Plan your dive and dive your plan

[TMHeimer]

I use tables and computer. A majority of my boat dives are square profile, so can be planned as such. I use watch and analog depth gauge. Computer as a backup and a curiousity to look at for remaining bottom time. I have a general knowledge of my air consumption and have the Air table memorized (Nitrox ones not so much). For an 80 foot "bottom only" dive I will say to an instabuddy "Lets do 10 minutes out on the wreck, cross the wreck & return for the next 10 minutes, then putter around the anchor line (which we have hopefully not lost track of) and ascend". So we're 5 minutes short of the 30 min. NDL. If no anchor line, same plan and ascend (without reference line) to safety stop. Plan varies of course with depth and other conditions. With most of my charter dives having been the typical 2 tank dive trip, there has been not a lot of variation.

 

[agilis]

... that's like saying if you don't know how to use a slide rule, you don't really know how to do math ...

... Bob (Grateful Diver)

No, it's not. A better analogy would be that not understanding logarithms means you don't know mathematics. Slide rules are, after all, a kind of basic one functiom computer.

 

[emoreira]

Understanding how tables work and planning dives with tables, helps you understand what a PCD does and how.

 

[MXGratefulDiver]

Understanding how tables work and planning dives with tables, helps you understand what a PCD does and how.

I agree ... they're great for teaching the relationship between how deep you can go, how long you can stay, and how much time you want to be out before your next dive. After OW class, I just don't see much of a practical use for 'em anymore ...

... Bob (Grateful Diver)

 

[freewillie]

Yes, understanding algorithms and dive tables is important to help plan a dive. But with the advent of dive computers the actual dive may be slightly different than what you would plan.

In a very real sense the computers are safer for extending bottom time. The tables and algorithms assume deepest dive first then diving in a square pattern as you ascend. These days that is not an absolute limitation and the diver with a computer can dive multiple depths and still stay withing NDL's for recreational diving.

The basic premise is still the same. You have a certain amount of time at a certain depth to avoid a decompression obligation. In general the deeper you go the shorter your time before you incur a decompression obligation. I tend to be more of a big picture person than to worry about minutia. It's not that I don't think tables and algorithms have their place its just that dive computers make it that much easier and safer. Slide rules are still useful and still accurate, but why not just use a regular calculator?

 

[Prof Diver]

I believe PADI has moved away from Tables and introduced a computer (not a dive one), but instead of finding and following the tables, you key in the details and bang, there's your group.

I'm still and old fashioned wheel table diver. Though I have my computer on me for backup and as a timer, but I still use my tables and basic maths

 

[TMHeimer]

It's not that I don't think tables and algorithms have their place its just that dive computers make it that much easier and safer.

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Easier in some circumstances (multi level, gradual ascent dives, etc.) for sure, safer--not so IMO. A dive computer tells you your NDL. And that theoretical limit (based on the tables) is a REAL limit. If you go over that limit by one minute you are in deco. With tables and a square profile: If your max depth is 100' and you go to the 20 minute limit exactly (not a good idea for sure), you are probably not right at the limit because you probably spent most of the 20 minutes at 97' or so. More conservative. The comparison has been debated ad nauseum, and it just winds up being personal preference anyway. If I am depending on my computer for my NDL, I tend to be a little more cautious about being close to that limit.

 

[diverrex]

I am surprised at how many people still use tables. Most of our diving is multilevel and often times until we descend and look around awhile we don't know what depth we will be at, and that depth will also change as we move from one area of interest to another. Using a computer for those types of dives seems much easier. Of course many of those dives are also at relatively shallow depth, maybe 45 FSW or so and generally with a 60 minute dive time so NDL just doesn't enter the picture either tables or computer.

I just looked at our last boat trip, 4 dives with max depths ranging from 41 - 85 and surface intervals between 45 - 50 minutes. The tables showed lots of violations while the computers were always at least 6 minutes from NDL.

 

[TMHeimer]

I am surprised at how many people still use tables. Most of our diving is multilevel and often times until we descend and look around awhile we don't know what depth we will be at, and that depth will also change as we move from one area of interest to another. Using a computer for those types of dives seems much easier. Of course many of those dives are also at relatively shallow depth, maybe 45 FSW or so and generally with a 60 minute dive time so NDL just doesn't enter the picture either tables or computer.

I just looked at our last boat trip, 4 dives with max depths ranging from 41 - 85 and surface intervals between 45 - 50 minutes. The tables showed lots of violations while the computers were always at least 6 minutes from NDL.

Well yeah, as I said-personal preference. Most of my diving is not multi level being a shell collector--they are usually on the bottom. The ones that are multi level I use the computer. Most of my boat trips are 2 tank dives, so my RNT will be less than yours, doing 4 dives. And many of my dives are shallow shore dives, and as you said, tables and computers become equally useless.