DIR and computers

[Custer]

diverbrian once bubbled...
Ask and ye shall receive
SSI Dive Control Specialist Chapter 7 pg 8
quote:
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If diver goes to the deepest depth first, and proceeds to successively shallower depths, then multi-level diving can be safe. If divers alternate between deep and shallow depths, however, then it is less safe. The reasons why are complex and have to do with the solubility of gases under pressure, but to illustrate in simple terms, imagine a sponge absorbing water. Sponges absorb water in varying amounts, but at some point will be saturated---they will hold no more water. The tissues at increased pressure are much like sponges; they will absorb nitrogen until they are saturated (for that pressure). At reduced pressure, tissues release nitrogen. If they are resubjected to increased pressure, they will again absorb nitrogen, but the residual nitrogen will affect that process."
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I will grudgingly concede this point, even though there's no reference to computers (as you noted).

I would certainly like to see the paragraph before and after.

diverbrian once bubbled...
As to how that affects decompression diving: Pg 7-11

<snip>

SSI Deep Diving Manual Appendix four AAUS Recommendations

<not sure what this was in reference to>

As for the rest of your post, you remind me of me.

I'm just pointing out that their way of diving, guessing at deco, works fine for the profiles they limit themselves to.

My computer takes your aforementioned onloading/offloading cycles into account.

Their method can't.

I'm not the one making the point that those who use computers are too stupid to dive any other way (that would include you, BTW).

diverbrian once bubbled...
Thank you for refreshing my memory. I am sure that I could find more direct references upon request about SSI's view an a proper dive profile. Obviously, I DO engage in limited staged Deco diving. I don't do that with SSI.

And you are correct that my IANTD training really isn't about my NDL diving (which by strict definition is still deco diving, even according to SSI). And neither agency will cut up a card issued if a diver chooses not follow all of their recommendations. I will never be in the physical conditioning of a top notch tech diver, not drink caffiene or alcohol ever, eat a perfect diet, etc. This is why I am not DIR. I applaud the divers with the discipline to live that way. I don't choose to.

I dive a computer (actually two of them). But, I temper the use of it with common sense. Computers are only as "perfect" as the person who programmed them in the factory. A quick "idiot check" in many aspects of life would prevent many mishaps. I don't wish to completely trust anyone that could have come in with a hangover on Monday morning because their favorite football team lost a game. I am responsible for my own safety and my own health.

But, just because I don't choose their way of diving doesn't mean that I will put it down. It works for them and I am sure that I have stolen some ideas on buoyancy control, trim, and equipment set-up from that school of divers. They have many good ideas and training. But you have to buy into the WHOLE system to make their formula work. I don't, but I see where it does for the people that practice their diving and lifestyles this way. As I said before, if you limit your variables, rules of thumb work very well.

I am getting to the point where I would rather read someone's ideas presented in a POSITIVE light then spend my time shooting down ideas that other people have carved in stone.

I also agree that there always is the risk of getting bent. It is somewhat like driving a car. By taking a car out of the driveway, I am risking an accident. But, if I stay within speed limits, stay aware of what is going on, and otherwise practice same driving habits, I reduce the chances of an accident happening in the first place and the severity of it if it does happen. If I stay slightly more conservative than my tables and computer and dive "safely", I could still get bent, although the chances are lower. AND, I CAN pretty much guarantee that when they take a blood sample they will get blood and NOT foam.

 

[boomx5]

Custer once bubbled...

I'm just pointing out that their way of diving, guessing at deco, works fine for the profiles they limit themselves to.

How can you say that they are limiting their profiles? Are you aware of the accomplishments of the WKPP? What about the Brittanic expedition? These guys do this stuff week in and week out and they conduct all their dives in the same manner. So to say they are limiting their profiles admits you don't quite understand the way they shape their dives or do deco.

 

[Custer]

boomx5 once bubbled...


How can you say that they are limiting their profiles? Are you aware of the accomplishments of the WKPP? What about the Brittanic expedition? These guys do this stuff week in and week out and they conduct all their dives in the same manner. So to say they are limiting their profiles admits you don't quite understand the way they shape their dives or do deco.

Reality check.

Do you really think that jj does deco-on-the-fly in a 400 fsw open ocean dive?

Just wings it in his head?

Think that GI3 does it at 300 ft, 3 miles in a cave?

Where does 20/120 fit into any of that?

