Aluminum vs Steel tanks

[d33ps1x]

The Catalina 80 is neutral when empty, and about -4.5 when full. The Faber LP 95 is +0.4 when empty, and -5.5 or so when full.

Using the "steel = drysuit" argument, why is the Faber an unbalanced rig, compared to the alternative?

Actually Boogie. Although I really don't want to be involved in this discussion any longer I would point out that a Catalina Standard 80 (77.4 cf volume @ 3000 psi) is actually -1.8 pounds full of air and +4.0 pounds empty. Almost a 5 pound difference:
http://www.catalinacylinders.com/scuba.html

A standard Luxfer 80 is -1.4 full and +4.4 empty which is a full 5 lb difference:
http://www.luxfercylinders.com/products/scuba/specifications/us_imperial.shtml

The only exception to the rule that I have heard is a steel 72 tank which is considered cool with a wetsuit.

Then again please do disregard the above as I apparently don't think but instead just blindly follow the rules my masters have set forth for me.

 

[Soggy]

The goal is to dive a balanced rig that can be swam up in the event of a wing failure. *Most* of the time, that means no steel doubles. You'll have to look at steel singles on a case-by-case basis.

DIR says no steel tanks and wetsuits. However, when you look at a case-by-case analysis, you'll find that frequently wetsuit divers are adding v-weights and other non-ditchable weight in order to compensate for aluminum tanks, thus, at the end of the day, are as negatively buoyant as someone wearing steel tanks. I think the real answer is that no deep diving should really be done in a thick wetsuit, period, unless you know for sure that you can swim the thing up.

Another solution, though not DIR is to add a redundant bladder, which I don't see a huge problem with, but the GUE people do.

 

[MXGratefulDiver]

Actually Boogie. Although I really don't want to be involved in this discussion any longer I would point out that a Catalina Standard 80 (77.4 cf volume @ 3000 psi) is actually -1.8 pounds full of air and +4.0 pounds empty. Almost a 5 pound difference:
http://www.catalinacylinders.com/scuba.html

A standard Luxfer 80 is -1.4 full and +4.4 empty which is a full 5 lb difference:
http://www.luxfercylinders.com/products/scuba/specifications/us_imperial.shtml

I take it Boogie's referring to the compact 80 ... which is an AL cylinder that dives almost exactly like a Faber LP95.

This is so ... I know because I own one of the former and three of the latter and dive them interchangeably ... the figures he provided earlier are accurate for that type of cylinder.

As an aside ... let's assume we're all here to exchange information and keep the personal comments to a minimum. It's cool to correct someone ... not so cool to insult them in the process.

Thanks ...

... Bob (Grateful Diver)

 

[d33ps1x]

I take it Boogie's referring to the compact 80 ... which is an AL cylinder that dives almost exactly like a Faber LP95.

Definately no nitpicking here. That was unclear in his post and I made the assumption that he was discussing the attributes of the far more popular and common S80 cylinder that you can find in pretty much any dive shop.

The somewhat rare C80 is not really apples to apples.

 

[jonnythan]

I think the real answer is that no deep diving should really be done in a thick wetsuit, period, unless you know for sure that you can swim the thing up.

Of course! That's "the answer" but it's independent of Al vs steel. You will have the exact same situations with Al tanks or steel tanks with thick wetsuits, the only difference is going to be the way the large amount of lead is distributed.

 

[Boogie711]

I gave you the bouyancy figures, which I still maintain are accurate, so I'm not sure why you would be confused.

In any event, perhaps you can shed some light for me on why diving the aluminum in that case would be DIR, but diving the Faber would not?

 

[jonnythan]

Boogie, your numbers have to be off a little bit. If a cylinder is neutral when empty and holds 80 cf, it has to be over 5 pounds negative when full.

 

[Boogie711]

Actually, I think it's 77 cu ft, but OK. I don't want to get into a debate here either - I'm merely interested in the rationale behind why people would consider one setup DIR and the other one not.

 

[jonnythan]

Actually, I think it's 77 cu ft, but OK. I don't want to get into a debate here either - I'm merely interested in the rationale behind why people would consider one setup DIR and the other one not.

Well, I think we both know the answer to this one..

 

[d33ps1x]

Actually, I think it's 77 cu ft, but OK. I don't want to get into a debate here either - I'm merely interested in the rationale behind why people would consider one setup DIR and the other one not.

There also is a big difference in buoancy characteristics between 77.4 cf @ 3000 PSI vs @ 3300 PSI

There really is no half way about it. If you want to make comparisons accuracy helps.