"Controlled" Buoyant Lift

[jw2013]

I wonder if anyone can help?... PLEASE...?!


I'm in the LAST part of my Open Water and just cannot clinch it because of my Controlled Buoyant Lifts. In the words of my instructor, "they're buoyant but not controlled". In a pool (at 3.5m) it's not a problem. At 6m in open water, I am having problems controlling the lift.


My casualty this past weekend was in a Dry Suit, 15kg of weight and I was using his BC to lift him. I'm in two wetsuits and carrying 12kg. I dump all the air from my BC and monitor my Dive Computer on the ascent.

I'm having to pump a ton of air into the casualty's BC to get him moving, then as he starts to lift, I begin dumping the air but around 5m to 3.5m the lift seems to accelerate slightly; once above this it seems to be too late to recover from the lift as the air expansion begins to lift us both too rapidly to slow enough to be deemed a controlled lift.


Does anyone have any advice or tips? I have another pool session tonight and another open water dive this week (before my holiday) so I need to get this nailed in the next open water session in order to dive abroad :\


Thank you for your help!!
Jonny

 

[Qasar]

Well Jonny, the pb is with the weight and the shallow depth of your CBL training.
You need a lot of air to start moving, but then you don't have enougn time to dump it before gaining enough speed to be "uncontrolled".
The solution is with a very careful usage of the casulty BCD. Put first enough air to have him vertical (very slowly), then try to swim up to start the lift. Add eventually very little by very little air at a time. Don't try to start the lift only by putting air in it. Use your fins to strat, then be ready to dump once moving up, but if you use your fins to move up it should be easier to manage.

 

[jw2013]

Thanks Qasar!
I was doing this in the pool but got told never fin up on a CBL. Use their air only (or mine for an OoA CBL) because if I rely on this, at depths this could be a real problem.

Do you find this?

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[Qasar]

Yes, that's right. My advice covers the start of the lift, but once a little away fromn the bottom you need to be at least neutral buoyant, then when moving up it will be positive and you will need may be to dump.

 

[Hickdive]

By dumping all your own buoyancy you end up having to lift not only your casualty but yourself. That is why you're having to pump a lot of air into the casualty's BCD.

Remember that things take time to happen underwater. Putting a lot of air in one go into the casualty without waiting to see the effect, will mean you can often over-inflate and be too buoyant before the casualty actually starts to move, this is made even worse if you're effectively trying to lift two divers with one buoyancy device.

So, don't dump your own buoyancy before you start - just make sure you are neutral.

Add small amounts of air to the casualty's BCD and see what happens before adding more. Squirt, pause to see if they lift, if not another squirt and pause until they start to rise then stop adding air. Be aware that once the casualty actually loses contact with the bottom they may stop again, in which case go through the squirt/pause process again.

You'll have to dump some of your own buoyancy, as well as the casualty's, on the ascent. As long as you maintain a grip on the casualty this shouldn't cause a problem. Just make sure you only dump small amounts at a time, dump too much and you'll drop back down

I assume you're doing the SAA course?

 

[jw2013]

Hi HickDive,

Thanks for this. I am doing BSAC Ocean Diver (the first level) and they teach to use the casualty only to lift.

We ate always kneeling on the bottom to begin with and make the start from there. It is so frustrating - my instructor is deliberately choosing casualties who may pose a problem which I think is great (I don't know who I may have to lift and when) but as its a difficult skill to master its becoming annoying for me.

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[Subcooled]

Don't make the casualty too buoyant too fast. Add small amounts of air, wait to see the effect, then add more, repeat - just as explained above.

Don't make the casualty buoyant but neutral only. Then with a tap of a finger, send him/her up, like a balloon In reality, of course, you need to grab the BCD and the corrugated hose and stay close and dump but you get the idea.

If the speed starts to increase and you don't have time to dump fast enough, then you could exhale and loose 3 kg worth of lift instantaneously. Do this early enough. Exhaling is a good idea every time you think you go up too fast. Your lungs comprise a large BCD with quite an effective dump This should give you some time to dump more air from the casualtys BCD, and then slowly inhale as gas is escaping the wing.

 

[Agility]

The victim is in a dry suit so make sure the vent is fully open and (assuming the vent is on the left shoulder) roll the victim slightly to his right side. start venting air as soon as you are moving up. If the ascent gets too slow inhale instead of putting more air in the BCD.

 

[Hickdive]

Ah, your reference to "Open Water" mislead me.

OK, there's no easy way to say this but your BSAC instructor is wrong. As a BSAC trainee you are NOT trained to dump all your buoyancy prior to starting the lift.

If your instructor is teaching you this then he/she is teaching you incorrectly and making the skill harder than necessary.

Ask him/her to review the lesson in their DTP notes and show you where it states that the rescuer needs to dump their buoyancy before commencing the lift.

In addition they need to bear in mind that as an Ocean Diver you're not expected to demonstrate perfection at this stage. You're only lifting from 6m. When undertaking SD and up you'll be lifting from deeper and expected to have sufficient control to stop the ascent at 6m to comply with the BSAC88 tables.

Of course I should qualify this with the caveat that it is a couple of years since I was a BSAC Instructor Trainer/Examiner and the current senior hierarchy at HQ have some bizarre ideas but I don't think this will be one of them. We used to have to "train out" some of these numpty ideas when instructor trainees turned up on IFC or OWIC. The worst offenders were usually people from branches who had had minimal exposure to nationally run events via the ITS. It was so bad that in-water AV was compulsorily one of the pool sessions on IFC because the general standard of teaching and performing the skill was so low!

It is also worth bearing in mind that BSAC branches and instructors do not have the authority to add or subtract from the DTP.

 

[jw2013]

Sorry HickDive. We refer to it as that as it's literally in open water.

The dumping of my air was a recommendation from another instructor, not mine but something I tried.

Tonight (in the pool, from 3.5m) I successfully did 3 CBL's. Typical! First was with two casualties, then with two casualties without a mask (the best I've done ever apparently!) and a third (with a mask) lifting 3 casualties.

...but I struggled with ONE in the open water!

I had a chat tonight with my instructor and he has given me more advice to go with that offered here and I need to try again on Thursday evening!

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