AL Twins vs Stage

[David Novo]

I have a liveaboard approaching for Maldives deep south and I have a high gas consumption.

I regularly dive twin steels at home with a drysuit and I am considering the following options (not as redundancy but as added gas):
1) AL twin set (11.1L x 2);
2) AL 13.2L backmounted plus 5.7L stage.

I will be diving a steel backplate (the only I have) plus potentially weight on a belt (2 kg in option 1, option 2 still have to calculate) and a 3 mm full wetsuit with 5 mm boots.

By my calculations I will be 6-7kg negative in the start of the dive at depth with option 1. I do believe I can swim them up if there is a problem with the wing (I have a DSMB if needed for additional emergency lift).

What is your opinion?

P.S.: Reducing gas consumption and changing backplate are not options at this time.

 

[Searcaigh]

The AL100s (13L) I have encountered are generally negative or near neutral when near empty, with a 3mm suit I think you should be fine.

I'm too lazy to calculate that stage size, is it AL40?

Anyway that's what I would use in preference to a twinset, which might be a PITA climbing up a ladder plus kitting up on the boat etc.

Use a 35lb lift wing.

 

[steinbil]

Are the doubles available on the boat? If so, it's nice to not have to deal with the stage and just dive the setup you're used to, with the added benefit of full redundancy. As long as you're weighted properly I wouldn't be too worried about diving AL doubles with a 3mm suit for recreational diving. The gas weight of the full doubles shouldn't be more than about 5kgs. I think 5kgs might be possible to swim up, but in any case you would have the option of ditching the weight belt or some gas while swimming against the weight if you have a complete failure of the wing over a bottomless pit (not that likely).

Benefits of the doubles:
- same config you're used to
- more gas
- more redundancy
- super stable/nice underwater
- easy to handle on the surface/ladder

 

[David Novo]

The AL100s (13L) I have encountered are generally negative or near neutral when near empty, with a 3mm suit I think you should be fine.

I'm too lazy to calculate that stage size, is it AL40?

Anyway that's what I would use in preference to a twinset, which might be a PITA climbing up a ladder plus kitting up on the boat etc.

Use a 35lb lift wing.

Yes the stage would be an AL40.

 

[David Novo]

Are the doubles available on the boat? If so, it's nice to not have to deal with the stage and just dive the setup you're used to, with the added benefit of full redundancy. As long as you're weighted properly I wouldn't be too worried about diving AL doubles with a 3mm suit for recreational diving. The gas weight of the full doubles shouldn't be more than about 5kgs. I think 5kgs might be possible to swim up, but in any case you would have the option of ditching the weight belt or some gas while swimming against the weight if you have a complete failure of the wing over a bottomless pit (not that likely).

Benefits of the doubles:
- same config you're used to
- more gas
- more redundancy
- super stable/nice underwater
- easy to handle on the surface/ladder

The doubles are available.

I am used to dive either config, it is the first time that doubles are available on a liveaboard I do.

 

[JohnN]

I have a liveaboard approaching for Maldives deep south and I have a high gas consumption.

I regularly dive twin steels at home with a drysuit and I am considering the following options (not as redundancy but as added gas):
1) AL twin set (11.1L x 2);
2) AL 13.2L backmounted plus 5.7L stage.

I will be diving a steel backplate (the only I have) plus potentially weight on a belt (2 kg in option 1, option 2 still have to calculate) and a 3 mm full wetsuit with 5 mm boots.

By my calculations I will be 6-7kg negative in the start of the dive at depth with option 1. I do believe I can swim them up if there is a problem with the wing (I have a DSMB if needed for additional emergency lift).

What is your opinion?

P.S.: Reducing gas consumption and changing backplate are not options at this time.

I dove with an AL80 on my back and another AL80 as a stage when I was in Fij

No problem back rolling off the boat, and underwater no problems with trim or balance. The boat crew did pull the stage bottle before I climbed up the ladder

It was nice to have lots of gas on the dives

 

[divezonescuba]

Gas consumption is what it is. I’d rather carry extra gas and relax than worry about my gas consumption.

Another option is independent backmounted doubles. If manifolded doubles are not available or cost more, I will use independent backmounted doubles. This is particularly effective in more remote locations with limited tank availability.

It used to be that only certain plate and wings could do independent backmount doubles. But, I invented a device called the DTA Double Tank Adapter that allows any backplate to use independent backmount doubles.



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[rongoodman]

I’d gladly use doubled 80s if they were available.

 

[rjack321]

I have a liveaboard approaching for Maldives deep south and I have a high gas consumption.

I regularly dive twin steels at home with a drysuit and I am considering the following options (not as redundancy but as added gas):
1) AL twin set (11.1L x 2);
2) AL 13.2L backmounted plus 5.7L stage.

I will be diving a steel backplate (the only I have) plus potentially weight on a belt (2 kg in option 1, option 2 still have to calculate) and a 3 mm full wetsuit with 5 mm boots.

By my calculations I will be 6-7kg negative in the start of the dive at depth with option 1. I do believe I can swim them up if there is a problem with the wing (I have a DSMB if needed for additional emergency lift).

What is your opinion?

P.S.: Reducing gas consumption and changing backplate are not options at this time.

I'd much rather use double 80s than a single plus something banging around on me

 

[Tracy]

The AL100s (13L) I have encountered are generally negative or near neutral when near empty, with a 3mm suit I think you should be fine.

What AL100s are you using? They are incredibly buoyant. At least a couple of pounds when low.