why helium?
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I understood Dave to mean manifolded doubles when he said "fully redundant system", since the two sides can be isolated.
The fact is that, helium or not, as you go deeper, it makes sense to lay on more resources -- More gas, more redundancy, more skills, more training, more experience. Helium may or may not be more unforgiving of inaccurate ascents, but the fact is that deep dives near the deco limits are not going to be forgiving of poorly executed ascents, no matter what you were breathing.
My personal approach is that rock bottom always needs to be observed, and the need for a fully redundant system is going to depend a little on dive conditions and expected hazards. In our cold, murky water, I don't do dives at the 100 foot level or below without my doubles. In Cozumel, I did 100 foot dives on a single HP 100. In both cases, I had trained buddies that I was extremely unlikely to lose. That's the non-negotiable piece of "equipment"
The fact is that, helium or not, as you go deeper, it makes sense to lay on more resources -- More gas, more redundancy, more skills, more training, more experience. Helium may or may not be more unforgiving of inaccurate ascents, but the fact is that deep dives near the deco limits are not going to be forgiving of poorly executed ascents, no matter what you were breathing.
My personal approach is that rock bottom always needs to be observed, and the need for a fully redundant system is going to depend a little on dive conditions and expected hazards. In our cold, murky water, I don't do dives at the 100 foot level or below without my doubles. In Cozumel, I did 100 foot dives on a single HP 100. In both cases, I had trained buddies that I was extremely unlikely to lose. That's the non-negotiable piece of "equipment"
Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else
, and a bottom gas/travel mix similar or the same to what you are breathing at 200? 3 different bottles? What would be your ascent/deco profile with bailout from 200' on whatever mix you would choose?
JeffG
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Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else
The rebreather divers I have talked/dived with would have 1 bottle of bottom gas (to get them from the bottom to the first deco stop) and may have mulitple deco bottles in reserve. The types and quantity of bottles differ between RB users, but I do know of some RB divers that carry the same deco bottles as a GUE/DIR open circuit diver (for the same depth of dive).
I carry a bottom bailout, using a high PO2 for 200ft 21/35 would do fine then carry one or two deco mixes. I would not use O2 as my primary deco mix but would probably use 50% for the dive you described. I would use a profile generated my v-planner at +2 for ascent and revert to my HS explorer for bailout.Do you carry multiple bailout gases? If so, would I be correct in assuming that for the dive I postulated that you would carry 02, something else
I could also use a team bailout plan in some circumstances since the deco gas would only get used if there was bailout requred.
Do you have a plan for lost deco gas or lost bailout if diving with someone else on an RB? Do you insist that all those diving together (assuming all on RB's) carry the same bail out gas? What happens when the depth gets in the 240' plus range and you start needing a s**tload of gas for both deco and ascent?
I deco on my rebreather so gas usually doesn't get touched until last dive in the series when I might do bailout drill.
All contingency plans are based on one major failure, either loss of RB, loss of bailout gas, loss of buddy and immediate dive enders. If I have to make contingency plans for multiple failures I would be too scared to get in the water. Too many permutations for me to consider.:11:
Gotcha, but would you carry all the gas reserves you needed for bail out on a dive in the 240-300' range? Seems like a lot of bottles. Do RB divers as a rule insist that you run your RB's with the same pp02s and then carry the same deco gas or is it every RB'er for themselves?
I would carry all bottom gas, and share deco gas 1.5 times that required for team. Team bailout also allows for optimal deco gas mixes as well.Gotcha, but would you carry all the gas reserves you needed for bail out on a dive in the 240-300' range? Seems like a lot of bottles. Do RB divers as a rule insist that you run your RB's with the same pp02s and then carry the same deco gas or is it every RB'er for themselves?
Okay, so for a 20-30 minute dive to 200' where you have oodles of gas in OC, particularly if you carry a stage (which sounds like you are doing essentially) what is the advantage of a RB? Sounds like you are carrying the same amount of bailout gas as I would.
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