OW class question

[Diver0001]

I think we should let the OP decide that.

As I said, he wanted to know if it was "nuts" to want to learn tables, not just rely on a computer. Providing a relevant situation where it is beneficial to know tables is NOT "off topic".

Ok, as you wish, we can see if the op wants this discussed here or not. (to the OP. if you don't like this side-bar please use the "REPORT" button and ask a moderator to split the thread).

Please don't get me wrong, I don't think there is anything wrong with wanting to learn about the tables and I have nothing against tables. When I learned how to dive there were no computers and I made my first 650-odd dives using tables.

Moreover, as I said above, I still teach both precisely because we *are* in a transition period. I believe where we differ in opinion is that I foresee that transition coming to a slow end at some point and you do not. I believe at some point people *will* see tables as an historical curiosity, the same way we see the abacus as an historical curiosity as compared to the calculator. Are we there yet? Maybe not, but I believe we will be.

Things change in this world. Some people accept change better than others and I think in our day and age this is especially true of acceptance of new technologies. Human beings have had similar debates about just about every change in history, not just in diving. Maybe the first caveman to use a hand full of pebbles to count higher than the number of fingers on his hand had a similar "debate" with his contemporaries. Likewise, people have literally been put to death for believing the world was round. But were they wrong?

Holding on to the past is no guarantee that the past ways are "better" (for lack of a better word). Do the reasons people used tables in the past still sufficiently justify spending the time on it in an age where we have technology that is (in some ways) demonstrably "better"? I think you would say yes. I'm not so convinced, especially when I see a potential risk (and clear examples) of mistakes if the diver is not using tables regularly. Where the rubber meets the road, people seldom use tables anymore and we've only had (decent) computers for a short time. How long do you think that it should be before we question the utility of teaching tables until the end of days just because we did so in the past? Our mathematics is no longer limited to counting fingers. We no longer accept that if you get cancer that you will die. Many children born in the last decade have never seen a telephone that plugs into the wall or has a rotary dial. We rely on technology and we accept new technologies as they come if it makes our lives easier or better. In my mind, it's no different in this case.

Whether people accept or resist change seems to have less to do with the new developments as it does with people themselves. There is a wealth of information available about "traditions" and "traditional thinking" and the idea of changeless worlds and organic societies. These are philosophical discussions, and it can be quite fascinating. In them you can get a sense of the very mechanics that come into play in these kinds of debates and the computer/tables discussion as an example of that.

The reason people end up exchanging stand-points about these things is because it's really hard to bridge the gap between letting go of traditions while not debasing the value they had at the time, and not wanting to let go at all. To be honest, I don't have a good approach for that. I understand you, but I don't agree with you and I'm not willing to hold on to past ways of doing things as much as you are. For your part, I think you must feel the same about what I'm saying. It's a hard gap to bridge.

R..

 

[Eric Sedletzky]

I don't think the transition from tables to computers is a big a deal as some make it out to be. With tables you look at your bottom timer or your watch and your depth gauge, and with your computer you look at your depth and time remaining. The only difference is with one you have the info stored in your head and with the other the computer has the info stored and you just follow it. But you still have to look at something.
Tables aren't rocket science and are pretty straight forward.
The cheapest computer I can find now is about $159.95 on sale. Most people will spend probably between $250 to $500 on a computer. This is substantial if it's a "requirement" now.
When I got certified they taught us tables and threw one in for free and we went diving.
If you wanted a computer then it was a luxury, but not mandatory.

 

[T.C.]

If I were on my "ultimate dive trip" I'd make sure I have a backup computer. If one poops the bed I have the other with me in the water to cover my ass. I usually have one with me even on quarry dives, just in case.

As do I now. But many diver have to save their pennies for that one special trip, and it is cheaper to rent one computer than buy one or two.

I believe at some point people *will* see tables as an historical curiosity, the same way we see the abacus as an historical curiosity as compared to the calculator. Are we there yet? Maybe not, but I believe we will be.

Yet, there is still a place for a manual backup in this world. The Shuttle carried calculators, and manual calculators, in case something happens. It's a backup. My tank has emergency modes for the turret and even a full manual backup with crank handles, manual hydralic pumps, alternate sight (with rangefinder), and manual firing device. It's a backup.

It doesn't replace the primary; but it is available if needed. We don't stop training it just because something better came along. Astronauts don't stop training backups just because there is a better system installed.

