Reasons for using aluminum tanks in cold water?

[mddolson]

I sold my steel tanks to reduce the weight. I've had a knee replacement.
I add 4 lbs to each cam band to account for the buoyancy change as the tanks empty.

 

[tbone1004]

I sold my steel tanks to reduce the weight. I've had a knee replacement.
I add 4 lbs to each cam band to account for the buoyancy change as the tanks empty.

that makes no sense.... You now have a 35lb tank that carries 77.4cf of air, if you used HP100's you would have a 35lb tank that carries 100cf of air and is shorter with 30% more gas.

 

[Razorista]

... 35lb tank that carries 100cf of air and is shorter with 30% more gas.

Doesn't that forget about the gas weight?
30% more gas is also 30% more weight.

I do not want to contradict the general message, though.
You can always find steel tanks that weight a bit less on land than aluminums of equal volume.

And adding weight to the aluminum tanks defeats the purpose, in my opinion.

 

[mddolson]

To clarify, I sold my set of twin 98 LP (fabre) steels which was 100lbs on my back & knee (with backplate/manifold/2 regs) when I switched to side mount. I can now manage the tanks as singles, & hand off/carry one tank at a time.
The 4 lbs on each cam band, came off my weight belt. BTW.
Compensating for light bottoms on aluminums at 500 psi.

 

[mddolson]

Doesn't that forget about the gas weight?
30% more gas is also 30% more weight.

I do not want to contradict the general message, though.
You can always find steel tanks that weight a bit less on land than aluminums of equal volume.
And adding weight to the aluminum tanks defeats the purpose, in my opinion.

True, but this assumes one has the budget to procure said tanks.
I already have 4x 80cuft aluminum tanks & I could no longer manage the twin 98's, on my back.
I could have split the steel tanks, into singles, but chose to sell them to fund my backmount rig (Nomad).
When traveling, rental tanks are usually 3000 psi aluminum's so it made sense to me be comfortable in that configuration.

 

[tbone1004]

OMS 98's aren't actually any significant weight savings btw. 4lbs/tank when empty, you aren't going to notice that. Even cave filled, the full 98's are only 8lbs heavier than the al80's, which isn't that bad when carried as singles.

Razorista, 30% more gas amounts to less than 2.5lbs. Inconsequential in this discussion. If you chose to say that I went with AL80's with lead on them because that's what I get when I travel, and already had them, then that's a different discussion, but saying he did it to reduce the weight without specifying the tanks he was going away from is not accurate because it doesn't actually reduce the weight by any significant amount with most tanks, and when compared to smaller tanks like the HP100's, is just wrong.

 

[eelnoraa]

Al tanks are lighter to carry around for a given volume of gas.

Incorrect. The most common AL tank is AL80. It is at 32lb (+4 empty). A X100 is 33lb (-2lb empty). No matter how you look at it, volume/weight is a lost for AL tank.

I think the main reason for anyone to use AL tank in cold is 1)cost 2)rental tanks. Can't see any other advantages

 

[shoredivr]

Double post

 

[shoredivr]

Aluminums as deco tanks only for me in cold water.

In the summer the St Lawrence River, the Niagara River and the St Clair River get up into the sweltering 70-76F degrees, and I'll dive a wetsuit in the rivers. Then Aluminums make sense.

 

[drbill]

I dive "cold" water and sadly gave up on steel tanks. Every one of mine has failed at some point due to hot fills or wet fills on dive boats. I dive neutral buoyancy Al 80 tanks now. Both of mine are ca. the mid 1970s and still going strong. On the last VIP for one of them the shop owner said it looked almost brand new inside. Of course these neutral buoyancy tanks have similar characteristics to steel.