Just got my helitrox cert on the JJ - one of the nice things about CCR is that it removes that cost-benefit analysis from the decision. It costs so little to add helium to the dil, and hopefully I won't be going through a lot of bailout!
Requiring shallow helium mixes?
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Just got my helitrox cert on the JJ - one of the nice things about CCR is that it removes that cost-benefit analysis from the decision. It costs so little to add helium to the dil, and hopefully I won't be going through a lot of bailout!
Capt Jim Wyatt
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Yea, not even a consideration cost wise.
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I voted 200. At that point, ppO2 becomes an issue on air so I won't go deeper due to OxTox risk.
That said, you asked a few contradicting questions.
You said minimum mandatory helium mix, well the mandatory helium mix for me is 200ft due to oxtox
You also asked for reasonable necessity, well that depends. Am I diving in a high flow cave at 110ft on a rebreather, or clear, no current, wall diving on open circuit?
On a CCR if available, I really see no justification for diving anything but 21/35 or 18/45 in the dil until you get to ppO2 limits for work of breathing as alluded to above.
In a cave, the need for helium may come early as I have been Narc'd in Ginnie, even on a scooter.
Clear, calm diving in the ocean gives me a lot more tolerance for narcosis so I'd accept going a bit deeper.
As far as a hard stop, that hard stop for me is 200ft when the ppO2 of air gets to be a problem but the odds of you seeing me go that deep are rare, and you won't see me condone it
That said, you asked a few contradicting questions.
You said minimum mandatory helium mix, well the mandatory helium mix for me is 200ft due to oxtox
You also asked for reasonable necessity, well that depends. Am I diving in a high flow cave at 110ft on a rebreather, or clear, no current, wall diving on open circuit?
On a CCR if available, I really see no justification for diving anything but 21/35 or 18/45 in the dil until you get to ppO2 limits for work of breathing as alluded to above.
In a cave, the need for helium may come early as I have been Narc'd in Ginnie, even on a scooter.
Clear, calm diving in the ocean gives me a lot more tolerance for narcosis so I'd accept going a bit deeper.
As far as a hard stop, that hard stop for me is 200ft when the ppO2 of air gets to be a problem but the odds of you seeing me go that deep are rare, and you won't see me condone it
I voted 160. With good conditions, I will dive to 150 with no helium. If I'm planning for deeper than that, I would only plan to include helium. With less-good conditions, I would require helium at shallower depths.
Capt Jim Wyatt
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I don't dive OC helium mixes anymore...have not in several years....
MichaelMc
Working toward Cenotes
I don't think clearly in response to my computer at 100', I believe I do at 80', so that's my 'beyond here does not make sense' range. I'm not Trimix qual'ed but voted. Trimix for rec is an interest, but might be too expensive to be practical. My opinion is that beyond 90-100' I think want Helium, which means I want a rebreather for the cost, which is more complex, and still expensive, than I need to do now.
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Locally (so the UK), anything where the max depth is likely to be 39m+. We have a lot of dives where the max depth is around 33m-35m, but the wreck starts shallower (around 22-30m depending on the dive), and I don't worry about helium for those dives. But anything deeper, helium is added.
Capt Jim Wyatt
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In my rough estimate if you make 100 helium dives on a CCR vs OC you have saved enough $ on the price of helium to justify the cost of the CCR.
I'm not there yet but the way I do the math is a bit different @Capt Jim Wyatt . I can blend my own. 25/25 in a hp100 is going to take about 20cf. A big tank is 95 for 210cf so that's about 9$ a tank. ycmv
My point is that each situation is different and how rich your mix and how much you need is variable. A big expedition dive where you are paying through the nose for helium is going to be 100-200$ a pop depending on how crazy the numbers are that you fill in the blanks with.
Me, I'm just thinking to get a bit deeper without worrying about the buzz. I have seen my buddy seem too unconcerned with what she is doing at 100 feet. Everything is ok is not a proper response to you are too deep and descending. ok, ok, ok. No, not ok, snap out of it. Everybody is different.
But as I said, I'm not there yet. I still lack experience and training but it is in my future. 100 feet seems like a good maximum END. It doesn't take much helium, even in OC to achieve that if you are only going to 130 or 140.
I'm actually not in disagreement with your point so much as expanding the discussion. You do have a valid point depending on the details.
My point is that each situation is different and how rich your mix and how much you need is variable. A big expedition dive where you are paying through the nose for helium is going to be 100-200$ a pop depending on how crazy the numbers are that you fill in the blanks with.
Me, I'm just thinking to get a bit deeper without worrying about the buzz. I have seen my buddy seem too unconcerned with what she is doing at 100 feet. Everything is ok is not a proper response to you are too deep and descending. ok, ok, ok. No, not ok, snap out of it. Everybody is different.
But as I said, I'm not there yet. I still lack experience and training but it is in my future. 100 feet seems like a good maximum END. It doesn't take much helium, even in OC to achieve that if you are only going to 130 or 140.
I'm actually not in disagreement with your point so much as expanding the discussion. You do have a valid point depending on the details.
25% of a 100 cu-ft tank is about 20cf? I reckon your math IS pretty different...
If I'm diving helium, it's in my doubles, which are 2 x 120. My cert limit is 20%. So, 48 cu-ft. My shop charges $1.50/cu-ft. So, $75 per fill for helium, if I get trimix. 100 dives like that would be $7500, which would definitely put me in the CCR Ballpark.
I'm hoping I'll get a chance to finish TDI Trimix soon. Then I'll be diving deeper and using more helium in my fills. 100 (deepish) dives would definitely pay for a CCR.
ps. Where are you getting helium for less than $0.50 per cu-ft??
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