Securing under floor gas tank

Realgun

Commander
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Jul 31, 2003
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2,484
As I have been getting ready to install floor I need to know how to install fuel tank.<br />It was sitting on 4 thin strips of rubber. The left and right sides were filled with chopped glass/poly about 10 inches long. this was obviously poured from the top and made a circle that went over the tank about 3 inches and down sides about the same. There was some sort of black rubber foam that held the rear of the tank.<br />What is this foam?<br />Tank is 24 inches wide and 42 inches long about 6 inces deep maximum and V shaped to snugle to the floor. The cavity is about 43 inches long and 24.5 inces wide. Floor is about 1/2 inch higher than tank. Also there was a plastic bag? on top of the tank that was covering the rear under the floor but not the entire tank it was stuck to poly and was there when tank was installed.<br />I installed a new float already.<br />Help me mount it properly.
 

cc lancer

Petty Officer 1st Class
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Aug 23, 2004
Messages
371
Re: Securing under floor gas tank

How thick was the black rubber foam?<br /><br />This is a different installation to what I have seen.
 

Winger Ed.

Chief Petty Officer
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Mar 24, 2004
Messages
649
Re: Securing under floor gas tank

That plastic may have been either to keep water from puddeling on top of the tank and maybe leak through the sender seal, then into the tank itself. Or, maybe the crew at the factory just tossed it in there instead of going over to the trash can.<br /><br />There's lots of ways to mount it, the rubber gives it some cushion, and won't rot very fast while letting water drain out from under it.<br /><br />The big thing about mounting the tank is keeping it from becoming under (bilge)water and leaking through the top; and setting it so it won't move around with vibration and chafe a hole in itself.
 

Boomyal

Supreme Mariner
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Aug 16, 2003
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Re: Securing under floor gas tank

Realgun, my tank was set on 4 blocks. The top of the tank had strips of dense foam weatherstrip laid across it. Foam was first poured into the bay and the tank set down on top of it. I think they must have laid the bay cover on and let the foam push the tank up against the underside of the cover.<br /><br />When the I went to remove the tank it's lower half was securely embedded in foam. There was no possibility of movement or chaffing.<br /><br />
035914.jpg
<br /><br />This is how it looked before I removed it.+<br /><br />
035915.jpg
<br /><br />Although this worked well for my boat, different construction may require different mounting proceedures.
 

prockvoan

Chief Petty Officer
Joined
Jul 27, 2004
Messages
512
Re: Securing under floor gas tank

Installing a gas tank with foam is a BIG NO NO!Go to www.uscg.gov They have the right way to do it.Another thing,don't use any type of rubber under your tank,if water(more in saltwater)the rubber gets wet,water releases the carbon in it,which eats the alum.I know,I'm replacing 2 100 gal tanks.
 

Realgun

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Re: Securing under floor gas tank

Your link no workie however- this site :) has information I might use.<br /><br />Acording to all the rules, and there are quite a few, it looks like I can secure the sides, rear and front with the 2-part foam I already have. <br />As long as I do not block water from dripping off the top.
 

prockvoan

Chief Petty Officer
Joined
Jul 27, 2004
Messages
512
Re: Securing under floor gas tank

Realgun,close cell foam will in fact suck up water in time.Its' not suppose to,but it does.What weight foam you are planning to use?If you do,watch out on how much you pour at a time.It can crush your tank or crack it.Make sure the tank is clear of gas.As the foam cures,it puts out alot of heat.I don't think that you want to do the spaceship one thing.
 

crab bait

Captain
Joined
Feb 5, 2002
Messages
3,831
Re: Securing under floor gas tank

foam in a plastic tank is baaaad.. the foam an plastic combo,, makes for major condensation INSIDE the tank.. i.e. tank-fulla-water.. <br /><br />MUST HAVE AIR GAP ALL AROUNND THE TANK..<br /><br />mite be same for alum.tanks,, i don't know..
 

mellowyellow

Vice Admiral
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Jun 8, 2002
Messages
5,327
Re: Securing under floor gas tank

ditto crab, strap it down and let air circulate<br />all around it.
 

Realgun

Commander
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Jul 31, 2003
Messages
2,484
Re: Securing under floor gas tank

Cannot strap it down. The compartment it sits in is almost the same size as the tank. It was secured on top with some chopped glass that was poured near edges. There is/was a 1/4 gap beteen stringers and tank. Floor sits 1/2 inch above floor. Front and rear are 1/2 inches from the bulkheads. Tank was sitting on 4 1/4x42 inch neoprene strips which I still have. <br /><br />I do know about foam and such no worries here. Acording to the rule I have sited above it requires at least 2 pound polyurethane foam.<br />If I use it to secure tank but not to float boat it only has to not absorb water for 24hrs.<br /> This table shows what is required.
 

prockvoan

Chief Petty Officer
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Jul 27, 2004
Messages
512
Re: Securing under floor gas tank

Ever leave your boat in the water over night or the weekend?
 

fireman57

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Aug 24, 2004
Messages
3,811
Re: Securing under floor gas tank

Hey Boomyal! There is the ever present disappearing rope again!
 

Realgun

Commander
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Jul 31, 2003
Messages
2,484
Re: Securing under floor gas tank

Ever leave your boat in the water over night or the weekend?
My boat has been off the trailer and in the water a total of 3 hours in the last two years. :) <br /><br />I understand the point however I am using the foam to secure the tank not float the boat. The tank sits over the bildge in a compartment designed for it. <br /><br />Would it be better to just mix some milled glass and epoxy to peanut butter consitancy and put it on the two sides as it was before? I had no issues with the polyester epoxy coming off tank but real epoxy is never coming off. And what was/is that black rubber stuff that was stuck to the bulkheads and tank feels like rubber but seems like neoprene? Will I need that to keep tank from possibly sliding back and forth?
 

Realgun

Commander
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Jul 31, 2003
Messages
2,484
Re: Securing under floor gas tank

Ok people still need help with gap at rear of tank.<br />I placed the four strips of rubber/neoprene back under tank and mixed 1/8" glassfibers and epoxy to peanut butter consistancy and spread that along top of tank edges and stringers.<br />Still have a gap at rear front was secured like sides. There is a gap all around tank at least 1/4".<br /><br />Cavity-<br />
038043.JPG
<br />Sides secured-<br />
038047.JPG
<br />See gap-<br />
038045.JPG
 
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