Naui/Jeppeson/Padi Dive Tables

[delgriffith]

Why are Padi tables more liberal than Naui tables?

Dive 1: 70 feet for 40 mins

Naui: H Diver
Jeppeson: H Diver
Padi: T Diver

SIT: 1.5 hrs

Naui: F Diver
Jeppeson: F Diver
Padi: D Diver

Dive 2: 60 feet

Naui: RNT is 36 mins, ADT is 19 mins
Jeppeson: RNT is 36 mins, ADT is 19 mins
Padi: RNT is 16 mins, ADT is 39 mins

This pattern holds for all the dive profiles I checked. Not being critical, just wondering...why the difference? This also begs the question, are the computer algorithms closer to Naui or Padi tables?

Note that the Padi tables also require less SIT than NAUI to gain an equivalent ADT for the next dive.

Thanks!!!!

 

[Paulmal]

PADI tables are designed for non-deco dives and were designed so you do not have to have a 1 hr surface interval. NAUI tables are modified Navy dive tables which were designed to allow for deco, and required an hour surface interval to get decent credit on your pressure group.
As for computers it depends on the algorithmic that they are using.

 

[delgriffith]

Thanks for the reply. Unfortunately it's still not clear to me why there is a significant difference in ADTs between the tables. Please understand I have no "horse in the race".

Looked at another way, in the example I gave, we have 19 vs 36 mins of BT or ADT (whichever you prefer). How would that work in a group dive if people were using different tables/computers?

Thanks again for your kind reply.

 

[Mr Carcharodon]

The different tables use different assumptions on what tissue compartment controls the dive. The Navy tables assumed one relatively deep dive to if not past NDL. Later DSAT (PADI) suggested that recreational profiles were more typically repetitive short and shallow and that caused them to shift the controlling compartment. Lippmann’s book “Deeper into Diving” has a good treatment of the different models.
Computers do not need the same degree of simplification that required to get a plan down on two sided card. They consider all tissue compartments and control off the one that is closest to the limit.

 

[DCBC]

Decompression Table development can be a long and complicated process. The Authority creating it must first elect which model to work from (the difference between the Haldane and Kid-Stubbs model, for example). The format used in each of these tables are not necessarily the same. The Authority must choose various options for how the mathematical model will be applied. A different level of conservatism is worked into the end result which naturally affects the end result. Out of the Tables currently available, the DCIEM table is the most conservative and will provide the largest margin of safety to the Diver.

 

[delgriffith]

Thanks for the posts! Is my assumption correct that the Naui tables use the DCIEM table?

 

[DCBC]

Thanks for the posts! Is my assumption correct that the Naui tables use the DCIEM table?

No; but you can get more information on the DCIEM Tables by downloading their manual at http://www.divetable.de/skripte/p125936.pdf You walk a path that can be confusing... The tables themselves can be purchased from Amazon (http://www.amazon.com/NAUI-DCIEM-Sport-Diving-Tables/dp/B001MZVUX8).

 

[rx7diver]

All,

I read these types of threads with interest and not a small amount of curiosity--always! They always lead me back to a fundamental question I have not yet found a satisfactory answer to, not in over 25 years of diving: Why should a table-user even care what particular flavor of whose particular theory was used to develop the table? For me, what is of paramount importance are (1) was the table sufficiently animal- and human-tested and verified, and (2) did these tests emulate the type of diving I do? (For example, if I tend to do a lot of yo-yo diving, then it would be important to me to know whether a particular table was tested and verified using square profiles, only.)

Safe Diving,

rx7diver

 

[delgriffith]

I agree completely on the testing. I will need to delve a bit deeper into the animal/human/experiential testing done to support padi, naui, dciem, usn tables etc. My preference would be tables that have been time-tested across a variety of dive types, and tables that are conservative across dive types.

 

[rx7diver]

My preference would be tables that have been time-tested across a variety of dive types ...

Even better!