Computers & Tables

[Gamehunter]

HI Beezwax
I thank you for your response but the statment that you made about the tables and the computers being from the same mold are not true. I took my calculations from my Uwatec computer that if dived in a square profile the most liberal reading would be 48 min while the most conservative time would be 8 Min. Now correct me if I'n wrong but how are these times even close to the table for 60' at 55 min?

 

[beezwax]

Gamehunter, I said broadly speaking they are the same. I also said it was a simplified answer. They are based on the same mathematical model, the work of John Haldane a hundred years ago. There have also been refinements to his original work (i.e. Spencer limits, Buhlmann limits) and you sometimes hear the term "neo-Haldane" models. These variations account for the fact that different computers/tables are going to give you different numbers. If you are really interested do a google search for "decompression theory" and you'll find plenty of interesting stuff to read!

 

[blueskies92629]

I dunno, I clearly remember the first time I was sitting on the bottom of a swimming pool in Laguna Beach California. There I was, breathing underwater!! That was in 1976. Since then I have quite a few thousand hours of SCUBA. I also worked as a hat diver in the Gulf of Mexico and have a few thousand more hours of bottom time working my butt off. When I glide into the water it is still a big thrill. I love it almost as much as I love skydiving.

The point I'm making is that the reason I SCUBA dive is to have FUN! I use the Navy tables, a pencil and a piece of paper. I never exceed the no deco limits. Always keep track of my RNT and always, always, always put safety first.

I've never had a problem with somone getting a couple more dives than me in a day or a week for that matter. I figure it's an ego thing and that usually leads to being uneasy from the inside out. The Buddah had it right

Drive Fast, Take Chances, Life is Short, Play Hard.

 

[beezwax]

Keep in mind that this is all a theory, a mathematical model. It has certainly been proven to be workable in the field by a hundred years of diving, but there is no real-world connection between the model and the human body. It is based on hypothetical tissue compartments. That is why it is possible (but not common) to take a hit even if you don't break the No-D limits. That is also why all computers and tables have to add the caveat that there is no guarantee that you'll be fine even if you don't break the rules, and why they all tell you to be conservative. But as Larry pointed out, it is ultimately a personal choice of course. One thing he did mention is a lot of cases of DCS are probably caused by too rapid an ascent, rather than necessarily overstaying the limits. Ascent rates are another thing that RGBM specifically addresses.

 

[beezwax]

blueskies, welcome to SB!

 

[Zeeman]

Just remember, if you are sick of your Oceanic wearing diving buddy getting more bottom time, you can always set your Suunto into EAN mode (say.. 26%?) to get a similar no deco time...



Z...

 

[padiscubapro]

There are other factors to address as well.. "no deco" tables allow different limits for surfacing values as opposed to models tha can deal with decompression obligations.. take the traditional 100fs for 20 minutes by the rdp, most buhlman based models limit this to 16 or 17 minutes.. if you stayed the complete 20 minutes you would not just be entering deco, you would have already incurred several minutes of deco..

tables are simplified models, they dont take into account multiple controlling compartments, they set the limits based on a specific compartment, when you are doing deco you generally have to clear multiple "compartments" and even as a faster one is clearing you may now be still loading a slower compartment..

Also depending on the goals of the tables they use a single compartment to calculate surface intervals.. some commom choices are the 60 minute compartment for no deco table and 120 min compartment for decompression tables. (dive co,puters generall tarck all the compartments the computer supports)

 

[beezwax]

Just remember, if you are sick of your Oceanic wearing diving buddy getting more bottom time, you can always set your Suunto into EAN mode (say.. 26%?) to get a similar no deco time...



Z...

Haha, hey Z,

As eluded to earlier, my answer is often to let my computer go into deco mode. It doesn't bother me to do "extra" stop time since it's usually only a few minutes more, and I think it's a smarter profile. I hadn't thought of dialing up the O2...I might just peg it at 40% and spend all day down there!

 

[Gamehunter]

I guess thats one way to get more nitrox dives in.

Welcome Blueskis.

 

[Zeeman]

Haha, hey Z,

As eluded to earlier, my answer is often to let my computer go into deco mode. It doesn't bother me to do "extra" stop time since it's usually only a few minutes more, and I think it's a smarter profile. I hadn't thought of dialing up the O2...I might just peg it at 40% and spend all day down there!

Heh, I'm glad you saw the humour in that

Z...