Well, unless he's using over 100% 02, then ANY stop at 10' would be a waste.
I think Bill Stone was able to get more then 100% in a tank, but it requied
so much cake eating , that no mere ahh mortal could redo the fill!

Sean


-----Original Message-----
From: Shimell, David (shimell) <shimell@se*.co*>
To: Sean M. Cary <SMCARY@MI*.CO*>; Steve Hogan <Steve.Hogan@tr*.co*>
Cc: techdiver@aquanaut.com <techdiver@aquanaut.com>
Date: Thursday, June 10, 1999 7:05 AM
Subject: RE: Re Last Stop Depth


>Sean
>
>Weird, I would have thought everyone did their O2 stops at 6m/20'.
However,
>I don't think Steve actually mentioned which gasses he was using for this
>"real mix" dive.  Hopefully he was using the "proper" ones so your point
>would be valid.
>
>David Shimell
>Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa.
>Email: shimell@se*.co* <mailto:shimell@se*.co*>
>
>-----Original Message-----
>From: Sean M. Cary [SMTP:SMCARY@MI*.CO*]
>Sent: Wednesday, June 09, 1999 11:16 PM
>To: Steve Hogan; shimell@se*.co*
>Cc: techdiver@aquanaut.com
>Subject: Re: Re Last Stop Depth
>
>Why do a 10' stop when the PO2  of 100% is lower then 1.6?  I make my last
>stop 20fsw.
>
>Sean
>
>
>-----Original Message-----
>From: Steve Hogan <Steve.Hogan@tr*.co*>
>To: shimell@se*.co* <shimell@se*.co*>
>Cc: techdiver@aquanaut.com <techdiver@aquanaut.com>
>Date: Wednesday, June 09, 1999 4:40 PM
>Subject: RE: Re Last Stop Depth
>
>
>>David,
>>
>>
>>>Occasionally, I do a multi-level, bimble-around-the-place dive and dive
an
>>>air computer but deco on O2.  I'm comfortable to leave the computer on
the
>>>line or bend it when I've done sufficient deco.  Note: this is based on
>>rules
>>>of thumb which allow me to do sufficient deco.
>>
>>I have done many dives using mix (usually 18/40) with 50/50 deco gas
>>and an air computer. Like you I am just wandering around and I use the
>>air computer as a guide for the deco. I have found that the air only
>>schedule
>>is longer than a mix schedule with deep stops and deco gas. There are a
few
>>rules
>>though. 1. Do the deep stops.  2. Use the deco gas (50/50) for all depths
>>shallower
>>than 70 ft. 3. perform the dive like a multilevel dive (no sawtooth stuff)
>>This is only for some dives where a set of tables is not really
>>necessary (like wnadering around on a reef where the bottom is known but
is
>>highly variable)
>>
>>Do not misunderstand me, when on a real mix dive (when I expect that the
>>stops will be greater than 10-20 ft) then the dive is planned and executed
>>on
>>tables (and I bend my poor computer....backup depth gauge/timer. On a dive
>>I did Sunday the computer informed me that I needed to stay at 20 ft while
>>on my 10 ft (table) stop and will finally clear 60 hrs after getting out
of
>>the water.... I am glad it is not adaptive...<grin> It still indicated 37
>>min
>>of deco left when I got out of the water)
>>
>>Steve
>>
>>
>>
>>David Shimell
>>Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa.
>>Email: shimell@se*.co* <mailto:shimell@se*.co*>
>>
>>-----Original Message-----
>>From: David Reinhard [SMTP:reinhard@oc*.co*.au*]
>>Sent: Wednesday, June 09, 1999 5:51 AM
>>To: techdiver@aquanaut.com
>>Subject: Re Last Stop Depth
>>
>>Thanks to all who have contributed to my knowledge with your replies.
>>Unfortunately there are too many replies for me to respond personally to
>>all of you
>> A number of you have pointed out that air is a poor choice for
>>decompression. I fully agree, and it is not my practice to do so. It was
>>remiss of me not to point that out in my original post. Below is my reply
>>to David Shimell which I had intended to go to the list but I think may
>>have only gone to his personal email address.
>>
>>At 01:19 07-06-99 -0700, you wrote:
>>>David
>>>
>>>The reason there is a significant difference between a last stop at 6 vs.
>3
>>>is that you are doing the deco on air which is a poor choice.
>>
>>In reality I don't do my deco on air. I was just running hypothetical
>>profiles to see the effect of different stop depths. While I naturally
>>expected a difference it was the magnitude of the difference that
surprised
>>me. While the pressure difference between 3m and 6m is not insignificant I
>>was particularly surprised that 1m could make such a big difference.
>> You are quite right, of course. Deco should be done on an
>>appropriate
>>nitrox mix and/or pure o2. But being very cautious I still deco to the air
>>schedule and take the safety benefit rather than do accelerated deco. So
by
>>choosing 6m rather than 3m I have been spending a lot of extra time in the
>>water. However due to the large ocean swells we often encounter where we
>>are diving it may at times still be appropriate to go for the 6m stop.
>>
>>Thanks for your comments,     Dave.
>>
>> I also received the following comment which I am particularly interested
>>in:-
>>
>>(quote)
>>"If you have done sufficient deco, then spending further time in the water
>>is
>>increasing your risk.  OK, this risk is small but never-the-less a risk
and
>>it bites some people.  Doing excessive deco is therefore not adding
>safety."
>>
>>Do others concur with this idea? As I said above I deco on nitrox but
>>operate on an air schedule. In effect this would constitute "excessive
>>deco" for the gas I am using. So is there a problem with this practice?
>>Does doing extra deco increase or decrease your risk? If you are going to
>>increase your deco at what point should you do it, eg only on the last
>>stop? Come to think of it Pyle stops are in effect increased deco beyond
>>that required by the tables. One of the thoughts I have had about this is
>>what actually constitutes "excess" deco. Given the variability in deco
>>tables what constitutes the "right amount" of deco on one table could
>>constitute "too much" deco on another table. Given that we don't really
>>know what the "right amount" of deco actually is for any particular
>>individual on a particular dive profile how can we hope to know what is
>>"too much" deco. (The only definition of "right amount" of deco I can
think
>>of is that amount which leaves you unbent after a dive - but you don't
>>really know that until after the dive, since tables are merely a hopeful
>>guideline which fortunately are right most of the time).
>>
>> In reality I would be very surprised if a small variation in stop
>>depth
>>made a large practical difference to the decompressing diver. If this were
>>the case I am sure we would have a lot more bent divers (hmmm... on the
>>other hand we do have a number of divers that get bent while apparently
>>following the tables... I wonder...).  As has been pointed out the use of
>>nitrox/o2 for deco significantly reduces the differences I observed, so it
>>is even less of a problem to deco diving than it would initially seem.
>>
>> It has also been mentioned that Zplan adjusts all stop depths if you
>>change the last stop depth. I had noticed this and have found it
>>inconvenient compared to other software that keeps the same standard stop
>>depths and only adjusts the last stop. I guess I didn't consider the
>>possible effect of this change on the total deco time. I noticed another
>>post on this list about a new shareware deco program that does not do
this,
>>so I would be interested in having a look at that program when it is
>>available.
>>
>>
>>Thanks to all, regards,  Dave.
>>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>>Ocean Internet - "The Quality ISP"
>>http://www.ocean.com.au/info.html
>>
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