I need to re-install a diesel tank. It was foamed in place and an then tab
glassed to the top of the bulkhead and hull. No problem with the glass work
but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan

Now THAT is one thing I can definitely quote chapter and verse because
everything I have ever seen says DO NOT use foam around a metal tank.
Especially a stainless one. It will hold oxygen depleted stagnant water
against the metal and create ideal conditions for crevasse corrosion.

Stainless needs a constant supply of oxygen be it in air or desolved in
seawater to maintain the protective surface. Tanks should be mounted so
that air can get to all surfaces. A lot of small Neoprene pads is
better than having the tank rest on a large surface that impeeds
circulation.

While I do not agree with David Pascoe on some things he has a good
section on mounting metal tanks on his survey page.

Bryan B wrote:

I need to re-install a diesel tank. It was foamed in place and an then tab
glassed to the top of the bulkhead and hull. No problem with the glass work
but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Hi Glenn,

Thats what I have read also but the other two tanks are foamed in. The boat
was built by the Bruckamn yard of C&C, which was the custom yard. I thought
maybe there was a foam that was breathable and used for this application.

Confused in Ohio.

Bryan

"Glenn Ashmore" wrote in message
news:mczjb.78272$sp2.67348@lakeread04...
Now THAT is one thing I can definitely quote chapter and verse because
everything I have ever seen says DO NOT use foam around a metal tank.
Especially a stainless one. It will hold oxygen depleted stagnant water
against the metal and create ideal conditions for crevasse corrosion.

Stainless needs a constant supply of oxygen be it in air or desolved in
seawater to maintain the protective surface. Tanks should be mounted so
that air can get to all surfaces. A lot of small Neoprene pads is
better than having the tank rest on a large surface that impeeds
circulation.

While I do not agree with David Pascoe on some things he has a good
section on mounting metal tanks on his survey page.

Bryan B wrote:

I need to re-install a diesel tank. It was foamed in place and an then
tab
glassed to the top of the bulkhead and hull. No problem with the glass
work
but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

A lot of production builders foam in their tanks. It is less expensive
and quieter. One thing about regulations. If you don't like one you
can probably find another that says something different. And if you
can't find one you can lobby your congressman to create one more to your
liking. :-) In this case 33 CFR 183.516(c) says you can use
polyurethane foam with a density of at least 2 lb./cu. ft.

No regulation is going to suspend the laws of chemistry and physics
however. Urethane can absorb water up to 7% of its weight. Once it
gets inside those cells it does not circulate and eventually runs out of
oxygen.

There is some validity to the argument that aluminum is better than
stainless for diesel tanks. Stainless requires that the chromium oxide
surface be constantly renewed while, though it sounds counter intuitive,
with aluminum the surface corrosion itself inhibits further corrosion.

Bryan B wrote:
Hi Glenn,

Thats what I have read also but the other two tanks are foamed in. The boat
was built by the Bruckamn yard of C&C, which was the custom yard. I thought
maybe there was a foam that was breathable and used for this application.

Confused in Ohio.

Bryan

"Glenn Ashmore" wrote in message
news:mczjb.78272$sp2.67348@lakeread04...

Now THAT is one thing I can definitely quote chapter and verse because
everything I have ever seen says DO NOT use foam around a metal tank.
Especially a stainless one. It will hold oxygen depleted stagnant water
against the metal and create ideal conditions for crevasse corrosion.

Stainless needs a constant supply of oxygen be it in air or desolved in
seawater to maintain the protective surface. Tanks should be mounted so
that air can get to all surfaces. A lot of small Neoprene pads is
better than having the tank rest on a large surface that impeeds
circulation.

While I do not agree with David Pascoe on some things he has a good
section on mounting metal tanks on his survey page.

Bryan B wrote:


I need to re-install a diesel tank. It was foamed in place and an then

tab

glassed to the top of the bulkhead and hull. No problem with the glass

work

but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com





--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I have done work similar to this. If you get the low expansion insulation
foam (urethane) in a can and start from the deepest part of the cavities,
working your way outward slowly in slow sweeping motions, allowing the
previous passes to max out their expansion, you should be okay. Do a sample
cavity that you rig yourself to get a feel for it, then move quickly to your
installation and go. The application tube from the can plugs up quickly, so
be organized and move it along. If you use the high expansion foam, you can
pressurized the area risking breeches, crushing, bursting, in the adjacent
surfaces. Get some more input than what I am saying to round out your
research.
Leo
"Bryan B" wrote in message
...
I need to re-install a diesel tank. It was foamed in place and an then
tab
glassed to the top of the bulkhead and hull. No problem with the glass
work
but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan

Hmm, OK.

