On Tue, 2 Nov 1999, Sean T. Stevenson wrote:

> 
> safety issues.  Open circuit is not "old" technology, but rather the
> correct equipment to use when the additional complexity and failure
> modes introduced by a closed circuit system are not warranted, such as
> is the case with any dive that could be accomplished on open circuit,
> without respiratory heat loss or dehydration becoming so significant an
> issue that to use the rebreather would be safer.  
 
I've spent a fair amount of time diving various closed-circuit systems,
and I've come to the conclusion that the issue of additional complexity
isn't particularly significant.   With proper training, and proper
backup, a CCR can be almost as safe as open circuit, and has
definite advantages in many areas, the biggest being the
8-12 hours of available gas at any depth, which completely
eliminates any sense of time pressure.

Once you have your failure-response modes drilled into your
head (the equivalent of valve open/close and isolator drills on OC),
all you really have to remember to do while diving is check
your O2 levels every 7-15 minutes.  That takes about two seconds
on most rigs.

For backup purposes, the winning combo is a fully automatic
mixed gas CCR for primary, and a small backup rebreather
that will give a few hours of duration in the case of 
primary failure.  Better yet if the backup rebreather
can be handed-off to a buddy in need (working on that
one right now).

-Will






> 
> -Sean
> 
> 
> 
> On Mon, 1 Nov 1999 13:08:23 -0500, Dave Sutton wrote:
> 
> >><< "Poneys" are too stupid to recommend on a modern "tech" list,  >>
> >
> >
> >>Well , ponys added to a single  80 , or 100 or 120 cu ft tank for a no-deco
> >>or short deco single gas ( air or nitrox)  70 - 130 foot sport dive
> >........may
> >>not be what one would consider technical diving .  But they are a very good
> >>valid  configuration for average divers in this area , IMO better than a
> >>h-valve , or an octopus for redundancy.
> >
> >
> >This all goes (again) to the application of the proper technique
> >to meet the proper mission. Steve understands this, and George
> >does not.
> >
> >To proceed:
> >
> >We all dive according to our learning processes
> >and (hopefully) we look at and use the lessons
> >that have been learned the hard way by those
> >who went before us.
> >
> >The 4 levels of learning are Rote, Understanding,
> >Correlation, and Application. Diving at different
> >levels of technique can be used to understand the
> >differences.
> >
> >Rote: Method is appliued just because the diver was
> >told to do it that way, with no understanding of the
> >process. A PADI diver diving reefs after 5 pool
> >sessions is probably at this level.
> >
> >Understanding: The diver uses the techniques that
> >were taught, and understands the reason for the
> >system. This diver does not, however, develop
> >new methods nor does that diver modify learned
> >methods to meet the needs of the mission. A diver
> >wearing side mounts while diving in the tropics at
> >moderate depth is an example of this. He understands
> >the advantages of this system of rigging, but does not
> >critically analize the reasoning behind it and does not
> >use the -appropriate- technique for the day at hand.
> >A similar example is a wreck diver showing up for cave
> >diving without modifying his gear, and the same can be
> >said for a cave diver showing up for a day of wreck diving.
> >A diver showing up for a live-boating day and finding that
> >the local boats are geared for anchoring into the wreck is
> >another example, as is the opposite.
> >
> >Correlation: The diver looks at the conditions that are
> >present at any gven site and selects the appropriate
> >tool for the day. He may, for instance, recognize that
> >for many dives side mounts are appropriate, but knowing
> >that the dive on this day will be a nitrox dive to moderate
> >depths with minimal decompression obligation, he chooses
> >to rig with a single 104 and a pony. He realizes that there
> >is an advantage in security using a pony instead of an H
> >valve, and selects what is really just mismatched doubles
> >for his method. He looks at his cave reel, looks at the wave
> >conditons today, contemplates 3 finger mitts V/S 5 finger
> >gloves,  selects the mitts and along with the mitts decides
> >to use his manila reel as he knows that his dexterity will be
> >impaired and he feels more comfortable with the manila
> >line. He realizes that this is a drag addition, but weighs that
> >against the other variables and chooses accordingly.
> >He realizes that the dive boat has chosen to anchor into
> >the wreck, and while recognizing the advantages of live-boating
> >realizes that it's not going to happen today, and plans for an
> >off-anchor deco. He has enough -equipment- be able
> >to choose and enough -common sense- to do so.
> >
> >Application: This is the highest level. The diver looks at all of
> >the available techniques, finds them lacking, and based on
> >his own experience decides to design his own. He's tired of
> >listening to the 'tech' and 'cave' divers bickering with the
> >'wreckers' over such details like if independant singles are
> >unsafe, pony V/S stage bottle for deco, etc. For the life of him
> >he cannot see the difference from a gas flow and reliability
> >standpoint beween side mounts and independant singles
> >mounted in a twin harness. It bafflles his how anyone can
> >say that identifying his pony regulator (or dual singles regulator)
> >is difficult to do, since he wears them over different shoulders
> >and sees that the side mount guys seem to have no problem
> >identifying their different regs. He's recognizes that the mainstream
> >is making a lot over a little, and strikes off on his own path.
> >He is the guy likely to be working with a milling machine and
> >lathe making his own stuff. He's the guy using a rebreather and
> >not bothering with the side mounts at all. He's the guy that
> >was making ideal manifolds up 20 years ago, and he's the
> >guy making his own bailout rebreather to back up his main
> >rebreather today.
> >
> >With all due respect to the fact that I think that GI is a pompous
> >ass, he's probably in the 4th category. So are the guys who
> >would not use open circuit for anything other than bailout.
> >The guys who 'look beyond' and then do it. Not to blow the
> >horn of myself or my buddies, but we have gone past open circuit
> >and consider it old technology. Tech diiving? You bet. Mainstream?
> >Not just yet. Side mounts V/S Doubles V/S pony Bottles?
> >Who cares?  They are all obsolete. It's just a matter of time.
> >But again, that is for the 'correct' application. The 'Correlation'
> >level diver may leave his rebreather at home on nice days
> >when 100 foot O/C nitrox mode is the easy way to make the dive.
> >
> >
> >Rude comments deleted without so much as a second thought.
> >Thoughtfull comments gladly debated. Hopefully the debaters
> >will be at least at the 'Application' level, which based on the
> >comments put forth by many 'Understanding' level divers may
> >be a stretch.
> >
> >
> >Dave Sutton
> >
> >
> >--
> >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
> >
> 
> 
> 
> 
> --
> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
> Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
> 

--
Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]