Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc. The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
Steve

"Wayne.B" wrote in message
...
If everything goes according to plan, I'm about to buy a Grand Banks
49 trawler that needs new fuel tanks (500 gallons each).

Any thoughts from this group on the best material for new tanks,
fabrication hints, and/or removal/installation suggestions?

On Sat, 5 Jun 2004 07:08:12 +0200, "Steve Lusardi"
wrote:
Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc. The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
=============================

Steve, a couple of questions:

1. Dou you use the Permatex both inside and out? Manufacturer?

2. I've always heard that SS tanks for diesel were a problem because
of weld corrosion. Is that not a problem with 316TI?

I was told 5052 aluminum is better than any stainless, and that stainless
tends to stress crack. I am sure there are many perfectly good stainless and
aluminum tanks out there. I would not even think about mild steel, it will
eventually start to rust.

"Wayne.B" wrote in message
...
On Sat, 5 Jun 2004 07:08:12 +0200, "Steve Lusardi"
wrote:
Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc.
The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
=============================

Steve, a couple of questions:

1. Dou you use the Permatex both inside and out? Manufacturer?

2. I've always heard that SS tanks for diesel were a problem because
of weld corrosion. Is that not a problem with 316TI?

5052 is a marine grade aluminum, but aluminum of any type is very reactive
when exposed and unprotected. I suggest that these tanks, once installed
will not offer access to all surfaces impeding inspection and maintenance.
In that light, I would not use it. 316TI is the chemical industry's material
of choice for corrosive environments. It is correct that SS will corrode
(crevise corrosion), but that takes stagnant water without oxygen and that
case will not exist is this application. If all welds are properly
passivated, inside and out, then there should be no corrosion. However by
far, the majority of diesel tanks are made very successfully of mild steel.
The success of mild steel is significantly enhanced when the INSIDE of the
tank is coated with this permatex product. This paint was developed for the
USAF for their underground jet fuel storage tanks. It is sold by the kilo
and has a 30 day shelf life. This has a very high lead content and is
hazardous to apply. Proper breathing gear is a must. It is sold to
professionals only. Another solution for these tanks would be polypropylene.
It can be welded, so custom fabrications are very possible and static
electricity and corrosion are not a problem. I believe all Chrysler vehicles
now use this. As a cost, I would estimate $3000 to $4000 per tank would be
close. Just as a side item, I use mild steel for diesel and 316TI for
drinking water.
Steve

"habbi" wrote in message
...
I was told 5052 aluminum is better than any stainless, and that stainless
tends to stress crack. I am sure there are many perfectly good stainless
and
aluminum tanks out there. I would not even think about mild steel, it will
eventually start to rust.

"Wayne.B" wrote in message
...
On Sat, 5 Jun 2004 07:08:12 +0200, "Steve Lusardi"
wrote:
Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc.
The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
=============================

Steve, a couple of questions:

1. Dou you use the Permatex both inside and out? Manufacturer?

2. I've always heard that SS tanks for diesel were a problem because
of weld corrosion. Is that not a problem with 316TI?

On Sat, 5 Jun 2004 19:47:57 +0200, "Steve Lusardi"
wrote:
As a cost, I would estimate $3000 to $4000 per tank would be
close.

Thanks for the information, estimates are close to what I've received.

The realy BIG costs are removal and re-installation - holes to be cut,
reglassed, painted, etc.

What do you use for fittings, and do you take special precautions to
isolate dis-similar metals?

Wayne,
You must consider maintenance, so an access hatch will be needed for each
baffelled compartment. I use studs, nuts and make-a-gasket RTV for the seal.
The boat layout will determine where the inlet and outlet ports should be.
Here, I suggest flanges, studs and gaskets or RTV. When all assembled, test
at 2 psi for 24 hours. I take special care with dissimliar metals and if I
have to use them, I use nylon isolators and tophats around the bolts and
studs. Always check with a VOM to be sure. However, do not use these with
the fuel tank. (static). Dissimiliar metals only matter when wet. No water,
no ploblem. I would be concerned about chafe between the hull and the tank.
Either eliminate the problem by bolting hard to the hull or use rubber shock
mounts and use a bond cable across a mount for earth.
Steve

"Wayne.B" wrote in message
...
On Sat, 5 Jun 2004 19:47:57 +0200, "Steve Lusardi"
wrote:
As a cost, I would estimate $3000 to $4000 per tank would be
close.

Thanks for the information, estimates are close to what I've received.

The realy BIG costs are removal and re-installation - holes to be cut,
reglassed, painted, etc.

What do you use for fittings, and do you take special precautions to
isolate dis-similar metals?

On Sunday 06 June 2004 11:51 am in rec.boats.building Steve Lusardi wrote:

Wayne,
You must consider maintenance, so an access hatch will be needed for each
baffelled compartment. I use studs, nuts and make-a-gasket RTV for the
seal. The boat layout will determine where the inlet and outlet ports
should be. Here, I suggest flanges, studs and gaskets or RTV. When all
assembled, test at 2 psi for 24 hours. I take special care with dissimliar
metals and if I have to use them, I use nylon isolators and tophats around
the bolts and studs. Always check with a VOM to be sure. However, do not
use these with the fuel tank. (static). Dissimiliar metals only matter
when wet. No water, no ploblem. I would be concerned about chafe between
the hull and the tank. Either eliminate the problem by bolting hard to the
hull or use rubber shock mounts and use a bond cable across a mount for
earth. Steve

All good stuff, but one additional point :=
Each tank should have a bottom drain at the lowest point. Water
contamination is a common problem for most fuels, especially diesel.
Water will always settle to the bottom of the tank, it is a good idea
to wait overnight after refueling to allow any water to separate and
then drain the tank bottom until clean fuel comes out.
It is also good practice to also do this as a regular routine inspection
to prevent the buildup of condensation or inward leakage from vents and
fillers.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

"Steve Lusardi" wrote in message
...
Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc.
The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
Steve

Commercial small / medium size vessel practice is usually aluminum or mild
steel. I don't see using plastic tanks, the size you are suggesting is
pretty big for plastic of non cylindrical shapes.

Saying aluminum is "too reactive" isn't really true. The only problem with
aluminum is if the tank is let to sit with moisture trapped against it.
Stand-offs or similar methods to keep any condensation from the skin of the
tank is a good idea.

Mild steel is generally not painted inside and the steel tanks do last at
least 20 years (the diesel on the inside tends to give a nice coating).
That said you can coat the inside of steel tanks for additional protection.

No I wouldn't use stainless steel - generally weld cracking can occur with
the thin plates of tanks. If you do go S.S., I would probably select 316L,
which is a low carbon version of 316 that is suited for welding. Much
better for corrosion than 304. But it's a pretty big price premium for
doubtful benefit.


--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)

Evan,
You are correct, but here is the rub. Diesel is hygroscopic and with tanks
this size water, being more dense than fuel oil, will settle at the bottom
and EAT the aluminum pretty damn quick.
Steve

"Evan Gatehouse" wrote in message
...

"Steve Lusardi" wrote in message
...
Wayne, you are talking about a reasonable effort and significant cost
regardless of the material chosen, Do not use aluminum, it is far too
reactive. Do not use gavanized steel. The diesel will disolve the zinc.
The
ultimate material should be 316TI SS and next best would be mild steel
blasted and painted with the special Permatex tank paint. This paint is
designed for large storage tanks and must be ordered specially. I just
finished 2 water tanks slightly smaller than yours in stainless and the
material cost was $3200 and that included access hatches.
Steve

Commercial small / medium size vessel practice is usually aluminum or mild
steel. I don't see using plastic tanks, the size you are suggesting is
pretty big for plastic of non cylindrical shapes.

Saying aluminum is "too reactive" isn't really true. The only problem
with
aluminum is if the tank is let to sit with moisture trapped against it.
Stand-offs or similar methods to keep any condensation from the skin of
the
tank is a good idea.

Mild steel is generally not painted inside and the steel tanks do last at
least 20 years (the diesel on the inside tends to give a nice coating).
That said you can coat the inside of steel tanks for additional
protection.

No I wouldn't use stainless steel - generally weld cracking can occur with
the thin plates of tanks. If you do go S.S., I would probably select
316L,
which is a low carbon version of 316 that is suited for welding. Much
better for corrosion than 304. But it's a pretty big price premium for
doubtful benefit.


--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)