"I'm so conservative..."

[tursiops]

The wording is tricky. I did not say that PADI requires that. I said that the course I taught (the computer version) was as I described. Yes, there are still shops that do not do it that way, but I did not teach for those shops.

Yes, there are people who say, "I am going to teach people to dive the way no one ever dives any more, and I will absolutely not teach them the way everyone dives today." I am not one of them. I admit it.

You misunderstand. It is possible to teach computers AND tables.

 

[boulderjohn]

You misunderstand. It is possible to teach computers AND tables.

Of course it is. When did I say it wasn't? I can also teach computers, tables, and how to make strawberry shortcake. I can't require proficiency in making strawberry shortcake a requirement for certification, but I can teach it to my heart's content. My student's might think it a bit weird, but there is nothing stopping me.

 

[Wookie]

You misunderstand. It is possible to teach computers AND tables.

And I contend that not teaching tables leads to people not understanding what it means when their computer fails to give them data that they can use. Teaching tables and computer is a must, not a choice.

 

[shawnhar]

And I contend that not teaching tables leads to people not understanding what it means when their computer fails to give them data that they can use.

How much of that is specifically about knowing how to use the tables, though, vs. understanding the underlying principles that they operate on?

Seems to me that knowing the details of which column I should follow across to where on that little laminated card is pretty useless if I will always dive using a computer. But without understanding WHY I was looking up those numbers on the card, and how to use that information to plan a dive, I wouldn't have known what to do with my new computer.

 

[boulderjohn]

And I contend that not teaching tables leads to people not understanding what it means when their computer fails to give them data that they can use. Teaching tables and computer is a must, not a choice.

It is simply incredible that Mark Powell wrote an entire book, Deco for Divers, in which he somehow explained decompression theory without once teaching anyone how to use a table. You should write to him and tell him how badly he screwed up.

Decompression theory is an important part of diving instruction. Divers need to understand it. They also need to understand how they can plan for it. One way to do it is with tables. Another way to do it is with computers.

 

[JohnnyC]

I don't know any OW students who have read Deco for Divers. Doesn't mean there aren't any, but generally speaking, OW students tend to only have a very basic understanding.

I think tables are important, not necessarily as a tool to understanding any underlying algorithms or anything †other than they are an excellent visual representation of the relation and effects of depth, time, and on and off-gassing. Being able to easily visualize what a 5m change in depth will do, or what an extra 20 minutes SIT will do when repetitive dive planning is the benefit. Do OW students hop in with a bottom timer and do square profile dives? Not really, unless their instructor only parks them on the sand, does skills, then surfaces. And then that really only happens in the first OW dives. In my experience students who have been exposed to tables, even if it's just used as a visual tool to show relationships, tend to have a more complete understanding of inert gas loading and decompression, or at least have more appreciation for it.

 

[tursiops]

It is simply incredible that Mark Powell wrote an entire book, Deco for Divers, in which he somehow explained decompression theory without once teaching anyone how to use a table. You should write to him and tell him how badly he screwed up.

I haven't read Powell's book, but Asser Salama's Deep Into Deco uses graphs and charts to make his points. After 120 pages, he's covered history, physiology, endless models and their differences, and talked about a number of software ways to calculate a profile. But there is nothing in the book that lets a diver go diving....they still have to get some tables and learn how to use them, or buy a computer or some software and learn how to use that. So I suggest there is a BIG difference between "explaining decompression theory" and actually giving someone the knowledge and tools they can use to go diving.

Decompression theory is an important part of diving instruction. Divers need to understand it. They also need to understand how they can plan for it. One way to do it is with tables. Another way to do it is with computers.

My observation is that the visual students latch onto tables pretty quickly as a way to learn the concepts. My other observation is that no one latches onto computers as a way to learn the concepts; they just use the computer to get some numbers out. The numbers may make sense to them, but the computer doesn't.

 

[Eric Sedletzky]

By the same token, is it wise to put the most basic recreational computer in the hands of those who don't get it.

We can talk about the dumbing down of diving, but whatever method you use to calculate your nitrogen load, you should understand it if you're going to load nitrogen.

I ran a liveaboard for 20 years. I would venture a guess that 60% of our divers had no idea what their computer was telling them. I had to add to the dive briefings that if their computer was beeping at them, they needed to look at it and do what it was telling them. I would venture a guess that 25% ignored the beeping for the entire dive (when their computer reset itself to 50% O2 and 79% N2).

What’s a person doing with a C-Card who doesn’t get it? Who gave them the card if they couldn’t demonstrate that they “get it”?

When I took OW there were just tables. Our instructor told us that the tables [and deco gas theory] was the most important thing right under “never hold your breath”. He said it was critical enough that he wasn’t going to pass anybody who didn’t get it. So we all got it, we didn’t have a choice, and the problems scrawled out on scratch paper was the proof.
How do they test for computer knowledge now?

 

[tursiops]

How do they test for computer knowledge now?

Apparently they don't, according to Wookie.

I went into a pharmacy the other day because I was comparing the costs of some prescriptions...drops for my eyes. Some of the costs were given for 3 or 5ml bottles, some for 30 or 90-day supply, and all I knew was I put one drop in each eye, each day. The nice, young, lady pharmacist came over and heard my question, looked at the piece of paper that had the 3ml bottle listed on it, punched some numbers into her pocket calculator that was in her white lab coat pocket, and wrote "30 days" on the paper. She then wrote "50 days" on the 5ml bottle page. I said what are you punching in? She said "multiply the bottle size by 20, 20 drops per ml, and divide by two 2, 2 drops per day." I said, "Cool, 10 days per ml." She said ":How did you do that?"

 

[Stoo]

I'm going to buck the tone of this thread a little, by starting with the initial post. Unless I missed something, we know nothing about this diver. He indicated that he was experienced and that he dove conservatively. But most of the posts in this thread seem to disbelieve that, and portray him as an unskilled cowboy. Is it not possible that he was in fact highly skilled and very experienced? Just because he didn't roll out a sheaf of c-cards does not mean he doesn't know what he's doing. If he is confident in his air consumption, he may well have been allowing for lots of gas to make his ascent safely. The OP doesn't state where they were diving, but assuming it was nice warm, clear water he may well have known exactly what he was doing.

Again, unless I missed it, I didn't see anything about his gas supply being depleted. Not everyone uses the same amount of gas obviously. He may well have had buckets of gas left.

As for his definition of "conservative" and using 30/85, he is going to go into decompression sooner than many. But assuming he does the required deco, and perhaps adds a few minutes for good measure, that is, at least in my book, "conservative". Changing the settings in the computer doesn't change a thing in the body of course. Would everyone feel better if he'd set his Petral at a more aggressive GF, avoided "decompression" showing on the screen, and surfacing after a 3 minute safety stop. To my mind, that is NOT conservative at all, just because the computer says "go"...

All of this is to say that while agree that there are many shortcomings in the divers methods, I think there's a little bit of judging going on.