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Ditching run time

Discussion in 'Hogarthian Diving' started by lefrogster, Feb 27, 2014.

  1. ajduplessis

    ajduplessis Solo Diver

    # of Dives: I'm a Fish!
    Location: dry land :-(
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    Firstly, gas switches are very basic tasks and if you find them stressfull you should not be doing these type of dives. Work on your skills like switches and the other poor examples you described. You should be able to do these without a mask and on the move. If you can't do this effectively how are you going to deal with it when things go south.

    The idea of being "forced" to stick to the dive plan is whole idea!! If you cant dive a run to the number , you are in for a serious suprise. You are masking your shortfalls by relying on your computer.

    Work on your skills and start to dive only with a BT and slate. This will force you plan better and work on the gaps....
     
  2. mathauck0814

    mathauck0814 Assistant Instructor

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    I'll start by saying that this entire thread is very scary.

    As part of the predive check, on the surface, computers should be on and verified to have all appropriate gasses set. In fact, all of our team members dive the same computer so that we can keep results as uniform as possible.

    During the working portion of the dive, it's acceptable to have some reasonable amount of separation, but not on critical events like ascents where you're supposed to be working together.

    These are skill problems.

    This is exactly why I (and everyone else I think) teach students to have a next/deeper/longer plan, so you don't have to ask the question, but know the consequences of overstaying. This is what gives you a nominal amount of freedom to handle unexpected minor failures.

    For major failures it helps to be grounded in ratio or deco on the fly or very good (and redundant) computers.
     
    wedivebc and TSandM like this.
  3. tom_n_tacoma

    tom_n_tacoma Dive Shop

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    The main two things that got me into Tec diving were the ability to find cool **** beyond the reach of other recreational divers and the mission planning aspect of it. I've done both TDI and PADI Tec training and run times, following schedules, etc., were all part of the mission planning, which is also part of safety in this type of diving. If you cut your tables in vplanner or whatever and they say you leave the bottom at 22 minutes, then you ought to be leaving the bottom at 22 minutes. You can do alternate tables in the software and see what an extra 5 minutes will do to your overall deco time, gas consumption, etc. You can also pad your stop times for the gas switches so if you need to be at 70ft for 3 minutes for a switch then you can do that. You can also have your other hose out on the way there, turn on your gas when you get there, check buddies and switch to speed it all up. If I dive with someone, and they're not into following the mission, schedule, run time, etc., then they dive with someone else. Its that simple. Lots of good points made in this discussion so far, I like the example of the blown dive where the wreck was not there so they didn't have the bottom time anticipated and still hung at 150 for a long time. You can cut extra tables, put them in your wetnotes or where ever, or do some math, and be able to compensate for things on the fly if you have to. To me it is all about practicing the skills, all the time, then you get better and better at them. Then run times don't seem to be an issue.
     
    Micksherryn likes this.
  4. lefrogster

    lefrogster Angel Fish

    # of Dives: 100 - 199
    Location: Hong Kong
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    I see that this thread has really grown! Great!

    Just to clarify a few points:

    - I don't favour ditching run time to follow a computer. I don't use a computer at all, just a bottom timer. I do all my dive planning on SW.
    - I'm also not in favour of ditching dive planning: if you plan 60m for 15 min, then you dive that plan. If you overstay or go deeper by accident, then you follow your backup contingency plans (which you should've already printed).

    I'm in favour of ditching run time and using stop time only for deco stops. Stop time is the actual time you are breathing your deco gas. This allows the team to do sequential rather than simultaneous gas switches and handle any contingencies that might arise. It isn't because I don't feel confident in my skill in doing a gas switch -- I accomplish this smoothly in about 10s.

    If most tec fatalities during deco are due to mistakenly switching to O2 at 21 m, then I don't see a problem spending a little more time at the stop to do the switching sequentially so your buddies can monitor. In a recent dive for instance, my buddy was surprised by a sudden massive leak and bubbles during a gas switch. I could see quickly that it came from the first stage attachment that become loose during the dive and we fixed it right away. Nothing serious, but having a buddy watching helped. So a normal 10s switch took us about 30s during this 2 min deco stop.

    We counted the 2 min stop from this moment, so the actual stop duration was 2min 30s, skewing the remaining run time schedule. It was more important for us to do the complete 2 min on deco gas, rather than cutting it short to 1 min 30s just so we can stick to our original schedule. And if something else happens on the other stops, skewing run time by another 20s, etc, it doesn't matter as long as we stick to the actual stop time we are breathing gas. This is just the 'padding' described in the previous post, and I agree with that. At the surface, we are usually no more than 1-2 min later than the original run time surface schedule. Those extra minutes don't do much in terms of extra gas consumption or where the boat picks you up, but it does give you extra time to handle in-dive contingencies.

