Shearwater coming out with new DC?

[scubadada]

That's not true. KenGordon is correct. There is a difference between being conservative, and just being slow. People forget it's not just the time, it's the profile. The deep stops debate is proof enough of this.

Say you do a dive at 30/70. Say 50m for 30m using 70% as a deco gas. You feel bad afterwards. What do you change to? 10/70? 70/70? How do you decide?

Oh Johnny, what's true and correct for you does not necessarily apply to others, it's not black and white. I carefully laid out my diving profile in an earlier post, it would appear very different to yours and Ken's. This is often the problem when rec and tec divers try to communicate in the same thread. I don't think we are actually arguing about anything. I will come up fast from my rec dives, you may come up as slow as you want from your tec dives. I have been very interested in dive safety and the relationship to decompression algorithm for quite a long time. I had high hopes for DAN's PGE to shed light on this topic. All I can conclude is that all commercial decompression algorithms are approximately as safe. This is probably not surprising as all are "relatively" conservative. So, I will spend more time underwater and less time surfacing than some of my peers.

Good diving, Craig

 

[JohnnyC]

Oh Johnny, what's true and correct for you does not necessarily apply to others, it's not black and white. I carefully laid out my diving profile in an earlier post, it would appear very different to yours and Ken's. This is often the problem when rec and tec divers try to communicate in the same thread. I don't think we are actually arguing about anything. I will come up fast from my rec dives, you may come up as slow as you want from your tec dives. I have been very interested in dive safety and the relationship to decompression algorithm for quite a long time. I had high hopes for DAN's PGE to shed light on this topic. All I can conclude is that all commercial decompression algorithms are approximately as safe. This is probably not surprising as all are "relatively" conservative. So, I will spend more time underwater and less time surfacing than some of my peers.

Good diving, Craig

I'm not being argumentative, what KenGordon said is fundamentally true. "It's not black and white" proves my point for me. We disagree that you think it's simply a communication issue, it is not. Your opinion is wrong, it has been proven by science. The idea that if you're slow you're conservative is not necessarily true, and the idea that if you're fast you're being way too liberal. It's not just people using different words for different things. The fact that people still get bent on both recreational as well as technical dives is proof enough that it's much more complicated than just saying "conservative is another word for slow." It is not a communication issue.

 

[SillyQuestions]

Tell you what, hitting correct ascent rates definitely does NOT feel slow!


Sent from my iPhone using Tapatalk

 

[scubadada]

I'm not being argumentative, what KenGordon said is fundamentally true. "It's not black and white" proves my point for me. We disagree that you think it's simply a communication issue, it is not. Your opinion is wrong, it has been proven by science. The idea that if you're slow you're conservative is not necessarily true, and the idea that if you're fast you're being way too liberal. It's not just people using different words for different things. The fact that people still get bent on both recreational as well as technical dives is proof enough that it's much more complicated than just saying "conservative is another word for slow." It is not a communication issue.

You really seem stuck on your perspective, you are right, and I am wrong. Tell me more about the "proven by science". Perhaps we're mainly being limited by vocabulary?

 

[dmaziuk]

There is hard science proving how people [not] get bent? Please tell me more.

 

[KenGordon]

You really seem stuck on your perspective, you are right, and I am wrong. Tell me more about the "proven by science". Perhaps we're mainly being limited by vocabulary?

Redistribution of decompression stop time from shallow to deep stops increases incidence of decompression sickness in air decompression dives

This compares two profiles. They get the divers out of the water at the same time. One bends three, one bends ten (in 175 ish) If only time/speed counted they would be equally conservative. If you were getting nearly bent on the shallow one (as per the 'listen to your body' school) and changed to the deep one (which has a more 'conservative' first gf number) by the results of this study you would increase the chances of getting bent.

It is all quite complicated and non obvious. Hence being able to choose from any old pair of numbers may lead to unexpected outcomes. Not really for the casual user.

 

[JohnnyC]

There is hard science proving how people [not] get bent? Please tell me more.

