Weight of tanks

I probably could figure this one out, but does anyone know which weighs more when full and on land: a steel 120 or an Al 80?

Scuba Cylinder Specifications

AL80 approx 37lbs (31lbs + 6lbs air)
ST120 approx 47lbs (38lbs + 9lbs air)

Now correct me if I'm wrong....

The ST120 will be about 6 lbs less buoyant near empty than the AL80 so you will be able to drop about 6lbs of your weights.

This means your total net weight change is +4lbs for a 50% increase in breathable air on your back.

Kyphur, Yes. those calculations are correct. Being an old guy I am deciding on whether to retire my steel 120 and go with Al 80. Seems the 120 is heavier to deal with topside, which is my big concern. I know I'll lose some bottom time with the Al 80.

TMHeimer:

Kyphur, Yes. those calculations are correct. Being an old guy I am deciding on whether to retire my steel 120 and go with Al 80. Seems the 120 is heavier to deal with topside, which is my big concern. I know I'll lose some bottom time with the Al 80.

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I wish you were closer (and not on the other side of an international border), I'm looking for another st120!

TMHeimer:

Kyphur, Yes. those calculations are correct. Being an old guy I am deciding on whether to retire my steel 120 and go with Al 80. Seems the 120 is heavier to deal with topside, which is my big concern. I know I'll lose some bottom time with the Al 80.

Click to expand...

Go HP 80 and cash in all around!

Pete

yup, I can attest to the truth in that, my friend's steel 80s are feather weight compared to any other tank. you should hear him complain when he picks up my 3AA faber HP100s (probably 14 lbs heavier in dry weight than his)

The HP 120 is very tall and unless you are 6'+ it may not work well for you in terms of trim.

You'll find a similar or better volume to total weight ratios and weight savings with other steel tanks:

X7-100 = 33 lbs but -2.5 pounds buoyant when empty, so you save 6.9 lbs in lead weight for 4.9 pounds in net weight savings over an AL80 but with 23 cu ft more gas.

X8-119 = 42 lbs but -2.0 pounds buoyant when empty, so you save 6.4 lbs in lead weight. Consequently for only 2.6 pounds more net weight than an AL80 you have 46 cu ft more gas.

X8-130 = 43 lbs but -2.0 pounds buoyant when empty, so you save 6.4 lbs in lead weight. Consequently for only 3.6 pounds more net weight than an AL 80 you have 54.4 cu ft more gas.

X7-80 = 28 lbs but -3.0 pounds buoyant when empty, so you save 7.4 lbs in lead weight in addition to 3 pounds in tank weight for a net weight savings of 10.7 pounds over an AL80 but with 4 cu ft more gas. The downside is the X7-80 is only 19.7" tall so it works great for short women, kids, ets where the weight saving is greatly appreciated, but it is not so hot for divers of normal height.

Faber steel FX series high pressure 80 tank weighs 28-lbs (not including valve) empty + 6lbs of air = 34-lbs. However it has empty buoyancy of -1.74lbs. A heck of a lot better than aluminum 80.

Faber steel M series high pressure 80 tank weighs 32.3lbs empty (not including valve) + 6lbs of air = 38.3lbs. However, its buoyancy when empty is -6.58lbs. You can shed a bunch of dive weights by using this tank over an aluminum 80, not to mention the total dive dead weight package should be a few pounds less because of the lighter tank.