Nitrox Class Without Tables or Math...OK?

[friscuba]

In response to the 2 posts above... The point I'm trying to make to both Soggy and Mike is that you can easily do dives which break the tables and still stay safe, and you even seem to agree with it... yet both of you seem to be critical of any course which teaches you how to be safe without relying on dive tables and formulas.

Mike, when you say I'm losing that bet, are you saying that you never dive a dive that doesn't fall within basic flat profile dive tables? I highly doubt it. If YOU don't need tables or a computer to dive a dive with a 70 foot max for an hour or so, why are you so critical of someone who teaches a nitrox course that teaches students how to be safe without knowing formulas?

I guess I don't get it.

 

[The Chairman]

Class was a blast! Cleared up quite a few misunderstandings with the students. Can't wait for CoolTech's assessment of it! Three different types of computers and they all were able to determine MOD easily.

 

[rottielover]

Well I realize this thread is already huge, but I thought that perhaps a fresh perspective might be nice...

Some of you may remember my stupid questions, as my wife an I have been certified a grand total of ALMOST whole year now

Unfortunately, we've only been able to complete a total of 14 dives so far (we plan on correcting that this summer, so expect to see me at Mermet Springs a lot).

Anyway, my wife and I completed our bookwork for the PADI class, and we're off tomorrow (actually it's today already! I really need to get more sleep), anyway, tonight in fact we're off to the dive shop for our classroom... I understand that the 2 dive requirement is now gone, and that we'll be certified upon successful completion of the class tonight.

So, here is my opinion (2 bubble's worth) and I hope that by posting this, that those of you who are professionals might gain additional insight into your students in same small way.

I for one, really preferred to learn on the tables first, and then go to my dive computer with an understanding of what's going on in the electronic brain. While I agree with others that the math portion of the book seems "rushed" (that is, it seems like there is far more information in the front of the book than in the back), I was glad to learn the formula's to be able to get the calculator out and find my numbers.

But don't get me wrong, I love my dive computers, they are super cool tools, just like that computer your using now could be a super cool tool , but like any electronic device, are subject to failure, especially in such a hostile environment like submersion in water!

I dive with two computers, my Gecko, and my Mosquito, but I also prefer to "run the tables" after every dive while logging. In fact, thus far I have been using my table results for my dive logs, and my computers more as timing/depth gages. Since in OW we learned to run the tables, I feel a good level of comfort coming back from a dive where BOTH my computers AND my tables tell me that I was well withing the limits.

Even though I dive with 2 computers, I know that in the unlikely event that both fail, that I will still be able to calculate my numbers using my tables.

So if you haven't been able to tell thus far, yes I trust my computer to a degree, but I trust the tables more. As my wife and I go on through more dives, and then on too our AOW, I plan to continue to add tools in order to help me dive "safer and funner"


So from one student to another, my personal recommendation is to learn the tables, learn the math, and then you understand what that fancy calculator on your wrist/console is really doing (dive computer).

From a student to instructors, I would have to say my gut feeling would have to be, cover how to use the tables properly... I understand that none of you want to become math instructors, lord knows that our public schoolz ain't all that great, but then again, if your student is unable to do the math, I fail to see how they could be a safe diver if for whatever reason they end up using a tank of 22 - 29 % ...

Wow, I rambled on Way too much, sorry...

Anyway, my hope is that those in the "know" will read my thoughts and gain some insight from a student about to go to class....

 

[El Orans]

Can't wait for CoolTech's assessment of it!

[thread=144235]SDI Easy Nitrox Class - Report[/thread]

 

[BHB ScubaTroll]

Here is the report... this is my last post to this thread

http://www.scubaboard.com/showthread.php?p=1891635&posted=1#post1891635

Do you sit by the refresh button, El?

 

[El Orans]

Do you sit by the refresh button, El?

 

[DivesWithTurtles]

...
I for one, really preferred to learn on the tables first, and then go to my dive computer with an understanding of what's going on in the electronic brain. ...
...
So from one student to another, my personal recommendation is to learn the tables, learn the math, and then you understand what that fancy calculator on your wrist/console is really doing (dive computer).

Why does anyone think that knowing how to read a table provides an understanding of "what's going on"?
How do the numbers on the tables better represent the formulae and algorithms used to calculate decompression than the display of a dive computer or the output of a deco program?
Would learning the Wheel give you an even better understanding of "what's going on"?
How does learning table reading make you understand physics or physiology?
What math did you study to understand "what that fancy calculator on your wrist/console is really doing"?

 

[MikeFerrara]

In response to the 2 posts above... The point I'm trying to make to both Soggy and Mike is that you can easily do dives which break the tables and still stay safe, and you even seem to agree with it... yet both of you seem to be critical of any course which teaches you how to be safe without relying on dive tables and formulas.

I'm not sure that I understand the question. I'm not sure what you mean by "breaking the tables". I do conduct dives that require staged decompression but I don't think that's what we're talking about.

