+ Reply to Thread
Page 5 of 5 FirstFirst 1 2 3 4 5
Results 41 to 45 of 45

Thread: 4 tank config

  1. #41
    aka Scotty com1 will become famous soon enough com1 will become famous soon enough com1 will become famous soon enough com1's Avatar
    Join Date
    May 2007
    Location
    Frankfurt & Budapest
    Posts
    362
    inspiration vision

    Re: 4 tank config

    I am always open to switch to more safe configs.
    With the gases you suggested, can you please post an example of a 90m/30min dive (+2 minutes OC at 90m).
    I donīt see how this can work with 80 cft tanks.

  2. #42
    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
    Join Date
    Jan 2007
    Location
    Seattle
    Posts
    405
    Meg

    Re: 4 tank config

    Quote Originally Posted by Nitrogenius  View Original Post
    Who told you that?? you cant quite be serious!
    in what sense iffy?
    For Bailout? Well if you Bail at 90 you should ascend immediately anyways and if you have regs that really suffer from density issues at such depths, please reconsider equipment.


    From lung-functionality at 90 on BO ?
    well that certainly is tolerable give the event - keep in mind this is not regular OC diving spending a lot of time at depth on OC with that gas!


    In Loop ? Surely there is no density issue whatsoever with that mix..


    60% He is certainly very good with no issues for up to 100m and even a bit beyond depending on your narcosis approach.. A 10/60 you gets you a Narcosis depth of 31m @ 100m after all..


    Don't judge and comment gas choices above your own level of diving based on hearsay..
    Looking at your profile the latter is the only conclusion you might have come to such opinion..
    Its not the END its the density, the lower limit based on the recommendations here:
    https://www.omao.noaa.gov/documents/...edings-2016pdf
    is 5.2 g/L
    depending on the ppO2 and temperatures a loop with only 60% is right at the cusp around 75m.

    The relevant paper starts on page 66 and was also discussed here:
    http://www.rebreatherworld.com/showt...nsity-planning

    at 90m and a ppO2 of 1.2 the loop has a density of about 5.9g/L, which is why I said it was "iffy"
    Last edited by rjack; 11th November 2017 at 09:56.

  3. #43
    aka Scotty com1 will become famous soon enough com1 will become famous soon enough com1 will become famous soon enough com1's Avatar
    Join Date
    May 2007
    Location
    Frankfurt & Budapest
    Posts
    362
    inspiration vision

    Re: 4 tank config

    Quote Originally Posted by rjack  View Original Post
    Its not the END its the density, the lower limit based on the recommendations here:
    https://www.omao.noaa.gov/documents/...edings-2016pdf
    is 5.2 g/L
    depending on the ppO2 and temperatures a loop with only 60% is right at the cusp around 75m.

    The relevant paper starts on page 66 and was also discussed here:
    http://www.rebreatherworld.com/showt...nsity-planning

    at 90m and a ppO2 of 1.2 the loop has a density of about 5.9g/L, which is why I said it was "iffy"
    I remember seeing Simonīs presentation a while ago, thx for the link.
    The document is saying the ideal gas density is below 5,2 and absolute maximum is 6,2 g/l.
    So I am close to the upper limit.
    I may change my BTM gas to something with 70% HE.

    A double 20 l PSCR frame would solve all my onboard gas issues, wouldnīt mind about the weight.
    Does a rEvo somehow fit inbetween?

  4. #44
    Jst anothr Breather Diver Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius's Avatar
    Join Date
    Jan 2010
    Location
    Germany
    Posts
    1,147
    rEvo III rms

    Inspo HH + classic Dolphin Ray

    Re: 4 tank config

    Quote Originally Posted by com1  View Original Post
    I am always open to switch to more safe configs.
    With the gases you suggested, can you please post an example of a 90m/30min dive (+2 minutes OC at 90m).
    I donīt see how this can work with 80 cft tanks.

