How does AluS080 11.1 ltr for deco/stage tanks sound?

[Arsham]

Searched a bit but couldn't find the exact answer in the existing topics, so here comes my question:

I have four 12 liter 232 bar steel tanks for my SM and Twinset dives, which I normally do in cold waters of Stockholm, Sweden. Now I'm looking to buy 1 or 2 aluminum tanks to use as stage / deco tanks. I wonder if aluminum S080 11.1 liter tanks can be a good choice for that, as if I buy two with extended valves, I may be able to use them as SM tanks for some non deco dives as well instead of my steel tanks. Is this a really bad idea? Will they be so bulky and huge that cannot be used as stage / deco tanks, specially when I do SM with my steel tanks as my bottom tanks?

 

[Alekseolsen]

Tjena!
Norwegian backmount diver here. I own two S080 and 1 7l stage, most of the buddies I dive with used S080's as stages as well.

You maybif course argue that you could do most dives with a (or a few) slightly smaller stages, but at least to me, the convenience of filling my S080 with 50% only every few deco dives outweighs the hassle of a slightly larger tank. It must be mentioned that I fill air and partial blends for stages at different locations, with the air filling one most convenient

 

[Marie13]

AL80s are very commonly used for stage/deco/CCR bailout.

If you’re diving cold water in a drysuit with thick undies, they may be less desirable for SM as you will need more lead than if you were diving steels SM. Plus I find having to deal with the floaty butt is annoying.

 

[dlao]

Deco stages yes, SM no.

They are standard deco tanks in tropical waters. On a typical deco dive day, we always fill one AL80 with 50% and do two one-hour deco dives. Typically you'll want steel tanks for back gas and alu tanks for deco stages.

SM is another thing. AL80 is horrible for SM due to its buoyancy. It starts with -1lb and quickly shifts to head-heavy positive buoyancy. And you'll need to add another 8lbs of lead weight to your belt as they are +4 lbs when empty.

 

[Marie13]

SM is another thing. AL80 is horrible for SM due to its buoyancy. It starts with -1lb and quickly shifts to head-heavy positive buoyancy. And you'll need to add another 8lbs of lead weight to your belt as they are +4 lbs when empty.

AL80s are heavily used for SM in Mexican caves. But a lot less lead is needed.

 

[dlao]

AL80s are heavily used for SM in Mexican caves. But a lot less lead is needed.

Yeah in the Red Sea where I used to dive they are also standard. But I don't see any point in diving them in cold water, especially for SM.

 

[Marie13]

Yeah in the Red Sea where I used to dive they are also standard. But I don't see any point in diving them in cold water, especially for SM.

SM/single tank for cold water? Nope.

 

[grantctobin]

Plus I find having to deal with the floaty butt is annoying.

That’s a skills or practice issue

 

[stretchthepenn]

I think your plan of swapping out AL80 tanks for non-deco dives is do-able, but it's not really practical.

I dive SM, usually in chilly water (quarries with 45F water at bottom) and I've been trained to use steel primary tanks and AL80s as deco stages. The AL80 tanks work fine for that purpose.

I also dive a Choptima (Dive Rite chest-mount O2ptima) rebreather, and I use SM-configured AL80 tanks for my diluent and bailout cylinders. The AL80s work well for that purpose, too.

I'm more hesitant about using AL80s as primary SM tanks for OC diving, though, especially in cold water. AL80s don't ride as evenly as steel tanks, you'll have to carry a lot more lead, and you'll also need to rethink your clip-in system.

About the clip-in system changes... The first change is that AL80s require you to hook the bottom clips in at your waist rather than on a butt plate. Depending on how you've been trained to carry your deco stages, you may need to swap out your clip-to-tank attachment point.

The second change is that as the AL80 tanks empty, their bottoms float. To fix this issue, you either move the bottom clips to other D-rings toward your midline, or you use sliding D-rings and move the entire clip-and-ring assemblies toward your midline. You'll likely need to add these items to your waist strap.

The third change is your hose configurations. When I dive steel primary tanks, I like my valve handles off to the side and the valve orifice pointing away from my chest. When I dive AL80 tanks with my rebreather, though, I find that I need to have the valve handles pointing downward and the orifices toward the inside. This change in angle means different hose routing. You'd end up either redoing your regulators whenever you switch tanks or getting separate reg sets for steel-primary and AL80-primary diving.

And also, the difference in hose routing could lead to needing different hose lengths. When I dive steel primaries, I need a fairly long hose for my necklaced reg, but when I dive AL80 tanks in SM with my rebreather, I need a much shorter hose for the necklaced reg. Again, you could need to change hoses every time you change tanks.

 

[Arsham]

AL80s are very commonly used for stage/deco/CCR bailout.

If you’re diving cold water in a drysuit with thick undies, they may be less desirable for SM as you will need more lead than if you were diving steels SM. Plus I find having to deal with the floaty butt is annoying.

Since Alu tanks are used for stage due to price, since I've found new Tecline military steel 11 liter tanks with cheaper price than new Polaris Alu 11 liter tanks, then maybe I should go with that option for my stage tanks too, as I do most of my dives in cold water with dry suit.