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Dear List:
Thanks for all the responses about the best mix for my 150' wreck. What a nice
break from the recent flame wars. I summarized the responses, both posted
and private. Basically everyone was in the same ball park, just huddled
around different bases. The two opinions I valued the most were from Steve
Hogan and Bill Mee, which basically said USE Helium, BOOST the percentage of
Helium, for a few extra bucks, you are investing in SAFETY.
Now you all know where I will be Saturday morning.
One again, thanx.
___________________________________________________
My recommmendation to you is to boost the helium as high as you can. In
fact if you have a booster pump go ahead and try diving heliox 20 and you
will be absolutely amazed at the difference in perception and
responsiveness. Furthermore you cannot believe how well you will feel after
the dive and there will be none of the fatigue which follows deep air
diving. As for the oxygen, keep the po2 in the 1.0 - 1.2 range. Boost it to
1.4 if the dive is to be short.
I would use 23/40 (as I had mixed for our last attempt on the
Moody). Depending on the length of the dive (and corresponding deco)
I would use 50/50 and 100 for deco. The two shorter dives is far
preferable to the 1 long one for safety (cause conditions sometimes
change fast on that one).
Sounds like a great dive. On Florida wrecks at similar depths, I dive a
25/30/45 trimix, with an AL40 of 50/50 for deco. That gives you 30
minutes at 150 with a 25-30 minute hang and only a single gas switch to
manage. Max PO2 on bottom is 1.385; END is 71 feet - conservative even
taking the potential narcotic effects of oxygen into account.
Kevin, a 25% O2 would suffice seeing how the bottom is at 150', but I will
almost always opt for running something closer to a 1.3 pp of O2 or lower when
factors such as cold water and current come in to play. So I would probably run
a 23% O2 max. and 20% He.(100' END). This would seem to be the acceptable
standard among the well advised!
For shallow trimix, use 1.4PPO2 MOD, and 90FSW END.
For deep, 1.3 / 100-120FSW END
Then again, if there was insufficient time between dives to remix then you
could use a 25/30 mix for the first dive and air top to get something like a
22/10 which should be fine for the second dive. I would see if I could
borrow a small deco cylinder (AKA a small horse - don't want to get into
that debate) with 100% for deco.
I'd opt for something like 21/25 Mix. Personally, I'd probably go for
even more Helium (30-35%). I hate being narced. I've dove the Moody a
bunch of times, but always on air or EAN, too. Haven't done her on Mix,
yet.
You talking about the MOODY? If so, keep your EAD to 80 to 100fsw and you be
amazed at how much more you'll see.
"Don't forget your history,
Know your destiny,
In the abundance of water,
The fool is thirsty."
Robert Nesta Marley
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^^^^^^^^^^^^^^^^^^^^^^
o o
o o
o o
_____ o o
(_/\_) o o o
=( )= oo
Kevin Rottner
Southern California SCUBA
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