Source for Rec Dive Tables?

[TSandM]

My understanding is that the biggest reason for PADI's development of new tables was that the Navy tables, while liberal on the first dive, were extremely conservative for repetitive diving. This was based on a number of assumptions, including the choice of controlling compartment, and that the worst case was diving after a mandatory decompression dive.

PADI's tables were slightly more conservative on the initial dive, but far more liberal on repetitive dives. They used a different controlling compartment, and did not assume a dive beyond NDLs for the first dive.

I again highly recommend the books I mentioned. If you read them, you begin to realize how murky decompression is, and how far from revealed truth any tables or computer algorithms really are.

 

[scjoe]

Obviously in the millions of dives the US Navy has done, they have not treated 20,000 cases of decompression sickness. 2% at the extreme and limited number of dives that take place for NEDU purpose or deep search and recovery is a different thing and hardly comparable to the recreational use of Navy tables. Since you feel the Scripps folks are shallow divers, the following is the full quote from Stewart:

"The program at Scripps Institution of Oceanography has historically used the U.S. Navy tables.
I had the good fortune to know Bob Workman and to work with Ed Lamphier during the 1958 atomic tests in the Pacific. The tables had just been promulgated and we put them through just about every kind of repetitive dive profile one could dream up. There were four of us from Scripps and we had an eight man Navy team working with us. Our main task was implanting and retrieving tsunami recorders near blast sites, but during that three month period we logged over 1200 dives, to depths in excess of 190 fsw.
In the years following we conducted research dives to document the sand movement in the Cabo San Lucas and Los Frailes submarine canyons. On many dives we were on the extreme exposure tables and on many others the 190-foot repetitive dive table. These projects usually involved six of us, and were conducted for a three week period each six months, over a number of years.
The Scripps program has over 200,000 cumulative dives since the early 1950s. We have had only a single case of decompression sickness. It occurred during a multi-day, multi-dive kelp research cruise. Six people made the last dives, all on the same profile. Ironically, the person who hung off at ten feet for two minutes got hit. We find that use of the U.S. Navy tables is safe and adequate. Our university guidelines for diving safety state that "Any dive table used must be at least as safe as the U.S. Navy tables."

 

[Mr Carcharodon]

Workman reported a 2% bends rate. Scripps may have done lots of dives but if we do not know the details of the dives it does not shed much light on anything.

 

[DaleC]

I will try to recall where I read about the accepted DCS risk for navy divers and post a link if I do. I do remember it having to do with the fact that they had chambers on station that allowed for immediate recompression; thus the risk, while present theoretically when using the tables, was greatly mitigated in practice.

The DCIEM tables (IIRC) were generated by monitoring thousands of both wet and chamber dives and when DCS was indicated they rolled back the limits so that the final tables represent a lower DCS risk when applied against navy tables. However, like the navy tables, they are more liberal for the initial dive and more conservative for repetive ones than PADI tables. DCIEM researchers also created the first dive computers; both a top side model and a divable version.

 

[James S]

"They are conservative and have a far less acceptable rate of DCS risk associated with them than say, the old US navy tables."

If one is using the "old" tables they should know that the USN tables are updated periodically and in fact have been recently updated.

 

[DaleC]

Well, let's say at the same time the DCIEM tables were generated.
It's not a contest.

 

[gcbryan]

The devil is in the details in this subject matter as well. As I recall (reading) the Navy didn't have a lot of experience with repetitive dives because that's not generally what they did. They had enough bodies to do longer dives and to send someone new down if another dive was needed.

Sometimes various tables that appear to be far apart aren't really when you compare the underlying assumptions of the table. One may have short NDL's because a direct ascent at 60 fpm can be used while the other may assume a slower ascent with various stops or provisos to correct for age, cold water, or whatever. People don't always take that into account when comparing tables.

As was mentioned, there's a lot of voodoo involved as well

 

[Mr Carcharodon]

This is just speculation but some of the details driving DCS rates may be the availability and cost of treatment. If the Navy had decompression chambers on site and there was no direct cost to using them economics would suggest higher usage rates than in a civilian population that did not have have ready access to a chamber and had to pay for it if they did. Availability seems to drive the utilization rates for many treatments. Anyway I do not know if the Navy and Scripps kept score the same way if you will.

 

[lekrigbaum]

Well,that's kind of overwhelming. What I was hoping to find is a set of tables that would be freely usable in a web application. I guess I'm assuming that PADI, NAUI, SDI, et al, have the set of dive tables their organization uses copyrighted. ANother question along the same line is that if the users are required to be a certified diver, wouldn't that mean that they purchased a set of tables from their certifying authority during their initial training? If so, would they be entitled to use those tables obtained from a different source, i.e. - a web app that has a copy of those tables? Thanks.

 

[Kern]

Buy any set of tables you like & use them.

Find a set on the web, borrow from a friend, etc. I doubt the table copyright police will come after you.

Some tables are in the public domain, fell free.

Some web apps are free, some aren't, but some of those are still available for trial periods, with nag screens, reduced functionality, etc.