Crowley's Blog

[Crowley]

We're in the tail end of High Season, and the not every diver is as good as they think they are - especially when it comes to working their own computers...

http://www.scubaboard.com/forums/blogs/crowley/173-crowleys-blog-dive-computers-not-toys.html

Cheers

C.

 

[Vassilis Vlachopoulos]

Would this experience of yours suggest / insinuate that tables (RDP) should be maintained in OW training and not be superseded by "computers" ?

 

[Crowley]

Hmmm - macrobubble commented as such on the blog page...

Personally I have always thought that use of the tables provides a basic introduction to decompression theory that has a more visual aspect than simply plugging numbers into a computer. I compare it to the difference between an analogue watch and a digital one - both tell you what time it is, but the analogue watch gives you a visual representation of the passage of time. I can "see" that a quarter-hour has passed by the relative position of the hands, and I don't even have to actually know what time it is. A digital watch requires you to make a small additional calculation.

In the same way, the pattern of the lines and boxes on the RDP tables provide a broad visual reference for a diver's memory. Even if they forget how to work the table correctly, there's a very obvious "deeper means shorter" pattern to the table, whereas computers just tell you exactly where you are at any given time.

My feelings on the teaching of tables have changed somewhat over the last two years, where my work has been mostly as a dive guide rather than an instructor, and I very rarely teach OW these days. I'm now the guy that has to deal with the aftermath of other people's instruction and since tables are effectively obsolete in my job, I'm starting to think it's better that computers are taught in more detail as part of basic training. Bear in mind that all of the problem folk I mentioned in my post are not new to diving - some were certified before I was and therefore inevitably would have been taught with tables - also I feel I should mention that they were not all certified by the same agency.

My dilemma is therefore do I want people to learn tables which have almost zero practical application these days, or correct use of computers which actually cause us rather a lot of headaches? I really don't want to see theory being removed from basic training, but if it means that there is more focus on the practical aspects of diver training - buoyancy, breath control, safety, computer use - then so be it. That's become a lot more valuable to me over the last few years.

On the other hand, if this particular guy had his tables on board - or I had mine, for that matter - maybe we could have worked out a second dive for him based on his maximum depth and time for the first. After all, this was the original PADI advice for using a computer - if it fails and you have a backup as in watch, depth gauge and table, you can re-plot accordingly.

I think it boils down to the fact that - at least in my world - nobody uses tables any more. Those who don't have computers rely on the guides to make very conservative dives, and some of those that do have computers create unnecessary complications by not understanding them. If this guy had been taught "if you forget to set your nitrox percentage, dive the air profile", which is correct, or understood the display - and all computers are only variations on similar themes - then possibly we wouldn't get this type of problem. If he'd also Read The Falootin' Manual this would have been of additional benefit!

I can see a day in the not too distant future where agencies market their courses with computers as part of the crew-pack "complete with PADI Zoop Computer..."

"..And the times they are a-chaaaaanging..." - Bob Dylan

Cheers

C.

 

[Solly]

I don't know about the OW current curriculum but for the PADI EANx course, they dropped the tables and instead told the student that the instructor will teach him how to setup his (the student) computer when diving in nitrox mode...

 

[macrobubble]

Whereas the tables used to be an absolutely necessary tool to execute dives safely in the past, they are today (IMHO) a tool to understand what computers do and what the numbers on the display mean. The introduction to tables gives a deeper understanding of decompression theory and avoid computers to just be a "black box" an your wrist. At school, you learn to calculate easy equations in your head, or more complex ones with pen and paper, before they allow pocket calculators.
I feel already today that too much theory has been sacrificed on the altar of "easy diving". Ask the average beginner who Boyle-Mariotte, Gay-Lussac, Dalton and Henry are and what their relevance to diving is - you will probably get a blank stare. All of that used to be part of beginner training 20 years ago (and with CMAS still is!). Diving is fun, absolutely, but diving also has certain risks which to understand and avoid needs a basic knowledge of diving-physics and diving-physiology. Too much knowledge does not hurt - too little can lead to accidents!

Learing the tables, even if you don´t use them later, is essential to become a safe diver!
Of course, I could strap a computer on a beginners wrist and ask him or her to not let the little number on the display get close to zero, but that would be like training a dog to sniff cocaine. There would be no understanding of "why". And there would be no understanding of the risks, if you exceed the limits and ignore them! And there would be no understanding of what a computer really does.
In the EAN-course, skipping the tables is OK with me, because, as I said, they are not taught to later really use them, but to understand the principles that a computer operates on. As long as the tables are taught in the OWD-course, that objective is met. But eliminating them alltogether is a really, really bad idea!

 

[Vassilis Vlachopoulos]

Those who don't have computers rely on the guides to make very conservative dives, and some of those that do have computers create unnecessary complications by not understanding them.

I have one additional concern. Divers who were not taught and/or are not familiar with tables, are very likely to ignore actual NDL figures (i.e. 45 min at 20 m, 20 min at 30m etc).

