First Dive Computer

[KenGordon]

Could you let me know why you are dismissive of ScubaLabs study?

All the computers could do all the dives. So it doesn’t matter which computer a diver used in that test.

They used a metric ‘NDL’ which is mathematically very sensitive. Very small changes in input result in large changes in the metric. So the EXACT dive profile is greatly magnified. Likely as not going a couple of m shallower a little earlier on a ‘conservative’ computer would increase the NDL by a large percentage.

If you want to know how conservative or aggressive a computer is really then do a deco dive and see how long the stops are. Long stops mean a lower surfacing oversaturation and less risk, so more conservative.

 

[scubadada]

All the computers could do all the dives. So it doesn’t matter which computer a diver used in that test.

They used a metric ‘NDL’ which is mathematically very sensitive. Very small changes in input result in large changes in the metric. So the EXACT dive profile is greatly magnified. Likely as not going a couple of m shallower a little earlier on a ‘conservative’ computer would increase the NDL by a large percentage.

If you want to know how conservative or aggressive a computer is really then do a deco dive and see how long the stops are. Long stops mean a lower surfacing oversaturation and less risk, so more conservative.

We're talking about recreational diving, you keep confusing the issue by bringing up deco diving.

 

[KenGordon]

We're talking about recreational diving, you keep confusing the issue by bringing up deco diving.

It is all deco diving. Your DSAT computer will allow no stops on a dive that would have stops on a Suunto. What is the difference other than marketing?

 

[scubadada]

It is all deco diving. Your DSAT computer will allow no stops on a dive that would have stops on a Suunto. What is the difference other than marketing?

Free access to the surface without stops, good enough for you? Or, would you ignore the Suunto stops, knowing that you are diving a "conservative" computer? It's more than marketing, don't you think?

I was diving in Jupiter, Florida today, 2 reasonably aggressive dives. One diver showed his computer to the DM at the end of the dive. They stayed down together for at least 5 minutes after the rest of us had completed our safety stop. Turned out he had put his Suunto into deco without being aware of what that meant. Ignorance is completely another topic.

 

[scubadada]

@KenGordon and @dmaziuk

What are the obvious advantages of a conservative deco algorithm that I seem to be oblivious of?

 

[KenGordon]

Thi

I was reminded today of a post from Newbie Stu (thank you, @peterak) that seem relevant to this thread:

So you want to buy a new computer?

This is a post about how you can get to your DSAT NDL using a cylinder 50% bigger than a typical holiday diver’s one.

Seems to me that you are confirming the assertion that other limiting factors need to be overcome before NDL is a serious issue.

Free access to the surface without stops, good enough for you? Or, would you ignore the Suunto stops, knowing that you are diving a "conservative" computer? It's more than marketing, don't you think?

No, I don’t ignore Suunto stops. I am saying that all dives involve deco and that the distinction between no stop,’recreational’ diving and stops on ‘technical’ diving is about marketing. Making ‘deco’ diving something other than ‘normal’ allows ‘normal’ diving to be extended down to people with only a few days to learn and enables the whole ‘learn on vacation’ experience.

Serious divers will realise that they can bend the rules to do the dives they want, or they can do a little more training and do the stops if they want longer dives. It is an accident of history, better marketing if you like, that meant that the dominant training system excluded doing stops. The rest of the world is quite relaxed about it.

 

[KenGordon]

@KenGordon and @dmaziuk

What are the obvious advantages of a conservative deco algorithm that I seem to be oblivious of?

Probability of getting hurt.

 

[scubadada]

Probability of getting hurt.

Please share with me the data that any conservative deco algorithm is safer than any more liberal algorithm when used for recreational diving.

 

[scubadada]

Thi

This is a post about how you can get to your DSAT NDL using a cylinder 50% bigger than a typical holiday diver’s one.

Seems to me that you are confirming the assertion that other limiting factors need to be overcome before NDL is a serious issue.


No, I don’t ignore Suunto stops. I am saying that all dives involve deco and that the distinction between no stop,’recreational’ diving and stops on ‘technical’ diving is about marketing. Making ‘deco’ diving something other than ‘normal’ allows ‘normal’ diving to be extended down to people with only a few days to learn and enables the whole ‘learn on vacation’ experience.

Serious divers will realise that they can bend the rules to do the dives they want, or they can do a little more training and do the stops if they want longer dives. It is an accident of history, better marketing if you like, that meant that the dominant training system excluded doing stops. The rest of the world is quite relaxed about it.

Your BSAC bias keeps shining through. Remember that this is a thread on 1st computer purchase by a newly certified diver. As before, you keep confusing the main issue by injecting deco diving into the mix. Please try to stay on topic.

 

[dmaziuk]

We prefer in this report to refer to dives without stops as "no-stop" dives, to avoid the implication that decompression is not involved; it always is.

-- R.W. Hamilton et al, The DSAT Recreational Dive Planner, Development and validation of no-stop decompression procedures for recreational diving, 1994 Feb 28, pp. 7, section II.C. 3.

It is important to keep in mind that although these ascent-limiting M-values are handled as specific "hard" numbers, the experience behind them is that they belong to a spectrum of gradually increasing risk. A given set of M-values clearly does not mark a hard edge beyond which DCS is sure to occur below which it is guaranteed not to (regrettably, this idea does not exist in the minds of many divers).

-- Ibid, pp. 14. section III.B.3. (emphasis mine)

There's a whole section II.C.6 titled "Safe or reliable; DCS is not an accident" in there, too... I think the difference in our diving styles is I've actually read this stuff and I (usually mostly) comprehend what I read.