DIR recreational deco?

[R_Deluca]

There's no magic here but I can't speak for DIR or GUE. Start a thread outside the DIR forum and I'll discuss it more but for starters don't get confused by some of the stuff GI has written.

I don't have any links but I've seen several "minimum deco" charts published.

The 120 rule is just a way to know NDL's without having a table in your pocket so you can use that or if you happen to have the NDL's from your favorite tables memorized you could use those also.

Plan the dive based on a profile depth which could be anything from your max depth (like you were taught) to an average depth or anything inbetween that you are comfortable with.

Do some minimum decompression for every dive along with nice slow ascents.

For a second dive do it the same or maybe add 10 ft or so to your profile depth if it makes you feel better depending on the nature of the dives and the SI.

Play with some decompression software and tables and you'll see that these things combined will work just fine.

When in doubt check yourself against some tables or software.

The mysterious ratio deco is just about as tricky as this. LOL

Again I'm not speaking for DIR or GUE but this is pretty much what I do.

I see the course outline is coming together already!

 

[Evans]

For a second dive do it the same or maybe add 10 ft or so to your profile depth if it makes you feel better depending on the nature of the dives and the SI.

What you wrote is pretty much what I do and close to what they talked about in my DIRF, as I recall. All except for what I quoted above. Do you mean that you do a shallower dive, but treat it like it was a little deeper, or do you mean that the idea is that doing an actually deeper dive is safer? I ask of course because since that's the opposite of what PADI et al teach I'd be interested to know the rationale.

I'm thinking the reason must have something to do with compressing bubbles enough to shunt through the lungs -- which is what I remember reading as a problem with quick bounce dives after a deep dive.

By the way, for all concerned, I'm talking about "rec" profiles, which is what I thought the OP was talking about. Shouldn't have to take a a tech course to learn how to do that safely. Not that it should matter anyway,.

 

[MikeFerrara]

I see the course outline is coming together already!

Absolutely and it works just dandy too. LOL

 

[MikeFerrara]

What you wrote is pretty much what I do and close to what they talked about in my DIRF, as I recall. All except for what I quoted above. Do you mean that you do a shallower dive, but treat it like it was a little deeper, or do you mean that the idea is that doing an actually deeper dive is safer? I ask of course because since that's the opposite of what PADI et al teach I'd be interested to know the rationale.

Sorry. I meant that to account for residual N2, sans a rep letter group you could just plan the next dive as though it were a little deeper than it is. Run some dives on a table and see how it comes out. You can easily come up with rules of thumb that work for the dives you're doing.

By the way, for all concerned, I'm talking about "rec" profiles, which is what I thought the OP was talking about. Shouldn't have to take a a tech course to learn how to do that safely. Not that it should matter anyway.

Well that's why I said that I'd prefer this wasn't in the DIR forum. I'm not a GUE instructor and I won't in any way promis that this is exactly what they do or teach but I didn't invent it or come up with it in a vacuum either. LOL

It's also not my intention to be teaching anything. Just giving you some things to think about beyond blindly following a table or computer without noticing any trends.

I'd guess and say that some of the reason they don't teach this stuff in DIRF, beyond the 120 thing that I think they go over sometimes, is that you can't come up with a profile depth other than max depth without the awareness and control to know what your profile actually was.

 

[JamesP]

I'd guess and say that some of the reason they don't teach this stuff in DIRF, beyond the 120 thing that I think they go over sometimes, is that you can't come up with a profile depth other than max depth without the awareness and control to know what your profile actually was.

Mike
The other thing you have to consider is the skill level of the divers. What they teach is of little benefit when a large number of divers cannot deco out without having a mooring line to hold onto. You have to start them off with the basic skills of bouyancy, trim and valve management before you introduce decompression obligations and more elaborate gas management.

You mentioned in you first post that there is no magic here. I have to say that holding a ten foot stop is the magic. You cannot just give people the numbers, pat them on the back and tell them to have a nice day. Thats just wrong.

 

[JamesP]

What I was saying in my original post was this:

Nobody on earth knows what the best deco theory is.


Just because GUE have the highest standards of training for SCUBA dosen't mean they know more about deco theory than anyone else.

Everyone has a theory on deco and no one theory is any more valid than anyone elses.

Precisely dude,
If you ever get to taking any GUE training one of the first things the instructor(s) will tell you is that they have not reinvented the wheel. They just make it run a little smoother.

It has been my experience to have the instructors break everything down to the fundamentals and rebuild and fine tune the skills and knowledge set from there. I found this to be most rewarding

 

[MikeFerrara]

Mike
The other thing you have to consider is the skill level of the divers. What they teach is of little benefit when a large number of divers cannot deco out without having a mooring line to hold onto. You have to start them off with the basic skills of bouyancy, trim and valve management before you introduce decocompression obligations and more elaborate gas management.

