DIR- Generic dual bladder wings...

[Adobo]

So in running some math, if you just keep doing T1 dives to 170ft for 20 minutes and you assume an ACE of 200 minutes, 20kg of sofnolime is 170 bucks, and $237 for 3 O2 sensors every 50 dives (annual replacement.) You are looking at ~40$/dive on CCR in consumables, completely ignoring gas costs for the diluent and O2 you do use.

It would take 213 dives for the crossover between the OC and CCR to occur assuming no other parts needed to replaced or serviced in either system, and you never touched your bail out gas, I fully admit I could be misunderstanding some of the cost of CCR diving.

I'm not sure if that savings to me would make it worth switching to CCR for cost savings, I think there are other valid reasons to dive CCR when the logistics or parameters of the dive require it but for the T1 level it really seems like a lot of additional complexity and risk, but maybe that's my ignorance.

Although I know a couple of people who dive with JJ CCRs, I haven't the faintest clue how much it would cost to get into one - either the equipment or the training. I know even less about how they work in terms of what the related equipment are (I seem to remember people talking about the higher end Shearwater computers) or the consumables.

I appreciate that with the cost of helium, if you are an avid technical diver, the rebreather will wind up "paying for itself". The argument seems to be stronger for those who are doing tech 2 dives than divers who only go as far as tech 1 dives. I imagine the considerations are beyond costs though - sounds like they are far more complex to operate.

 

[crofrog]

It is your ignorance.

Is the math wrong or are you saying there is not more complexity and risk?

 

[Doby45]

Is the math wrong or are you saying there is not more complexity and risk?

Your math is wrong and with training it is no more complex or risky that an OC T1 dive.

I am not writing a dissertation this evening to prove a point to you but when you talk about 20min bottom times. I can do those dives on my rebreather without even topping off my tanks. I carry a 3L of O2 a 3L of inflation gas and 200cft of 18/45 bailout. I could actually do a NUMBER of those dives without ever topping of my tanks. Cost wise I would say it is approx $7 to fill my scrubber, which is good for 6hr. So lets say for grins and giggles I do 2 of those dives a day on some exotic vacation or a trip to the caves. I would do both those dives for a total of $7. I also don't know of anyone that just changes all three cells (or more) every 50 dives. Those normally get replaced on a rotation or a cycle. I have no idea where you got the "change all cells after 50 dives" or are you simply saying a cell is good for about a year. If that is the case, you would replace one about every 6 months for a cost of (roughly) $75.

Sooooooooooooooooooooooooooooooooooooooo, you have now done your 100 OC T1 dives and lets say I have paid for my rebreather in those same 100 dives. The very next time you go to dive your OC Trimix dive, I will be spending roughly $3.50 for that dive. We can even go hog wild and say I spend $10 for each of those dives (top off inflation and maybe O2). I still have you beat.

 

[Wibble]

So that's about 100 T1 dives before you've covered the purchase price of a JJ (not including any training or consumables for the CCR)

Did I do that math right?

Yes, if diving a CCR is only about helium prices.

CCR gives a ton of other benefits over open circuit, of course that bringing a load of other challenges. I like the flexibility of CCR, the absence of gas anxiety, the silence, the stability, lack of bubbles when inside a silty environment, warm and moist breathing, the (relative) lightness of the kit (compared with large doubles), the lack of a "hard" finish to a dive (e.g. not getting to min gas and being a few minutes away from your exit)...

All are intangiables, but most definitely benefits.

For tech 1 limits I'm assuming you're limited to about ~20 minutes at 170ft based on the 30 minutes of deco. Decoplanner spits out 92cuft of 18/45 for a 20min dive to 170ft. So about 75 dollars for the bottom mix, and 8 dollars in NX50.

A bottom time of 20 minutes at 47m/170ft with a <60min runtime??? Why on earth would you only do that?

Ah, single inefficient 50% deco gas which you have to consider as your one failure, so must be able to do the entire dive on backgas alone.

