Why do some agencies recommend using a bottom timer instead of a computer

[rjack321]

Key points

1) The discussion on deep stop emphasis is not identical to the one on why one might use RD.
Firstly because RD evolves gradually, just like the scientific basis we have available does, and secondly because you can use RD and adapt it as you develop.
It's the intended purpose.

2) There is nothing in science to support the litigating parties in this discussion in their apparent view that RD is dangerous.

Nyt - none of UTD's RD changes have been science based. UTD's ratio deco has been through 3 major iterations and all of those changes have been based on Andrew getting older and not offgassing as well as he used to. They all have added time or moved the deco time done up shallower - so cough cough more like Buhlmann.

First change was in 2008ish: the 1:2 setpoint was changed from 220ft to 200ft because AG finally felt like crap using 220ft (funny how that happens after you turn 40)
Second change in 2012 ish: the insanely deep 75% of max depth deep stops finally get moved up (a quirk of the curve that Ross pointed out 12+ years ago)
Third change in RB2.0 (past year): the silly unsubstantiated O2 window milk trucks finally stop weighting the 50% portion of the ascent too deep and the S curve is debunked.

ALL of these RD attributes were made up from whole cloth in the original late 1990s/early 2000s version of RD. They are going away because they are biting people in the proverbial DCS butt and of course they were never substantiated beyond the hypothetical bubble theories of Yount and others in the first place.

 

[Dan_P]

Nyt - none of UTD's RD changes have been science based. UTD's ratio deco has been through 3 major iterations and all of those changes have been based on Andrew getting older and not offgassing as well as he used to. They all have added time or moved the deco time done up shallower - so cough cough more like Buhlmann.

First change was in 2008ish: the 1:2 setpoint was changed from 220ft to 200ft because AG finally felt like crap using 220ft (funny how that happens after you turn 40)
Second change in 2012 ish: the insanely deep 75% of max depth deep stops finally get moved up (a quirk of the curve that Ross pointed out 12+ years ago)
Third change in RB2.0 (past year): the silly unsubstantiated O2 window milk trucks finally stop weighting the 50% portion of the ascent too deep and the S curve is debunked.

ALL of these RD attributes were made up from whole cloth in the original late 1990s/early 2000s version of RD. They are going away because they are biting people in the proverbial DCS butt and of course they were never substantiated beyond the hypothetical bubble theories of Yount and others in the first place.

Spisni fell out of the sky, and UTD changing procedure can't have anything to do with something scientific - got it.
Yet both the S-curve and 75% stops were updated in RD2.0, after Spisni.

But the problem remains that the litigators here, when making claims to the effect that RD is dangerous, have no backing to make such claims.

Still, the disambiguation across using a standardized deco paradigm, and using increased deep stop emphasis, appears to somehow persist in its absence.

Regardless, the point is precisely that my working logic is I prefer RD for practical reasons, and its use isn't dangerous. I think it should be very obvious how that's different from saying that RDs deep stop emphasis is "more perfect" compared to the elusive "perfect algorithm", or any given range of algorithms for that matter.

The reply appears to be "but it's not algorithmically perfect".

This, paradoxally, in a world where there is no proof to say which algorithm is perfect, when it's perfect, for whom or why.

 

[boulderjohn]

2) There is nothing in science to support the litigating parties in this discussion in their apparent view that RD is dangerous.

You do realize, don't you, that this same glowing endorsement could be given to a plan devised by some drunk who knew next to nothing about decompression theory? You are essentially arguing in favor of something on the basis that it has not been truly studied.

 

[boulderjohn]

Doing linear extrapolation of a curve is really not hard at all - despite what Boulderjohn says about it.

I have no memory of making any statements along those lines.

 

[Dan_P]

You do realize, don't you, that this same glowing endorsement could be given to a plan devised by some drunk who knew next to nothing about decompression theory? You are essentially arguing in favor of something on the basis that it has not been truly studied.

No - and in either case, you're missing the point, and indeed basis of the conversation, entirely.

Take note - what I'm arguing in favor of, is pragmaticism.

You're counterarguing on the basis of something that has not been studied adequately to carry neither the ultimative truths you seem to be unilaterally basing your logics on, nor the litigations you regularly associate yourself with, perpetuate or instil - all while wrongfully claiming to be backed by science.

I won't hesitate to call the method employed in your litigations unscientific, for that reason.

Reversely, I acknowledge what science has to offer us, and incorporate it in my strategy when/where applicable. But I attribute practical considerations with significant weight in my evaluation.

That's not to say that there is a conflict from a scientific point of view - only a compromise in practical application.

When or if you call that dangerous, it's you that shall carry the burden of evidence.

 

[PfcAJ]

so would that be GUE's version, UTD's version, Steve Lewis' version or something else?

No ones interested in getting into the details.

“Ratio deco - bad” is the limit of brain engagement. Even if ratio deco put out an ascent schedule that matched whatever schedule one feels to be the “best”, because ratio deco was the method to get there it’s bad and dangerous.

