Steve-

Here's some Decom generated tables which when scrutinized should provide 
your answers:

Here's an air dive using no accelerated deco:

Depth Time   DT   TT  O2/HE/N2 PpO2  CNS% TCNS%  GAS     BRate
  130   40   40   40  21/ 0/79 1.04  14.5  14.5  138 cf  0.70
   40    2   45   45  21/ 0/79 0.46   0.0   0.0    3 cf  0.70
   30    6   51   51  21/ 0/79 0.40   0.0   0.0    8 cf  0.70
   20   13   64   64  21/ 0/79 0.34   0.0   0.0   15 cf  0.70
   10   22   86   86  21/ 0/79 0.27   0.0   0.0   20 cf  0.70 
OTU'S =    0
CNS % =  14.5
TOTAL DECO TIME:  43 
Ascent Time :   3
TOTAL GAS USED :    184 cubic feet
 21/ 0/ 79      184 cf

--------------------------------------------
And here's the dive using 20/20

Depth Time   DT   TT  O2/HE/N2 PpO2  CNS% TCNS%  GAS     BRate
  130   40   40   40  20/20/60 0.99  13.0  13.0  138 cf  0.70
   40    3   46   46  20/20/60 0.44   0.0   0.0    5 cf  0.70
   30    6   52   52  20/20/60 0.38   0.0   0.0    8 cf  0.70
   20   15   67   67  20/20/60 0.32   0.0   0.0   17 cf  0.70
   10   26   93   93  20/20/60 0.26   0.0   0.0   24 cf  0.70 
OTU'S =    0
CNS % =  13.0
TOTAL DECO TIME:  50 
Ascent Time :   3
TOTAL GAS USED :    192 cubic feet
 20/ 20/ 60      192 cf

-------------------------------------------------------
-------------------------------------------------------

Now here are the same dives using accelerated deco-

Depth Time   DT   TT  O2/HE/N2 PpO2  CNS% TCNS%  GAS     BRate
  130   40   40   40  21/ 0/79 1.04  14.5  14.5  138 cf  0.70
   40    2   45   45  50/ 0/50 1.11   0.8  15.3    3 cf  0.70
   30    4   49   49  50/ 0/50 0.95   1.2  16.5    5 cf  0.70
   20    6   55   55 100/ 0/ 0 1.61  14.3  30.9    7 cf  0.70*
   10    9   64   64 100/ 0/ 0 1.30   5.0  35.9    8 cf  0.70 
OTU'S =   31
CNS % =  35.9
TOTAL DECO TIME:  21 
Ascent Time :   3
* DIVE HAS EXCEEDED 1.5 PpO2...
TOTAL GAS USED :    161 cubic feet
 21/ 0/ 79      138 cf
 50/ 0/ 50        8 cf
 100/ 0/ 0       15 cf

And the 20/20:

Depth Time   DT   TT  O2/HE/N2 PpO2  CNS% TCNS%  GAS     BRate
  130   40   40   40  20/20/60 0.99  13.0  13.0  138 cf  0.70
   40    2   45   45  50/ 0/50 1.11   0.8  13.9    3 cf  0.70
   30    4   49   49  50/ 0/50 0.95   1.2  15.1    5 cf  0.70
   20    7   56   56 100/ 0/ 0 1.61  16.7  31.8    8 cf  0.70*
   10   10   66   66 100/ 0/ 0 1.30   5.6  37.4    9 cf  0.70 
OTU'S =   34
CNS % =  37.4
TOTAL DECO TIME:  23 
Ascent Time :   3
* DIVE HAS EXCEEDED 1.5 PpO2...
TOTAL GAS USED :    163 cubic feet
 20/ 20/ 60      138 cf
 50/ 0/ 50        8 cf
 100/ 0/ 0       17 cf
-----------------------------

As you can see when using accelerated deco you can treat 20/20 like air. 
And you can also see that when diving the deeper depths for any time at 
all accelerated deco is the way to go as well, unless you like hanging 
there for an hour...

 Jim

Sender: Steve Lindblom  Date: 9/28/98 10:57 AM

>If one were going to use trimix in the deep rec/lite tec range,  as many
>have been advocating here, for moderate exposures, ,  say, 100-160', 20-40
>minute bottom, and wanted to have a fairly standard mix to use rather than
>doing a different mix for every dive, what would one use?
>
>- 17/17 poor man's trimix aka heliair
>- Cobb's 20/20
>- a nitrox-style hyperoxic trimix, say, 28/30 or thereabouts
>- a real trimix, say 17/30
>- other ??
>
>How would one plan the dive:
>- available tables (which?)
>- Cobb's 20/20 tables (which don't exist yet?)
>- custom computer-generated tables for each dive
>- air/nitrox tables or computers, and ignore the He.
>- other?
>
>I have no opinion or agenda here, just curious about how ready trimix is
>for use by the non-hardcore-techie.
>
>
>
>--
>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
>Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
>


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