I said nothing about hard science proving how not to get bent, however there absolutely IS hard science proving that "slow," and "conservative" are NOT the same thing. Likewise, "fast" and "liberal, or aggressive," are not the same thing. Scubadada seems to want people to believe that we're simply using different words to describe the same thing. That is wrong. As in, not correct. People seem to think that simply because they have an opinion, it is valid. That is not the case. Scubadada's opinion that we are communicating the same concepts by equating slow and conservative, or fast and liberal/aggressive, is not correct.

KenGordon's article proves it, I could repost it, but what's the point? You either understand that calling something "slow" is not the same thing as calling something "conservative," and calling something "fast" is not the same as "liberal" or "aggressive," or you are wrong.

 

[dmaziuk]

KenGordon's article proves it, I could repost it, but what's the point? You either understand that calling something "slow" is not the same thing as calling something "conservative," and calling something "fast" is not the same as "liberal" or "aggressive," or you are wrong.

It doesn't take a PhD to figure out that at a deep stop some of the tissue is off-gassing while some other tissue is on-gassing. If the former outweighs the latter, deep stop is good for you, otherwise the opposite. So you can take a bunch of people down, have them not spend enough time there to reach the "deep stop is good for you" point and get them bent proving that deep stops are bad.

Are you trying to say that spending a long time at deep stop and then bolting to the surface will be "slow" but not "conservative"? Thanks, I couldn't have possibly figured it out for myself so I'll try to memorize it for my next no-deco recreational dive.

 

[Jax]

Too true!

And I agree the Petrel is far from perfect. I have several "improvements" that I would like to see, ranging from more deco options in rec mode to
the dive log continuing count from any manual changes made in the dive count.

The dive log does continue to count from the manual change in the dive count .. . ??? :huh:

---------- Post added January 1st, 2016 at 01:43 PM ----------

Redistribution of decompression stop time from shallow to deep stops increases incidence of decompression sickness in air decompression dives

This compares two profiles. They get the divers out of the water at the same time. One bends three, one bends ten (in 175 ish) If only time/speed counted they would be equally conservative. If you were getting nearly bent on the shallow one (as per the 'listen to your body' school) and changed to the deep one (which has a more 'conservative' first gf number) by the results of this study you would increase the chances of getting bent.

It is all quite complicated and non obvious. Hence being able to choose from any old pair of numbers may lead to unexpected outcomes. Not really for the casual user.

I do not believe this applies.

They determined a Total Stop Time (TST) of 174 minutes. That 174 minutes was simply re-distributed over the water column.

The shallow stops schedule, . . .was prescribed by the, deterministic, gas content, VVAL18 Thalmann Algorithm.

The deep stops schedule, ... was according to the probabilistic BVM(3) bubble model.

It's more like bubbles versus gas content . . . I would like to see the actual schedules and how the stops were distributed, and what the ascent speed was all all points. :huh:

 

[KenGordon]

It doesn't take a PhD to figure out that at a deep stop some of the tissue is off-gassing while some other tissue is on-gassing. If the former outweighs the latter, deep stop is good for you, otherwise the opposite. So you can take a bunch of people down, have them not spend enough time there to reach the "deep stop is good for you" point and get them bent proving that deep stops are bad.

Are you trying to say that spending a long time at deep stop and then bolting to the surface will be "slow" but not "conservative"? Thanks, I couldn't have possibly figured it out for myself so I'll try to memorize it for my next no-deco recreational dive.

Actually it does take a PhD. Several of them in fact. And a navy. And still nobody can tell you when one outweighs the other.

For the second point, no unless you call 112 minutes of stops from 10m to the surface 'bolting' after 30 minutes at 50m.

---------- Post added January 1st, 2016 at 08:50 PM ----------

I would like to see the actual schedules and how the stops were distributed, and what the ascent speed was all all points. :huh:

It is all in the paper. Table 1.

If a child of yours bought a GF based computer, how would you suggest they choose the settings?