New divers and computers

[terrasmak]

I dive my computer , but still carry my tables and refure to them a lot , especially when diving with newer divers and ones without a computer.

 

[vkalia]

But given our limited diving opportunities, when we travel, I don’t want to miss a moment of safe diving by only using tables. So what do I do?

Use a computer, but don't follow it blindly. The computer should remain a tool in your arsenal, and not become a crutch.

A computer is a great way for tracking your SAC, for example. Match your average depth to your air usage - that'll help you figure out how much air you consume and how that changes with external factors. And read up on decompression theory - figure out what goes on in your body, realize that decompression is not a binary state, etc.

Enjoy your diving - it is meant to be fun. Watch your buoyancy, watch your air and stay with a buddy, and you'll be jes' fine.

Vandit

 

[Amberjack]

No after the O2 question

One makes all the difference, eh?

 

[PaulChristenson]

One makes all the difference, eh?

Geez... You better believe it

Maybe we can to do a St Lawrence shot later this year together??

I'll see if I can drum up some interest in our Department for it...

Later

Paul in VT

 

[bradshsi]

I’ve also read the threads where many of you have argued very convincingly that new divers shouldn’t start with computers because they should be completely familiar with the tables first.

But given our limited diving opportunities, when we travel, I don’t want to miss a moment of safe diving by only using tables. So what do I do?

In the end it's a call only you can make given the type of diving you do and your tolerance for risk.

As others have pointed out shore diving profiles are not a particularly good fit with square table profiles. Computers have lots of spiffy features such as profile logging and NDL credit for multilevel profiles.

On the other hand you have little or no control over how conservative, accurate or bug free the computer is. Typically the computer will be less conservative than tables. Plus it's electronics in a hostile environment so eventually it will fail.

Regardless of whether tables or computers are used, the more you push them the higher the accepted risk. I liked this quote from a far more experienced diver (I've truncated it some for brevity).

Okay folks, this is the drill, as they say in the military! First of all, Snow Bear is spot on the money when she says that those who push the limits of their tables are bound to get in trouble. Almost all of the tables have some conservatism built in these days, but in some cases, not a lot. Push at the limits and sooner or later you will bust out of the edge of the envelope!

...it is extremely important to remember that EVEN IF you are well within the table limits, there can be instances in which you become a statistical outlier. NO table or algorithm...I say again...NO table or algorithm ever reaches a zero probability of DCS occurrence. This is why we talk of "un-EXPECTED" cases of DCS, not "un-deserved" cases. I do not mean to scare you. Just to point out that there is always some risk, albeit a low level of it!

Personally (for what it's worth), I dive with tables because I'm a somewhat conservative soul and I don't view computers as having a good cost/benefit tradeoff.

Good luck with your choice.

 

[Iruka]

I see what you're saying, but to be fair to the instructor, he absolutely used it as a 'teaching opportunity.' And he did impress on us the need to take everything into account - ie, surface intervals, max. depth, bottom time - to plan our dives and calculate our NDLs.

In doing many recreational dives, they tend to be "multi-level" and not always comfortably fit onto a "square" dive table profile. As others have said, students are supposed to fit their dive onto either the wheel or regular dive table. The wheel, obviously (for those who have ever used it) will give you a lot more time (by allowing multi-level profiles) than will the other table. (I'm just referring to the 2 PADI products here, not being familiar with other types of tables.) Anyhow, one thing that I've occassional done is to plan the dive to "fit" whatever table is being used, but then use the "safety stop" to make the dive a lot longer. Some sites, for instance, have a shallow reef.....so we might do the last 20 minutes or so just cruising along the top of the reef. Since this is all safety stop depth or shallower (around 5m/15') it doesn't count as bottom time. The recommendation for a safety stop is at least 3 minutes, but there's no rule against going LONGER. I've seen instructors now & then who seem to want to get back on the boat as soon as possible....so a "deep" training dive to 30m/100' means they're back on the boat in 20 minutes or so (as they've hit the table NDL within that time.) Air permitting, I like to be "first in the water, last on the boat" (which captains aren't always happy with ) and by explaining & utilizing the principles of multi-level diving, an NDL time for a certain depth doesn't necessarily limit the time you can spend underwater.

 

[Amberjack]

Maybe we can to do a St Lawrence shot later this year together??

I'll see if I can drum up some interest in our Department for it...

That'd be great!

 

[RadRob]

Forget the tables. Who needs them? Just buy two computers. If you are down and the first one goes out on you, you can use the second one. (j/k of course)

Learn the tables, buy the computer. If your computer goes belly-up, you can always ascend immediately, with safety stops along the way. Personally, while I know the tables, I haven't used them in many years. Like all that history and trigonometry you learned in school. Good to learn, but when in "real life" are you going to use complex equations (unless you are a scientist or mathematician)?

 

[Diveral]

I’ve also read the threads where many of you have argued very convincingly that new divers shouldn’t start with computers because they should be completely familiar with the tables first.

If you know that then you know why we suggest not relying on your computer. Some divers wear and suggest using two dive computers, one as the primary and the other as the back-up. I've always wondered what you do if your computers disagree. I use a computer and my dive watch, depth gage, and the tables are back-up. That way when the computer craps out when I am at 90Ft for 15 minutes I have a alternate plan and the day's diving is not shot. If you don't know your tables a or how to plan repetetive dives with tables then you're screwed.

You can get the computer and then run your tables like you normally would. That way you learn the tables and find out how much more bottom time you are getting using a multilevel dive capable computer.

My 2 cents

 

[Charlie99]

I use a computer and my dive watch, depth gage, and the tables are back-up. That way when the computer craps out when I am at 90Ft for 15 minutes I have a alternate plan and the day's diving is not shot. If you don't know your tables a or how to plan repetetive dives with tables then you're screwed.

If you follow the tables as a square profile dive, you may be screwed even if you do have tables and watch with you.

The other day my 1st dive was an no-required-deco dive of 131', 1:06. If my computer dies during the SI, what do your tables say?

A less extreme example is this morning's dive. 79', 45 minutes before getting back above 50', 54 minutes total runtime. What do the tables say about that one? What would the tables say about a failure partway into my second dive -- 46' max, 1:28, after an SI of 1:38.

I don't bother carrying a depth gauge and tables with me because it generally isn't realistic to switch over to tables during the dive. Depending upon the situation, I'll just gracefully abort the dive by going shallower than 30' and hanging around for a while. Or I might (gasp!) look at another diver's computer and take into account the differences I've already observed about his profile and mine.

I just accept that a computer failure will cause me to fall back onto the tables for future dives. For just a second dive, I'll simply assume pressure group Z on the PADI table and go from there. For a day with 3 or more dives, I'll have to make a judgement call as to whether I need a 3 hour min SI or not.

I've always wondered what you do if your computers disagree.

Common sense you dictate that you follow the more conservative one.

Hopefully, you understand your computers well enough that you can judge whether or not the discrepancy is due to differences in the algorithms, or due to a failure in one of them.