Modern research/thoughts on Ascent Rates

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As soon as you take the curved output from whatever Bulhmann (or VPM even, or nearly any other) model and slap a "ratio deco" line on it you will be shifting at least some time deeper which is exactly what modern science says to avoid. You can undo that linearization, but you end up back where you started with a shape similar to the original GF 15/85 or 50/80 or whatever you started with.
No, that's not how it works at all. You're still mixing up the general mathematical concept of ratio deco with specific implementations thereof. There is nothing inherent in ratio deco which shifts some time deeper.

I think the source of your confusion is failure to understand that there are two totally separate curves at work here. Ratio deco planning is divided into two phases, each with its own curve.

In phase 1 you calculate the total deco time based on the depth and bottom time. For a given set of gasses you can visualize this as a 3-D surface plot with the independent variables of depth and bottom time on the X and Y axes, and the dependent variable of total deco time on the Z axis. That surface has a complex curvature based on the chosen deco algorithm (ZHL-16C or whatever you prefer), but within any small region it can be approximated as a plane. So, you can establish simple linear relationships to quickly estimate total deco time to within a couple minutes of the actual deco algorithm.

In phase 2 you take the total deco time calculated in phase 1 and divide it up into discrete stops every 10 ft / 3 m. There is no particular requirement to follow a linear ascent rate (although that is an option). You can come up with whatever heuristic you like there to approximate the shape of the optimal ascent curve. Some divers follow something like a Fibonacci sequence (I am not recommending that specifically, just pointing out that there are multiple options on how to approach this phase).

The specific implementation of ratio deco covered in some GUE tech courses is optimized for pragmatism in terms of being easy to teach and minimizing the risk of dangerous errors in the field. They aren't trying to squeeze out maximum efficiency just for the sake of getting out of the water 2 minutes faster.
 
This article is honestly dreadful, not really recognizing modern science...
Didn't bother reading any further. The article in question is basically a summary of the modern science and its implications for ZHL-16C + GF's.

Edit Note:
Per @grantctobin 's comment, there was an unnecessarily escalating comment here. It is now removed.
 
Didn't bother reading any further. The article in question is basically a summary of the modern science and its implications for ZHL-16C + GF's.
I would suspect a twenty minute phone call between RJack and Nick would rectify that they're discussing the same methodology from different angles and probably dive very similarly and make similar profile choices.
 
I think you've unnecessarily escalated this and (I would suspect) a twenty minute phone call between RJack and Nick would rectify that they're discussing the same methodology from different angles and probably dive very similarly and make similar profile choices. The bolding is a little laughable given your respective dive histories.
My issue had nothing to do with "Ratio Decompression" and RJack and Nick's argument about it. I know nothing about "Ratio Decompression".

The article Nick posted said nothing about "Ratio". It was a discussion about the implications of the latest dive science, the opposite of what RJack said it was.

Dive history is not relevant to science. There are many scientists with little or no dive history that are more expert on dive science than I with my modest dive history and also more expert that most divers with 1000s of dives. There are dive scientists who also have 1000s of dives (ie. Doolette, or Mitchell), but 1000s of dives by themself, does not put you in their class.

I am sure that RJack is infinitely more expert that I am on diving(where dive history is very relevant). But his statement on the article in question that I quoted is about the science. RJack might even be more expert on the science than I. But if so, I suspect he didn't actually read the article and just assumed the content.
 
This article is honestly dreadful, not really recognizing modern science.
rjack321:
I have read it several times. What people are being taught and actually doing does not align with anything in there.

Hi rjack,

I must say I find these statements surprising. I think David's article is a clear and balanced articulation of where things currently sit in relation to our knowledge of decompression from technical bounce dives. Like boulderjohn I would be interested in your opinion on where it fails to meet that standard.

boulderjohn:
You may say Dr. Simon Mitchell, but I think Dr. Mitchell gets a lot of his information from Dr. Doolette.

Yep, I gleaned most of my high-level knowledge of decompression physiology from David, just like he picks up stuff on the clinical side from me. Its a mutually beneficial collaboration.

Simon
 
Yep, I gleaned most of my high-level knowledge of decompression physiology from David, just like he picks up stuff on the clinical side from me. Its a mutually beneficial collaboration.
Human symbiosis :thumb:
 
https://www.shearwater.com/products/teric/
http://cavediveflorida.com/Rum_House.htm

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