Deco Table comparison...

[all4scuba05]

If this is not the best place for this question, feel free to move it.

I'm looking at TDI's Navy Table(Deco Side) and Bulmann Deco Table.

First example:
Dive to 18.2M (60')
80 Min's BT
TDI Do a 7 min stop @ 3M(10')
Bulmann 18 min @ 3M(10')
Notice the difference in Deco Requirement

Second example:
TDI Dive to 190'(57.9M)
15 min's BT
Do 4 min's @6M(20')
Do 7 min's @3M(10')
Bulmann Dive to 57M(Just under 190')
15 min's BT
Do 1 min @12M
4 min @9M
5min @6M
11min @3M
In the second example TDI has you in water approx 17 minutes
Bulmann is approx 41 minutes.

Wow, what a difference. For those that would dive using Tables and not software... What table do you use? If not one of these two, then which one, and where does it fall as far as conservative or liberal? It would be nice to be able to dive TDI's times and not get a hit.

[Meng_Tze]

..
Wow, what a difference. For those that would dive using Tables and not software... What table do you use? If not one of these two, then which one, and where does it fall as far as conservative or liberal?
I assume you are comparing both tables with the same gas. Yes there will be a difference between USN and Buhlman tables. It is inherent to the basics and models.

I dive VPM predominantly now, but did many dives with Buhlman GF. Both work fine for me. Depending on the dive and conditions (environment and myself/buddy) conservatism is adjusted. We do use software to cut tables and have free reign in setting up a dive rather than fixed preprinted tables.


It would be nice to be able to dive TDI's times and not get a hit.

Start slowly with lots of padding and work from there. Depending on your training/experience, you can adjust which way you want.

[Mr Carcharodon]

Hmmm...the TDI deco time is about half of the Buhlmann. Is TDI assuming EAN-50 for deco?

[all4scuba05]

Start slowly with lots of padding and work from there. Depending on your training/experience, you can adjust which way you want.

Yes, that's what I am planning to be on the safe side.

I haven't seen a list yet of all the different charts in the order of conservative to liberal or vice versa. Is there one out there?

[all4scuba05]

Hmmm...the TDI deco time is about half of the Buhlmann. Is TDI assuming EAN-50 for deco?

Top of the chart says US Navy Air Tables. Perhaps they are the most liberal?

[all4scuba05]

I forgot to mention something important.
I am starting my Advanced Nitrox/Deco class on Tuesday. I don't plan on diving those tables 'til I'm certified.

[Meng_Tze]

Thank you for your honesty. You will learn a lot in that class and probably end up cutting your own tables....;)

[JS1scuba]

It appears you are comparing the USN tables (in TDI book) with Buhlmann Tables. The USN Tables are the absolute shortest tables around. They were designed for military application where a chamber is usually on-site. However, they are the most popular tables in the world and have an outstanding track record for working well.

Buhlmann tables are more conservative than USN and you will see more stops for a deco dive and shorter times for no-stop times.

Our company manufactures NAUTILUS DIVE PLANNER which has 5 different algorithms in it so you can compare different "tables" in a software planning mode. You can find that product at:

NAUTILUSDIVEPLANNER.COM (http://www.nautilusdiveplanner.com) you can also read a lot about models there as well.

IF you are taking an ADV EAN / DECO class this might be a product for you as well.

Regards,

[all4scuba05]

In that case, if I were to make a list of tables from most conservative to most liberal, which table would be in the middle?

[battles2a5]

The US Navy did not develop those tables for recreational divers. They were built for Navy divers that have support teams and an available recompression chamber. I would be willing to bet that the Navy's idea of an "acceptable" number of cases of DCS is different from ours. And they always have to option to throw a diver in the chamber is symptoms arise. The Buhlmann ZL-16 model is much more refined, more conservative and uses 16 compartments in the algorithm vs. 6 (i think) for the Navy. So they outcome is theoretically more "precise". FWIW, if I am using stock tables I will use Buhlmann. My computer uses the same algorithm so it makes things simpler. I use VPM-B for custom tables.

[hydro12]

Hopefully this is not interpreted as a hijack and I certainly hope it sheds some light on deco model comparison for the OP:

Joel,

In regards to your Nautilus deco software I was reading that the ZH-L16A algorithm was a purely mathematical model developed by Buhlmann and was replaced by ZH-L16B and C for the purposes of tables/software for application in real-world use because A was found not to be conservative enough, especially in the middle M-values (particularly causing skin bends, is what I read).

However, my observed use of the algorithm seems quite different. I have a friend who owns Nautilus and ran a profile of a dive to 140ft/20min on Air (no accelerated deco) w/ no GFs. He also computed a 2 hr SI and ran the exact same profile for the 2nd dive. The two profiles he came up with from the Buhlmann 16-compartment algorithm in Nautilus are:

Dive 1:
140fsw/20min
30fsw/8min
20fsw/5min
10fsw/15min

2 Hour SI

Dive 2:
140fsw/20min
30fsw/8min
20fsw/5min
10fsw/22min

When I ran the same profile through GAP, both with ZH-L16B and ZH-L16C (they don't have A in GAP) with no GFs (ok, 99/100% GFs), I got the following:

Dive 1:

140fsw/20min
30fsw/1min
30fsw/3min
10fsw/8min

2 hour SI

Dive 2:

140fsw/20min
30fsw/1min
20fsw/3min
10fsw/8min

As you can see, not only does ZH-L16A appear to produce a much more conservative set of stops than ZH-L16B or C (B & C both produced the same table), but A actually gives you a longer 10 ft stop, while B & C don't extend any of the stops (Dives 1 and 2 are identical) when using the algorithms from GAP.

Seeing as how this contradicts what I've read about the different versions of the Buhlmann algorithm, I was hoping you might be able to shed some light on the disparity between the profiles.

Thanks!



It appears you are comparing the USN tables (in TDI book) with Buhlmann Tables. The USN Tables are the absolute shortest tables around. They were designed for military application where a chamber is usually on-site. However, they are the most popular tables in the world and have an outstanding track record for working well.

Buhlmann tables are more conservative than USN and you will see more stops for a deco dive and shorter times for no-stop times.

Our company manufactures NAUTILUS DIVE PLANNER which has 5 different algorithms in it so you can compare different "tables" in a software planning mode. You can find that product at:

NAUTILUSDIVEPLANNER.COM (http://www.nautilusdiveplanner.com) you can also read a lot about models there as well.

IF you are taking an ADV EAN / DECO class this might be a product for you as well.

Regards,