PADI tables finally going away?

[caseybird]

Agreed. (snip)

Thus, not only you would have to teach the use of each specific computer, as for each computer you would have to teach different ways of diving according to it's underlying degassing theory.

Not only that, people with different computers would not be able to buddy properly, at least regarding the ascension.

At this point, I believe we are overestimating the complexity of NDL diving.

 

[Kingpatzer]

No, the tables are not "completely obsolete" and I seriously doubt they ever will be. There will always be those of us who would rather not go blindly about, letting a machine do all our thinking for us.

I was going to respond to this, but I decided instead to go for a dive. Just sitting at the computer while vplanner prints out my table.

 

[AfterDark]

I was going to respond to this, but I decided instead to go for a dive. Just sitting at the computer while vplanner prints out my table.

Well good luck with that. I'm in Paladin’s camp on this. I plan my dives with the US Navy air tables modified by me for me. If my PDC shows less time at a stop than I've calculated with my modified tables, I go with my numbers. The PDC has yet complain but this will only be the second year I’ve used a PDC, mainly because some ops here are started to ask for one. This has worked for me for 40 years I ain't changing now.

Just last week someone offered the use of their software to plan my dives for me. Thanks but no thanks. I’ll do it myself.

 

[notivago]

I have no idea what you mean here.

It is true that when dealing with no decompression diving, different computers with different algorithms will give different NDL times, but as is taught in every OW class, even ones that teach tables, you simply go with the most conservative computer in a buddy team.

It does not matter whether you are using tables or computers--it is likely during part of an ascent that some of your tissues will be ongassing while others are offgassing. That's due to physics and is true no matter how you are measuring your dive.

I have absolutely no idea what you mean when you say people would have to teach different ways of diving. Can you give an example?

I thought I had given the examples. But, let me try to rephrase it, let's consider two computers, one will be the same model as mine, an Excel 3, I don't know which model it uses, but it is the classic ascend and stop model for degassing, anything bellow the degas area(~5m) is on gassing.

The other is the Suunto tha uses the model I linked in the other post, it uses a model were you make an gradual ascension were the degassing occurs in stages, the diver must ascend in such a way that makes him always inside an area delimited by an floor and a ceiling which are calculated by the computer according to the model.

Now lets buddy two people with those computers, they dive till near the NDL and decide to ascend, but which is the proper way to ascend to keep budding? As they are near the NDL, the excel will penalize it's user for ascending slowly with the Suunto, but if they ascend in the conventional way the Suunto will shut and will refuse to play anymore.

At the stop site the excel will demand a greater stop due to the ascend which for it was on gassing whilst it was degassing for the Suunto which will possibly award extra credits for it's diver for degassing.

Also, if you read the paper, you will see that Suunto do not consider varying level as just the sum of the different levels, it penalize the diver for changing depths as it(according to the chosen model) causes nitrogen bubbles that become difficult to expel from the divers body.

So certain classic rules are different if you dive with certain computers, in the case of the Suunto, the rule for degassing is not ascend and stop for 3min at 5m, it is ascend as the computer tell you to do. On the other hand it is valid for the Excel.

The rule: dive according to the more conservative computer becomes muddy as the models become complex as it become difficult to judge what is more conservative, the the example case, who is being conservative regarding the ascend? The Suunto or the Excel? For the Excell the slow ascend puts its user dangerously near the NDL as for him it still counts as on gassing. But for the Suunto to ascend faster would put it's user at risk as the nitrogen bubbles(according its model) would be forming too fast and becoming too big to be expelled.

Some can say that the best would be slow ascend plus stop would solve the problem, but it may be that for a sum of factors the Excel user really is too close to his NDL, due for example to a deeper dive profile and what if the slow ascend puts him in NDL?

There is no such thing as dive according to the more conservative computer if they are different, for being conservative for one can be risk taking for the other, this is a loose rule that only really hold if you take in account simple factors like different depth profile and water temperature.

In the example given, the only way to guarantee proper ascension would split the buddies, something that I particularly dislike, I am all for if you are budding you dive together all the time.

Also, if you look at the example given, the Suunto model is a clear case were what is taught in the OW regarding ascension does not hold, so if you are teaching a class to use this computer in particular, you wont teach the classic ascension and safety stop, you would teach gradual ascension. You would also teach that an square profile gives you more bottom time than varying depth profile.

If it were a class about E3, you would teach ascend and wait for computer clearance and that a non square profile would give you longer bottom time than if you did all your dive at the max depth.

It is true that in decompression diving, using different computers CAN break up a dive team if they give different times at different stop depths, but almost all modern decompression computers will allow you to overcome that and follow the more conservative computer. This thread is also not about decompression diving. If you are interested in how to dive different computers in decompression diving, there was a thread on that topic recently in the tec diving forums.

I guess I am many years away from decompression dive, one step after the other and let's make them baby ones. =)

 

[notivago]

At this point, I believe we are overestimating the complexity of NDL diving.

Am I? Have you read the Suunto paper on the model they use? The degassing theory they use is actually different from the traditional, or it is a updated version if you like, and would change the way you ascend and degass, also they consider that changing depth during the dive hardens degassing and take that in account for theirs model, contrary to other models in which you extend you NDL by varying depth, more precisely it give you less credit for changing depth.

 

[Blackwood]

Am I? Have you read the Suunto paper on the model they use? The degassing theory they use is actually different from the traditional, or it is a updated version if you like, and would change the way you ascend and degass, also they consider that changing depth during the dive hardens degassing and take that in account for theirs model, contrary to other models in which you extend you NDL by varying depth, more precisely it give you less credit for changing depth.

I believe what Caseybird was getting at is: the model being fundamentally different doesn't change how most folks execute these types of dives: putt around and ascend when you approach NDL to whatever margin you choose. If you buddy dive, putt around and ascend when the first buddy to hit that margin does so.

RBGM may credit NDL on ML profiles less than Buhlmann, but that doesn't change the generic approach.

If the algorithms were directing a buddy team to ascend in different schedules your point would be key, but that isn't the case within the realm of "recreational" PDCs.

 

[notivago]

If the algorithms were directing a buddy team to ascend in different schedules your point would be key, but that isn't the case within the realm of "recreational" PDCs.

If you look closely on the algorithm I mentioned you will see that it is exactly what happens, the way you ascend for the Suunto is different from the traditional. There are other cases for example, there are instances were the computer credit you for doing a stop at mid max depth and then other at 5m while others consider the stop at mid max depth as being on gassing, those computers would disagree on the ascend schedule and the mid stop one disagree with the regular procedure taught in OW courses.

 

[windapp]

If you look closely at the algorithms for all the computers, I think you will find that every one of them has you on-gassing for unsaturated tissue compartments, and off-gassing for supersaturated tissue compartments. I am pretty sure that this is not unique to Suunto.

If you and your buddy are both in decompression mode, and you are using computers that are that different, it means that one of you went into decompression mode, and ignored it long enough for the other one to also go into decompression mode. At this point, it doesn't matter how much penalty a computer is giving. Your diving should be over for the day anyways so the penalties are irrelevant.

 

[Blackwood]

... There are other cases for example, there are instances were the computer credit you for doing a stop at mid max depth and then other at 5m while others consider the stop at mid max depth as being on gassing, those computers would disagree on the ascend schedule

NDL computers don't give you an ascent schedule at all (mandatory decompression notwithstanding); they react to yours by adjusting remaining NDL.

That one computer may credit my NDL differently than than another isn't particularly relevant within the NDL paradigm.

An RGBM computer diver is no less compatible with a Buhlmann computer diver than is a PADI table diver with a NAUI table diver.

 

[windapp]

I think you will find that a lot of dive equipment manufacturers use very fancy terms that mean pretty much the same thing as what everyone else is doing. If you were to read the Mares airtrim manual, and never be exposed to any other form of BCD, you would be under the impression that the airtrim BC is the only one that allows you to cut off the air to a freeflowing fill-valve by disconnecting the inflator hose.