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Thread: changes in my rEvo WOB?

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    RBW Member Nicool is on a distinguished road Nicool is on a distinguished road Nicool's Avatar
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    rEvo III micro FT RMS

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    changes in my rEvo WOB?

    hi community,

    I am writing to seek some advice, as i've had the impression over the last few months that the WOB on my rEvo isn't as good as it used to be.
    Maybe it's the diver who's declining, but i'd like to understand if there's something i could improve, be it on the unit or on how i use it!

    First of all, a bit about me & how i dive my rEvo
    I am MOD1, diving a rebreather mainly to get closer to wildlife (photography is my thing) and spend more time underwater (the more the better for me!).
    So i am using Air diluent, never dive deeper than 45 msw.
    I am 34 years old, rather fit, and been diving once per week except when vacationing somewhere exotic.
    My rEvo is a micro FT full RMS hCCR, with the rEvo harness and wing, harness appears to be "XS" size i noticed.
    I've been diving rebreathers since 2012 and done about 300 hours on various units: ~50 hours on a rEvo standard, then ~60 hours on a Poseidon mark VI, then back to rEvo with a micro mid 2014, since then ~200 hours on that unit, so 300 hours in total.
    So not very experienced, not a total newbie neither.
    Yet it's easy to take on bad habits, which maybe you can help pinpoint.

    There have been some changes into how i've dived my rEvo Micro mid-2017 so i thought i'd highlight these, and maybe that helps finding why i am now feeling less content with my WOB:

    How i've been diving my rEvo micro between Aug-2014 and May-2017
    A combination of:
    -at home: long no-deco shallow shore dives for macro photography: say 15 meters max, 2h-2h30 dives, either in winter 13 degrees drysuit (neo compressed) all the way to summer 23 degrees 8mm wetsuit. Little current, little effort.
    -at home: shorter deco dives, say 50-75mins, mostly between 25 and 45 meters, with 20 minutes deco max. Sometimes current but limited. Same dry/wet suits as before.
    -Bali 2015: mosty long dives 2h30-3h30, 5 to 35 meters, some currents, warmish water (26-27 deg C) and just 3mm wetsuit. Some deco up to 20mins but typically going away due to the dive profile (1+ hour spent in 5-15 meters).
    -Sudan May2017: some deco dives (5-10 mins max) but short 60-70mins, 45 meters max, very warm, 3mm wetsuit, lots of currents.
    Over that period i've used a combination of different suits and dived in various temperatures with more or less effort, and i don't recall feeling WOB problems.
    I even noticed how easier it was to swim against current with my rEvo (compared to OC) and i assumed it was due to the streamlined designed of the unit and higher PO2.
    However, i did have a few times "the snorts", a breather issue discussed here, and it seemed to appear on some very shallow dives when i was too focused on my photography and struggling a bit upside down or very flat (which isn't good with back-mounted counter lungs) and against some current. But apart from these, very happy with my WOB.

    How i've been diving my rEvo micro since i moved in Sydney (Sep-2017)
    First of all i shipped my rEvo to the factory for full service in June, and haven't dived it before relocating to Sydney (Sep2017) so that's 3 months with no diving (hadn't happened to me for years!) and possibly slight changes on the unit during servicing (e.g. harness position).
    Trying to highlight changes vs previous period:
    -now mostly shore diving (there's so much to see in the shallows)
    -max 15 meters for most, no deco
    -often some noticeable currents (tides!) and surge
    -temperatures between 14 and 22 degrees. Doesn't sound too cold but after 2 hours in 16 degrees being very static i have been veeeery cold, even in a drysuit.
    -i've hence changed drysuit: moving from a comressed neoprene to a membrane (Santi Emotion+), and i've used various layers of fourth element undergarnments, happy with the comfort in those.

    The issues i've experienced
    I've had "the snorts" a few times but this was clearly same reasons as before so i'm disregarding them.
    However i've felt in several dives short of breath, and although these were dives where we were moving quite a bit (discovering dive sites that were new for us), i haven't felt doing too much muscular effort, i wasn't exhausted on a muscle basis, but i felt short of breath.

    What i've tried
    -adjusting my harness making the shoulder strap tighter: the higher the rEvo on diver back, the better the WOB according to the user manual. With all the recent changes in undergarnments what worked with my previous drysuit was too loose on the membrane one which fits much closer to my body, and i had been easy going on that, so i tried to tighten the straps much more. Significant improvement, yet not great and i notice the shoulder strap are still "too large", saying they aren't tight on my arms, but i don't think i can tighten them more (see photo attached). Not sure if there are meant to be tight on your arms, or just not too lose?
    -working on the minimum loop volume: as Claudia points it in her very good article, some divers take bad habits on the minium loop volume and as i was still adjusting my weights with the new drysuit (3kg off and counting) i think i had somehow compensated a bit with the counterlungs! So lesson learnt, i'm now again very disciplined with WOB. Maybe too much as i've made my ADV very tight, and on shallow dives (5-8 meters) with surge i feel it can cause discomfort, yet i am re-working my skills.

