Which tables should you believe?

[IndigoBlue]

So are you saying all PSD, Military and Commercial divers are fools?

Gary D.

Commercial divers normally wear hard hats.

Military divers normally wear rebreathers.

Where the heck are you getting your info from??

 

[glbirch]

buy a dive computer,they are the most accurate.

Really? Which computer then, given that different computers are based on different algorithms?

 

[Gary D.]

Commercial divers normally wear hard hats.

Military divers normally wear rebreathers.

Where the heck are you getting your info from??

Let’s take a look at each one.

“Military Divers normally wear rebreathers”. When was the last salvage, recovery or repair operation done with rebreathers? The combat divers use them quite a bit but they are a small part of the military. Besides isn’t a rebreather SCUBA? Most units in use today are semi-closed and not fully closed circuits.

“Commercial divers normally wear hard hats”. Depends where they are and what they are doing. SCUBA is still widely used. There is a lot of commercial diving that can’t be done, or is not cost effective to do in a hard hat.

“Where the heck are you getting your info from”?? Having been both of the above and still a very active PSD I’m passing on first hand information.

So, from a sport divers stand point, are they fools or not? You made the statement and I was just trying to understand your line of thinking in regards to it.

Gary D.

 

[MikeFerrara]

I gotta go with Uncle Pug and BCS.

All that "accuracy" and "precision" in a computer using a model that doesn't predict what's going on in your body and has no idea how far you have to hump your gear or how you felt after you last similar dive...doesn't mean a thing.

Kim,
One pressure group more or less might be important when you're taking a written test but that's all.

More important is good dive habits like slow ascents with "deeper" stops realizing that all dive are decompression dives. the only choice is how you decompress.

 

[Rick Murchison]

I gotta go with Uncle Pug and BCS.

All that "accuracy" and "precision" in a computer using a model that doesn't predict what's going on in your body and has no idea how far you have to hump your gear or how you felt after you last similar dive...doesn't mean a thing.

I wouldn't go that far... I'd be lying if I said I don't massage the tables based on lots of things - like those Mike mentions - but to say the model is meaningless is a bit further than I'm willing to go. I always have tables as a baseline from which to make decompression decisions (including so-called "no decompression" dives, which most of mine are) for my little pea brain needs a "jumping off" point.
Rick

 

[wedivebc]

Really? Which computer then, given that different computers are based on different algorithms?

Most dive computers still use some version of the Buhlmann algorithm however they may be "j-factored" to make them more conservative.
Some computers have started using the RGBM model such as Suunto and HS Expolorer. This model allows you to start your deco deeper but results (theoretically) in less overall deco time. Many people find they feel better after the dive from doing deeper stops.
No algorithm is more correct than another since it is just a mathmatical simulation of what happens in the average human tissue. Your body will be somewhat different.
I defer to what UP said:

If you stop and think about all the differences not only in tables but in computer generated profiles, especially those that allow user input of conservation to be used... precision in output begins to look like a fools game.

Thinkaboutit.
?

 

[H2Andy]

tables and computers are tools, and they are more than adequate for 90% of
all divers.

that said, if there was a way available to me to learn the DIR curve thing (which i
barely understand), i'd give it a try. however, it seems like i would have to take
at least a DIR-F and a TECH-1 (i am guessing) to get there, not to mention spousing
the entire DIR approach, which I simply am not ready to do.

thus, it's tables and computers for me.

 

[glbirch]

Most dive computers still use some version of the Buhlmann algorithm however they may be "j-factored" to make them more conservative.
Some computers have started using the RGBM model such as Suunto and HS Expolorer. This model allows you to start your deco deeper but results (theoretically) in less overall deco time. Many people find they feel better after the dive from doing deeper stops.
No algorithm is more correct than another since it is just a mathmatical simulation of what happens in the average human tissue. Your body will be somewhat different.
I defer to what UP said:

This pretty much sums up the reason I asked the question, as I don't think stating that 'dive computers are accurate' is really... accurate. As has been said, they are all working on theoretical models and YMMV.

Human nature being what it is, people seem to believe the tables/computers that match with their own level of diving aggression/conservatism. More than once I've heard a variation on "My computer is too conservative, I'm buying one that gives me more bottom time."

 

[AtomicWalrus]

Remember that all dive tables are just models of how a generic human body behaves under pressure, and can't account for everything. For example, your dive table may not account for the fact that you're that 1 person out of every 4 with a patent formale ovale (the "hole in the heart") that predisposes you to DCS, or if you're dehydrated, or maybe you've got a really lean body that allows you to off-gas more efficiently. Given that the model isn't that precise, you shouldn't get too hung up on the precision of the predicted NDLs either, unless they appear to be wildly optimistic.

All of those tables are based on a theory with a limited amount of testing that drew a line where there appeared to be an acceptably low incidence of DCS. The DCIEM tables are more conservative because they're based on more testing, and being Canadian, the test conditions were probably more rigorous than tables evaluated in warm water. The PADI RDP also has quite a bit of testing built into it, but it's a little less conservative because it's intended more for recreational diving than working diving.

 

[gj62]

The DCIEM tables are more conservative because they're based on more testing, and being Canadian, the test conditions were probably more rigorous than tables evaluated in warm water.

Are you sure that the testing wasn't done in a chamber? I'd be surprised if they did the tests in open water - too many variables...