+ Reply to Thread
Results 1 to 6 of 6

Thread: Had a go. Now some questions.

  1. #1
    RBW Member Paul S is on a distinguished road Paul S is on a distinguished road Paul S's Avatar
    Join Date
    Sep 2008
    Location
    UK, Twickenham
    Posts
    147
    rEvo III Mini hCCR

    Had a go. Now some questions.

    Hi All,

    Last week I had my first go on a rebreather. An Inspo classic that an instructor friend of mine owns, and he kindly let me have a go in the pool, walking me through everything first... striping the unit down... putting it all back and doing all the pre-dive checks. No real surprises with any of that. I've lurked on here long enough to pick up the basics. Only real issue was that the unit was really rigged for someone smaller than me, as I'm 6'5" (195cm) and he..... isn't.

    Pre-breathing the unit I noticed that the cell reading fluctuated between about 0.5 as I breathed in and 0.75 as I breathed out (set point 0.7). Is this normal? I was surprised by this. I expected it to be steadier.

    Once in the water I found the unit reasonably comfortable. More resistance to breathing in than I expected, but I guess I'm drawing air through the scrubber. Thing I found difficult was, surprise surprise, buoyancy. Some of it was me. I had all those moments of realising I couldn't use my lungs for buoyancy. Sometimes I'd breath really deep and just bottom out the lungs and make the ADV fire which would knock me off.

    Sometimes though I felt like I was having to dump gas to compensate for the O2 injection. I'd get myself set up, minimum loop volume, trimmed out on the wing, and swim around a bit just off the bottom (about 3m - 10ft). Then the O2 solenoid would fire (about a 3-5 second burst every minute or so). I'd feel the lungs inflate, and I'd be heading upwards. Looking at the ppO2, it was still doing a similar sort of 0.5 -> 0.75 dance in time with my breathing as it had been on the pre-breath.

    So, was I fighting a machine doing funny things or does that sound normal and I was just being too stuck in my OC ways? I only had 20-25 minutes so I'm quite prepared to believe I was being an OC numpty.

    Basically I wanted to give it a go so that when I go do try-dives on other units I've got a base line to compare against. I just want to make sure that my base line was normal.

    Thanks

    Paul

  2. #2
    RBW Member ashsg will become famous soon enough ashsg will become famous soon enough ashsg will become famous soon enough ashsg's Avatar
    Join Date
    Apr 2010
    Location
    Bolton-UK
    Posts
    249
    Inspiration Classic

    Re: Had a go. Now some questions.

    Quote Originally Posted by Paul S  View Original Post
    Hi All,

    Last week I had my first go on a rebreather. An Inspo classic that an instructor friend of mine owns, and he kindly let me have a go in the pool, walking me through everything first... striping the unit down... putting it all back and doing all the pre-dive checks. No real surprises with any of that. I've lurked on here long enough to pick up the basics. Only real issue was that the unit was really rigged for someone smaller than me, as I'm 6'5" (195cm) and he..... isn't.

    Pre-breathing the unit I noticed that the cell reading fluctuated between about 0.5 as I breathed in and 0.75 as I breathed out (set point 0.7). Is this normal? I was surprised by this. I expected it to be steadier.

    Once in the water I found the unit reasonably comfortable. More resistance to breathing in than I expected, but I guess I'm drawing air through the scrubber. Thing I found difficult was, surprise surprise, buoyancy. Some of it was me. I had all those moments of realising I couldn't use my lungs for buoyancy. Sometimes I'd breath really deep and just bottom out the lungs and make the ADV fire which would knock me off.

    Sometimes though I felt like I was having to dump gas to compensate for the O2 injection. I'd get myself set up, minimum loop volume, trimmed out on the wing, and swim around a bit just off the bottom (about 3m - 10ft). Then the O2 solenoid would fire (about a 3-5 second burst every minute or so). I'd feel the lungs inflate, and I'd be heading upwards. Looking at the ppO2, it was still doing a similar sort of 0.5 -> 0.75 dance in time with my breathing as it had been on the pre-breath.

    So, was I fighting a machine doing funny things or does that sound normal and I was just being too stuck in my OC ways? I only had 20-25 minutes so I'm quite prepared to believe I was being an OC numpty.

    Basically I wanted to give it a go so that when I go do try-dives on other units I've got a base line to compare against. I just want to make sure that my base line was normal.

    Thanks

    Paul

    Bouyancy will come i had a love/hate with my classic through bouyancy now i love it. Did you ask your instructor on the cell issue?? Mine has never done this maybe dying cells. As for the ADV i decided to dive without one i just prefer it that way. As for WOB i find it easier on CCR than on OC, maybe your stack/scrubber was packed way to tight. Best off having a word with the instructor really.

