3 or 5 minute Safety Stop?

[uncfnp]

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Some outliers will be the exceptions that prove the rule. There will be some fairly big guys with good SACs.

There will be some people who, through good fitness levels & dedicated skill acquisition/refinement, will drive their SAC down and do well with an 80 cf tank.

But at the end of the day, I think that on average big, chunky guys who get no closer to the gym than driving by it occasionally are often either going to dive larger tanks when available, or else plan their profiles around parameters other than a strict 'rule of 3'rds' policy. Assuming excellent conditions, such as Bonaire shore diving or in a quarry.

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Richard.

Richard,

Its true that this is one of the few areas in life where women have been given a physical advantage and that it actually pays to be petite! Through no specific skill set of my own, I always surface with more air than my partner, typically 1000 to his 500 when we both use the same size tank. To even this out, in Bonaire, I use 63s and elsewhere he uses 100's. We have the same number of dives and experience, are of about the same age, fitness level and roughly the same BMI but he is 6 foot male to my 5' 3" female and it will never be "fair" to him!

In my four years of diving, I have seen one buddy group where the woman used a larger tank then her male partner. He was a very experienced diver and she had less than 25 dives.

 

[The Chairman]

Elena seems to surface with more air in her tank than what she started with. The bad part is that she gloats about it.

 

[tracydr]

Listening to people's SAC rates is just funny. Like I'm supposed to be impressed because someone can do an 80 minute dive and still have 1000 psi left.

To quote Popeye, I yam what I yam.

I know my physical weaknesses and I'm working on them. My SAC is what it is and I use that information for my dive planning.

Oh, and FWIW, it's the same .65 you got. So I guess we are in good company.

You're absolutely right. And I have a really hard time believing some people when they brag about things like that that, too, especially larger men.
I've always had a lower SAC rate, though, for some unknown reason. I used to think it was from being smaller. However,I've dived with many women my size who don't seem to find that they have a similar rate. I think its just how some people are. Sure there are some things you can do to improve but at some point you are just what you are.
It's nice, though, because when we dive a resort and use aluminum tanks, I hate AL 80s because they are longer than my spine. I'm much happier with a AL63 and it gives me plenty of air for most warm water rec dives.

---------- Post added July 6th, 2013 at 07:23 PM ----------

Richard,

Its true that this is one of the few areas in life where women have been given a physical advantage and that it actually pays to be petite! Through no specific skill set of my own, I always surface with more air than my partner, typically 1000 to his 500 when we both use the same size tank. To even this out, in Bonaire, I use 63s and elsewhere he uses 100's. We have the same number of dives and experience, are of about the same age, fitness level and roughly the same BMI but he is 6 foot male to my 5' 3" female and it will never be "fair" to him!

In my four years of diving, I have seen one buddy group where the woman used a larger tank then her male partner. He was a very experienced diver and she had less than 25 dives.

My husband and I do the same. Except for with our steel tanks. He really needs to get 100s because I use an HP 80 and he has LP 85s.

---------- Post added July 6th, 2013 at 07:25 PM ----------

Just a funny quick comment on this specifically, and not to derail the thread, but I teach spinning (cycling aerobics) and have for 15yrs now and I'm a short light guy. But I'd love to have your air rate Richard as I suck down better than .8. Its not really that I have lousy aerobic capacity, but its the way I breath when teaching - huge lung fulls at high rates. Trying to re-learn to breath slow and deep is like running up hill backwards on my hands - opposite of my trained normal... Also of similar funny, when the AF had the cycling test as its PT standard, Id fail that too everytime. The fat smokers who walked by the gym on the way to the bar passed with flying colors - no joke. Funny how ironic life can be sometimes.

Now, back to your regularly scheduled program....

Try yoga.

 

[Paulmal]

Just cave fill the Lp85's and they hold just as much air as HP100's.

 

[RJP]

I don't own one, I have an Oceanic, but I have been looking at the Sunnto for its conservatism and the deep stop option. I know most of the newest models (not the Zoop) offer it but don't recall the exact models, D6, D9 and Vyper I believe. They call it the Deep Stop RBGM algorithm. I have been unable to find out how it is incorporated into recreational dives and if it changes the SS.

Google Vytec DS manual - it provides an explanation about how the DS setting works.

 

[beester]

So got to love your profile Richard....I would just rather hit 100ft deep and play around and glide back toward 20ft and still be onboard with 1000psi after an hour...but then..that is just me...

I rather use all available gas.. meaning I don't mind a bit coming up with 20-30 bar (300-400 psi 80 cuft tank). The whole idea from my point of view is to have enough available gas to get you and your buddy/team to the next available gas supply or surface. The gas needed to do so is obviously very depth dependend. So at 4 ata I would need about 1200 barliters reserve to help out a buddy (that's more than have of a filled 80 cuft tank) at 2 ata I would need significantly less. Cudos for being conservative, but conservatism at the right place.

