Setpoint during fast decent, what do you use?

[mr_v]

lol that’s like asking AJ or Beckner etc if they have any cave experience

Look, I know only 2 people on this board. So when someone starts asking questions, etc. about the subject that I think is pretty straightforward and self-explanatory, I have to ask. There is no harm in that, but I can understand how written communication can sound a bit more harsh than a casual conversation.

 

[Agro]

Mod for 21/35 is 30 meter as dilluent for GUE ccr divers. The mod of 18/45 when using as diluent is 45 meter for GUE ccr divers.

My GUE ccr doubles contain 15/55 which has a mod of 60 meter when using as diluent.

Yes I know GUE's MOD is extremely shallow. I am not part of the GUE sect, nevertheless I look at their ideas. GUE's MOD is GUE's MOD, not Agro's MOD.

 

[Agro]

Does your instructor dive this way too? High O2, high gas density and high END?

I don't know.

 

[Agro]

Next week I will dive as follows: Jump from boat into water, current. We will have to dive to the bottom (52m) as fast as possible, no in water buddy check possible. We will use UPV to go down at max. speed. I hope we can do it within 2 min or less. No chance to switch SP manualy during descent. At target depth we must find the wreck, no time to loose. Current. I don't want to switch manually. In this case I will set autoswitch at 35m, always keeping an eye on the HUD.

On such a fast descent pO2 will probably spike if I switch to high SP at shallow depth. That's what I have learned here.

Dil will be 21/35.

Thanks for all the interessting posts.

 

[Wibble]

Curious about your dil choice of 21/35 even for 52m/175ft.

Personally, I’d use more helium >50% to ease the narcosis on the rapid descent and less oxygen <18% to reduce PPO2 spiking when inflating the loop. Maybe around 15/55.

Do you have banked gas available or do you mix it on demand?

 

[berndo]

I don't know.

If you had taken any half decent training, you would know.

 

[Wibble]

If you had taken any half decent training, you would know.

@Agro did say he's been on rebreathers for a long time, so training would have been a long time ago

 

[Wibble]

Time for a small digression into maintaining CCR skills.

This is not aimed at anyone in particular. OK, maybe myself.

One thing I've noticed about the move to CCR is how much there is to learn, the level of knowledge and a considerable effort to maintain those skills.

There's that old circle of learning (I often use the context of learning to juggle 3 tennis balls or learning an instrument):

• Conscious Incompetence
  • When you start a new skill, you're rubbish at it! Learning is hard, just doing it once or twice is bad.
• Conscious Competence
  • You've managed to get the skill but you really have to concentrate. If anything interrupted, it would all fall apart. Often see people with their tongue sticking out!
• UnConscious Competence
  • You've mastered it. Like walking or riding a bike, it's no problems. Sometimes referred to as muscle memory
• UnConscious Incompetence
  • Bad habits have developed. You take chances (e.g. driving). You are often unaware of how your skills may have degraded. You probably have that wake-up moment when either something terrible happens or someone tells you that you aren't great any more.
  • So do something about it.... Back to Conscious INCompetence to re-learn

Diving a rebreather's like that.

Sometimes you have to stop doing the big-boy dives and go back to basics and run over the initial skills. Maybe even pay someone to give you a big beasting session! But it's hard to stop doing the whole reason you moved to CCR to basically go backwards.

There's always more to learn. Being humble is one of them!

 

[berndo]

@Agro did say he's been on rebreathers for a long time, so training would have been a long time ago

I know a nigerian prince that wants to talk you about a business opportunity.

 

[Agro]

Curious about your dil choice of 21/35 even for 52m/175ft.

Personally, I’d use more helium >50% to ease the narcosis on the rapid descent and less oxygen <18% to reduce PPO2 spiking when inflating the loop. Maybe around 15/55.

Do you have banked gas available or do you mix it on demand?

21/35, pO2 1.3, 52m. There is nothing I would call "narcosis". If this produces narcosis I'd probably use Heliox.

Keeping low SP down to 35 will prevent O2 spiking, that's what I have learned from this discussion. I find 21% OK for 52m.