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Thread: Choosing GF factors

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    RBW Member ChristianM is an unknown quantity at this point ChristianM's Avatar
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    Choosing GF factors

    Hi all,

    as we switched to a JJ we also have to set the GF factors accordingly.
    My question is whether you are choosing diffrent GF factors for your dives or are you always using the same one?
    What come to my mind is something like choosing diffrent GF factors for:
    - shallow air dives
    - cold dives
    - scooter dives
    - ..
    So please give me some insides in what you are doing and why.

    Cheers,
    Christian

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    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Choosing GF factors

    For dives that I have a track record of doing just fine, I.e. one deco dive a day, not especially long deco (<75mins), warm enough, was able to use my usual gas choices, just all around "normal". I use 40/80.

    For dives that are much longer than my usual, much colder, deeper, lots of cave sawtooths, 2 dives a day, multiple deco diving days in a row, forced to use a new-to-me diluent choice, really anything that is "significantly different" I get more conservative and use 40/70

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    Re: Choosing GF factors

    I start at 50/70. That's in a cave for pretty much all conditions

    If I'm doing something like shallow/warm stuff, I'll bump it up to 50/85

    If something goes sideways on deco, suit flood, etc. then I'll change the GF-hi to 95. I'll try to stay in an extra 5-10 mins at 10ft after it clears at 95. One thing that I've started to do is try to go for at least 5-10 minutes of "surface deco" in the water while I'm shedding gear before I carry anything out of the water. Seems to help a lot

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    Supporting Member mt_diablo is an unknown quantity at this point mt_diablo's Avatar
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    Re: Choosing GF factors

    Quote Originally Posted by rjack  View Original Post
    For dives that I have a track record of doing just fine, I.e. one deco dive a day, not especially long deco (<75mins), warm enough, was able to use my usual gas choices, just all around "normal". I use 40/80.

    For dives that are much longer than my usual, much colder, deeper, lots of cave sawtooths, 2 dives a day, multiple deco diving days in a row, forced to use a new-to-me diluent choice, really anything that is "significantly different" I get more conservative and use 40/70
    Ditto. 40/80 on all dives and 90/90 on my backup if had to get out fast...

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    Re: Choosing GF factors

    30/80 on all dives, why play with what has a proven record for me.
    Gabe

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    Re: Choosing GF factors

    25/80 for me, but I also play with it for bailout plans.
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    Re: Choosing GF factors

    I run 60/90 for my regular diving. If the runtime is going to go over 4-5 hours, I will drop it down to 50/90. If the runtime is going to be over 8 hours, then I drop to 40/90 and will pad the shallow stops depending on the dive conditions.
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    Re: Choosing GF factors

    I run VPM B+3, which in total time comes alittle shy of 55/90.

    I like Dons numbers, gives me lots of extra bottom time. If I had to run GF again, I'd be 55/90, but probably hating it for deeper longer dives compared to VPMB3

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    Re: Choosing GF factors

    Quote Originally Posted by Dsix36  View Original Post
    I run 60/90 for my regular diving. If the runtime is going to go over 4-5 hours, I will drop it down to 50/90. If the runtime is going to be over 8 hours, then I drop to 40/90 and will pad the shallow stops depending on the dive conditions.
    My understanding of the numbers is different than Don. The first number as I understand it determines how deep your stops come in. The second how aggressive the deco profile is.

    Currently I am running 40/80 for most diving. For bigger dives and repetitive days of bigger diving I lower the second number to 75 or 70.

    I may yet bring up the first number a bit as I feel more comphy with the shallower first stop.

    A 90 as the second number seems very aggressive.

    I don’t get moving the bottom number and keeping a very high second number.

    Often I have found myself out to lunch on this stuff and my question is genuine.

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    Re: Choosing GF factors

    Quote Originally Posted by Dsix36  View Original Post
    I run 60/90 for my regular diving. If the runtime is going to go over 4-5 hours, I will drop it down to 50/90. If the runtime is going to be over 8 hours, then I drop to 40/90 and will pad the shallow stops depending on the dive conditions.

    Quote Originally Posted by PeterVICEG  View Original Post
    My understanding of the numbers is different than Don. The first number as I understand it determines how deep your stops come in. The second how aggressive the deco profile is.

    Well as fiddling with the low GF always also influence the hi GF even if you keep one value steady generally lowering one number (no matter which) is giving you a more conservative deco approach as it is increasing the overall deco time and increasing any of the two numbers is decreasing overall deco time and hence results in a more aggressive profile..


    With which number of the both you fiddle is determining the "shape" of the profile and not necessarily the overall conservatism..
    To me overall conservatism is best compared by comparing total decompression times of the same bottom dive profile..


    having said that: 60/90 is quite aggressive overall for sure.. 40/90 okish for my taste.. but I would never exceed a 85 for the high GF.. then rather up the lo and go shallower faster..


    to answer the OPs question:
    I mostly dive 50/70 as "standard" especially in warmer waters where I don't mind the "extra shallow" time..
    on colder waters I might migrate to a 40/85 to shorten the shallow time where one might more easy get colder (at least phsycologically) even when same time is spent in the water.. The deeper stops are more "demanding" as you "move" every 2 min..


    some extra padding on "unplanned" depending on the conditions and event..


    Shit hit the fan BO plan CC and OC: 90/90

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