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Can anyone suggest a computer for returning to altitude after a dive

Discussion in 'Computers, Gauges, Watches and Analyzers' started by kirstyjay, Jan 19, 2020.

  1. kirstyjay

    kirstyjay Angel Fish

    # of Dives: 0 - 24
    Location: Tenerife, Spain
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    I've been looking through most of the Scubapro ones over the past few hours and they all seem to have some sort of display for altitude classes, even the more basic aladin models, so that's reassuring. I realise that it may not be something I really need to worry about straight away, but my drive up to 600m is quick... in 10-15 minutes. I live on the side of a volcano. So, it was something that concerned me. I feel a lot better about it now. I have 5 mins in the rib back to shore, 10 mins getting all the kit off the boat plus another 30 mins having a shower and changing before the 10 min walk back to the car, so I should be ok. I'm still a bit overwhelmed with the choice of computers out there, but at least I know I can find one that has what I want.
     
  2. Angelo Farina

    Angelo Farina Marine Scientist

    # of Dives: 1,000 - 2,499
    Location: Parma, ITALY
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    Your case is peculiar, as you live at an altitude. So your amount of nitrogen which is stable in your body is smaller than the amount which people living at sea level have.
    In practice you start your dive with less nitrogen than your buddies, and hence at the end of the dive you will have slightly less nitrogen in your body than what your computer evaluates.
    This is particularly true for the slowest tissues. This provides you with an additional safety factor, which I suppose the computer is not evaluating. So, if the computer says that you can climb up to 700m, do it without fear, you are on on the safe side.
     
    kirstyjay, markmud and KWS like this.
  3. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
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    Your tissues are like 4 minute for the fast one that that will be 2-4 half lifes 6 is considered all you need for full adaptation to the new pressure. The first it as much as the last 5 periods combined I dont think it is possible for you to drive up a steep enough road fast enough to out run the off gassing process. in 8 minutes if you went form 0 to 800 meters you tissues will be at 600. A 200 meter difference is nothing. If you are concerned dive nitrox.
     
  4. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
    4,484
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    Hers another way to look at it. the max tissue pressure difference from lake side pressure is 1 atm. so your tissues can be pressured to 33 ft and your body is at the surface that is a 2 atm to 1 atm ratio which is the max that really applies to you. Perhaps that is a bit confusing but one atmosphere in the air is perhaps 60 thousand feet so if you were fully off gassed at sea level, you would have to go up to 30 thousand feet to again hit that 2:1 pressure difference to have a problem. Now lets look at how much effect 700m or 2000 ft is it is about 1/30th of an atmosphere difference. so you hit the surface and pack and head out in say 30 minutes. you tissues are perhaps at 1 foot water pressure or 1.03 atmospheres. and you teleport to 700 meters or 2000 fr and the atmosphere pressure drops from say 1 atm to .9 atm. now you have a ratio of 1.03/.9 that is at worse a 1.1 to 1 ratio and you are allowed up to a 2 to 1 with out having DCS issues. Now if you want you can suck up some nitrox for a few minutes on the surface or dive with it you could speed that up. NO matter what It will not have a problem. BTW when astronauts go to space you see them with a suit on and carrying a ac pack. they are breathing pure O2 so that they have almost nil N2 in their system. They do that because of the extreem altitude pressure change when they take off in a very short time period. they are going form 1 atm to practicaly a potential 0 atm in the matter of a couple of minutes. they breath O2 to prevent the bends from the large altitude change effects on nitrogen. Your 2000 ft change is really a non issue. grab a lunch before going home and relax.
     
    kirstyjay likes this.
  5. GJC

    GJC Solo Diver

    # of Dives: 100 - 199
    Location: Southern California, USA
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    It really depends on what dives you are doing.

    If only doing 1 dive to 60 feet for 45 min. You can safely ascend to 700 m without delay.

    If you are doing 3 dives in 1 day, you can absorb enough nitrogen that would require a 6 hour delay before your ascent.
     
    KWS and kirstyjay like this.
  6. BoundForElsewhere

    BoundForElsewhere Ah-Muzen-Cab ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: New York, New York
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    Could you use some variant on an altitude dive function to figure it out?
     
  7. Michael Jastrzebski

    Michael Jastrzebski Nassau Grouper

    # of Dives: 200 - 499
    Location: Oakland, CA
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    This is what I like about Shearwater - if something can't be reliably computed it isn't shown, as with flying after diving, offers absolutely no guidance.
     
  8. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,662
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    I might amend that to, "...if something can't be reliably predicted, it isn't shown..."

    The more I think about this (not for the OP, I think her situation is pretty safe), the more I think watching GF99 in real time as you drive up to altitude might be the way to go. I'll have to try this with my Perdix and see what functions remain active during the surface interval. Certainly the tissue map will, and I think GF99 will.

    Anyone care to debate whether tracking GF99 to stay below (say) 70 would be a good way to protect yourself as you ascend in altitude during the surface interval?

    I think I'll post a question in the Shearwater thread and ask them...
     
    markmud likes this.
  9. Michael Jastrzebski

    Michael Jastrzebski Nassau Grouper

    # of Dives: 200 - 499
    Location: Oakland, CA
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    Yes, you should and come back here with their reply.
    Your method sounds reasonable to me however it is predicated on their software updating the GF99 once out of the water, so double checking with them is important.
    I do have the Teric and imagine I am in the (ideally) ..watch mode and drive up the mountain and Teric would warn me when my GF99 gets high enough.
     
  10. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    kirstyjay likes this.

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