+ Reply to Thread
Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 25

Thread: Anatomy of a deep rebreather dive

  1. #1
    RBW Member bobbob23 is an unknown quantity at this point bobbob23's Avatar
    Join Date
    Jun 2008
    Location
    at home
    Posts
    37

    Anatomy of a deep rebreather dive

    First things first: I am not a rebreather diver nor am I looking for instruction I am only asking this out of curiosity, nothing more.

    So Iím trying to get my head around what a deep (80-100m) dive would go down like and have a few questions about what would happen and when. So the best way I think of going about this is to write down what I think happens and when so hopefully can let me know if I get something mixed up or wrong. Iíll be using multideco for calcs and deco but Iíve never used it in CCR mode so donít know what Iím doing. I will be using the first person but donít take this to mean anything. Iíll ask a few questions to clear up some things before going through the whole planning or bail out calcs which I will leave until later.

    So letís say a 100m dive with 20min bottom time and we can assume nothing goes awry.
    1. Letís assume I have a reasonably stock CCR equipped with a BOV. What dil would one use (10/70)? Whatís my bailout look like three cylinders: Ali 80 with 10/70 another with Nx50 and one more with 80-100%
    2. Predive checks carried out and all is good, setpoint would be set at the surface to 0.7?
    3. Begin the descent, the BOV will be connected to my highest O2 bailout stage?
    4. During the descent, I would increase my setpoint to 1.0 - 1.3, what depth would this change happen, what setpoint for this dive?
    5. I would need to switch my BOV to a safe working gas would I go onto my deepest bailout as soon as itís breathable?
    6. All the bailout bottles have a quick disconnect how is hose routing to the BOV done? Especially given that some people have stages on both sides?
    7. Many of the plans give me back CNS errors (set at 80%) what should be entered into multdeco?
    8. Quite a few of the plans go well beyond three hours scrubber time as far as I can see are often rated for three hours with how is this dealt?
      Some people dive with a bail out breather
    9. how is the setpoint managed on a device that isnít being used actively during the dive?
    10. Given the BOB will have counterlungs full of gas how is buoyancy is managed?

  2. #2
    RBW Member Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll is a jewel in the rough Clive O' Driscoll's Avatar
    Join Date
    Feb 2007
    Location
    Cork Ireland
    Posts
    697
    Meg 2.7 :) - of course

    Megalodon 2.7

    Re: Anatomy of a deep rebreather dive

    Quote Originally Posted by bobbob23  View Original Post
    first things first: I am not a rebreather diver nor am i looking for instruction i am only asking this out of curiosity, nothing more.

    So iím trying to get my head around what a deep (80-100m) dive would go down like and have a few questions about what would happen and when. So the best way i think of going about this is to write down what i think happens and when so hopefully can let me know if i get something mixed up or wrong. Iíll be using multideco for calcs and deco but iíve never used it in ccr mode so donít know what iím doing. I will be using the first person but donít take this to mean anything. Iíll ask a few questions to clear up some things before going through the whole planning or bail out calcs which i will leave until later.



    So letís say a 100m dive with 20min bottom time and we can assume nothing goes awry.
    1. letís assume i have a reasonably stock ccr equipped with a bov. What dil would one use (10/70)? Whatís my bailout look like three cylinders: Ali 80 with 10/70 another with nx50 and one more with 80-100%
    2. predive checks carried out and all is good, setpoint would be set at the surface to 0.7?
    3. begin the descent, the bov will be connected to my highest o2 bailout stage?
    4. during the descent, i would increase my setpoint to 1.0 - 1.3, what depth would this change happen, what setpoint for this dive?
    5. i would need to switch my bov to a safe working gas would i go onto my deepest bailout as soon as itís breathable?
    6. all the bailout bottles have a quick disconnect how is hose routing to the bov done? Especially given that some people have stages on both sides?
    7. many of the plans give me back cns errors (set at 80%) what should be entered into multdeco?
    8. quite a few of the plans go well beyond three hours scrubber time as far as i can see are often rated for three hours with how is this dealt?
      Some people dive with a bail out breather
    9. how is the setpoint managed on a device that isnít being used actively during the dive?
    10. given the bob will have counterlungs full of gas how is buoyancy is managed?


