Some questions for all you rebreather pilots...

[OMANDIVER]

hi Nasser, thanks for asking these questions, they are some that many OC technical divers are thinking about. Longer bottom time would be the main benefit. He costs for OC are through the roof is another, and can only get worse (although fixed and training costs for CCR are substantial). One of my concerns is how frequently does one need to use a unit to stay current on it ie roughly how many dives a year? not from a financial point of view but from the skills and safety perspective.

 

[mathauck0814]

1. I understand that CCR’s basically come in three flavors - eCCR or mCCR or hybridCCR… what kind do you choose to currently dive and why? Also what brand of CCR do you use?

This one is a bit religious. I'll draw the analog to how you drive. If you're the "cannot own a car without a clutch" type you're not going to get on well with an eCCR. I don't even like being a passenger in a taxi with an automatic transmission; I dive a mCCR. Wife is a serious photog and wants hands free, she's diving hCCR.

2. How different do you find CCR to Open Circuit in terms of the actual diving technique ? was it a huge learning curve?

Personal experience is that it was hard to learn CCR diving. I had thousands of dives on open circuit. My wife had far fewer dives (only several hundred to OC tech) and didn't understand my struggle at all. Based on that, I suspect the earlier you transition the less you'll have to un-learn (but there's a balance because I firmly believe that you should be qualified to 100m on open circuit before pursuing CCR as you'll need to have those skills dialed in, in a very absolute way).

3. Is there anything that you still prefer in open circuit over CCR?

No, but I have learned to really appreciate freediving since I left open circuit diving. I've either got no gear or all the gear these days.

4. Finally… how safe do you find CCRs in general? are there any brands or types (electronic vs. manual) that you find safer over the other?

How much do you dive? 4-6 hours/week is a good week of diving, less is very rare, 10+ hours/week is quite a good week. I believe that CCR is about muscle memory and addressing the issues that come up through simple probability. Both frequency AND recency are important. If you dive a lot, I think CCR gives you a whole sh!tload of options you wouldn't otherwise have. If you don't dive a lot, the complexity of the procedures will probably make you more likely to hurt yourself.

---------- Post added July 31st, 2014 at 05:30 AM ----------

So I guess we should have to present CCR cert before we post in this forum?

Yes. You're ignorant.

---------- Post added July 31st, 2014 at 05:32 AM ----------

No matter how much bottom time that rebreather gives you, it doesn't bring you any closer to the surface or make your body decompress any faster. Keep that in mind.

I guess your understanding of fixed PPO2 and how it impacts decompression is also incomplete?

 

[2cold4california]

This one is a bit religious. I'll draw the analog to how you drive. If you're the "cannot own a car without a clutch" type you're not going to get on well with an eCCR. I don't even like being a passenger in a taxi with an automatic transmission; I dive a mCCR. Wife is a serious photog and wants hands free, she's diving hCCR.



Personal experience is that it was hard to learn CCR diving. I had thousands of dives on open circuit. My wife had far fewer dives (only several hundred to OC tech) and didn't understand my struggle at all. Based on that, I suspect the earlier you transition the less you'll have to un-learn (but there's a balance because I firmly believe that you should be qualified to 100m on open circuit before pursuing CCR as you'll need to have those skills dialed in, in a very absolute way).



No, but I have learned to really appreciate freediving since I left open circuit diving. I've either got no gear or all the gear these days.



How much do you dive? 4-6 hours/week is a good week of diving, less is very rare, 10+ hours/week is quite a good week. I believe that CCR is about muscle memory and addressing the issues that come up through simple probability. Both frequency AND recency are important. If you dive a lot, I think CCR gives you a whole sh!tload of options you wouldn't otherwise have. If you don't dive a lot, the complexity of the procedures will probably make you more likely to hurt yourself.

---------- Post added July 31st, 2014 at 05:30 AM ----------



Yes. You're ignorant.

---------- Post added July 31st, 2014 at 05:32 AM ----------



I guess your understanding of fixed PPO2 and how it impacts decompression is also incomplete?

Apparently your own comprehension of medical science is incomplete. Are you just spouting words you think are complicated in the hopes that I don't understand?


You don't understand. Yes, by manipulating oxygen concentrations you can shorten decompression. That doesn't change the fact that the pressure remains the same whether on OC or CCR. If you were to have infinite gas changes you could so the EXACT same thing with OC.


So try again.



Edit: I did not actually read your whole post. I still haven't, but that's ok I'm pretty sure the rest of it was just as ill conceived.

 

[mathauck0814]

You don't understand. Yes, by manipulating oxygen concentrations you can shorten decompression. That doesn't change the fact that the pressure remains the same whether on OC or CCR. If you were to have infinite gas changes you could so the EXACT same thing with OC.

Please, enlighten us with your plan to actually do this EXACT dive on OC.

 

[Dr. Lecter]

Ifyou were to have infinite gas changes you could so the EXACT same thing with OC.

And if you were to have any experience with CCRs, you could comment intelligently in this thread - but there's no point in discussing what we all know are practically impossible situations as if they're relevant.

 

[2cold4california]

And if you were to have any experience with CCRs, you could comment intelligently in this thread - but there's no point in discussing what we all know are practically impossible situations as if they're relevant.

I will admit that I was not totally correct when I stated that CCR did not decrease decompression time. It can, if done properly.


My other criticisms still stand.

 

[kwinter]

He's a troll trying to increase his post count. Best advice is to ignore him.

Back to our regularly scheduled program. I disagree a bit with Mathauck about the clutch analogy. You can set your setpoint low on eCCR and fly the unit manually. The difference is that you won't have a CMF orifice or "leaky valve" to bleed in a constant flow of O2 and you will have to do that manually.

After playing with the idea of converting my eCCR to hybrid, I instead bought a rEvo hCCR and soon discovered I really did not like having the leaky valve. So now I'm back to an eCCR (rEvo for sale). Maybe I'm just more comfortable on it because that's what I started with and used for years.

 

[2cold4california]

Please, enlighten us with your plan to actually do this EXACT dive on OC.

Kudos you caught me in a fib. It is actually impossible to replicate the exact dive on OC. You can't adjust PPO2 on OC without changing air sources.

 

[mathauck0814]

I disagree a bit with Mathauck about the clutch analogy. You can set your setpoint low on eCCR and fly the unit manually. The difference is that you won't have a CMF orifice or "leaky valve" to bleed in a constant flow of O2 and you will have to do that manually.

I did say that this was the one that was closest to religion. Running an eCCR in the way that you describe is (IMO) the worst of all worlds. I now HAVE to manually add constantly because I don't have a CMF orifice to keep things in line AND I've added a computer driven solenoid that can stick open. More tasks to manage AND more things to go tits up.

Last I'll comment on the matter as it's one of those conversations that devolves quickly. There are pros and cons of each of the models. No perfect rebreathers yet.

 

[Dr. Lecter]

It's my understanding you've gone past the 100m mark on a revo, so I'm curious to hear how you overcome the depth restriction on the CMF...or are you just plugging in offboard O2? I've personally just handled the O2 addition manually below the depth limit on my 1ATA reg providing CMF, but eventually even that would become a problem...and of course there's the risk (I consider small, but still) of hypoxia should the diver cease manual addition w/o having either functioning CMF or a solenoid.