PADI tables finally going away?

[Mr Carcharodon]

The downside of everyone following their computer on a Cozumel dive master lead dive is that the group will likely break up. Not a great deal on a drift dive since the boat then has to pick up multiple divers. It is better to know enough to plan your own multilevel dive so everyone can be on the same page. There was a recent post on another board that discussed two computers giving 60 minutes difference in remaining NDL time. That is no way to keep a group together.

 

[Blackwood]

There was a recent post on another board that discussed two computers giving 60 minutes difference in remaining NDL time. That is no way to keep a group together.

Seems like an awful lot. Can you link to that thread?

Was the consensus that it was an algorithmic difference (e.g. RGBM vs Buhlmann) or a difference in NDL assumptions?

In the shallows, there is no real ballpark for NDL (look up 30 feet in a 10 tables and you'll get 10 answers - or no answer at all - some drastically different). I suspect this is because at 30 feet you're barely at enough ambient pressure to load up to a common critical m-value, but table authors don't feel comfortable writing really long NDLs (5 hours in the case of the US Navy table), so they just arbitrarily cut it down.

 

[tracydr]

Used the tables in nitrox, AOW and now for DM.

 

[tracydr]

The basic digital calculator is a convenience but should never precede or replace fundamental knowledge & comprehension of analog four-operator arithmetic by hand.

The basic personal dive computer (PDC) is a convenience but should not precede or replace fundamental knowledge & comprehension of analog dive tables.

The 120 rule that you can use & generate "on-the-fly" is actually an applied analog heuristic algorithm & mnemonic taken from the old NAUI (and US Navy) NDL Air Dive Table.

Can you tell me what the old 120 rule is?

 

[tracydr]

Most tables will use a square profile, so it assumes that you spent all dive at the deepest point. I find that to be both an advantage and a disadvantage compared to computers as tables will be more conservative on certain dives if you are only at your max depth for a short amount of time. Its handy to get the added time that the computers bring if im going on holiday and going to be diving most of the week however so in that case i generally will use a computer. For my regular diving in the cold dark waters around where i live on the outher hand i find it comforting to have the added safety margin that the dive tables bring.

Im not sure however if i had only been trained on the PADI tables whether i would use them or a computer.[/QUOTE]
They do make a wheel for profiles that aren't square.
I learned in 1994, got my first computer in about 2001. Lot of table dives!

 

[eponym]

Dr. Tracy,

120 is sum of depth and time on the Navy no-deco tables, for instance 60 for 60, 70 for 50, 80 for 40, 90 for 30. The apparent linearity in just this range of depths was a consequence of rounding on the tables.

-Bryan

 

[Mr Carcharodon]

Seems like an awful lot. Can you link to that thread?

That was on TDS. If you look in the decompression form you'll find it. The diver who posted took a photo of the two computer strapped to one arm with two radically different answers on remaining margin to NDL. I think you are right that the difference is how the NDL is calculated at relatively shallow depths. Still once they start spitting out meaningless answers you begin to wonder what the point is.

 

[Blackwood]

That was on TDS. If you look in the decompression form you'll find it. The diver who posted took a photo of the two computer strapped to one arm with two radically different answers on remaining margin to NDL. I think you are right that the difference is how the NDL is calculated at relatively shallow depths. Still once they start spitting out meaningless answers you begin to wonder what the point is.

Yah. Maybe that's why PADI and NAUI don't list anything shallower than 40.

 

[tracydr]

I emboldened the real problem in the above quote and that is a training issue. Why don't they think twice about it? You never taught them to.

More often than not, a traditional instructor's approach to PDCs is simply to ignore them whenever possible. IF the student has a PDC, they will teach them rather than just giving them the knowledge regardless. Odds are, they will be diving with one sooner if not later. You KNOW they are going to get off of tables as soon as they can. Unfortunately, if your concept of a PDC is that it is ONLY a convenience and that there is nothing to them, then you are perpetuating the problem. Learning a PDC is far more than simply learning how to press it's buttons. Heck, the manual can teach you that. As an instructor, our job is to connect the dots so that the students comprehend what they are looking at and what the hell it actually means to their diving. You have to train them to connect what little they have learned about deco theory and use their PDC to their advantage. Obviously, if they ride their NDL on the first dive, odds are they will be having a very short second dive and/or incur a obligatory stop.

I think learning PDCs in general is good, no need for everyone to learn to use a specific one in detail. They can look at the manual (. Order one on line if it got lost) ask the LDS who sold it or carries the model for information.
In life, the important thing to know is where to go to find the information (lds,manual), and what questions you need to ask (how do I put it in planning mode, change gas)
Trying to teach the students all they need to know on one computer only gets them so far. First, they are not always going to have the same model and second, they can't remember everything so what do they do when they forget?
In medicine we could never remember everything but we can become proficient in solving problems and using our references.

 

[Goannaman]

I don't see why PADI (or anyone else for that matter) would stop teaching tables. They seem a pretty easy way to explain NDLs, surface intervals, etc.

I don't ever use my tables, but they are always in my bag, just in case.

I think teaching students the principles of computers are important, but I don't think explaining specifics of the computers are important because they vary to much in operation for this to be practical. Who knows what computers they will buy/ rent. At the end of the day, like any other tool, it is up to the individual to know how the tool works before they use it.