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Reply to: RE>Rebreather toys...
>>Can one rebreather sustain two divers for the ascent and decompression
>>hang?? How is buddy breathing off of one of those? The unit has to
>>work not quite twice as well as required for one diver.
>
>It's more than this. There isn't an "octopus" unit as far as I can see.
>It seems as though you'd be forced into a buddy breathing scenario. I'm
>not sure exactly how they would teach this. Since it's a closed circuit
>system - if you were buddy breathing you'd have to hold your breath until
>you got the mouthpiece again otherwise I think you'd run out of gas
>pretty quickly.
That's exactly my point... If two divers have to buddy breathe off of one unit,
the unit could quickly become exhausted since each person is breathing out into
the water (i.e. "open circuit" breathing) rather than back through the
rebreather ("closed circuit" breathing). Bail out bottles, etc. are fine, but
not under a lot of circumstances such as deep inside the Andrea Doria, etc.
Holding your breath is a bad idea - especially as, at some point, you'll be
ascending and we all know that holding your breath during an ascent is a bad
idea.
Assuming that you bring down an AL80 tank. How long will it last you at, say,
250 feet? Now, given the CIS-Lunar setup (and I've only seen the unit once, so
it may have changed since then), WHERE do you PUT an AL80 tank? What gas
mixture do you put into it?
It would appear that the use of rebreathers, in some ways, incur an even higher
amount of planning - creating what I think of as "siege diving", much like
siege climbing where one establishes base camps and a string of camps with
supplies, etc. due to the appearance to me of the impossibility of sharing air
from one rebreather unit and the difficulty of carrying additional air sources.
But I still want one.
-- Kevin --
--------------------------------------
Date: 4/5/94 11:14 AM
To: Kevin Klop
From: Carl G Heinzl
> Reply to: Rebreather toys...
>On of the things that I wonder about the advent of rebreathers (and I admit
>that _I_ want a rebreather too) is the question of, "I'm at 100 feet and, for
>some reason, my unit stops working. My buddy, being another toy afficiando
>like myself, also has a rebreather." Now comes the million dollar question:
Depends - if you're running a high enough pp02 and don't have any required
deco stops (or not very long deco stops) it seems that a 30 or 40 cu ft
pony would be the right thing to have. I would worry much more about
being inside a ship at 250 feet and have a failure. A previous generation
of the CIS Lunar unit was completely redundant (as someone already pointed
out), but that has since been dropped.
>Can one rebreather sustain two divers for the ascent and decompression hang??
>How is buddy breathing off of one of those? The unit has to work not quite
>twice as well as required for one diver.
It's more than this. There isn't an "octopus" unit as far as I can see.
It seems as though you'd be forced into a buddy breathing scenario. I'm
not sure exactly how they would teach this. Since it's a closed circuit
system - if you were buddy breathing you'd have to hold your breath until
you got the mouthpiece again otherwise I think you'd run out of gas
pretty quickly.
>Anyone have any thoughts on this? Sure, you can always have a pony bottle down
>with you, but from what I saw of CIS-Lunar, the unit is heavy enough without
>adding an additional pony bottle.
65 pounds total for the CIS Lunar unit is what was quoted by Rich Nordstrom.
I think that a bailout bottle is always a good idea. From some of the
pictures that we saw in the technical seminars at the Sea Rovers - 65 lbs
plus an additional bottle is *nothing*. There were pictures of people
entering the water with up to *8* bottles - twins on the back plus a nitrox
for deco plus a small o2 for shallow deco, plus two bottles on each side!
Now, admittedly, this is pretty extreme, but when diving deep, it's not
unusual to have twins plus a nitrox bottle for deco plus a small pure o2
for shallow deco.
>Now, I know that the rebreathers have an additional air/O2/something bottle
>because there's no rebreather that doesn't have some loss, but is that bottle
>sufficient?
Virtually the only time you actually loose air is when you ascend (the
resulting expansion of gas leaves the system). This means that you
do not consume very much gas. The CIS Lunar system does run on two
separate bottles - a pure O2 and a diluent. This diluent can be virtually
any gas that you choose. From what I understand, you must tell the
computer what the composition of this gas is so it knows how to mix it
for you to give you the desired pp02.
-Carl-
--
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Subject: Rebreather toys...
From: Carl G Heinzl <heinzl@wi*.en*.de*.co*>
Date: Tue, 5 Apr 94 13:43:36 EDT
To: techdiver@opal.com
Cc: heinzl@wi*.en*.de*.co*
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