average depth and tables?

[atedeschi]

I also have the info someone sent me after they took the ratio deco course but ratio deco is not the same as average depth. It has its own whole set of rules and parameters. It was interesting though to read and learn about, but to much math to do while diving and its easier to plug in a range of depths and times, laminate and take them with me.

 

[Thalassamania]

Yawn. I'm not the one fear-mongering about loss of sexual function for what are utterly benign dives. You're a riot.

And you're quite dangerous. You are advising people to use a technique that, to the best of my knowledge, no reputable diving physiologist recommends, a technique that has no theoretical basis, a technique that is essentially nothing more than a curve fitting exercise. The FIRST thing that you learn about regressions and curve fits is that they are approximations and that should never be used outside of their data set, that's high school statistics. So since you know that the approximation is not really worth while you pile on any number of subject (and some people, even mystical) fudge factors, without any rhyme or reason save, "it feels right." There are areas of decompression where I am willing, based on experience developed from models with a physiological and physical basis, to walk much closer to the line than many (e.g., rather aggressive oxygen deco and time to fly) and there are areas that I find too problematical to be useful, such as RD. You're a hazard, and if you want to be a hazard to yourself, knock yourself out ... but don't lead others down that path without an honest explanation of where they're going: to something that seems to work, but that relies more on fudge than on theory or testing.

 

[Mr Carcharodon]

And yet he and many other routinely do RD dives and come out OK. Reality is just so inconvenient.

 

[Rainer]

An even bigger yawn. Where have I advised anyone to do anything in this thread? I have pointed out that RD is not something to "fear".

Please post a RD profile (assuming you know how to generate one; I sort of doubt it) and then please show where it's dangerous or sits outside known *theoretical* models (sorry, none of them are completely validated). Every RD profile I've ever dived had me clean under DecoPlanner or V-Planner (i.e. Buhlmann + accepted GFs or VPM).

Your harping on "fudge" factors is also silly. What do you think is actually being taught other than "back away from profiles that didn't sit well with you"? What agency is NOT teaching this obviously SANE practice?

And you're quite dangerous. You are advising people to use a technique that, to the best of my knowledge, no reputable diving physiologist recommends, a technique that has no theoretical basis, a technique that is essentially nothing more than a curve fitting exercise. The FIRST thing that you learn about regressions and curve fits is that they are approximations and that should never be used outside of their data set, that's high school statistics. So since you know that the approximation is not really worth while you pile on any number of subject (and some people, even mystical) fudge factors, without any rhyme or reason save, "it feels right." There are areas of decompression where I am willing, based on experience developed from models with a physiological and physical basis, to walk much closer to the line than many (e.g., rather aggressive oxygen deco and time to fly) and there are areas that I find too problematical to be useful, such as RD. You're a hazard, and if you want to be a hazard to yourself, knock yourself out ... but don't lead others down that path without an honest explanation of where they're going: to something that seems to work, but that relies more on fudge than on theory or testing.

 

[Thalassamania]

And yet he and many other routinely do RD dives and come out OK. Reality is just so inconvenient.

Read what I wrote: it is a pretty good curve fit. I'm not denying that it can work, especially when fudged by the phase of the moon and your grandmother's age, almost any moderately conservative set of equations (or for that matter set of numbers) would yield similar results. Without an underpinning in basic physiology and modeling it's not a unified approach that can be trusted to be extrapolated and so it should not be represented as anything other than a math tick, every new time/depth pair is a crap shoot of unknown odds.

An even bigger yawn. Where have I advised anyone to do anything in this thread? I have pointed out that RD is not something to "fear".

Please post a RD profile (assuming you know how to generate one; I sort of doubt it) and then please show where it's dangerous or sits outside known *theoretical* models (sorry, none of them are completely validated). Every RD profile I've ever dived had me clean under DecoPlanner or V-Planner (i.e. Buhlmann + accepted GFs or VPM).

Your harping on "fudge" factors is also silly. What do you think is actually being taught other than "back away from profiles that didn't sit well with you"? What agency is NOT teaching this obviously SANE practice?

That's exactly the point, what is being taught is "back away from profiles that didn't sit well with you," that's kinda ex-post-facto. And checking your RD dive, that you did in your head in real time, against a program later is kinda closing the barn door after the horse is gone. I'm glad that you have suffered no ill effects from this to date, it my fervent hope that your good luck continues, but lord only knows what the long term effects of repeated sub-clinical DCS may be (we do have some idea, e.g., dysbaric osteonecrosis, which does not show up for a long time).