    do your training ffs

  3. #3
    New Member jmark18 is an unknown quantity at this point jmark18's Avatar
    Join Date
    Mar 2005
    Location
    DundasOntario,Canada
    Posts
    70
    Sport Kiss

    Re: Anatomy of a deep rebreather dive

    This has to be a troll. If not god help you and leave your dive plan so someone will know where to find the body

  4. #4
    RBW Member bobbob23 is an unknown quantity at this point bobbob23's Avatar
    Join Date
    Jun 2008
    Location
    at home
    Posts
    37

    Re: Anatomy of a deep rebreather dive

    Nope not a troll, genuinely interested. Thought I was pretty clear on that in the intro. Not ready to buy a unit, I'm not trimix qualled am diving on doubles and stage, tdi adv nitrox and deco procedures.
    I couldn't even do anything close to this even on oc just want to know the ins and out of doing something like this on closed circuit.
    Last edited by bobbob23; 8th July 2018 at 02:10.

  5. #5
    RBW Member broncobowsher is on a distinguished road broncobowsher is on a distinguished road broncobowsher's Avatar
    Join Date
    Jul 2012
    Location
    Arizona
    Posts
    239
    TBD

    Re: Anatomy of a deep rebreather dive

    Doesn't look like a troll to me. Just someone who is doing research and is smart enough to ask questions. Only worth flaming if that was an actual plan and was going to ignore any advise. He CLEARLY states he isn't a rebreather diver and just researching what it would take. I'm a rebreather diver and don't even know how to plan that advanced of a dive.


    Just give him what he is asking for.
    If everything goes right, what to expect.
    If you have to bail at the 20 minute mark, what to expect.
    Don't have to be 100% spot on, but at least a reasonable plan.

  6. #6
    RBW Member bobbob23 is an unknown quantity at this point bobbob23's Avatar
    Join Date
    Jun 2008
    Location
    at home
    Posts
    37

    Re: Anatomy of a deep rebreather dive

    Quote Originally Posted by broncobowsher  View Original Post
    Doesn't look like a troll to me. Just someone who is doing research and is smart enough to ask questions. Only worth flaming if that was an actual plan and was going to ignore any advise. He CLEARLY states he isn't a rebreather diver and just researching what it would take.
    Thank you, it's been ten years since I first started diving and first joined this board, I then dropped out of all boards because of the snarky responses. I really thought I was exceptionally clear at the beginning of the OP but wasn't expecting the responses. Including one that was predicting my death after trying an extremely deep dive on my imaginary rebreather.

    I've tried to learn as much as possible with regard to rebreathers but the majority of printed material deals with the basics of function and I haven't found much on the minutiae of a deep technical dive using CCR. I was hopeful that I might get some good responses but discouraged by the first replies.

    Even if I never end up doing a dive as involved as this what harm comes from knowing how it happens?

  7. #7
    RBW Member Dive Africa is an unknown quantity at this point Dive Africa's Avatar
    Join Date
    Feb 2007
    Location
    South Africa
    Posts
    175
    Meg Classic & Meg 15

    Re: Anatomy of a deep rebreather dive

    Quote Originally Posted by bobbob23  View Original Post
    Thank you, it's been ten years since I first started diving and first joined this board, I then dropped out of all boards because of the snarky responses. I really thought I was exceptionally clear at the beginning of the OP but wasn't expecting the responses. Including one that was predicting my death after trying an extremely deep dive on my imaginary rebreather.

    I've tried to learn as much as possible with regard to rebreathers but the majority of printed material deals with the basics of function and I haven't found much on the minutiae of a deep technical dive using CCR. I was hopeful that I might get some good responses but discouraged by the first replies.

