Do the dive tables have a limit on the number of dives per day?

[Eric Sedletzky]

Hi @Eric Sedletzky

Do the old PADI tables have a date on them? The PADI RDP came out in the late 1980s, 1987 or shortly thereafter.

Interesting how the old PADI/USN tables show deco time for overstaying the NDL, the RDP did away with that

The old PADI tables have a date of 1981 on them, and the RDP has an initial copyright date of 1985 with revisions going up to 1994

 

[dmaziuk]

The RDP was developed prior to anybody understanding that theory. They probably still don’t have a full grasp on what actually happens.

I don't think so: DSAT report starts with "RDP was developed by adapting Haldane's computational algorithm used by U.S. Navy to the special needs of recreational divers" and goes on to explaining the science, assumptions, testing procedures etc. that went into its development, in great detail. I assure you they understood the theory very well and it hasn't changed that much since.

But that relates kind of to my earlier question about loading up the faster tissues first on a shallow dive thereby lessening the allowable bottom time on the second deeper dive which would begin to load up the slower tissues. The longer you stay deep the faster the slow tissues load up exponentially. So it may actually be safer to do shallow dives first then do deeper dives later.

Yes, I saw your question and had it in mind: you will have less NDL time on your second dive either way, but fast tissues will off-gas during SI, and your NDL for the next dive will be controlled by what's left in the slower tissues. Deeper dive will push more gas into them and more will still be there after SI, so you end up with greater total residual loading.

I suspect the differences will mostly disappear by the 3rd or 4th dive -- although all this stuff is very profile-dependent.

 

[Akimbo]

I assure you they understood the theory very well and it hasn't changed that much since.

This is always a subject of debate and interpretation, which reminds me of the famous quote:

“ Ask a new diver what causes DCS and he'll say he doesn't know. Ask an instructor on ScubaBoard and he'll go on for days about micro bubbles, M-values, tissue stress, etc. Ask a research scientist who has studied DCS at Duke for many years and he'll say he doesn't know. ”

— Unknown

 

[Celt]

Have you seen this

 

[boulderjohn]

Hi @Eric Sedletzky

Do the old PADI tables have a date on them? The PADI RDP came out in the late 1980s, 1987 or shortly thereafter.

Interesting how the old PADI/USN tables sho

I found some old PADI tables I forgot I had.
They appear to be based straight across from USN tables.
Compare them to the RDP, quite a difference!

For those who are not clear on it, the tables shown here are not the PADI RDP; they come from well before that, and, yes, they are essentially the US Navy tables. The earliest copyright on the RDP instructional book I have is 1985.

 

[boulderjohn]

This is always a subject of debate and interpretation, which reminds me of the famous quote:

“ Ask a new diver what causes DCS and he'll say he doesn't know. Ask an instructor on ScubaBoard and he'll go on for days about micro bubbles, M-values, tissue stress, etc. Ask a research scientist who has studied DCS at Duke for many years and he'll say he doesn't know. ”

— Unknown

That is a very much shortened version of a much longer statement by Richard Pyle.

 

[scubadada]

The old PADI tables have a date of 1981 on them, and the RPD has an initial copyright date of 1985 with revisions going up to 1994

Are there any references to the USN tables on the 1981 PADI tables? These are, in fact, exactly the USN tables in 1981.

I was certified in 1970 with USN tables. The RDP changed the controlling compartment from 2h to1 h, making repetitive dives practical, a huge advance.

 

[boulderjohn]

I was certified in 1970 with USN tables. The RDP changed the controlling compartment from 2h to1 h, making repetitive dives practical, a huge advance.

A key goal of the PADI RDP was to cut down the huge surface intervals required by the US Navy tables.

• PADI's research showed that for most dives in the range we now refer to as recreational diving, the 40 minute compartment would work, but they ended up going with the 60 minute compartment. This made the biggest difference, because the navy used the 120 minute compartment.
• They shortened the first dive NDLs, which also allowed for shorter surface intervals. For example, at 100 feet, the Navy NDL was 25 minutes, and on the RDP it was 20.
• Another big impact was in nearly doubling the number of pressure groups. This significantly reduced the rounding errors, which of course were always to the more conservative pressure group.

 

[tursiops]

Are there any references to the USN tables on the 1981 PADI tables? These are, in fact, exactly the USN tables in 1981.

I was certified in 1970 with USN tables. The RDP changed the controlling compartment from 2h to1 h, making repetitive dives practical, a huge advance.

Here is the 1983 version of the PADI tables; I think this was the last before the RDP. No mention of the Navy tables.

 

[tursiops]

Another big impact was in nearly doubling the number of pressure groups. This significantly reduced the rounding errors, which of course were always to the more conservative pressure group.

The Navy used A-Z for pressure groups including both NDL and deco dives.
PADI's RDP used A-Z just for NDL dives.