One thought that is re assuring..... Aluminum and steel boat interiors are
insulated with a poly urethane foam.

The tank I need to return to service has been out of the boat for a few
years. It looks good but I will pressure test before re-installing. The
other 30 year old tanks do not leak, hence the consideration for going back
to foam support.

I am happy to report all tanks have clean outs and can be removed from the
boat without major cabinet destruction. If they do ever start leaking I
guess I would go with with aluminum replacements.

Thanks all.

"Leo Petipas" wrote in message
ble.rogers.com...
I have done work similar to this. If you get the low expansion insulation
foam (urethane) in a can and start from the deepest part of the cavities,
working your way outward slowly in slow sweeping motions, allowing the
previous passes to max out their expansion, you should be okay. Do a
sample
cavity that you rig yourself to get a feel for it, then move quickly to
your
installation and go. The application tube from the can plugs up quickly,
so
be organized and move it along. If you use the high expansion foam, you
can
pressurized the area risking breeches, crushing, bursting, in the adjacent
surfaces. Get some more input than what I am saying to round out your
research.
Leo
"Bryan B" wrote in message
...
I need to re-install a diesel tank. It was foamed in place and an then
tab
glassed to the top of the bulkhead and hull. No problem with the glass
work
but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan

I too have read Mr. Pascoe's tank installation info. as well as almost
monthly ranting from Powerboat Reports editorial and boat review staff
against foamed tanks. All the negatives do make sense. So I did a half
foaming job on my aluminum tanks. I dammed off the (4) corners and just
foamed them using poured (2) part foam and then I ran a damn around the top
an inch or two deep and used insulation foam (one part) all around the top.
The corners were to keep the tanks from moving and the sealing around the
top was to fend off any water that might find its way into the tank
compartments. So what I tryed to do was not trap water anywhere around the
tank. This made some sense to me at the time but weather it makes sense to
anyone else, well that's up for question. I hope you do something that gives
you peace.

--
Ron White
My boatbuilding website is:
www.concentric.net/~knotreel

Ever hear of poultice corrosion? It's another reason why aluminum isn't
necessarily better than mild steel.

Glenn Ashmore wrote:

A lot of production builders foam in their tanks. It is less expensive
and quieter. One thing about regulations. If you don't like one you
can probably find another that says something different. And if you
can't find one you can lobby your congressman to create one more to your
liking. :-) In this case 33 CFR 183.516(c) says you can use
polyurethane foam with a density of at least 2 lb./cu. ft.

No regulation is going to suspend the laws of chemistry and physics
however. Urethane can absorb water up to 7% of its weight. Once it
gets inside those cells it does not circulate and eventually runs out of
oxygen.

There is some validity to the argument that aluminum is better than
stainless for diesel tanks. Stainless requires that the chromium oxide
surface be constantly renewed while, though it sounds counter intuitive,
with aluminum the surface corrosion itself inhibits further corrosion.

Bryan B wrote:

Hi Glenn,

Thats what I have read also but the other two tanks are foamed in.
The boat
was built by the Bruckamn yard of C&C, which was the custom yard. I
thought
maybe there was a foam that was breathable and used for this application.

Confused in Ohio.

Bryan

"Glenn Ashmore" wrote in message
news:mczjb.78272$sp2.67348@lakeread04...

Now THAT is one thing I can definitely quote chapter and verse because
everything I have ever seen says DO NOT use foam around a metal tank.
Especially a stainless one. It will hold oxygen depleted stagnant water
against the metal and create ideal conditions for crevasse corrosion.

Stainless needs a constant supply of oxygen be it in air or desolved in
seawater to maintain the protective surface. Tanks should be mounted so
that air can get to all surfaces. A lot of small Neoprene pads is
better than having the tank rest on a large surface that impeeds
circulation.

While I do not agree with David Pascoe on some things he has a good
section on mounting metal tanks on his survey page.

Bryan B wrote:


I need to re-install a diesel tank. It was foamed in place and an then


tab

glassed to the top of the bulkhead and hull. No problem with the glass


work

but what foam should be used for the tank. The tank is 316 ss about 30
gallons.

Thanks,

Bryan



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com