Hi guys,
It seems like as soon as I get one annoying question answered, another pops out of nowhere!
So I'm trying to figure out what the best way is to optimize my loop volume on my backplated-Dolphin. I can adjust how far the backplate stands off from the Drager shell - the backplate adapter slides back and forth. The original guy who sold it to me was a rather large/tall fellow, and he had it set for almost maximal expansion. This gave me a serious case of chipmunk cheeks when I lay on my back in the pool, as the CLs are further away from my lungs, and also probably contributed to buoyancy issues.
Yesterday, I adjusted the backplate adapter to be much closer to the shell, to restrict the volume of the CLs. I then set everything up (on land), without attaching any Nitrox supply (so the auto addition valve isn't working).
Here is my question: How do I know that the CLs aren't TOO restricted? I tried to answer this question by doing the following...
First I tried to find the minimal loop volume as defined by Rich Pyle's FAQ, i.e. I sucked the CL's down as empty as I could, then exhaled all the air in my lungs through the nose.
Keeping the system at min loop volume, I took in a full complete breath through my nose. I then let this breath into the loop through my mouth. Then keeping the loop at constant volume (no more nose breathing), I tried to see if I could activate the exhaust valve on the Dolphin by exhaling as hard as I could.... the answer was no, not unless I took in some more air through the nose.
I -assume- that this indicates that I am at optimal loop volume, i.e. CL's are almost close to flat when I fully inhale. I'm not sure how the constant mass flow properties of the Dolphin system will change this, as I didn't test it with the flow on.
Any ideas, obvious flaws, or better ways to find optimal loop volume on a Dolphin?
Thanks so much and sorry for the long post. Hopefully this might be useful!
Yeang