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IPO and back mounted counter lungs

Discussion in 'Rebreather Diving' started by Gareth J, Apr 23, 2019.

  1. JohnnyC

    JohnnyC Divemaster

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    I can't believe he's still allowed here. Between the shilling and attempts to sell his crap in every thread, to the outright lies he pushes to try and do so, I can't for the life of me figure out why he's allowed to stick around.
     
    rjack321 likes this.
  2. wedivebc

    wedivebc CCR Instructor ScubaBoard Supporter

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    I am all for free speech. As long as there are experienced rebreather divers who can expose the snake oil salesmen.
     
  3. silent running

    silent running Manta Ray

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    Hi Brad, yes the NEDU did test the Prism WOB, I don’t remember what it was, maybe 1.6? It was one of the lower figures, there’s a chart somewhere in an old RBW thread.

    And yes, an analog secondary, high output sensors with a modern HUD would be my most preferred design. And if you also could switch from solenoid to needle valve CMF addition for sawtooth/cave type profiles, that would be ideal...

    Thanks for all the links and graphs, but it’s a bit hard to sift through all that information to find an explanation for how BMCLs can overcome the hydrostatic head experienced with near horizontal or worse, head down/descending trim. Can you explain in laymen’s terms how this is achieved? Even with BMCLs as close to the back as possible, the diver’s lungs are still closer to the front of the chest than the back. I just don’t see how with all other design elements being equal, OTS would not breathe better given the hydrostatic head encountered in most common swim positions...
     
  4. rjack321

    rjack321 Captain

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    At least some BMCLs "wrap around" the lower back onto the sides so part of the lung volume is at the same depth as the diver's lungs when in flat trim at least.
     
  5. silent running

    silent running Manta Ray

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    Which CCR(s) are you referring to?

    While that may be an improvement, aren’t the lungs higher up in the chest cavity as well as being closer to the front of the chest? Wouldn’t wrapping the lungs around higher up than the lower back, under the arms, bring them even closer to the lungs?
     
  6. JohnnyC

    JohnnyC Divemaster

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    The Mk1 Pelagian lungs are essentially “side-mounted” counterlungs that most closely match the lung centroid of the diver in virtually all positions except sideways.

    However, they are, for most people, unacceptably intrusive as the clutter up both the front, and sides of the diver in places where we need to be trim and unobtrusive. They literally obstruct every d-ring except the butt and scooter rings. Hence why most Pelagian divers have switched to BMCL’s.
     
  7. silent running

    silent running Manta Ray

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    Thanks JohhnyC, I’m familiar with the Pelagian CLs, very sensible design aside from the D ring issues you mentioned. But it sounded like rjack was speaking of another CCR with the lungs placed mostly on the back?
     
  8. rjack321

    rjack321 Captain

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    The kiss sidewinder lung (single) wraps across the small of my back and extends down each side by my kidney about 4-6"
    The kiss orca and spirit lte CLs both do the same (those units have 2 CLs)

    At least in the sidewinder's case you couldn't have the lungs higher as the neck bungies from sidemounted bailout would compress them. The WOB from the wrap around CL is fabulous in trim, it does get kind of crappy if you go head up or head down because your lungs and entire diaphragm end up above or below the CL. Its not impossible to breathe and the unit is still divable in a vertical position - but it does take a lot of work. I had to go vertical in a cave I was diving a couple weeks ago and my lungs vented (via my nose & mouth) and all my suit gas dumped and I was not a happy camper as the water was 41F (5C). Worst part was the cave ended and it was all for naught.
     
  9. silent running

    silent running Manta Ray

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    Thanks for the detailed info. Are you using the Sidewinder as a BO CCR?
     
  10. rjack321

    rjack321 Captain

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    I know a few people are. I use a Meg with "top of shoulder" CLs for wreck dives. The sidewinder is for cave dives. 95% of my dives are 10-220ft, maybe 5% are deeper than 220ft and my max is around 305ft. I use al80s in open water and lp85s or hp130s in cave for OC bailout. I don't see a need for a BO CCR in my diving in the foreseeable future. Right now on both units combined I think I have 225-240hrs, mostly in cold to very cold water.
     

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