Its so easy to put in access ports in an aluminum tank. Cut a square
hole, get 2"wide aluminum strips the same gage as the tank walls and
install as a sister flange using bolts as attachment studs, epoxy coat
the sister flange to the tank and then simply line everything, the
original cut out square used as the closure manhole/handhole. The
typical 100 gallon square tank in most boats are such that a human arm
can reach entirely across to the other side from an access port.
Honestly did you ever see a LARGE access port on a rotomolded tank that
didnt cost almost as much as the tank without an access port?

Without access ports there is NO way to get inside and mechanically
scrub off any biofilm (calcyx) ... and if there there is any calcyx
remaining, simple sanitization methods simply will not work. Access
port ARE simpler easier and cheaper to install /add to an aluminum
tank.

Mmmmmmmm most ballfes in fabricated metal tanks inthe marine industry
typically only have 5%-10% of the projected cross section open to
prevent 'sloshing' . A rotomolded tank would probably consist of
mostly deep Vs to accomplish the same. A rotomolded tank with the
typical baffle area and baffle 'exit' area form by deep Vs would be
absolutely preposterous while having little useful internal volume in
comparison. Sorry.

:-)

problem is on a normal baffeled tank of any size (under the size a man
can crawl thru the baffles) is painting it with a brush or roller is
next to impossiable, unless the tank has an inspection/work port in
every space between baffles. It's a great way to go if your building
tanks but expensive to do right. And roto mold tanks can and do have
baffles. They are made by molding deep V's into the sides of the
tanks.

Joe

On Oct 2, 12:40 pm, druid wrote:
Hi,

I've always seen plastic watertanks, but the boat I'm buying has an old
aluminum one (I think it's alum: it's metal, and not SS). Is there any
advantage to alum over plastic or vice-versa?

Hi

I worked in a university research oyster hatchery as a bio lab aid. I
was the summer help. But the people who worked there were all PhD
types. I scrubbed glass wear. One of the things the lab did was test
hatchery materials and water supply materials for toxicity. We used
oyster larvae for the indicator in the bio assays. Basically,
fertilize the gametes in water with a test material. Observe the
development over time. Different materials kill/deform baby oysters at
different rates.

What I learned in two summers. Oysters are very sensitive creatures.
Just about anything will kill em. A material must be really inert
(safe) for an oyster to like it. For example, 316 L. Copper, on the
other hand, is death to an oyster. Do a little research regarding
effects of Aluminum on our brain. So goes with many plastics.

Ya Ya Ya yada yada yada in know now all the republicans o, and our one
libertarian will pipe in and say you'd have to eat a pound a day for
50 years to have any deleterious effect. So go for it.................

I had two 1979 Al tanks on my boat when I bought it. After yanking
both out and tearing one open I found pitting every where. Looked like
the pox. I eye estimate that 30-40% of all inside tank surfaces were
pitted and 100% surface was rough. Then I wondered where all that
material went????????????

Now I have two tanks on board. One 40 gallon and one 20 gallon. Both
are made of 316 L.

Forget plastic and forget Al...................
Some things ya just cant filter out using charcoal and paper.

Besides, its a boat. Why even conseder anything but the best.

Live long and prosper,
Bob

In article . com,
says...
On Oct 2, 12:40 pm, druid wrote:
Hi,

I've always seen plastic watertanks, but the boat I'm buying has an old
aluminum one (I think it's alum: it's metal, and not SS). Is there any
advantage to alum over plastic or vice-versa?

Hi

I worked in a university research oyster hatchery as a bio lab aid. I
was the summer help. But the people who worked there were all PhD
types. I scrubbed glass wear. One of the things the lab did was test
hatchery materials and water supply materials for toxicity. We used
oyster larvae for the indicator in the bio assays. Basically,
fertilize the gametes in water with a test material. Observe the
development over time. Different materials kill/deform baby oysters at
different rates.

What I learned in two summers. Oysters are very sensitive creatures.
Just about anything will kill em. A material must be really inert
(safe) for an oyster to like it. For example, 316 L. Copper, on the
other hand, is death to an oyster. Do a little research regarding
effects of Aluminum on our brain. So goes with many plastics.

That seems to be an apples and oranges comparison to me. Do you
have specific data on plastics? I drink a few liters of soda a
week from plastic bottles---and I can still type this with two
hands at age 61.

Ya Ya Ya yada yada yada in know now all the republicans o, and our one
libertarian will pipe in and say you'd have to eat a pound a day for
50 years to have any deleterious effect. So go for it.................

I had two 1979 Al tanks on my boat when I bought it. After yanking
both out and tearing one open I found pitting every where. Looked like
the pox. I eye estimate that 30-40% of all inside tank surfaces were
pitted and 100% surface was rough. Then I wondered where all that
material went????????????

"all that material" might have been two to three grams of aluminum in a
few thousand kilograms of water. Since the aluminum content of the
water put into the tank was probably 1 to 8PPM, that doesn't
sound like a problem unless you left the original 100 gallons
of water in the tank for 10 to 15 years.

Now I have two tanks on board. One 40 gallon and one 20 gallon. Both
are made of 316 L.

Forget plastic and forget Al...................
Some things ya just cant filter out using charcoal and paper.

Besides, its a boat. Why even conseder anything but the best.

Um, weight and cost probably lead the list. If your boating
budget is unlimited, you've got more money than me.

Worrying about aluminum tanks in a boat where you fill the
tank from a city water supply that uses aluminum sulfate
as a coagulant seems a waste of time to me.

Live long and prosper,
Bob


Mark Borgerson

Bob wrote:

ther hand, is death to an oyster. Do a little research regarding
:effects of Aluminum on our brain. So goes with many plastics.

Showing there aren't any?

On Oct 9, 10:18 am, David Scheidt wrote:
Bob wrote:

ther hand, is death to an oyster. Do a little research regarding
:effects of Aluminum on our brain. So goes with many plastics.

Showing there aren't any?



Howday......

Without reviewing the salient body of literature regarding effects of
Al on humans I'll just say: I believe Aluminum in humans is bad.... Any
amount.

So I don't use Al cookware or Al forks and spoons ya find when third
worlding it. Also, potable water tanks. Ya know its kinda like using
Al stranded wire in your AC and DC boat system. Now why would you NOT
want Al wire, ANY amount, on your boat??????

But like I said b4 lots will say at 8 ppm it aint no problemo. Good on
mate for your tuff life style. Sorry, I wont drink an 8 ppm solution
of cyanide either.

Best o luck. Go with 316L for any size boat. Im not rich, in fact I
take home $2000/mo and my boat gets the best. Now why would I do that?

Bob

Bob wrote:
:On Oct 9, 10:18 am, David Scheidt wrote:
: Bob wrote:
:
: ther hand, is death to an oyster. Do a little research regarding
: :effects of Aluminum on our brain. So goes with many plastics.
:
: Showing there aren't any?



:Howday......

:Without reviewing the salient body of literature regarding effects of
:Al on humans I'll just say: I believe Aluminum in humans is bad.... Any
:amount.

You're welcome to believe anything you'd like. Reality will get along
just fine without you.

On Thu, 11 Oct 2007 00:27:49 +0000 (UTC), David Scheidt
wrote:

Bob wrote:
:On Oct 9, 10:18 am, David Scheidt wrote:
: Bob wrote:
:
: ther hand, is death to an oyster. Do a little research regarding
: :effects of Aluminum on our brain. So goes with many plastics.
:
: Showing there aren't any?



:Howday......

:Without reviewing the salient body of literature regarding effects of
:Al on humans I'll just say: I believe Aluminum in humans is bad.... Any
:amount.

You're welcome to believe anything you'd like. Reality will get along
just fine without you.

Interesting as most of the 3rd world cooks using aluminum pots and
alzimers (which was one of the most common ailments attributed to
aluminum) doesn't seem to be a major problem.


Bruce in Bangkok
(brucepaigeATgmailDOTcom)