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Aluminum Fuel Tank and Foam????

Old 08-07-2011, 09:32 AM
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Default Aluminum Fuel Tank and Foam????

I was wanting to know if this would create a problem down the road?

If you install an aluminum fuel tank and just foam it in (without putting a coating on the aluminum" or securing the tank down (relying on the foam to hold it in place).

Will this cause the aluminum to corrode?
Old 08-07-2011, 09:35 AM
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Originally Posted by silver bullet View Post
I was wanting to know if this would create a problem down the road?

If you install an aluminum fuel tank and just foam it in (without putting a coating on the aluminum" or securing the tank down (relying on the foam to hold it in place).

Will this cause the aluminum to corrode?
A lot of tanks have been installed over the years with foam. For the $100 +/- that coal Tar coating cost, I would not take any chances.
Old 08-07-2011, 09:48 AM
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Originally Posted by silver bullet View Post
I was wanting to know if this would create a problem down the road?

If you install an aluminum fuel tank and just foam it in (without putting a coating on the aluminum" or securing the tank down (relying on the foam to hold it in place).

Will this cause the aluminum to corrode?
You might want to check on the most recent regulations as to foaming in a tank.
For the very most part, the very most, it's no longer done.
It can be, but must be in such a way that it's impossible for the foam to allow any standing water, to capture any water at all.
Before you do it, look into it some.
You might not want to foam in the tank at all.
Today it is done, but the great exception.

There are published regulations as to installling a fuel tank, NMMA, ABYC, and USCG.

I'd strongly reccomend you look into it before doing it.
Old 08-07-2011, 09:53 AM
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Originally Posted by silver bullet View Post
I was wanting to know if this would create a problem down the road?

If you install an aluminum fuel tank and just foam it in (without putting a coating on the aluminum" or securing the tank down (relying on the foam to hold it in place).

Will this cause the aluminum to corrode?
I believe this is also against regulation.....the foam cannot be the only means of support (anymore).....you'll need fuel tank stringers or brackets that bolt to other structure/stringers

as far as corrosion...either let it breath and oxidize itself, or seal it completely on all sides to keep moisture off of it......if moisture gets trapped against it anywhere, thats where corrosion will take over. The old foam in jobs left the tops exposed, allowed moisture to sit there and even travel down the sides, get trapped between the tank and foam, then corrode.
Old 08-07-2011, 10:45 AM
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I took the deck lids off my tanks on my '07 32' SeaVee to put in deck sensors for an alarm. The tanks were not coated - seemed fine - I think I recall they were foamed in as well.
Old 08-07-2011, 10:59 AM
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Originally Posted by maxie View Post
I believe this is also against regulation.....the foam cannot be the only means of support (anymore).....you'll need fuel tank stringers or brackets that bolt to other structure/stringers

as far as corrosion...either let it breath and oxidize itself, or seal it completely on all sides to keep moisture off of it......if moisture gets trapped against it anywhere, thats where corrosion will take over. The old foam in jobs left the tops exposed, allowed moisture to sit there and even travel down the sides, get trapped between the tank and foam, then corrode.
Maxie,
Somewhat of a paradox for me.
As I understand the NMMA, ABYC, and USCG, yes, I guess you can, if you can stipulate it meets spec, which in my thinking, Ok, you can, but in reality I dont know how you can meet spec if foaming a tank in.
Is that a "Paradox" or an "Oxymoran"?

In any event, I think today tanks are very seldom foamed in place.
Old 08-07-2011, 11:08 AM
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Need to anchor it to stringers with tabs etc. Coal tar epoxy it if in an area where a lot of water has potential to get on top. If foaming in make sure no cavities on the sides for water to get and sit. That's one of the biggest issues with foaming in tanks is people don't do it right.
Old 08-07-2011, 11:42 AM
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redoing my 88 privateer, foam on top, and an airspace underneath, and a place cut in all bulkheads for water to move. i'll take another 23 out of the next one
Old 08-07-2011, 11:53 AM
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Originally Posted by Touche View Post
I took the deck lids off my tanks on my '07 32' SeaVee to put in deck sensors for an alarm. The tanks were not coated - seemed fine - I think I recall they were foamed in as well.