    Help please :)
    That's about where i am, and i still feel not 100% comfort, so looking for any advice you may have on what could have affected my WOB and how i could improve.
    Some thoughts:
    -is it a problem that i cannot fully tighten the shoulder straps onto my arms? How tight are yours (if using standard harness)?
    -could i just be re-learning how to maintain optimal loop volume, and being too zealous i am causing my own discomfort in those shallow, surgy dives?
    -any piece in my rEvo that may have got worn over time or damaged during transportation? I am thinking about this angled backplate which is supposed to position the counterlungs at the right distance from my own lungs - anyone had issues with this one?
    -or my own position underwater, is diving too horizontal not good? With the new drysuit i get more air trapped in the feet (flexsoles) though i was in discomfort during last dive and it was wetsuit.

    Thanks in advance for sharing your thoughts!
    P.S. i know some of you have happily changed to a different harness brand. At this stage i'd like to leave this option aside, simply because i used to be content with that same harness a few months ago, so i'd like to work out what has changed and fix it.

    cheers
    Nicolas
    http://www.rebreatherworld.com/attac...&thumb=1&stc=1
    Attached Images

  2. #2
    RBW Member Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1 has a reputation beyond repute Gobfish1's Avatar
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    Re: changes in my rEvo WOB?

    zealous causing your own discomfort maybe
    dont see why ccr divers worry about saving a bit of gas ,
    or dive min loop , to shave off half a kg off lead or save 3 bar of gas .

    dump the lung s now and then , start again and take a good breath

    if your doing a lot of shallow divers your prob better off with a adv thats not to hard , if you over shoot /inflate a quick snort out your nose will sort it , a bit more it better then not enough, may want to get the straps sorted , you want unit close as you can ,
    Last edited by Gobfish1; 11th February 2018 at 13:20.

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    RBW Member jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold's Avatar
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    Re: changes in my rEvo WOB?

    Some of the things I found out with my Micro FT:

    I did my course on a rEvo 3 mini, and liked it, although I found the CL-volume too large, so I ordered a Micro FT because of its smaller CL-volume and improved travellability.

    I was lucky, and the CL-volume of the Micro FT almost matched my lung-volume perfectly, allowing me to dive it with MAXIMUM loop volume (yes I am special), which allowed me to be in full control of what is happening to my gas (no gas is added without me noticing almost immediately, and no gas escapes or expands without me noticing. Resulting in minimum effort to maintain my buoyancy.

    About breathing it, I tried to move it around a bit on my back, and found that I preferred it relatively low (lowest edge at where your back rounds the lowest when in trim), with the waist-strap angled down because of a short crotch-strap, so that I could breathe freely with my belly, instead of the chest.

    Also, I prefer the shoulderstraps (fixed, hogarthian) to be relatively loose, and they are "tightened" by tensioning the waist-strap and crotch-strap, which pulls the whole rig downwards.

    Also, I tightened the ADV as much as I could. I could just barely trigger it with close to a max effort. And I tightened my OPV as well, using my nose or mouth for exhaling excess gas.

    I also removed the rubber backplateprotectors. I figured out that even at just a couple mm, they still have a negative impact at hydrostatic breathing-resistance...

  4. #4
    RBW Member Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36's Avatar
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    Re: changes in my rEvo WOB?

    I dive my rEvo with the ADV a bit tight also. I have found that if I just let the machine do the work, I will often experience the WOB issues you speak of or as I refer to as "chest pain". I now make a conscience effort to make sure I take an extra deep breath to have the ADV fire enough to give me a bit over minimum loop volume and give me optimal loop volume instead.

  5. #5
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    Re: changes in my rEvo WOB?

    Just My 2cI
    I found having an absorbant cloth installed in the exhale lung impacted on the WOB as when it expanded it crushed the inhale lung. Not sure if the OP has this thought.


    Sent from my iPhone using Tapatalk

  6. #6
    RBW Member Nicool is on a distinguished road Nicool is on a distinguished road Nicool's Avatar
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    Re: changes in my rEvo WOB?

    Quote Originally Posted by Gobfish1  View Original Post
    zealous causing your own discomfort maybe
    dont see why ccr divers worry about saving a bit of gas ,
    or dive min loop , to shave off half a kg off lead or save 3 bar of gas .

    dump the lung s now and then , start again and take a good breath

    if your doing a lot of shallow divers your prob better off with a adv thats not to hard , if you over shoot /inflate a quick snort out your nose will sort it , a bit more it better then not enough, may want to get the straps sorted , you want unit close as you can ,
    hi Gobfish,
    Actually i wasn't worrying too much about the gaz consumption, the main downside of too much gas in the loop is that it makes breathing more tiring, as it's your own lungs exercising to circulate a larger volume of gaz through the loop.
    Ultimately, that may give you the feeling (on a physical dive) that you haven't got enough gas in the loop so you end up naturally adding more, whereas taking a break and reducing the gas volume would be the right solution.
    I recommend reading Claudia's article who explains it much better than i do.
    Both my wife and myself (both on rEvo micros) had experienced the same discomfort on same dive and noticed inappropriate loop volume as the likely cause.
    I think that's it, i am being too zealous on how much i am reducing it.

