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Thread: Another Co2 story... and pondering a BOV.

  1. #11
    RBW Member Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by silent running  View Original Post
    Hi Mike, I tried on a the Nova FFM and it felt like it was sticking out a mile in front of me. While I'm sure you're right about the FFM staying in place, it just seems so much bulkier than a DSV and low profile mask.
    yes its a tad bigger but any and all drag is taken by the mask straps and full face seal so you dont feel any fatigue at all - certainly far less than a normal dsv and hoses in strong current where all the load is taken by the mouth - and far more secure.

    Did you have trouble getting used to the Nova? Does it pull a lot when turning into or away from current, enough say to make hanging on to something with one hand significantly harder?
    nope not in the slightest. In strong current dives the most id do is tighten the straps harder than normal - normally their gentle. pre ffm i would have to use one hand to hold the dsv in my mouth to stop it getting ripped out - or bite hard on the mouthbite (which as mentioned is not a good idea) with the mask my neck muscles take the load and i can concentrate on my tasks with no change in wob and reduced stress. I have once had the mask flood in strong current which wasnt nice but as it has an internal mouthbite it didnt flood the loop and as its a ffm i wasnt at risk of losing the mask completely. I just closed my eyes until i could turn out the current adjust the straps (they were too lose) and purge


    Good point about the teeth clenching scenario, never thought about that before. This is another reason I'm glad I have a Mantabite as it keeps the mouth pc. in place with minimal effort and my mouth open wide.
    this is why good Rebreather mnf supply units with big (thick) mouthbites and why the people who remove the thick apd one and replace it with something far thinner and more comfortable are not doing themselves much favors.

    Hadn't thought about the positive pressure making WOB, at least the inhale, easier. Could indeed make a difference in a crisis.
    the difference is quite amazing
    Last edited by Drmike; 8th July 2008 at 10:26.

  2. #12
    RBW Member Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike has a reputation beyond repute Drmike's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by Gill Envy  View Original Post
    thanks Mike, great feedback! how do you keep the current from crushing the counter lungs.
    easy - dive a bmcl unit :D

    FWIW On my homebuilds ive found the wob of the lung differs hugely if i put it in a hard case (a la back mounted rbs) or inside a flexible cover (a la inspo) as with the cover there you have to move it to breath - extra work (wob) with the hard case you dont have anything to move. Guess its the same with hysteresis in meg cl material (or inspo) or when breathing with ots cls in strong currents.

    I failed to mention that just before this happened I was sitting right next to her when the current first started to gust, I was holding on with both hands and the pressure of the current against my chest emptied the counter lungs out my mask.
    at times like this i think about taking up golf:D
    Last edited by Drmike; 8th July 2008 at 10:35.

  3. #13
    RBW Member blue_dubai is an unknown quantity at this point blue_dubai's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    To BOV or not to BOV ... I used a Poseidon regulator on a divematics BOV



    Hi Peter,

    i was wondering which Poseidon second stage do you use?
    I have a cyclon 5000 and wonder if it makes sense to use it for a BOV.

    Thanks,

    Mehdi-Saman

  4. #14
    Submerge Productions PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver is a splendid one to behold PCDiver's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by blue_dubai  View Original Post
    i was wondering which Poseidon second stage do you use?
    I'm currently using an Xtreme.

  5. #15
    Underwater Journal Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns is a name known to all Walt Stearns's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    I just replaced the Paragon on my Sport KISS with a Aqualung Mikron. Breathes really nice now, plus it's still small and light like it was before.

    Walt Stearns
    Editor-in-Chief
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    Last edited by Walt Stearns; 15th December 2008 at 13:46.

  6. #16
    Mature mouth breather silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by Gill Envy  View Original Post
    My wife chose to hold on with both hands trying to figure out where to find shelter, she should have let go and drifted and swam along the wall but could not see anything but flat exposed areas...she wasn't sure what to do. then a blast of current beared down on her so strong it ripped her DSV right out, out went the gas from the loop, into the loop went some salt water, back in the mouth went the DSV on bottomed out C-lungs, current so strong the CL's were collapsed and wouldn't hold anything and the schrader style ADV just was not keeping up with her inhales.

    Hi GE, glad you finally got around to posting this story. I still don't quite understand how her CLs collapsed to the point they were unable to breathe off of. Is it possible that her feeling of not having enough air was because of CO2 retention, rather than the loop not having enough volume?

    Even after many, many instances of heavy current hitting me directly in the chest while clinging to something, I've never felt the CL volume decrease to the point where I had trouble getting a full breath. The Meg CLs are longer than the Prism and have T-pcs that sit on top of the shoulder. This makes me wonder if the Prism having the DSV hoses mounted lower on the CLs and head hoses mounted on top of the shorter Prism CLs, spreads out the lung volume more, instead of having all the gas in a low loop volume scenario concentrated around a T-pc.