I guess my real problem is that RD is a classic example of applying engineering thinking to a biological problem. It almost always yields a good first or second order approximation that has unexpected holes in it, just ask any engineer if a bumble bee can fly.

 

[Rainer]

Again, since you're the RD expert, please post a RD profile and show how it is less conservative than "more established" tables others are diving. Seriously, post away.

I'm getting out of the water cleaner than what VPM or B+GF profiles would have me doing (i.e. RD calls for *more* deco than the other tables in the depth ranges I'm diving). Our group tends not to be the ones sleeping on the boat ride back, so I'm not really too worried about any sub-clinical DCS.

Still have no idea what fudge factors you're talking about. I don't apply any "fudges" to my "vanilla RD" profiles. Neither do any of my teammates. If I found profiles that weren't sitting well with me, I'd modify them. That's not something specific to RD. Anyone should back away from profiles that prove too aggressive for their particular physiology. To do otherwise is asinine.

We'll keep awaiting that RD profile example that's so scary. Feel free to offer it up anytime.

Read what I wrote: it is a pretty good curve fit. I'm not denying that it can work, especially when fudged by the phase of the moon and your grandmother's age, almost any moderately conservative set of equations (or for that matter set of numbers) would yield similar results. Without an underpinning in basic physiology and modeling it's not a unified approach that can be trusted to be extrapolated and so it should not be represented as anything other than a math tick, every new time/depth pair is a crap shoot of unknown odds.

That's exactly the point, what is being taught is "back away from profiles that didn't sit well with you," that's kinda ex-post-facto. And checking your RD dive, that you did in your head in real time, against a program later is kinda closing the barn door after the horse is gone. I'm glad that you have suffered no ill effects from this to date, it my fervent hope that your good luck continues, but lord only knows what the long term effects of repeated sub-clinical DCS may be (we do have some idea, e.g., dysbaric osteonecrosis, which does not show up for a long time).

I guess my real problem is that RD is a classic example of applying engineering thinking to a biological problem. It almost always yields a good first or second order approximation that has unexpected holes in it, just ask any engineer if a bumble bee can fly.

 

[gcbryan]

Is there a profession of "diving physiologist" and is it part of their profession to recommend theories?

Fitting lines to curves and not being used outside of their data sets...isn't that what RD does?

I think it's helpful to lighten up and have a sense of humor with some of the issue on here. I actually agree with some of your points but I don't think the alternatives are as grim as you are making them out to be.

Sure, it's grim when those things happen but that's not the same as saying that they do and will happen with RD as opposed to happening (insert statistic) to divers as a group.

I don't use RD but I don't think it's voodoo anymore than everything else is voodoo. It's not a theory and is just shorthand for applying existing theories which are voodoo to a degree anyway because ...they are theories!

 

[atedeschi]

Plus ratio deco is not the same as depth averageing and using programs like vplanner or something similar and that is wat the op was asking about.

On a rd note I took a good look at it and compared profiles against vplanner. What I found is for the depth ranges it was sometimes more conservative and sometimes more agressive but I dnt recall it being to extreme. It does work for me for two reasons: I dnt use there standard gases and I dnt want to calculate it on the fly in the water.

 

[acwest]

can you use the average depth from your computer to log dives with tables.

Lets not get into why I want to do this because it is not really relavant.

Would you consider this safe enough to use to make a subsequent table dive?

Why you want to do it could be quite relevant. If the goal is just to transition from a computer dive to a table dive, one of the better methods I have seen is to check what NDL the computer is giving for various depths after your first dive, and compare that with your tables. You should be able to work out what pressure group you are in, and use that for subsequent table dives. The problem with using an average depth is that Nitrogen loading isn't linear with depth. If it was, tables and computers would both be a lot simpler. The order you do the depths matters too. If you don't believe that, you could do your deco stops at the beginning of the dive instead of the end... I really wouldn't recommend that as an experiment, unless you have some goats or Navy ratings to try it out on.

 

[LiteHedded]

to me, bottom time matters a lot more than depth for the most part. I don't stress out about my averages too much. a few feet this way or that. doesn't bother me at all.