My Journey into UTD Ratio Deco

[Dan_P]

Pick the "average" you want. There always seems to be an argument for why it is "good enough" even if it is not the same as a real average. Either it is close enough, or practically the same, or safer, or whatever. Jeez.

No, and I think this sort of statement should be addressed.
What I've said is I'd need to go through a number of iterations to illustrate the degree of theoretical inaccuracy in the conflict highlighted above, to determine approximately how significant a discrepancy this would create in practice.

I don't think that's unreasonable.

@tbone1004 Don't take the bait. Whatever you say, he'll claim it is of no practical significance.

What I have actually said, and stand by, is I need to go through a number of iterations to illustrate the degree of theoretical inaccuracy in the conflict highlighted above, to determine approximately how significant a discrepancy this would create in practice.

You can deduct something to that effect from this quote:

I'd need to go through a number of iterations to illustrate the degree of theoretical inaccuracy in the conflict highlighted above, to determine approximately how significant a discrepancy this would create in practice.

When someone then posts a question (statement) that seems to assume such discrepancy, I'd naturally ask if they wouldn't mind sharing the basis on which they've landed on that conclusion.

That's a very reasonable response.

 

[Dan_P]

I might indulge in learning and using rd as an interesting exercise as I do with monitoring my gas consumption and pressure remaining but I always check my estimates against an actual gauge. Similarly I would monitor my Perdix while diving and would always rely on it. RD would be game of the mind that would give me a way of thinking while diving. When SHTF that will be jettisoned while my available brain cells are focused on problem solving.

I don't think this is an unreasonable way to approach the matter.

Look, when I first heard of RD, I was using laptop, software, slates, wetnotes, and quite a lot of time pre-planning a dive. Then someone came along and said I could do all that in my head, on the fly.

"Bollocks!", I thought - but I took it for an honest spin to find out.

Scepticism can be conducive to perspective.

 

[NAM001]

Personally, I think that's in essence an accuracy-versus-practicality question.
I'd need to go through a number of iterations to illustrate the degree of theoretical inaccuracy in the conflict highlighted above, to determine approximately how significant a discrepancy this would create in practice.

But in terms of where this is really relevant - we'd stereotypically be talking caves, right?
And usually when we don't know where we're going (or we wouldn't need to at least partly rely on [an approach] to determine average depth in-water).
So pretty much, we're talking non-entry level cave, probably exploratory.

At that point, I suppose a diver has gone through the iterations needed to form a more concise answer and choice.
That's an important aspect of it, I think.

I'm not the right diver to answer the question, and in either case, certainly not in any official capacity.

But I think it's a good question.
Personally, if this became a significant thing for me on a dive, I'd probably pad the shallows - if feasible. If that's unfeasible, I'd disregard it as whatever's keeping me from spending extra time in the water is probably a bigger problem than this one.

thanks .... I did not consider this from the cave aspect where the cave dictates your depths as much as open water gives the diver the latitude of max depth control. surely the cave environment will not be the open water ever progressing going deeper. My thought was more an open dive at a wreck.

 

[Dan_P]

thanks .... I did not consider this from the cave aspect where the cave dictates your depths as much as open water gives the diver the latitude of max depth control. surely the cave environment will not be the open water ever progressing going deeper. My thought was more an open dive at a wreck.

Sure thing.
I can only speak from the perspective that my experience allows, and that doesn't include the long, exploratory cave dives, yet.

That said, what I can say is that I haven't encountered iterations where I personally find this problematic for open water-diving.
I think I'd best leave it on the individual diver's own accord to dry-run relevant iterations on examples of their dives, and see what difference there is in theoretical loading, when using different approaches.
I think that's a good way to approach the question.

For me, when I play this on my laptop, the inaccuracy/discrepancy is so small that I'm perfectly okay accepting it.

For the heavy end of the spectrum, given my own limitations as posted above, I assume we're probably looking at the question in a Max Deco-setting anyway.
If so, then the question probably relates most to what would happen if we'd use this methodology beyond Max Deco - in the land of saturation diving.
I'm not the right diver to make the argument that that's the case, though - but if it is the case, then I would argue that we can't expect recreational (rec and tec) methodologies to necessarily hold true in commercial (saturation) diving. It's beyond the scope.

So, long story short, at this time I don't personally identify the use of this averaging methodology as problematic in recreational and technical diving.

