DIR and computers

[diverbrian]

I dive a VyTec and use it for what some people call "Hard Deco".

I also look at every dive profile when I am done and look at the theoretical nitrogen loading. Like my Cobra (my back-up which I keep in gauge mode for this kind of diving as it doesn't show my gas switch to EAN50 at about 60 ft as I come up), it will show a ceiling of 10 ft to start with and extend it down. It will actually start ticking off deco at about 50 or 60 ft. You can tell this underwater as that is when the "ascent time" window actually quits increasing and starts ticking down. In other words, the Suunto Computers figure that at 50 ft or so as you come up you are off gassing. If you want to come up slowly, there is no additional deco obligation incurred and you actually are starting your deco stops.

This is the reason that I dive the tables as they spell out my deco stops. But, on a shipwreck type dive, the VyTec and my IANTD tables match up quite well. I also tend to stay down another 2 minutes or so at fifteen feet or so just to wait for people to get back on the boat and think about the dive (also known as relaxing ). But I don't see where the Suunto's penalize me for coming up slowly. Follow the nitrogen loading sometime on a theoretical dive (using their download software) and you will see what I mean.

Again just my humble two cents worth. You are all welcome to take it or leave as you wish.

 

[GreenDiverDown]

MikeFerrara once bubbled...


What i'm going to say here doesn't have anything to do with DIR or GUE but...

Stephen, run through some dives on your tables. Look at the RNT after a reasonable surface interval like 1 - 2 hours (whatever you like). What is the penalty for different depths? Can you come up with a rule yourself that will fit the vast majority of situations like mabe considering your depth a few feet deeper or your time a few minutes longer on the second dive? Combine that with good profiles and good ascents and do you think you could pull it off without a copy of the tables in your hand?

Besides if you had an average (profile) depth and a time couldn't you calculate a pressure group if you wanted to?

All they did was sit down and really look at the tables realizing that with good habits it didn't have to be calculated to the inch and the second and came up with a simplified procedure.

The answer is is pretty much on the tables. Any one have any experience with algorythm design?

Thank you...thank you...thank you...thank you....thank you...thank you...thank you...thank you...thank you...thank you...thank you...thank you...

SA

 

[Wyno]

Stephen Ash once bubbled...

Anyway...let me try to clarify what I meant by "Until DIR is ready to share these things most folks will have a hard time believin' that they don't need their tables or computers."

I'm NOT saying that unless you give it away for free on the internet people will have a hard time believing it. What I AM saying is that people can't toss away their tables or computers until they understand the whole deal. I bet you would agree with that. Speaking for myself, I expect that there is a better way. I believe guys like you know the score. But I can't stop doin' what I'm doin' til I figure out that other way.

Let me put it another way...again speaking as a friend...folks won't understand that there is a better alternative to computer diving unless they understand what that alternative is. If they can only get that in a DIRF with a certain instructor then only those folks that take that class will understand that alternative.

Its tough to take the position that there is a better way to dive when you can't discuss just exactly what that better way is. Do you see what I'm saying?

Ya know...if this stuff was in "the book" it would make talkin' about it much easier.

Mike,

People will pay to take the class because you teach it. They will pay to take the class because they will get quality training. The folks that take your free tid bits and run aren't gonna pay to take the class anyways.

SA

My thoughts and better put then I could have done.

Mike,

I too will be taking GUE classes but it doesn’t sound as if I’m going to learn the 120 rule there either I would have to pass and take yet another class to learn it, at least from what I have heard.

Dan

 

[Uncle Pug]

Stephen Ash once bubbled...
Thank you...thank you...thank you...thank you....thank you...thank you...thank you...thank you...thank you...thank you...thank you...thank you...

as the light comes on.

 

[Rick Murchison]

After seven pages of posts and well thunk thought, I have decided I'll plan my dive, dive my plan, and carry my computer.
Rick

 

[Custer]

David Evans once bubbled...
Here are just a few flaws of using a computer (I use the Suunto Vyper and Stinger):

1. I had my Stinger on in the pool for a class two weeks ago. I managed to get down to a depth of 12 feet at the bottom of this particular pool. My Stinger didn't want me to fly for 12 hours afterwards.

2. If I do a dive to 20 feet for 1 minute, my computer wants me to stop for 3 minutes at 15 feet. If I dive to 90 feet for 20 minutes, my computer wants me to stop for 3 minutes at 15 feet.

