"Riding your Computer Up" vs. "Lite Deco"

[uncfnp]

This is a mistake by that diver. If he wasn't doing it deliberately I don't think that is the behaviour which is being discussed on this thread. My understanding is that this is about deliberately doing short, back gas stops.

Not planning, and being surprised by a relatively long obligation, is not light deco, it's stupidity.

Yes and that was the point I was trying to make. Should have made my post clearer. I was hoping to show any readers not familar with "lite deco" the difference between it and unplanned, poorly managed deco.

 

[uncfnp]

So you are really getting multiple lines in the sand and choose to use the most conservative. But then you have no problem crossing that first line because you know it is conservative. So, where does that leave you in relation to the alternative lines you have that you could!d use. That is, have you really put a hard ceiling over your head during a recreational dive or are you actually pretending that ceiling is there so you can be guided through a more conservative ascent. Why not run your bottom time on a more liberal algorithm, honor that limit, and then switch to a more conservative algorithm as you begin your ascent,. That way you can enjoy whatever advantage there may be in the more conservative ascent profile with little risk of actually incurring a hard ceiling. I do suspect that a deep stop could push the liberal algorithm into deco but you could even check that on the fly if a problem arises.

Yes, I guess you could say that I do have multiple lines in the sand and I think RainPilot's post is a good way to explain it too.

As to your question on "hard ceiling" exactly where that starts is for each diver to decide. Just as more traditional deco, different algorithms will give different profiles. Which diver has the true hard ceiling?

Rather then just doing longer stops, because in lite deco that's mostly what we are discussing, I choose to use the conservative settings for the added margin of safety that it gives with consideration of other dive parameters beyond just bottom time. My dives are trip related and fairly dive intensive with multiple dives a day for often 6 to 10 days.

Speaking of which, I got to go pack for the afternoon's dives!

 

[halocline]

Yes, I could alter my behavior. That is what I’m doing. On the first dive, that’s a pretty easy thing to do. But a conservative DC keeps track of everything and suggests a second dive based on the same level of conservatism as my first dive. It calculates everything based on the level of conservatism that I want to maintain.

It also remembers and rewards/penalizes me for what I actually did on the first dive. It is more than a convenience, I don't know how I would track all that. Sometimes, I’m quite surprised at those rewards/penalties.

I'm guessing that there is a problem using conservative recreational computers and deliberately pushing them into deco. If I understand correctly how these computers work, if you go into deco they 'assume' that it was unintentional, and inflict penalties as such. IOW, the computers' algorithms assume that the diver made an error, and because of that they may add additional required surface interval time, or do something else intended to change the diver's 'reckless' behavior in unintentionally going into deco. Maybe my understanding is not correct.

If I was going into deco, I would want to plan it with a computer designed for that specifically. If I'm diving recreationally, I plan my dive according to the site, my gas supply, my interest in staying out of mandatory stops for a variety of reasons, (1. I'm not diving with tech diving buddies, 2. I don't have the redundancy for hard ceilings, 3. The charter operates within recreational boundaries, etc) and I simply add extra time at shallow stops because I know that doing so is proven effective at removing residual N2 in NDL diving. This is true for initial and repetitive dives.

It's a very simple and effective way to mitigate the risks of aggressive NDL diving with the added bonus of less fatigue post-dive.

I wonder if you guys are over-complicating the process of planning recreational dives, and using a recreational computer in a way it is not intended to be used.

There's one other point, and that is that there is an assumption that more conservative computers are 'safer' in recreational diving, but there is zero evidence to support that. Maybe someday there will be enough statistical evidence to make a claim for the safety of say, suunto computers in recreational settings, but there is none at this time.

 

[DevonDiver]

The issue that glares blindingly at me from debate in his thread is that a trained tech diver, with decent tech instrumentation and understanding of it's functions, can manipulate their dive parameters to allow satisfactory bottom-time and ample conservatism.

In contrast, the recreational diver; lacking knowledge and appropriate digital information management, is forced into horrible compromises, inanely evasive tactics to 'trick' their instrumentation and excessive risk acceptance in their quest for some mediocre payback in time underwater.

Just get properly trained and equipped for decompression diving folks... it's not so hard.

