David, 

Mix specific tables have their place. And we do use them, but I have found
that using the variable mix table does not add all that much time to a deco
complared to what it saves in time from making tables all the time.  I also
like the variable mix tables form an operational perspective, especially in
the field.  The basis behind these types of tables is operational
simplicity -- keep the deco gases constant and the rest can be variable but
the schedule remains the same. It is also easier to keep a group all on the
same schedule.

The slightly longer deco is really not a big deal on bounce dives, I can
see it getting boring if one was in a cave doing a longer than 30 or 40
minute bottom time past 200 fsw, but for the ocean 5 or 10 minutes is not a
big deal. 





At 08:45 AM 10/2/1998 +0100, David Shimell (shimell) wrote:
>Joel
>
>Thanks for the information, most of which I was aware of.
>
>When I mentioned standard tables, I was referring to the idea of choosing a
>set of bottom gas mixes for specific depth ranges and then developing your
>own standard tables for these mixes and deco gases the individual uses.
>Thus, cut the tables once and they can be re-used.  The main problem with
>generic tables of the nature you mention is that you'll end up doing far too
>much deco than is necessary.
>
>David Shimell
>Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa.
>Email: shimell@se*.co* <mailto:shimell@se*.co*> 
>
>-----Original Message-----
>From:	Joel Silverstein [SMTP:joelsilverstein@wo*.at*.ne*]
>Sent:	Wednesday, September 30, 1998 4:44 PM
>To:	David Shimell (shimell); s_lindblom@co*.co*;
>techdiver@aquanaut.com
>Subject:	RE: Trimix question - Real Tables 
>
>David, 
>
>There are standard tables for standard mixes ---Hamilton Research Ltd has
>had standard trimix tables avaialble for years 
>
>they are the Key West Consortium Tables -17/50/33 
>
>Variable Oxygen Variable Helium tables for Trimix from 120 fsw - 250 fsw 
>
>The single set of tables allow for the use of 16-21% oxygen  17-50% helium
>content
>
>Required decompression gas is EAN36 and Pure Oxygen. 
>
>
>There is a variation of these tables for shallower water diving and single
>gas decompression 
>
>Key West Consortium 18/35/47   
>
>For depths of 130fsw - 230fsw 
>
>This single set of tables allow for the use of 18-21% oxygen 30-40% helium
>
>Required decompression gas is EAN 55-65     oxygen is optional
>
>These tables are exceltional, are used by many many divers, and are quite
>expensive, however they have an extremely reliable track record and
>eliminate the need for making up new tables every time you want to do a
>dive -- they also allow for mix variables which makes them wodnerful to use
>on expeditions. --- No batteries needed. 
>
>
>
>
>At 03:07 PM 9/29/1998 +0100, David Shimell (shimell) wrote:
>>All
>>
>>>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?
>>
>>As a slight digression, it is worth developing standard mixes and tables
>for
>>ranges of depths and times.  I dive mixes for every 10 m, i.e. I use 50,
>60,
>>70, 80 metre mixes together with the corresponding tables... My run times
>>are also in 5 minute increments (easy to remember)  - usually 3 options
>with
>>the middle run time being the planned run time.  This RT is usually set at
>>around 90 minutes due to the water temperature in the UK.
>>
>>My tables for my 80m mix (16/44) go in 5 metre increments i.e. 80, 75, 70,
>>65, 60, 55, 50.  Thus if we mix for an 80 metre dive and weather precludes
>>diving this wreck, and we have to do a 63m wreck, then I would simply dive
>>my 65 m tables for this gas.
>>
>>For multiple day diving, I see a penalty of around 4 minutes maximum.  I
>use
>>the same tables but add in a minute here and there (one minute 3 m deeper
>>than my first mandatory stop, 1 minute in the middle somewhere and 2
>minutes
>>on my last stop at 6 m.  This is in addition to 10 m/minute ascents and
>deep
>>stops added.
>>
>>My tables are laminated and therefore re-usable.
>>
>>David Shimell
>>Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa.
>>Email: shimell@se*.co* <mailto:shimell@se*.co*> 
>>
>>--
>>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
>>Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
>>
>Joel D. Silverstein
>Scuba Training + Travel Co.
>http://www.NitroxDiver.com
>--
>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
>Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
>
Joel D. Silverstein
Scuba Training + Travel Co.
http://www.NitroxDiver.com
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