    Even if I never end up doing a dive as involved as this what harm comes from knowing how it happens?


    see run tables like this - gasses chosen like this because same gasses used down to 125m (different bottom gas). CNS could run well over 100% - it happens. If yoiu use BOV - youcould consider switching block that can take two gasses - one hypoxic(deepdil) and one normoxc - need to consider counte diffusion in choices - in deepdiving |I found that switching blocks make choices just too complicated. your choice - decisios to be made on experience.

    Caveat - this dive plan based on very specific target/fitness and experience. VPM - will not dive this any more just had it at hand as an example of what we did 10 years ago

    105m
    Sodwana Ė Dil: 6/70 - (PO2: 1.3)
    Jesser Canyon Ė 15min @ 105m - +4 Ė SI 20:00 TTS: 153 min
    Depth Up  Bailout B-Gas 3min B +2+2 Ex Out
    6 60 (173) 45 (138) O2 (1160) 21 (67) 67 (193) 38 (134)
    9 15 (113) 14 (93) 6 (46) 18 (126) 13 (96)
    12 12 (98) 9 (79) 5 (40) 13 (108) 9 (83)
    15 10 (86) 7 (70) 3 (35) 10 (95) 7 (74)
    18 7 (76) 5 (63) 3 (32) 9 (85) 6 (67)
    21 6 (69) 4 (58) 50 (1440) 2 (29) 7 (76) 6 (61)
    24 6 (63) 4 (54) 2 (27) 6 (69) 4 (55)
    27 4 (57) 4 (50) 2 (25) 5 (63) 4 (51)
    30 4 (53) 3 (46) 1 (23) 4 (58) 3 (47)
    33 3 (49) 2 (43) 1 (22) 4 (54) 2 (44)
    36 3 (46) 2 (40) 1 (21) 3 (50) 3 (42)
    39 3 (43) 1 (38) 1 (20) 3 (47) 2 (39)
    42 2 (40) 2 (37) 1 (19) 3 (44) 2 (37)
    45 2 (38) 1 (35) 28/25 (1320) 1 (18) 2 (41) 2 (35)
    48 2 (36) 2 (34) 1 (17) 2 (39) 1 (33)
    51 2 (34) 1 (32) 1 (16) 1 (37) 2 (32)
    54 1 (32) 1 (31) 1 (15) 2 (36) 1 (30)
    60 3 (31) 2 (30) 1 (14) 3 (34) 2 (29)
    66 2 (28) 2 (28) 20/40 (810) 1 (13) 2 (31) 2 (27)
    72 2 (26) 2 (26) --- 2 (28) 1 (25)
    78 1 (24) 1 (24) --- 1 (26) 1 (24)
    84 1 (23) 1 (23) --- 1 (25) 1 (23)
    105 15 (20) 15 (20) 10/65 (1040) 3 (8) 17 (22) 15 (20)

  8. #8
    RBW Member jvos is on a distinguished road jvos is on a distinguished road jvos's Avatar
    Join Date
    Jan 2006
    Location
    Michigan
    Posts
    40
    Apeks Meg

    BMR500 IDA

    Re: Anatomy of a deep rebreather dive

    Switching gases between BOV is not necessary. Just setup for deep section.

  9. #9
    RBW Member dreamdive has disabled reputation dreamdive's Avatar
    Join Date
    May 2007
    Location
    Delray Beach, FL
    Posts
    1,276
    Pathfinder, rEvo, Explorer

    Meg, PrismII, Titan, Optima, 7

    Re: Anatomy of a deep rebreather dive

    Why don't you take a trimix ccr class attending the theoretical part only, since you are not qualified to dive it.


    Not sure what you are trying to understand/gain when you are not even a basic CCR diver. Using a BOV or not is very specific and again, for someone who does not even have a basic CCR cert, I don't understand why you are asking.


    Not wanting to give you a "snarky" reply. I do agree with some of members here that your questions are suspicious since your motive of "just curious, nothing more" is not easily bought.


