Computer or Not

[TSandM]

60': (Same source)

USN - 60
RDP - 55
DCIEM - 50
Buehlmann - 51
NAUI RGBM - 55
Vytec - 52
Aladdin Pro - 50
Cochran - 68

The numbers seem to get more consistent as the depths increase, to a point, but there is still significant variation. This is one of the things that made me realize, very early on, how much the various models are NOT carved in stone, absolutely accurate limits.

 

[darkpup]

Also, I wonder how the Cochran Commander came up with 599 minutes?

Being a software engineer by trade, I bet it's a max limit rather than some decompression model. As if 600 minutes is the max, and the code looks for X < 600 based on the average ATA.

~ Jason

 

[rjack321]

That NAUI RGBM number (55) looks suspect to me. I was always under the impression that they just lopped 5 min off the Navy tables. I have one of their newer tables (1994) vs. a late '80s version and that's the across the board difference.

The fact that the numbers start to converge at 60 and below is somewhat predictable. Much more uncertainty at the shallow depths.

 

[headhunter]

Navy Tables (according to Lippman, Deeper into Diving) 30 feet - 405 minutes. Same source, Buehlmann 400 minutes. DCIEM 30' - 300 minutes. RDP - 360 minutes. NAUI RGBM - 150 minutes. Same source, computer limits: Vytec 204 minutes, Aladdin Pro 334, Cochran Commander 599 minutes.

It won't be tough to guess which option I voted for after reading this post.

I used U.S. Navy Tables until November of 2004 when I started to use the "min deco" method that GUE teaches. I figured it was time that I started using something a bit more conservative and find it less of a hassel using the Navy Tables.

I just pulled out my old "paper" copy of Navy Tables. Table 1-11 is titled "No Decompression" Limits and Repetitive Group Designation Table for "No Decompression" Dives. It shows (Rev. 1970) on each page that I have, so it may have been changed since then and this may amount to no more than a history lesson.

Here is what I see in this table:

Down to 30 feet the column labled is blank.

Then the 2 columns show the following;
Depth (feet) and No-decompression limits (min)
35 - 310
40 - 200
50 - 100
60 - 60
70 - 50
80 - 40
90 - 30
100 - 25
110 - 20
120 - 15
130 - 10
140 - 10
150 - 5
160 - 5
170 - 5
180 - 5
190 - 5

It also shows an ascent rate of 60 feet per minute in the paragraphs that follow.

I'll say this again in case anyone reads this and wants to run out and use this.

These tables were last revised in 1970 and a lot of research has been done since then. Don't use this historical data in your actual diving.

Christian

 

[*Floater*]

130' - 5 min
120' - 10 min
110' - 15 min
100' - 20 min
90' - 25 min
80' - 30 min
70' - 35 min
60' - 50 min
50' - 60 min
40' - 170 min*

*I prefer to use 90 min here - then when you shift the times down by two rows you get a pretty good table for EAN32.

A good exercise for the skeptics out there is to calculate your average EAD's for your your last X rec dives (from your uploaded dive data), and see whether they are within the limits of this table.

 

[rjack321]

*I prefer to use 90 min here - then when you shift the times down by two rows you get a pretty good table for EAN32.

Or treat 40' as indefinate on 32%.

I only shift times one depth for 32% when above 80', I use a two depth shift below 80'

 

[*Floater*]

Or treat 40' as indefinate on 32%.

I only shift times one depth for 32% when above 80', I use a two depth shift below 80'

I treat 40' and 50' as indefinite on 32% because my dives so far have never lasted long enough (2.5+ hours) for it to really matter. So one EAN32 table looks like:
........? table.......PADI EAN32
130' - 15 min........18 min
120' - 20 min........20 min
110' - 25 min........25 min
100' - 30 min........30 min
90' - 35 min..........35 min
80' - 50 min..........45 min
70' - 60 min..........60 min
60' - 90 min..........90 min
50' - undef...........155 min
40' - undef...........undef

I included the PADI values for comparison - it's pretty close.

 

[rjack321]

Of course the padi table advocates a max depth of 110' on 32%, while the ?? table would set a MOD for 32% of 100' based on narcosis.

70ft = 60 minutes and 60 ft =90 minutes is too long for me. 20% of 60ft is only 12ft and I haven't been comfortable rounding that up to 20ft.

So I shift:
70ft = 50 mins
60ft = 60 mins

This 60' depth is a significant difference for your plan.
Have you actually done 90 minutes at 60' with 1 min stops at 30,20,10? How did it go?

 

[Lake Mead Tony]

After diving without a computer for 35 years, I finnaly got my first one about 2 years ago. It has to be the best investment I have ever made in diving equipment, nothing special but EAN is a must.

 

[*Floater*]

Have you actually done 90 minutes at 60' with 1 min stops at 30,20,10? How did it go?

No, but that's what my DIR-F instructor suggested (or he suggested the 90 minute value for 40' on the air table, and by implication 90 min at 60 for EAN32, but my dives generally don't last that long anyway), and I may tweek the values based on how I feel as I gain more experience with them.

In reality my dives so far have been lead by DM's who have used their computers to limit the bottom time when necessary and I just track the average depth and use the table to see if I need to do extra time on the ascent. For example, if a DM were to push X min past my average depth limits on that table, then I'd divide X min as additional time to my shallow stops (as a rule of thumb) where X is something small (10 minutes max). Beyond that I'd call the dive myself.