> -----Original Message-----
> From: SouthEast US Scuba Diving Travel list
> [mailto:[log in to unmask]]On Behalf Of John Nitrox
> Sent: Thursday, July 06, 2000 6:47 PM
> To: [log in to unmask]
> Subject: Re: [SCUBA-SE] Draeger rebreathers (was: Re: [SCUBA-SE]
> DivingDoubles)
>
>
> At 08:15 AM 7/6/00 -0500, Mike Wallace wrote:
>  In fact for the camera phob, the Dolphin is a damn nice unit.
>
>
>         Although I only have experience with the Atlantis and not
> the Dolphin, as
> I understand things from Draeger's literature and through speaking with
> their representatives and Dolphin users, there are still a few negatives.
> First, you are betting your life on your O2 analyzer,

O2 analyzer? Atlantis/Dolphin ? These systems don't have a oxy gauge.

>not just on just the
> oxygen toxicity side, but also, as Carl pointed out, on the hypoxia side.
> The more stress you are under or the more vigorously you move the
> lower the
> PO2 and consequently the oxygen available to your brain.

Looking at the margins that are used in the design, I would say this is not
the
biggest problem with the Dolphin/Atlantis design.
>
>         The old Atlantis had a mouthpiece shutoff valve which was
> so difficult to
> work that buddy breathing guaranteed wet 'sorb, but disregarding that,
> buddy breathing is not a viable solution to a problem with these
Buddy breathing and rebreathers ?? How can you even mention such an option
??

> semi-closed circuit rebreathers, one must have a bailout bottle
> and the wit
> (read brain well perfused with oxygen) to deploy it when needed.  Worse
> still, in the scenario Carl obliquely suggested of a broken gauge
> or poorly
> monitored gauge, any already low PO2 situation will be exacerbated by
> rising towards the surface, and because of the relatively small
> size of the
> rebreather bottle, less gas would become available for breathing than with
> open circuit scuba.

We were talking about the Dolphin here. Right?
I don't understand what you are saying here. Since the bailout system is
completely separate
from the rebreather system, I don't see what the size of the rebreather
bottle has to do with
amount of gas I have for the bailout system.

>
>         Draeger has made some bad changes to the Atlantis while
> failing to make
> the one change which would make either rebreather better for
> photographers.

>  Unlike the Atlantis, the Dolphin only has one gas orifice which prevents
> the optimization of the nitrox for the depth of the dive.  one cannot
> get extended time on a shallow dive by using nitrox with a higher O2
> content, as one could with the Atlantis.

Correct me if I'm wrong, but what you are describing is the Draeger Ray.
The difference between the Atlantis and the Dolphin is minor.
The counterlung material is different, the relief valve is slightly
different,
but you still have the same three nozzles for 60%, 50% or 40% O2.

The Draeger Ray only has 1 nozzle, therefore just 1 possible nitrox mixture.
The Ray has a standard oxy gauge, as opposed to the Dolphin which only has
an
additional connection for an optional oxy gauge.

> On the other hand, the noisy
> belch on every fifth breath, or so, which scares the hell out of fish is
> still there.  While the bubble diffusion technology which would make both
> the Atlantis and Dolphin more suitable for photographers is available,
>         Of course, because of the counter lung, it is much more
> difficult to control one's depth and consequently to approach fish
smoothly and
> naturally.

I would call it difficult, but different. It is only difficult when you are
used to an open system in combination with your lungs. After some time with
the rebreather under water, you will start to appreciate the fact that you
can stay
at one depth without any problem.


>
> DPTNST,
>
>
> John
>