3. On exactly the same profile: If I get into deco in Cancun, my computer figures I need the exact same deco stops as I do on the same profile in the Puget Sound (despite the fact that both computers know the water temperature).

Modern science on the subject shows that all three of these suppositions by the computer are incorrect.

Actually, what it shows is, either you didn't read the manual, or don't understand what a default is.

It's funny that you apparently avail yourself to "modern science" to prosecute a problem that doesn't even exist.

What this is, is, the perfect example of what other people cite, dependency on a computer when you don't understand how it works.

In a nutshell, the computer doesn't make decisions. It provides you with information with which to make decisions.

 

[Custer]

Uncle Pug once bubbled...

1. Yes you are... you are missing what is being said about there being something other than either tables or computers. Now it may be intentional on your part... but that is something else altogether.

2. Saw tooth dive profiles are proscribed by common sense... and most agencies that I know of.

Like I said, guessing at your deco status works ok when you limit your dive profiles.

Just out of curiosity, what common sense and dive agencies can you cite on this?

 

[diverbrian]

I will back him up with at least one agency. The SSI Deep diving and DiveCon manuals address the lack of safety in sawtooth profiles EVEN WITH A COMPUTER.

The IANTD Tech Diver's Encyclopedia doesn't address the issue directly but has a similar (albiet more wordy) take on decompression theory. Due to the fact that tissue loading is not linear, the ideal dive profile from from a DCI prevention standpoint is do the deepest dive first in the day and the deepest portion of the dive first to allow for more off gassing in the shallower "end" portion of the dive.

This is the common sense that Uncle Pug refers to. And I have listed two agencies that really don't approve of sawtooth profiles that are not GUE.

If you take into account that DIR divers are using a standard mix, dive a disciplined profile, and are supposed to be the best possible physical condition (read Tom Mount's stuff on the disciplined profiles and physical conditioning, he preaches this as well) with the best possible health habits, this would appear to remove many variables and allow for the safe use of "thumb rules."

I can attest that thumb rules work for standard "on the fly" work as we used them in nuclear power for standard operations and only calculated them out fuel usage at the end of the day. Guess what? Our thumb rules weren't that far off.

 

[James connell]

Rick Murchison once bubbled...
After seven pages of posts and well thunk thought, I have decided I'll plan my dive, dive my plan, and carry my computer.
Rick

the ONLY intellegent post to date on this thread - i'm not suprized.

 

[David Evans]

Custer once bubbled...



Actually, what it shows is, either you didn't read the manual, or don't understand what a default is.

It's funny that you apparently avail yourself to "modern science" to prosecute a problem that doesn't even exist.

What this is, is, the perfect example of what other people cite, dependency on a computer when you don't understand how it works.

In a nutshell, the computer doesn't make decisions. It provides you with information with which to make decisions.

Custer:

First, I assure you that I have a very deep understanding of how both the Stinger and the Vyper work, along with quite a few other models (I have to, as I work in the dive industry as an instructor). I understand the different user settings, and levels of coservativism, and the differences in Suunto's "RGBM" and Weinke's "real" RGBM. I also know a fair amount about Haldane and Buhlman's models. You would do well not to assume so much about people you don't know.

You would also do well, in my opinion, to try to refute my statements (which are absolutely accurate) rather than try to discredit me.

I can't really tell what you are advocating here - on the one hand, you seem to be advocating using a computer as a reliable dive planning tool. At the same time, you seem to be advocating using your brain to moderate what the computer is telling you.

Which is it?

Either you trust the computer, or you don't.

Either the computer is an accurate dive planning tool, or it's a guideline.

Which is it?

If the computer is an accurate planning tool, then I encourage you to explain to me why I need to not fly for 12 hours after spending 20 minutes at the bottom of a 12 foot deep pool.

If the computer is just a guideline, then I encourage you to explain how can I possibly trust it to calculate my decompression.

Please, Custer, oh, wise one in the way of computers, explain this to me.

Is my computer an absolutely accurate tool for dive planning?

Or is it merely a guideline that I should use, but not totally trust?

If I can't totally trust it, then what lesson(s) should I learn from that with regard to planning and executing my dives?

And if I can't totally trust my computer, what can I carry with me on my dives that I can totally trust?