Mike, when you say I'm losing that bet, are you saying that you never dive a dive that doesn't fall within basic flat profile dive tables? I highly doubt it. If YOU don't need tables or a computer to dive a dive with a 70 foot max for an hour or so, why are you so critical of someone who teaches a nitrox course that teaches students how to be safe without knowing formulas?

I guess I don't get it.

I'm saying that I can do multilevel dives without a computer or table calculations. I'm not going to go into detail but I'll try to give every one a few things to think about. I'm not suggesting that any one else do anything different than what they were taught but...I would describe my calculations (for lack of a better term) as being based on tables but a bit more conservative than many popular tables or what many computers would have you do. I just don't need to actually look at a table for recreational no-stop dives even when they're multilevel and/or multiple dives.

A couple of things to keep in mind here is that there are a number of things that are probably more important than a precise calculation using exact depth, exact time and a decompression model thats really a SWAG. Meaning that the NDL is anything but a nice thin line with safety on one side and a sure trip to the chamber on the other. Those other things relate to your own condition but more in our control is our dive habits especially ascents.

I'm not saying that any one should ignore the model of their choice or run around violating NDL's but I am saying that the precision that divers sometimes feel they are getting with a computer doesn't really exist. The computer is accurately calculating something that only loosly relates to what's going on in your body. It's like cutting a board with an axe and measuring it with a micrometer. Look at a bunch of tables and note that NDL's could vary by as much as about 40%. That's a huge variation. Will the real NDL please step forward? Play with some decompression software and notice that by changing user selectable parameters that the output profile can be drastically effected. Also notice that some of the dives your computer or table might let you do as a no-stop dive will come up requireing staged decompression. Which one will work? All? None? What precission?

Just try something. Look at a dive table closely. See if you can see any patterns. Just for fun run some dives on paper, estimate and see if you can't get within a couple of minutes of what the table says even over 2, 3 or 4 dives using some simple rules that fit the patterns on the table. Now compare your "estimates" with several different tables and maybe some sample outputs from some software. Were you in there? Now if you did those dives and use good habits in your diving and didn't try to redline it, does that theoretical couple of minutes one way or the other matter a whole lot? Personally I don't think so.

Again, I stress that I'm not suggesting that any one should do anything except what they were taught but if you look at some of the things I've pointed out and give it some thought you might look at your diving in a little differently. The point isn't whether or not you carry a computer, it's whether or not your thinking and diving is keeping up with it (proactive or reactive) and realizing that getting anywhere near a "limit" puts all bets off. If the diving is sloppy (the norm?) you may be playing with fire even if you did spend $1000 on a fancy computer and it only made it into a yellow (which is a safer color than red from what I've been told).

If you followed me on a multilevel dive carrying your computer, you're computer would be more than pleased with our profile. I just don't need the computer to do it. Further, any dive I do that's even close to what might be considered an NDL is planned as a staged decompression dive meaning that recreational divers are diving profiles every day that I wouldn't touch with a 10 ft pole...and once in a while they get bent doing it. It also means that while your computer would probably be happy with my profile, your computer or table may very well suggest profiles that I would not be happy with...so I'm glad that the thing went on your credit card bill instead of mine.

 

[The Chairman]

I'm saying that I can do multilevel dives without a computer or table calculations. I'm not going to go into detail but I'll try to give every one a few things to think about. I'm not suggesting that any one else do anything different than what they were taught but...

And you teach this to your students??? I am not sure I would want the liability! As I said: you got me beat! No tables and no narcosis! I am impressed! Is the next thing to go your regulator???

 

[Rick Murchison]

Why does anyone think that knowing how to read a table provides an understanding of "what's going on"?
How do the numbers on the tables better represent the formulae and algorithms used to calculate decompression than the display of a dive computer or the output of a deco program?
Would learning the Wheel give you an even better understanding of "what's going on"?
How does learning table reading make you understand physics or physiology?
What math did you study to understand "what that fancy calculator on your wrist/console is really doing"?

What is needed is a feel for "what's reasonable?" You can know how to use the tables cold, but unless you incorporate what the tables are telling you into your personal TLAR diving envelope you can still make an egregious error. Computers, being computers, can make *really* egregious errors from time to time, and unless you have a feel for what's reasonable you can go merrily on your way and do something really stupid based on what the computer tells you, or, even worse, miss a dive 'cause the computer says you can't go when in fact you can.
If you're one who really believes a computer "always" makes the same calculation the same way every time and you don't believe computers screw up in a big way from time to time then you're living in a fantasy world. It is not a matter of whether the computer will give you bad information sometime, just a matter of when... and whether you have enough of a grounding in what information is reasonable to recognize it.
My personal solution is to (1) run my own approximation of what the computer ought to be telling me before I ever look at it, and (2) carry either a backup computer or at the least a bottom timer and depth gauge in addition to the computer. I have yet to use or to see a computer brand that hasn't given bogus info from time to time.
Rick