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In a message dated 9/29/98 9:44:03 PM Eastern Daylight Time,
rthomps@ma*.co*.mi*.ed* writes:
> My original query which began this thread stemmed from my thinking about
> the following scenario: Each of a pair of air divers descends with two
> deco mixes, and removes both deco bottles and leaves them on a wreck at
> the point the buoy line ties into the wreck. The pair penetrates the
> wreck via an access point nearby. At the turn-around point deep inside
> the wreck, one buddy loses *all* of his/her backgas. Upon exiting the
> wreck, the now air-sharing buddies cannot locate their four deco bottles
> (or the buoy line). The buddies must now make a free ascent, blow a bag,
> and deco on one diver's remaining air.
>
---------------------------------------------
Ronald,
Sorry I misunderstood your original scenario.
I calculated this on Abyss and came up with 23 min total deco diving
as above, and 29 min with only 100% O2 for deco.
Why use the 50% ?
If you forget the 50% and just go with 100% you can carry it into the
wreck fairly easily in an alum 40 tucked in close and eliminate the risk
of being caught without deco gas - far more important than having to add
about 6 min to total deco time by dropping out the 50% and, you save
yourself the time & trouble of securing stage tanks and the need to pick
them up on the way out in an emergency (4 tanks).
With a single carried deco gas, as opposed to staging 2, you;
1 Virtually eliminate the risk of loosing deco gasses.
2 Don't have to stage tanks. (more bottom time for exploring)
3 Don't have to pick them up. (darn hard if you are having to hold
a regulator in your partners mouth or work his BC)
4 Simplify deco planning and slate references in a crisis.
5 Are not bound to returning the way you came and can take
advantage of other exits without loosing deco gas.
If nothing goes wrong 6 extra minutes of deco is no problem. If
something does go wrong managing the second deco gas and
re-acquiring staged tanks will add a lot of task (and risk) to the
situation. Having a single deco gas on you eliminates a lot of potential
headaches and problems in return for just a little more resistance and
a little more time at the stops.
Of course, if we were going to really do this dive right we would have a
support diver and a chase boat - right ? Ahhh compromise !
Chuck Boone
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