    I have been working from the numbers you gave me.
    I can not give you a dive plan as I have no idea how you get to the gas amounts you mentioned for that specific dive, but if you use:


    1289.7 ltr Trimix 12/60 (7l+3l)
    925.0 ltr Trimix 20/35 (7l)
    955.6 ltr Nitrox 32 (7l)
    1894.9 ltr Nitrox 50 (11.1l)
    1500.7 ltr Nitrox 99 (7l+3l)


    then I cant see how:


    having 1 80 10/60 and 1 80 15/45 should not work instead of your 12/60 + 20/35 + 32
    You use app 3200 L until you get to your 50% and 2 80 cft are equaling 4400 L
    Leaving out the 32 and having a 15/45 should not impact your deco plan too significant.. according to rough estimates you get to your 50 maybe 8 min later but that's maybe 600 L so you still be using less than the 4400 L available. you can also tweak that second gas a bit like eg a 16/30 or so that should further reduce the gap..
    Going shallower quickly might also be worth looking into.
    Or giving up on using your CCR Mix Gas as Bailout entirely..
    Like I said don't know how you plan and get to those numbers you provided (too many variables), I was just judging from those and thought it should be doable..
    If it does not work for you and you really need those 5 gases for your plan, then ok..
    I still would suggest to have a full 80 cft for deep BO available so again there goes the thought of that 7 L ;)


    If I was planning that dive my Bailouts would be:


    80 cft 16/45 (with BOV connected via QCs to that if diving with BOV)
    80 cft 20/30
    80 cft 50%
    40 cft 100%


    and I would all carry them sidemounted..
    When you properly sidemount (like in OC sidemounting) you actually have your chest fairly free and you still maintain a decent streamlined profile..
    The 20/30 would be SM left the 50% would go right..
    Under the left tank would go the 16/45 to have that also accessible right away..
    the oxy goes under the 50%..


    When ascending from an uneventful dive as soon as I reach my first Deco stop (which at such profile still is shallower than BO MOD for the second gas (20/30) the 16/45 gets clipped to a crotch Dring and is out of the way.. it floats and does not create an issue there..
    As you can see here the BOV becomes an issue (this is why I said if Diving with Bov) either all BO regs need to have a QC and the connection is made under water (which in cold water I do not like for the water ingress) or the BOV is disconnected from that point onwards..
    Then when hitting the 21 m stop the 20/30 is being clipped back to the crotch again and the 50% is moved to the left side.. after that one is nicely streamlined for the then onwards longer part of the dive..
    You have streamlined profile that way, all Bailouts on you and it also comes with the advantage that the Bailout also would maintain to go to the lowest left side tank for the muscle memory..
    Lastly in comparison with your approach to it the Bailout Gases used that way also do not have any fancy PN jumps that might trigger an isobaric event..


    Cheers ;)

  5. #45
    Jst anothr Breather Diver Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius is a splendid one to behold Nitrogenius's Avatar
    Join Date
    Jan 2010
    Location
    Germany
    Posts
    1,147
    rEvo III rms

    Inspo HH + classic Dolphin Ray

    Re: 4 tank config

    Quote Originally Posted by rjack  View Original Post
    Its not the END its the density, the lower limit based on the recommendations here:
    https://www.omao.noaa.gov/documents/...edings-2016pdf
    is 5.2 g/L
    depending on the ppO2 and temperatures a loop with only 60% is right at the cusp around 75m.

    The relevant paper starts on page 66 and was also discussed here:
    http://www.rebreatherworld.com/showt...nsity-planning

    at 90m and a ppO2 of 1.2 the loop has a density of about 5.9g/L, which is why I said it was "iffy"


    Thanks for explaining.. I had been focusing on OC SM Cave diving for a while and did not dive my rebreather for a while and also did not follow the "news" that closely anymore..
    So in fact I have missed this. Thanks for the links..
    From own experience I think following the "ideal" would force one into "too much" Helium quite early with all the issues of extremely high helium comntents, so as always it is a trade off.. But for sure it makes sense to keep an eye out for the upper limit..

+ Reply to Thread
Page 5 of 5 FirstFirst 1 2 3 4 5

Posting Permissions

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