 

[guyharrisonphoto]

This, above. There is no statistical or other empirical evidence that diving a "liberal" computer within NDL with a safety stop is in any way safer than diving a more "conservative" computer and following deco obligations, on the same dive profile, for recreational diving. Conservatism is theoretical and might provide a comfort level for those who choose to use it, but there's no evidence that it reduces DCS risk in this context.

Oops, Andy posted before my reply, which was to Halocline and not to Andy's post above.

 

[lowviz]

I'm guessing that there is a problem using conservative recreational computers and deliberately pushing them into deco. If I understand correctly how these computers work, if you go into deco they 'assume' that it was unintentional, and inflict penalties as such. ...

That is an excellent observation!

Yes, the experts have said here on SB that the same algorithm can be implemented differently on different platforms. This is something to consider.

...//... I wonder if you guys are over-complicating the process of planning recreational dives, and using a recreational computer in a way it is not intended to be used. ...

Quite possibly. I may be guilty of assuming that a conservative DC and my tech DC both behave similarly in lite deco. Most interesting.

The same can be said for an aggressive DC. Is it the same if one rides the NDL up vs. just starting one's ascent at the bottom NDL? Are more penalties involved?

...//... There's one other point, and that is that there is an assumption that more conservative computers are 'safer' in recreational diving, but there is zero evidence to support that. Maybe someday there will be enough statistical evidence to make a claim for the safety of say, suunto computers in recreational settings, but there is none at this time.

Agreed.

That would make a great Consumer Reports test or science fair project, the dive industry wouldn't touch it.

 

[dmaziuk]

I'm guessing that there is a problem using conservative recreational computers and deliberately pushing them into deco. If I understand correctly how these computers work, if you go into deco they 'assume' that it was unintentional, and inflict penalties as such. IOW, the computers' algorithms assume that the diver made an error, and because of that they may add additional required surface interval time, or do something else intended to change the diver's 'reckless' behavior in unintentionally going into deco. Maybe my understanding is not correct.

That's the one big problem with proprietary algorithms: maybe it is correct. Nothing in my computer's manual suggests anything of the sort, but who knows. From the coding POV, adding conditionals for arbitrary penalties for fuzzy "bad behaviour", as opposed to just straight tracking of gas loading, is a bad idea. However, software vendors choose "feechoorz" over sense just about every time.

 

[Storker]

the recreational diver; lacking knowledge and appropriate digital information management, is forced into horrible compromises, inanely evasive tactics to 'trick' their instrumentation and excessive risk acceptance in their quest for some mediocre payback in time underwater.

Just get properly trained and equipped for decompression diving folks... it's not so hard.

Or, just choose a computer, live with its (real or perceived¹) conservatism and enjoy the time it gives you underwater. When time's up, time's up.


¹ This is something of a pet peeve of mine. I use a Suunto, and as we all know (irony alert!), Suuntos are excessively conservative. Except they aren't, for sound profiles, sound ascent rates and somewhat ample SIs. They may punish you more than other DCs for corking, or for "wrong" profiles", or for short SIs, but for the kind of diving I do, I've never been particularly limited by my computer. I'm more often limited by exposure protection, or by min gas, than by nitrogen saturation. Especially if I use EAN32, which currently is my standard gas, but not uncommonly also if I'm on air.

 

[kelemvor]

So what is the level of training and experience you need to be able to do all of this? The PADI Tech 40 class teaches light deco (up to 10 minutes) within recreational ranges, exactly what we are talking about here. Is that sort of training necessary for this kind of diving? Will boat crews publicly adapt policies that enable light deco for those with the proper credentials?

In my experience, that is entirely dependent on if the crew also sells training such as Tech 40. If they don't then they probably won't care.

 

[stuartv]

Just get properly trained and equipped for decompression diving folks... it's not so hard.

It may not be so hard, but around here it is effing expensive! Buy or rent doubles and a deco bottle, a couple of extra regs, an extra computer or bottom timer, maybe a BP/W, etc.. And then course tuition anywhere I've checked runs around $1000 for TDI Adv Nitrox + Deco Procedures or equivalent.

Seems like a lot to just flippantly tell a person who dives 10 or 20 dives per year to suck up when they go on vacation to FL or the Caribbean once or twice per year (yet still wants to maximize their bottom time when they do get to go).