What is Ratio Deco?

[Slamfire]

Let's just compare "apples-to-apples"...

Fact is that a dive with helium will require less time than the same dive without helium under Buhlmann. Saying that RD gets you out faster than either means nothing. Saying that because RD gets you out faster, Buhlmann is therefore penalizing is equally non-sensical. But I'll play along... Buhlmann penalizes helium and it penalizes nitrogen even more. Does this rephrasing satisfy your semantics? We all know that these are all penalties because the undisputed golden standard against which anything else should be measured is UTD RD.

RD is a supposedly Buhlmann/RGBM/VPM based shorthand methodology. It is supposed to have originated on their basic principles. Are there any numbers that explain why it does not comply with Buhlmann/RGBM/VPM? We already know helium has a lower lipid solubility and a greater diffusivity. Can you quantitatively show how RD used the measured differences in solubility and diffusivity numbers and applied it to dictate that deeper stops and shorter shallower stops were in order?

Eric Baker quantitatively showed how and why he modified Buhlman. So did Yount and Wienke. I realize that no one, not even the most rigorously scientific and analytical model has all the right answers about decompression. But I do believe there is value in following proper scientific protocols when it comes to hypothesis testing. Luck favors the prepared. Dismiss the science and make unprepared assumptions about the interactions of altitude or helium in human physiology and luck may not favor you at all.

 

[PfcAJ]

RD is right because RD is right. If RD is wrong its because RD is right.

Check...

 

[Kevrumbo]

Once again Slamfire . . .Buhllmann does not take into account the diffusivity & solubility of Helium versus Nitrogen and so will give you longer decompression total times with high Helium mixes than the method & strategy of Ratio Deco. Period. The exercise above with RD and the DPlanner profile was only to meant to illustrate this. If you want to play semantics by saying RD gets you out faster -then you yourself interpret it that way (and actually AG used to tout that as well, but with regards to the non-standardized mixes I've been using like Air & 20/20 "Economy Trimix", he understands all the additional O2 deco time padding that I've been adding to the RD Method). . .

Since I used mostly Deep Air here in Truk for the past month, the only thing I care about is doing enough deco to clear out all the residual inert N2 over consecutive days & weeks of diving -especially the slow fat tissues of my upper arms & shoulders- and not how much "cleverer" I am with getting out faster by applying strict Ratio Deco method.

 

[PfcAJ]

Once again Slamfire . . .Buhllmann does not take into account the diffusivity & solubility of Helium versus Nitrogen and so will give you longer decompression total times with high Helium mixes than the method & strategy of Ratio Deco. Period.

That's because ratio deco is wrong. Period.

Its not supported by ANY algorithm, and the guys doing real dives and real science don't use it for a reason. Too short of a decompression for long/deep dives, and too long of decompression for longer/shallower dives (like the Indian dive we discussed earlier in this thread).

For a short ocean thing, sure. But beyond that it just doesn't work.

I'd like to see things from your point of view, but I'd rather not get my head that far up AG's ass.

 

[Kevrumbo]

That's because ratio deco is wrong. Period.

Its not supported by ANY algorithm, and the guys doing real dives and real science don't use it for a reason. Too short of a decompression for long/deep dives, and too long of decompression for longer/shallower dives (like the Indian dive we discussed earlier in this thread).

For a short ocean thing, sure. But beyond that it just doesn't work.

I'd like to see things from your point of view, but I'd rather not get my head that far up AG's ass.

Of course it's not supported by any scientific algorithm -just simply an amalgamation of all the best application of deco theories as they have evolved -from classical Haldane, Workman, Buhlmann; Baker's GF implementation, and bubble mechanics of present day VPM and RGBM. Period.

Use it and apply it as you feel as needed for your own "real" dives. . . it works.

__
Now with regards to the deeper "Deep Stops" of RD on standardized high Helium mixes, my qualitative take on this is due to Helium's quantitative high diffusivity -and potential affinity for diffusing into any micro-nuclei/bubble seeds- which is why you want to keep these micro bubbles small with high surface tension, and kept there by higher/deeper ambient pressure of the Deep Stop.

 

[LiteHedded]

Guys, he took a (online probably) class on it 8 years ago. I think he knows what he's talking about.

 

[Kevrumbo]

Guys, he took a (online probably) class on it 8 years ago. I think he knows what he's talking about.

A group lecture & recitation by AG & Joe Talavera of 5thDx (pre-UTD company) eight years ago Feb at Loyola Marymount University. Set up IIRC by Andy Huber from Ocean Adventures DiveShop in Venice (Los Angeles area).

Plenty of practice since then -and a few "mal-practices" too- with lots of dive experience using RD on tech wreck trips here in Truk, Palau, Bikini Atoll, Vanuatu, South China Sea, Sunda Strait Indonesia, Sri Lanka and the Philippines. . .

 

[PfcAJ]

Good thing no research has been done since then. Whew!

 

[LiteHedded]

Good thing it never bent you like a pretzel in the meantime and made you want to do some actual research

 

[LFMarm]

Great to have redundancies and ways to plan a safe way out If everything fails. I just don’t get why not using computers because they may fail. How about flying planes with no computers because they may fail? Just bring 2 of them in case one fails and have with you tables or learn RD as backups. If people don’t understand how a computer is calculating the stops, you can find a computer with Buhlmann and even tweak it as you go if you want to increase or decrease your conservatism. There are many more chances of you getting your approximate calculations wrong than a modern computer fail.