Modern Ratio Deco usage?

[C Dub]

Do want. Mine has 30fpm to 75% then 10fpm to 50%, then 5pm to gas switch.

That is what my current T2 materials show.....

However, I have found that it is not at all unusual for what is taught during the actual class to change long before the materials do.

 

[KevinNM]

That is what my current T2 materials show.....

However, I have found that it is not at all unusual for what is taught during the actual class to change long before the materials do.

I was told there used to be (years ago) stops at 75%, not just ascent rate changes. Even for min deco ascents.

 

[boulderjohn]

Do want. Mine has 30fpm to 75% then 10fpm to 50%, then 5pm to gas switch.

This was not in my training, and i was trained by the other side anyway. So please help me to understand.

In another post in one of the threads on this topic I mentioned that I had put a dive profile to 200 feet into Multi-Deco with GFs of 50/80, and it had my first stop at 90 feet. My gas switch to 50% would have been at 70 feet. That means that with a steady 30 FPM ascent rate, I would reach that first stop in just under 4 minutes. My ascent (not counting stops) to the gas switch would be another minute. That means I would reach 70 feet after 5 minutes of ascent plus the remaining time for the stops at 90 and 80 feet.

If I were using ratio deco instead, it would take me not quite 2 minutes to reach the first stop at 150 feet. It would then take me 5 minutes of ascent plus the remaining time at 5 deco stops to reach 100 feet. It would then take me 6 minutes to reach my first gas switch at 70 feet. Is that correct?

In summary, with Buhlmann at 50/80, it would take me 5 minutes of ascent time plus the remaining time at 2 deco stops to reach 70 feet. With ratio deco, it would take me 13 minutes of ascent time plus the remaining time at 8 deco stops to reach 70 feet. Is that accurate?

 

[northernone]

How does this sanity check work?

The way he applied what he identified as ratio deco was as a mathematical ballparking of your deco obligation and a schedule which could get you home safer than a wing and a prayer while taking less time at depth working out a contingency plan on tables at depth if you found yourself outside of your slates and with computer trouble.... (one of the stories was a major restriction that hung him up, blew his thirds, lost a dive computer in the silt out and muck and then had his other computer freeze up on his ascent.)

I suppose that's a rather mild version of RD applied by a very experienced diver not the purist brand name version.

So with that in mind, it seems a rather useful tool to bring if I'm going to dive with Darwin.

Regards,
Cameron

 

[C Dub]

boulderjohn, I think you were trained in the UTD RD? They generate dive plans using their version of RD.

GUE's version RD does not generate dive plans. That is done with Decoplanner or similar software before the dive. GUE RD is ONLY used to adjust your deco time if you end up running longer/shorter or deeper/shallower than the plan generated by Decoplanner.

 

[LiteHedded]

i generated dive plans in my tech 2 class using ratio deco

 

[C Dub]

I'm guessing that was some time/years, ago? T1 was about a year ago and they did not have us generate plans with it.

 

[boulderjohn]

How can you be trained to use RD if you are not generating plans in your training?

My first training experience with RD was, believe it or not, with TDI, and that was before UTD existed. My TDI instructor had had some training with GUE, and some of it had been with Andrew when Andrew was with GUE. His TDI instructor trainer was (and is) thoroughly GUE/DIR oriented and works for Extreme Exposure (home of GUE) in Florida. I am having a hard time remembering the details, but as I recall my very first deco schedules were planned with DecoPlanner, after which we took the results and changed them to fit the GUE belief in the oxygen window and the S-Curve. We were taught RD principles then.

 

[PfcAJ]

Can you provide the research that supports this ascent rate?

I don't have any research that supports 20/85 (which is what that ascent rate is trying to mimick). Lots of anecdotal evidence, but that isn't what you're asking about.

 

[PfcAJ]

This was not in my training, and i was trained by the other side anyway. So please help me to understand.

In another post in one of the threads on this topic I mentioned that I had put a dive profile to 200 feet into Multi-Deco with GFs of 50/80, and it had my first stop at 90 feet. My gas switch to 50% would have been at 70 feet. That means that with a steady 30 FPM ascent rate, I would reach that first stop in just under 4 minutes. My ascent (not counting stops) to the gas switch would be another minute. That means I would reach 70 feet after 5 minutes of ascent plus the remaining time for the stops at 90 and 80 feet.

If I were using ratio deco instead, it would take me not quite 2 minutes to reach the first stop at 150 feet. It would then take me 5 minutes of ascent plus the remaining time at 5 deco stops to reach 100 feet. It would then take me 6 minutes to reach my first gas switch at 70 feet. Is that correct?

In summary, with Buhlmann at 50/80, it would take me 5 minutes of ascent time plus the remaining time at 2 deco stops to reach 70 feet. With ratio deco, it would take me 13 minutes of ascent time plus the remaining time at 8 deco stops to reach 70 feet. Is that accurate?

A system that's designed to mimick 20/85 will not put out an ascent that's the same as 50/80.