Place of dive tables in modern diving

[TMHeimer]

So, you're saying that any person who is taught the use of tables correctly will never make a mistake in using them in the future, even if they haven't looked at or thought about a dive table in 20 years?

If they haven't looked at them for 20 years (or in my case a LOT less), they'd simply have to get out their OW materials (or internet?) and re-learn how to use them. That's on them to do. I do a table problem daily (alternating between Air & Nitrox), so I'll never forget how to use them. Then again, 1-2 minutes daily isn't much when you're retired....
Ironically, the rare time I dive well below 30', I have to get out my DC manual to make sure I know how it works.

 

[stuartv]

If they haven't looked at them for 20 years (or in my case a LOT less), they'd simply have to get out their OW materials (or internet?) and re-learn how to use them. That's on them to do. I do a table problem daily (alternating between Air & Nitrox), so I'll never forget how to use them. Then again, 1-2 minutes daily isn't much when you're retired....

I haven't perceived that to be a feasible option when I have seen people on a boat talking about planning their next dive using tables. Partly because they probably don't have their OW materials with them and they don't have Internet access on the boat. But, much more importantly, they don't even realize that they are doing it wrong. They THINK they are doing it correctly.

 

[lowviz]

I've seen it done correctly lots and lots of times.

Suggestion: Slow down, cool off, and offer aid where aid is needed.

 

[atdotde]

Looking at my recreational dive profiles almost all are much more a triangle than a square. Those are handled very badly by tables (which give much shorter NDLs if you approximate my the enveloping square). This finishes the argument for me.

Tables are a thing of the past when dive computers were expensive and unreliable. Plus they try to squeeze the information of the state of your body into a single vale (the repetition group) for repetitive diving. Something you don’t have to do on a computer.

The only thing you have to monitor using a computer is that the time to surface stays compatible with you has supply.

 

[KeithG]

I've seen it done correctly lots and lots of times. ...

It is not about the times when they do it correctly. It is about the time when they screw up.

 

[lowviz]

...//...The only thing you have to monitor using a computer is that the time to surface stays compatible with you has supply.

Not so.

Yes, you need to plan for your gas usage. BUT, you also need to follow a reasonable dive profile. You can't just go up and down at will until your gas runs out.

 

[lowviz]

It is not about the times when t hey do it correctly. It is about the time when they screw up.

Oh come on! Then they die.

Screwing up on a rec dive can be a very instructional thing. I've done it, have a busted ear and burst capillary in an eye. Forces one's nose back to the grindstone. Suck it up, move on.

Or for the millennial set, gives them someone to blame. [exaggeration alert]

 

[Storker]

But you can cut your dive into segments as long as you can keep track of the loading from the earlier segments.

This is not really true, which is why the tables can't be validly used for multi-level dives, and is why PADI came out with the Wheel, to allow for multi-level dives. The reason for the lack of validity is that the tables assume you are going to the surface at the end of a "segment" and the N2 loading is thereby reduced over what it was at depth, before the ascent. If you try and construct a multi-level dive from the table, you think there is less loading than there actually is. Not safe.

Using the Recreational Diver Planner for multi-level diving.

Abstract:

Both the PADI Recreational Dive Planner (RDP) and the PADI Wheel are table-based implementations of the DSAT Rogers-Powell model. Since they use the same model, it should be possible to use the RDP to compute multi-level profiles which are consistent with those allowed by the Wheel. This paper presents the derivation and verification of a concise set of rules which maintain all parameters of the underlying model. These very simple rules allow one to use the RDP to compute multi-level profiles which are at least as safe as those permitted by the Wheel.

I don't have more than a few NDL times memorized, and I prefer using my tables for a quick'n'dirty sanity check on my planned bottom time since it's a lot faster to read the RDP than to fiddle with my computer's buttons. After reading that paper, I started using the method the author describes for planning multilevel dives. And while I follow my computer when I'm underwater, there really isn't much difference between what my rough plan tells me, and what my computer tells me. If anything, using the PADI RDP that way is more conservative than my computer is. Even if I use a computer brand which many folks here claim is overtly conservative. Maybe it's because the segment depths I use in my plan are max segment depths, while my dive seldom has a step-profile.

 

[Storker]

If you don't have a clue, Your in deep s##t if your computer dies...

Not any deeper than if you're diving tables and your bottom timer dies. Either way, you should call the dive and ascend.

 

[Saniflush]

I would contend that there is a direct correlation between dive tables being taught and computer sales. In my limited experience, the more the dive tables are taught, the more computers my LDS sells to those who had to learn them.