 

[NAM001]

Sure thing.
I can only speak from the perspective that my experience allows, and that doesn't include the long, exploratory cave dives, yet.

That said, what I can say is that I haven't encountered iterations where I personally find this problematic for open water-diving.
I think I'd best leave it on the individual diver's own accord to dry-run relevant iterations on examples of their dives, and see what difference there is in theoretical loading, when using different approaches.
I think that's a good way to approach the question.

For me, when I play this on my laptop, the inaccuracy/discrepancy is so small that I'm perfectly okay accepting it.

For the heavy end of the spectrum, given my own limitations as posted above, I assume we're probably looking at the question in a Max Deco-setting anyway.
If so, then the question probably relates most to what would happen if we'd use this methodology beyond Max Deco - in the land of saturation diving.
I'm not the right diver to make the argument that that's the case, though - but if it is the case, then I would argue that we can't expect recreational (rec and tec) methodologies to necessarily hold true in commercial (saturation) diving. It's beyond the scope.

So, long story short, at this time I don't personally identify the use of this averaging methodology as problematic in recreational and technical diving.

I think you are correct. For recreational diving I think we all have an idea what our max depth is. And to be honest in the rec world it doesn't hurt to just take the max depth to make decisions on. Unlike the use of RD with the right gas and being 140 ft for 30 min and trying to determine a deco obligation. I say that because rec diving by default is no deco diving and as such the fine points of determining avg max depth to calculate deco is not much more than trying to find the equivilant tech process to implement in the rec world. Rec world already has the safety stop process to use as a reliable catch all for boo boo's. And if necessary you can stop at half depth for 5 min is you are unsure. gas limiting factor decision of course. I have tried to use the RD for 32 nitrox in rec depths and it provides nothing much surprising info. I have suspected that these Rec RD things may be a prep for RD with trimix on deep deliberate DECO dives. It sounds like """""" we have a program/ process called RD that can be implemented from day one of a divers training for the purpose of making the norm of no computers."""" It is a logical thought process only if the ultimate training level is predetermined. That opinion for me is supported by the agency names of GUE and UTD.

Thanks for the conversation and the open mindedness while engaging in it. More discussions should be this congenial.

 

[Scuba J7]

It’s not much of a discussion if it’s all congenial. Just a bunch of back patting and congratulating.

 

[Dan_P]

The exchange of ideas was to mutual benefit.

 

[Michael Guerrero]

@CAPTAIN SINBADThe discussion against RD isn't about min-deco because that's not "decompression". The points against, including what Bob said, are about "exposure times" that are "real". I.e. multi hour dive profiles with trimix, multiple decompression gases, etc. not light backgas deco or NDL diving.

This thread is in the Advanced forum, so talking about bigger dives might be irrelevant. I can see how it might be nice to have a way to just jump in the water for some light recreational diving and be able to come up with a plan that makes you feel comfortable, without having to print out tables ahead of time. That's not really the "plan your dive, dive your plan" mentality, but I think harmless on these types of dives.

That said, my Petrel already does all this for me, and gives me an ascent profile I think is reasonable (I wouldn't execute the one you mapped out above). I would find having to do (even simple) math every five minutes bothersome and would rather just focus on enjoying the dive and monitoring my time using my computer. I'm not sure how much this class cost, but I got my Petrel for $500 used and it's going strong after 5 years of diving. To each his own.

 

[Michael Guerrero]

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

Particularly given the research from David Doolette that we should be treating He and N the same in aqueous tissues in terms of washout. Wonder if there's some lingering "helium is faster" thinking going on. Or maybe the profiles are tame enough that it doesn't matter much.

 

[mikeny9]

Particularly given the research from David Doolette that we should be treating He and N the same in aqueous tissues in terms of washout. Wonder if there's some lingering "helium is faster" thinking going on. Or maybe the profiles are tame enough that it doesn't matter much.

If you're referring to Decompression from He-N2-O2 (trimix) bounce dives is not more efficient than from He-O2 (heliox) bounce dives., the study does not claim that Helium and Nitrogen should be treated the same, but that Helium should be treated no worse than Nitrogen, hence all the the noise about eliminating the Helium penalty.

However, it does not prove that Nitrogen is the same as Helium with regard to decompression. Therefore, Helium might actually be better, but there is no research that proves (or disproves) that theory.