average depth and tables?

[SailNaked]

well a little off topic however there is a rule, that if there are points that do not support your theory then your theory is wrong. (paraphrase).

Dive theory is wrong, we know that. We accept that and we use it anyway. To argue that something violates the theory and as such is dangerous is well fuzzy.

we use a fuzzy algorithm and we get approximate results, I am just asking if taking the average depth from a computer as the depth of a previous dive and deriving a pressure group would be significantly outside the bounds of safety and why.

I will have to obviously take some dives and see what it gives and then see if the plan on the computer agrees or disagrees significantly.

Seems the ratio deco and averaging guys have not all died so likely outcome is it will mostly work fine, about as well as the tables do on their own.

Unless of course someone as a statistic on the mortality of the averaging dudes.

 

[Thalassamania]

In my view most of what has kept the RD guys intact is their approach or using "fudge factors" that make baseball pitchers' superstitions appear quite rational by comparison.

 

[Hatul]

You're trying to get extra dive time out of tables and as TSandM pointed out violating the rules of the model. You remind me of the dive guide who used his dive computer with 24% O2 setting while diving with air to increase his bottom time.

Adam

 

[Thalassamania]

You're trying to get extra dive time out of tables and as TSandM pointed out violating the rules of the model. You remind me of the dive guide who used his dive computer with 24% O2 setting while diving with air to increase his bottom time.

Adam

At least that's a systematic approach, all it does is increase the odds of DCS; and, let's face it, some people are harder to bend than are others. RD on the other hand faces you with potential of "potholes" that you have no idea are there, just waiting for you to fall into.

 

[Rainer]

LOL, have you actually seen RD profiles? They aren't exactly "way out of the norm". Ditto the average depth recreational profiles that DIR divers are doing (i.e. they're generally more conservative than what people are doing on their computers). This all *does* take some knowledge about how to generate multi-level profiles and use average depth responsibly. Clearly you don't understand the method. That's ok; learning this stuff on the interwebs can be a bitch.

In my view most of what has kept the RD guys intact is their approach or using "fudge factors" that make baseball pitchers' superstitions appear quite rational by comparison.

 

[atedeschi]

Like it has been stated it's all theory and not proven law. Perfect example about 2 months ago I was diving and a group of three were all diving in a class with same gases times and same profiles plus or minus maybe a foot. The all ascended together and followed same cut tables and one of the three got bent.

To the op I just cut some tables to give you an example just have to find what I did with them and I'll post it.

 

[Thalassamania]

LOL, have you actually seen RD profiles? They aren't exactly "way out of the norm". Ditto the average depth recreational profiles that DIR divers are doing (i.e. they're generally more conservative than what people are doing on their computers). This all *does* take some knowledge about how to generate multi-level profiles and use average depth responsibly. Clearly you don't understand the method. That's ok; learning this stuff on the interwebs can be a bitch.

I'd guess that I know far more about RD and have had far more one-on-one discussion with real decompression physiologists concerning how RD works and doesn't work than you can possible imagine.

The fact is that RD is nothing more than an attempt to fit an approach to a model that was not developed for that purpose. Do you dive "raw" RD repetitive profiles right up to the edge of no-D and then make a direct controlled ascent to the surface? Of course you don't ... you're not that stupid, so stop assuming that others are.

 

[Rainer]

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

I'd guess that I know far more about RD and have had far more one-on-one discussion with real decompression physiologists concerning how RD works and doesn't work than you can possible imagine.

The fact is that RD is nothing more than an attempt to fit an approach to a model that was not developed for that purpose. Do you dive "raw" RD repetitive profiles right up to the edge of no-D and then make a direct controlled ascent to the surface? Of course you don't ... you're not that stupid, so stop assuming that others are.

 

[Mr Carcharodon]

I will have to obviously take some dives and see what it gives and then see if the plan on the computer agrees or disagrees significantly.

s.

That is the right approach. Take some dives and compare the ascents in v-planner, deco planner, ratio deco etc and see how different they are, and how they compare to tables. Change the conservatism parameters, and the gradient factors and see what happens. See where averages work what screws things up.

Tables are set up in part to keep it simple enough to get it all on one card, not because they are scripture written in stone. Almost everyone today dives a computer that does not assume a square profile and it does not appear their DCS risk is significantly differnet than those using tables. The ratio deco folks seem to being doing OK too.

By the way UTD does have an online ratio deco course. I do not have firsthand knowledge about the online course. Maybe someone else here does.

 

[atedeschi]

If I understand the OP question you want to take the average depth after the dive and use that as your actual dive depth and plan your next dive. This is not correct and will get you hurt for sure, because the computer accounts your asecent and deco or safety stop.

What I am doing is doing my dive (these are deco or CC dives not recreation dives) and bring a range of tables say for a 200' dive, I would have tables for 200' - 160'. Once on the dive I do my thing and before my ascent look at my BT which does on the fly average depth. Say it comes to 173', then I would use 180' tables for the BT i was down.

Here are some examples of multilevel tables vs average depth.

