Sean

>Should you even use the 10' stop?  Errols had told me in an e-mail a long
>time ago to not even use the 10'...since you aren't keeping the PO2 at 1.6
>it wasn't worth it.  I have cut them out since then, and set 20 as the last
>stop depth in ZPlan...

Cutting tables with 20' and 10' stops enabled and decoing on O2 will generate
a total time on O2 about the same as setting 20' as the last stop.  E.g. a
minute or so difference which is neither here not there.

So, it doesn't really matter whether you cut tables with or without the 10'
stop, what matters is where you do the stops.  I do all my O2 stops at 20'.
This means that if I cut tables with 20' and 10' stops, I do the 20' at 20'
and the 10' at 20', thereby keeping the PO2 at 1.6.  This is done in the
belief that the higher PO2 provides a better deco than Buhlmann algorithms
would indicate.

What I understand George to be saying is something else.  Which by of a
simple example is:

If the software gives O2 stops as follows:

20': 6 Minutes
10': 12 minutes

You can reverse the 10' and 20', to do 12 minutes at 20', and then start your
ascent from 20' to the surface taking 6 minutes to get there.  Correct?

This makes sense to a non expert like me, as by spending more time at 20'
i.e. 12 minutes we have moved the ceiling higher than 10' which would have
been the next stop.  And then start a slow progressive ascent - don't forget
stops are a way of achieving this at a higher level of granularity. It is
probable that the slow "early" ascent from 20' is better since the last part
of the ascent is where the greatest pressure change occurs and the greatest
likelihood for bubbles to cause a problem (assuming deep stops have been
done).  You are providing a better opportunity for your lungs to filter out
the bubbles since they are arriving at a slower rate.  The only downside is
the reducing PO2 during the slow ascent.

It also makes the deco a bit more interesting with something to concentrate
during the slow ascent!

David Shimell
Email: shimell@se*.co* <mailto:shimell@se*.co*> 
Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited,
Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF, UK
registered in England and Wales under company number: 1999363, registered
office as above

-----Original Message-----
From:	Sean M. Cary [SMTP:smcary@mi*.co*]
Sent:	Thursday, December 16, 1999 11:48 PM
To:	kirvine@sa*.ne*; Gliviak, Jozef
Cc:	'Shimell, David (shimell)'; techdiver@aquanaut.com
Subject:	Re: Bottom timer - any recomendations

Should you even use the 10' stop?  Errols had told me in an e-mail a long
time ago to not even use the 10'...since you aren't keeping the PO2 at 1.6
it wasn't worth it.  I have cut them out since then, and set 20 as the last
stop depth in ZPlan...

Sean


----- Original Message -----
From: <kirvine@sa*.ne*>
To: Gliviak, Jozef <Jozef.Gliviak@co*.co*>
Cc: 'Shimell, David (shimell)' <shimell@se*.co*>;
<techdiver@aquanaut.com>
Sent: Thursday, December 16, 1999 3:46 PM
Subject: Re: Bottom timer - any recomendations


> I think David already said this, but the steps are not that precise.
> Some of our guys use an Ironman watch countdown timer that they set for
> each step, but we are talking very long steps. I carry one of them just
> so I do not inadvertanly blow off a 100 minute chunk of deco. I do not
> set the timer, I just note the time of day.
>
> BTW, Smithers Z Plan reruns the whole deco after separately figuring the
> deep stops and the normal run. I run them separately. This is what is
> giving you guys the bloated 10 foot stop. I think you can reverse the
> ten and twenty foot times and treat the ten as an ascent to the surface
> from 20 evenly in that amount of time. I can say that, but Will will
> not.
>
> Gliviak, Jozef wrote:
> >
> > Try Z-plan with WKPP deco stops. They are in seconds.
> > Or if you would like to know (control) your ascent rate in open water,
It's
> > helpfull to have seconds.
> >
> > The best I can imagine would have a second timer which you can easily
reset.
> > I never heard about such device.
> >
> > Regards
> >
> > Jozef Gliviak
> > Slovakia
> >
> > -----Original Message-----
> > From: Shimell, David (shimell) [mailto:shimell@se*.co*]
> > Sent: Thursday, December 16, 1999 4:54 PM
> > To: Gliviak, Jozef
> > Subject: RE: Bottom timer - any recomendations
> >
> > Jozef
> >
> > Why are you concerned about reading to the second?
> >
> > David Shimell
> > Email: shimell@se*.co* <mailto:shimell@se*.co*>
> > Project Manager, IBM NUMA-Q, Sequent Computer Systems Limited,
> > Weybridge Business Park, Addlestone Road, Weybridge, Surrey, KT15 2UF,
UK
> > registered in England and Wales under company number: 1999363,
registered
> > office as above
> >
> > --
> > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
>
> --
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