    I think its much better to ensure you are breathing your deco gas for the planned time rather than being at a certain depth at a certain time, especially if it means cutting short your breathing time just so you can meet the run time schedule.

    Unexpected things can happen during deco, and you might need a little extra time to stow a DPV, get out of a down current -- on another recent dive we got attacked by big Titan fish protecting their territory. These aren't related to poor skills but the unexpected conditions that can occur in any dive.
     
  5. Diver0001

    Diver0001 Instructor, Scuba

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    I'm lost.

    Aren't you over thinking this? All I've ever done is make 3 schedules. The target schedule, the +5 min schedule and the +10 min schedule (or whatever makes sense) assuming it all fits within gas planning etc.

    For me, learning deco diving was a *release* from time pressure because it allows for so more flexibility. Doing stops deeper than the ceiling is just a SOP that gives you a way to strickly control ascent speed. It's completely natural and completely fluid once you practice it a bit. I'm having trouble understanding why someone would feel time pressure because of that.

    R..
     
  6. lefrogster

    lefrogster Angel Fish

    # of Dives: 100 - 199
    Location: Hong Kong
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    The +5 or +10 min slates are for overstaying bottom time. I think that's fine in addition to slates if you go too deep.

    My question is about deco stops, and what the contingency plan is if there is any delay in gas switch with someone in your group. I think the group should overstay that stop to ensure that the late guy breathes the required gas for the required duration, rather than having the group ascend to the next stop just to stick to the pre planned run time.

    Once I started doing this, I felt much more liberated and free of run time pressure.
     
  7. Diver0001

    Diver0001 Instructor, Scuba

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    Don't look at it as as overstaying. The gas switch is just a task and it takes as much time as it takes. If you have a group that can't do that in less than a min then just extend that stop for another minute. If you think this situation will apply to you then you could opt to leave the bottom a minute or so early so you don't have to worry about extending the stop causing additional on-gassing that you didn't account for.

    See the difference in mind-set when you say extend as opposed to overstay? One is something you choose to do and account for. The other is something that happens that puts you in time pressure.

    Moreover you know (or should know) from your deco theory that if your target ascent rate above 21m is say 3m/min that you can increase that to 10m/min without penalty until you reach your first required stop. So if your ascent is falling behind your clock then just roll through one or two stops to get your time and depth back in synch again. There's no real reason to go to a longer schedule unless you're so far behind your clock that you can't re-synch at 10m/min.

    As for just doing "whatever", until you get to your first mandatory stop (how I read it, is this what you meant?) ... I wouldn't be in favour of that. As I said before, the deeper stops are all about controlling your ascent rate and controlling your ascent rate is essential to your safety. The required stops are based on a certain ascent rate and you want to know that you haven't gone over that at any point during your ascent.

    Once again, it becomes automated at some point if you do enough of these dives. Ýou'll find after a while that you don't have to think about it anymore, it will just become the SOP.

    R..
     
  8. Ste Wart

    Ste Wart Master Instructor

    # of Dives:
    Location: England
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    I used to use run times, but I'm alright now ;-)

    I started using Ratio Deco last year and it changed by diving. Deco become intuitive rather than controlled (ie from a program). I work out basic gas parameters in my head + an initial idea of the schedule then adjust that based on what happens during the dive.
    I enjoy being a thinking diver rather than a v-planner automaton.

    Sent from my couch using tapatalk
     
    lefrogster likes this.
  9. lefrogster

    lefrogster Angel Fish

    # of Dives: 100 - 199
    Location: Hong Kong
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    I think this is what I've been trying to say. I'm in favour of making a choice to extend the stay to take the time needed for any contingencies, or if you want to do gas switches with your buddy sequentially. As long as its in a controlled and deliberate manner, I think it is fine.

    But I've dived on a few trips with divers that would consider this as overstay and a sin, because they value respecting run time above all else. Procedures seem rushed, and there is constant time pressure and timer-checking. I don't think that kind of to-the-second rigour is necessary especially if it can cause problems rather than resolve them.

    I don't think I meant to say this in this manner.
     
  10. Diver0001

    Diver0001 Instructor, Scuba

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    I think what you want to do is perfectly acceptable within boundaries. I think I can explain in more detail when it's ok to extend a stop and when you should delay extending it until you're shallower within certain types of dives. However I don't have time right now. Remind me about this later on and I'll try to get my thoughts pixelated for you.

    R..
     

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