UTD Decompression profile study results published

[lowflyer]

I guess reading the actual paper would provide some answers.

Would love to, but I don't get this journal. Don't think a link to the article itself is available, but maybe you have one?

 

[Kevrumbo]

Maybe I'm wrong. Explain how RD, which as far as I know hasn't changed in the last 15 or 20 years, somehow magically mimics Buhlmann with some kind of gradient factors now when it never has before.

Would you care to explain the process by which the bubble approach has been "let go" and RD now approximates Buhlmann?.... because I'm not seeing it.

I could be wrong about this (and I sincerely hope that I am to be perfectly honest) but I would like to see incontrovertible proof that I am wrong. How do you adjust RD to accommodate "your algorithm of choice"?

R.

GUE Ratio Deco, and UTD Ratio Deco without any Deepstops or S-curve shaping:

@50m for 25min bottom time on 18/45 standard gas and two deco gases Eanx50 and O2, GUE has 15min with 50% and 15min with 100% O2, while UTD has 17.5min on 50% and 17.5min on 100% O2 -or nearly the same Eanx50 and O2 time schedules for both versions of Ratio Deco.

Depth: GUE: UTD:
21m, 3min, 3.5min [Eanx50]
18m, 3min, 3.5min;
15m, 3min, 3.5min;
12m, 3min, 3.5min;
9m, 3min, 3.5min;
6m, 15min, 17.5min [Oxygen]
Or optionally:
6m, 9min, 11.5min [Oxygen]
---->, 6min, 6min [---> a surfacing ascent rate from 6m at 1 meter per minute].

Now compare the above with a generated Buhlmann GF 50/80 for the same bottom profile and let's see how it looks. .

 

[tursiops]

Would love to, but I don't get this journal. Don't think a link to the article itself is available, but maybe you have one?

No, sadly, I'd like to read it too! We join the society, or wait a year. Imagine how much off-base speculation there is going to be over the next 12 months!

 

[Diver0001]

GUE Ratio Deco, and UTD Ratio Deco without any Deepstops or S-curve shaping:

@50m for 25min bottom time on 18/45 standard gas and two deco gases Eanx50 and O2, GUE has 15min with 50% and 15min with 100% O2, while UTD has 17.5min on 50% and 17.5min on 100% O2 -or nearly the same Eanx50 and O2 time schedules for both versions of Ratio Deco.

Depth: GUE: UTD:
21m, 3min, 3.5min [Eanx50]
18m, 3min, 3.5min;
15m, 3min, 3.5min;
12m, 3min, 3.5min;
9m, 3min, 3.5min;
6m, 15min, 17.5min [Oxygen]
Or optionally:
6m, 9min, 11.5min [Oxygen]
---->, 6min, 6min [---> a surfacing ascent rate from 6m at 1 meter per minute].

Now compare the above with a generated Buhlmann GF 50/80 for the same bottom profile and let's see how it looks. .

Kevin I'm not quite sure what you are trying to show me but that is a 1m per min ascent ( or less depending on how you read this). Isn't that exactly (1m/min) that got you bent while trying to learn how RD worked?

I'm not trying to be obnoxious. Just trying to get on the same page as your message here....

R..

 

[Remy B.]

GUE Ratio Deco, and UTD Ratio Deco without any Deepstops or S-curve shaping:

@50m for 25min bottom time on 18/45 standard gas and two deco gases Eanx50 and O2, GUE has 15min with 50% and 15min with 100% O2, while UTD has 17.5min on 50% and 17.5min on 100% O2 -or nearly the same Eanx50 and O2 time schedules for both versions of Ratio Deco.

Depth: GUE: UTD:
21m, 3min, 3.5min [Eanx50]
18m, 3min, 3.5min;
15m, 3min, 3.5min;
12m, 3min, 3.5min;
9m, 3min, 3.5min;
6m, 15min, 17.5min [Oxygen]
Or optionally:
6m, 9min, 11.5min [Oxygen]
---->, 6min, 6min [---> a surfacing ascent rate from 6m at 1 meter per minute].

Now compare the above with a generated Buhlmann GF 50/80 for the same bottom profile and let's see how it looks. .

Dec to 50m (2) Trimix 18/45 18m/min descent.
Level 50m 22:13 (25) Trimix 18/45 1.07 ppO2, 18m ead, 23m end

Stop at 24m 0:45 (29) Trimix 18/45 0.61 ppO2, 6m ead, 9m end
Stop at 21m 2:00 (31) Nitrox 50 1.54 ppO2, 10m ead
Stop at 18m 1:00 (32) Nitrox 50 1.39 ppO2, 8m ead
Stop at 15m 1:00 (33) Nitrox 50 1.24 ppO2, 6m ead
Stop at 12m 3:00 (36) Nitrox 50 1.10 ppO2, 4m ead
Stop at 9m 5:00 (41) Nitrox 50 0.95 ppO2, 2m ead
Stop at 6m 17:00 (58) Oxygen 1.60 ppO2, 0m ead
Surface (59) Oxygen -6m/min ascent.