Things change in this world. Some people accept change better than others and I think in our day and age this is especially true of acceptance of new technologies.

Congratulations. You completely FAILED to grasp my point.

NOWHERE did I say that things should not change or that we should "hold on to the past" or that tables are better. I support teaching computers; it should be the primary means- but the alternate should be taught as well. There are many reasons to continue; Eric provides another good example; what if a diver can't afford one? Let's face it- one reason you teach computers is to sell and rent more; the PADI mentality.

This is a simple, inexpensive BACKUP method. It ensures that, in the event of the failure of your primary, you can still dive. Ever here of a PACE plan? Due to the inherent dangers of diving, all risks should be mitigated with this as one of the control measures.

I'm not so convinced, especially when I see a potential risk (and clear examples) of mistakes if the diver is not using tables regularly.

Then this is where you failed as an instructor, to instruct properly. If they were taught properly, then it is their fault for letting a skill deteriorate.

How long do you think that it should be before we question the utility of teaching tables until the end of days just because we did so in the past?

You simply don't grasp the concept of backup, do you? There always exists a viable need to have an alternate plan if one system fails. If your computer fails on a trip, having a backup can save time and money.

Teaching tables does not infringe on the ability or need to teach computers. Nor should it replace computers. Both should be taught side-by-side. This produces a more skilled diver, one that can better handle an failure. And as such, the OP is to be congratulated for recognizing where the agencies have lowered the standard, and wanting additional training to correct this.

 

[TMHeimer]

I don't think it's nuts at all to want to learn tables. What if somebody doesn't have the money right away for a computer or only plans to do easy fairly shallow shore dives for the first few years?
You don't need a computer to do these dives, but it would be easy with tables to at least know in your head what kind of time you allowed at what depth.
Tables are crude but still the most reliable technology out there because they're a physical chart that you can hold and look at and memorize in your head. You don't have to make sure you changed the batteries in your table.
The only thing is tables are designed to use for square profiles, whereas computers will constantly adjust remaining bottom time according to the changing depth.
Some people don't think this is always a good thing since computers have the capability take you all the way to the edge. However, computers do have different settings to adjust away from agressive profiles.
Tables have a built in safety factor because of the square profile, but some people have even taken tables a notch up by learning to "depth average" instead of using the deepest depth for setting the time.

I still like the idea of an analog system to fall back on in case all else fails. Nobody can take the tables out of my head.

A lot of good advice -- I like this as one of the best. My tidbits are--it can't hurt to see everything spelled out on the tables--gives you a better understanding of what the computer is doing. As for learning the tables now, if you haven't gotten that from your Instructor I agree they're not hard (even for me). Probably can be found somewhere on the internet as well. Computers require studying each different one's instructions. I know the basic important stuff with mine--don't know stuff like how to transfer data to your PC and then possibly to be printed out--don't really care (paper logbook). So you have to understand what the computer is doing and how your specific model works.

 

[Dive-aholic]

Tables are becoming a thing of the past. And while there are people that state if your computer fails you can fall back on tables, do you have a depth gauge or bottom timer to use in place of the dead computer? I always have a dive watch with me but I personally don't have anything other than my dive computers to tell me what depth I'm at, well, except my knowledge of the dive site.

I also don't agree with the response to listen to your computer. Too many divers are "flying" their computers these days. They go in the water and simply wait until their computer tells them they are getting close to NDL. There's very little dive planning occurring. Dive computers do have dive plan functions. You should be using that to plan your dives. If you're dive is going to be at an average depth of 60' then go to the plan function and look up your NDL. Then plan you dive according to that. Don't simply jump in the water and wait for your computer to tell you you're 3 minutes from going into deco so you better start ascending. That's how accidental decompression happens. Even divers intentionally doing decompression dives are letting their computers dictate their stops rather than planning their dives before hand. This is simply unsafe and unacceptable.

 

[T.C.]

Tables are becoming a thing of the past. And while there are people that state if your computer fails you can fall back on tables, do you have a depth gauge or bottom timer to use in place of the dead computer? I always have a dive watch with me but I personally don't have anything other than my dive computers to tell me what depth I'm at, well, except my knowledge of the dive site.

Yes, but this is due to your extremely high level of training. Few people have your experience. You know what you need. I dive two computers, but I still have a depth gauge as manual backup.

