Dave, there are distinct flaws in logic in some of the arguments you
make.  With regard to independent doubles on the back being
logistically identical to sidemounts, they are not, for in the case of
a first stage failure the sidemount diver can control gas delivery by
manual operation of the tank valve, can change out regulators on these
tanks when necessary, and is in a better position to free these
cylinders from entanglement.  In addition to the gas identification
problem, routing the regulator hose from a back mounted pony over
either shoulder is a problem, since you either interfere with the
ability to donate the long hose, or you add an extra hose in a position
where a conditioned response reaction could confuse these hoses, such
as when you have a runaway inflator and need to disconnect in a hurry. 
It seems to me that you have not, in fact, come to a complete
understanding of the real risks of these dives, and the liabilities
imposed by these gear placement decisions.  Using a single tank for any
dive requiring decompression stops is an unreasonable assumption of
risk, if you are giving any consideration to a gas sharing scenario. 
Look at the component failure survivability - the isolation manifold
provides the maximum possible redundancy, providing access to half of
your gas in the absolute worst case scenario.  The justification for
using a pony bottle arises from either the fact that you are
consistently mismanaging your gas supply, and thus need the pony as a
crutch, or that you are doing a dive that genuinely requires the
redundancy and failure survival probability of dual regulators, in
which case the isolation manifold is the safer decision.  Independent
singles are a bad idea - do the failure analysis, and consider an out
of gas buddy at the point of maximum penetration/turn point of the
dive, add a first stage failure during egress and you're SOL. 
Independents with mismatched tank capacities (such as a single with a
pony) just compound the problem.  The gear choices and placement
decisions I have made all arise from the consideration of ALL factors,
and a complete ability to deal with all conceivable emergencies,
utilizing conditioned responses which are consistent regardless of
environment, giving due consideration to my dive buddies.  This means a
complete component failure probability analysis (system failure vs.
mission failure), and choosing the appropriate gear.  Accomplish each
redundancy or emergency option with the least amount of inherent
complexity, and take a look at what you have ---> DIR.  You mentioned
that the five finger dry glove system provides adequate warmth even in
Antartica (McMurdo water temp about -2 C, or something to that effect),
and yet you may still choose to use 3 finger mitts for abrasion
resistance when digging, even though you know this will reduce
dexterity (and hence your ability to manipulate valves, break down your
second stages, etc.), and to compensate for the dexterity loss, you use
a larger spool of line, etc.  Think carefully about what is the most
important consideration here.  The basis of all equipment decisions
should be safety, with dive objective a secondary issue.  It seems that
the decision to use 3 finger mitts in this case initiates a string of
sub optimal equipment choices, from a safety perspective.  The DIR
diver does take environment into account, but without necessitating
equipment changes that are significant enough to affect conditioned
response to emergency scenarios, or to increase liability through
entanglement hazards or significant drag increases (which, IMO, is a
larger safety issue that you seem to acknowledge).  Such changes might
entail adding a lift bag for wreck, a safety or jump spool for cave,
gloves and larger bolt snaps for cold water, etc.  You notice that the
common theme here is the variance of dive specific tooling, and not of
the core life support system itself.

There is nothing wrong with innovation.  Most of the gear I use now was
not available to me only a few years ago.  I designed my own backplate,
made my own tank bands and machined my own burst plugs, because I was
not satisfied with what was available.  For the same reason, I am using
lights, fin straps, wings and other gear which is designed with maximum
safety as the primary focus.  It is commendable that you realized the
advantages of the manifolded gas supply so long ago, and expended the
effort to create what was not available.  For the same reason that gear
is evolving, so too are diving practices and safety procedures.  It
seems somewhat hypocritical of you to suggest that you have been diving
safely with established techniques for twenty odd years, and so can
pursue your own path in diving without due consideration of these
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.  What exactly are your
priorities?

-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
>
>
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