    Has anyone else had a OTS CL flatten out to the point where it they couldn't breathe and the ADV wouldn't flow enough to bring the CLs back to shape?


    Quote Originally Posted by Gill Envy  View Original Post
    this has made me think about a BOV a lot harder since it was obvious that there was nothing she could do to successfully get off the loop once caught in the downward spiral. so why haven't I run out and gotten a BOV? I have to admit that the added profile and drag has it's risk benefit equation and while i'm closer to going for one, i'm not quite convinced it's the right thing for me and i'm also hoping that someone will come out with a better design. Even in the above scenario the current was so strong it would have been free flowing and impractical for such diving. I came to the conclusion a while back that one should BO long before they think they need to and now I realize that in some rare cases there is no warning, as Dave S so well illustrated in his post. I understand and choose to take this risk for now, but that may just be a matter of time. If there was one with a very low profile that pressurized as it was switched on so it didn't free flow in current but also did not require turning on a flow stop in addition to switching on, I would be more likely to add it to the wish list, as I more graphically see it's value. For now, it's just one more area where I pad the equation that much more and do my best to avoid getting in such a situation in the first place.

    Remember my experience with the Divematics BOV in Ambon last year? You kept saying how bulky it looked. I realized after having it on the rig for 2 days that even a reasonably small BOV, with a bottom mounted 2nd stage is too much bulk in heavy, turbulent current. But I don't think that free flow would likely ever be a problem, even in heavy head on current-as long as the BOV 2nd stage is on the bottom of the barrel. I only experienced free flow in OC mode at the surface. And remember that a BOV 2nd stage needs to be pressurized during the dive in order to keep the diaphram from collapsing as you descend. So, you will always need to have the gas on and some way to counter a free-flow of a BOV. You can install a flowstop and dive with it on, but I don't like the idea of adding more bulk and stiffness to a BOV setup than there already is. That's why I have a shut-off in the form of a ball valve on my offboard whip which would feed my BOV, instead of having a slider/flowstop inline, next to the BOV.

    After all my research and experience with the Divematics BOV and reading more of Mike's comments, now I'm back to the Nova FFM with a standard DSV and sidemounted reg-most compact, most flexible, most comfortable, most safe and no WOB compromise in either CC or OC. Not happy about the expense and the visual distortion in the plastic lens sides and what felt like a slightly narrower field of usable vision than a low volume mask, but I can deal...
    Last edited by silent running; 8th July 2008 at 16:23.

  7. #17
    Mature mouth breather silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running has a reputation beyond repute silent running's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by Drmike  View Original Post
    In strong current dives the most id do is tighten the straps harder than normal - normally their gentle. pre ffm i would have to use one hand to hold the dsv in my mouth to stop it getting ripped out - or bite hard on the mouthbite (which as mentioned is not a good idea) with the mask my neck muscles take the load and i can concentrate on my tasks with no change in wob and reduced stress.

    Thanks for all the details Mike. Makes sense that by transferring the load from the mouth/jaw to the neck, you'd be gaining comfort and reducing stress. Not a bad trade off for a bit more bulk and then we have all the increased safety and ease of access to OC gas. Guess I'm out another $1500, ugh!

    BTW, what do you and others do with an FFM on the surface while waiting a few minutes for the tender? Would you take it off completely and let it hang off the loop in the water? Or disconnect the DSV and put the FFM on top of your head?

  8. #18
    RBW Member sailordiver@msn.com is on a distinguished road sailordiver@msn.com is on a distinguished road sailordiver@msn.com's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Gill,
    Thanks for the thorough and harrowing account of your wife's near disaster. What liveaboard were you on in Indo that caters to RB divers?

  9. #19
    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    We were not diving a liveaboard. Andy has a fairly successful way of looking around for the undiscovered and remote dive spots that are still pretty healthy and finding an operator that can source o2, and from there, as Andy puts it, everything else can be worked around.

    Diving in Alor was the third dive operation we've dove together as a group who had never catered to rebreather divers. I really should do up a trip report as these kind of trips can be quite amazing but have some pitfalls to watch out for. For me, half the reason I love rebreather diving so much is that on such trips the operators can not keep up, so they just let you do your own thing and make your own choices... the downside to that is that it is really tricky to dive in a place you've never been before with little useful guidance and an operator that doesn't understand your limits. I found the dive briefings pretty useless as our profiles had us doing totally different, virgin dives on nearly every splash... but wow, at the same time it's hard to complain about that!

    g



    Quote Originally Posted by sailordiver@msn.com  View Original Post
    Gill,
    Thanks for the thorough and harrowing account of your wife's near disaster. What liveaboard were you on in Indo that caters to Rebreather divers?