    Ash

  3. #3
    Hammermeg, Copis2, Kiss divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe is just really nice divingabe's Avatar
    Join Date
    Oct 2005
    Location
    Lake City,FL
    Posts
    654
    Meg 2.7, Hammermeg, copis meg

    Kiss Sport, Draeger dolphin

    Re: Had a go. Now some questions.

    Way too shallow in a pool for buoyancy comfort. WOB difficulty may have been from not having the counterlungs properly adjusted. Cell reading sounds like a faulty cell. In the future in a try dive in a pool use the unit as an oxygen only rebreather it will help with the buoyancy issue by limiting the solenoid firing, just fill the loop with pure o2 put set point on .7 run minimal loop volume and manually add o2 when increased volume is neede in the loop.
    Gabe

  4. #4
    Mostly cold ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown has a reputation beyond repute ChrisBrown's Avatar
    Join Date
    Jan 2008
    Location
    England
    Posts
    1,742
    Evo+, Pos MKVI, Sentinel

    rEvo II & III Minis & Micros

    Re: Had a go. Now some questions.

    Hi Paul, glad you had a go. See below.

    Quote Originally Posted by Paul S  View Original Post

    Pre-breathing the unit I noticed that the cell reading fluctuated between about 0.5 as I breathed in and 0.75 as I breathed out (set point 0.7). Is this normal? I was surprised by this. I expected it to be steadier.
    Yes. The electronics give more info more often than many other units. This means you will always see the cell readings moving. This is deliberate and a great feature. It helps you spot current limited cells and shows you how fast they are responding

    Quote Originally Posted by Paul S  View Original Post
    Once in the water I found the unit reasonably comfortable. More resistance to breathing in than I expected, but I guess I'm drawing air through the scrubber.
    No, nothing to do with the scrubber. You had too much loop volume, which is quite normal for a first go. Everytime you exhale, you drop the P02 below set point and the solenoid is constantly firing to try to bring it back up. Once you get too much gas in the loop, its not very efficient (as its like putting a teaspoon of rum in a quart of coke )

    Your friend should have explained this and got you to dump all the loop volume before descending and perhaps even reduced the setpoint to .5 and got you at around .7 before you descended.

    Quote Originally Posted by Paul S  View Original Post
    Thing I found difficult was, surprise surprise, buoyancy. Some of it was me. I had all those moments of realising I couldn't use my lungs for buoyancy. Sometimes I'd breath really deep and just bottom out the lungs and make the ADV fire which would knock me off.

    Sometimes though I felt like I was having to dump gas to compensate for the O2 injection. I'd get myself set up, minimum loop volume, trimmed out on the wing, and swim around a bit just off the bottom (about 3m - 10ft). Then the O2 solenoid would fire (about a 3-5 second burst every minute or so). I'd feel the lungs inflate, and I'd be heading upwards. Looking at the ppO2, it was still doing a similar sort of 0.5 -> 0.75 dance in time with my breathing as it had been on the pre-breath.

    So, was I fighting a machine doing funny things or does that sound normal and I was just being too stuck in my OC ways? I only had 20-25 minutes so I'm quite prepared to believe I was being an OC numpty.

    Basically I wanted to give it a go so that when I go do try-dives on other units I've got a base line to compare against. I just want to make sure that my base line was normal.

    Thanks

    Paul
    Yes, all normal :) Rebreathers SUCK big time in a pool. A total waste of time unless you can get over 4m of depth in my opinion.

    Its not until you are over 60fsw/20m ish that you can even start to see the real benefits of them.

    Diving CCR's deep is easy. The real art is on ascent and shallow in particular, where you are offgassing into the loop, have the solenoid firing all at the same time as managing an expanding loop, wing and drysuit :)

  5. #5
    RBW Member Paul S is on a distinguished road Paul S is on a distinguished road Paul S's Avatar
    Join Date
    Sep 2008
    Location
    UK, Twickenham
    Posts
    147
    rEvo III Mini hCCR

    Re: Had a go. Now some questions.

    Thanks everyone. That all makes sense, and there's a few little nuggets of useful information in there. Sounds like it's all natural things that just take time to get used to.

  6. #6
    Plays with High Voltage trident00 has a spectacular aura about trident00 has a spectacular aura about trident00 has a spectacular aura about trident00 has a spectacular aura about trident00 has a spectacular aura about trident00 has a spectacular aura about trident00's Avatar
    Join Date
    May 2011
    Posts
    93
    KISS classic

    Re: Had a go. Now some questions.

    It takes time as you said. Everything you throw on top of it takes time to adjust to as well. As was mentioned it can become a bit of a juggling act when you throw on a drysuit, bail out, lights, etc.

    It is just something you have to commit to and understand that there will be a learning curve. When I started it took me a bit to get used to being on the loop. I think that many just kinda forget that adjustment period and after it all becomes second nature its easily forgotten.

    Best wishes, Walt

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts