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Air sharing on ascent

Discussion in 'Basic Scuba Discussions' started by Deefstes, Aug 25, 2008.

  1. Deefstes

    Deefstes Loggerhead Turtle

    # of Dives: 100 - 199
    Location: Johannesburg, South Africa (not close enough to th
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    I'd like to get your thoughts and advice on air sharing during ascent. Let me start by explaining where I'm coming from.

    This weekend my wife and I decided to do some skills practicing at the local quarry. We wanted to look at some basic trim issues etc. but also to do air sharing while doing a free ascent with a 3 minute safety stop at 5m.

    What a disaster! We started our free ascent at 15m and as soon as my wife took my octo, she became a cork. I'm sure it has nothing to do with using my octo but just that she forgot to mind her buoyancy. I grabbed her by the fin and pulled her down and at the same time dumped all the air from my BC. We must have been at around 10m by the time our upwards movement stopped and I'm surprised that our computers didn't complain of ascent rate violations so it couldn't have been too bad. By now she's realised what happened and she dumped all her air as well and before we knew it, we were back to 15m.

    After some heavy finning and air additions to the BC's our buoyancy was sorted. OK, so we started the intended ascent. Things seemed fine although I think it could have been better. We didn't really ascend steadily but rather bobbed up and down with a net upwards movement, probably not ideal but not catastrophic either. The same thing continued through the safety stop and our 3 minute stop constantly varied between 4m and 6m.

    If this was a real life emergency I think we'd have survived, even without harm. However, in a real life emergency at least one diver will probably have been much more panicked and things could have been much worse so I think we'll go back and practice this again until we get it right.

    Now, your help and advice please.

    1. Throughout the exercise, we were in the vertical position. Sorting out our bad buoyancy would probably have been easier if were horizontal but in a real life emergency I'm pretty sure at least one diver will not remain horizontal. Your thoughts? What is a good position for an air sharing ascent?

    2. Keeping on the topic of body position, I found that donating an octo made things pretty tricky. We had planned on grabbing each other's BC's with the one hand, facing each other but the awkward looping of the octo hose made that, well, awkward. So we ended up being almost side by side, her to my left. Again, what is the correct way?

    3. Both of us kept a close eye on our computers throughout, mostly to keep a tab on our depth. We both had the same computer but even so, they didn't give he exact same readings all the time. So while she thought we we're at 5.4m, I thought we were at 4.6m (this is probably because of the 20sec sample interval). The thing is I'd be trying to get us deeper while she'd be trying to get us shallower or vice versa. Would it perhaps be a better idea for both of us to keep an eye on just one of the computers?

    4. Would it not perhaps be a good idea for only one of the two divers (the one who is not OOA, ie. the donating diver) to manage the entire ascent? In other words, the receiving diver has only two tasks, keep the donated octo in your mouth and hold on to the donating diver's BC. The donating diver then makes sure the collective buoyancy is correct and manages the safety stop, monitors the computer etc.

    What else can you gurus tell me? I think this might be a valuable skill to master and once we have this one down pat we'll move on to buddy breathing during free ascent with a safety stop.
     
  2. El Orans

    El Orans ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: The Netherlands
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    I prefer to do my free ascents with an SMB. Having a reference makes it easier to maintain your depth allowing you to focus on the sharing of air.
     
  3. spectrum

    spectrum Dive Bum Wannabe ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: The Atlantic Northeast (Maine)
    11,342
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    #1 Unless the buddy team has practiced horizontal you are probably correct.

    #2 This is why I have my alternate second stage on my left. It presents properly to a donor that is face to face or swimming to my left.

    #3 The sample rate refers to the data that is logged for download. The display is real time.

    #4 Just like while diving somone needs to be driving. Let the "victim" be the follower, that is probably the more stressed diver. The donor will also be the one with ready access to inflator air if too much gets dumped.

    Congratulations on making time to practice this sort of stuff.

    Pete
     
  4. battles2a5

    battles2a5 Divemaster

    # of Dives: 200 - 499
    Location: Charlotte, North Carolina
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    There are a few things happening in this scenario (both in practice and in "real life"):

    1. Recreational configs are not set up very well for air-sharing or air-sharing ascents. They are designed to get you air and get you up to the surface. It is difficult to share air horizontally with rec-length hoses. When you go vertical to share, your bouyancy is going to change a bit and that doesn't help things.
    2. IIRC, your wife is a new diver. First on all, good for you for continuing to practice skills and OOA after your training. Second, it is natural for newer divers to increase their breathing and to breathe higher into their lungs during drills. So this is going to increase your bouyancy. This just takes some time to get comfortable with taking the reg out, being conscious of your breathing, and just being comfortable in general.
    3. Once you realized you were ascending, you probably over-compensated with your responce to dump air, hence the bobbing up and down. It also sounds like you began the ascent right away after you started sharing air. I would suggest breaking the drill down into part. For instance, donate the reg then stop. Wait a few seconds and make sure your breathing and bouyancy are ok. "OK" eachother then begin the controlled ascent. That may help.
    4. The one donating the reg should be controlling the ascent. If the receiving diver is OOA, they don't have any air to inflate the BC. They should be venting on thier own during the ascent but you should be prepared to help them, especially in a face-to-face vertical ascent.
    5. Not sure where you are practicing this, but "free" ascents without a visual reference and difficult for everyone, not just new divers. Maintaining depth and a controlled ascent rate is a challenge and requires a LOT of practice to master. This is compounded by the OOA drill. You want to do this on an upline or a wall, or somewhere else where you can maintain a visual reference.

    Hope this helps! Keep up the good work with the drills.
     
  5. danvolker

    danvolker Dive Shop

    # of Dives: I'm a Fish!
    Location: Lake Worth, Florida, United States
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    This is one of the foundational points to why you should consider DIR for recreational diving. If you and your wife were each breathing through a long hose primary, with the necklace reg back up, the drill would have played more like this :
    1. On ascent start at 15m , you pass your long hose primary to your wife, with you switching switching instantly to your necklace reg.
    2. You are now swimming comfortably side by side, not bumping into each other, or even slightly hampered--it is exactly like being on your own air supply, and swimming in a buddy formation.
    3. You ascend with the "normal" ascending skills you are capable of--both of you. Without the stress of short breathing hoses and your buddy bumping into you and being unable to swim with the short octo---the DIR config makes this ascent feel incredibly easy.
    4. You should end up at the surface , in exactly the way you normally would....
    ***note*** in a real world use of air share, the DIR diver, seeing his buddy/wife at a low psi ( say 400 psi to his 1200 psi) would shove his primary over to his buddy, and they would both begin the ascent. At the surface, once you get close to the boat, this will mean your buddy can go back to their own air, for the final moments of exiting the water, where buddy breathing is more cumbersome.

    Regards,
    Dan Volker
     
  6. TSandM

    TSandM Missed and loved by many.

    # of Dives:
    Location: Woodinville, WA
    36,350
    13,498
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    First off, big kudos to you and your wife that you are practicing this stuff!

    I think what you just learned is that executing a well-coordinated air-sharing ascent is not a trivial task. Can you imagine how that would have gone, had one of you actually BEEN out of gas? THIS is why practice is essential. If the procedure is smooth and stress-free in a practice situation, it's more likely to go well when it's needed.

    The problem with doing an ascent in a vertical position is that every movement of your fins drives you upwards. So you can try to do the ascent negative, and swim up, but that's difficult to calibrate, especially if a good part of your attention is being used up by maintaining the airshare. Doing the ascent in a horizontal position means you do the ascent close to neutral, and especially if you are diving a drysuit, you can vent it while maintaining the air sharing. (This still requires practice!) But the problem with doing an air-sharing ascent while horizontal is that it's difficult to impossible to do it if you are sharing a 24" hose or a 36" hose. This is why a lot of people go to a longer hose (40", routed under the arm with an elbow connector, or 5', or 7').

    As far as who controls the ascent, the diver with gas should be the one monitoring depth and calling the stops, because he's unstressed (assuming there are no other tasks to be done while ascending). But each diver should control his own buoyancy. Somebody's already made the observation that the OOA diver has no power inflator, which is true -- but if he over-vents, he CAN orally inflate (another skill nobody practices).

    Finally, it's my experience that depth gauges aren't terribly accurate, and no two read precisely the same at a given depth. If one diver is calling the deco, he says, "Level off HERE", and it doesn't really matter if the other diver's gauge is at 10 feet or 12 feet or 9 feet, that's where you level off and stay.

    Again, this is wonderful that you guys are practicing this stuff, and as you solve the issues, I think you will find the polished skills that are required will be reflected in your normal diving, as well.
     
  7. Theunis

    Theunis Barracuda

    # of Dives: 100 - 199
    Location: Pretoria, South Africa
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    Hi Deefstes, you have received good advice from the members. The one donating the octo will not always control the ascent. You will find that the more experience diver will tend to take over control of the ascent.

    The secret is to control the ascent by controlling your buoyancy. You should try to use your BC as little or as conservatively as possible. For me it's the easiest to do the ascent in a vertical position with my buddy facing each other especially in an emergency situation. This works great when you are sharing air with one reg or where your octo hose is too short.

    You and your buddy should rather be a little negative than positive buoyant as well. It's better to have a slight finning action to neutralise negative buoyancy than having a battle with positive buoyancy. When you get to your safety stop depth you can fix your negative buoyancy by conservatively inflating your BC.

    Remember, practise makes perfect!!
     
  8. Blackwood

    Blackwood DIR Practitioner

    # of Dives: 500 - 999
    Location: Redondo Beach (SoCal, not Washington)
    5,537
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    IMO, it's better to shoot for dead nuts neutral rather than slightly negative or slightly positive. Err on whichever side you feel is more cautious. If you're over a 4000 foot floor, positive may be more cautious than negative.

    Definitely. I prefer to do my ascents and descents horizontally, as it's much easier for me to control when drag is working in my favor. However, whatever you and your buddy decide to do, practice it often.
     
  9. Teamcasa

    Teamcasa Sr. Moderator Staff Member ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Near Pasadena, CA
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    Like others have said, kudo’s for doing the drill.

    Just a few more thoughts. Doing a open water, no line assist stop is difficult for many divers even when they have plenty of air and almost impossible if one is panicked and out of air. Again, practicing is the best method to manage the panic factor.

    Despite running the risk of being flamed, I’d advise you to practice holding the stop while sharing air in a vertical position. It is much easier. You can watch each other face to face, keep close, hold on to each other and control the stop and assent, further reducing the panic factor. Besides, should you ever have to do this for real with someone really OOA that has not trained with you, chances are they will be vertical and heading directly up to the surface. You will need to be the calm one, control the assent and instill confidence right away. Face to face helps with this. (Oh and take a rescue class together.)

    Since, like me, your primary dive buddy is your wife, you have a big advantage. Practice and you both will eventually get this skill honed to perfection. While getting this done, and when doing your normal recreational dives, continue practicing the open water, no line assist stop in the horizontal position until both of you have that skill nailed. Then, add in the air sharing until it is also second nature.
     
  10. String

    String Master Instructor

    # of Dives: I just don't log dives
    Location: Grand Cayman
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    If using standard length octo hoses face to face and vertical is about the only way the hoses will reach.

    Consider mounting the octo so it comes from your left. That way its the correct way up for the buddy without having to loop the hose. Those few extra inches help a lot.
    I always use and teach grabbing the BC straps - i HATE the insecure roman handshake thing that so many people seem to do these days. Both should be securely grabbing each others BCs and hold each other close - too far away and its hard to not wobble all over the place.

    Unlikely - sampling interval is for downloads only - they update once a second or so on a dive but only store snapshots at 20 seconds or whatever its set to. Very few computers read the same but most are only out by 20-30cm not that much.

    Neither. The stop depth is not critical. Just get to somewhere you are both happy then signal stop. Then one of you watch the depth, the other base the position relative to the other diver without watching a computer at all. Constantly "chasing the needles" causes bouncing.

    The guy with air dictates it to an extent but the OOA diver will still need to dump from their BC and suit. The way its done here is the with-air diver has the computer, is responsible for the rate and so on, the OOA diver is responsible for staying level with the guy who has air (by looking at him NOT the computer).

    Also worth noting that if it had been real after all the air had been dumped and you both ended up back at 15m your OOA buddy would not in the real world have been able to inflate their BC easily to get back off the bottom.

    Try this a lot and shallow until comfortable before doing any more diving - if you cant manage a practice OOA ascent with no stress at all its not real safe to be there.
     

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