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Excellent Deco Model Summary Video

Discussion in 'Technical Diving' started by Sidemount_Stu, Mar 11, 2017.

  1. Sidemount_Stu

    Sidemount_Stu Sidemount & Sane!
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    I came across this excellent video today, one of the best and most simple i've seen for explaining the difference between standard gas uptake models and Bubble models... an interesting watch with some excellent references.... it's made me reconsider the GF's I use..... it's quite long, 45 mins, but well worth watching all of it.....



    Hope it's of interest to some of you .....
     
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  2. nickb

    nickb Active Member

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    I've seen Simon give this presentation, he's always an outstanding speaker. He's great fun too, I've been on a couple of liveaboard trips with him.

    Probably a thread in its own right, but for context, what GFs have you been using?
     
  3. Sidemount_Stu

    Sidemount_Stu Sidemount & Sane!
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    I've varied between 20/80 and 30/75
     
  4. nickb

    nickb Active Member

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    So, are you thinking about upping the low GF? I was using 70/85 all last year, up from 50/85 previously. I've just reverted my Shearwaters to 50/85 as there's little or no difference when one tries to actually do the profiles.

    I do dial the high GF back a bit if I'm doing a lot of diving (liveaboard etc.)

    Mark Powell gave a presentation at last year's Dive Show and suggested that a low GF below 30 is probably not good.
     
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  5. Sidemount_Stu

    Sidemount_Stu Sidemount & Sane!
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    Yes, i'm thinking of upping my low GF to 50 or 60.... probably keep the High GF as 75 or 80... probably start at 50/80 and see how i feel etc
     
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  6. Wibble

    Wibble Fish don't talk
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    I use 50/80 for my planning which was recommended to me by someone I trust. Admittedly my diving's not particularly deep, down to 45ish, but it's been fine for me.

    The low GF has quite an affect on the deeper initial stops. There's some chatter over the whole deep-stop thing now suggesting that it's not as effective as once thought. I'll try to dig out the references.
     
  7. Wibble

    Wibble Fish don't talk
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  8. Sidemount_Stu

    Sidemount_Stu Sidemount & Sane!
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    LOL.. Watch the video....
     
  9. Doomanic

    Doomanic Dinosaur Wrangler
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    I have the attention span of a goldfish, what's the gist of it?

    FWIW, I currently use 30/85 as a throwback to my OC diving with Gooers as it's fairly close to RD.

    I had a play with Baltic Deco today, 50/85 saves 1 minute on a 42m 30 min BT dive.
     
  10. Sidemount_Stu

    Sidemount_Stu Sidemount & Sane!
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    Honestly, it's worth making the effort to watch....

    the gist of it is, that standard (no GF) Buhlmann is about getting you into the shallows, long shallow stops then out.... bend & mend.... whilst Bubble models are based entirely on theory, with no research based evidence.... the theory goes that deeper stops prevent (minimise) bubble formation, so the theory states that you start your stops deeper, and do shorter stops all the way up... you often find this get you out of the water marginally quicker too.

    Gradient Factors were a way (as you already know) to make Buhlmann model behave more like a Bubble model, by altering the deep stop phase and conservatism....

    however, studies have shown that actually the theory of Deep stops does not actually work, and as such the standard used (historically speaking) GF's of around the 20/80 or 30/75 areas are actually starting the stops too deep.... and there is valid research that suggests the first stop should be shallower.... using GF low in the region of 50-60....

    But honestly, I would recommend watching the video... it is well enough put together to hold interest, and there is valuable information within in.....

    At least that's my interpretation (in a nutshell)
     
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  11. Colliwobbles

    Colliwobbles Active Member

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    Cheers for that Stu. I'll have a read tomorrow.

    I'm running 30/85 at the moment but have read about increasing the low gf to between 50-70 may have benefits.

    The deep stop argument is one that will be gong on for some time I think!
     
  12. Dave Whitlow

    Dave Whitlow Well-Known Member

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    Looks like you'll be out a bit quicker than me then. Mine are set to 50/80 with an alternative GF of 80/100 if something feels urgent. Hopefully nothing will feel urgent.
     
  13. nickb

    nickb Active Member

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    Weren't you clearing your deco before me most of the time? Have you changed your settings?
     
  14. Dave Whitlow

    Dave Whitlow Well-Known Member

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    yeah, but I have decided a lower GF high might be good for me.
     
  15. nickb

    nickb Active Member

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    At your age, I agree
     
  16. Dave Whitlow

    Dave Whitlow Well-Known Member

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    :p
     

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