This is where doing normoxic training comes in where you've two deco gas cylinders -- 50% & 80% 100% -- where you can massively extend your bottom time.

Or doing that dive on CCR and you would double or even triple your bottom time -- for virtually no additional cost -- or do it with lots of helium for another $2.

 

[PfcAJ]

Your math is wrong and with training it is no more complex or risky that an OC T1 dive.

I am not writing a dissertation this evening to prove a point to you but when you talk about 20min bottom times. I can do those dives on my rebreather without even topping off my tanks. I carry a 3L of O2 a 3L of inflation gas and 200cft of 18/45 bailout. I could actually do a NUMBER of those dives without ever topping of my tanks. Cost wise I would say it is approx $7 to fill my scrubber, which is good for 6hr. So lets say for grins and giggles I do 2 of those dives a day on some exotic vacation or a trip to the caves. I would do both those dives for a total of $7. I also don't know of anyone that just changes all three cells (or more) every 50 dives. Those normally get replaced on a rotation or a cycle. I have no idea where you got the "change all cells after 50 dives" or are you simply saying a cell is good for about a year. If that is the case, you would replace one about every 6 months for a cost of (roughly) $75.

Sooooooooooooooooooooooooooooooooooooooo, you have now done your 100 OC T1 dives and lets say I have paid for my rebreather in those same 100 dives. The very next time you go to dive your OC Trimix dive, I will be spending roughly $3.50 for that dive. We can even go hog wild and say I spend $10 for each of those dives (top off inflation and maybe O2). I still have you beat.

It’s certainly more complex and risky. What are you even talking about?

It has all the complexity of OC, plus all the complexity of the rebreather.

It has all the risks of OC minus running out of gas, but has the added risks of hypercarbia, hypoxia, and unit induced hyperoxia.

Tech divers don’t often die from running out of gas, especially not in the ocean. It does happen from time to time but there’s usually other factors involved. They DO DIE from unit induced hyperoxia, hypoxia, and hypercarbia.

 

[Doby45]

It’s certainly more complex and risky. What are you even talking about?

It has all the complexity of OC, plus all the complexity of the rebreather.

You musta missed reading the part where I said "With training".

Driving a car in general is risky, you would even say that driving a race car is MORE risky. But the people driving race cars have the training for that function. With TRAINING the race car even though it is going faster is really no more risky. And while there are still deaths that occur on race tracks, safety is far more focused.

 

[PfcAJ]

You musta missed reading the part where I said "With training".

Driving a car in general is risky, you would even say that driving a race car is MORE risky. But the people driving race cars have the training for that function. With TRAINING the race car even though it is going faster is really no more risky. And while there are still deaths that occur on race tracks, safety is far more focused.

Training doesn’t eliminate risk. It can reduce as best.

Every ccr related death that I can think of involved a trained diver.

Its make pretend to say it has the same risk and complexity as OC. It’s simply not true.

 

[Doby45]

Training doesn’t eliminate risk. It can reduce as best.

Every ccr related death that I can think of involved a trained diver.

Its make pretend to say it has the same risk and complexity as OC. It’s simply not true.

okie dokie

 

[Adobo]

A bottom time of 20 minutes at 47m/170ft with a <60min runtime??? Why on earth would you only do that?

Ah, single inefficient 50% deco gas which you have to consider as your one failure, so must be able to do the entire dive on backgas alone.

This is where doing normoxic training comes in where you've two deco gas cylinders -- 50% & 80% -- where you can massively extend your bottom time.

Or doing that dive on CCR and you would double or even triple your bottom time -- for virtually no additional cost -- or do it with lots of helium for another $2.

Sorry to be that guy but..

Just a gentle reminder, this is the DIR forum.

 

[Wibble]

Sorry to be that guy but..

Just a gentle reminder, this is the DIR forum.

Ooops! Thanks

Changed to standard deco gasses