Teaching Computers in OW class vs tables

[MikeFerrara]

But do current teaching methods via the tables make students understand deco theory?

IMO, no. I don't think getting rid of teaching tables is a step in the right direction though.

You have pointed out one issue which is that its more difficult to plan a serieis of dives using a computer. Mine only scrolls current allowable NDLs, but cant tell me when to quit in order to have a certain amount of time on another dive.

Tables can help there but better yet some decompression software is the nost useful and instructive.

 

[Web Monkey]

When I got out of the water I looked at it to try and figure out what made it flip. Apparantly I bumped it or something and put it in some super duper ultra conservative mode. Of course there isn't any way to fix it or even figure that out under water so if I didn't already know exactly how I was going to do the dive I would have been at the mercy of that crazy machine.

You can't really blame the computer for that. You set it for "ultra-conservative", that's what it gave you.

And then there's all the computers that lock up or go into gauge mode for 24 or 48 hours if you violate one of its rules. No computer should EVER do that. It needs to keep calculating and let you make the decisions.

You need to violate a whopping great rule to make it do that.

The Smart-Com will lock out if you blow through all the manditory stops (not just the optional stops you get if you set it to "conservative").

It's a reasonable response, since the condition of your body would then be outside the parameters that the algorithm in the the computer can handle. Your body is in a condition where the computer can't safe dive conditions, so it locks out.

Can you imagine the lawyer feeding-frenzy that would happen if a diver blew past all his stops, got to the surface, felt OK, then went on another dive "because the computer said it was OK", then got bent?

You don't have to like computers, but the fact is, they do a lot better job of monitoring a diver's condition, alerting to potential problems, (and collecting data in case of an accident) than a huge portion of the divers would do themselves.

In any event, it's just a computer, and doesn't have a shock-collar attached, so if it locks out because of something that happened, but you still want to dive, nothing prevents you from grabbing an SPG, depth-guage and watch and going in again.

Terry

 

[kalvyn]

How about this, an informal poll. In how many dives has your computer failed how many times? Ive used mine 100 times and had 0 power failures or misinformation. Note: Im not interested in user error here, that is a different topic.

Second, lets take a hypothetical. A dive computer will never fail. If this was the case, what would be the problems with tossing the tables and teaching OW students computers only?

1. My Mosquito failed on me mid-dive after about 100 dives. It was less than a year old and replaced for free under warranty. I continued and finished the dive, only getting uncomforatble when it was reporting 40 fsw when I knew we were in 20 fsw or less. I should have just taken then thing off and put it in my pocket, as no information is better than misinformation in my personal opinion.
2. Again, my own personal opinion -- I personally don't believe the tables are taught correctly and just switching to "trust your computer" mode will not improve the education model. What really matters is the "shape of the curve" and that time shallow makes up for time spent deep. Also, just flatly stating that "computers increase your bottom time" (which is not true; education and understanding increase your bottom time) without talking about the shape of the curve or that time shallow makes up for time spent deep will do more harm than good.

Let me throw out a recent example dive, which my wife and I did using bottom timer/depth guages only:

• Dive time -- 72 minutes
• max depth -- 58 fsw
• avg. depth -- 35 fsw

Now, if you base the dive on NAUI tables (how I learned), I blew my NDL on the first dive by 17 minutes. Fortunately, I know that I did a multi-level dive with a lot of time spent shallow. Using my average depth of 35 fsw, a 72 minute dive is nowhere near the NDL according to the NAUI table (40 fsw for 130 minutes).

After a one hour four minute SI I'm a letter G, so I know that my next dive should be at a max depth of 70 fsw or less (which it was, by the way).

Interestingly, on this particular trip I dove with the D3 (gauge only) on my wrist and my Mosquito in my bellows pocket (I wanted to see how it thought I did). I did not look at the Mosquito until the end of each diving day, and it was never violated. My wife and I dove the profiles we wanted, using our brains and tables only, and lived to tell the tale. We never pushed NDLs the entire trip, and our average dive times were 60 minutes or more.

Jimmie

 

[ShakaZulu]

Let me throw out a recent example dive, which my wife and I did using bottom timer/depth guages only:

• Dive time -- 72 minutes
• max depth -- 58 fsw
• avg. depth -- 35 fsw

Now, if you base the dive on NAUI tables (how I learned), I blew my NDL on the first dive by 17 minutes. Fortunately, I know that I did a multi-level dive with a lot of time spent shallow. Using my average depth of 35 fsw, a 72 minute dive is nowhere near the NDL according to the NAUI table (40 fsw for 130 minutes).

After a one hour four minute SI I'm a letter G, so I know that my next dive should be at a max depth of 70 fsw or less (which it was, by the way).

Interestingly, on this particular trip I dove with the D3 (gauge only) on my wrist and my Mosquito in my bellows pocket (I wanted to see how it thought I did). I did not look at the Mosquito until the end of each diving day, and it was never violated. My wife and I dove the profiles we wanted, using our brains and tables only, and lived to tell the tale. We never pushed NDLs the entire trip, and our average dive times were 60 minutes or more.

Jimmie

Please give me your dive plan (tables) for this dive. You mention that the Naui tables would have put you over the tables NDL, and then you say you did the dive using tables for you ML profile??? Did you use your average depth to determine your NDL??? Scary.

 

[kalvyn]

Ok, I have question for all the table dewds.......... I always log my dives to the logbook after a dive.

Diving Air

Dive 1

Dive Time - 28min
Max Depth - 99ft
Ave Depth - 62ft
Safety Stop - 3min (stayed within the NDL limits as shown by the computer)

Dive 2 (SI 1:09)

Dive Time - 25min
Depth - 85ft (last time I looked, the computer stopped working)

Immediately accended with my buddy and did a 3min safety stop. When can I do my next 85ft dive again?

Well, without knowing the actual total dive time of the second dive (how much time between the time your computer dies at 25 minutes and you actually got out of the water), here's what I would do:

After the first dive, by the NAUI tables I would be letter group F. After an 1:09 SI, I would be letter group E. Average depth on the second dive... let's say 60 fsw to be conservative. AMDT for group E @ 60 fsw is 25 minutes. After the second dive I would be letter I, which means that I would have to be out of the water a minimum of two hours three minutes to be able to dive to 85 fsw again (for not very long!). I would not go below 66 fsw for the third dive for any lenght of time, personally.

Jimmie

 

[kalvyn]

Please give me your dive plan (tables) for this dive. You mention that the Naui tables would have put you over the tables NDL, and then you say you did the dive using tables for you ML profile??? Did you use your average depth to determine your NDL??? Scary.

Our dive plan was 60 fsw for 55 minutes. We were at 60 fsw for nowhere near 55 minutes. We spent at least 15 minutes (most likely more, I can't view the profile graphic at work) in 20 fsw or less, just using up our air (well, my air... my wife kicks my butt in air consumption). FYI, your computer uses your average depth to determine your NDL (for all practical purposes).

Jimmie

 

[Web Monkey]

[/list]Now, if you base the dive on NAUI tables (how I learned), I blew my NDL on the first dive by 17 minutes. Fortunately, I know that I did a multi-level dive with a lot of time spent shallow. Using my average depth of 35 fsw, a 72 minute dive is nowhere near the NDL according to the NAUI table (40 fsw for 130 minutes)

The tables aren't linear, so you can't average the depth.

The NDL for 60 feet is 50 minutes (at least on the table I have handy). The NDL for 120 feet isn't 25 minutes, it's 10.

Terry

 

[Web Monkey]

Our dive plan was 60 fsw for 55 minutes. We were at 60 fsw for nowhere near 55 minutes. We spent at least 15 minutes (most likely more, I can't view the profile graphic at work) in 20 fsw or less, just using up our air (well, my air... my wife kicks my butt in air consumption). FYI, your computer uses your average depth to determine your NDL (for all practical purposes).
Jimmie

The computers I've seen continously calculate the remaining bottom time based on actual depths and times, not an average.

Terry

 

[kalvyn]

The computers I've seen continously calculate the remaining bottom time based on actual depths and times, not an average.

Terry

Which is why I said for all practical purposes. Interestingly enough, from what I've seen if you run some profiles in a deco planner program, the NDLs work out to be pretty close to the average depth of the dive, though (for recreational no stop diving).

I personally use the 120 rule (time + depth = 120) and not the NAUI tables specifically. I used them in my example as that's what I'm most familiar with when it comes to tables. I am quite comforatable doing a dive with a resulting average depth of 50 fsw for 70 minutes. Others may not be, and they shouldn't dive that way. Don't dive like I do, one may die as a result.

Jimmie

 

[ShakaZulu]

I am quite comforatable doing a dive with a resulting average depth of 50 fsw for 70 minutes. Others may not be, and they shouldn't dive that way. Don't dive like I do, one may die as a result.

Jimmie

No further questions, your honor............... Do you realise, people may actually take what you say seriously, apply it and get into serious trouble???

I would strongly recommend the following Course.

http://www.padi.com/english/common/courses/rec/continue/multileveldiver.asp