And no one has once addressed the question of a 6 or 7 dive day.

Their method has specific parameters that dictate dive profiles.

It won't work with the kind of dives that many divers regularly do.

That's limiting their profiles.

"So to say they are limiting their profiles admits you don't quite understand the way they shape their dives or do deco."

Wow. Suggest you re-read the entire thread.

 

[cornfed]

Custer once bubbled...


Where does 20/120 fit into any of that?

And no one has once addressed the question of a 6 or 7 dive day.

I think it already was.

Their method has specific parameters that dictate dive profiles.

It won't work with the kind of dives that many divers regularly do.

That's limiting their profiles.

How? I don't see this.

 

[Custer]

cornfed once bubbled...


I think it already was.

Not that I noticed, but I'll check.

cornfed once bubbled...

How? I don't see this.

Tell me how it works on a "sawtooth" profile, or a 147 ft dive like the Grove.

 

[boomx5]

Custer once bubbled...


Think that GI3 does it at 300 ft, 3 miles in a cave?

"One time I did a dive with Gavin, and at 120 feet after a few stops he asked me for the schedule. I asked him to show me his. He did not have one. I told him I did not have one. He then frisked me and looked through everything in my pockets and my books. He wrote me back and asked if I had a "New York Times" he could read. I told him to get out and get it out of the van and bring it back, or I would get out and read the schedule and come back to tell him what it was. This went through my head, only I remembered taking the deco tables out of my van, and throwing them in the trash a long time ago.

I wondered if I could just get out right there. 360 minutes or SIX HOURS at 285-300 is so ridiculous that I did not want to think about it. I started figuring for a full saturation dive. I knew what that looked like from 250-180, so worked on the rest. I could not come up with any reason to do more deco than for 3 hours, but I did come up with a few very compelling reasons do do LESS between 170 and 100. I tried it. In my mind I broke the dive into three dives: 120 to 40, 240-130, and 300 only. The first dive cleared in my mind 20 minutes into the 40 foot stop. The second nearly cleared after the a 40 minute 40 foot stop, but oxygen did not help it any, and the third cleared to 120 after the 170 stop, producing the second dive as the deco, that in turn producing the third dive as the deco, and all telling me the whole thing could well be done without ANY oxygen. That I was not willing to try, since I had to be back home the next day for sure. I knew absolutely what WOULD work, so did it. I went ahead with an 8.5 hour deco plan, but knew I was not going to get out before 2:00 am , so sent up word to Dawn to get me a room at Wakulla so I could get a couple hours sleep before I left. Panos got the room, and I got up in time to catch Barry Miller coming out of the water from his SECOND 3500 foot plus dive of the day ( he , Chris Werner and Ted Cole went back in and cleaned up the gear which we left at 3500 feet)."

 

[cornfed]

Custer once bubbled...

Not that I noticed, but I'll check.

There was mention about doing a "full decompression" on every dive then running the same schedule for the next dive.

Tell me how it works on a "sawtooth" profile, or a 147 ft dive like the Grove.

First of all, why would you want to do a "sawtooth" profile. Honest question.

Second, the profile for your Grove dive has to be shaped. It's your choice whether you do this with a computer or "in your head."

DISCLAIMER: I am a JAFR. But you already knew that.

 

[MXGratefulDiver]

David Evans once bubbled...


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?

Be careful David ... if Custer decides you're a danger to yourself he's liable to just chuck your computer overboard ... :wacko:

... Bob (Grateful Diver)

 

[MXGratefulDiver]

A couple of you DIR folks have talked about diving a "standard mix" ... from what I gather EAN32. That's well and good I suppose, for doing all these mental calculations. Personally, I like to calculate my mix for a PO2 as close as possible to 1.4 for the planned max depth ... I'm an older dude, and really don't want to push 1.6 if I can help it. Diving the same mix all the time would seem to me to be rather limiting ... diving the wrecks in Nanaimo, for example, I don't want anything over EAN30.

Using your own logic (and terminology), seems like diving a "standard mix" all the time amounts to "turning off your brain" rather than taking the time to calculate your deco limits based on the best mix for the dive profile you're planning to do ...

... Bob (Grateful Diver)

 

[Custer]

NWGratefulDiver once bubbled...


Be careful David ... if Custer decides you're a danger to yourself he's liable to just chuck your computer overboard ... :wacko:

... Bob (Grateful Diver)

Damn, that was cold.