Unless a diver is using the planning / simulation mode of his computer (if available), the only perception of NDL is a "number" (among others) on his computer that starts from some undefined value and, within some time period, it will gradually decrease towards zero (and then rise again). Ok, this does provide some understanding of what goes on with NDL, especially if the diver pays attention to the variation of this "number" in conjunction with time and depth.
It is, however, retrospective. If the diver does not know BEFOREHAND the NDL of the dive he is about to undertake, IMHO he cannot do an optimum planning of his dive.

This is probably not an issue for the usual multilevel dives close to a reef. It does, however, become an issue for square profile dives, say to visit a wreck at 30m (could be the Thistlegorm). By knowing beforehand that such a dive has an NDL of 20 min, the diver(s) can plan to spend x time to the stern, y time to the holds and z time to the bow (assuming there is no DM to plan the dive on their behalf and guide them).

Now, tell me Crowley, from your experience, how many divers among the hundreds you have accompanied to the Thistlegorm, you would trust to let them dive w/o DC and feel safe that they would know how to monitor their NDL? I anticipate that we need to add to our briefings not only to watch out for 100bar but also for NDL in order to set our turnaround / end_dive point.

 

[Crowley]

I agree Vassilis, and Thistlegorm is a great example - the number of divers I would trust to dive there independently is a small minority anyway in terms of the overall number of people that visit the wreck, and a few years back my dive centre adopted the policy that is mandatory to use a computer to dive there, and one must be hired if the diver doesn't have their own.

I reckon that the majority of divers I guide there do indeed have their own computer, and given their age and experience range, must have learned to dive using tables. Also, the majority of people who have problems with their computer / unplanned deco / etc. fit into this category. The (often more inexperienced) diver who rents them tend not to have so many problems, because - at least in my case - I spend some time making sure that they know how to read the display. Sadly, this is often a case of "when that number gets to 10, let me know - otherwise you might DIE!"

The number of people who actually have these computer issues is very small compared the the high volume of divers that pass through my centre. Don't forget that this is only based on my own personal experience, which may include a high turnover of customers but does have a fairly limited scope - great diving in a fun and safe environment with experienced dive professionals - but there's no "challenge" to the diving, other than to enjoy it, not break anything, and time your toilet breaks carefully.

In general I don't want to lose the table completely, but I would like to see some time spent on dive computers also, and how the two relate. PADI standards make the decision "either/or" when it comes to teaching tables versus computers. I think that in my particular corner of the diving world (which is not a small corner, after all), the best decision is "both".

Cheers

C.

I have one additional concern. Divers who were not taught and/or are not familiar with tables, are very likely to ignore actual NDL figures (i.e. 45 min at 20 m, 20 min at 30m etc).

Unless a diver is using the planning / simulation mode of his computer (if available), the only perception of NDL is a "number" (among others) on his computer that starts from some undefined value and, within some time period, it will gradually decrease towards zero (and then rise again). Ok, this does provide some understanding of what goes on with NDL, especially if the diver pays attention to the variation of this "number" in conjunction with time and depth.
It is, however, retrospective. If the diver does not know BEFOREHAND the NDL of the dive he is about to undertake, IMHO he cannot do an optimum planning of his dive.

This is probably not an issue for the usual multilevel dives close to a reef. It does, however, become an issue for square profile dives, say to visit a wreck at 30m (could be the Thistlegorm). By knowing beforehand that such a dive has an NDL of 20 min, the diver(s) can plan to spend x time to the stern, y time to the holds and z time to the bow (assuming there is no DM to plan the dive on their behalf and guide them).

Now, tell me Crowley, from your experience, how many divers among the hundreds you have accompanied to the Thistlegorm, you would trust to let them dive w/o DC and feel safe that they would know how to monitor their NDL? I anticipate that we need to add to our briefings not only to watch out for 100bar but also for NDL in order to set our turnaround / end_dive point.

 

[Karibelle]

I'm enjoying the blog, Crowley. Keep it up!

I am going to jump into this one...

Learing the tables, even if you don´t use them later, is essential to become a safe diver!

I - like many of you, it seems - have struggled a bit with the move away from teaching table use, toward computers in OW. One shop that I teach for in Canada made the commitment early this year to do all computers in OW. I'd submit that learning the tables themselves isn't the essential bit, it's learning the concepts behind the tables. The tables are simply a tool (that seems to be on its way out in OW classes) for understanding the relationships between depth and time, and the potential effects those relationships have on our bodies. The computer is nothing more than the next tool. If we choose to teach only the tool, well, that's not our best choice... but there is simply no reason why a student who's been trained in computer use rather than table use must leave his OW course with less than a full understanding of the theories behind the tools.

And on the subject of the fellow in the blog - do you really think having a table would have helped him?

 

[Crowley]

Thank you Karibelle - always glad to know that people are reading this stuff!

And you bring up a fair point, which is that in some cases, the level of training and what was actually taught is kinda immaterial - some people simply never learn. Anything.

Cheers

C.

 

[Crowley]

Stilll going strong: ScubaBoard - Crowley - Blogs

Also don't forget the latest edition of the Equalizer is out (click on my signature for the link) and UK viewers keep an eye on upcoming editions of DiVE Magazine

Cheers,

C.