Are dive computers making bad divers?

[Storker]

Just as a matter of interest - for those experienced with tables, how would you work out your no stop times more accurately for a typical shore dive similar to the one I posted a couple of pages back (copied below for info)?

I like the KISS approach. If the plan is too complex, I won't remember it. Particularly if I'm diving deep-ish (for me) and get a little tipsy. So I never plan more than two levels. Deep level first, shallow second. Planned depths are maximum planned depths, with a contingency in case we see something really cool just below us. A typical plan will be "max XX meters for XX minutes, then max YY meters for YY minutes. Safety stop, surface." (EDIT: Min pressures at the two depths are also included.) During the dive I monitor my computer and my SPG for real-time corrections to the plan. Max run time is never exceeded, because if we stay longer than that, we risk that the dive leader calls emergency services. And that could be rather embarrassing...

On my table, I'd model your shore dive as 18m from A to C, then - depending on the depth profile - some guesstimated value between 18m and 5m from C to D. Probably some 10 to 14m depending on the ascent speed/steepness of the slope. Safety stop depth isn't included in the NDL plan, but in the total plan to find the run time I give to the boat tender/dive leader before we splash.

---------- Post added November 26th, 2015 at 02:35 PM ----------

And you thought that metric was some how superior.

99 times out of a hundred, it is That was the exception to the rule

 

[Neilwood]

I like the KISS approach. If the plan is too complex, I won't remember it. Particularly if I'm diving deep-ish (for me) and get a little tipsy. So I never plan more than two levels. Deep level first, shallow second. Planned depths are maximum planned depths, with a contingency in case we see something really cool just below us. A typical plan will be "max XX meters for XX minutes, then max YY meters for YY minutes. Safety stop, surface." (EDIT: Min pressures at the two depths are also included.) During the dive I monitor my computer and my SPG for real-time corrections to the plan. Max run time is never exceeded, because if we stay longer than that, we risk that the dive leader calls emergency services. And that could be rather embarrassing...

On my table, I'd model your shore dive as 18m from A to C, then - depending on the depth profile - some guesstimated value between 18m and 5m from C to D. Probably some 10 to 14m depending on the ascent speed/steepness of the slope. Safety stop depth isn't included in the NDL plan, but in the total plan to find the run time I give to the boat tender/dive leader before we splash.

---------- Post added November 26th, 2015 at 02:35 PM ----------


99 times out of a hundred, it is That was the exception to the rule

Cheers for that - I did cover tables in my OW course but shore dives such as those weren't covered in any way. I would be diving with a computer anyway but was wondering in case the computer borked after/during a dive how to determine the appropriate SI and residual ntrogen time. Would you consider the final D-A lag as surface time or only run the clock from actual surface time?

 

[Storker]

I would be diving with a computer anyway but was wondering in case the computer borked after/during a dive how to determine the appropriate SI and residual ntrogen time.

That's real simple. Take a two hour SI, and unless you were in PADI W or higher after your first dive, you'll be in PADI B. If the dive was really long, reckon that you're in C. From there on it's a walk in the park

Would you consider the final D-A lag as surface time or only run the clock from actual surface time?

It wouldn't contribute to my SI time. I'd be fine with not having it contribute to underwater nitrogen time either, but it's up to you to determine how much conservatism you want.

 

[The Chairman]

99 times out of a hundred, it is That was the exception to the rule

It's just a tool. I use the ones I'm familiar with. Of course, everyone knows that metrics rot your brain. Just multiply your depth by 3 (or 3.3 if you're CDO) and the planning rule still works. Easy.

Remember, the rule of 120/140 should never replace using a PDC or even tables, if you're a Luddite.

 

[tridacna]

Hmm...let me think. 99.999% of rec divers worldwide use PDCs. The remaining 11 are ranting on this board. Paradigm is almost over. The remaining adherents will take this to the grave with them.

