Deco Gases

[triton94949]

You're right, but I just want to make the point that just because the deco software you use tells you something, that doesn't simply end the discussion for everyone and make everyone else wrong.

Holger has not told us yet what his deco software says, regarding the difference between TMX50/xx and EAN50. Therefore we only still have a sample of one: my subscribed deco software.

 

[jonnythan]

Holger has not told us yet what his deco software says, regarding the difference between TMX50/xx and EAN50. Therefore we only still have a sample of one: my subscribed deco software.

He has said that "most people" cheat their deco software by running the times given for EAN50 on 50/25, and feel better because of it. He also said that it is "known" that the He numbers used in most deco software are too conservative.

I've obviously no idea if he's right, but it's worth discussing, and if he is right, your deco software starts out the argument "flawed" in being too conservative for He.

 

[BigJetDriver]

I have tremendous respect for JJ. He is after all a NAUI instructor. And the author of a couple of books on scuba as well.

And Irvine is a stockbroker. I am sure he is good at that.

Triton,

With George Irvine III you have to be careful which "George" you are talking about. If you meet George personally, you will find that he is pleasant to talk to, and that he has a lot of very interesting stuff to impart when it comes to diving.

If you are talking about GI3 or Trey when they are on the internet, you are talking about someone whose posts are so harsh that you wind up thinking to yourself: "Is this the same man I was talking to? He seemed so reasonable then. What happened??" Now JJ, while a man of strong opinions, has taken a much more reasoned approach in his statements (generally), and as a result, gets more people to listen to him even though he is saying much the same thing.

Dr. Wienke, (Bruce Almighty), is an interesting guy. I have met him several times. He is fascinating to listen to because he has SO much information to impart. (This guy has a doctorate in atomic particle physics, after all.)

I read his books (I read around the high-level math. I am a pilot, not a mathematician! ). I talked to the man. I talked to people I know in the industry about the man.

What I learned boils down to this. He took the known theory, as produced by such people as the famous goat-bender (Haldane), and the respected Prof. Docteur Buhlmann, (both theories having been extensively tested by ourselves as crash-test dummies), and crunched the numbers.

Then he took the bubble model (gas phase) numbers and crunched those. Then he added the two together and crunched those numbers until they added up to a cohesive whole. All of this was in the fine tradition of those previous scientists, with the exception of the fact that they did not have Cray supercomputers to help with the job, and Bruce does! :11:

After that he took the tables to his folks on the NEST team, and the NAUI tech guys, Tom Mount, the WKPP troops, and others and said: "I know you guys are crazy enough to do this. Help test this stuff by being crash-test dummies." Of course, being the kind of people they are they said: "You betcha, big fella!" Thus it was that many man-hours of diving were put in on this program.

It can be said with certaintude that an awful lot of thought, computer time, and physical testing has gone into the effort to make RGBM a reality!

Cheers!

 

[triton94949]

My deco software IS the last word for me. That means I don't try to second guess the outcome or tweak the numbers I just follow the plan.
I think triton is just trying to present the view that George Irvine is not the last word on deco either although many seem to think he is. He has emperically trialed Bill Hamiltons tables but in a very limited environment. Depth, temperature, physical fitness, hyrdation are all factors to when determining deco profiles. It takes lots of real divers in lots of different environments to validate a deco algorithm or table.

I completely agree with you, Dave, on all points.

You have summarized how each of us feels about the deco software we have chosen for ourselves.

You have also stated the conservative view of not violating the prescribed output of the programmed algorithm.

You have also pointed out the fallacy of relatively sparse anecdotal trials being used to contradict a more vast sampling of data in the formulation of an algorithm.

These issues are paramount to safe deco diving. Thanks for helping to explain them to everyone.

 

[triton94949]

He has said that "most people" cheat their deco software by running the times given for EAN50 on 50/25, and feel better because of it. He also said that it is "known" that the He numbers used in most deco software are too conservative.

I've obviously no idea if he's right, but it's worth discussing, and if he is right, your deco software starts out the argument "flawed" in being too conservative for He.

Jonnythan, you have touched precisely on the issue of anecdotal trials. How safe do you think that is? To plug one gas into your deco software, and then do the dive with another gas instead? Doesn't that sound slightly insane to you?

 

[jonnythan]

Jonnythan, you have touched precisely on the issue of anecdotal trials. How safe do you think that is? To plug one gas into your deco software, and then do the dive with another gas instead? Doesn't that sound slightly insane to you?

I'm certainly the last one you should be asking that. I'm just saying that his "side" has merit with respect to the original question. No matter what your deco program says, using 50/25 might be "better" than EAN50. It might not, but "this deco program gives larger numbers for the trimix" isn't really "the answer," IMO.

