Dave, you need to stop posting.  I don't have enough time to spend all
of it debunking this shit.

First off, climbing a ladder with all of your cylinders attached to you
after a long or deep dive is pretty stupid.  This sort of exertion
immediately following an ascent is likely to induce a type 1 DCS hit,
if you were anywhere near your ceiling upon surfacing.  This is what
surface support and other team members are for.

Second, pony bottles of any type are a bad idea.  Putting a gas
cylinder in a location that necessitates either using a long SPG hose,
or not being able to read the pressure off the bottle, in a location
where it is difficult if not altogether impossible to disentangle, and
where it is possible to have a second stage in any position on your
body that might get confused with either of the back gas regulators,
and where you can not positively visually identify the gas being
breathed, where you can not easily hand it off to another diver, where
you can not keep the valve off and only turn it on when you go to use
that particular gas is an accomodation to playing odds.  A gas should
only ever be breathed from if you can make a one hundred percent
positive identification without any sort of tactile aid.  This is why
the argon can be mounted on the back tanks - this tank is never, ever
breathed from, nor could it be because there is no second stage
attached to it.

Third, 190ish is not the borderline depth for air vs. trimix.  If you
accept the liability imposed by the narcotic potential of air at
anything approaching that depth, and the damage done to you by the
nitrogen when decompressing, you need to take a serious look at your
risk/benefit analysis.  Better yet, quit diving and take up golf.  I
will do bounce dives to 100 on air, but in fact air is not a good gas
for ANY depth.  I use trimix a lot for shallow reef dives these days.

Fourth, a 40 of oxygen filled to supply pressure (2015-2200 psi)
contains more than enough gas to deco out on for that dive, unless you
are doing ridiculous bottom times, in which case you should ask
yourself if you can do two shorter dives instead of one long one, or
you are doing a ridiculous deco for a given dive, or if your RMV is
poor and you need to hit the gym.

Fifth, ignoring the possibility of being blown off the anchor line is a
complete lack of foresight.  Carry all of your deco gas with you,
unless you can guarantee you will be swimming back over it, such as is
the case with caves, where you either come back to it or you die. 

Sixth, closed circuit apparatus introduces additional complexity to the
system in the form of electronics, and additional failure modes.  Since
you need enough gas to bail out on open circuit anyway, the
justification for using this device eludes me.  I could see using a
rebreather for extremely long exposures which would require several
stages of bottom mix, or when hypothermia is an issue in very cold
water, but for the dive you describe a component failure probability
analysis puts open circuit well on top. 

-Sean
 


On Sun, 24 Oct 1999 11:02:42 -0400, Dave Sutton wrote:

>>>The guy was carrying two WKPP type sidemounts
>>
>>No he was not , I was talking about me.He had 2 steel stages left and
>>right.
>
>
>OK. No sweat. He had way too much shit on.
>Side mounts plus doubles? Too much shit.
>No wonder it (literally) dragged him to his
>watery death.
>
>Reminds me of the closing lines of the
>'New Jersey Wreck Divers Song" which
>ends like this:
>
>"And with guages and guages,
> From catalog pages,
> He lept into the water and drowned"
>
>
>>You have 2 different dive trips to the doria going here.Doria 98 I had the
>>mask problem on the first dive and had my stages right and left.The ladder
>>on the boat in 98 sucked ,in 99 they had a new ladder , I could climb that
>>ladder with 4 stages anywhere on me ( not steel stages)if I wanted too.
>
>
>OK. Same issue, however, of sides interfering with laddering.
>
>
>>>I've seen many a deep
>>>blue water wreck dive done with twin overpumped 80's and a 40 cube
>>>poney with 02 in it.
>>
>>What depth and where is the blue water you refer to.What is the goal ,
>plan?
>>
>>>  Think about it: Less drag for sure than side mounts
>>>and adequate gas for bottom and deeper stops and 02 for the shallower
>>>hang. But poneys suck 100% says the guru(s) from the South. I better
>>>not get off on that subject either... ;-)
>
>
>
>Say, the Choapa. 190-ish. Open water. High relief. Bad vis.
>Just about at the border depth for air V/S trimix. I choose
>trimix on this day, meaning I'm also looking for 02 deco.
>Not sure I'm getting back to the anchor line. Set up to do
>an intentional off-anchor deco. Blow a bag and hang on
>my reel line (cave reel or manila is yer choice). Wear
>two 104's into an OMS manifold and carry a 40 cube
>poney of oxygen for deco. Side mount the poney or
>back-mount like olden days? Not sure best answer.
>For sure an overpumped 40 is going to be enough 02,
>though. Side mount does me little real advantage here,
>I'm a slow swimmer and not covering much ground.
>Snagging hazards of the back-rig V/S the side rig are
>about a wash. The ladder splash-zone environment is
>easier to deal with using the back-mount. I have no
>intent of stashing my 02 bottle on the bottom, since
>if I could find it,  could find the anchor line. if I can find
>the anchor line, why am I carrying my own 02?
>
>What's the need to carrying -4- bottles to the Doria?
>You -are- going to go back to the anchor line for deco.
>It's easy to find. You hopefully have hung-gas waiting for
>you on a hose from  K bottle on the boat. Carry what you
>are going to breath, leave the deco gas on the boat.
>
>
>
>>I could agree here if you were more detailed of the dive.
>
>
>See above. I'm not convinced that  4 bottle cave rigs belong
>offshore. No resting place on the bottom, eh?
>
>This is -the- reason that I'm going to a fully closed rebreather.
>I have enough gas to do anything I want to in a package weighing
>less than a set of twin 72's. That's -including- enough off-board
>gas to do my deco after any bailout to open circuit.
>
>
>
>
>>>I'm not the sidemount expert so I'll keep my yap shut from here. But
>>>it'll take some convincing to get me on board the idea that they are
>>>always appropriate in high current blue water diving.
>>
>>There are NO experts on this list , all the experts I've heard of are
>>dead.Thats the first thing they say about them in their obituaries "John
>>Doe was an expert scuba diver", screw it I'm still learning don't want to
>>be an expert:)
>
>Yup. Agreed. This is -the- issue. Nobody should feel that they are going to
>be obscenely ridiculed by anyone here for asking questions or sharing
>their experience. That does nothing but close communication lines.
>I teach 'Crew Resource Management' and 'The Philosophy of Safety'
>in my aviation job. The -main- point of CRM is for the crew to focus
>on -what is right-, not on -who is right-.  Whe a crewmember has
>an emotional stake in a position (IE an ego problem) he'll very likely
>die before doing anything about it. When airplanes are involved, it's
>a big issue. Open communications without fear is the resolution.
>-Any- crewmember should feel free to call to the entire crews
>attention any issue that requires resolution, for group attention.
>This raises the entire situational awareness of the group. When
>any crewmember feels that he will be made socially awkward
>by his/her input, he/she will probably say nothing.
>
>Before each takeoff, the Captain of a jet gives a takeoff brief. This
>includes all safety related items and the plan of action in case
>something goes wrong. A typical brief might include something
>like this "In case of an engine fire after V1, we will consider it
>an in-flight emergency. I'll fly the aircraft to 1000 feet and level off.
>You will do nothing until then except cancel the audio warning of the fire.
>At 1000 feet we will conduct the emergency engine fire checklist.
>We will then reconfigure the aircraft to best engine inop climb speed
>and return to the airport".
>
>Now, here is the good part. The Captain can 'shut the door' on
>communications from his subordinate by saying "Do you have
>any questions", thus forcing the copilot to reveal any weakness
>in his understanding by asking a question that might reveal a
>weakness. Few copilots will do so, even if they are clueless.
>-OR- the Captain can 'open the door' on communications by
>actively soliciting feedback by asking 'Do you have anything to
>add to that?" which is an open statement. The copilot might answer
>by saying "Do you want me to set the alt alerter at 1000 feet if
>you level after a fire, or would you prefer to do it yourself".
>
>How does this affect our group? We have two choices:
>
>A: We can 'shut the door' on discussion by saying
>"You ignorant fool. Your way is stupid. Only assholes dive like that.
>I'm the expert and you are so friggin stupid. I know what is right!"
>
>Or B: We can concentrate on -what- is right and not -who- by asking
>"Really. I have not considered that technique. Can you explain?"
>
>Which is better? Civility or rudeness? Open or closed communication?
>Driving away those offended by the tone, or being nice and entering
>into polite debate to convince a wayward entry that there is a better way?
>
>
>
>>You are answering a great many questions from the list , ready for a break?
>
>
>Naah..... If anything, we have begun to use the list for the correct reason
>and not to push any particular agenda.
>
>Now, does anyone have anything to add to that?? ;-)
>
>
>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'.

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]