Excuse me for being of topic. On topic, instead of a 5 min stop at 10 or 20 feet you could also do a 1 min stop every 3 feet from 20 feet onwards.

 

[TSandM]

I think you can approach this logically, and the experimental data support what you conclude.

Haldane's math (refined by Buhlmann) basically says that you can spend an indefinite period at 15 feet and surface. This is not true of significantly deeper depths, though.

If you have been deeper than that, then any time you spend at 15 feet is offgassing nitrogen you absorbed when you were deeper. Any nitrogen you get rid of at 15 feet is not available to cause problems when you surface. Therefore, I think you could say in theory that it would be quite nice to spend enough time at 15 feet to equilibrate all your compartments to where they would be at 15 feet if you had never been deeper. In other words, the longer the 15 foot stop, the better.

Frank has a lovely point, which is that, if you are warm and comfortable and there is anything to look at (even if it's only your dive buddies and the SMB line) why NOT prolong your dive and hang out. This, of course, assumes you have enough gas to do it, which you should have, if you have been using the rock bottom concept for planning, and that there is no other pressing reason to surface.

On some of my dives, we are having so much fun in the shallows we don't WANT to surface. I did twenty minutes of unasked-for deco on a dive in the Red Sea, because we were on a gorgeous wall, covered in spectacular corals, and full of sunlight, and we just decided that rather than surface and board the RIB, we would swim back to the boat. Presto -- 25 minutes of deco at 20 feet! We were only the better for it.

My personal ascent strategies match what most deco software will offer, if you use gradient factors or a bubble model. I hurry up from depth, and dawdle in the shallows. One of the most respected posters on SB when I came here was a man named Uncle Pug, and his guideline was to spend as much time above 30 feet as he spent below 60, and I would say most of my profiles match that.

Gas urgencies and thermal challenges can limit the time you can spend shallow -- not to mention the problems that come with a dry suit without a p-valve. But all other things being equal, I think there are both theoretical reasons and some experimental support for spending as much time in the top 2 ATA as you can safely do.

 

[Abdullah]

This nails it for me from Alert Diver | Deep Stops :

These quotes from the article nail it for me:

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

Mitchell: No. There is insufficient data to justify a deep stop approach in recreational, no-decompression diving. Divers should, however, pay careful attention to ascent rates, and the imposition of shallow safety stops is still considered beneficial.

Gutvik: No. The recommended safety stop and a controlled, slow ascent rate are adequate for performing safe no-decompression dives. These dives will normally be either too shallow to consider deeper stop depths or too short for the deep stops to have an effect.

Doolette: Recreational diving within no-decompression limits conducted with a shallow safety stop has a good safety record. There is insufficient evidence to suggest a deep stop offers any advantage.

What does it take to compare the safety of two or more decompression procedures?

Doolette: Comparing, for instance, a "deep-stops" schedule and a "traditional" shallow-stops schedule requires that each schedule be dived many times by many divers with everything else kept about the same, with a predetermined end point such as DCS or perhaps venous gas emboli (VGE) scores. For instance, the U.S. Navy Experimental Diving Unit conducted almost 400 air dives to 170 fsw for 30 minutes of bottom time with the same decompression time. Half the dives followed a deep-stops schedule, and half followed a traditional shallow-stops schedule. There was more DCS following the deep-stops schedule than the traditional schedule. ...

 

[The Chairman]

Doolette: Comparing, for instance, a "deep-stops" schedule and a "traditional" shallow-stops schedule requires that each schedule be dived many times by many divers with everything else kept about the same, with a predetermined end point such as DCS or perhaps venous gas emboli (VGE) scores. For instance, the U.S. Navy Experimental Diving Unit conducted almost 400 air dives to 170 fsw for 30 minutes of bottom time with the same decompression time. Half the dives followed a deep-stops schedule, and half followed a traditional shallow-stops schedule. There was more DCS following the deep-stops schedule than the traditional schedule. ...

That would be a decompression dive and I would be following the deco schedule presented by my PDC, adding an additional safety stop at the end, gas permitting. I wonder if those were type I or II hits? Deco diving usually presents a higher incidence of type I hits. In this thread, we are discussing NDL diving, which is far, far different. How many "undeserved hits" from NDL divers were type 1? How many "undeserved hits" from NDL divers were type II? According to DAN, they are almost all type II. If getting DCS is just a little more than statistical noise, then getting type I DCS for the recreational diver is really rare. Consequently, I'm going to dive in a manner that minimizes type II DCS even further. That for me means a two minute deep stop and a full five minute safety stop. I feel far better when I do this and that anecdotal evidence is enough for me.

 

[BDSC]

These quotes from the article nail it for me:

A few months ago I was at the DAN headquarters in Durham, NC and asked Neal Pollock, who is the Research Director at DAN, his thoughts on Deep Stops. He felt it would be far better to add that extra minute to your accent time than do a deep stop for a minute.