Ongoing discussion of Ratio Deco

[limeyx]

With all due respect,

In the DIR forum where DIR answers are required.
Deep stops would be a part of D-plan as taught by GUE.
When this program is used as it is taught by GUE, deep stops and shaping of the curve are included.
Where do you guys think AG got his deep stop protocol for ratio deco from?
Therefore to exclude these stops from D-plan would in my opinion be considered a non DIR answer.
Since these protocols clearly came from GUE first.

In another forum under different circumstances(program used without GUE training) I could see your point.

Sincerly,
Milo

yes, I (now?) think they need to be in the DecoPlanner column too (unless the implication is to dive the DecoPlanner profiles with no deep-stops which probably/possibly is not DIR -- whatever)

However, you can't just say "Hey, take the DP output and assume we do deep-stops" I think they would have to be programmed into DP as "waypoints" etc because they will then affect the profile.

 

[grazie42]

Isn´t the strict DIR-answer that RD is right and the rest is wrong, might as well delete the whole thread then...

It may be that most(?) users add deepstops to dplan-profiles, the same point could propably be argued with v-planner but these profiles are what the software generates "out of the box" so that´s what I´m comparing with...

The only one who has said dplan is DIR is you (ScubaMilo), only to argue that it isn´t...

I´ve never said or implied that the 30/85-profile is DIR...The RD-paper encourages the reader to compare the profiles with vplanner +2 & GF 30/85, that´s it. If you disagree with the profiles, feel free to take it up with whoever sells dplan...

That is what the table does (I added hdplan because someone was nice enough to run the profiles)...If it makes you feel any better the profile was provided by a GUE-instructor...he had reservations about gas-choices for some of the depths but the profiles are still what comes out of the software (he says, I don´t own dplan)...


ymmv

 

[ScubaMilo]

Isn´t the strict DIR-answer that RD is right and the rest is wrong, might as well delete the whole thread then...

Actually, No
As far as I know ratio deco is not taught as, or considered to be, a stand alone method for planning deco by GUE.

The only one who has said dplan is DIR is you (ScubaMilo), only to argue that it isn´t...

I'm not the only person saying D-plan is DIR it's actually in the GUE standards as the program of choice for verifying deco planning.
Actually I did not say D-plan was not DIR what I said was using it in the manner you suggested would not be considered a DIR aproach to planning deco using this program.

I´ve never said or implied that the 30/85-profile is DIR...The RD-paper encourages the reader to compare the profiles with vplanner +2 & GF 30/85, that´s it. If you disagree with the profiles, feel free to take it up with whoever sells dplan...

I didn't say I disagree with the profiles.
I disagree with the Idea of giving one program credit for deep stops and not the other.

I think some of my post may have been misunderstood.
I hope this makes it a little clearer.

Safe diving,
Milo

 

[ScubaMilo]

However, you can't just say "Hey, take the DP output and assume we do deep-stops" I think they would have to be programmed into DP as "waypoints" etc because they will then affect the profile.

I'll concede.
You seem to have a good point here.
How did Gideon teach you guys to do this?

Milo

 

[limeyx]

I'll concede.
You seem to have a good point here.
How did Gideon teach you guys to do this?

Milo

The same way you are doing it
1) ratio deco and/OR
2) DecoPlanner, then shape the stops and add deep stops-- but not quite the same shape as an RD 'S-curve' -- more like adding minutes at the 70 foot stop, rolling minutes in from the 80 stop to 70 etc.

I will share the T1 slide with you privately if you want to see, but I bet it's similar to what AG teaches, and probably to what Chris/Anders do.

Gideon asked us not to share his slides publicly, so obviously if I send to you, please respect that.

having said that, I think you do lose something of the "scientific-ness" of decoplanner this way, but I would argue that it's still a cleaner profile.

 

[ScubaMilo]

The same way you are doing it
1) ratio deco and/OR
2) DecoPlanner, then shape the stops and add deep stops-- but not quite the same shape as an RD 'S-curve' -- more like adding minutes at the 70 foot stop, rolling minutes in from the 80 stop to 70 etc.

I will share the T1 slide with you privately if you want to see, but I bet it's similar to what AG teaches, and probably to what Chris/Anders do.

