Computer vs tables

[Blackwood]

Would you plan a multilevel dive with the RDP?

Theoretically, if I know a site well enough to pre-plan a multi-level dive, I COULD use a table.

Realistically? No. I'd dive and figure the decompression based on my actual profile, either using on-the-fly techniques or with a computer.

If it fails, you can tell by looking up when you are to reach 15 fsw
...

I can't.

Around here, viz is often substantially below 15 feet. And every time I've dove in "vacation" conditions, I was disoriented by the high viz. I remember looking up and seeing the hull of a Bora Bora Blue Nui dive boat from about 100 feet, and it looking like 20.

I CAN, however, fly an SMB and use the knots I've tied at 10' intervals to know how deep I am.

 

[Charlie99]

What is a "flatwheel"?

It turns out that one can use a table very similar to the PADI RDP to duplicate the calculations of the PADI Wheel. Since it has all of the functionality of the PADI Wheel, but in a flat table, I call it the "flattened wheel".

It came out of some work I did while studying the PADI RDP. I ended up reverse engineering it to figure out what exactly the pressure groups really meant.

Attached is an Excel file that uses the basic ongassing equations and the basic parameters of the DSAT/PADI deco algorithm to generate an RDP-like table. It also has a table that simplifies gas planning. I just included the same depths as the PADI RDP, but since the equations are all there, you can add back in the 5' depth increments if you want.

The 5' depth increments are on the GIF file of a "flattened wheel" in my Scubaboard photo album. It was an interesting mental exercise, and I was able to verify that it give the same answers, to within a minute or two, as the PADI Wheel, but as I noted in an earlier post, in real life I just use the RDP in the same way to get a rough ballpark validation of a proposed multilevel dive profile, and then use the dive computer to monitor it in realtime.

 

[RS]

Charlie99,

Thanks for posting the table. That must have taken alot of head scratching. I see the 60 min compartment half-life correlation in the SI row but it's going to take me awhile to put the rest together. This is giving me something to think about for the new year...

Thanks again to charlie99, blackwood and stagraven for bringing up multi level planning.

End of hijack.

Oh, yeah, nereas, I think the cochran computers will also guide you through deco dives.

 

[nereas]

...

Oh, yeah, nereas, I think the cochran computers will also guide you through deco dives.

Cochran Commander? Didn't those have some kind of issue associated with them? Has that been resolved now?

 

[amascuba]

Oh, yeah, nereas, I think the cochran computers will also guide you through deco dives.

Giving a person a dive computer and telling them to follow it blindly is like giving a blind person a gun and telling them to just point and shoot.

 

[AndrewJD]

Hi all,

I haven't read some of the later posts yet but I would like to throw some of my thoughts out there.

So far the discussion has been on what's better Table vs. Computer vs. know your dive site etc... Each of these represents a "strategy" that a diver is going to use in in their decompression. As a strategy, each has it's advantages and disadvantages. Is any one better then the other across the board for all divers? I doubt it.

Now, IMO, (and a few others) the important thing is that during a dive (or period of diving like a week long trip) a diver chooses their strategy and then follows it. If your strategy is your computer then great. Follow it. But what happens if your computer fails, say day three during your seven day trip, what now? Your strategy has failed. Do you go to another computer that may be running a different model inside the black box. Do you now just dive tables? Change strategy?

How about on that 200 ft decompression dive. Your computer fails? What now? Back up computer? Back up to the backup computer? For that matter, how do you know it has failed? Multiple computers reading different things? Bottom timer/depth gauge to track depth and time separate from your computer? Still, what's your strategy now? Whip out your pre-cut contingency tables? What if you failed to anticipate your current situation? Anyway, enough of that you've got the point I hope.

Now if you learn some decompression theory, develop some situational awareness allowing you to pay attention to depth and time, become adept with some simple math and plan your deco in your head (or wet notes), then you have a robust and flexible strategy that will probably not fail you at a less then convenient time. Furthermore, your strategy is applicable to many different types of diving and can be built upon as you advance.

So, I hope these thoughts will positively contributed to the discussion. Happy New Year!

Jonathan

 

[Jasonmh]

...Is there a method to using tables which would allow the apparent flexibility offered by using a computer??

TIA

Mark

I know that some of the threads here have gone on to talk about traditional tables and other methods, but since you were asking about DIR directly, the answer is yes there are methods that offer as much (I would say more) flexibility as using a computer. On my last liveaboard trip I was getting as much bottom time as other divers using their computers.