Past NDL. And then this???

[tursiops]

Several times in this thread DSAT has been mentioned in the context of being "liberal" and "aggressive." Actually, to the extent there is any truth in that, it is only for dives within the NDL, which is what the algorithm was designed for and validated for. Once you go into deco, the algorithm backs way off and forces long deco stops compared to other algorithms actually designed for deco. I suppose the algorithm becomes super conservative for deco mostly because it is not intended to be used that way.

 

[BRT]

And that is known how?

Because it can be retro-modelled until a sufficiently liberal algorithm is found that would have kept it out of deco?

If he'd had a liberal algorithm, so what??

Mindset would have remained aggressive.

He'd have still have dived three times per day ... pushing NDL on every dive... until EVENTUALLY a lapse of awareness pushed him into cascading slower tissue decompression.

So... same outcome... but instead he'd have been on a liberal algorithm that afforded him much less forgiveness for his dilemma.. and may have led to a different (more painful, and expensive) outcome... .

You can change the numbers 'problem' ... but you aren't changing the real-world inert gas dissolved in tissues problem...

Mindset versus Algorithm

A LIBERAL (aggressive) algorithm combined with a LIBERAL mindset affords you very little capacity for error or ill-luck.

If you dive a LIBERAL (aggressive) mindset, you're better protected by a CONSERVATIVE algorithm.

Vice versa, if you're inclined to be a disciplined and CONSERVATIVE diver in attitude, then you afford yourself the option of using a LIBERAL algorithm without negative consequence.

Yep. He would have dove just the same way, along with the group he was with who did not exceed their NDL's.

 

[scubadada]

Several times in this thread DSAT has been mentioned in the context of being "liberal" and "aggressive." Actually, to the extent there is any truth in that, it is only for dives with the NDL, which is what the algorithm was designed for and validated for. Once you go into deco, the algorithm backs way off and forces long deco stops compared to other algorithms actually designed for deco. I suppose the algorithm becomes super conservative for deco mostly because it is not intended to be used that way.

Absolutely correct

 

[DevonDiver]

Yep. He would have dove just the same way, along with the group he was with who did not exceed their NDL's.

... and this is why most computer manufacturers do their best to take the harmful decisions out of diver's hands.

There's no greater feeling that sitting in a chamber enjoying your third $18k hyperbaric treatment with a smug self-satisfied grin from knowing you were inside your NDL... right?

It's worth remembering, that the aim of any diver, computer or algorithm is to avoid DCS... not NDL.

Divers shouldn't get those two abbreviations mixed up in context.

 

[drrich2]

That user error was greatly exacerbated by an over-confidence and complacency empowered by an internet browser quasi-education.

This lesson wasn't learned at the time - hence the mistaken quest for 'clarity' in the OP... more internet browser quasi-education... that, again, illustrates little comprehension of where things actually went wrong.

The CLEAR lesson is to respect what you are actually TAUGHT at your level of diving... and have the disciple and moral courage to restrain yourself within those limits.

A secondary lesson is that dive operators can act very irresponsibly at time. The DM leading that dive absolutely failed to act to protect your safety and further endangered your safety with his "clearing your computer" shenanigans.

If the 'DM leading that dive' was a true Dive Master (not a guide mislabeled that), then while not an instructor (although many guides assumed to be DMs are instructors), one could get taught 'rule breaking' by a professional. Consider what another poster noted (not clearly rule-breaking, but I think a bit similar):

I had a DM on a dive boat in Cozumel admonishing all of us to set our computers to the most aggressive setting, because he didn't want anyone to go into deco *sigh*.

Again, true DM, or maybe even instructor?

I get what you're saying about respecting the limits set for a given level of diving, rather than deliberately transgress them before getting the training for that to be an informed decision. I wonder how rare it is for someone getting formal instruction to be advised in an unduly risky way, much as can happen with an internet browser 'quasi-education.' The text book should give right info., of course.