    Gill Envy

  10. #20
    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Re: Another Co2 story... and pondering a BOV.

    Quote Originally Posted by silent running  View Original Post
    Hi GE, glad you finally got around to posting this story. I still don't quite understand how her CLs collapsed to the point they were unable to breathe off of. Is it possible that her feeling of not having enough air was because of CO2 retention, rather than the loop not having enough volume?
    hello Andy! The crazy thing with this sport is that you can get really far along in a variety of skill sets and still be at square one when faced with a new situation. Elizabeth and I are very experienced current divers... we are very good at planning dives so we have the least amount of current! When the current starts to rip, we are accustom to getting the hell out of the water. Where we live, big current doesn't equal big fish action so there is just no need to subject yourself to it. Deliberately diving in heavy current is a new thing for us, something you are much more accustom to and skilled in. she and I had no business hanging on in such intense current, and I doubt that will ever happen again. When my lungs callapsed I realized quickly what was happening, something like this had happened before to me. In this case I was becoming a kite in a heavy wind as I held on with both hands with the current nearly perpendicular to my chest at the crest of a ridge. I quickly let go and turned around and refilled my lungs with the right proportions of o2 and dill and then turned around to see where she was at and the same thing was happening to her, she'd just never had that combination of things happen before and didn't react quickly enough.

    Quote Originally Posted by silent running  View Original Post
    Even after many, many instances of heavy current hitting me directly in the chest while clinging to something, I've never felt the CL volume decrease to the point where I had trouble getting a full breath. The Meg CLs are longer than the Prism and have T-pcs that sit on top of the shoulder. This makes me wonder if the Prism having the DSV hoses mounted lower on the CLs and head hoses mounted on top of the shorter Prism CLs, spreads out the lung volume more, instead of having all the gas in a low loop volume scenario concentrated around a T-pc.

    Has anyone else had a OTS CL flatten out to the point where it they couldn't breathe and the ADV wouldn't flow enough to bring the CLs back to shape?
    Perhaps there is a design difference in the Prism which helps prevent this or perhaps our rigs just fit us differently because we are tall. All in all, with your diving in Comodo and other current swept places you certainly have more heavy current exeperience and i'm guessing simply getting comfortable and knowing what to do goes a long way to steering clear of sticky situations. As for the Meg's style of ADV, it is not a regulator, so it requires that the plunger be alligned to automatically give you air. I used to really be leery of this but I've gotten used to it for the most part and would not trade it's reliability and simplicity for anything. If i'm not getting the air I need I just give it a tap...admittedly harder to do when holding on with both hands. speaking of manual adding, you would have thought these scenarios would have prevented us from staying "in the zone" with our po2 and manual o2 addition, but the required add intervals were never an issue.


    Quote Originally Posted by silent running  View Original Post
    Remember my experience with the Divematics BOV in Ambon last year? You kept saying how bulky it looked. I realized after having it on the rig for 2 days that even a reasonably small BOV, with a bottom mounted 2nd stage is too much bulk in heavy, turbulent current. But I don't think that free flow would likely ever be a problem, even in heavy head on current-as long as the BOV 2nd stage is on the bottom of the barrel. I only experienced free flow in OC mode at the surface. And remember that a BOV 2nd stage needs to be pressurized during the dive in order to keep the diaphram from collapsing as you descend. So, you will always need to have the gas on and some way to counter a free-flow of a BOV. You can install a flowstop and dive with it on, but I don't like the idea of adding more bulk and stiffness to a BOV setup than there already is. That's why I have a shut-off in the form of a ball valve on my offboard whip which would feed my BOV, instead of having a slider/flowstop inline, next to the BOV.

    After all my research and experience with the Divematics BOV and reading more of Mike's comments, now I'm back to the Nova FFM with a standard DSV and sidemounted reg-most compact, most flexible, most comfortable, most safe and no WOB compromise in either CC or OC. Not happy about the expense and the visual distortion in the plastic lens sides and what felt like a slightly narrower field of usable vision than a low volume mask, but I can deal...
    the Nova FFM sounds tempting but higher on the list for me is MOD 2+3, then an ISC Radial and then a needle valve... in that order. Like everything else it will probably take me at least a year to get comfortable with the idea of a FFM enough to get over my inhibitions, find someone who has one and spends 2 hours talking me into it at a dinner party, maybe then I'll go for it ... and then only to wish i'd done it 10 years ago. isn't that how it goes?! :D

    Gill Envy

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