different dive tables

STOGEY · Jun 4, 2005

Hey the other day I ws looking at two of my dive tables. One of the tables I got while taking my padi basic open water course, the other I got at my dive shop. Anyways while looking at the depths I noticed that there were different allowances for total depth time for the same depth. For example 70 ft in the ndl a list in one of the tables would say 55 minutes, 70 feet on the other dive table would say 40 minutes.

I also have a dive computer, and I do consult the tables often before I go on a dive. That way if there is something wrong with the computer I have something to go by.

My question is which table would I pay more attention to, and would it be harmful if I were to take the 55 and 40 minutes and split the difference and put it to about 45 minutes?

FZJ80 · Jun 4, 2005

According to the PADI RDP, Wheel, and eRDP, the NDL for a depth of 70 feet is 40 minutes. The SSI table also gives 40 minutes as the NDL for 70 feet.

Stick with 40 minutes.

Charlie99 · Jun 4, 2005

STOGEY:
For example 70 ft in the ndl a list in one of the tables would say 55 minutes, 70 feet on the other dive table would say 40 minutes.

55 minutes at 70' is a very agressive NDL. Even the old US Navy tables were only 50 minutes at 70'. The Navy has since reduced the 70' NDL down to 40 minutes in repsponse to doppler tests that monitored bubble formation.

What was the table with 55 minutes at 70'. Is it possible that you are looking at a table designed for Nitrox rather than air???

Charlie

STOGEY · Jun 4, 2005

at 40 feet one says 205 minutes, the other 200. At 60 ft one says 60 minutes, the other says 55. At 100 feet one says 20 minutes, the other 25 minutes.

These are just some examples.

Don Burke · Jun 4, 2005

STOGEY:
Hey the other day I ws looking at two of my dive tables. One of the tables I got while taking my padi basic open water course, the other I got at my dive shop. Anyways while looking at the depths I noticed that there were different allowances for total depth time for the same depth. For example 70 ft in the ndl a list in one of the tables would say 55 minutes, 70 feet on the other dive table would say 40 minutes.

STOGEY:
at 40 feet one says 205 minutes, the other 200. At 60 ft one says 60 minutes, the other says 55. At 100 feet one says 20 minutes, the other 25 minutes.

Interesting.

The old Navy tables call for:

35 - 310
40 - 200
50 - 100
60 - 60
70 - 50
80 - 40
90 - 30
100 - 25
110 - 20
120 - 15
130 - 10

The PADI tables call for:

35 - 205
40 - 140
50 - 80
60 - 55
70 - 40
80 - 30
90 - 25
100 - 20
110 - 16
120 - 13
130 - 10

I am very interested in where that other table came from. I would not use it, but I would like to learn the history of it.

cudachaser · Jun 4, 2005

My agency (NASE) uses the Navy Doppler tables...These tables are significantly more conservative than PADI tables...I introduce my students to both, emphasizing the NASE tables.

The bottem rule talking with DAN experts...the ascent is critical...much slower than 60 fpm...know how the NAVY determined that rate? The crane that was used to lift hard hat divers out of the water was geared to 60fpm.

The slower the ascent rate, less than 30fpm is accepted. On way to judge this is coming up at the same rate the smallest bubbles rise around you, they come up at around 20fpm

Joe

pdoege · Jun 4, 2005

All of the tables are going to vary a bit. Most of the US ones seem to be based on Navy tables that have been modified with doppler info. There are others, like the DCIEM tables and whatnot.

However, the NDL values on any given table are theoretical in nature and there really doesn't seem to be a right/wrong answer as to what the real NDL actually is.

If you mind your Ps and Qs then you can get away with aggressive dives, but if you don't....

Stogey, according to VPlanner, the dives that you give as examples (100' for 20 minutes on air) are decompression dives. My SSI tables say that they are NDL dives. Which is correct? Both.

Best of luck,
Peter

Walter · Jun 5, 2005

What tables do you have?

Don Burke · Jun 5, 2005

I think I found where these numbers are coming from.

STOGEY:
For example 70 ft in the ndl a list in one of the tables would say 55 minutes, 70 feet on the other dive table would say 40 minutes.

55 minutes is what the PADI tables give for 60 feet. 40 minutes is what the PADI tables give for 70 feet.

STOGEY:
at 40 feet one says 205 minutes, the other 200.

205 minutes is what the PADI Tables give for 35 feet. 200 minutes is what the old Navy tables give for 40 feet.

STOGEY:
At 60 ft one says 60 minutes, the other says 55.

60 minutes is what the old Navy tables give for 60 feet. 55 minutes is what the PADI tables give for 60 feet.

STOGEY:
At 100 feet one says 20 minutes, the other 25 minutes.

20 minutes is what the PADI tables give for 100 feet. 25 minutes is what the old Navy tables give for 100 feet.

My guess is that someone did an exceptionally crappy job of manually copying the tables (or putting them in a computer file) and you have the result.

STOGEY · Jun 7, 2005

Also when I bought the tables I even though the dealer is reputable, but much of his equipment doesn't seem to be too up to date. Sort of like buying a 2004 dodge dakota in 2005. Its still good equipment, but some of the specs may not be what they would be if they were designed more recently.

I agree that some tables probably do vary, and they are produced for ideal conditions and for the average person. But not everyone is an average person, so I consult the both of the tables along with my computer.

different dive tables

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