Another point of potential confusion is that some 'limits,' such as a 60 foot max. depth for fairly new OW graduates, and 100 feet for AOW, etc..., are often seen as starting recommendations pending further training or experience (which raises the 'you don't know what you don't know' concern). NDL limit recommendations it's highly advised to abide by. I wonder how well most recent OW and AOW weigh those distinctions?

Richard.

P.S.: I'm not dissing formal training or proposing online browsing as a substitute. I think the latter can complement the former & help people learn.

 

[Asteve]

Here a review I wrote on the CRESS LEONARDO over 2 years ago
Review of the Cressi, Leonardo underwater dive computer.

I have posted some of the warning here I talked about.
It has been asked if the manual was read. It may have been but it was not followed.

Page 5 “WARNING: this instrument is designed to be a dive aid and does not replace the use of the dive tables.”

I have read that tables are being dropped from the OW curriculum, therefore, your training will not allow you to use this computer. If this DC is an aid for dive tables, I can not find any tables that are more conservative than this DC, so how is this DC going to aid me in following the tables, I would put this DC into 48 hours lock-out all the time. Why have it? Why would an aid disable itself?

Page 6 “WARNING: While diving, be equipped with a depth gauge, a manometer, a diving timer or watch and dive tables. Please always check your diving cylinders’ pressure to be fit to the planned dive and, while diving, often check the cylinders’ air capacity by means of your manometer.”

How many of you dive with a manometer? Poor translation.

Page 9: “WARNING: Currently, no validated scientific literature allows to dive more than twice a day for periods of one or more weeks without the risk of decompression sickness. For your own safety, it is important to avoid diving for more than two times a day. A rest of at least 2 hours between two subsequent dives is mandatory. The next/repetitive dive shall be shallower and its minimum duration shall be 15 minutes.”

So to use this computer you need dive tables.
It not for more then 2 dive a day
It need a 2 hour time before dives.

Well I have beat the horse enough. I replaced this dive computer

Now to the diver.
You have taken a beating for try to find out what is wrong and what you need to change. You have gotten a lot of good information.
Continue to ask question, that the only way to learn.
This was a bad computer for the diving you were doing BUT You need to follow your instrumentation. ( get a new diver computer ).
You had no system to call the dive. Or you were not willing to call the dive. You were to slow to get to your dec stop.
Once you were headed up you should keep going and not stop to look at something.
Thanks for posting this.

 

[Centrals]

Computer is just a tool, no more or no less. It is the diver responsibility to use it correctly.
Reading the manual is never enough if you do not understand it.
Even an aggressive/liberal computer will get into DECO. Then what?
Follow the instruction given by the computer diligently otherwise give it away and buy different one. Never ever blame the computer but yourself.

 

[KeithG]

The whole trip was on subsurface as downloaded from my computer! I know that surface intervals make huge difference in all these.

Thanks a lot guys. I got to go get some sleep for now.

It was a pleasure and I hope by tomorrow I will have plenty more replies to study.

You should also look into Subsurfaces capability for displaying NDLs - I am very new to Subsurface so I do not know the answer to my question below.

My computer does not download NDL data into subsurface, just the dive profile data. Subsurface then recalculates NDLs using its own algorithm and settings. The subsurface defaults did not match my computer, so the NDL data it displayed did not match what I saw under water.

Is your computer (or any?) capable of downloading NDL data to Subsurface? Or is is always recalculated?

If your computer is like mine (no NDL data) you will most likely have to alter Subsurface algorithm preferences in order for it to provide NDL calculations that match your computers behaviour. Otherwise, subsurface will be providing misleading data as the NDL times can vary widely based upon the algorithm and settings.

 

[doctormike]

Yep. He would have dove just the same way, along with the group he was with who did not exceed their NDL's.

I don't understand. Are you saying that if he had a more liberal computer, he would have been less likely to get bent doing the same profile?

 

[BRT]

I don't understand. Are you saying that if he had a more liberal computer, he would have been less likely to get bent doing the same profile?

I'm saying the other people he was with did not exceed their NDL's and were not bent. He dove the same dives and had over 1/2 hr decompression. The problem was in the computer not in the dives. Get a different computer.