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#7073 - 10/06/05 07:45 AM Defective Dive Tables
RAH Offline
avid diver

Registered: 07/25/05
Posts: 15
Loc: Long Beach
I was originally open water certified by SSI, but am now taking some PADI courses. I still use my dive tables from SSI, which are based on the Navy tables. When working my dive profile, I sometimes run into situations where my Repetitive Group is different than my PADI teammates. The instructor will check my work on my tables, and find them correct, however the Repetitive Group IS different from the PADI answer. She mentioned that the reason may be because the SSI tables are based on the Navy tables, and therefore not as conservative as the PADI tables...or that perhaps my tables are defective and should be replaced. She mentioned that she thought there was a website that gave information about serial numbers of dive tables that were defective, but she didn't know the website address. Does anyone know the web address of such a website, or offer any explanation as to the differences I'm experiencing in SSI versus PADI dive tables? Any suggestions? Thanks.

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#7074 - 10/18/05 09:22 PM Re: Defective Dive Tables
scuba-alex Offline
avid diver

Registered: 07/11/05
Posts: 7
Loc: S.F. Bay Area
Try this website. Some good educational stuff there.
http://www.aquaholic.com/table/

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#7075 - 10/25/05 12:59 AM Re: Defective Dive Tables
BrianO Offline
veteran

Registered: 05/04/01
Posts: 289
Loc: Irvine
This is a great question.

The first answer you got from your PADI instructor is the right one. The Navy tables were set up for young men between the ages of 18 and 25 in peak physical condition. Navy divers (not particularly combat swimmers) also conduct their activities with surface support such as portable recompression chambers and hyperbaric medical personnel topside to attend to them if any symptoms of DCS appear. This was the case when the original tables were formulated and it has changed very little over the last 60 years.
Recreational divers do not need the aggressive profiles allowed by the surrounding conditions that military personnel and their support crews can practice. The added safety factors built into recreational tables are guidelines that allow people in more average physical condition to enjoy diving in a more relaxed fashion with the intent that no additional support be necessary for their overall safety and well-being.
Regardless of the name of the training agency, if you are taking their class, you should be using their support material. This will avoid confusion and give everyone in the group/class the same pressure group profiles for depth and time.

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#7076 - 10/27/05 10:09 AM Re: Defective Dive Tables
RAH Offline
avid diver

Registered: 07/25/05
Posts: 15
Loc: Long Beach
Thanks so much for the great replies everyone! Guess it's time for me to go out and buy some new PADI dive tables!

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#7077 - 11/03/05 02:34 PM Re: Defective Dive Tables
BrianO Offline
veteran

Registered: 05/04/01
Posts: 289
Loc: Irvine
Either new tables or a good inexpensive computer. A computer will do the tables for you about every 2 seconds so you get a longer profile because you get credit for being in shallower water during the dive. It will also manage your logged information and give you up-to-the-minute repetitive dive times to the depth you want to go to. Many of them will also download to a PC for graphic display of the profile through the entire dive.

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#7078 - 01/08/06 12:36 AM Re: Defective Dive Tables
scubashep Offline
veteran

Registered: 08/15/05
Posts: 67
I know a website that has full navy dive tables and manuals. It also has alot of other manuals for reg service and stuff. It might help you in your adventure I am not sure. I can post it if it's ok to do so here. Does anyone know how much poo you get in for posting sites with "not so public info"?

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#7079 - 01/08/06 04:22 PM Re: Defective Dive Tables
BrianO Offline
veteran

Registered: 05/04/01
Posts: 289
Loc: Irvine
The content of any link would determine weather or not it remained on these posts.
The original issue posted here was that there are differences in the various available tables. For training purposes, It is recommended to use the tables put forth by the training agency whose course you're currently enrolled in. Otherwise, a computer that is formatted for the type of diving activities you intend to engage in will serve you well.

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#7080 - 02/04/06 06:40 AM Re: Defective Dive Tables
MuckDiver Offline
new diver

Registered: 02/04/06
Posts: 3
Loc: Minnesota
Just to correct something:

The SSI tables are not straight-up navy tables, they're based on Doppler studies, and thus considered "more conservative" than the navy tables.

There are a number of versions of the tables out there, all of them are at best approximations, and just because a dive profile puts you one column over in remaining nitrogen time, doesn't mean much at all. Your instructor should know that! I wouldn't worry about it -- if you look into it, the difference will only be a few minutes either way.

Another way to look at it is compare it to using a computer: there are different algorithms used among computers, just like there are different tables. If you and your buddy have different computers, and they indicate a slightly different RNT, does that mean one is defective?

Finally, unless you are descending vertically to a fixed depth that happens to be on the chart, staying there, and then ascending straight up, the chart has a built-in "penalty", and will be more conservative than a computer. That's the main reason I like using a computer -- no silly penalties for normal multi-level diving.

If you are really worried about it, as you should be for instance, if you have some condition that pre-disposes you to DCI, then I recommend buying a computer that allows you to program in an extra safety margin, and use it. The Suunto computers, for instance, use an algorithm based on "micro bubble" research that gets imncreasingly more conservative for multiple repetetive dives on the same day, and you can program them to provide an increased level of conservatism.

To me the most worrisome thing about the experience you describe is the reaction of your instructor -- obviously not very knowledgeable about scuba.

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#7081 - 02/04/06 04:26 PM Re: Defective Dive Tables
BrianO Offline
veteran

Registered: 05/04/01
Posts: 289
Loc: Irvine
Again, very insightful. The recurring theme throughout these replies is that all of the tables are based on "safe theory" that has been in place for years. The overall result as MuckDiver points out is that it's a few minutes one way or the other. New algorithms and numbers of "tissue types" (simply an estimated rate of absorbtion/off-gassing at a given depth) are being developed and tested. Varying rates of ascent and air integration have also been used to determine a closer look at the gasses absorbed on a particular dive profile. As technology moves forward, we will see even more ways of monitoring the gasses absorbed on a dive.

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#7082 - 12/24/08 08:15 AM Re: Defective Dive Tables [Re: BrianO]
rquasar Offline
avid diver

Registered: 12/24/08
Posts: 16
Loc: AZ
I know this thread is old, but I was wondering. I got my cert this year, & I use a Dive Computer with transmitter, I don't even carry the dive table with me, since the computer calculates everything even for the 2nd,3rd or 4th dive. I also use a backup Computer. Is there a reason why I should bother with the dive table?

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#19250 - 01/15/12 02:58 PM Re: Defective Dive Tables [Re: rquasar]
Chikarma Offline
new diver

Registered: 01/15/12
Posts: 2
I still use the PADI Dive tables but totally agree that you need to have a good standard of tuition to enable you to understand the tables and work with them properly. At the end of the day it is still the individual diver and their interpretation of the PADI Dive Tables. Make sure you have proper training prior to using the tables so you really know what you are doing. For those that are at a proficient standard and use the tables regularly i found a good copy of the PADI Dive tables at this blog: http://divingholidaysmalta.blogspot.com/

They also have some interesting articles on NAUI and comparisons with the PADI dive Tables if you are interested.

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