    Quote Originally Posted by bobbob23  View Original Post
    First things first: I am not a rebreather diver nor am I looking for instruction I am only asking this out of curiosity, nothing more.

    So Iím trying to get my head around what a deep (80-100m) dive would go down like and have a few questions about what would happen and when. So the best way I think of going about this is to write down what I think happens and when so hopefully can let me know if I get something mixed up or wrong. Iíll be using multideco for calcs and deco but Iíve never used it in CCR mode so donít know what Iím doing. I will be using the first person but donít take this to mean anything. Iíll ask a few questions to clear up some things before going through the whole planning or bail out calcs which I will leave until later.

    So letís say a 100m dive with 20min bottom time and we can assume nothing goes awry.

    1. Letís assume I have a reasonably stock CCR equipped with a BOV. What dil would one use (10/70)? Whatís my bailout look like three cylinders: Ali 80 with 10/70 another with Nx50 and one more with 80-100%
    2. Predive checks carried out and all is good, setpoint would be set at the surface to 0.7?
    3. Begin the descent, the BOV will be connected to my highest O2 bailout stage?
    4. During the descent, I would increase my setpoint to 1.0 - 1.3, what depth would this change happen, what setpoint for this dive?
    5. I would need to switch my BOV to a safe working gas would I go onto my deepest bailout as soon as itís breathable?
    6. All the bailout bottles have a quick disconnect how is hose routing to the BOV done? Especially given that some people have stages on both sides?
    7. Many of the plans give me back CNS errors (set at 80%) what should be entered into multdeco?
    8. Quite a few of the plans go well beyond three hours scrubber time as far as I can see are often rated for three hours with how is this dealt?
      Some people dive with a bail out breather
    9. how is the setpoint managed on a device that isnít being used actively during the dive?
    10. Given the BOB will have counterlungs full of gas how is buoyancy is managed?

  10. #10
    RBW Member topper133 is an unknown quantity at this point topper133's Avatar
    Join Date
    Dec 2016
    Location
    UK
    Posts
    17
    XCCR

    Thumbs up Re: Anatomy of a deep rebreather dive

    Quote Originally Posted by bobbob23  View Original Post
    So let’s say a 100m dive with 20min bottom time and we can assume nothing goes awry.
    What dil would one use (10/70)? I try to keep my dil PO2 at 1.1 and my end < 30m so yes probably a 10/70.
    What’s my bailout look like three cylinders: Ali 80 with 10/70 another with Nx50 and one more with 80-100% - You would want an intermediary drop in He, so maybe a 18/35, and a 60-70% (and maybe a 4th depending on your SAC) etc.
    Predive checks carried out and all is good, setpoint would be set at the surface to 0.7? - Yes
    Begin the descent, the BOV will be connected to my highest O2 bailout stage? No, plug into deep BO, why bother with anything else? Many don't even dive with a BOV!
    During the descent, I would increase my setpoint to 1.0 - 1.3, what depth would this change happen, what setpoint for this dive? Many different answers, I manually inject O2 at 10m or so to bring it to 1.0, the descent alone will increase the PO2, I usually find I'm there or there abouts at 1.3 at the bottom, then I change my setpoint to 1.3 or just continue to run manually which I find good practise sometimes.
    All the bailout bottles have a quick disconnect how is hose routing to the BOV done? I don't, BOV to deep water BO, then the rest just OC regs, there are hundreds of different ways to skin this cat.
    Many of the plans give me back CNS errors (set at 80%) what should be entered into multdeco? Yup, suck it up!

    I don't use a BOB so cannot comment.

    *Caveat, these are my own thoughts procedures etc, do not take\use them without consultation with an instructor (of which i am not one!).*
    **Again this is my own, not looking for a slanging match on the rights and wrongs of my procedures, just trying to help the OP**

+ Reply to Thread
Page 1 of 3 1 2 3 LastLast

Posting Permissions

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