Diving Stages instead of Back Gas?

[Reg Braithwaite]

I've just met the third person who (a) Seemed to be DIR, and (b) Professed to diving stages nearly all the time and saving back gas for emergencies. Now this is strictly anecdotal, and perhaps I misunderstand what I have been hearing, but the protocol seems to be to fill the doubles with something that works at every depth you might plan, then leave them full for the season. Then you dive and refill stages as you go.

Am I understanding this right? And if so, is this DIR practice? One part of my brain thinks this is adding complexity where none is needed, but perhaps when you're scootering out to wrecks you're carrying some extra bottles and one more doesn't make a big difference...

Any ways, I wondered if any DIR practitioners could comment on this protocol. Thanks in advance!

 

[Blackwood]

On the West Coast it's common to find people doing the following (note - this is for dives that ordinarily wouldn't require a stage):

dive 1: descend on a stage, suck it more-or-less dry at depth, go to backgas and begin the ascent, switching appropriately to deco gas
dive 2: normal (no stage)

That allows you to get two dives one one set of doubles. Also, what's left in the doubles is often enough to fill a stage, so you can get in the pattern of doing two dives for the cost of one fill.


The procedure you described seems odd to me. I'm not lugging doubles onto a boat that I only plan to use in an emergency.

 

[rjack321]

I'm not sure how you decided they "seemed to be DIR" or if that's relevant.

Reserving some backgas is common in caves. Reserving <all> of your backgas is a bit rarer, you need to be bringing quite a few stages along before the volume of gas used to penetrate in the stages = the volume of gas in doubles. (Beyond that volume safety bottles are deployed.)

For ice diving in your area, its common to reserve 100% of backgas because freeflows seem to come in successive overwhelming waves. Reserving backgas for emergencies keeps those regs "unused" and ice free so if you switch to them they are less likely to immediately start to freeze up and compound the original problem.

In OW, I don't see a good reason to constantly dive stages and reserve 100% of backgas. Maybe you should ask the people who are doing this the "whys" and whether there is more to it than mere practice.

 

[rjack321]

On the West Coast it's common to find people doing the following (note - this is for dives that ordinarily wouldn't require a stage):

dive 1: descend on a stage, suck it more-or-less dry at depth, go to backgas and begin the ascent, switching appropriately to deco gas
dive 2: normal (no stage)

That allows you to get two dives one one set of doubles. Also, what's left in the doubles is often enough to fill a stage, so you can get in the pattern of doing two dives for the cost of one fill.

We sometimes do this too.

We also may do 1 normal tech dive and then a 2nd shallower MDL dive on a 80 stage of 32%. Switching to a less expensive gas with a shallower EAD.

 

[sea2summit]

I've seen it done a lot in caves, doubt it's "DIR" but I'm sure some DIR guys do it. It only makes sense diving thirds 1 AL 80 plus 200cft on your back you can go as far as the 80 will take you and still be well within your thirds or able to do multiple dives off one set of doubles.

If your not DIR the thing that makes sense is to go CC

 

[ivobj]

I used that in caves, you go in breathing from the stages and leaving then clipped in the cave cable as you enter, and comes out breathing from back gas clipping the empty stages to take them out (or leaving to your suport team to take out, if you have one), so in the deeper part of the dive into the cave you are lighter.

The logic is that in an emergency, from any point in the dive you will always have gas leave the cave only in your back gas and if necessary can leave all the stages behind, if you breath from back gas first you will necessarily have to drag the stages with you or you can run out of gas in the way out. Of course if your emergency is a severe leak in your back gas you will most probably need to share gas with your buddy, but if you breath back gas first and have a severe leak in one of the stages this could happen as well, so odds are the same.

 

[ppo2_diver]

We will normally dive a bottom stage when doing two tech dives in one day. That saves some back gas for the second dive where the bottom stage isn't necessary. Our bottom stage will have the same gas mix as our doubles.

 

[b1gcountry]

Diving with bottom stages was part of my trimix class. Non-GUE, but taught by a very DIR instructor.

I recently signed up for a charter with the first dive to 180', and second to 125'. I had some 18/45 in my doubles, and an AL80 stage of 28/20. Unfortunately, that got weathered out.

Tom

 

[S. starfish]

I've not heard of anybody diving a stage and reserving the entire backgas for emergencies around here, but you will find people diving stages to save money when diving trimix. The idea being that rather than bleed off the last few 100 psi of trimix remaining in your tanks after each dive you fill your doubles with a blend that will work at all depths you plan on diving, then you fill a stage, suck it dry and do the ascent on your bg for a few dives. That way you end up only bleeding away that last few 100 psi once.

 

[RTodd]

I've just met the third person who (a) Seemed to be DIR, and (b) Professed to diving stages nearly all the time and saving back gas for emergencies. Now this is strictly anecdotal, and perhaps I misunderstand what I have been hearing, but the protocol seems to be to fill the doubles with something that works at every depth you might plan, then leave them full for the season. Then you dive and refill stages as you go.

Am I understanding this right? And if so, is this DIR practice? One part of my brain thinks this is adding complexity where none is needed, but perhaps when you're scootering out to wrecks you're carrying some extra bottles and one more doesn't make a big difference...

Any ways, I wondered if any DIR practitioners could comment on this protocol. Thanks in advance!

You are confusing cave practices with OW ones. Other than some of the logistics issues discussed above (and ignoring the nickel rocket reasons), it is not common for open water dives.

Read this thread and you will have learned everything you need to know to do complicated stage dives on the internet and won't need to take any time consuming GUE classes which might teach you something.

http://www.scubaboard.com/forums/dir/212464-stage-planning-caves.html