They are now coated and bonded.
Old 08-07-2011, 11:56 AM
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Lots of info on this thread concerning foam filled aluminum tanks.

http://www.thehulltruth.com/boating-...uel-tanks.html
Old 08-07-2011, 12:27 PM
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How are Contender fuel tanks now installed?

In the past, I know for a fact, that some older Contenders had fuel tank leakage to their aluminum tanks.

Why would a quality boat builder not use Coal tar epoxy?

I have been told by Yellowfin and Contender that they do not use Coal tar epoxy on tanks but would add it if I wanted it. Invincible does use coal tar epoxy.

Foamed in aluminum tanks will all eventually fail due to moisture causing corrosion. It may take ten years or longer, but it will eventually happen.
Old 08-07-2011, 12:33 PM
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Originally Posted by mike carrigan View Post
Maxie,
Somewhat of a paradox for me.
As I understand the NMMA, ABYC, and USCG, yes, I guess you can, if you can stipulate it meets spec, which in my thinking, Ok, you can, but in reality I dont know how you can meet spec if foaming a tank in.
Is that a "Paradox" or an "Oxymoran"?

In any event, I think today tanks are very seldom foamed in place.
Yeah, I don't think too many are foamed in, but some still are...I think I recall YF still does??

Anyway, I helped someone pull a foamed tank a few years ago, and anywhere the foam was wet and up against the tank, it was severely corroded.....so we looked at where the water was coming from.....we found 2 major issues

1) the fuel hatch and those POS pie plates continually let water into the coffin....with foam surrounding the tank, and in some spots not very level, creating pools of water....this water sat on top of the tank and worked its way down between the foam and tank and sat there...bad news.....and the foam from 20 years ago absorbed water more than the ones made today.

2) since the tank was ONLY supported by foam, it jockeyed around a little..but that was enough to crush the PVC drain pipe running underneath it in the coffin. The water coming from the anchor locker and a fish box/storage box went through this tube and hence added to the foam/moisture issue from underneath.

so to take care of the issue with water, we first replaced and beefed up the PVC drain area...is was just caulked in originally...so we glassed it in and made sure the areas around the bulkeads were water tight......

we then had the new tank made with brackets/tabs and bolted the tank to the stringers so it basically 'hung" in place....this will keep the tank from moving/bouncing and crushing the PVC tube again and gives access to pour in the foam....this takes care of one of the regulations.( 2 means of support when foamimg) We also coated the tank with Interprotect after proper etching/prep...same as you would running gear or aluminum engine brackets. The big thing to use these days is coat tar epoxy? either way I guess, both seal the metal surface.

then we foamed it in with 4lb foam, not 2lb.....after letting it expand completely for a couple of days, we carefully trimmed the excess foam on a bevel ( you don't want to nick the newly primed surface as that will attract water intrusion) so that any water that may get in will drain off the top of the tank and head towards the stern.....we drilled and installed a PVC drain hole at the foam level at the aft bulkhead to allow water to run off and out into the bilge...this has a plug, just like you do for a bottom fuel tank compartment....just open it up once in a while to get whatever is there out.....We then glassed the top of the tank and the cut foam to seal it from water....this also keeps the fuel lines from rubbing against the tank and damaging the epoxy.....then a new pie plate and O ring for inspection and resealed the hatch.....

The tanks on my boat are exposed all around...when its time for replacement, they will stay that way...just need to keep water out of there
Old 08-07-2011, 12:51 PM
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I don't care how well it's built water will find a way! When I had my Yellowfin built it was a no brainer to protect the fuel cell with Line-X! We acid washed it, primed it and applied around 90 mils of Line-X. Yellowfin then foams and screws the tanks to the stringer system. My tank is forever!







Andros 32' tanks


MRAP tanks-
Old 08-07-2011, 01:08 PM
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Originally Posted by yz250b View Post
I don't care how well it's built water will find a way! When I had my Yellowfin built it was a no brainer to protect the fuel cell with Line-X! We acid washed it, primed it and applied around 90 mils of Line-X. Yellowfin then foams and screws the tanks to the stringer system. My tank is forever!







Andros 32' tanks


MRAP tanks-
nice! what would that run for say a 100g tank?
Old 08-07-2011, 02:19 PM
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Originally Posted by maxie View Post
Yeah, I don't think too many are foamed in, but some still are...I think I recall YF still does??

Anyway, I helped someone pull a foamed tank a few years ago, and anywhere the foam was wet and up against the tank, it was severely corroded.....so we looked at where the water was coming from.....we found 2 major issues

1) the fuel hatch and those POS pie plates continually let water into the coffin....with foam surrounding the tank, and in some spots not very level, creating pools of water....this water sat on top of the tank and worked its way down between the foam and tank and sat there...bad news.....and the foam from 20 years ago absorbed water more than the ones made today.

2) since the tank was ONLY supported by foam, it jockeyed around a little..but that was enough to crush the PVC drain pipe running underneath it in the coffin. The water coming from the anchor locker and a fish box/storage box went through this tube and hence added to the foam/moisture issue from underneath.

so to take care of the issue with water, we first replaced and beefed up the PVC drain area...is was just caulked in originally...so we glassed it in and made sure the areas around the bulkeads were water tight......

we then had the new tank made with brackets/tabs and bolted the tank to the stringers so it basically 'hung" in place....this will keep the tank from moving/bouncing and crushing the PVC tube again and gives access to pour in the foam....this takes care of one of the regulations.( 2 means of support when foamimg) We also coated the tank with Interprotect after proper etching/prep...same as you would running gear or aluminum engine brackets. The big thing to use these days is coat tar epoxy? either way I guess, both seal the metal surface.

then we foamed it in with 4lb foam, not 2lb.....after letting it expand completely for a couple of days, we carefully trimmed the excess foam on a bevel ( you don't want to nick the newly primed surface as that will attract water intrusion) so that any water that may get in will drain off the top of the tank and head towards the stern.....we drilled and installed a PVC drain hole at the foam level at the aft bulkhead to allow water to run off and out into the bilge...this has a plug, just like you do for a bottom fuel tank compartment....just open it up once in a while to get whatever is there out.....We then glassed the top of the tank and the cut foam to seal it from water....this also keeps the fuel lines from rubbing against the tank and damaging the epoxy.....then a new pie plate and O ring for inspection and resealed the hatch.....

The tanks on my boat are exposed all around...when its time for replacement, they will stay that way...just need to keep water out of there
The benefit of foaming a tank in place totally eludes me.
Why?
Not stronger, more possiblity of water collecting where it's not wanted.
What's the upside, the advantage?
To me it's thirty year ago stuff and older that has progressed far beyond foaming in a tank.
Old 08-07-2011, 02:54 PM
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Originally Posted by mike carrigan View Post
The benefit of foaming a tank in place totally eludes me.
Why?
Not stronger, more possiblity of water collecting where it's not wanted.
What's the upside, the advantage?
To me it's thirty year ago stuff and older that has progressed far beyond foaming in a tank.

Some of the pics above are bad news, no thought has been given to maintenance.
All it takes is a pin hole in the bottom of the tank and the substructure of the boat has to be cut apart,
just to get the tank out?

Tanks are very cheap compared to having to cut the deck and stringers up to remove them.
I pulled the 60 gal tank out of my 40 yr old chrysler in less than 45 minutes without having to cut anything,
thats engineering. No foam, large access hatch.
Old 08-07-2011, 03:06 PM
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Originally Posted by mike carrigan View Post
The benefit of foaming a tank in place totally eludes me.
Why?
Not stronger, more possiblity of water collecting where it's not wanted.
What's the upside, the advantage?
To me it's thirty year ago stuff and older that has progressed far beyond foaming in a tank.
Benefit? good question.....I would leave mine open, just like the factory did it.....maybe some boat builders use the foam as added structure?Doesn't it help a little when placed between stringers? Added floatation? Sound deadening?

especially those go fast boats...lots of potential movement at 80mph hitting waves?
Old 08-07-2011, 03:58 PM
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Is this tank done right?
Old 08-07-2011, 04:02 PM
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Translation:

"Hey, will you guys look this over and see if you can help me find another way to flame Yellowfin boats?"
Old 08-07-2011, 04:03 PM
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Why would a boat builder not spend $100.00 on the coat tar epoxy?

This tanks looks like it was foamed in and was NOT even coated.

Is this done right? The pic's of the fuel tanks that are coated looks great.

When you get a boat built is this another one of those things that you need to tell your "top tier boat builder to do"?

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