Quote: (Originally Posted by
Mark Chase)
However total loss of inboard diluent will mean total loss of wing inflation gas. Not much of a problem open water but in a cave it could be. So the choice now is to run the buoyancy off the dry suit (not my first choice) or to disconnect the dry suit and swap the feed to the wing inflate.
Why not run your wing from offboard? My BOV and wing run from the manifold with a QD to my offboard. It uses a minimal amount of gas when you get used to balancing it with your suit.
I calculate bailout on fill pressure -30bar so I've got a lot of padding in there. OK bailout is another thing to monitor but I like my dil just to feed the the loop and that's it.
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With 02 we ran thirds all the time which is both sensible and easy to do. With the average metabolic rate of 1-1.2 a 3ltr will last eight hours +. So only on caves with loads of ups and downs are we going to need to worry about 02. that said a leek can spoil any dive so Id personally have a means of injecting 02 from a redundant supply.
I don't have a gauge on my O2. Any hint of a problem and it's home time. If there's no problem then the O2 will last longer than I want to be in the water (or my scrubber).
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When open water diving on the Inspo I had my 50% deco mix with a hose on it I could plumb into the counter lung. On my KISS I use a 0.75ltr bottle plumbed into my kiss for manual injection but switched off till I needed it.
So bailout plus 0.75l bottle plus suit bottle plus onboard plus Rebreather... Wouldn't OC be a hell of a lot simpler?
As I've said before, my two tests are: if OC means less cylinders and/or OC is cheaper then I go OC for cave diving.
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Bailout gas is planned on 100% needed to exit the cave so no thirds. Safety margins were in place via increased SAC calculations and slow and easy progression into the cave.
That's "roughly" how I plan mine. Only I take an extra of whatever my deepest bottle is. So if I need 1x12 to exit then I take two. If I need two then I take three. I have serious doubts over the survivability of a CO2 hit in a cave. I also tow a scooter if I'm 30m+ with any distance so perhaps I'm just paranoid.
For turnpoint I go for 1/3 off dil (I don't put a gauge on my O2) unless I've hit a predetermined point (if it's a cave I know) or time (if it's a cave I don't). Even if I've got plenty of dil/bailout/whatever, I turn if I hit that point. I find cave diving CCR a lot more restrictive than OC, if I want to just get in and swim and have a mooch then I far prefer OC.