Multiple Stages when ?

[Depth-junkie]

OK, you have been diving using a twin set and a stage of say 50% for the last year, dives are to around 40-45 mtrs but the run times are getting longer, and so is the deco.
When is the best time to start using stages of say one of 40% and one of 80%, and are there any more things to look out for, i know the old addage "rich is right" but just want a few views on the subject.

FFS, when one deco cylinder does not hold enough gas to complete the deco....pretty simple really, which honestly is when you are hitting 60m+ or 50m dives with 45min-1hr BT's!!!

Anything less is 1 deco cylinder for me when i was OC diving





ATB
Gareth

[Mark Chase]

Originally Posted by Peter M

OK, you have been diving using a twin set and a stage of say 50% for the last year, dives are to around 40-45 mtrs but the run times are getting longer, and so is the deco.
When is the best time to start using stages of say one of 40% and one of 80%, and are there any more things to look out for, i know the old addage "rich is right" but just want a few views on the subject.

I used two stages from 40m and down. Diving say the Moldavia 45m for 60mins bottom time my deco would be 72mins using 32% and 80%. I ran steel 7s but I could easily do the dive on two Ali40s Running 50% for deco I needed 100mins of deco and a steel 10 blown high or a Ali80 blown high and there would be very little in the way of reserve gas.


I used 21/35 32% and 80% for all my deco diving below 40m. Above 40m Id use a single stage of 50%


I prefer rich right, lean left, lean mix on (and used as suit inflate to save carrying another tin) rich mix gassed up but off. To me rich right is a no brainer when you need to know where your breathable gas is.

I cant say carrying two 7s ever bothered me much. My aim was to max the bottom time. In doing so i often ran very low on back gas so having a deco mix you can get on deep is a bonus. On a dive like the Moldavia id happily run back gas down to 30bar in the 12s before considering going home as i only had to go up a couple of M before going on the 32%. If your going to carry two stages you might as well be able to get on it deep to save on back gas.

Believe it or not running say 40% and 80% for this dive extends the deco to 84mins and running 50% and 100% extends it to 76mins so i lose nothing by having 32% as my deep deco mix.


The problems you will find with a left right configuration is you have no clear side to access pockets D rings etc and you will need to think careful about your equipment positioning. Apart from that I always found it like diving in an armchair Their are other problems but until you start putting trimix in the deco tanks you wont need to worry about them .

ATB

Mark Chase

[finbar.taylor]

I would often do dives to 45m with 2 stages.

part of my solo gas planning was catering for lost deco gas by having say 32 & 80 with air backgas if the 32 failed no real drama as it was only going to be for the deep stops and if the 80 failed then 32's better than 21! having 2 stages you can also swap regs across from cylinders much easier than trying to unscrew one behind your head!

Fin

[japandiver]

I'd suggest that anything over 45m merits two stages - I use a 32 and an 80 in Ali 40's. One useful bonus of this is that you generally find that after using the 80% cylinder it has just a tad more gas in it than needed for an air top off to produce your 32% for the next outing.

Hugh

[David Pye]

Originally Posted by GLOC

There will be a point (unless you are solo diving) that you do not have enough back gas to get you and your buddy to the gas switch at 21m.
<snip>
Just something to think about, rules of thirds doesn't necessary mean that you can get to the switch with your buddy on your long hose.

I'm a bit curious about this one - I'm not really conscious of how everybody does failure planning, so please excuse me if I'm being naive.

Do you plan for the contingency of your buddy to have a complete loss of backgas, even if they're on twins? Or do you expect them to be able to isolate and save a certain percentage of their gas?

David

[stevechesh]

Originally Posted by David Pye

I'm a bit curious about this one - I'm not really conscious of how everybody does failure planning, so please excuse me if I'm being naive.

Do you plan for the contingency of your buddy to have a complete loss of backgas, even if they're on twins? Or do you expect them to be able to isolate and save a certain percentage of their gas?

David

Assuming your post wasn't only meant only for Gloc, i'll reply on the way i do it with the guys in our little group. We all carry an extra stage as bailout that doesn't come into gas planning. That way, hopefully, we'll all get to the surface in one piece having completed our deco obligations. You MUST isolate. There are no prizes for 2nd place. if you can't then you need to look at indies. My sets are all manifolded, but i can certainly see the advantage of indies. . . . . Just remember, there are pro's and cons with both (but thats another thread and has been done to death!)


we all dive solo/same ocean ish, but we only carry and plan the gas for ourselves as individuals. In an ideal world, we should be self sufficient, but it's not ideal all the time. If the worse comes to the worse, then we'll send up a yellow blob to get gas dropped down to us. Now assuming that doesn't happen, you can be in the poo a bit, but if the diving you're doing starts to get this critical, then it's time to look at returning to a trapeze with spare cylinders or carrying enough spare gas in the 1st place.

Just remember that if you only have 1 drop bottle and 12 divers. it's a bit of a lottery if 2 yellows turn up on the surface!

[johnkendall]

Originally Posted by David Pye

I'm a bit curious about this one - I'm not really conscious of how everybody does failure planning, so please excuse me if I'm being naive.

Do you plan for the contingency of your buddy to have a complete loss of backgas, even if they're on twins? Or do you expect them to be able to isolate and save a certain percentage of their gas?

David

My gas planning always allows for 1 major failure. So I plan for 1 team member losing all their backgas for whatever reason. Remember a freeflow is not the only problem that could occur. There are other things that could occur to prevent you isolating, and some failures that isolating won't fix (for example an isolator failure)

HTH

John

[GLOC]

Originally Posted by David Pye

I'm a bit curious about this one - I'm not really conscious of how everybody does failure planning, so please excuse me if I'm being naive.

Do you plan for the contingency of your buddy to have a complete loss of backgas, even if they're on twins? Or do you expect them to be able to isolate and save a certain percentage of their gas?

David

As John, to be expected really

[Peter M]

Originally Posted by japandiver

I'd suggest that anything over 45m merits two stages - I use a 32 and an 80 in Ali 40's. One useful bonus of this is that you generally find that after using the 80% cylinder it has just a tad more gas in it than needed for an air top off to produce your 32% for the next outing.

Just what i thought !