 

[The Chairman]

I believe the first quote was intentionally emplying an indefinitive rhethoric.

This is typical behavior when you have vested so much in proving your methodology correct. It would appear that you've lost objectivity in your desire to be right. So much so, that you've lost the desire to find out what's right or even best. Ratio Deco fails @Dr Simon Mitchell's "Loved One Test". For those who aren't familiar with that test, it essentially asks you to decide if you trust a protocol, diver, instructor to the point that you would actually trust a loved one to dive with them. It cuts through all the posturing, the twisting and misunderstandings (ie BS) and gets to the core of their belief/disbelief of whatever you're discussing. It fails my "Loved One Test" as well. Friends don't let friends dive Ratio Deco.

Besides, if you believe that shallow is better, you can use RD and adapt shallower.

But why? What possible benefit could I accrue? There are better methods and more reliable protocols, so why cling to a faulty one? Just to prove you can? I don't dive to prove my deco strategy. No, I use my deco strategy so I can conduct a dive safely and concentrate on my dive. I'm coming to the end of my 49th year of diving and I've never been bent. Never. Why would I want to jeopardize that streak?

2) There is nothing in science to support the litigating parties in this discussion in their apparent view that RD is dangerous.

And in a poof of psuedo-logic, you throw common sense out of the proverbial window. The only courtroom we are in, is the one of diver opinion. Counsellor, you've absolutely failed to persuade anyone to go against the good Doctor's call to use a better protocol. He won't use RD. He won't let his family use RD. He won't teach RD and he does not encourage its use. How much clearer can you get? This is as much of a 'condemnation' as I have ever heard the Good Doctor give. Is it understated? Sure and that's a product of his scientific training. In any event, a reasonable diver would do well to heed his understatement. Friends don't let friends dive Ratio Deco.

Doing linear extrapolation of a curve is really not hard at all

At my desk? No, it's pretty straightforward. At depth? Oh, I can do it but I don't have the same cognitive abilities at depth, so I am excluding other tasks. Then, I have to remember to do it repeatedly. I can't forget to check, check, check my depth. Why? Why not let my PDC deal with all of those tasks? It's not prone to making those simple mistakes like I am. @Dan_P talks about "pragmaticism", and while he probably meant pragmatism, I understood the reference and believe that RD is anything BUT. Again, I don't dive to prove a protocol right. I dive a protocol to allow me to pursue my interests on a dive.

OK, I think I'm kind of done here. I'm starting to repeat myself which is never good. Ask me a question or similar and I'll reinsert myself into the thread. Just remember: Friends don't let friends dive Ratio Deco!

 

[Dan_P]

This is typical behavior when you have vested so much in proving your methodology correct. It would appear that you've lost objectivity in your desire to be right. So much so, that you've lost the desire to find out what's right or even best. Ratio Deco fails @Dr Simon Mitchell's "Loved One Test". For those who aren't familiar with that test, it essentially asks you to decide if you trust a protocol, diver, instructor to the point that you would actually trust a loved one to dive with them. It cuts through all the posturing, the twisting and misunderstandings (ie BS) and gets to the core of their belief/disbelief of whatever you're discussing. It fails my "Loved One Test" as well. Friends don't let friends dive Ratio Deco.

To me, this looks like a serious misrepresentation, but I'll let @Dr Simon Mitchell be the judge of that.
This one, too:

And in a poof of psuedo-logic, you throw common sense out of the proverbial window. The only courtroom we are in, is the one of diver opinion. Counsellor, you've absolutely failed to persuade anyone to go against the good Doctor's call to use a better protocol. He won't use RD. He won't let his family use RD. He won't teach RD and he does not encourage its use. How much clearer can you get? This is as much of a 'condemnation' as I have ever heard the Good Doctor give. Is it understated? Sure and that's a product of his scientific training. In any event, a reasonable diver would do well to heed his understatement. Friends don't let friends dive Ratio Deco.

I think your opinion on this subject lost any relevance it may have had
Here's why:

At my desk? No, it's pretty straightforward. At depth? Oh, I can do it but I don't have the same cognitive abilities at depth, so I am excluding other tasks. Then, I have to remember to do it repeatedly. I can't forget to check, check, check my depth. Why? Why not let my PDC deal with all of those tasks? It's not prone to making those simple mistakes like I am. @Dan_P talks about "pragmaticism", and while he probably meant pragmatism, I understood the reference and believe that RD is anything BUT. Again, I don't dive to prove a protocol right. I dive a protocol to allow me to pursue my interests on a dive.

All you're doing here, is demonstrate with perfect clarity that you have little to no grasp on the topic at hand, that is, Ratio Deco.
And it gets worse:

But why? What possible benefit could I accrue? There are better methods and more reliable protocols, so why cling to a faulty one? Just to prove you can? I don't dive to prove my deco strategy. No, I use my deco strategy so I can conduct a dive safely and concentrate on my dive. I'm coming to the end of my 49th year of diving and I've never been bent. Never. Why would I want to jeopardize that streak?