Would you recommend a new diver dive without a depth gauge? As well trained as you are, you know the risks of diving with a single point of failure in one computer.

 

[Ricky B]

You figure out the time you were in the water and the depth from the previous dive. If you don’t know this from YOUR watch, you can compare the time from a diver who dove before you (the start time of their dive), and the end time from a diver who exited after you (thus giving you a longer dive for computing, then look at your depth gauge and get your max depth. Figure out your SI (using a diver who exited after you if needed) and you now have your dive time, max depth, and SI.

You can run the tables, and figure out the pressure group you finished your last dive at, and use the SI to figure out the NDL for your next dive. Set it in your watch and you can make the next dive safely.

I am not wading into the should-they-teach-tables debate, but I do want to point out a relevant fact, often ignored in these debates.

Because the computer does not require a square profile for its calculations, the dives actually done will often make the tables go haywire. For example, I was on vacation and did two dives per day. One morning, the first dive was to 91' and the total dive time was 44 minutes. OK, let me look at my PADI table. A max depth of 91' means I have to round up to 100'. I go down the 100' column and I see that the max bottom time is 20 minutes. What pressure group does 44 minutes that put me in? There is no applicable pressure group (Gee, I must have the bends).

So whether I have the tables as backup or not, I am sitting out the rest of the day.

I don't think I did a single dive that would not have put me off the charts, so to speak, with the tables.

For those who have the money to devote to this problem, the solution is a back-up computer.

In fact, a savvy instructor can use the comparison of the two, and the extra time a computer gives you to encourage sales.

Point of clarification.

Since the tables require a square profile, comparing apples to apples, some (e.g., Suunto) computers will give less time with a square profile than the tables tables. For example, for the first dive of the series, the computer gives 50-minute time limit for a 60' dive and the PADI tables give 55 minutes. The NOAA tables give 60 minutes. I haven't checked the USN tables but the NOAA tables are based on the USN tables (and the manual for the Suunto says "The no-decompression limits displayed by the dive computer for the first dive to a single depth are slightly more conservative than those permitted by the U.S. Navy tables.")

Multilevel profile, computer wins hands down. Square profile, the tables win.

---------- Post added March 15th, 2014 at 11:11 PM ----------

Too many divers are "flying" their computers these days. They go in the water and simply wait until their computer tells them they are getting close to NDL. There's very little dive planning occurring. Dive computers do have dive plan functions. You should be using that to plan your dives. If you're dive is going to be at an average depth of 60' then go to the plan function and look up your NDL. Then plan you dive according to that. Don't simply jump in the water and wait for your computer to tell you you're 3 minutes from going into deco so you better start ascending. That's how accidental decompression happens. Even divers intentionally doing decompression dives are letting their computers dictate their stops rather than planning their dives before hand. This is simply unsafe and unacceptable.

This is why computers must be taught. It takes a while to learn how to use a computer properly.

As for teaching tables too, I'm not jumping into that debate for now.

 

[Dive-aholic]

Yes, but this is due to your extremely high level of training. Few people have your experience. You know what you need. I dive two computers, but I still have a depth gauge as manual backup.

Would you recommend a new diver dive without a depth gauge? As well trained as you are, you know the risks of diving with a single point of failure in one computer.

For recreational dives I see no problem with not having redundancy. If the dive computer fails during the dive then the proper response is to ascend to the surface. A 3 minute safety stop at 15-20' would be nice but not necessary if you don't know when you're at 15-20'.

 

[Agility]

Tables can show you at a glance that NDL gets shorter the deeper you go. IMHO they are a good tool to teach the principles of decompression, there is nothing wrong in asking about them in a course that only covers computers. You can download tables if they are not provided with your course material e.g. Chikarma Diving - Diving Holidays Malta - Scuba Diving In Malta & Gozo: PADI Dive Tables PDF Download - Chikarma Diving they are easy to use and the basic principle is printed on them.
If you want to read more about what is going on in your body when diving you might have a look at Deco for Divers: Decompression Theory and Physiology: Mark Powell: 9781905492077: Amazon.com: Books

 

[DukeAMO]

I almost always calculate my dive profiles after each dive using the tables, for practice, and just in case my computer fails. I have a waterproof watch and a depth gauge as backup. If my computer failed mid-dive (unlikely), or if I accidentally left the computer at home (happened once), I could still dive based on the tables and a square profile. In other words, I would act as if I had been diving on tables all day.