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From: <bdi@wh*.ne*>
Date: Thu, 13 Jan 2000 12:06:19 +1100
To: "Manos Manoli" <manos@ma*.co*.cy*>, Tech Diver <techdiver@aquanaut.com>
Subject: Re: I think I don't understand
At 12:22  13/01/00 , Manos Manoli wrote:
>Hello Billyw
>Hmmm it gets tricky.... If you are also using nitrox as a bottom mix
>then you don't want to accelerate  your OTU's very fast  just when
>you have started your deco stops.

Why not?

If you plan your mixes so you don't push the OTU
limits, opening the oxygen window earlier is a benefit,
not a problem. You just need to avoid hot mixes.

>  I believe air breaks can be handled
>and calculated much better on your last stop.
>AND NOT ONLY THAT : lets follow the worst scenario lets say that you have
everything
>on control and on surface you have the symptoms 50% is next to nothing.

Your oxygen on the boat is 100%.

rgrds billyw


>My humble opinion.
>Rgds Manos Manoli
>Cyprus - Limassol
>
>
>bdi@wh*.ne* wrote:
>
> > At 08:08  12/01/00 , Manos Manoli wrote:
> > >Jeff i made many many tests with diferent Ean mixtures belive me
> > >100% oxygen on 6 meters does a hell of a lot diference than 50% on all
stops.
> > >Plus you can stick with it on board if you screw up thinks.
> > >To be precise i tested 40% on all deco stops and create an excel table
someware
> > >ill try to find it for you but from my personal experience is that nothing
> > >compares
> > >to pure oxygen.
> >
> > Manos, on these 'lite' technical dives, you can
> > get onto the 50 earlier to open the oxygen window.
> >
> > With deep stops & 50, you've done more of your deco
> > earlier, rather than leaving it all for the 02 to
> > flush-out the bubbles at 6 metres.
> >
> > rgrds  billyw
> >
> > >Jeffrey Swann wrote:
> > >
> > > > Dear  List,
> > > > George
> > > > Are you saying, that you get into deco time with a single tank.
> > > > This seems to throw away your teachings.
> > > > I mean, frankly where does recreational and tech diving separate.
> > > > I do alot of nitrox type diving.
> > > > That is 20 to 30 m wrecks, multilevel, etc.
> > > > I use a harness routinely now and practice redundancy.
> > > > This brings me to the point:
> > > > What is wrong with carrying  a pony with a single.
> > > > I sling it across my waist, clipped up tight.
> > > > Reg clipped off, on the harness.
> > > > Back gas EAN 36.
> > > > Pony 25 cu ft EAN 50. (or similar)
> > > > Also, if you do a 25 to 30m dive, George are you just using nitrox, or
are
> > > > you putting some He in that as well.
> > > > The dive boats we are using for harbour dives, don't lend themselves to
> > > > using twins.
> > > > Excepting if I use my twin 55's.
> > > > Sorry if I am ranting.
> > > > Anybodys comments welcomed!!!
> > > > Jeff of Darwin.
> > > >
> > > > At 20:09 10/01/00 -0500, you wrote:
> > > > >Art, I was kind of thinking that the worse shape you are in , the
better
> > > > >that trick would work on a relative basis: the guy who sits on the
> > > > >backgas and extends the stops will ongas more stuff than he loses(
> > > > >although in different places) - his only real chance is to force the
gas
> > > > >out and treat himself with the oxygen.
> > > > >
> > > > >For the fit diver, helium especially is a great gas even when the ppo2
> > > > >is low. Bill Me and I deco out on backgas a lot and don't get hit on
> > > > >relativlely deep dives with short bottom times. I hate to admit this,
> > > > >but we do a lot of these on single 80's with no deco gas at all. Now
> > > > >that should get the weenies howling, but see Weinke's stuff - his work
> > > > >says it is very doable.
> > > > >
> > > > >
> > > > >Paltz, Art wrote:
> > > > >>
> > > > >> I've been following this thread with good interest.  Are we saying
that on
> > > > >> this particular profile that had we lost the 50/50 mix that we should
> > > > >> probably just follow the planned 50/50 stops but use back gas?  Then
do our
> > > > >> planned 100% stops as scheduled?  I think this probably works if you
could
> > > > >> just come up to 20 foot anyway.  Knowing that most people are not in
the
> > > > >> same shape as George, the question is for the normal diver in
relatively
> > > > >> good shape who has done similar dives without having to resort to
in-water
> > > > >> contingency planning (i.e. has not lost a gas) and has had no
trouble,
> > > > >> should they just follow the planned schedule substituting back gas
for
> > > > >> 50/50?  Sorry so long but that's just the way it came out.
> > > > >>
> > > > >> I think to summarize and simplify, if in descent shape and
experienced in
> > > > >> these types of dives and you loose the deeper gas should you:
> > > > >> a). Substitute lost gas with previous gas (possibly back gas) and
continue
> > > > >> with planned schedule.
> > > > >> b). Do to previous gas (back gas in this instance) and try and fudge
a
> > > > >> little by adding stops (probably dangerous on deep stops)
> > > > >> c). Panic and surface, signal for correct gas and try and go down
and hold
> > > > >> your nuts hoping someone comes to the rescue.
> > > > >> d). Something else?
> > > > >>
> > > > >> The above assumes that "previous gas" is probably better than just
saying
> > > > >> bottom mix.  Correct me if I'm wrong but I would assume that if you
were
