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See, this makes better sense, only if the unit saves you gas on the =
bottomgas, why don't you use the unit for deco (with 50 and 100 for =
deeper dives) I know that the unit gives you better advantages the =
deeper you go (on gas consumption) but I would think that you would the =
unit for deco as well?
Why is it standard procedures to carry the twinset on the side of the =
unit? As G3 has stated so many times (and I agrees with him) carrying =
stages is not a problem, so why not just have another stage with the =
bottomgas
Regards,
Mike
-----Original Message-----
From: John Grogan <john@ro*.co*.uk*>
To: Mike Langborg <mslangborg@cl*.ne*>; techdiver@aquanaut.com =
<techdiver@aquanaut.com>
Date: Tuesday, June 01, 1999 10:59 AM
Subject: Re: Halcyon rebreather
=20
=20
Hi Mike,
I'm one of the Halcyon divers that you saw. Let me try to answer =
some of your queries.
=20
We were preparing for a 30m dive when you met us and as such we did =
not carry deco bottles with us for that dive. For our planned bottom =
time and backgas (30/20) there was no need for it although our deco =
bottles were on the boat - for use on subsequent days.
=20
It is standard procedure to use the twin bottles carried either side =
of the unit. The bottles are connected by an isolated manifold and we =
use our standard open-circuit regulator set-up. The only addition is 2 =
extra hoses - one which drives the RB and the other feeds the regulator =
on the mouthpiece block.
=20
All dive planning is done as though we were on open circuit - =
including decompression. The Halcyon is not a fixed ppO2 unit so the =
perceived "big advantage" of such units do not apply here. We do an =
open-circuit decompression on all dives. If you find that you're =
getting a big deco advantage moving from open circuit to fixed ppO2 =
closed circuit then you're probably doing the wrong deco and/or using =
the wrong gases.
=20
There are a number of advantages to this - your bailout deco is the =
same as your planned deco. You can easily mix halcyon divers with OC =
divers and everyone is still running the same plan. The gas that you =
carry for the dive is also your bailout gas - our stage bottles are 7L =
(45cuf) so they hold all the deco gas we need should we go open circuit =
for deco.
=20
I guess one of the most important things to remember about the =
Halcyon is that it is a gas management tool. It allows us to achieve =
good gas efficiency on our dives. We typically go high on helium on =
many dives for a number of reasons and as you know, helium is expensive =
in this country. The gas savings that we make by using a halcyon make =
it easier to do this.
=20
In deciding on stages, back mounted gas etc, you need to consider =
the worst possible scenarios, look at how to get out of them and plan =
accordingly. Typically, the worst scenario is both RB's fail resulting =
in both divers going to OC, then 1 diver experiencing a complete OC =
failure. This results in 1 diver passing the long hose and both divers =
exiting on 1 diver's backgas. In the ocean, this means a safe ascent to =
the depth where the divers can switch to deco gas, or if shallow enough =
not to require deco gas, then to the surface. In cave, this would mean =
sharing until you reach a stage drop (although typically, WKPP do not =
use the backgas but use stages - backgas is for emergencies).
=20
With this in mind, we always use the twinset mounted with the unit. =
We could carry our gas in a stage bottle, but for the type of diving we =
do, we don't feel that's suitable. To answer some of your questions =
directly - we would use deco gas for deeper dives (our deco gas is 100% =
oxygen and 50% as well if diving deeper) and indeed did use it on =
subsequent dives. Our deco is OC deco.
=20
Hope this helps.
Best,=20
John.=20
On a resent diver trip down south (Waymouth) we met some DIR =
divers. Some dived the Halcyon Rebreather (open water).
=20
It was rigged with two 7 litres (45 Cft.) on the sides of the =
unit. We asked if they did not use stages for DECO, and the answer was : =
NO
=20
They dived to about 30 meter (100 ft) so I can se why they might =
opt to leave stages, but when we asked if they used stages on the deeper =
dives the answer was still : NO.
=20
My question is therefor. Is this standard DIR(WKPP) procedures. =
If so why? Since this unit is NOT constant PPO2 you must have a longer =
hangtime compared to OC (and what about OC bailout?).
=20
Secondly why are the bottom mix carried on the back (on the =
sides of the unit) when a single stage would do the same, and easily can =
be carried along the deco stages?
