Ascent rates - normoxic Trimix on OC

[boulderjohn]

Most divers target something like 9m/30ft per minute for planning the ascent from the bottom to the first real deco stop, and then progressively slow down.

You and I have different experiences from which to draw our opinions on what most divers do. Every diver I have ever done a tech dive with does a standard 9m/30F PM ascent up through the final stop. The final portions of the dive are effectively shower because of the decompression stops, but the ascent speed between the stops does not change.

 

[PfcAJ]

You and I have different experiences from which to draw our opinions on what most divers do. Every diver I have ever done a tech dive with does a standard 9m/30F PM ascent up through the final stop. The final portions of the dive are effectively shower because of the decompression stops, but the ascent speed between the stops does not change.

Hmm I and others are slower between stops. 10fpm.

 

[rjack321]

No one has done controlled experiments on this so you're not going to find any hard data.

This ^^^
There's no data on how fast to move between stops. Even if someone tried to figure this out, you're talking about differences of (at most 40 seconds) between 3m/min and 9m/min. This is not a question with any money behind it worth investigating.

 

[boulderjohn]

Hmm I and others are slower between stops. 10fpm.

Which does not change what I wrote in my post, since I have never dived with you or anyone else who followed that practice.

 

[flymolo]

30fpm up until the 1st stop then 10fpm after that...

same procecdure on ccr tho admittedly it's harder to nail 30fpm on ccr

 

[PfcAJ]

Which does not change what I wrote in my post, since I have never dived with you or anyone else who followed that practice.

You’re the first person I’ve ever heard of who reports people doing 30fpm between stops.

 

[Kendall Raine]

Slower ascentspeeds can be similied to "adding deep stops/lowering GFlow". This was all the hype a few years ago, but does indicate that deep stops do more harm than good. You basically end up ongassing some tissues while offgassing

The problem with the term “deep stops” is that people equate the term “deep stop” with the first stop called for in a dual phase model. That’s imprecise. To be accurate, anything deeper than the first stop called for in a dissolved gas model is a “deep stop.” That is, anything less than a GFlow of 100%. The problem is many people don’t make the distinction between dual phase and “deep stops.” What’s been questioned by the NEDU study, and those preceding it, is whether a dual phase shape is better than one with shallower “deep stops.” NEDU says no. In fact NEDU results suggest a true dual phase shape (e.g. VPM, RGBM) is worse. However, even the Navy’s VVAL 79 prescribes first stops much deeper than a traditional dissolved (Buhlmann, Haldane, derivatives) phase model. In fact VVAL 79 will adjust first stops (implied GF low) and GF high depending on bottom depth.

Hence, saying things like “deeps stops are bad, debunked, whatever” is virtually meaningless and really should be phrased “dual phase” shapes are probably no better, and could be worse, than a first stop shallower.

It should be remembered that the genesis of the dual phase shape was that straight Buhlmann was considered to have its deepest stop too shallow. A lot of smart people were involved for a long time with the thought behind the dual phase concept. Current thinking is that such dual phase models make the deep stops too deep, not that a straight dissolved model is correct.

 

[100days-a-year]

30-60fpm to 1st stop. 10fpm between stops. Maybe 5 fpm last stop to surface.

 

[Learner Diver]

The deco program you’re using will have a parameter for the ascent rate. I think you’ll be hard pressed to find any real data regarding ascent rates to the 1st deco stop.

30fpm seems to work, and that’s the default setting of most decompression programs.

I have read that CCR divers need a slower ascent rate than open circuit divers. What's your opinion?

Which does not change what I wrote in my post, since I have never dived with you or anyone else who followed that practice.

I have read Shearwater have arrows indicating fast ascents past 9 metres per minute. What's your opinion?

 

[PfcAJ]

I have read that CCR divers need a slower ascent rate than open circuit divers. What's your opinion?

I have read Shearwater have arrows indicating fast ascents past 9 metres per minute. What's your opinion?

I don’t know of any reason for that to be the case. I dive a pSCR and I don’t change my ascent rate because of it. Interested in others opinions and rationale though.