For several years, I've been trying to get to one of the rebreather "try dive" days that are occasionally organized in our area, and I've never been able to make one. So, when I found out Leon Scamahorn was going to be doing a weekend of education and experience with the new ISC Pathfinder, I jumped on the opportunity, and today was the day.
It was a great experience. We met at 9am, and spend the first three hours in lecture. We heard about the history of Leon and of ISC, and about what makes the ISC rebreathers different. (Leon is very proud of the third party testing he's had done on his units, as I think he probably ought to be.) We talked about his vision of what a rebreather ought to be able to do (lots of "R's" -- redundant, robust (I kept thinking of JJ), reliable, and so on). We talked about the actual design of the units, and how the Meg is different from the Pathfinder (which is his electronic unit), and I got to ask questions about rebreather design and work of breathing, and about scrubber design and why temperature and depth make a difference in scrubber duration, neither of which made sense to me. I mean, if cold makes the reaction go slower, the scrubber ought to last LONGER, right? (No.) Leon was very patient with my questions, as were the rest of the participants, none of whom asked anywhere near as many as I did, perhaps because nobody else could get a word in edgewise.
We got a brief introduction to how one dives one of these things, all of which will bore the daylights of out the rebreather people on this forum, but most of which was new to us. (I had done a 15 minute dive on an MC90 in the Red Sea, so not all of it was new.) Leon prioritizes the tasks of diving the unit as 1) manage your ppO2; 2) set the loop volume, and 3) adjust buoyancy with BC or suit. But the Pathfinder wasn't set up with diluent (just O2) so we didn't have a BC per se, and all of us were diving wetsuits, so buoyancy in some cases just wasn't even possible. I was weighted enough to get underwater, which made me very negative at the bottom (5 mil suit), so I spent a lot of time discreetly pushing myself up off the bottom, and remembering my OW class.
The Pathfinder is kind of amazing. With just one 6 cf bottle on the back, the whole thing weighs less than 35 pounds. It doesn't really even feel like gear. I knew it would be silent, which it was, but the work of breathing was fabulous -- I don't think my MK25/S600s are any better. To my surprise (even though Leon had told us this) the WOB was the same in just about every position. It was fun to roll over on my back and have it just as easy to breathe as it was before. Normally, one would have a bailout bottle attached on the left side, which we didn't, which I think would have balanced the whole unit out beautifully.
Running a rebreather in 13 feet of water is a complete mind trip for someone who has completely internalized open circuit buoyancy control. NOTHING works the same. Since loop volume doesn't change with inspiration, that deep breath one instinctively takes when sinking accomplishes nothing. Worse, if you fail to add gas to the loop, you suddenly discover you are not only sinking, you are OUT OF GAS!!! Of course, you aren't, you've just bottomed out the loop volume, and a quick push of the O2 addition button fixes the issue, but it's unnerving. Even stranger, when you ascend, you have to ADD gas to the loop, which is of course expanding as well, and if you don't want chipmunk cheeks and a quick trip to the surface, you have to breathe all that extra gas out your nose. I don't know about you, but I don't BREATHE through my nose on scuba; I was actually rather thoroughly schooled NOT to do that, and it felt extremely strange, not to mention making my mask feel rather insecure and fog like crazy.
I was actually rather pleased at how quickly I managed to figure out how the loop ought to feel when it had the "right" amount of gas in it, and I was also pleased that I never heard the solenoid fire (which would have been an indication that I had not kept my attention on the ppO2). I did NOT like the fact that I could not read the handset well at all (I'm totally OLED spoiled), but the heads-up display would have fixed that. (That's what I used when I did this before.)
Overall, it was a wonderful way to spend a day. I learned a lot, and Leon was very patient. It was exciting and fun to do something totally different with diving, as well, and to get to be a beginner again. I'm not ready to pull out my checkbook, but I'm glad I did this.
It was a great experience. We met at 9am, and spend the first three hours in lecture. We heard about the history of Leon and of ISC, and about what makes the ISC rebreathers different. (Leon is very proud of the third party testing he's had done on his units, as I think he probably ought to be.) We talked about his vision of what a rebreather ought to be able to do (lots of "R's" -- redundant, robust (I kept thinking of JJ), reliable, and so on). We talked about the actual design of the units, and how the Meg is different from the Pathfinder (which is his electronic unit), and I got to ask questions about rebreather design and work of breathing, and about scrubber design and why temperature and depth make a difference in scrubber duration, neither of which made sense to me. I mean, if cold makes the reaction go slower, the scrubber ought to last LONGER, right? (No.) Leon was very patient with my questions, as were the rest of the participants, none of whom asked anywhere near as many as I did, perhaps because nobody else could get a word in edgewise.
We got a brief introduction to how one dives one of these things, all of which will bore the daylights of out the rebreather people on this forum, but most of which was new to us. (I had done a 15 minute dive on an MC90 in the Red Sea, so not all of it was new.) Leon prioritizes the tasks of diving the unit as 1) manage your ppO2; 2) set the loop volume, and 3) adjust buoyancy with BC or suit. But the Pathfinder wasn't set up with diluent (just O2) so we didn't have a BC per se, and all of us were diving wetsuits, so buoyancy in some cases just wasn't even possible. I was weighted enough to get underwater, which made me very negative at the bottom (5 mil suit), so I spent a lot of time discreetly pushing myself up off the bottom, and remembering my OW class.
The Pathfinder is kind of amazing. With just one 6 cf bottle on the back, the whole thing weighs less than 35 pounds. It doesn't really even feel like gear. I knew it would be silent, which it was, but the work of breathing was fabulous -- I don't think my MK25/S600s are any better. To my surprise (even though Leon had told us this) the WOB was the same in just about every position. It was fun to roll over on my back and have it just as easy to breathe as it was before. Normally, one would have a bailout bottle attached on the left side, which we didn't, which I think would have balanced the whole unit out beautifully.
Running a rebreather in 13 feet of water is a complete mind trip for someone who has completely internalized open circuit buoyancy control. NOTHING works the same. Since loop volume doesn't change with inspiration, that deep breath one instinctively takes when sinking accomplishes nothing. Worse, if you fail to add gas to the loop, you suddenly discover you are not only sinking, you are OUT OF GAS!!! Of course, you aren't, you've just bottomed out the loop volume, and a quick push of the O2 addition button fixes the issue, but it's unnerving. Even stranger, when you ascend, you have to ADD gas to the loop, which is of course expanding as well, and if you don't want chipmunk cheeks and a quick trip to the surface, you have to breathe all that extra gas out your nose. I don't know about you, but I don't BREATHE through my nose on scuba; I was actually rather thoroughly schooled NOT to do that, and it felt extremely strange, not to mention making my mask feel rather insecure and fog like crazy.
I was actually rather pleased at how quickly I managed to figure out how the loop ought to feel when it had the "right" amount of gas in it, and I was also pleased that I never heard the solenoid fire (which would have been an indication that I had not kept my attention on the ppO2). I did NOT like the fact that I could not read the handset well at all (I'm totally OLED spoiled), but the heads-up display would have fixed that. (That's what I used when I did this before.)
Overall, it was a wonderful way to spend a day. I learned a lot, and Leon was very patient. It was exciting and fun to do something totally different with diving, as well, and to get to be a beginner again. I'm not ready to pull out my checkbook, but I'm glad I did this.
