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> Having just done an intro course to the Prism, I know what you mean about > back pressure! I found at first, I was swimming around with cheeks puffed > out like a chipmunk! It seems the positioning of the breathing bag is fairly > critical in reducing this effect. > > As we were only using it in a swimming pool, it was rather shallow. Do you > find this effect is independent of depth or less noticable down deeper ? > I found it significantly less comfortable to use than open circuit because of > this effect. How do you find the rebreather compared to open circuit now that > you have a significant number of hours on it ? The effect is independant of depth (i.e., it's the same in deep water as in shallow water). I actually don't notice any difference in this back pressure according to my body orientation; only on the loop volume. The counterlungs on the Cis-Lunar are relatively large, so there the diver has good range of back-pressure intensity to play with. The "chipmunk" effect only happens to me as I am ascending and the loop volume is expanding. Once you know how to vent the excess gas volume on ascent, it's not really a problem at all. Also, I maintain different back-pressures depending on whether or not I am using a FFM (I keep the back-pressure slightly higher with a FFM to help minimize water leakage into the mask). During my first few hours on the rig, I found it somewhat less comfortable than SCUBA mainly because it took me a while to master proper loop volume control and bouyancy control (you never realize just *how much* you rely on your breathing for bouyancy trim until you dive with a rebreather). Bouynancy control *IS* affected by depth: it takes more effort to maintain neutral bouyancy if your going up and down from 20 feet to 5 feet than it does if your going from 75 feet to 60 feet. After about 5 hours or so, I got the hang of it and now find that rebreather diving is MUCH more comfortable than SCUBA diving. I'm an adict now, and the few times I've gone back to SCUBA make me appreciate the rebreather all the more. Aloha, Rich ******************************************************************* Richard Pyle deepreef@bi*.bi*.ha*.or* "WHATEVER happens to you when you willingly go underwater is COMPLETELY and ENTIRELY your own responsibility! If you cannot accept this responsibility, stay out of the water!" *******************************************************************
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