As I said, it's clear that you're ignorant to Ratio Deco, and if you'd asked questions rather than litigate, I would have bothered giving you answers.
It's fair enough that you're not interested - but to litigate RD in this fashion, I'd expect you to be more well-versed in its nature and application.

On a side note - no, I mean pragmaticism, as you'd recognize in the presentations I've made of my working logic - that is, if you'd even bother listening, and Charles Peirce rang a bell.

 

[The Chairman]

To me, this looks like a serious misrepresentation, but I'll let @Dr Simon Mitchell be the judge of that.

Serious accusations, but it goes hand in hand with you wanting to hear ONLY what supports your religion. Let's quote the good Dr, shall we?

However, at the same time, the answer to essentially all The Chairman's questions is "no": I would not choose to use it myself, recommend it to my family, teach it to other divers, or encourage others to use it. This is because there is a reasonable body of evidence that there are other approaches that almost certainly carry less risk.

What about "no" do you not understand? I didn't call that the "Loved One Test" when I posed those questions, but that's exactly what it is. How is it misrepresenting what the good Dr said? Moreover, how can you leverage that to a "serious" misrepresentation? You seem to be the one doing the "litigating" here.

I think your opinion on this subject lost any relevance it may have had

Not to reasonable thinking divers looking for truth. However, my opinion lost all relevance to you when it disagreed with yours. You want to attack the messenger now and not the message. Again, that is typical of trying to defend the indefensible. Stop dealing in vague dismissive verbiage and be specific about what I wrote and not that I wrote it.

As I said, it's clear that you're ignorant to Ratio Deco, and if you'd asked questions rather than litigate, I would have bothered giving you answers.

I am happily ignorant of how to use Ratio Deco in my diving and will happily continue that ignorance. I've already answered why, but I'll 'splain it again. Too many accidents. I know hundreds of divers and those who dive RD account for maybe %2. Unfortunately, they account for over %50 of divers I know who have gotten the bends. That's hugely astronomical and it scares the crap out of me. Mind you, all of those incidents were due to diver error. All of them. I make silly math mistakes all the time, so why would I endanger my health by relying on me to make any computations under water? Oh, wait: I don't.

Before I waste my time and precious cognitive resources to learn Ratio Deco, you would have to answer these questions to my satisfaction and that means it would have to pass my own "Loved One Test".

• Why the f@#$ does Ratio Deco account for such an inordinate number of DCS incidents?
• How can one prevent these kind of DCS incidents?
  • I avoid them by not using Ratio Deco.
• Have any studies shown Ratio Deco to be more reliable than any PDC?
• What benefit(s) would I accrue using Ratio Deco over my PDC? Any?
  • July starts my 50th year of diving without ever having had a DCS incident
• Why the f@#$ does Ratio Deco account for such an inordinate number of DCS incidents?

So far, I still firmly believe that friends don't let friends dive Ratio Deco. Change my mind.

 

[PfcAJ]

Serious accusations, but it goes hand in hand with you wanting to hear ONLY what supports your religion. Let's quote the good Dr, shall we?

What about "no" do you not understand? I didn't call that the "Loved One Test" when I posed those questions, but that's exactly what it is. How is it misrepresenting what the good Dr said? Moreover, how can you leverage that to a "serious" misrepresentation? You seem to be the one doing the "litigating" here.

Not to reasonable thinking divers looking for truth. However, my opinion lost all relevance to you when it disagreed with yours. You want to attack the messenger now and not the message. Again, that is typical of trying to defend the indefensible. Stop dealing in vague dismissive verbiage and be specific about what I wrote and not that I wrote it.

I am happily ignorant of how to use Ratio Deco in my diving and will happily continue that ignorance. I've already answered why, but I'll 'splain it again. Too many accidents. I know hundreds of divers and those who dive RD account for maybe %2. Unfortunately, they account for over %50 of divers I know who have gotten the bends. That's hugely astronomical and it scares the crap out of me. Mind you, all of those incidents were due to diver error. All of them. I make silly math mistakes all the time, so why would I endanger my health by relying on me to make any computations under water? Oh, wait: I don't.

Before I waste my time and precious cognitive resources to learn Ratio Deco, you would have to answer these questions to my satisfaction and that means it would have to pass my own "Loved One Test".

• Why the f@#$ does Ratio Deco account for such an inordinate number of DCS incidents?
• How can one prevent these kind of DCS incidents?
  • I avoid them by not using Ratio Deco.
• Have any studies shown Ratio Deco to be more reliable than any PDC?
• What benefit(s) would I accrue using Ratio Deco over my PDC? Any?
  • July starts my 50th year of diving without ever having had a DCS incident
• Why the f@#$ does Ratio Deco account for such an inordinate number of DCS incidents?

So far, I still firmly believe that friends don't let friends dive Ratio Deco. Change my mind.

Does use RD result in a higher rate of DCS?

Source pls.