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This sounds somewhat contradictory to me...

On Wed, 20 Sep 1995 22:57:00 +0000 Mark Welzel said:
> Bob Raimo has brought up a point of bailout bottles. It's always
> been my understanding that the 50/50 I was carrying was only for
> deco and I carried enough bottom mix to do my deco if I lost my
> deco bottle. I took ANDI's course so I could get deco fills.  [snip]

First off, this is using the pony as a managed gas supply, in contrast
to the current thread of the pony being a bailout.  Not that I disagree
since it depends on your plan, but let's proceed...

> Getting to this bailout issue, aren't you supposed to have enough
> bottom gas in case of emergency? And if you carry a pony (be it a
> 40 cu.ft. or a slung 80 cu.ft) shouldn't it have gas you can breathe
> at any depth you might reach?

Well, you can't use EAN50 very deep, making it an unsuitable bailout gas.

So here is our quandry... is the pony a bailout, or deco gas, or what?
You could use it for both with limited depth but certainly not EAN50.  And
if you ARE using it as a "managed gas" then you need an SPG on it (despite
recommendations otherwise we've already heard).  You can't have both.

Personally I carry a large pony (relatively speaking, 30cf).  For an Al80
primary, this is a bailout bottle until my primary reaches ~1200psi.  At
that point you can view your setup as "dual 30s" depending on your dive
plan.  For deep, square profiles it should remain a bailout gas; but for
a multi-level wall dive, perhaps now you can switch it's function to that
of a managed gas supply if you're already at a civilized depth.  You can
then continue your dive (extend bottom time) using it as a managed gas
without risking the bailout option - just switch gas supplies so that you
maintain a suitable bailout gas volume (10-20cf assuming no deco stops).

This may be a setup as flame bait, but what's wrong with "switching" the
role of the pony from bailout to managed gas assuming you are past the
point where a full 30cf of bailout supply is necessary?  Taking that one
step further, if you use a "lean" EANx mix, say EAN32, you can use it
for either bailout or managed gas provided your max depth doesn't exceed
the max ppO2 levels of the pony mix - and you get the added advantage of
improved deco/stops whether you use it for bailout or managed gas.

I'm thinking of wall dives again (for emphasis); I'd never advocate this
thinking for a dive profile with no advantage for extending a shallower
ending depth.

[\] Jeff Kell <jeff@ut*.ut*.ed*>

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