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

[Akimbo]

Back in the day divers tended to be more fit, younger, and in general better shape.

And all males for US and Royal Navy test subjects and DCS reports from the fleets. The first female US Navy diver was in 1973. I have no idea if gender makes enough difference to impact algorithms or not, or if there is enough data available to refine them.

We did daily PT (Physical Training) when operations allowed, including divers in their early 50s on their last tour of duty before retiring after 30 years. It is not unusual for people to start diving in their 50s today and keep going for 30+ years.

The RGBM implementation on the Atomic Cobalt computer does want your date of birth, so I'm guessing adjusts the calculation for age.

 

[Eric Sedletzky]

@boulderjohn
I just ran some PADI RDP tables on a couple dives.
I did a 50’ dive to max NDL of 80 minutes, waited an hour, then went to 110’ for NDL of 3 minutes (the tables wouldn’t let me go deeper) for a total bottom time of 83 minutes.
Did the same depths but did the deep dive first
110’ for 16 minutes max NDL, waited an hour and then did the 50’ dive to max NDL for 61 minutes for a total bottom time if 77 minutes.
So doing the shallow dive first I got more bottom time according to PADI tables.

 

[boulderjohn]

@boulderjohn
I just ran some PADI RDP tables on a couple dives.
I did a 50’ dive to max NDL of 80 minutes, waited an hour, then went to 110’ for NDL of 3 minutes (the tables wouldn’t let me go deeper) for a total bottom time of 83 minutes.
Did the same depths but did the deep dive first
110’ for 16 minutes max NDL, waited an hour and then did the 50’ dive to max NDL for 61 minutes for a total bottom time if 77 minutes.
So doing the shallow dive first I got more bottom time according to PADI tables.

Yes, but total bottom time was not the issue. The issue was second dive NDL. With the shallow dive first, you got a 3 minute second dive. With the deeper dive first, you got a 61 minute second dive. If you had been using the US Navy tables, which were what was being used when the concept began, you could not have done the second dive at all.

 

[Eric Sedletzky]

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!

 

[Eric Sedletzky]

Yes, but total bottom time was not the issue. The issue was second dive NDL. With the shallow dive first, you got a 3 minute second dive. With the deeper dive first, you got a 61 minute second dive. If you had been using the US Navy tables, which were what was being used when the concept began, you could not have done the second dive at all.

That’s true.
It was just interesting to see what the difference was with the dives reversed. I’d rather do all shallower dives personally, that’s where all the action is anyway. At this stage in my life I’m done with all the deep sh!t anyway.

 

[dmaziuk]

@boulderjohn
I just ran some PADI RDP tables on a couple dives.
I did a 50’ dive to max NDL of 80 minutes, waited an hour, then went to 110’ for NDL of 3 minutes (the tables wouldn’t let me go deeper) for a total bottom time of 83 minutes.
Did the same depths but did the deep dive first
110’ for 16 minutes max NDL, waited an hour and then did the 50’ dive to max NDL for 61 minutes for a total bottom time if 77 minutes.
So doing the shallow dive first I got more bottom time according to PADI tables.

It's curious that it rounds to 6 minutes rather than 5: half-time of their fastest TC, but yeah: faster TCs off-gas faster too. So if your dive mostly loads the faster tissues (shallow dive), you should off-gas "more" during your SI after it, which should result in more total bottom time.

 

[tursiops]

At one time Pyle stops where heavily encourage, not so much now. VPM was the thing, now it isn't.
Not knocking any of these, but it shows as much as we do know and understand, there is much we don't.

Actually, it shows how unsupported fads can take hold.

 

[Eric Sedletzky]

Actually, it shows how unsupported fads can take hold.

Ha ha ha, I know where this one is going!

 

[Eric Sedletzky]

It's curious that it rounds to 6 minutes rather than 5: half-time of their fastest TC, but yeah: faster TCs off-gas faster too. So if your dive mostly loads the faster tissues (shallow dive), you should off-gas "more" during your SI after it, which should result in more total bottom time.

The RDP was developed prior to anybody understanding that theory. They probably still don’t have a full grasp on what actually happens.
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.
But don’t take my word for it, I’m certainly no expert.

 

[scubadada]

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!

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