Ratio deco #1

[ucfdiver]

You can look at the graph of tissue loading and estimate max deco.

 

[Slamfire]

So basically saturation. If you are doing dives deep and long enough to max the tissue loading (saturate tissues) I would think you would know about not taking the decompression algorithm beyond saturation and allowing it to penalize you needlessly. The way I read his comment, I thought he had reinvented a new wheel and found a way to do deco much more efficiently.

 

[ucfdiver]

So basically saturation. If you are doing dives deep and long enough to max the tissue loading (saturate tissues) I would think you would know about not taking the decompression algorithm beyond saturation and allowing it to penalize you needlessly. The way I read his comment, I thought he had reinvented a new wheel and found a way to do deco much more efficiently.

I read it as a marketing person who's selling scuba classes...and if you need it, scuba agency gear, too!

 

[limeyx]

I read it as a marketing person who's selling scuba classes...and if you need it, scuba agency gear, too!

You could look at it that way, but then again AG and NT actually put their butts on the line and went out and actually did the dive.

I would say anyone interested should probably email Andrew directly

 

[rjack321]

So basically saturation. If you are doing dives deep and long enough to max the tissue loading (saturate tissues) I would think you would know about not taking the decompression algorithm beyond saturation and allowing it to penalize you needlessly. The way I read his comment, I thought he had reinvented a new wheel and found a way to do deco much more efficiently.

People don't dive 30/85 GF Buhlmann on the big big dives (like the Pit) either. They fudge the software to 20ish/130ish GFs or something like that because it works and 30/85 is bloody overkill for the really long dives. They should theoretically be bent like pretzels surfacing with a GF 20-30% greater than allowed, but aren't.

Once again, Buhlmann is wrong. The model has utility for some people within certain ranges but its "accuracy" is no better than RD.

I dunno why every one wants this stuff to "match" - I could give a damn what matches what or not. Just get me out of the water unembolized and unbent.

 

[Slamfire]

People don't dive 30/85 GF Buhlmann on the big big dives (like the Pit) either. They fudge the software to 20ish/130ish GFs or something like that because it works and 30/85 is bloody overkill for the really long dives. They should theoretically be bent like pretzels surfacing with a GF 20-30% greater than allowed, but aren't.

Interesting. I heard someone once say something like "the deeper you go, the more decompression theory moves away from science and into the realm of black arts."

I dunno why every one wants this stuff to "match" - I could give a damn what matches what or not. Just get me out of the water unembolized and unbent.

The reason behind the fascination with "matching" is the ability to replicate results. The man says this is not based in science. I think, "thank you for being honest and getting that out of the way." He says, this is based in his many thousands of dives and it works great for him. I think, "good for you, but how do I know that it will work for me?"

A scientific methodology strives to get duplicable results under controlled conditions. When you take away scientific methodology, you have to introduce faith into the equation. So I am then supposed to put my faith that I won't get bent simply because somebody says so, and there is no scientific proof behind it... Hard pill to swallow. If I could see that it matches to something that has a scientific methodology, things become easier to accept. This is the way our society has been educated.

 

[rjack321]

Interesting. I heard someone once say something like "the deeper you go, the more decompression theory moves away from science and into the realm of black arts."
The reason behind the fascination with "matching" is the ability to replicate results. The man says this is not based in science. I think, "thank you for being honest and getting that out of the way." He says, this is based in his many thousands of dives and it works great for him. I think, "good for you, but how do I know that it will work for me?"

A scientific methodology strives to get duplicable results under controlled conditions. When you take away scientific methodology, you have to introduce faith into the equation. So I am then supposed to put my faith that I won't get bent simply because somebody says so, and there is no scientific proof behind it... Hard pill to swallow. If I could see that it matches to something that has a scientific methodology, things become easier to accept. This is the way our society has been educated.

If you actually took a deco course from AndrewG you'd discover that this not how RD is presented today. You are "supposed to" conservatively try it and gradually build an understanding of what works for you. Most of the elements of RD (deep stops, "O2 window although that's a bit misnamed, and shallow stops for dissolved gas are founded on a mix of what's understood about deco theory). Pure Buhlmann is for instance only a dissolved gas theory which does not address inevitable bubbling. There's not alot of trust, more "here are the concepts we agree upon how do we put them together into a plan?" If you don't agree with the 3 basic pillars of RD then use one of the other products which incorporates the concepts you do agree with. In simple terms:
Buhlmann = dissolved only (GFs being a bubble kludge)
VPM = dissolved + bubble
RD = dissolved + bubble + deep stops

On a side note... Successful deco is barely reproducible as it is, you can do the exact same profile multiple times and then wham just get hideously type2 bent out of the blue. Personally I think these are probably deep bubble formation hits which are semi-stocastic with some loose relationships to hydration.

If you are demanding scientific "proof" of "safe" deco before proceeding then you should probably quit diving.

 

[Mr Carcharodon]

It's about doing what works not what is officially scientific. After thousands of successful dive there is a practical validation that is on par with what dsat and dciem did. You may not like it but the proponents keep doing it because it works.

 

[lamont]

From a thread on another board (text bolding by me):

I've read the Shape of the Curve and understand why it doesn't have to mirror any specific algorithm. But how in the Poseidon's trident do you go from reducing a 1200 mins deco obligation to a mere 400? What is this Max Deco thing? What is the rationale behind it? One of the first things AG acknowledges during his RD seminars is that there is no scientific methodology or proof for RD. That it is merely an arithmetic "fit". So then how do you explain this dramatic departure from something that you're "fitting" your deco profile to? It's gotta be more substantial than just AG's feeling, no? Does it have to do with saturation diving?

VPM-B from v-planner with +2 conservatism doesn't reproduce anything like the 1200 minute deco obligation, closer to 500-600. If set it to nominal and eliminate the helium from the deco gases (eliminating the helium weenie factor from the algorithm) and include 18%, 21%, 30%, 50%, 100% deco gases then I can get it down to 480 minutes of deco.

 

[lamont]

People don't dive 30/85 GF Buhlmann on the big big dives (like the Pit) either. They fudge the software to 20ish/130ish GFs or something like that because it works and 30/85 is bloody overkill for the really long dives. They should theoretically be bent like pretzels surfacing with a GF 20-30% greater than allowed, but aren't.

Once again, Buhlmann is wrong. The model has utility for some people within certain ranges but its "accuracy" is no better than RD.

I dunno why every one wants this stuff to "match" - I could give a damn what matches what or not. Just get me out of the water unembolized and unbent.

From a model approach the GF kludge is going to apply the GF_hi limit to very different compartments depending on what the exact profile is. Never seemed to make a lot of sense to me. But saying that 30/85 works for T1 dives and 20/130 works for certain very long/big dives makes as much sense as any other decompression voodoo. Its on precisely the same foundation as ratio deco -- "it works".