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Find the screw-ups

Discussion in 'Rebreather Diving' started by rjack321, Jul 31, 2019.

  1. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    8,638
    2,526
    113

    yea thanks

    At min 66 and 67ish it looks like he descended and added dil to compensate. adding volume which is only 18% o2 when shallow is going to drop the ppo2
     
  2. vitaly

    vitaly Angel Fish

    # of Dives: 500 - 999
    Location: SF Bay Area
    39
    6
    8
    Petrel Firmware v53... Time to upgrade to v65 :)
     
  3. JonG1

    JonG1 Nassau Grouper

    # of Dives: 2,500 - 4,999
    Location: Glossop UK
    73
    20
    8
    It's a Kiss Classic so MCCR, not sure about PPO2 at start of dive, at the end the chop was running and perm shot on wreck was a pogo stick.

    I should have stuck a Jon line on it or bagged off, clearly my buoyancy was crap!

    There was a negative outcome for me on this dive...any guesses?
     
  4. JonG1

    JonG1 Nassau Grouper

    # of Dives: 2,500 - 4,999
    Location: Glossop UK
    73
    20
    8
    ADV must have fired at 66/67 crashing the PPO2, switch it off now at about 15m
     
    rsingler likes this.
  5. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    8,638
    2,526
    113
    second dive of the day, modest SI, not terribly deep, short deco
    Im at a loss trying to divine what this profile is a problem though?
     
  6. ChuckP

    ChuckP Manta Ray

    # of Dives: 200 - 499
    Location: Cozumel
    503
    319
    63
    Here's two dives from class, three screenshots from the first one and two from the second. Using shearwater desktop you can see what your TTS is doing and calculate your ascent rates.

    Shallower dive I did the gas switch on the fly, primary reg free flowed and it wasn't pretty. Deeper dive the next day, I had no intentions of switching on the fly - I switched when I hit my stop.

    The screen shots show that with all that added complication on the shallow dive - per my computer, I gained two minutes deco - the deeper dive, slightly slower ascent rate, "late" gas switch, I gain 4 minutes of deco.......

    Is plus 4 minutes that bad if you don't mind spending the time?

    My question revolves around different motives, different diving style. Those were classroom wreck dives, I dive warm water drifting reef dives. We've dove a lot lately in the 100-130' range, plans based on gas and limiting TTS to no more than 10 minutes - our ascents are slow. TTS gets to say 8 minutes, we head shallower gradually and may spend another 40-60 minutes in the 70-40' range. First stops are almost always at 20' by the time you get there. We may carry more gas and extend to 150', similar type profile with the slow ascent - are we really being that bad to ourselves with the slow ascents? GF Lo is 45 now, Hi is 80 but I'm usually out of the water at 75..........
     

    Attached Files:

  7. huwporter

    huwporter DIR Practitioner

    # of Dives: 1,000 - 2,499
    Location: Sydney, Australia.
    211
    178
    43
    Second dive of the day, not sure what the first dive looked like, but this one was 'relatively' long and shallow so more slow tissue loading. You could have been bubbling on the ascent, was the bouncing up and down at the 6m stop enough to provoke a type 2 hit?

    Thanks for putting it up.
     
  8. rjack321

    rjack321 Captain

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    8,638
    2,526
    113
    Oh @ChuckP I see what you mean. Although your class ascents look around 25-30ft/min to me which is great.

    I dont mind a multileveling dive at all. In fact there were a few dives on the trip from the screen shots I posted that would have been better as multilevel dives. That is we tied into a mooring at 78ft and swam down 250ft (horizontal) to the stern of the wreck at 180ft deep then swam back. Sounds good until you realize that the bow of the wreck ended at 25ft deep. Why no moor to that and swim the length and blow off deco as you twiddle your way up? I'm all about seeing stuff as you blow off deco.

    But ascending up a line from 240ft? I wanna get off the bottom and into my legit offgassing zone close to the model rate, 15-20ft/min is common in my experience (really slow though). When there's a problem like OOA it really haunts you because all the rock bottom calcs are done based on faster rates. And your deco gas is all budgeted for a certain amount of deco. Adding 5 mins doesnt sound like much but 5mins longer at depth than it should be in good conditions can make a bad day a tragedy. Its also just loading up your intermediate tissues with for little or no measurable value.
     
  9. JonG1

    JonG1 Nassau Grouper

    # of Dives: 2,500 - 4,999
    Location: Glossop UK
    73
    20
    8
    Bang on huwporter. The wreck was pretty broken up so I was running a reel and diving tanks left so left arm was working relatively hard keep line out of bottles.

    Took a mild pain only in left shoulder.

    Very cautious with stop depth now.
     
  10. JonG1

    JonG1 Nassau Grouper

    # of Dives: 2,500 - 4,999
    Location: Glossop UK
    73
    20
    8
    Rjack, I aim for 9/10m a min but if there are divers on the line it can look a bit out of control so you end up compromising.

    I pad the shallow anyway but computer should adjust stop times too surely to compensate for greater loading?
     

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