Nitrox Class Without Tables or Math...OK?

[MikeFerrara]

Which brings us back to the topic of the thread. Computers or tables = safe rec nitrox diving.

I would certainly agree that a successful dive can be conducted with either though I'm not in favor of leaving too much of the theory out of a class. It's not because I expect the student to die because of it but rather because it's fast and easy to teach and can provide the student with more choices in their diving. IMO, it's a small investment with a rather large potential for a good return. As I've said survival is only one consideration. Versatility and convenience are others.

 

[H2Andy]

What about the implied subject, Andy? His use of "which" was merely a feint common to Elmers.

"which" is sometimes used as a noun ("Which is yours?")

alas, in the clause in question:

all of which are visible to the diver well before the alarm goes off.

"which" is preceded by a preposition ("of"), and the subject of a sentence
can never follow a preposition (because the preposition makes what follows
a prepositional clause, and a prepositional clause can not function as a
subject).

this clause has no subject, and is therefore not an independent clause

 

[JS1scuba]

Which brings us back to the topic of the thread. Computers or tables = safe rec nitrox diving.

It all depends.

And what it depends on is your gas supply. If you have sufficient gas supply and you have a specific depth you want to work at then either will work.

Square profile dives for the most part are exactly the same result with either tables or dive computer. (given the variations of the algorithm)

however ......... MOST recreational divers do NOT do square profile -- they take their time getting down then do up and downs throughout the dive and then progress shallower towards the end of the dive. A typical caribean dive is set up that way so that on a single tank you can pull of a 60-75minute dive (boyles law)

For those situations the only way to calculate the dive in real time is with a dive computer. The "flat" tables are out the door. Now you can cut tables with a program like NAUTILUS and put in the multi level aspects of the dive but then again you must follow the plan.

The multi-level dive computer combined with the ability to program in the nitrox value makes simple nitrox diving an absolute perfect match. (dont forget to add in an Oxyspy to analyze the gas)

..........

Someone made mention that it was odd that a guy who has written so much on nitrox (me) can take such a simple stance on "Easy Nitrox" .... well here is why. Easy Nitrox is a "quick start" it has some simple rules to follow. So long as you follow them it works great. When you want to do more than "easy nitrox" and want to get into specific mixes for specific depths, best mix, full no-stop time at specific depths in square format, acceleration of decompression, optimizing ascents for multi-level no stop dives, multi day repetitive diving, and messing with diving at altitude you need a LOT more information. That's when you step up to a "math" type nitrox course or advanced nitrox courses.

Dive computers are a fact of diving today. Just like the PC / Mac, cell phone, and PDA are facts of life for communication. Without the computer I could not reply to this simple question in this manner. Don't buck the dive computer ....... they are quite safe to use. Just read the manual first!

Cheers

 

[TheRedHead]

LOL. I never got anywhere arguing with my English professors.

 

[H2Andy]

we are geeks!

revel in it

 

[Soggy]

So the "Check Engine Light" never comes on because you removed the bulb? That's too funny. You have no clue if you have ever violated your PC then. Too funny!

More like, the rev limiter hasn't kicked in because I never exceeded 7000 rpm because I was paying attention.

Occasionally, I have dropped to 73 feet on a EAN50 mix. My computer, which has no knowledge of what mix I was breathing, didn't know that I had violated my MOD by 1 foot, and thus did not beep at me, However, I, being smarter than my computer, was able to recover from this error without being beeped at and flashed.

Hmm...violating, flashing...sounds like spring break in Panama City.

 

[minnesota01r6]

Occasionally, I have dropped to 73 feet on a EAN50 mix. My computer, which has no knowledge of what mix I was breathing, didn't know that I had violated my MOD by 1 foot, and thus did not beep at me, However, I, being smarter than my computer, was able to recover from this error without being beeped at and flashed.

A computer's usefullness in diving isn't that it is smart - it is only as "smart" as the diver makes it. The computer's usefullness comes in because it isn't able to get distracted or task loaded. It would have told you (perhapse only 1/2 a second before you realized it) that you were exceeding MOD for your mix, had you programmed it to do so.

 

[Soggy]

A computer's usefullness in diving isn't that it is smart - it is only as "smart" as the diver makes it. The computer's usefullness comes in because it isn't able to get distracted or task loaded. It would have told you (perhapse only 1/2 a second before you realized it) that you were exceeding MOD for your mix, had you programmed it to do so.

Aside from the headache and taskloading required to program multiple gasses into a computer...that 1/2 second would have helped me how?

 

[friscuba]

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.

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.

I think we're in agreement on the multilevel diving. It essentially takes the tables out of the equasion. My original post was trying to get across the point that the reality is that many or most of the critics of NetDoc's course which teaches nitrox diving saftety without concentrating on tables an formulas , themselves very likely do not follow strict table rules or formulas in thier everyday dive practices. .. therer's no real reason to be able to do the math if you follow safe practices. There are lots of ways to dive safely, I don't see any problems with the SDI approach. I just find it odd that people who are not diving strictly by the tables or formulas, are criticising the class.

later,

 

[Rick Murchison]

If your computer alarms in these situations, I would expect it would flash a warning light, blink, or do some other type of visual warning as well as beep. If you haven't ever seen the warnings, you are not paying attention to your guages. You also might do well to investigate what is causing the alarm and then decide to ignore it or pay attention to it. After all, even experienced divers can make mistakes. Why dive with a computer if you aren't going to pay attention to it?

Good grief!
Blinking and flashing gauges are no more useful when you're framing the photo than are audible alarms you cannot hear. You'd better just know where you are, how deep, how long you've been there, how much gas you have and what your decompression status is without the idiot lights.
Now, that said, this is about recreational diving... as you move into more complex systems, and particularly systems that can kill you without any input from you, then alarms become a whole new game. A "master caution" light or tone that can direct the diver to the problem child (low PO2, for example) is a useful and at some degree of complexity, necessary part of the diving system. But for recreational air and Nitrox diving, which lacks the "sneak-up-on-you" nature of, say, CCR diving, alarms are just a nuisance to me.
If you like 'em, by all means use 'em. I use computers... but I use 'em as additional tools, not as the end-all of dive planning and execution.
Rick
Rick