You mentioned in you first post that there is no magic here. I have to say that holding a ten foot stop is the magic. You cannot just give people the numbers, pat them on the back and tell them to have a nice day. Thats just wrong.

Agreed James.

Just for clearity let me point out that I wasn't trying to suggest diving beyond no-stop limits without training. Several agencies are now teaching deeper stops as part of a "safety stop" NAUI has the "rule of halves" and GUE and IANTD are using stops at 30, 20 and 10. In general some time spent shallow after time spent deep and slow ascents.

Also I purposely didn't give any numbers but rather general ideas and concepts some one could give some thought to while playing with their tables, computer (I know eeek!) or decompression software.

IMO, like buoyancy control and trim, a little decompression theory beyond "follow the light on the computer" is something divers should be introduced to before even going to open water.

 

[Charlie99]

Why even have a board if the answer is always, "take a class"?

I took a DIRF, and if I had a nickle for every time someone asked a legitimate question on one of these boards and the answer was "take DIRF" and it was something they never even mentioned in my class, I'd, well, I'd have a couple of bucks, anyway.

Anyway, what's wrong with the question? Is GI advocating deepest dive last for recreational profiles, and if so, why? It's not like it's a tech diving question, as if that matters.

Perhaps those items were covered in your classbooks and handouts even though the instructor never mentioned it.

Surely there is some hardcopy info you take away from the class to help refresh your memory later.

 

[MikeFerrara]

Why even have a board if the answer is always, "take a class"?

I took a DIRF, and if I had a nickle for every time someone asked a legitimate question on one of these boards and the answer was "take DIRF" and it was something they never even mentioned in my class, I'd, well, I'd have a couple of bucks, anyway.

Anyway, what's wrong with the question? Is GI advocating deepest dive last for recreational profiles, and if so, why? It's not like it's a tech diving question, as if that matters.

You might want to take a look at "Technical Diving in Depth" for an overview of bubble mechanics and a pretty thorough treatment of reverse profiles. I won't try to explain it but I think what you want to look at is the effect on an existing bubble seed by a parameter called P(crush). If I remember right both the magnitude of the descent and the rate of descent have an effect but that's not the only factor and it's as far as I'm going to go without the book in front of me.

I've read the article that you're refering to and I can't explain it. You could probably shoot GI or JJ an email and ask for an explaination of what was behind his recommendations.

 

[lamont]

IMO, like buoyancy control and trim, a little decompression theory beyond "follow the light on the computer" is something divers should be introduced to before even going to open water.

I think this is what I'm trying to ask. I'm looking for what we can take from emergent theories about decompression coming from dual-phase models or the WKPP and what can be applied to NDL diving within rec limits. One of the examples of that is the shift to stops at 30, 20, 10. Can we re-examine how we do surface intervals and penalties for reverse profiles based on this emergent information? Can we teach multi-level decompression diving to NDL divers so they don't have to buy computers?

And unfortunately when I see "take tech I", particularly when it seems like I'm getting talked down to, I kind of assume that the poster can't explain anything because they need a refresher themselves (this is aimed at *some* of the people who suggested tech I, not all).

Also, its annoying that people assume that you're going to be irresponsible with any information that you acquire on the Internet. I've been on the net since 1989 and know better than to blindly trust what I read here, what I read on the WKPP site, what comes from the industry or even what I'm taught in GUE classes. I'm probably not going to be putting my computer into guage mode for at least another year or two.

And then there's the people who assume that you don't know crap about decompression because you haven't taken Tech I. Actually I've got my tables memorized for the depths where they're important (implied there is also that I know what depths they're important for). I've graphed and studied the NDL curves for NAUI, RDP, GUE, USN and my Suunto Vyper and compared them with similar graphs based on air consumption. I've implemented various Buhlman-Haldane models and played around with those and gas loading in different compartments for different profiles. Now that I think I'm feeling more comfortable with the terminology of dual-phase models the next step for me is trying to implement RGBM, but the math there is the only math I've come across in diving that isn't completely trivial and I haven't found the time. I've also read that one mechanism of doing multi-level dives is to just compute based on average depth, and I've been considering experimenting with that using a computer implementation of a Haldane model, and figuring out where I could make that break and under what circumstances that could be trusted. And if it sounds like I place too much weight in the deco models, I have a few years of quantum mechanics under my belt, and I understand better than most that the model isn't necessarily reality. What else do I need to know to pass the entrance exam? (oh yeah, PFOs, bounce diving, yadda yadda... know it...)

Well that degenerated into a bit of a rant -- I guess I did have a bad week at work....

Feel free to respond, don't expect me to respond though -- I think I've gotten it out of my system...