Not Foaming a Fuel Tank?

[ruckus reef]

I saw a video online about a mako that did not foam in the new tank post-repacement. Instead, thick neoprene rubber strips were stuck on the tank with 5200 to secure it (along with the fuel tank tabs screwed into the coffin box). The rationale of the video, the water is able to drain therefore protecting the tank from corrosion. My question is, does a fuel tank need to be foamed in. Further, what purpose does foam serve, protection? stability? floatation purposes?

I am curious as to what others think of this method of no foam, I searched but did not see an existing thread on the topic. Any insight would be appreciated.

[OceanBean]

I replaced the tank in my 17 ft two seasons ago. The tank manufacturer advised against foaming. He provided me plastic strips to rest the tank on the stringers. I then lag bolted into the sides of the coffin. It is not going anywhere. Airflow around tank is key. I confirmed this with other boat yard guys as the recommended installation method.

Oceanbean 1983 17 mako

[Justin]

This is a debated topic.

Most around here foam, after coating the tank in coal tar epoxy and glassing the coffin-to-tank area to minimize water ingress.

Some dont foam at all.

http://www.yachtsurvey.com/fueltank.htm

[mrdelgado]

Was the tank at least coated with epoxy? The big problem is there's no air circulation in the coffin to remove the moisture or condensation built up. Properly done, the foam would add protection from any moisture collecting on or against the tank

Also, for me, the idea of 700# + of fuel bouncing around, being supported by a couple tabs and 5200 ? no thanks

[ruckus reef]

What type of plastic was used?

quote:

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Originally posted by OceanBean


I replaced the tank in my 17 ft two seasons ago. The tank manufacturer advised against foaming. He provided me plastic strips to rest the tank on the stringers. I then lag bolted into the sides of the coffin. It is not going anywhere. Airflow around tank is key. I confirmed this with other boat yard guys as the recommended installation method.

Oceanbean 1983 17 mako

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[OceanBean]

strips of polycarbonate (plexi-glass)

[Triplecrownnc]

quote:

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Originally posted by OceanBean


strips of polycarbonate (plexi-glass)

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The tank is sitting on plexy strips and the tank (plastic) is lag bolted to the coffin?

[OceanBean]

Yes -

I tried to send you an email with more info, but could not.

I have pictures if interested. You might be able to email. I did not have enough posts to qualify for emailing.

[Triplecrownnc]

quote:

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Originally posted by OceanBean


Yes -

I tried to send you an email with more info, but could not.

I have pictures if interested. You might be able to email. I did not have enough posts to qualify for emailing.

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the e mail system within CM does not work. To post pictures, open and account with imgur, load up your pics and copy the link in your CM reply.

[OceanBean]

see if this link works.

https://imgur.com/GMOZbC1

The tank was made by RAM welding in Farmingdale, NY. They are a prominent tank fabricator. I installed per their instructions.

Note the 4 tabs welded to the tank. These allow the tank to be lag bolted to the coffin stringers. The tank is aluminum and epoxy coated. It holds 37 gals. Note I also drilled a drain hole in the back wall of the coffin so should any water get in, it will drain into the bilge. Otherwise the coffin is water tight so it would only accumulate. The tank is off the bottom of the boat as it is sitting on the stringers. Water runs under and out into the bilge.

I did a similar tank replacement on 1986 Gradywhite 22ft Seafarer. The GW tank was 93 gals. I replaced with a shorter tank but same shape to save some weight (about 62 gals). The boat was repowered with a heavier motor. Wanted to get the scuppers out of the water. The GW tank was original and not foamed in. It was framed into the hull with CCA lumber. It corroded on top where rubber pad were between the tank and wood. You will read now, that rubber padding is not recommended. That tank was over 30 years old. I have no doubt both of these tanks will outlive either me or the boats.

Oceanbean.

[Triplecrownnc]

Drilling a hole in the coffin so that water can leave the coffin and enter the bilge also allows water in the bilge to enter the coffin.Your tank will then be in direct contact with salt assuming you use the boat in salt water.

You mention you lag bolted to the 'coffin stringers'. To my knowledge that is just glass, no stringer behind that area. What did you find there?

[ruckus reef]

Thanks for the info, and the pic worked. I just picked up the tank from Atlantic Welding in NJ. The tank was epoxy coated at the fabricators recommended a no foam technique (rubber and 5200).

As for the drain into the bilge, I cut PVC tubes at an angle and used epoxy to hold them tight. I believe this will allow water to drain without bilge water entering the coffin.

[Mac25]

foam isn't the best ideal for fuel tanks, noodles do work good in place of foam, any coffin should have a way to drain when needed, a rubber bilge plug and transom drain works well as the coffin will sweat.

[Triplecrownnc]

quote:

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Originally posted by Mac25


foam isn't the best ideal for fuel tanks, noodles do work good in place of foam, any coffin should have a way to drain when needed, a rubber bilge plug and transom drain works well as the coffin will sweat.

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Noodles?[B)]

To each their own, there is absolutely no way I would leave to chance the possibility of a fuel tank breaking loose while I was offshore. I could possibly see this design in a lake boat or something. The exposed tank is going to sweat (a lot) as their is more exposed metal. The open drain to the bilge with introduce salt weather the water back fills or not.

The issue is mostly around not maintaining the tank and tank lid seal. Its not reasonable to expect a tank be installed, the lid sealed and then not look at it for 20-30 years yet that is exactly what happens. I pull my lid every 2 years, clean, inspect and reseal. You can look at my project thread as I just did this and you can see what a tank looks like in two years under the lid.

[Justin]

Non-foamed tanks are a great option if the boat is designed for it (ie structural members tied to stringers that tank sits on, elevated off the bilge bottom, etc)..

HOWEVER, non-foamed tanks are not ideal in most Makos, which just werent designed to support a non-foamed tank.

The foam is required to secure the tanks to the coffin, which is itself supported by a "floating deck." As someone mentioned, those coffins are 1/8" glass. Not enough to support the tank on its own.