OTU's this dive: 77
CNS Total: 46.3%

I know it was mention about similarities and not equals, but I will prefer to spent 5min at 9m and less time deeper, It is more efficient in my vague knowledge as well that you will need less gas, dismal but in longer dives it may be beneficial.

 

[huwporter]

Maybe I'm wrong. Explain how RD, which as far as I know hasn't changed in the last 15 or 20 years, somehow magically mimics Buhlmann with some kind of gradient factors now when it never has before.

You keep on saying this, but: A) GUE literally in the last couple of months released updated ascent SOPs with greatly reduced deep stops. This is following another similar change a couple of years ago also reducing deep stops. B) in my group we regularly discuss reducing deep stops further than the SOPs go.

Despite it being explained several times already even in this thread, there is still confusion about the fact that there are two very different things being referred to as RD.

Type X: UTD Ratio Deco(TM) = a set of rigid rules, dictated by AG, defining exactly how to do deco.

Type Y: ratio deco = a methodology (not rules) for starting with your algorithm of choice and adjusting it slightly to make a result that is really easy to remember.

Using type Y, you can find ratios for whatever starting profiles you want. Buhlmann 100/100? Sure, no problem.

I use type Y all the time. I've never used type X. Dont confuse UTD Ratio Deco(TM) with ratio deco.

 

[Kevrumbo]

Kevin I'm not quite sure what you are trying to show me but that is a 1m per min ascent ( or less depending on how you read this). Isn't that exactly (1m/min) that got you bent while trying to learn how RD worked?

I'm not trying to be obnoxious. Just trying to get on the same page as your message here....

R..

No . . .Diver0001 how did you hear or understand that a slow 1 meter per minute final ascent rate to the surface on Oxygen after a proper O2 deco profile at 6 meters causes DCS?

 

[Kevrumbo]

So what is the issue to strap on a DC and a slate and follow GF, and leave RD in your mind in case your 1st DC and/or 2nd and your buddy's DC fail and both lose the slates ?

I suppose that's fine until you move to another site where the depth changes. Now your slate is worthless.

With RD I can cook up a plan on the boat in the event of a change.

So you are not diving your plan, and you dive without a contingency plan ?

How to derive a contingency deco plan range for dive site profile depth changes using Ratio Deco given the standard mixes of 21/35 for bottom and Eanx50 for deco:

At a setpoint 150'/45m for Ratio Deco 1:1 Schedule, my one 40cf/5.5L Deco Bottle of 50% can safely cover a total deco profile time of 20 minutes for my particular deco Depth Consumption Rate. So my pre-dive "insta-profile" depth & bottom time choices, using RD rules (i.e. adding 5min deco for every 10'/3m you go over the setpoint of 150'/45m, and subtracting 5min for every 10'/3m interval less than the setpoint), calculated out like this:

130'/39m for 30min;
140'/42m for 25min;
150'/45m for 20min [RD 1:1 setpoint]
160'/48m for 15min
170'/51m for 10min.

(Choose one of the above for a square profile at the particular depth of interest, or stay around the average depths of the RD 1:1 setpoint).

The point is the total time on Nitrox 50% is the same (20min) whichever depth and corresponding bottom time you choose above. The deco stop times in minutes starting at 70'/21m with 10'/3m interval stop depths ascending to the surface has a progression like this: 2,2,2,2,2,10 and finally slow 1m/min (3'/min) ascent to surface.

Alternatively, this is one simple and easy back-up deco profile range for the novice tech diver's wet notes, if the tech computer craps out and all that's left is a back-up bottom timer.

 

[UWSojourner]

2. ratio deco = a methodology (not rules) for starting with your algorithm of choice and adjusting it slightly to make a result that is really easy to remember..

I can see that. But are there more reliable and more accurate methodologies?

For example, consider tables. If you bring tables:

1. You can bring tables for any conceivable scenario.
2. You don't have to do mental math under stress -- just lookup the needed table.
3. No need to adjust the table to make it easy to remember -- more accurate.
4. Even these more accurate tables can be a BACKUP to a dive computer (or 2).

Ratio deco is to decompression diving as the rule of 72 is to financial planning. A decent approximation, but I wouldn't plan the details with either.

This new study provided evidence that a "well planned RD schedule" is not as good as a properly planned dive. And IMO RD 2.0 = another-on-the-fly-approximation-2.0.

Is RD best practice? Of course not.

 

[huwporter]

This new study provided evidence that a "well planned RD schedule" is not as good as a properly planned dive. And IMO RD 2.0 = another-on-the-fly-approximation-2.0.

I disagree: the study proved that "AG's lucky rabbits feet UTD Ratio Deco(TM)" schedule is not as efficient as a GF 30/80 schedule. It sheds no light on ratio deco as a methodology.

Just in case there was confusion: the ratio deco type 2 from my post that you quote above has nothing to do with "UTD Ratio Deco 2.0(TM)". I'll edit my post to type X and type Y to make that clear.

The rest of your post is more about philosophy and preference, which I have no wish to argue with. I'd compare it to a preference for manual (stick shift?) gears versus a preference for automatic gears. Either is fine, personally I wouldn't wish to do without driving a manual but that doesn't mean there is anything wrong with driving automatics.