AL40 vs Steel 50 for deco gas?

[PSD Diver99]

Just wondering if anyone is using Steel 50 for deco gas instead of the usual AL40? Thoughts?

 

[Divin'Papaw]

A full steel 50 is -5 or 6 lbs negative where as full AL40, especially Luxfer, is -0.8 lbs. If you are dropping the bottle at a cave entrance or at the tie-in location on a wreck, MAYBE the steel 50 would work. But I sure wouldn't want to be swimming around with one slung to my side.

 

[JonG1]

I've made normoxic 60-70m ow wreck dives with SM bottom mix and deco mix with 12l steels, but obviously you are balanced in that configuration, any other deco cylinders are then aluminium.

I guess it depends on how you rig it and rest of configuration, back in the day it was perfectly normal to use steel stages.

 

[Cio]

I use a steel 46. No issues and I hate how 40s get floaty so like how it sits the same full to empty.

 

[Grantt]

In theory, stage/deco tanks should be AL to reduce excess weight. I'm sure there are exceptions to this rule but it is a generally accepted practice.
If steel tanks work better for your configuration and requirements, then go for it.

 

[PEDiver]

Why? With steel stages/deco bottles, you are most likely overweighting yourself and if you’re only slinging one bottle, you’ll have a lot of weight on one side. If you need more deco gas, sling an 80. It was not uncommon in the past to have steel tanks used for O2 or another deco gas when cave diving since you usually stash the bottle at the entrance and don’t carry it for any real distance. But I can’t see any upside to using steel tanks for stages/deco if you’re going to be swimming with them for the duration of the dive.

 

[rx7diver]

We were using OMS (Faber) LP46's (same OD as, but a bit shorter than, Faber LP50's) for deco gas in the mid- to late 1990's in the Great Lakes. Drysuit dives. For IANTD Advanced Deep Air training, we would sling two, one on each side, right rich and left lean. The "lean" cylinder was cave-pumped. The "rich" cylinder was NOT cave-pumped (especially if it contained 100% oxygen!).

We were doing air dives a bit deeper than 200 fsw.

At first I wore manifolded Sherwood Genesis (PST) HP 100's. Eventually I wore HP 120's. I used a DR original Al plate and wings and simple harness.

Worked fine for these dives. (Don't wear both steel deco bottles on one side if you want an effortless configuration, though!)

rx7diver

 

[happy-diver]

We wore a Faber 40, 5litre steel clipped horizontally across our stomachs, a while back

More recently just me a 25, 3 litre steel on my back

If it's a steel, you can pump it!

 

[Cio]

Why? With steel stages/deco bottles, you are most likely overweighting yourself and if you’re only slinging one bottle, you’ll have a lot of weight on one side. If you need more deco gas, sling an 80. It was not uncommon in the past to have steel tanks used for O2 or another deco gas when cave diving since you usually stash the bottle at the entrance and don’t carry it for any real distance. But I can’t see any upside to using steel tanks for stages/deco if you’re going to be swimming with them for the duration of the dive.

Difference between an 80 and a 46 (or 50) is substantial, especially if you're going into a wreck. A 46 is virtually the same as a 40 but gives way more deco gas.

A 40 is really a 32 or 33 for planning purposes, a 46 (properly filled) is a 46 and the safety factor is higher.
I still need 4# of lead with a 46 so not overweighed. I can see how this won't work for everyone but dry suit wreck diving where SAC rates aren't always the best, it makes longer dive plans possible while still maintaining proper gas planning rules.

 

[ChrisMBC]

If I'm reading the infamous @tmassey cylinder spec sheet correctly, a Catalina AL40 is -1.5lbs negative when full, +1.4lbs empty. A Faber LP50 is -2.4lbs full (presumably more like -3lbs if hot-filled) and +1.2 empty. Not a huge difference?