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Author Topic: Foam for under and around poly tank?  (Read 705 times)

July 27, 2018, 04:53:35 PM
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theFunsmith

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Foam for under and around poly tank?
« on: July 27, 2018, 04:53:35 PM »
Is there a generally accepted optimal foam material for padding under and around a poly tank? Want to get the best stuff for chemical (gasoline) resistance, and a long life of vibration dampening. Basically, I don't want to ever have to remove the tank once it is installed. 

July 28, 2018, 08:15:36 AM
Reply #1

mshugg

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Re: Foam for under and around poly tank?
« Reply #1 on: July 28, 2018, 08:15:36 AM »
No foam will be gasoline proof.  That is to say that if exposed to raw gasoline for an extended period of time, it will absorbe some gas.  Useing denser foam means less airspace and therefore less potential to absorb either water or gas.  I think that 4lb foam is standard for foaming in aluminum tanks.

With that said, you’re in uncharted territory foaming in plastic.  Moeller says to allow 3% expansion in all directions for hydrocarbon swell (Example: Initial size 40"L x 24"W x 18"H = Expanded size 41.2"L x 24.7"W x 18.5"H). Moeller also says:  DO NOT FOAM THE FUEL TANK IN PLACE!  The all caps and exclamation point are theirs.

If you’re not talking foaming in the tank, they recommend neoprene padding anywhere chafe can ocur.

July 28, 2018, 01:39:15 PM
Reply #2

theFunsmith

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Re: Foam for under and around poly tank?
« Reply #2 on: July 28, 2018, 01:39:15 PM »
Thank you for the reply. I wasn't talking about pour style foam, but more like a roll of foam rubber. Neoprene foam was a common one I was seeing, but there were like 10 different kinds of foam materials that looked similar out there, and I wanted to make sure whatever I ordered wasn't going to degrade in a couple years.

July 30, 2018, 06:15:13 PM
Reply #3

theFunsmith

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Re: Foam for under and around poly tank?
« Reply #3 on: July 30, 2018, 06:15:13 PM »
While getting more confirmation on Neoprene as the go-to padding material, I found some other good stuff straight from the horses mouth on installation, in case anybody else finds themselves in the same spot I am.

To obtain optimal performance from your Moeller Marine fuel tank, it is important that you follow
these installation guidelines closely.

1.Follow all applicable ABYC, ISO, NMMA, and USCG regulations and recommendations.

2.The fuel tank must be fully supported in its installed position.

3.The fuel tank should be installed securely. The installed fuel tank shall not bounce, shift, or move as this will cause chaffing. The fuel tank shall not be allowed to be scraped, cut, or punctured because of a loose installation or manufacturing debris. IMPORTANT: Neoprene padding should be added to any area where the surface of the tank makes contact with a surface that may cause chaffing. DO NOT COMPRESS NEOPRENE PADDING!

4.Allow 3% expansion of the fuel tank in all directions. Hydrocarbon swell occurs when gasoline or diesel fuel soaks into the fuel tank material. (Example: Initial size 40"L x 24"W x 18"H = Expanded size 41.2"L x 24.7"W x 18.5"H) Design the fuel tank compartment to allow growth equally. Hold down brackets / braces must be installed to prevent damage to the fuel tank even after hydrocarbon expansions occur.

5.DO NOT remove dust caps until you are ready to install the fuel tank. Dust caps are provided to limit dirt, dust, water or any other foreign substance from getting into the fuel tank.

6.Fuel tank placement should be carefully considered, as certain environmental factors can increase fuel temperature, leading to potential degradation of fuel integrity and related problems.

7.DO NOT deform the tank during installation. Methods of deforming the fuel tank also include: walking, standing, or applying excessive weight onto the fuel tank.

8.DO NOT solid plumb fuel lines to the fuel tank use only flexible lines.

9.DO NOT FOAM THE FUEL TANK IN PLACE!

10.NEVER modify the fuel tank. Use only fittings which come with the tank, or fittings approved by Moeller Marine.

11.DO NOT attempt to patch or repair holes or punctures in fuel tank.

12.Fuel tank temperatures need to be stabilized to room temperature for 24 hours before testing or installation.

July 30, 2018, 07:18:19 PM
Reply #4

RickK

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Re: Foam for under and around poly tank?
« Reply #4 on: July 30, 2018, 07:18:19 PM »
They used to, or maybe still do, make interlocking 1/2" thick rubber (or something spongy) floor mats/pads.  My buddy had some in his boat and he gave me a couple which I cut into 1/2" strips and contact cemented the strips onto the supports and on the sides & ends of the tank well. You can see the strips in my rebuild thread. (Rickk's 170 Rebuild)
Rick
1971 "170" with 115 Johnson (It's usable but not 100% finished)

1992 230 Explorer with 250 Yamaha

July 30, 2018, 07:24:16 PM
Reply #5

theFunsmith

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Re: Foam for under and around poly tank?
« Reply #5 on: July 30, 2018, 07:24:16 PM »
Rick,

Those foam pads look good, but I wasn't sure what they were made of. Murphys law being what it is, I just wanted to make sure I didn't use something that liquified if some gas leaked onto it. Just want to do it right, so I don't have to go back in there. I want to do it without a true coffin lid, using deck plate style access ports to hose and sender points.

 

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