Discussion - merits of qualifying on multiple rebreathers?

[lv2dive]

I’m certified to dive 3 units and I got my CCR Cave and MOD3 certs on my first unit, a Meg, but they are unit-independent certifications. I’m not sure if unit-independent certs are still offered or not but personally I think it’s the way to go for advanced certifications. While I do not see myself moving away from my current unit (SF2), if I was interested in starting over with another unit, I would always take a crossover... but I don’t have to go through the progression again with a new unit.

With the SF2, I did dive it in caves from the beginning - because that is almost exclusively where I dive - but I did build up to MOD3 dives only after putting some hours on the unit / familiarizing myself with it. If I had to take MOD2 &3 and CCR Cave over again just bc I switched units, I’d be irritated.

All of that being said, I still agree with the majority of opinions shared in this thread. It’s important to have developed muscle memory on the unit before moving to the deeper dives. For the first time taking any CCR to hypoxic depths, it’s best to have well-developed muscle memory on the unit used for training. As a (hypothetical) instructor, I would not want my students to have met the minimum hours requirements based on two or three units.

 

[kensuf]

Stuff happens fast deep -- OC gas goes quickly, deco piles on quickly. You need to be able to respond correctly to a problem with your unit in a timely fashion and sometimes the best answer isn't "bail out / GTFO". Managing problems requires a level of muscle memory / comfort / knowledge / familiarity of the unit you're on.

On the plane thing, it's an interesting comparison to me. A guy I was friends with and his wife died in a plane crash last summer in Palatka Florida. My understanding is that it was his second flight in that plane without an instructor, and even though he had over 700 hours of flight time, the crash was caused by a fuel stop-cock being turned off, which caused the engine to cut off during take-off.

 

[lowflyer]

Managing problems requires a level of muscle memory / comfort / knowledge / familiarity of the unit you're on.
On the plane thing, it's an interesting comparison to me. A guy I was friends with and his wife died in a plane crash last summer in Palatka Florida. My understanding is that it was his second flight in that plane without an instructor, and even though he had over 700 hours of flight time, the crash was caused by a fuel stop-cock being turned off, which caused the engine to cut off during take-off.

That is exactly how John Denver died. He was an excellent pilot (substitute diver for this discussion) but wasn't used to his new airplane's fuel system (substitute different CCR unit).

 

[tomfcrist]

. Managing problems requires a level of muscle memory / comfort / knowledge / familiarity of the unit you're on.

Would you extend that to various models of the same unit?

Muscle memory is important. I’ll use the Optima as an example because I dive one. The differences in stock units are astounding over the last decade. Hammerhead>shearwater. Front lungs to back lungs, old back lungs to new ones. All have different locations and mechanisms for manual add, solenoid shutoff...etc.

 

[Jeremy Williams]

I agree that higher level certification on CCR being unit specific has some problems. Just like there are some problems with doing hypoxic-trimix-cave dives on a unit that you just switched over to using. Okay, maybe not that bad... but they are still real.

And I think the barriers go all the way up...

Can you imagine (using our popular plane analogies) a flight instructor that was only capable of training pilots on a Piper Cherokee? Because instructors have to buy the units and dive them a bunch before they can start teaching them, it becomes a massive commitment to be certified as an instructor on more than one unit. The entire rest of the scuba industry is pretty brand agnostic. You can use whatever gear you want (within reason) and most comparable certs from a reputable agency will function as a prerequisite for a different agency. GUE being the notable exception, but SCUBA is generally pretty cross-compatible.

But rebreathers are an exception for the most part.

I also suspect that (unlike airplanes) the global supply of rental rebreathers is vanishingly small. That fleet of available rental rebreathers is probably not very diverse or evenly distributed. How many places in the world can you rent a pair of rebreathers for a week of non-training dives for yourself and a buddy?

And that means that it is unlikely that the instructor for your Advanced Mixed Gas CCR class could do so on another unit that you might want because they need unit specific certs as an instructor too.

And while an instructor might be happy with you auditing a class you have taken from them before, a different instructor doing unit specific certifications is going to need to be paid again all the way up the crossover certification chain.

But I’m not sure how I would change it. Then again I’m not trying to buy my second rebreather and looking down the road at doing ALL the classes all over again as a crossover.

 

[hroark2112]

I'm certified on the Kiss and Optima. Totally different units, totally different operations, totally different assembly/disassembly/maintenance methods. Diving the two is not remotely similar. After 150 hours on the Kiss, one weekend on the Optima was miserable. It took at least 25 hours before I was even remotely comfortable on it. There is no way in hell that I should have taken that unit down to 200' until I was very proficient on the unit. It's just not a good idea.

 

[rjack321]

I have PADI CCR TEC 40 on Poseidon VI/VII, TDI Crossover on JJ and IANTD Crossover on O2ptima and on all three combined I have enough hours to do more advanced training but not enough on a single unit alone. I'm just a little perplexed that the combined time does not count, as although I am still a beginner on CCRs, I feel ready to go to another level on any of the three, but not ready yet to just buy/specialise in a single model.

Just out of curiosity here, how many hours do you have on each?

I'm certified on a Meg (~200hrs) and a Kiss (~45 hrs), completely different units. I have never done beyond Mod1 on either and I honestly dont really plan on doing trimix on CCR. I do have OC trimix and 400+ trimix dives.

 

[kensuf]

Would you extend that to various models of the same unit?

Muscle memory is important. I’ll use the Optima as an example because I dive one. The differences in stock units are astounding over the last decade. Hammerhead>shearwater. Front lungs to back lungs, old back lungs to new ones. All have different locations and mechanisms for manual add, solenoid shutoff...etc.

Yeah, I would. I'm not a fan of rental rigs for hypoxic diving either. Big boy dives require some level of big boy commitment.

 

[Caveeagle]

Just out of curiosity here, how many hours do you have on each?

I'm certified on a Meg (~200hrs) and a Kiss (~45 hrs), completely different units. I have never done beyond Mod1 on either and I honestly dont really plan on doing trimix on CCR. I do have OC trimix and 400+ trimix dives.

Just out of curiosity... why would you choose open Circuit tri-mix, when you have a CCR?

 

[rjack321]

Just out of curiosity... why would you choose open Circuit tri-mix, when you have a CCR?

Other way around!
I had OC trimix for a decade before I bought a CCR - I couldnt do the dives I wanted to do on OC anymore so I started with a Meg, then added a Kiss