Spisni study

[Akimbo]

Not quite. See for instance the O2 cells from the rebreathers.

True, I stand corrected. However that is a special case with widely-recognized electrochemical sensor-drift that rebreather's are programmed for and redundancy is provided. Basically eCCR divers expect it and are trained to manage it. Dangerous for sure, but not unanticipated.

The worst case relative to this part of the discussion is a software bug that undercalculates your decompression obligation and you get bent like a pretzel. We intellectually know that the possibility exists but don't really anticipate it.

 

[Dan_P]

Hmm, a lot of good points in this one, for sure.
And I also think it's probably correct to speak about this matter as a subject to personal preference.

As @Diver0001 says, we'll need a quite specific study for proof, and it'd probably need to stretch across a great (and likely unavaible) amount of divers, measuring many things including DCS as well general injury and fatalities.

I think the scope and scale would be well beyond anything we're looking at in relation to typical studies' sizes.

For me, it's not even about the gear failing, even though that is of course an eventuality (however unlikely it may be).
It's more that I feel more relaxed having calculated my reserve gas and decompression obligation myself, and checked against the team's results. Sure, it's more work at first, definitely. I'm not going to try and deny that.
But to me, I feel it's no more taxing than the flow check - as a matter of fact, I've incorporated everything into it - /Ratio Deco/Rock Bottom/flow check/SPG check, usually once every 10 minutes-ish. Takes 10 seconds.

Personally, I've found it to be a worth while investment. The next diver might not, and that's perfectly fine.
I don't feel that either way is dangerous, but both have inherent dangers if done "the wrong way".

I feel it's a snowboard vs. ski-conversation.

I also think the rebreather-example is an interesting one - there's the same "external" control of what the machine is doing, separate from the cells, i.e. "I have Nx32-flushed the loop at 30m, my ppPO2 should equal approx. 1.28" to cross-check the voting logic.

Same with the SPG in general (O/C): I calculate what it ought to read, then control it and detect error in the gauge or deviance from norm, and I know how to calculate a new amount of gas (Rock Bottom) to adjust.

Same with the decometre (if any). I want to establish what it ought to read, before I look at it.

In either case, to me, it's about establishing familiarity with my way home.
I think that's what's important.

 

[RayfromTX]

So dive and let dive? That seems fine with me right up until an instructor is teaching to use RD in lieu of using a proper dive computer. Teaching tables is one thing. Teaching Ratio Deco as the only means of tracking and implementing a deco plan seems very risky to me. I would tell that to any friend or relative that told me they were using RD without a computer. I don't have experience as a deco diver but I have a lot of experience in how the human brain works and enough experience with the unrecognized impairment that occurs while diving to never add that layer of thought process to what there already is to keep up with. It will work until it doesn't.

 

[tridacna]

How many RD devotees are there worldwide? And will this issue ultimately disappear in a Darwinian context? There is a lot of discussion IMO about a method that is used by a teensy weensy segment of tech divers generating a huge amount of antipathy. Kinda like the last group of pilots insisting on flying their aircraft without electronic instruments.

 

[Dan_P]

So dive and let dive? That seems fine with me right up until an instructor is teaching to use RD in lieu of using a proper dive computer. Teaching tables is one thing. Teaching Ratio Deco as the only means of tracking and implementing a deco plan seems very risky to me. I would tell that to any friend or relative that told me they were using RD without a computer. I don't have experience as a deco diver but I have a lot of experience in how the human brain works and enough experience with the unrecognized impairment that occurs while diving to never add that layer of thought process to what there already is to keep up with. It will work until it doesn't.

Dive and let dive works for me.

As for RD versus tables, I don't feel there's a big difference in terms of depth averaging.
I figure out what the average "ought to be", then confirm it against my gauge.

How many RD devotees are there worldwide? And will this issue ultimately disappear in a Darwinian context? There is a lot of discussion IMO about a method that is used by a teensy weensy segment of tech divers generating a huge amount of antipathy. Kinda like the last group of pilots insisting on flying their aircraft without electronic instruments.

While I don't agree with the Darwin-angle, it is a minority for sure, and tech divers aren't that many to begin with.
I suppose you can interpret that as my opinion that the debate around it has been out of proportion.

In either case, I feel that "flying manual" gives me peace of mind when I'm diving - but that's just my vibe.
If I were "flying automatic" instead, I'd consider at least that manual is my primary backup mode.

But I think there's a resonably good takeaway from this in saying there are potential dangers in using computers, and potential dangers in using RD, and they're different. The rest is snowboards and skis.

 

[tridacna]

Dan, you’re probably correct. It may not disappear for Darwinian reasons but rather for “Kuhnian” reasons. Eventually the last stragglers will become no more and the paradigm will shift completely. I guess that we’re almost there. (Although you could argue that @boulderjohn ’s erstwhile RD buddies are perverse examples of Darwin taking care of that methodology.

 

[Patoux01]

Same with the decometre (if any). I want to establish what it ought to read, before I look at it.

In either case, to me, it's about establishing familiarity with my way home.
I think that's what's important.

Yah, except when the agency bans computers and you suggest that strongly that if one doesn't use RD (tm) then one cannot have an idea of what the computer should be reading. Then it's very hard to follow that idea, but otherwise yes, welcome to real life with divers that aren't idiots, they all have some idea of what the computer should be saying. It serves to spot mistakes, not to say "**** you, computer, I'm smarter than you".

 

[dmaziuk]

I have read that the vast majority of failures across the spectrum of electronic products occurs in the first three months of use.

Murphy's law: first three weeks after warranty expires. Couple of years ago I replaced electrolytic capacitors in a batch of wifi routers that did just that. But mostly they do indeed fail when first stressed, so everyone does "burn-in" whenever they can.

Veering further off-topic, we recently had a pair of brand new servers locking up with memory errors. Even sent one back to the vendor eventually, after replacing bits and stress-testing and all that, to no avail. Couple of weeks later their techies figured it out:
- the BIOS defaults to "smart" fan plan: fan speed is controlled by on-board temperature sensors,
- that particular motherboard has no thermal sensors under memory banks, only under CPUs.
I.e. it's not an obscure bug, it's an obscure combination of features.

 

[rjack321]

To be fair, one of the reasons the penalty is so big is because air deco is an exceptionally inefficient way of off-gassing the medium/slow tissues that you are loading up during the deep stops. Using deco gases (particularly oxygen) would make that difference much smaller.

Well sure. But on O2 the 1 hour difference is chopped down to a ~25 to 35minute difference (just wagging my finger of a guess). That still seems substantive to me for 30minutes of BT at a relatively modest depth.

 

[Dan_P]

Yah, except when the agency bans computers and you suggest that strongly that if one doesn't use RD (tm) then one cannot have an idea of what the computer should be reading. Then it's very hard to follow that idea, but otherwise yes, welcome to real life with divers that aren't idiots, they all have some idea of what the computer should be saying. It serves to spot mistakes, not to say "**** you, computer, I'm smarter than you".

But UTD has no such ban - it's clearly worked into the S&Ps that the choice of computer/algo/RD is in the hands of the instructor/students.
It's possible to do a UTD-class with a computer.
Personally, yes, I would prefer RD, but that's just a personal preference, not an agency stipulation.

I don't think it's impossible to safely dive a computer (just to be clear).
I think it's a weakness/strength of computers that they welcome laziness/complacency, just like it's a weakness/strength of RD that it really doesn't.

That's my personal opinion, and I can stand by it, but I definitely don't mean to imply that there are no divers who dive computers "the right way" (whichever way one might hold that to be).