My Journey into UTD Ratio Deco

[BRT]

It seems to me that accurately keeping track of average depth throughout the dive (without a computer) would be time consuming. I mean, you've got to sum a growing array of numbers and then calculate the average every 5 minutes? I guess it's doable if you had a slate, but it seems like this would take a significant bit of focus each time you do it right? I must be missing something obvious, what is it?

That does not appear to be what they are doing from the example. The example showed adding the depth for the last 5 minutes to the average up to that point and dividing by 2.

 

[PfcAJ]

@LiteHedded if this isn't DIR, then what is? AG is the biggest voice of DIR right now. UTD and ISE are the only ones actually calling their diving DIR. Now, I do understand your WKPP argument, and I also understand why JJ stopped using the term, but if UTD and ISE are promoting ratio deco, and promoting DIR, then that is to me more "DIR" than anything that GUE is doing right now. Unfortunate, but annoyingly true.

Being the biggest voice doesn’t mean you’re content is credible. There are guys who actually dive DIR and listen to and respect the best minds in decompression science.

 

[CAPTAIN SINBAD]

You can’t just ignore 7% difference in inert gas content.

Well...you can... but don’t expect the same DCS risk.

Agreed 100%!!! Using 25/25 in place of 32% and observing the same limits that is a valid point for class room discussion.

 

[tbone1004]

Being the biggest voice doesn’t mean you’re content is credible. There are guys who actually dive DIR and listen to and respect the best minds in decompression science.

100% agree with you, but unless you're part of that "club" DIR means whatever AG says it means to the public...

 

[LiteHedded]

I would really like to see when and where this happens. During my chat with Bob Sherwood (GUE) he also raised this concern that at certain exposure times you will deviate from established algorithms on ratio deco. From the test profiles I have been running on Multi-Deco, using standard gas (32%), using Min-Deco table while using UTD ascent profile, I have not come across such a situation at least in the Min-Deco depth and time limits but yes, I am open to seeing possibilities of where that could happen.

In fact I would encourage everyone to run a few Min-Deco single profiles as well as repeat profiles on your Deco-Planning software while following the guidelines I am posting below. These are from UTD Tech-1 Diver training manual which I am going through right now. For those who are new to this, some points should explain the UTD mindset.

• Unlike conventional tables the UTD Depth averaging table is a repeatable table. The bottom times do not change on this table and that is why it is one table committed to the divers memory.
  
• Instead of shrinking and expanding bottom times to fit within a moving No Decompression Limit, UTD will expand and contract its stop-times during ascent to ensure that you clear any deco obligation while repeating the table on consecutive dives.

1. For up to three dives a day you follow the same ascent schedule as long as you are putting 60 minutes of more of surface time between dives.
2. For up to three dives a day you double the stop times on each stop if your surface interval is less than 60 minutes between dives. In other words you are stopping to decompress twice as long after your recreational dives.
   
3. For more than three dives a day the audio-material suggests that you double all the stops no matter what the surface interval.

I have tested various versions of scenario A up there on Multi-Deco giving them only 60 minutes of interval to see if they would blow you out of the Buhlmann table and thus creating the departure that GUE community suggests caution against. For three dives a day, they get you out while keeping you within pure Buhlmann 100/100. On the fourth dive you are pushing it.

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NOTE: THESE ARE AVERAGE DEPTHS


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I didnt read this whole diatribe but like i said you wont find it on min deco dives (because there ISNT any real deco to speak of)

if you run a profile for say 200' for 70 minutes (a dive i did yesterday) you will see the divergence for yourself.

minimum deco is a very different thing than a ratio deco tech 1 or 2 dive with decompression gases

 

[CAPTAIN SINBAD]

I didnt read this whole diatribe but like i said you wont find it on min deco dives (because there ISNT any real deco to speak of)

if you run a profile for say 200' for 70 minutes (a dive i did yesterday) you will see the divergence for yourself.

minimum deco is a very different thing than a ratio deco tech 1 or 2 dive with decompression gases

I am not disputing you there. It is a legitimate concern and I see that. The depths and exposures at which it becomes a realistic concern may be outside of the this particular course limits.

 

[LiteHedded]

I am not disputing you there. It is a legitimate concern and I see that. The depths and exposures at which it becomes a realistic concern may be outside of the this particular course limits.

Maybe. What are the tech 1 max depths and bottom times? It falls apart quicker than you might think

 

[CAPTAIN SINBAD]

Maybe. What are the tech 1 max depths and bottom times? It falls apart quicker than you might think

UTD Tech 1 covers:

• 32% and 25/25 for Min-Deco (no deco gas)
• 21/35, 25/25 and 18/45 with 100% and 50%
• Max depth 160 with one deco bottle (AL-40 or AL-80)

Your maximum deco time is limited to 15 mins (one oxygen cycle) on 100% and 30 minutes on 50%.

 

[tbone1004]

@CAPTAIN SINBAD with a 15 min max O2 deco, you won't see any dive profiles big enough for it to fall apart. The danger with it is similar to his views on the Z-system about how everything is "scalable". Problem is, the Z-system doesn't actually scale to a rebreather because the whole point of it was primary donate which you can't do on the loop, and with the ratio deco, it works just fine for those tech 1 kind of dives, but it doesn't scale to the real big ones. AG has an inhuman ability to offgas so it may work fine for him, but he isn't everyone

 

[LiteHedded]

@CAPTAIN SINBAD with a 15 min max O2 deco, you won't see any dive profiles big enough for it to fall apart. The danger with it is similar to his views on the Z-system about how everything is "scalable". Problem is, the Z-system doesn't actually scale to a rebreather because the whole point of it was primary donate which you can't do on the loop, and with the ratio deco, it works just fine for those tech 1 kind of dives, but it doesn't scale to the real big ones. AG has an inhuman ability to offgas so it may work fine for him, but he isn't everyone

There is divergence at the edges of the tech1 limits as well. Not huge but it begins to get less conservative than the tables before you over run their max deco times.