UTD Ratio deco discussion

[mikeny9]

i just looked it up in GUEs newly released standards version 8 under 1.3.4 general training standards, "decompression diving conducted during GUE classes must use GUEs decoplanner as the referenced standard using the Buhlmann algorithm 20/85". nowhere does it say what to use when doing dives after the class as some may think

GUE does not have any standard.

They use it in examples, but it isn’t the be all-end all. My tech instructor used 30/85, so what?, Also, see your chart on page 26. 20/85, 30/80, and 30/85 are similar while RD and RD 2.0 are clearly outliers.

Fair enough. A friend of mine who recently went through GUE Tech 1 said "20/85 is the GUE standard." It appears he is wrong as well, as it's only a standard while in training.

Regarding the outliers, the deep portion of RD 2.0 and 20/85 are pretty similar until you get to the gas switch "o2 window" range, which is what I was pointing out with my "20/85" comment. The point being people are being very critical of UTD's "deep stops," yet 20/85 is fairly accepted and taught in GUE classes (at least while training)... a bit of a double standard.

 

[Rainer]

Fair enough. A friend of mine who recently went through GUE Tech 1 said "20/85 is the GUE standard." It appears he is wrong as well, as it's only a standard while in training.

Regarding the outliers, the deep portion of RD 2.0 and 20/85 are pretty similar until you get to the gas switch "o2 window" range, which is what I was pointing out with my "20/85" comment. The point being people are being very critical of UTD's "deep stops," yet 20/85 is fairly accepted and taught in GUE classes (at least while training)... a bit of a double standard.

I took my GUE tech training a decade ago. Can someone post the modifications that are currently being recommended by GUE for the ascent to the gas switch at 70'? I thought they'd gone away from 1 minute stops to 30 second slides. Someone else posted earlier that they were just teaching 30'/min to the gas switch. Those are both different than a straight 20/85.

 

[PfcAJ]

Fair enough. A friend of mine who recently went through GUE Tech 1 said "20/85 is the GUE standard." It appears he is wrong as well, as it's only a standard while in training.

Regarding the outliers, the deep portion of RD 2.0 and 20/85 are pretty similar until you get to the gas switch "o2 window" range, which is what I was pointing out with my "20/85" comment. The point being people are being very critical of UTD's "deep stops," yet 20/85 is fairly accepted and taught in GUE classes (at least while training)... a bit of a double standard.

I think some of the issue folks have (at least I have) is that after a gue course you've got the tools to made adjustments to your ascent plan by changing those gradient factors. With UTDs method you really don't.

Gue stops you at a depth because if he gradient factor. UTD stops you at a depth because AG says so.

 

[CptTightPants21]

I took my GUE tech training a decade ago. Can someone post the modifications that are currently being recommended by GUE for the ascent to the gas switch at 70'? I thought they'd gone away from 1 minute stops to 30 second slides. Someone else posted earlier that they were just teaching 30'/min to the gas switch. Those are both different than a straight 20/85.

30 sec slides/1min hold was for minimum deco on non-deco dives.

30’ ascent rate to the first deco stop then follow computer/dive plan normally.

 

[mikeny9]

I think some of the issue folks have (at least I have) is that after a gue course you've got the tools to made adjustments to your ascent plan by changing those gradient factors. With UTDs method you really don't.

Gue stops you at a depth because if he gradient factor. UTD stops you at a depth because AG says so.

Not really, using your same logic: if GUE stops you at depth using GFs (Buhlmann-based dissolved gas theory), UTD stops you at depth due to bubble theory.

I thought they'd gone away from 1 minute stops to 30 second slides.

FWIW, the "1 min stops" in UTD RD and RD 2.0 are also 30 second slides, e.g. stop for 30 seconds and ascend 10 ft in 30 seconds. They also follow a 30 fpm ascent rate to the first stop. Those stops are considered a "1 min stop" because the total time in between the 10 ft increment is still 1 min. It's more of a "pause" than a stop, but then again, all stops, whether they are 1 min or 30 min, are meant to be a practical fit to their model, which fits a curve for a theoretic slow continuous and gradual ascent. In other words, all stops just slow your ascent rate by some factor.

 

[PfcAJ]

Not really, using your same logic: if GUE stops you at depth using GFs (Buhlmann-based dissolved gas theory), UTD stops you at depth due to bubble theory.


FWIW, the "1 min stops" in UTD RD and RD 2.0 are also 30 second slides, e.g. stop for 30 seconds and ascend 10 ft in 30 seconds. They also follow a 30 fpm ascent rate to the first stop. Those stops are considered a "1 min stop" because the total time in between the 10 ft increment is still 1 min. It's more of a "pause" than a stop, but then again, all stops, whether they are 1 min or 30 min, are meant to be a practical fit to their model, which fits a curve for a theoretic slow continuous and gradual ascent. In other words, all stops just slow your ascent rate by some factor.

Nah, your logic is backwards. Gue suggests a stop depth is determined by gradient factors. Gradient factors>stop depth> easy to remember % of avg depth

UTD skips those first two steps and just gives you a % of avg depth.

The first step is an important variable. I (and others) have changed that variable and are therefor able change the 2nd step (stop depth) based on selecting the appropriate gradient factor.

 

[mikeny9]

Right, but it's the Buhlmann GF model that allows you change your first stop depth. It's bubble theory that's controlling the UTD 66% stop, not "AG."

 

[PfcAJ]

Right, but it's the Buhlmann GF model that allows you change your first stop depth. It's bubble theory that's controlling the UTD 66% stop, not "AG."

Explain the math behind arriving at 66% and why its no longer 75%.

 

[mikeny9]

I will let @Kevrumbo do that, he's more of the math expert. Or @rossh but I think someone banned him from the thread.

 

[PfcAJ]

I will let @Kevrumbo do that, he's more of the math expert. Or @rossh but I think someone banned him from the thread.

Come on man, its important stuff. You deserve to know why you're doing what you're doing. If you don't, why are you doing it?