 

[Eric Sedletzky]

I think I might have come up with a fairly good analogy between tables and computers. I always seem to refer to automobiles for analogies, but anyway...
So in the old days we had tables, and now we have computers.
In the old days there was no power steering, no power brakes, no A/T, no air bags, no anti lock brakes, etc. You had to manually drive the car, shift the I'm stupid, muscle the wheel around with two hands, push down hard on the brake pedal and hope it didn't lock up and skid out of control.
Now we have everything automatic and easy to use, power steering, power brakes, auto trans, anti lock brakes, air bags, and a multitude of other conveniences.
Now it's possible for a driver to yak on their cell phone with one hand, hold a cup of coffee with the other, and drive with their knees.
In the old days you couldn't do that. So in this sense, the ease of use through technology has enabled the feeble minded to abuse technology.

However, what both can still do is: run red lights, hit other cars, speed, drive drunk, and cause general havoc on the roadways.
Just like a table diver could not plan their gas supply, go too deep, split on their buddy, have bad skills ....yada yada.

Computerization and technology isn't going to make better drivers or better divers, there are idiots everywhere. I put some of the blame on instructors for enabling idiots when they shouldn't be anywhere near the water, just like some people shouldn't be on the road.
Computerization in itself doesn't create anything, it's just a machine, a tool. What it's done though is made regular idiots into bigger idiots, but it doesn't make idiots from scratch.

 

[scubadada]

I'm an old timer, certified in 1970, Navy tables, by the LACUU. Personally, I think it's a good thing if new divers learn tables. Teaches the rudiments of diving physiology, nitrogen absorption and elimination, residual nitrogen time, NDLS, deco. The basics are very helpful in fully understanding and using a dive computer. I'm afraid shortcuts may miss some of this basic information just like current nitrox training might miss some of the basic, important information. I have no problem with modern technology, I've been diving computers since 1999.

 

[doctormike]

The issue really isn't whether or not computers make it easier to calculate NDLs than tables... I know that there are some table-slingers here who say that they can plan a dive faster than someone with a computer. OK, maybe, but who cares? It's not like it takes hours to plan a recreational dive with a PDC, there is plenty of time between the dive briefing and the splash to generate your NDL ahead of time, so that you can plan.

But the thing about that NDL that you generated ahead of time with your computer or your tables is that it is INACCURATE. It almost certainly will not reflect your actual profile, unless you really are diving a site that is completely flat. The computer on your wrist knows your ACTUAL dive profile, in real time, during the dive. And it's always better to make diving decisions with correct information than a guesstimate made ahead of time. If your plan includes watching your depth and times during the dive at all the different levels, and then working out an updated NDL on the fly with waterproof tables - well, then you are a better diver than I am!

This was an issue when I first started tech diving. I would cut tables on my wrist slate, and then just do that deco no matter what I had done on the dive (always being careful not to exceed the N2 loading calculated ahead of time by overestimating the square bottom depth, and having +5 foot / +5 minute contingency tables as well). And I would frequently be hanging on the line long after the Petrel told me that I have cleared deco.

But one of my regular buddies convinced me that I was diving with inaccurate information, and that I was better off doing the deco that my dive actually required, and use the slate as a backup in case of computer failure. So that's what i do now.

 

[phoenix31tt]

Personally, I think it's a good thing if new divers learn tables. Teaches the rudiments of diving physiology, nitrogen absorption and elimination, residual nitrogen time, NDLS, deco.

Teaching someone to use tables does not teach them the bolded section. If you want them to learn the bolded section you teach that... teaching someone to use tables teaches them how to calculate the estimated NDL for a dive. All other values on the table are used to calculate that, and that's about it. The pressure groups, the RNT, the SI... it all goes into simply calculating how long you can safely stay at a particular depth.

 

[timz]

I'm an old timer, certified in 1970, Navy tables, by the LACUU. Personally, I think it's a good thing if new divers learn tables. Teaches the rudiments of diving physiology, nitrogen absorption and elimination, residual nitrogen time, NDLS, deco. The basics are very helpful in fully understanding and using a dive computer. I'm afraid shortcuts may miss some of this basic information just like current nitrox training might miss some of the basic, important information. I have no problem with modern technology, I've been diving computers since 1999.

In my country, the authority requires a driving school to teach and test in manual car. But it's up to the diver to buy am automatic or manual transmission car.

I appreciate if diving is the same. Learning the table and and up to the divet to stick on a table and timer or to get himself a dive com.