deep stops or not

[lowviz]

As I indicated in one of my posts on decompression theory a while ago, in my opinion there is no clear formula on how to determine OGCs, but they seem to me rather empirical constructs determined by trial and error and experience. ...//...

Well finally a solid answer!

...//... Basically, the question is: how much overpressure gradient (by compartment) are you willing to accept? 2 ATM for the fastest compartment? ...//...

I'm sticking with Workman's 1.58


THANKS!!!

---------- Post added February 1st, 2014 at 06:26 PM ----------

Trying to keep this in scope for "Basic Scuba Discussions". This is a decent read for the most interested: http://www.diverclub.ru/File/literatur/understanding_m-values.pdf

Just lightly skimming the article will offer many "hand waving" insights.

---------- Post added February 2nd, 2014 at 01:44 AM ----------

-might just as well give the rest of it. If I have to guess, I only do one deep stop, 2 minutes at this depth:

OGC = 0.69(Max Depth) - 8. Gives the OGC stop in feet.

YMMV...

---------- Post added February 2nd, 2014 at 02:06 AM ----------

And finally, ascent rate varies: http://www.scubaboard.com/forums/co...ascent-rate-speed-comparison.html#post1979863

 

[Ricky B]

That's not entirely true. They each say different things.

Yes, but they add up to the same conclusion, at least in the context of this thread.

Should recreational divers staying within no-decompression limits be concerned about deep stops?

Mitchell and Gutvik say No. Southerland says, "Recreational divers should be aware of the issue. If sufficient evidence becomes available, then a diver might be better off just upgrading the dive computer with a newer algorithm." This means to me "No until there is more data." Bennett says, "There is no more reason for concern about deep stops than for the widely accepted shallow safety stop." What Bennett says could be construed to endorse deep stops and maybe that rec divers should do deep stops.

But earlier in the discussion, in response to the question Is it advisable for divers to insert additional deep stops regardless of what their dive computers suggest? Bennett said, "If divers have computers with a deep-stop option, they can use it. If the computers do not have a deep-stop option, they should stick to the computers' readout." All the other answers agreed that divers should not insert additional deep stops on their own.

So while the jury is still out on whether deep stops are helpful or not, there is consensus that a rec diver should not insert a deep stop that is not called for by the dive computer.

Mitchell says, "If divers find the concept of deep stops appealing, they should choose an algorithm into which [deep stops] have been incorporated." Seems like common sense.

 

[dmainou]

Btw guys, I'll point out that NOW there is some hard data on deep stops and it is not very flattering to them.

I've posted before the links to other forum where the discussion is taking place.

People from the US Navy have kindly devoted some time to explain why they created the study the way they did, what is the meaning of the outputs and why this matters to recreational dives.

Simon Mitchell, a leading hyperbaric physician had spent much time debating with the salesman of a popular deep stop software.

The long story short is that deep stops are a nice hypothesis popularised by the internet that until recently no one had actually tested it's validity.

The jury is out you just need to read the writing in the wall. The scientists do agree that more research is required in the sense that better profiles can be produced and that the ideal profile may be somewhat in between but again that is just a hypothesis. At present we know that shallow stops are better than current deep stop profiles.

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[Ayisha]

...Bennett says, "There is no more reason for concern about deep stops than for the widely accepted shallow safety stop." What Bennett says could be construed to endorse deep stops and maybe that rec divers should do deep stops.

But earlier in the discussion, in response to the question Is it advisable for divers to insert additional deep stops regardless of what their dive computers suggest? Bennett said, "If divers have computers with a deep-stop option, they can use it. If the computers do not have a deep-stop option, they should stick to the computers' readout." All the other answers agreed that divers should not insert additional deep stops on their own...

In the context of "stick(ing) to the computer's readout", let's say you get to 50 feet and you have "10 safe minutes" left according to the computer. What would be the harm in staying at that depth for 1 minute and calling it a deep stop?

My computer (Sherwood Wisdom) constantly recalculates my safe minutes remaining throughout the dive. I don't ride the computer or go very close to the NDL's, so I see no harm and no difference between a deep stop and if you chose to swim along for a while looking in some holds at 50 feet ie) a multi-level dive. In articles about Deep Stops years ago, DAN used to say, "Beat the Bubble, rather than Treat the Bubble".

 

[tursiops]

I'm sticking with Workman's 1.58

You do realize, don't you, that DiveNav's 2.0 ATM and Workman's 1.58 ATM are the same, since the former is talking about the total pressure difference and Workman is talking about about the pressure difference on just the Nitrogen fraction of air? (2x0.79 = 1.58)

 

[lowviz]

You do realize, don't you, that DiveNav's 2.0 ATM and Workman's 1.58 ATM are the same, since the former is talking about the total pressure difference and Workman is talking about about the pressure difference on just the Nitrogen fraction of air? (2x0.79 = 1.58)

We both know that it wasn't DiveNav, it was Haldane. Keep in mind this is all just for understanding and using the nitrogen fraction aids in (my) understanding. The profound lack of comprehension of decompression theory in all but a very few individuals clearly signals that changing one's ascent profile because it seems like a good idea, is most likely, a bad idea. The only way I alter my ascent profile is to add conservatism if I feel that it is warranted on that day.

My DC inserts deep stop(s) as part of the ascent profile it provides. I have found ways to fairly accurately estimate what my DC will offer as an ascent profile. This is my fallback if the DC cuts out on me, nothing more.

 

[SADS 669]

In the context of "stick(ing) to the computer's readout", let's say you get to 50 feet and you have "10 safe minutes" left according to the computer. What would be the harm in staying at that depth for 1 minute and calling it a deep stop?

My computer (Sherwood Wisdom) constantly recalculates my safe minutes remaining throughout the dive. I don't ride the computer or go very close to the NDL's, so I see no harm and no difference between a deep stop and if you chose to swim along for a while looking in some holds at 50 feet ie) a multi-level dive. In articles about Deep Stops years ago, DAN used to say, "Beat the Bubble, rather than Treat the Bubble".

Good common sense post, I like it.........it also slows an ascent which is always good

 

[DiveNav]

You do realize, don't you, that DiveNav's 2.0 ATM and Workman's 1.58 ATM are the same, since the former is talking about the total pressure difference and Workman is talking about about the pressure difference on just the Nitrogen fraction of air? (2x0.79 = 1.58)

Actually I was referring to the delta pressure in a given compartment loaded with inert gasses resulting from a diver ascending from point A to point B.
In the example shown in the image below, inert gasses are a mix of Nitrogen and Helium (and you can actually see what happens to the OGC curves when the diver switches to a different gas during ascent).

​

 

[100days-a-year]

Still ALL just theory,as given the inability to accurately predict an individuals actual intake and offgas of inert gasses we are left with algorithms that extrapolate it based on a less than 1 millionth of of the total population sample size.Granted empirical evidence is compelling but is not fact.Given that the decompression theory koolaid of the day changes every few years I listen to the guys actually diving these whack newfangled ideas and incoporate them as I can.

FWIW I am not a recreational diver very often but I did read a post on DecoStop once in band camp.

 

[dmainou]

Yeah, it's just that the tide has changed again and more they are saying that the way we were going before seems to have gone too far.

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