, but common on smaller boats with belly tanks.

 

[harringtondav]

I've never heard of a 'coffin' fuel tank enclosure. It sounds like an industrial tank farm enclosure. I'm thinking once a fuel tank leaks, fumes are the greatest hazard. It would seem fuel in the bilge would be the earliest method of detection vs. having the stuff accumulate hidden under the floor. The few boat gas tanks I've seen are set somewhere on the hull, with a drain channel if located on center. I go for belt and suspenders in some instances. This one doesn't make sense to me.

 

[steve_h7]

Fwiw my project was originally manufactured in Canada (Campion) and the tank was built all the way in the rear of the boat so the tanks level gauge, inlet, and breather tubes all have open access near the bilge. If I was to put it back in it's stock location and seal it, it would prevent everything from the bow towards the tank from being able to reach the bilge.

 

[kcassells]

Thanks guys for the feedback. I appreciate it. This is one of the mysteries to me and coast guard regs. I will be placing a sniffer alarm in my coffin in any event.

 

[mickyryan]

here is issue i see with coffin idea , by the time you know there is a leak the leaked fuel is all over inside and can possibly soak into stringers and making vapor where as if it leaks into bilge you immediately know there is a issue and can resolve it.

 

[kcassells]

I have no issue with the coffin, I feel safer. A sniffer will let me know whats up Doc before all that happens. The fuel to the battery compartment would be my scare.
I have also seen guys put a valve off the box for check ups now and then, That seems plausible.

 

[Bondo]

To me a gas tank is supposed to be placed into a "coffin" as a sealed unit.

Ayuh,..... I disagree, as in my experiences, Any sealed compartment in a boat, is a water-trap,.......

My thought is, Any, 'n Every compartment should be self-draining to the bilge,......

 

[kcassells]

Ayuh,..... I disagree, as in my experiences, Any sealed compartment in a boat, is a water-trap,.......

My thought is, Any, 'n Every compartment should be self-draining to the bilge,......

I agree to disagree!:joyous: Good hearing from ya Bondo

 

[zool]

Ayuh,..... I disagree, as in my experiences, Any sealed compartment in a boat, is a water-trap,.......

My thought is, Any, 'n Every compartment should be self-draining to the bilge,......

Yup, 30 years later any my substructure was mostly solid wood with that exact setup

 

[kcassells]

All compartments self draining to the bilge hmmmm I like that idea too!

If only there was a way to do that with 2 part foam...hmmmmm.

 

[mickyryan]

I am so happy My boat has no foam

 

[Redfred1]

Ayuh,..... I disagree, as in my experiences, Any sealed compartment in a boat, is a water-trap,.......

My thought is, Any, 'n Every compartment should be self-draining to the bilge,......

Plus 1! I agree with Mr Bondo.

 

[Bondo]

All compartments self draining to the bilge hmmmm I like that idea too!

If only there was a way to do that with 2 part foam...hmmmmm.

Ayuh,...... If you put limber holes in all the stringers, 'n bulkheads, the water will weep to the bilge, under the foam,......



Not that I'd put foam in a boat,....
'cause closed cell or not, over time, it All holds water,..... Especially if the hull isn't self-drainin',.....

 

[kcassells]

Takes along time to rot the foam to make the water pass. By that time the wood/glass is compromised. JMHO.
Most of, no nearly all results of that scenario you suggest typically fail with water being trapped by foam.
The foam adheres to the glass/wood. Closed cell, water eventually corrupts it to open cell. Total failure. Rot from bottom up.

 

[kcassells]

Water takes the path of least resistance... above does not demonstrate that.

 

[Bondo]

Ayuh,...... Not arguin' yer points,..... My point is, without limber holes to drain any water, the hulls gonna rot anyways,.....

You could put down a sheet of poly to stop the foam from stickin' to the bottom,.....
The water will then weep to the limber holes, 'n then drain,.....

In a sealed cavity, the water just gathers, when it freezes, the foam gets destroyed, turned into a sponge,....