=20
It doesn't make sense to me, so please enlighten me.=20
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<BODY bgColor=3D#ffffff>
<DIV><FONT color=3D#000000 size=3D2>See, this makes better sense, only =
if the unit=20
saves you gas on the bottomgas, why don't you use the unit for deco =
(with 50 and=20
100 for deeper dives) I know that the unit gives you better advantages =
the=20
deeper you go (on gas consumption) but I would think that you would the =
unit for=20
deco as well?</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Why is it standard procedures to carry the twinset =
on the side=20
of the unit? As G3 has stated so many times (and I agrees with him) =
carrying=20
stages is not a problem, so why not just have another stage with the=20
bottomgas</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Regards,</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Mike</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV> </DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; PADDING-LEFT: =
5px">
<DIV><FONT face=3DArial size=3D2><B>-----Original =
Message-----</B><BR><B>From:=20
</B>John Grogan <<A=20
=
href=3D"mailto:john@ro*.co*.uk*">john@rockportcapital.co.uk</A>=
><BR><B>To:=20
</B>Mike Langborg <<A=20
href=3D"mailto:mslangborg@cl*.ne*">mslangborg@clara.net</A>>; =
<A=20
href=3D"mailto:techdiver@aquanaut.com">techdiver@aquanaut.com</A> =
<<A=20
=
href=3D"mailto:techdiver@aquanaut.com">techdiver@aquanaut.com</A>><BR>=
<B>Date:=20
</B>Tuesday, June 01, 1999 10:59 AM<BR><B>Subject: </B>Re:
Halcyon=20
rebreather<BR><BR></DIV></FONT>
<DIV><FONT color=3D#000000 size=3D2>Hi Mike,</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT><FONT size=3D2>I'm
one of =
the Halcyon=20
divers that you saw. Let me try to answer some of your=20
queries.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>We were preparing for a 30m dive when you met us =
and as=20
such we did not carry deco bottles with us for that dive. For =
our=20
planned bottom time and backgas (30/20) there was no need for it =
although=20
our deco bottles were on the boat - for use on subsequent =
days.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>It is standard procedure to use the twin bottles =
carried=20
either side of the unit. The bottles are connected by an =
isolated=20
manifold and we use our standard open-circuit regulator =
set-up. The=20
only addition is 2 extra hoses - one which drives the RB and the =
other feeds=20
the regulator on the mouthpiece block.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>All dive planning is done as though we were on =
open=20
circuit - including decompression. The Halcyon is not a fixed =
ppO2=20
unit so the perceived "big advantage" of such units do not =
apply=20
here. We do an open-circuit decompression on all dives. =
If you=20
find that you're getting a big deco advantage moving from open =
circuit to=20
fixed ppO2 closed circuit then you're probably doing the wrong deco =
and/or=20
using the wrong gases.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>There are a number of advantages to this - your =
bailout=20
deco is the same as your planned deco. You can easily mix =
halcyon=20
divers with OC divers and everyone is still running the same =
plan. The=20
gas that you carry for the dive is also your bailout gas - our stage =
bottles=20
are 7L (45cuf) so they hold all the deco gas we need should we go =
open=20
circuit for deco.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>I guess one of the most important things to =
remember about=20
the Halcyon is that it is a gas management tool. It allows us =
to=20
achieve good gas efficiency on our dives. We typically go high =
on=20
helium on many dives for a number of reasons and as you know, helium =
is=20
expensive in this country. The gas savings that we make by =
using a=20
halcyon make it easier to do this.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>In deciding on stages, back mounted gas etc, you =
need to=20
consider the worst possible scenarios, look at how to get out of =
them and=20
plan accordingly. Typically, the worst scenario is both RB's =
fail=20
resulting in both divers going to OC, then 1 diver experiencing a =
complete=20
OC failure. This results in 1 diver passing the long hose and =
both=20
divers exiting on 1 diver's backgas. In the ocean, this means =
a safe=20
ascent to the depth where the divers can switch to deco gas, or if =
shallow=20
enough not to require deco gas, then to the surface. In cave, =
this=20
would mean sharing until you reach a stage drop (although typically, =
WKPP do=20
not use the backgas but use stages - backgas is for=20
emergencies).</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>With this in mind, we always use the twinset =
mounted with=20
the unit. We could carry our gas in a stage bottle, but for =
the type=20
of diving we do, we don't feel that's suitable. To answer some =
of your=20
questions directly - we would use deco gas for deeper dives (our =
deco gas is=20
100% oxygen and 50% as well if diving deeper) and indeed did use it =
on=20
subsequent dives. Our deco is OC deco.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Hope this helps.</FONT></DIV>
<DIV><FONT size=3D2>Best,</FONT> </DIV>
<DIV><FONT size=3D2>John.</FONT> </DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 solid 2px; MARGIN-LEFT: 5px; =
PADDING-LEFT: 5px">
<DIV><FONT color=3D#000000 size=3D2>On a resent diver trip down =
south=20
(Waymouth) we met some DIR divers. Some dived the Halcyon =
Rebreather=20
(open water).</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>It was rigged with two 7 =
litres (45=20
Cft.) on the sides of the unit. We asked if they did not use =
stages for=20
DECO, and the answer was : NO</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>They dived to about 30 meter =
(100 ft) so=20
I can se why they might opt to leave stages, but when we asked =
if they=20
used stages on the deeper dives the answer was still : =
NO.</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>My question is therefor. Is =
this=20
standard DIR(WKPP) procedures. If so why? Since this unit is NOT =
constant PPO2 you must have a longer hangtime compared to OC =
(and what=20
about OC bailout?).</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>Secondly why are the bottom =
mix carried=20
on the back (on the sides of the unit) when a single stage would =
do the=20
same, and easily can be carried along the deco =
stages?</FONT></DIV>
<DIV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DIV><FONT color=3D#000000 size=3D2>It doesn't make sense to me, =
so please=20
enlighten =
me.</FONT> </DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>
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