It may help me to answer that by knowing in what way you say that 1 in 8
students that you see can't use 100% at 20'? Is it that they can't maintain
a steady depth at 20' and therefore use 80% at 1.28 to avoid problems with
oxtox? Maybe they need more help to maintain bouyancy and a steady depth?
Let me know their problem and maybe I can answer.

Trouble is that they miss the benefit of the 1.6 gradient, even if they pull
their 80% stop at 30' on 1.52. In any event that has got little to do with
the point that I was making about needing backgas breaks on either 100% or
80% if you are doing that sort of deco.

Steve Bliim

-----Original Message-----
From: gzambeck1 [mailto:gzambeck1@me*.ne*]
Sent: Wednesday, 6 September 2000 21:03
To: Steven Bliim
Subject: Re: 80/20 deco


Then Steve why don't you explain to me why 1 out of 8 students I see can't
use
100% O2 at 20 ft.
They have to use 80/20.
There are a couple of diver I know who use 50% and still can't use 100% at
20
feet.

Greg Zambeck

Steven Bliim wrote:

> Jim has hit one of the nails on the head here. Anyone doing their deco on
> 80/20 from 30 feet as opposed to 100% from 20 feet is still going to be
> facing a similar PPO2 for similar times. They are going to need backgas
> breaks in the same way that those using 100% will need backgas breaks -
that
> is if their deco goes for long enough to need backgas breaks. So much for
> that argument!
>
> Have I got it wrong, can anyone tell me why the 80/20 crowd will not need
> backgas breaks?
>
> Regards
> Steve Bliim
> Still waiting for my trip to the NE!
>
> -----Original Message-----
> From: Jim Cobb [mailto:cobber@ci*.co*]
> Sent: Saturday, 2 September 2000 1:33
> To: Guy Morin
> Cc: Tech Diver
> Subject: Re: 80/20 deco
>
> So what you are telling me that you will use whatever it gets you out of
the
> water quicker, damage to your body be damned, and whatever I say or
anybody
> else says will not make you change your mind.
>
> I don't know what it takes to get you guys to realize that the idea with
> deco is to remove nitrogen from you body and you don't do this by
breathing
> more nitrogen. Nitrogen is what causes the damage.
>
> I also, IMHO, your thinking is flawed when you presume that using 80/20
> obviates the need for air breaks. Seems to me if you are doing *any* mix
> where you are spending extensive time at 1.5 PP02 or above you would want
to
> do air breaks to avoid long term damage to your lungs.
>
> Oh, yeah, the only thing that matters is getting out of the water fast, I
> forgot.
>
>   Jim
> -------------------------------------------------------------------
> Learn About Trimix at http://www.cisatlantic.com/trimix/
>
> From: Guy Morin <xnet@vi*.ca*>
> Date: Fri, 01 Sep 2000 09:24:54 -0400
> To: Jim Cobb <cobber@ci*.co*>
> Cc: Tech Diver <techdiver@aquanaut.com>
> Subject: Re: 80/20 deco
>
> Hi Jim,
>
> Thank you Jim for confirming what was elucidated
> in the post. For myself, you are quite right that I will
> be using the theoretical model since it has a good
> track record, and consistently estimates what I am
> actually diving. Doesn't the WKPP have something
> in regard to diving to what is planned? I would have
> to guess not, since they never dive what they plan.
>
> Only a fool would dive following the WKPP method
> without knowing all the details of what they practice,
> and that certainly isn't available on the net, on this list,
> or through word of mouth.
>
> As far as your practice versus theory, well that part
> is going to be ignored the WKPP obviously hasn't
> put in the same effort in 36/80 deco as it has in 50/100.
>
> On another note, remember that it is someone who was
> promulgating the WKPP method as being superior that
> pointed out the tissue loading from the theoretical model,
> not me. Let's keep that little detail in mind, shall we? He
> who lives by the sword...
>
> Finally, I will point out that from a logistical and consumables
> perspective, 50/100 deco does make better use of resources.
> If I was wanting to get hundreds of divers through the water
> to stage a big push, that would be my choice too. The major
> costs for a large operation is gas consumables. Using 36/80
> deco requires a greater investment in blending, and gas
> matching, and wastes a lot of gas. The reasons are obvious,
> getting off back gas at around 100' prevents the back gas
> from getting drained as would be the case in 50/100 deco.
> Using back gas in deco allows it to be drained following more
> liberal rules than thirds. In addition, since shallow deco allows
> switching to back gas, that makes further use of back gas,
> and economizes the O2. Using O2 is simple to blend, and
> is insensitive to error. Since a lot of time is spent at the
> shallow stops, not having to blend huge volumes of gas,
> and the subsequent analysis required, and schedule tweaking,
> it makes a lot of sense, especially on that scale.
>
> So, from an operational standpoint, 50/100 is by far the best
> choice. For the diver who doesn't have to worry about consuming
> millions of cubic feet per year, and who wants accurate deco
> estimation in a field environment that often does not afford
> the luxury of a decompression chamber, something more "consistent"
> makes a lot of sense.
> --
> Guy
>
> --
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