    Quote Originally Posted by jlovold  View Original Post
    Some of the things I found out with my Micro FT:

    I did my course on a rEvo 3 mini, and liked it, although I found the CL-volume too large, so I ordered a Micro FT because of its smaller CL-volume and improved travellability.

    I was lucky, and the CL-volume of the Micro FT almost matched my lung-volume perfectly, allowing me to dive it with MAXIMUM loop volume (yes I am special), which allowed me to be in full control of what is happening to my gas (no gas is added without me noticing almost immediately, and no gas escapes or expands without me noticing. Resulting in minimum effort to maintain my buoyancy.

    About breathing it, I tried to move it around a bit on my back, and found that I preferred it relatively low (lowest edge at where your back rounds the lowest when in trim), with the waist-strap angled down because of a short crotch-strap, so that I could breathe freely with my belly, instead of the chest.

    Also, I prefer the shoulderstraps (fixed, hogarthian) to be relatively loose, and they are "tightened" by tensioning the waist-strap and crotch-strap, which pulls the whole rig downwards.

    Also, I tightened the ADV as much as I could. I could just barely trigger it with close to a max effort. And I tightened my OPV as well, using my nose or mouth for exhaling excess gas.

    I also removed the rubber backplateprotectors. I figured out that even at just a couple mm, they still have a negative impact at hydrostatic breathing-resistance...
    Interesting, thanks jlovold! What's your typical diving position which makes this setup ideal to you, are you very horizontal or somehow angled heads up?

    Quote Originally Posted by Dsix36  View Original Post
    I dive my rEvo with the ADV a bit tight also. I have found that if I just let the machine do the work, I will often experience the WOB issues you speak of or as I refer to as "chest pain". I now make a conscience effort to make sure I take an extra deep breath to have the ADV fire enough to give me a bit over minimum loop volume and give me optimal loop volume instead.
    Thanks Dsix36 I'll work on that technique.

    Quote Originally Posted by cb1  View Original Post
    Just My 2cI
    I found having an absorbant cloth installed in the exhale lung impacted on the WOB as when it expanded it crushed the inhale lung. Not sure if the OP has this thought.
    Sent from my iPhone using Tapatalk
    Hi cb1, yes i am aware that putting an absorbant in the top counterlung impacts the WOB. In fact, rEvo recommends not to put any, but i have seen too much saliva there and i am nervous it coud slip into the sorb when moving aside/looking up.
    So i still have an absorbant (though i've reduced it in size) but i had also one before when i used to be happy about my WOB, so that's not the "delta" i am looking for.

    cheers to all
    Nicolas

  7. #7
    RBW Member jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold's Avatar
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    Re: changes in my rEvo WOB?

    I am always very horizontal. One of the reasons why I like to have the rEvo low is the lifting bar keeps interfering with the back of my head even if tilted back.

    I used a small moisture-absorber in the exhale lung, rolled up and stuffed down into the small pocket on the lower left side. Haven`t felt anything negative about that.

  8. #8
    RBW Member jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold's Avatar
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    Re: changes in my rEvo WOB?

    Oh, and one more thing:

    I removed the chopping-board. I never used it, and it didnt really do anything for me.

    That may not have had much to say about the wob, but still it would restrict some expansion of of the counterlungs if not in use.

  9. #9
    RBW Member Nicool is on a distinguished road Nicool is on a distinguished road Nicool's Avatar
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    Re: changes in my rEvo WOB?

    Quote Originally Posted by jlovold  View Original Post
    Oh, and one more thing:

    I removed the chopping-board. I never used it, and it didnt really do anything for me.

    That may not have had much to say about the wob, but still it would restrict some expansion of of the counterlungs if not in use.
    Thanks for this thatís interesting.
    And donít you get some pain in lower back by having the bottom of your rEvo rest there?
    Or itís sitting so low that itís ok?

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    RBW Member jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold is a jewel in the rough jlovold's Avatar
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    Re: changes in my rEvo WOB?

    Quote Originally Posted by Nicool  View Original Post
    Thanks for this thatís interesting.
    And donít you get some pain in lower back by having the bottom of your rEvo rest there?
    Or itís sitting so low that itís ok?
    I get some pain in my lower back, but the chopping-board didn`t help with that, because the problem is partially the weight-distribution of the rEvo, in combination with the buoyancy of your suit (dry or wet), and weightbelt or weightpockets, that induces a torque to your lower back.

    Moving your weightbelt down on your butt doesn`t really help much, because the rEvo is rear-heavy. One way to mitigate the problem is to put weights on the top-rack of the rEvo (I typically used 2-3 kgs there, but if you are able to move ballast down on your legs (in a way that gives them more or less homogenous neutral buoyancy), that should help greatly with the lower back. But that is very theoretical and probably impractical...

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