Another Tables vs. Computers Thread

[Charlie99]

Tables use a shorter compartment time for the so-called "controlling" compartment on repetitive dives - most computers use much longer compartments for this. For example, US Navy tables used the 120 minute compartment, where as DSAT (i.e. PADI) tables use the 60 minute compartment. Dive computers will typically use their longest compartment - perhaps something in the 480 to 720 minute range. The longer the half-time on the controlling compartment, the less bottom time you get on a repetitive dive - the effect of this is that tables generally give you more bottom time on flat profiles, whereas computers generally give you more time on multi-level profiles.

Your analysis is in error.

While the dive computers track all of the compartments, including the very long half time compartments, after a typical recreational dive, the very long halftime compartments have relatively little loading and have no effect on the next dive.

If your analysis were correct, then decompression programs such as Decoplanner and V-Planner, since they also track the very long halftime compartments, would give you less time on flat bottom profiles than tables. You can easily verify that this is not true. Nor is your original assertion.

 

[Charlie99]

because you have to make the computer "happy"

an example. My buddy uses his computer as a Bottom timer (as do I -- i like the ability to download depth profiles). But he had been lazy and was running it in air mode, but we were diving 32%.

We did our dive, and on the way up, even though we were well within our minimum deco limits for 32%, his computer (because we were a bit sloppy) said 11 minutes deco. We ignored it (as it wasnt really true) and got out of the water, and he got locked out and had to borrow a bottom timer. Should I really have spent 11 useless mintues "decompressing" ?

Rather thasn spending 11 useless minutes, you and your buddy should learn how to use your tools properly. Too bad you and your buddy weren't able to catch the error during your buddy check.

Do you have any example where a properly used computer has forced anyone to dive a profile other than what you desired?

A lot of people have parroted the "doesn't give credit for deep stops" line, but if you actually look at what happens, you will find that the computer does indeed properly account for offgassing in the faster compartments.

You, at least, have not parroted the false logic about a dive computer forcing you to immediately pop up to the ceiling depth that will be shown when in deco.

 

[H2Andy]

But he had been lazy and was running it in air mode, but we were diving 32%....

...his computer (because we were a bit sloppy) said 11 minutes deco. We ignored it (as it wasnt really true) and got out of the water, and he got locked out and had to borrow a bottom timer. Should I really have spent 11 useless intues "decompressing" ?

garbage in, garbage out

 

[tedtim]

If I were to be taking a canoe trip in the deep, darkest areas of Canada, I would prefer to have an axe as opposed to a chain saw. If I lost the fuel for the chain saw, it would not work, whereas the axe would.

K, take it from someone who has been there. You would be better off taking DEET than either an axe or a chainsaw. Once the mosquitos get to you it would not matter if you had an axe or a chainsaw.

Still, both an axe and a chainsaw are equally dangerous if not used properly.

 

[Scubakevdm]

K, take it from someone who has been there. You would be better off taking DEET than either an axe or a chainsaw. Once the mosquitos get to you it would not matter if you had an axe or a chainsaw.

Still, both an axe and a chainsaw are equally dangerous if not used properly.

Also, while an axe is enough to kill, or at least incapacitate 50% of Canadian mosquitos, the other 50% will take it from you and use it against you.

 

[H2Andy]

i think you're thinking of Canadian waterfowl. the mosquitos get almost as big,
but lack the brainpower to disarm an opponent

 

[Charlie99]

It is truly amazing how many times people think that you have only an "either-or" choice. As in, I must bring EITHER the axe OR the chainsaw, when there isn't any reason that you can't bring both, and some DEET too.

And maybe even use both computers, tables, mental tracking, and a large dose of seat-of-the-pants flying.

 

[1_T_Submariner]

So not to add to much fuel to the fire here. I tried to follow the tables after I first got my computer and found that after doing 3 multilevel dives starting deep (80-110 feet) and working our way up (Most of the dive was 30-50feet) that I couldn't make the 4th dive but, my computer calculated that I had plenty of NDL time left. So do you make the dive or not?

 

[H2Andy]

i'd follow the more conservative result and not make the dive

(and next time, won't use the tables at all so i can)

 

[tedtim]

i think you're thinking of Canadian waterfowl. the mosquitos get almost as big,
but lack the brainpower to disarm an opponent

Mosquito = provincial bird of Manitoba and part of Northwestern Ontario. I have a t-shirt somewhere to prove it. We don't live in that region anymore, but they are still a pain.