Typical Cave Dive at Ginnie

Multilevel Tables

Conservatism = Nominal

Dec to	80ft		(1)	Nitrox 32	50ft/min descent.
Level	80ft	 13:24	(15)	Nitrox 32	1.09  ppO2,  64ft ead
Dec to	90ft		(15)	Nitrox 32	50ft/min descent.
Level	90ft	 19:48	(35)	Nitrox 32	1.19  ppO2,  73ft ead
Dec to	100ft		(35)	Nitrox 32	50ft/min descent.
Level	100ft	 29:48	(65)	Nitrox 32	1.29  ppO2,  81ft ead
Asc to	90ft		(65)	Nitrox 32	-30ft/min ascent.
Level	90ft	 15:00	(80)	Nitrox 32	1.19  ppO2,  73ft ead
Asc to	80ft		(80)	Nitrox 32	-30ft/min ascent.
Level	80ft	 10:00	(90)	Nitrox 32	1.09  ppO2,  64ft ead
Asc to	20ft		(92)	Nitrox 32	-30ft/min ascent.
Stop at	20ft	  1:20	(94)	Oxygen	1.60  ppO2,  0ft ead
Stop at	15ft	 12:00	(106)	Oxygen	1.45  ppO2,  0ft ead
Surface			(106)	Oxygen	-30ft/min ascent.

Average Depth Table

Conservatism = Nominal

Dec to	90ft		(1)	Nitrox 32	50ft/min descent.
Level	90ft	 88:12	(90)	Nitrox 32	1.19  ppO2,  73ft ead
Asc to	20ft		(92)	Nitrox 32	-30ft/min ascent.
Stop at	20ft	  0:40	(93)	Oxygen	1.60  ppO2,  0ft ead
Stop at	15ft	 11:00	(104)	Oxygen	1.45  ppO2,  0ft ead
Surface			(104)	Oxygen	-30ft/min ascent.

The runtime difference is two minutes which gets covered in my safety stop anyway plus 2 minutes is nothing in deco, you get more then that on different computers or deco programs. Also to be far the average is actuall 91' so you could also round up but since I said 90', I would do a 5min SS on O2 just to be clear.

Here is a typical Ocean Dive

Conservatism = Nominal

Dec to	200ft		(4)	Triox 21/20	50ft/min descent.
Level	200ft	  6:00	(10)	Triox 21/20	1.48  ppO2,  141ft ead,  153ft end
Asc to	180ft		(10)	Triox 21/20	-30ft/min ascent.
Level	180ft	 20:00	(30)	Triox 21/20	1.35  ppO2,  126ft ead,  137ft end
Asc to	160ft		(31)	Triox 21/20	-30ft/min ascent.
Level	160ft	 10:00	(41)	Triox 21/20	1.23  ppO2,  111ft ead,  121ft end
Asc to	90ft		(43)	Triox 21/20	-30ft/min ascent.
Stop at	90ft	  0:20	(44)	Triox 21/20	0.78  ppO2,  59ft ead,  65ft end
Stop at	80ft	  2:00	(46)	Triox 21/20	0.72  ppO2,  51ft ead,  57ft end
Stop at	70ft	  2:00	(48)	Nitrox 50	1.56  ppO2,  32ft ead
Stop at	60ft	  2:00	(50)	Nitrox 50	1.41  ppO2,  26ft ead
Stop at	50ft	  3:00	(53)	Nitrox 50	1.26  ppO2,  20ft ead
Stop at	40ft	  5:00	(58)	Nitrox 50	1.10  ppO2,  13ft ead
Stop at	30ft	  6:00	(64)	Nitrox 50	0.95  ppO2,  7ft ead
Stop at	20ft	  4:00	(68)	Oxygen	1.60  ppO2,  0ft ead
Stop at	15ft	 15:00	(83)	Oxygen	1.45  ppO2,  0ft ead
Surface			(83)	Oxygen	-30ft/min ascent.

Average Depth Table of 180'

Conservatism = Nominal

Dec to	180ft		(3)	Triox 21/20	50ft/min descent.
Level	180ft	 36:24	(40)	Triox 21/20	1.35  ppO2,  126ft ead,  137ft end
Asc to	110ft		(42)	Triox 21/20	-30ft/min ascent.
Stop at	110ft	  0:40	(43)	Triox 21/20	0.91  ppO2,  74ft ead,  81ft end
Stop at	100ft	  1:00	(44)	Triox 21/20	0.85  ppO2,  66ft ead,  73ft end
Stop at	90ft	  1:00	(45)	Triox 21/20	0.78  ppO2,  59ft ead,  65ft end
Stop at	80ft	  3:00	(48)	Triox 21/20	0.72  ppO2,  51ft ead,  57ft end
Stop at	70ft	  2:00	(50)	Nitrox 50	1.56  ppO2,  32ft ead
Stop at	60ft	  3:00	(53)	Nitrox 50	1.41  ppO2,  26ft ead
Stop at	50ft	  3:00	(56)	Nitrox 50	1.26  ppO2,  20ft ead
Stop at	40ft	  5:00	(61)	Nitrox 50	1.10  ppO2,  13ft ead
Stop at	30ft	  7:00	(68)	Nitrox 50	0.95  ppO2,  7ft ead
Stop at	20ft	  4:00	(72)	Oxygen	1.60  ppO2,  0ft ead
Stop at	15ft	 18:00	(90)	Oxygen	1.45  ppO2,  0ft ead
Surface			(90)	Oxygen	-30ft/min ascent.

So in this dive its actually more conservative then the multi level plan.