Steel or Ali?

[GottaDive]

Have both, dive both. Like others have said, it depends on the type of dive your on.

However,..I do prefer one that is FULL OF GAS!!

~Steve~

 

[jeckyll]

You still carry the weight, just not on your belt/in your BC. It is on your back.

Lets take a steel tank that is neutral when empty (say a PST LP 80).

This means that when in the water at the end of a dive, you have something on your back that requires _no_ lead to keep down.

Compared to an AL80 which requires you to have 4 lbs of lead on your belt (or wherever you like to carry it).

Your BC, exposure protection etc has unchanged buoyancy characteristics. Therefore the only change is the 4 lbs you now do now have to carry at the end of the dive to stay neutrally buoyant (if you were to breath your tank to zero psi).

PST LP 80 weighs 34 lbs
Luxfer AL 80 weighs 31 lbs

So you'd save one pound.

Now if you had a Faber HP 80 (again still the same amount of gas inside) which is -7 lbs at the end of the dive and weighs 32.5 lbs, you could take off over 8 lbs from your belt.

HTH

Bjorn

P.S.: Tank weighs from http://www.techdivinglimited.com/pub/tanks.html in case you want to run through some more examples with different kind of steel or AL tanks.

<edit>: I personally would choose a neutrally buoyant tank like a LP 95 or a E7 120

 

[spectrum]

It would seem to me that ensuring correct weighting for the END of the dive would solve this problem in most circumstances.

You can even solve the trim problem by putting weight on the tank straps or your backplate. It shouldn't matter that this weight is non-ditchable because it is as ditchable as the steel tank is.

Or I could just be wrong. Which is definately possible.

Weighting should aways be configured for the end of dive condition, the BC carries you through the "heavy" part of the dive.

Your thoughts on weight are also correct. In fact adding weight is exactly what standard aluminum cylinder divers must do to make the common AL80 divavble. The point is that you are adding weight to sink a cylinder that is already heavy so it's like adding insult to injury. This can easiily add another 10% of a divers body weight and to some this maters, especially for cold water shore diving.

There is no magic to a neutral 80 BTW. The cylinder is made with excess material to in effect integrate enough weight to offset the buoyancy.

For the lightly weighted warm water diver, the stand up and jump boat diver or the hulk it is much less of an issue.

Pete

 

[CBulla]

Here is the thing that still puzzles me about this arguement:

All tanks weight less empty than full. You lose the weight of the air in the tank when the tank empties during a dive.

So, even if you are diving steel, which is still negatively buoyant when empty, your tank weighs less at the end of the dive. If you are not weighted for an empty tank, and you have an empty tank strapped to your back (along with buoyant exposure protection), you can still be positively buoyant at the end of the dive and struggle during deco/safety stops.

It would seem to me that ensuring correct weighting for the END of the dive would solve this problem in most circumstances.

You can even solve the trim problem by putting weight on the tank straps or your backplate. It shouldn't matter that this weight is non-ditchable because it is as ditchable as the steel tank is.

Or I could just be wrong. Which is definately possible.

I can definately see the volume advantage of steel for long dive plans, though...

I have found that by going to steel tanks, even a simple steel 72 at the end of a dive is more than adequate weight to provide negative bouyancy. That is in a 3/2 wetsuit which I absolutely hate to wear.

On the occaisions I do wear an AL now a days, I lace on 4# to my webbing and such is that, I've lost nothing really unless its not a neutral type tank then I just lace on 2 3# weights.

 

[m3830431]

I have both but perfer the steel 100's over the Al 80's. The less lead I need the better the dove.