CCR Cave - Why take it?

[Pavao]

CCR Cave - Why?​

…
When we did a complex circuit, installing jump lines, and markers in a relatively small tunnel with a mud bottom and no flow the divers did not have complete control of their buoyancy and trim.…

Right, something I noticed while regrettably diving with a LOCAL CAVE CCR INSTRUCTOR. How can someone make it to instructor level and not posses the level of proficiency required at the diver level?

Guy was using the scooter to “maintain” buoyancy, when we got off the trigger, he silted out passages I had to get on the line to exit, passages I have been back to with non instructor friends we navigated without lifting a grain of silt

Imagine the quality of divers an instructor like that produces.

 

[grantctobin]

Right, something I noticed while regrettably diving with a LOCAL CAVE CCR INSTRUCTOR. How can someone make it to instructor level and not posses the level of proficiency required at the diver level?

You’d be positively blown away at what instructors can get away with, even with a litany of complaints against them to the agency.

 

[Dr. Doug Ebersole]

Yes. I also review their build checklists daily and keep a copy of them in their student folder. I scroll through their controller to understand the "settings" they have chosen and have them defend their choice of GFs and other user definable settings.

Thanks, Jim. Sounds like a great way to do things.

 

[lermontov]

two cave divers who have been certified as open circuit cave divers for over 20 year

they had never actually calculated their OC bailout volume requirements for dives they were doing

this doesnt make any sense-

i guess they were used to some sort of App to do a BO plan for a vertical ascent and not taken into account the horizontal part as in a cave environment ?

 

[kensuf]

Can a ccr cave instructor who is certified in one brand of ccr teach CCR cave course to students using a different brand ccr the instructor isn't certified on ?

Yes, but the instructor must be certified as "diver level" on the unit the student is diving. So although I'm not a Liberty instructor, I could teach CCR cave to a Liberty diver because I am a certified Liberty diver.

 

[inquis]

When we attempted a 1000-foot exit using SCR mode (as required by NSS-CDS standards)

Is this the SCR where you still have PO2 readings or have the electronics failed & you're counting breaths?

 

[Capt Jim Wyatt]

Is this the SCR where you still have PO2 readings or have the electronics failed & you're counting breaths?

Two methods:

1. Total loss of O2
2. Loss of electronics.

 

[mr_v]

When we attempted a 1000-foot exit using SCR mode (as required by NSS-CDS standards) these divers were unable to maintain buoyancy and frequently lost control of their buoyancy and trim. Divers should have mastered SCR mode in open water before practicing it in the overhead.

Jim, out of curiosity, what do you think triggered the buoyancy issues? Was it flushing with the newly plugged in SCR gas?

We do teach SCR mode in an entry level rebreather class at this point, however there are those who have stated that we can forego that skill in the entry level classes because we simply teach OC bailout if the CCR fails.

I never understood why someone would not want to learn how to extend gas ~4 times. Most folks who advocate for "bailout if CCR fails" probably underestimate RMV under stress. I recall talking with some Nor Cal divers who saw a shark. Their AL80s were as good as birthday balloons in terms of life support capabilities.

 

[Capt Jim Wyatt]

Jim, out of curiosity, what do you think triggered the buoyancy issues? Was it flushing with the newly plugged in SCR gas?

Doing the diluent flushes caused it because he had not worked on that since his mod 1 course 18 months earlier.

We also later discovered that his less than one year old DUI drysuit inflator button was sticking open and very slowly adding gas to his drysuit.

 

[kensuf]

I never understood why someone would not want to learn how to extend gas ~4 times. Most folks who advocate for "bailout if CCR fails" probably underestimate RMV under stress. I recall talking with some Nor Cal divers who saw a shark. Their AL80s were as good as birthday balloons in terms of life support capabilities.

I'm in the "don't focus on SCR mode in beginning CCR courses" camp. Speaking only for myself, the first few times I dove a rebreather it felt overwhelming for me (I describe the feeling like I was trying to run on an ice rink). Now, thinking of the general public, by virtue of being a new rebreather diver a person should not be in overhead environments, and at most, no more than 10 minutes of deco.

How much bailout gas do you need to ascend straight up from 120' with 10 minutes of deco? An AL40 will probably suffice for a lot of people, an AL80 will definitely cover it.

So what's the value in SCR mode in that environment? In terms of the cons, I can see people potentially skimping out on their bailout because "I have this fancy SCR mode tool in my belt" even though the reality is it's a skill they will likely never master in a beginning ccr course.

Why not focus on mastering a proper bailout and ascent in that environment, rather than teaching a perishable skill that's likely not going to be mastered in a 5-7 day course that's already overwhelming?

For mod2 and 3, and of course CCR cave, SCR mode has value. Keep in mind, people going into MOD2 or CCR Cave have at least 50 hours on their unit and should already have quite a bit of comfort on rebreathers. Different horses.