 

[HolgerS]

Interesting. We all seem to agree, that deco-SW is not always up to date and never can reflect all individual, dive-specific issues.

So, why do most divers follow the software output without switching on brain?

Why didn´t anyone discuss the given arguments given in my posting? Why turning the discussion into CV- and academic-title questions? Is there any real interest to He in deco gases?


@ Triton
Be honest. You turned the thread near the edge of civilicity. I prefer proceeding with arguments pro/con He in deco mixes - with interested people.

Save diving - with or without He in deco mixes
Holger

 

[lamont]

Jonnythan, you have touched precisely on the issue of anecdotal trials. How safe do you think that is? To plug one gas into your deco software, and then do the dive with another gas instead? Doesn't that sound slightly insane to you?

Thinking the deco software is a perfect model of your physiology is a little bit more insane.

They're willing to do experiments on themselves. If they can get away with it, and they feel good after dives and people don't get bent, then the model in the deco software will eventually need to change. If everyone always dived exactly what the deco model told them to, we wouldn't ever advance in our understanding of decompression. You don't have to be one of the lab rats, but that doesn't mean you get to write off approaches which people are finding work as "insane" and wrong without having tried them.

 

[HolgerS]

@ Triton

I don´t use any deco-SW. I also don´t use any tables. Sorry, I cannot give you the SW-response you requested.

I personally do all my dives with "deco on the fly". I realized, that deco is - taking dual phase theory - quite linear for dives with BT shorter than roughly 90 min. Eric Maiken has proven this "scientifically". So I felt safe enough to elaborate my own rules. The outcome is pretty close to RGBM-GAP and V-Planner results. That gives me enough confidence.

I use deep stops and standard mixes with high He content "even" in deco mixes. So far, I am ok. I also adapt my deco schedule to dive specific and individual issues. Just by taking the thumb. But honestly, of course, I also discussed the rules with Micha Waldbrenner and other very experienced divers.

A small taste of my rules (not complete!!!):

90m depth, 10/70, 35/35, 50/25, O2
# Deep stops beginning at 80%atm
# additional deco schedule: 0,75:0,75:1,5:1,5

Meaning:
# 1,5*BT at 6m O2
# 1,5*BT at 21m to 9m with 50/25
# 0,75*BT at 36m to 24m with 35/35
# 0,75*BT at 51m to 39m with 10/70
# 1m/min ascent from 6m
# avoid body-exercise before, during and after dive ...

The allocation of individual steps, the adaptions regarding altitude diving, temperature, depth variations not listed here.

So, I have no SW results. Anyway, SW doesn´t tell you anything about He content in deco mixes. As posted.

Regards
Holger

 

[triton94949]

@ Triton

I don´t use any deco-SW. I also don´t use any tables. Sorry, I cannot give you the SW-response you requested.

I personally do all my dives with "deco on the fly". I realized, that deco is - taking dual phase theory - quite linear for dives with BT shorter than roughly 90 min. Eric Maiken has proven this "scientifically". So I felt safe enough to elaborate my own rules. The outcome is pretty close to RGBM-GAP and V-Planner results. That gives me enough confidence.

I use deep stops and standard mixes with high He content "even" in deco mixes. So far, I am ok. I also adapt my deco schedule to dive specific and individual issues. Just by taking the thumb. But honestly, of course, I also discussed the rules with Micha Waldbrenner and other very experienced divers.

A small taste of my rules (not complete!!!):

90m depth, 10/70, 35/35, 50/25, O2
# Deep stops beginning at 80%atm
# additional deco schedule: 0,75:0,75:1,5:1,5

Meaning:
# 1,5*BT at 6m O2
# 1,5*BT at 21m to 9m with 50/25
# 0,75*BT at 36m to 24m with 35/35
# 0,75*BT at 51m to 39m with 10/70
# 1m/min ascent from 6m
# avoid body-exercise before, during and after dive ...

The allocation of individual steps, the adaptions regarding altitude diving, temperature, depth variations not listed here.

So, I have no SW results. Anyway, SW doesn´t tell you anything about He content in deco mixes. As posted.

Regards
Holger

Well I am no expert at deco on the fly. I hope it works for you Holger.

Before using it, I would myself plug it into V-Planner to validate it. But then, I would only be relying on V-Planner again. Like Dave/Wedivebc said, it all boils down to what do you trust?

V-Planner tells me that if I mix HE with my intermediate (70 ft / 20 m) deco mixes, I end up with a longer deco time. That is what I trust.