> > > > >> using say 35% Nitrox, 50/50 and O2 in the schedule you should use the
> > > > >> remaining 35% for the 50/50 stops if you lost the 50/50 gas.  Maybe
on a
> > > > >> profile where you're necessitating more than 2 deco gases the answer
> > > > >> changes.
> > > > >>
> > > > >> Thanks,
> > > > >> Art.
> > > > >>
> > > > >>         -----Original Message-----
> > > > >>         From:   kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*]
> > > > >>         Sent:   Monday, January 10, 2000 10:14 AM
> > > > >>         To:     Shimell, David (shimell)
> > > > >>         Cc:     Ian PINKSTONE; techdiver@aquanaut.com
> > > > >>         Subject:        Re: I think I understand
> > > > >>
> > > > >>         Move up = shallower. You can do the 50% as if it were oxygen
> > > > >> timewise,
> > > > >>         and if you lose that you can do the backgas as if it were 50%
> > > > and go
> > > > >> to
> > > > >>         the oxygen. What I am saying is do not extend the table
because you
> > > > >> have
> > > > >>         the wrong gas - the upper deco steps can be screwed with
> > > > >> unmercifully
> > > > >>         without any real consiequnces, it is the deep ones that you
must so
> > > > >>         corectly.
> > > > >>
> > > > >>         I'll let you in on a little secret - you could do this dive
and
> > > > come
> > > > >>         right to 20 in quick steps  , do 20 minues on oxygen and get
out
> > > > >> clean -
> > > > >>         done it, and done al ot worse and gotten away with it. These
are
> > > > the
> > > > >>         real measures you take in an emergency.
> > > > >>
> > > > >>         Shimell, David (shimell) wrote:
> > > > >>         >
> > > > >>         > George
> > > > >>         >
> > > > >>         > Most interesting stuff...
> > > > >>         >
> > > > >>         > >In real life, you are btter off moving up and taking the
> > > > gradient
> > > > >>         > >offgassing as bubbles while still underwater than you are
> > > > sucking
> > > > >> on the
> > > > >>         > >wrong gas and lengthening the stops,
> > > > >>         >
> > > > >>         > Going pack to your suggested deco profile:
> > > > >>         >
> > > > >>         > Profile 220' FOR 25
> > > > >>         > 16/50, 50% and O2
> > > > >>         >
> > > > >>         > DEPTH   TIME    GAS
> > > > >>         > 160-120 1 MINUTE EACH ON BG
> > > > >>         > 110     1
> > > > >>         > 100     1
> > > > >>         > 090     1
> > > > >>         > 080     1
> > > > >>         > 070     5       50/50
> > > > >>         > 060     2
> > > > >>         > 050     3
> > > > >>         > 040     5
> > > > >>         > 030     8
> > > > >>         > 020     13      OXYGEN
> > > > >>         > 20-0    8
> > > > >>         >
> > > > >>         > I would like to better understand what you mean by "moving
up".
> > > > >>         >
> > > > >>         > Following a failure of the 50%, are you suggesting that you
> > > > >> continue the deco
> > > > >>         > as if 50% had been available i.e. follow the schedule but
on BG.
> > > > >>         >
> > > > >>         > Or are you saying that 16% is so worthless that you would
skip
> > > > the
> > > > >> stops and
> > > > >>         > go straight to O2 at 20', if so what kind of ascent would
you do
> > > > >> from 70' to
> > > > >>         > 20' to give your system a chance to cope with the bubbles?
> > > > >>         >
> > > > >>         > 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:   kirvine@sa*.ne* [SMTP:kirvine@sa*.ne*]
> > > > >>         > Sent:   Thursday, January 06, 2000 4:48 PM
> > > > >>         > To:     Ian PINKSTONE
> > > > >>         > Cc:     techdiver@aquanaut.com
> > > > >>         > Subject:        Re: I think I understand
> > > > >>         >
> > > > >>         > Ian, these decos are so severely overstated that a loss of
a gas
> > > > >> is
> > > > >>         > insignificant. I did a whole Wakulla deco on my 190 bottle
right
> > > > >> through
> > > > >>         > 20 feet on a 30 minute bt at 300 and never got hit, using a
> > > > >> schedule for
> > > > >>         > switching. I kept screwing up the gas switch and not
knowing
> > > > it. I
> > > > >> only
> > > > >>         > found out when I got to 20 feet and my O2 was not there,
and I
> > > > >> then saw
> > > > >>         > that my 120 and 70 bottle were both untouched, and that I
was
> > > > >> about out
> > > > >>         > of gas on my 190 bottle. So much for deco.
> > > > >>         >
> > > > >>         > In real life, you are btter off moving up and taking the
gradient
> > > > >>         > offgassing as bubbles while still underwater than you are
sucking
> > > > >> on the
> > > > >>         > wrong gas and lengthening the stops, and in real life if
you have
> > > > >>         > anything approaching the deocompression time that you are
> > > > >> suggesting
> > > > >>         > here, you not only have support with extra gases
available, you
> > > > >> have
> > > > >>         > buddies to share with. I just did a dive wher I shared the
70
> > > > >> bottle
> > > > >>         > with my dive partner last Sunday, and it worked fine.
> > > > >>         >
> > > > >>         > --
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> > > > >> `techdiver@aquanaut.com'.
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> > > > >>
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