more DSAT/RDP questions

[blackwater]

O.K.
I was reading Jordons thread on the RDP, and looked at his web site. I decided it would be a good math review to plug the equations into Excell and plot some of the data behind the RDP. I had e-mailed PADI to get the pamplet on the derivation of the tables but got no response (just sent a follow up).

so here are the questions:
1) The plan is to calculate the tissue partial pressure which the diver needs to accend at 60 Ft/min. to get to the surface with a tissue pressure of the M-value.
2) calculate the time at depth to reach this tissue pressure.

My numbers are coming in about 10% off.


So, I was checking into where variances could be occuring....
1) is this two step profile the correct approach to match the RDP?

2) for atm, is their a more precise conversion factor than 33ft.of sea water? how about bar vs. Atm, these seem to be "almost" the same.

3) for pressure, was H2O vapor pressure used in the calc. (a fixed pressure). how about C02/O2 and the oxegen window, & respitory quotient?

4) is their a more precise percent used for nitrogen, (did they lump the other trace gases in to the nitrogen percentage?).


I would feel better if the numbers worked out, and it's interesting to see the affect of tweeking different values on the calculated Deco-time.

then it's onto VPM, RPGM & micronuclii.

thanks in advance
GT

 

[Dr Deco]

Dear GT:

It would be best to have the booklet from DSAT/PADI on the dive tables and planner. There is some degree of rounding off in the calculations and this is explained in the booklet. I do not remember the calculations (and they were performed by Dr Rogers, anyway).

If you “tweak” some of the number, you will find some variations in the length of bottom time. What is important to remember is that there are no physical realities to the table limits. It is basically derived from the no-decompression limits of the laboratory performing the initial NDL testing. It depends on test conditions and the number of test subjects. Some conservatism is added in accordance with the designated use of the table (recreational, military, commercial).

What is not included is the activity after the dive itself. Most test divers simple sit down after the test dive. None of them carry air cylinders in the laboratory. No go outside to play volleyball. When scuba divers perform these activities, they must realize that this is outside of the table test protocol. These generate micronuclei and can be an initiators of DCS.

Dr Deco
:doctor:

 

[blackwater]

Yes, I would like to get ahold of the booklet. But since PADI is not responding to the emails, I'm trying alternate avenues. It seems as though some members of this list do have copies of the pamplet

My understanding is that for DCI, there are two general factors, the super-saturation which can be directly modeled mathmatically, and the micronucli which are only indirectly modeled. The Dive industry has (for better or worse) focused on the mathamatical models and largly ignored the micro-nuclei.
I just Finished your Seminar on Catilina Is. (Adv. Deco. Phys.) And liked the information on micro-nuclei, as it gave a rational to the chaotic nature of the bends, but being an engineer I also like the chance to brush off the Ordinary Differential Equations and put them to a real problem. (in Theory any way, as I'll still use my dive computer for timing and planning).

Thanks
GT
(Alice's brother)

 

[Dr Deco]

Dear GT:

It was a nice surprise to see you at Catalina

Mike Powell (aka Dr Deco):doctor: