steel vs alum

[limeyx]

My new Worthington 100s weigh 34 lbs. empty. I haven't been in the water yet with them (and won't until next summer, alas), but I figure that in terms of removing weight it will be a wash--taking 4 pounds off the belt, but adding 4 pounds to the tank (assuming that the average weight of an aluminum 80 is 30 lbs.) The real plus is the extra air--even if I only fill them to 3000 psi I'll be getting at least 10 percent more air than I would with aluminum 80s.

That's the out of water weight though. You need the in-water buoyancy numbers to see how much weight you can drop.

Going from an AL80 to a PST E7-100 I dropped 4 pounds initially, and then maybe another 2 after that.

The PST is close to neutral empty, compared to the AL80 at (usually) around +6

 

[nwfellah]

good to know. Thanks everyone. I might be looking into a steel in the near future.

 

[bob1dp]

I usually prefer to dive steel tanks.

 

[Leadking]

The metalurgists do not agree with the analogy. 6351 cylinders can crack from "SLC" sustained load cracking. It is not from the fill cylce.

 

[Rick Murchison]

I usually prefer to dive steel tanks.

HHhhaaarrrrr!
We've got about 300 of these on the bottom off the LA (Lower Alabama) coast if you're interested...
Rick

 

[Double_D]

That's the out of water weight though. You need the in-water buoyancy numbers to see how much weight you can drop.

Going from an AL80 to a PST E7-100 I dropped 4 pounds initially, and then maybe another 2 after that.

The PST is close to neutral empty, compared to the AL80 at (usually) around +6

And that's the bottom line. The weight is the same - it's how you wear it that matters. More ditchable weight means a higher chance of an uncontrolled buoyant ascent if you lose it, accidentally or intentionally. I'd much rather inflate than mess with weights - emergencies are another matter.

 

[spectrum]

And that's the bottom line. The weight is the same - it's how you wear it that matters. More ditchable weight means a higher chance of an uncontrolled buoyant ascent if you lose it, accidentally or intentionally. I'd much rather inflate than mess with weights - emergencies are another matter.

The weight is not the same. Any tank that goes positive represents a penalty not found in those that stay neutral or heavier.

The mass of many steels is less than that of an aluminum cylinder of the same CF capacity.

Mass (weight) and buoyancy are two distinctly different properties. Both go into the comparisson.

Ditchable is another discussion.

Pete

 

[Sea-Diver]

One nice thing about steel tanks is that they have a longer life span.

 

[Shadow]

One nice thing about steel tanks is that they have a longer life span.

Not if they rust! Steel tanks require more care and more frequent visual inspections to ensure no rust - inside or out. If you get ANY moisture in your tanks, from a poor fill or diving your tank empty, and rust begins inside, your steel tank can be toast in just a few months. The high pressure air increases the rate of corrosion.

For scuba tanks, steel tanks cost about twice as much as aluminum. Interestingly, for propane tanks, aluminum tanks cost twice as much as steel... Hmm, can't be manufacturing costs driving the price...

I dive with steel tanks simply because I'm small, the tanks are smaller than same Cu.ft. aluminum, and I can use less lead weight. For an average size or bigger, stronger man, I don't know if the extra cost is justified.

 

[bergersau]

Here's a tank buoyancy calculator for those that need one.

http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi