Deco on Dives in Coz? Educate Me

[georoc01]

I think what we are really talking about here is planned vs unplanned Deco. In the case of the former, you know what you you're deco schedule is before you hit the water and have done the appropriate gas planning to complete the dive.

When its unplanned and letting your computer define the deco, you are at its mercy as far as how much time you need to spend underwater to safely complete the dive. It may be nothing, it may be well beyond the amount of gas you have remaining.

I dive with computers, and they are a great tool, and when it comes to Deco, they are a great backup to my planned dive schedule for when things don't go as planned. But depending on them for your deco schedule is risky. Is one minute worth of deco time, if honored on your computer going to be dangerous? Probably not.

When we dove Punta Sur, I was last to go through the swim through. The divers who went first and then waited for everyone to complete had a small deco obligation. Those of us who were last did not. Did it create a problem on the dive? No, but its something to be aware of when diving deep.

 

[ianr33]

Isn't it likely that once pushed into deco, different computers will be asking for different stops for different amounts of time? Shouldn't all deco stops be followed to completion as asked by that individual computer?

Thanks

Yes,different computers will go into deco at different times,and once there will ask for different length stops.

BUT..............When first into deco the requested stop is going to be 10 feet. As you stay at depth the time required at 10 feet increases. Eventually the computer will need a 20 foot stop.
HOWEVER...........If your computer gets as far as needing a 20 foot stop on a recreational dive you are no longer "just a little over NDL" You are being truly stupid and deserve anything bad that happens to you!


SO...If computer goes into deco,start a slow ascent,do deep stops if you want and DO NOT exceed the ceiling.Stopping at 15' would be good.

Of course,if you run out of gas on your deco stop you have a problem,which is why going into deco in the first place is not a bright idea unless you are planning for it.

 

[TSandM]

Okay, so now we have a definition: A "decompression" dive is a dive where YOUR computer goes into deco.

I would seriously hope that this discussion makes a number of people sit back and think about what their computer is doing, what the NDLs ARE, and what it means when you "go into deco". I am sort of hearing a tendency toward people feeling that their computer is doing something arcane that they can't understand, but they'd better obey it. If you are going to ride the NDLs, or exceed them, you really should have much better understanding of what decompression algorithms are doing, what the computer is saying, why it's giving you the stops it is, and how much gas it takes to complete your obligation.

There is nothing magical about staged decompression diving. But doing it blindly is not very smart. I like the "poking a sleeping bear with a short stick" analogy.

 

[Mr Carcharodon]

Everybody should also be aware that the algorithms in recreational computers are NOT designed to create a valid profile for staged decompression diving.

Really, what are they doing then?

Admittedly most of the dive computers manufactures are obtuse about what they are doing. But as far as I know all computers out there control ascents based on critical pressures, or volumes. Both of which should work for staged decompression. Can you give an example of a computer that does not work this way? Of course you are right that if you do not know what the ascent will look like gas planning becomes impossible.

 

[FishOutUvH2O]

Okay, so now we have a definition: A "decompression" dive is a dive where YOUR computer goes into deco.

If you like that definition and it works for you, run with it. However, I'm going to stick with a different definition. The one that defines a "decompression dive" as a dive that has required decompression stops. I'm also going to stick with my type of dives, which are "no-decompression dives".

How many people actually know, or even care what decompression model and data base their computer uses to calculate their NDL's?! I don't know. I would venture to guess very few. Should they know?! Yes. Do people need to know?! Maybe, maybe not. While it's obvious that there may be some debate on the definition of some concepts. I have no disagreement that people need to understand that, regardless of whether or not your computer is conservative or liberal, coming close to or exceeding any of their NDL's means that, at a minimum, you're pushing any current standard for NDL's. And at least be aware of what the risks are for pushing those limits.

 

[TSandM]

I now officially have my head in my hands.

A decompression dive is one with mandatory decompression stops. I agree.

But your prior answer indicates that, if three divers do the SAME dive and one has a computer indicating mandatory deco, that dive is a deco dive for THAT diver, but not for the others. Which is why I said, "A mandatory deco dive is one where YOUR computer goes into deco."

You're making my head spin.

 

[FishOutUvH2O]

I now officially have my head in my hands.

But your prior answer indicates that, if three divers do the SAME dive and one has a computer indicating mandatory deco, that dive is a deco dive for THAT diver, but not for the others. Which is why I said, "A mandatory deco dive is one where YOUR computer goes into deco."

You're making my head spin.

Unfortunately, that's a side-effect of both applying in practice a theory with varying models, and then having so many computers running different algorithms, coming up with different NDL's. Since, we individually dive (and hopefully are paying attention to) our own computer it becomes possible for one individual in a group to suddenly be doing a decompression dive while others aren't. If I push my computer's NDL's and it goes into deco-mode, giving me a mandatory stop, then I'm now doing a decompression dive while others aren't. That was actually part of the OP's original question. Which is referring to unplanned, or poorly planned, decompression dives.

. . . Isn't it likely that once pushed into deco, different computers will be asking for different stops for different amounts of time? Shouldn't all deco stops be followed to completion as asked by that individual computer? It seems like this might make staying together as a group a bit more difficult.

 

[TSandM]

Okay -- so you're willing to consider any given dive to be possibily a decompression dive or not, depending on which computer evaluates it. I'm okay with that. And I totally agree that having a team diving different algorithms is a recipe for irritation at best, or serious problems at worst.

 

[FishOutUvH2O]

To be nitpicky. . . I simply adhere to the definition. Why do I think the definition is that important? Well, I'm glad you asked. . .

Because it circumvents any arguments that may be made in the post dive "discussion" about whether or not a deco-dive occurred. I don't do dive plans for decompression dives. So, by extension, I don't want to do deco-dives. I'm not that well trained and I don't have the equipment. So, if for some reason, I or my dive buddy end up with their computer going in to deco-mode then we blew the "no-deco" dive plan, and back at the surface we need to know why. What I want to avoid are the arguments like; "well, it was only for a minute", "I didn't have that much deco time", or my favorite, "It cleared before I got to my safety stop". Or any other, "for this reason" it wasn't a deco-dive excuse. It either was or it wasn't. Luckily, my wife is my buddy and she dives the more conservative of the computers. So, it's her computer that tends to dictate the dives NDL's. And she's somewhat of a stickler for paying attention to her NDL's, so any of our computers going into deco-mode almost never happens. . . Almost never.

 

[craracer]

Cavalier.

Yes my friend, it truly is a pretty tree, but have you noticed the forest?