Gideon asked us not to share his slides publicly, so obviously if I send to you, please respect that.

having said that, I think you do lose something of the "scientific-ness" of decoplanner this way, but I would argue that it's still a cleaner profile.

Nick,

I would love to see the slide If you can PM it to me or send it to my E-mail address: Scubamania1@aol.com
Thanks, and of course I will respect it and not make it public.

Milo

 

[globaldiver]

I think this is a very interesting dicussion, but fail to see how Milos caution of a perception of RDs totality can be misinterpreted. Every decompression model or program has its limitations. To use sources like RD, decoplanner, and similar, to form and tweak your decompression schedule in accordance to DIR/GUE methods is what, as far as I know and have learned, normally is used in DIR. I have personally never heard phenomenal divers and instructors like JJ, Rhea, RL, AG, etc., say that a GUE/DIR-diver performing decompression dives always could solely rely on RD for the decompression planning, or that it is the only method using deep stops. The deep stops are a normal part of GUE dive planning, and RD, Decoplanner, etc., are just tools used to be able to make a safe and proper decompression schedule and dive. Deep stops, when needed, are always added anyway, even when using Decoplanner as a tool.

I do not think that Milo is saying that RD is a bad tool or model, just that it has some limitations that should be considered when planning a decompression dive. I have many times dove with him and Chris where we have used RD and we have all been fine. The additional use of Decoplanner is however a useful recommendation/directive of GUE, and I cannot see anything negative in also using this as an intricate tool. The more information we have before a dive, the better and hopefully safer the dive will be.

I think that RD is a very intelligently constructed, and useful tool for certain decompresion diving, but like everything else it has its limitations. That is also probably why GUE in T1, teaches RD, but also (besides teaching oxygen window, S-curves and dissolved gas theory) teach the use of Decoplanner. This enables you to easily compare both the Bühlmann and VPM profiles generated, and to adjust them to DIR diving as an intricate part of the dive planning.

Decompression planning is, in my view, not primarily about simplicity but all about safety.

Sincerely

Anders

 

[rjack321]

Hey, I'm all for understanding deco theories through various tools. Including even Haldane :shakehead

However, I do take exception to the concept that theories, which we strongly suspect are incomplete (e.g. Buhlmann) and somehow holding them up as the only "scientifically valid" methods.

The proper definition of valid IMO is:
Are people diving those profiles routinely without getting clinically or subclinically bent?

In my T1 class, it was obvious but unspoken that Buhlmann was the "legal dept. approved" way of deco. And roughly a RD profile was the "real way".

Then again, I was taught by the best koolaid heretic out there

 

[addexdiver]

RD uses "80% ATA (75% depth)" as an approximation of the commonly calcuated start of decompression zone where the leading compartment has a gradient to off-gas. Just the same as running a VPM-B profile (deco zone starts ~2 ATA less than bottom) or running a (GF Low=5 to 10) Buhlmann profile. /QUOTE]

Why not simply adjust the low GF value in Decoplanner to incorporate the deep stops and the high GF to get the total deco time in line? This allows for extension to profiles not quite at the "RD sweet spot" and that use an accepted GUE approach (the science behind Decoplanner)...GF 5/90 or thereabouts yields very GUE-RD profiles.

I think the RD approach is great because it can be used "on the fly" - but why do that when most dives are planned? Decoplanner is a very good tool. Why limit the power of a tool that has a GF adjustment. After all, the low GF applies only to the deepest stop, and the high GF to the shallowest - all the other stops are linear interpolations of GF setting by depth (deepest to shallowest).

Stow the Napalm, just use the flamethrower - Good thread.

 

[FishTaco]

Hey, I'm all for understanding deco theories through various tools. Including even Haldane :shakehead

I know I’m a little off topic here…
But, I wouldn’t shake my head at Haldane’s contributions in developing the dissolved gas model. Remember, it was Haldane who established the concept of “tissue” compartments, and “ascent limiting criteria”. Then other scientists built upon this work, Workman established M-values, not to mention contributions by Schreiner, Buhlmann, Hamilton, etc. that built upon this work.

BTW, does anyone know who actually developed ratio deco? Was it AG?

Take care,
Chris