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clavicl3
10-05-2009, 15:27
I'm considering buying a tank. Would the weight be lower with an aluminum tank or steel tank? I've seen that steel tanks are much smaller. How much air do they hold relative to an Al tank?

Damselfish
10-05-2009, 15:47
that's all going to depend on the tank. Here's a chart - Scuba Cylinder Specifications (http://www.tdl.divebiz.net/pub/tanks.html)

Lighter on land is nice, but there are lots of other considerations. Aluminum will be cheaper. Steel tends to have better buoyancy characteristics in the water, especially if you are diving cold water. (On the other hand, some people who dive warm water with little exposure protection will find themselves overweighted with some steel tanks.)

clavicl3
10-05-2009, 16:03
It looks like steel tanks are slightly lighter than Al tanks. And smaller is good as well. Negatively buoyant is good for me since it allows me to wear less weight in other areas.
Now... what is Tripple, Pwdr, Galv?
What is better?

WD8CDH
10-05-2009, 16:09
Once weighted for the same buoyancy, the tank plus any weight will always be less for the higher pressure tank of the same material. Of the readily available SCUBA tanks, HP Steel will be the lightest for a given capacity, both the tank itself and with any needed weight to be added or removed from your belt.

CompuDude
10-05-2009, 16:47
It looks like steel tanks are slightly lighter than Al tanks. And smaller is good as well. Negatively buoyant is good for me since it allows me to wear less weight in other areas.
Now... what is Tripple, Pwdr, Galv?
What is better?

Galvanized in best for salt water, and fine in fresh, too. The triple-coated epoxy that Faber uses is fine for fresh water, but I don't like it as much for salt water. It also gets more beat-up looking than galvanized tanks do.

Power-coating is generally only for aluminum tanks.

WD8CDH
10-07-2009, 07:13
To make the decision MORE complicated, the phosphate interior treatment of the Faber tanks is more resistant to corrosion from a wet fill.

WD8CDH
10-07-2009, 07:19
This is the lightest diving system available. It is now DOT approved.

http://www.interspiro.com/_downloads/98607C01_Divator_Lite_product_leaflet_L.pdf

WaScubaDude
10-07-2009, 10:52
This is the lightest diving system available. It is now DOT approved.

http://www.interspiro.com/_downloads/98607C01_Divator_Lite_product_leaflet_L.pdf
These look great but what about the buoyancy characteristics? Any idea how much?

awap
10-07-2009, 13:32
It looks like steel tanks are slightly lighter than Al tanks. And smaller is good as well. Negatively buoyant is good for me since it allows me to wear less weight in other areas.
Now... what is Tripple, Pwdr, Galv?
What is better?

The only better solution is what my wife came up with. If it is a longer walk, I get to carry her tank.

mitsuguy
10-07-2009, 21:20
This is the lightest diving system available. It is now DOT approved.

http://www.interspiro.com/_downloads/98607C01_Divator_Lite_product_leaflet_L.pdf
These look great but what about the buoyancy characteristics? Any idea how much?


its a cool system, but they sell weights to make the assembly less positive, neutral, or negative...

out of the water, the tanks will be much lighter than standard gear, however, the weight you need to add will be similar to an aluminum tank to stay neutral in the water... this is both good and bad - it doesn't solve the root problem, walking with gear on is heavy, but it does make moving the tank around by itself easier...

WD8CDH
10-12-2009, 11:02
This is the lightest diving system available. It is now DOT approved.

http://www.interspiro.com/_downloads/98607C01_Divator_Lite_product_leaflet_L.pdf
These look great but what about the buoyancy characteristics? Any idea how much?


its a cool system, but they sell weights to make the assembly less positive, neutral, or negative...

out of the water, the tanks will be much lighter than standard gear, however, the weight you need to add will be similar to an aluminum tank to stay neutral in the water... this is both good and bad - it doesn't solve the root problem, walking with gear on is heavy, but it does make moving the tank around by itself easier...
Not quite true, when you add the weight they will still be much lighter than aluminum tanks, they are still lighter than even HP steel tanks of the same capacity.

mitsuguy
10-12-2009, 16:40
This is the lightest diving system available. It is now DOT approved.

http://www.interspiro.com/_downloads/98607C01_Divator_Lite_product_leaflet_L.pdf
These look great but what about the buoyancy characteristics? Any idea how much?


its a cool system, but they sell weights to make the assembly less positive, neutral, or negative...

out of the water, the tanks will be much lighter than standard gear, however, the weight you need to add will be similar to an aluminum tank to stay neutral in the water... this is both good and bad - it doesn't solve the root problem, walking with gear on is heavy, but it does make moving the tank around by itself easier...
Not quite true, when you add the weight they will still be much lighter than aluminum tanks, they are still lighter than even HP steel tanks of the same capacity.

Lets see if we can do some math and stop guesstimating...

their 6.7 liter setup, even at 300 bar, is only 71 cu ft.

if I am reading this correctly, an empty tank setup weighs 27 lbs, and a full tank setup weighs 37.7 lbs... which is confusing, because 10 lbs should be around 133 cubic feet... so, if we were to assume that 6.7 liters doubled up, you would get roughly 130 cubic feet of air, then we are doing pretty good, assuming you could find someone to fill it to 300 bar to start...

You could get a PST 130 cu ft steel cylinder (I can't compare it to aluminum, as the biggest AL cylinder I see is 100 cu ft), which weighs only 43 lbs and never goes positive no matter how empty you get it...

I'd just like to know the actual buoyancy characteristics of those tanks, and being as how I don't see them published, its hard to say for sure