Steel tanks vs. Alum.

[Remy B.]

the only difference between a Al 11L and a 10 Steel 230bar tank is 1 Kg in weight, and these steel tanks ( EU tanks ) are negative, I did a dive 10 days ago in Mallorca-Spain and used two 10L steel tanks, they are just perfect, they are smaller than the AL80 and lighter out of the water, these tanks will be my next additional bottom gas tanks to complete a total of 8500lts for bottom gas with 4 tanks.

AL are heavier out of the water, bulky and you need more lead in the water if you let them reach 50-60Bars.

 

[Patoux01]

The usual S80 is 14.3kg. (Luxfer at least)

10l tanks vary largely.
~12kg for Faber (some at ~11 also), 232bar
11kg for Roth, 230bar
11.5 (or 15) for ECS

So you have on average ~2kg less per tank, 4kg total on a diver. The tanks being smaller makes them easier to handle out of water (torque), and reducing the need for added weights too because they don't get floaty.


Sources:
L6X® aluminium SCUBA cylinders
Faber Industrie: Faber Cylinders for Scuba Diving
http://www.rothmions.fr/pdf/gamme_bouteilles.pdf
http://www.eurocylinders.com/sites/de/material/Tauchen-de.pdf

 

[Bigeclipse]

Aluminium cylinders get floaty bottoms during the dive and must be trimmed out. Steel cylinders stay negative for all the dive. If you don't have to negotiate restrictions, steels are quite comfortable - just clip them on and forget about them. But if you have to unclip the bottoms and bring them in front to get through a restriction, steel tanks will sink and make it difficult to maintain your trim. Thus, when diving with AL cylinders, you need a rig which allows to trim out the floaty bottoms. Xdeep Stealth 2.0 Tec arguably is the best SM system on the market right now, but Apeks, Razor and Diamond can handle AL tanks, too, with their sliding rings on the waist band. As far I've observed, it is more complicated with such systems as Hollis. For steel cylinders the important thing will be the lift capacity.

Can you tell me the complications with the hollis system as I'm about to purchase a Hollis SMS75. I mainly dive steels but may occasionally use aluminums as well. Are you referring to the Hollis systems being bad for steels or aluminums or both? I thought you could simply add d-rings to the belt of the Hollis to clip floaty tanks during the dive.

 

[Johanan]

Are you referring to the Hollis systems being bad for steels or aluminums or both? I thought you could simply add d-rings to the belt of the Hollis to clip floaty tanks during the dive.

I did mean that Hollis and similar SM systems, as they come out of the box are not so good for handling the floaty bottoms of AL cylinders. It is not a problem for steel cylinders which never float. Yes, I have heard about putting weights on AL cylinders and other slynesses to fix this problem. Perhaps sliding D rings can be added, too. But then, why shouldn’t one get a system like Xdeep, or Razor, or Apeks, or Diamond, which have them originally installed? These systems handle both steels and allies equally well.

A problem with steel tanks is that they are negative in the water. It would make it difficult to maintain a good trim, when you bring them forward in front of you, which is one of the special techniques in Sidemount diving.

 

[Bigeclipse]

I did mean that Hollis and similar SM systems, as they come out of the box are not so good for handling the floaty bottoms of AL cylinders. It is not a problem for steel cylinders which never float. Yes, I have heard about putting weights on AL cylinders and other slynesses to fix this problem. Perhaps sliding D rings can be added, too. But then, why shouldn’t one get a system like Xdeep, or Razor, or Apeks, or Diamond, which have them originally installed? These systems handle both steels and allies equally well.

A problem with steel tanks is that they are negative in the water. It would make it difficult to maintain a good trim, when you bring them forward in front of you, which is one of the special techniques in Sidemount diving.

Ok I get it, I have just heard when it comes to out of the box adjustability for fit etc nothing beats the Hollis sms75 and when it comes to just steels nothing beats it while the others are just ok for either but not the best. If all you have to do to make the sms75 work for aluminum’s is a few d-rings, that is hardly a deal breaker for me.

 

[Johanan]

I have just heard nothing beats the Hollis sms75 while the others are just ok ...

That may be true or just somebody’s opinion. I have no personal experience with the sms75. Last September one of the grandees in sidemount and cave diving told me, that at the moment Xdeep Stealth Tec 2.0 was the best system on the market, when it comes to how it behaves in the water. However, he is a European and the preferences sometimes have a regional character. It is a boon to have the same system which your buddies dive.

 

[DA Aquamaster]

That may be true or just somebody’s opinion. I have no personal experience with the sms75. Last September one of the grandees in sidemount and cave diving told me, that at the moment Xdeep Stealth Tec 2.0 was the best system on the market, when it comes to how it behaves in the water. However, he is a European and the preferences sometimes have a regional character. It is a boon to have the same system which your buddies dive.

The SMS 75 and the Xdeep Stealth are great examples of "it depends".

For example, the SMS 75 is perfect for the KISS Sidewinder CCR, in large part because it was designed around the SMS 75. In contrast the Xdeep rig is all but incompatible and won't work well with the KISS Sidewinder CCR. So despite both these rigs being highly regarded, one works superbly in a particular application and the other does not.

In my experience, there is no absolute "best" rig. What is optimum for one type of side mount diving may not work well at all in another type of side mount diving.

Rigs in the 35-40 pound lift range usually work pretty well for general purpose side mount diving and the SMS 75 (40 pounds) falls in that range.

The Dive Rite LS (35 pounds) also does well or general purpose side mount diving and it is very easy to trim some one out in one. It's better suited to smaller passages than the SMS 75, but is also less capable when it comes to multiple stages.

The Manta Side Mount System also trims out very well. It is a derivative of a razor style harness but with a 50 pound wing. As such it does well with multistage Florida type diving, but is also low bulk and the larger wing squishes down well in tight passages. It's not mentioned much, but it is a very capable rig.

The Nomad XT even has it's place. It will literally do everything from back mounted singles or doubles to side mount open circuit diving to side mount CCR with back mounted bailout. Now...it doesn't do everything well, it's no one's first choice in a small passage, and it usually needs some weight on the shoulders to trim out, but it offers a great deal of flexibility to a degree unmatched by any other rig.

 

[victorzamora]

Can you tell me the complications with the hollis system as I'm about to purchase a Hollis SMS75. I mainly dive steels but may occasionally use aluminums as well..

The SMS75 is extremely easy to get diving in steels cleanly out-of-the-box. It's just a matter of rigging your tanks/regs correctly and fine-tuning tank position by changing the length of the bungee. There's honestly very little to it.

For aluminum tanks, it'll take a little more work but nothing insurmountable. Sliding d-rings of some variety on the waist strap or a well-positioned fixed d-rings need to be added to move the bottom clip of the AL tanks forward. Honestly, a few dives in a pool with mostly-empty AL80s should get you pretty close.

For the "usually-steels, may occasionally use Alu" diver, the SMS75 is a good rig and you've got nothing to worry about.