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  1. #11
    GUE Tech and Cave Instructor johnkendall's Avatar
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    Quote Originally Posted by jturner View Post
    Not even just drown - it will the worse than that! Fatally killed to death.
    I'm not a cavey person but I have to say from the few times I've tried it for more than a few minutes, it is an utter balls-ache to do continuously whilst doing other things, and unless I had no other choice (eg CCR has failed and bailout has all leaked away so it was SCR or death), I'd rather not.
    YMMV and all that. I don't think I count as the great or good, so feel free to ignore me!
    I've never seen it, but have spoken with guys who have done body recoveries. It's not unusual for the finger tips to be shredded, where the diver has tried to claw through the rock.

    Gas in a cave is easy. Just carry enough to always be able to get out. Navigation, or confusion is what is most likely to kill you.

    Thanks
    John

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    John Kendall
    GUE Instructor Trainer, Tech and Cave Instructor www.johnkendall.com
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  2. #12
    Red Hot Totty ;) Hot Totty's Avatar
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    My understanding (and I’ll admit it’s limited to ripen water) is scr is a gas extender when your o2 has all gone and you need to get back to the shot.
    www.wapsac.co.uk
    Apparently becoming a grandad

  3. #13
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    Quote Originally Posted by johnkendall View Post
    I've never seen it, but have spoken with guys who have done body recoveries. It's not unusual for the finger tips to be shredded, where the diver has tried to claw through the rock.

    Gas in a cave is easy. Just carry enough to always be able to get out. Navigation, or confusion is what is most likely to kill you.

    Thanks
    John

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    Also the nice thing about caves is they can be set up with safeties. There really is no excuse not to have enough of gas in a cave.

    I won’t say that all else fails I wouldn’t do scr - but it wouldn’t be part of plan

  4. #14
    Established TDF Member OutOfTest's Avatar
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    I was doing a dive this summer. My bailouts (not including 2 other CCRs) ran up to:

    2x20L 15/55
    4xAl80 15/55
    Al80 21/35
    Al80 35/25
    2xAl80 50%
    Al80 O2
    20L O2

    That's 1.5x the gas calculated as required for bailout. It's no problem. I'd quite easily and happily take more if required.

    I have an offboard whip on my KISS. It plugs into any of my OC bottles. I can SCR, do I plan to? No. It's an absolute sh1t hits the fan option that's available once my KISS goes down with a failure that means I can still SCR, my bailout breather goes down, and my OC has failed in a few different places to make it look like I'm really not gonna get out on it even with 1.5x reserve. I hope I never have to do it, and if my whip was ever unoperable, I'd very happily take it off and do the dives without.

    As an aside, going into the overhead on a rebreather for your first dives there is a terrible idea in general. That might be a better topic of conversation than SCR...see my new topic.

  5. #15
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    Course is OC mate, this is for the future!

  6. #16
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    So probably less divisive than I suspected. I must admit it wouldn't be in any planning going forward because the failure band it applies to is too narrow, but I will practice it a bit more over winter to have it as an option.

  7. #17
    Old but keen Mark Chase's Avatar
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    Yes but we all know cave divers are several slices short of a loaf

    SCR is a skill you should lurn and have as an option available for you but it should not be part of dive planning for bailout

    The options for bailout should be (in order of preference)


    1: Personally carried or staged OC bailout all the way out

    2: Personally carried deep and intermediate gas + drop tank

    3: Teem bailout

    4: SCR


    For you to need to go SCR you will have suffered a CCR failure which has left you with no PP02 readings but a dry loop

    & Loss or failure of your OC bailout

    & Lost your access to your buddies / teems bailout

    When the choice is down to breathing water and going SCR, you go SCR but if you survive it just remember how you monumentally screwed up to the point where it became necessary



    I have planned v deep like 80-120m dives where my deep bailout SAC calculations have been tight. Like below 15SAC tight. My reasoning is its unlikely the failure will happen at the farthest point from the shot, its unlikely it will take me as long to return to the shot as it took me to get there, its unlikely Ill actualy be at potential max depth and theres a possibility my buddy could help out. BUT If not then SSCR for 10 -15 mins to get back to the shot, is a viable option

    But remember we both have the same problem in that loop recovery from a flood is bordering on the impossible ESPECIALY if it was a sudden large flood. If it was a slow flood you should have been heading back to the shot anyway

    In the early days I tried a full SCR bailout on three hours deco plan.

    I suffered miserably and failed after about 2 hours I believe had a C02 hit as well (massive headache post dive)

    Had it been a real dive real emergency id have defo blown off that last hour and gone up. I simply couldn't take it anymore.


    This was on an inspo classic which had MAV and duel buttons on front mounted lungs which made gas switching and SCR easy.
    Last edited by Mark Chase; 07-12-2018 at 07:41 AM.

  8. #18
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    Holme bank is not that big a cave as I used to be able to view the hill from my bedroom window. I expect for training then it's a consideration.

  9. #19
    Established TDF Member steelemonkey's Avatar
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    Any chance of someone explaining all these abbreviations? I always thought SCR was surface consumption rate.
    Not as though I will ever use a 'breever of go cave diving, but I like to follow threads out of interest.
    You lot are like the computer guys, you speak a totally different language.
    Paul.
    If God had meant us to breathe underwater, he would have given us larger bank balances.
    Human beings were invented by water as a means of moving itself from one place to another.

  10. #20
    Old but keen Mark Chase's Avatar
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    Quote Originally Posted by steelemonkey View Post
    Any chance of someone explaining all these abbreviations? I always thought SCR was surface consumption rate.
    Not as though I will ever use a 'breever of go cave diving, but I like to follow threads out of interest.
    You lot are like the computer guys, you speak a totally different language.
    SCR Semi closed Rebreather


    Fill loop with OC gas, breath it 4 X then flush with fresh gas


    This extends your OC tank 3-400%

    Its used for total loss of PP02 display or failed scrubber as the flush replenishes 02 and vents away most of the C02


    Problems are low PP02 bailout on ascent with an ever dropping PP02 need to be allowed for

    C02 is cumulative so even a small amount on the loop will start to build up and cause a full on C02 hit in the end.

    In theory we only use 25% of inhaled 02 the rest is exhaled back into the loop


    Also we only need a PP02 of about 0.11 to stay conscious as long as we are not exerting ourselves. So you can breath down a loop starting at say 1.3pp02 and breath that gas down to 0.11 before you pass out


    On a KISS this is extremely usefull as the KISS also trickles in 02 to top up the loop, so if you know your 02 consumption you can figure out roughly when your PP02 needs toping up.



    This was a shallow cave and at min 20 I toped up to set point of 1.0 (but its showing as 0.9 on the graph)


    At min 34ish theres a small bump up as I hit the ADV and about min 38 I hit 0.15pp02 So somewhere around 15mins (allowing for hitting the adv and adding .21%) on one 0.9pp02 loop full of gas before it dropped to unbreathable

    Note also that due to running a pretty good min loop I hit the adv before the PP02 dropped below 0.2 which was a pretty handy warning if id been on the ball.

    Hypoxic1 by markchase8, on Flickr
    Last edited by Mark Chase; 07-12-2018 at 08:06 AM.


 
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