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Old 20 January 2012, 11:33   #41
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Originally Posted by dally View Post
"On this note, I am qualified "
as what exactly MrP ??
O level? Driving Licence? aaah "note", I have a Grade 1 Theory in music
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Old 20 January 2012, 11:53   #42
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Originally Posted by biffer View Post
The easiest thing to do as suggest is squat with your fingers in your neck seal. You don't want excess air in the suit if your wearing a life jacket
When you're diving air shift to legs can be a problem in the not so well trained and I've seen uncontrolled accents from depth and it ain't pretty.
Just get the air out to be on the safe side

sent from a remote device
That's two of you now who have mentioned from personal experience seeing uncontrolled accent with air shift to the legs in dry suits.
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Old 20 January 2012, 12:42   #43
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Quote:
Originally Posted by dally
"On this note, I am qualified "
as what exactly MrP ??

O level? Driving Licence? aaah "note", I have a Grade 1 Theory in music

you posted it, thought you might know,
obviously your advice on matters sub-aqua is something to be taken very seriously then.
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Old 20 January 2012, 12:54   #44
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That's two of you now who have mentioned from personal experience seeing uncontrolled accent with air shift to the legs in dry suits.
Aye & since when did personal experience count against armchair experts & sceptics
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Old 20 January 2012, 13:05   #45
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Lighten up a smidge Dally. If you look at my LR Defender opinions you'll see that everything is very serious indeed.
But it all depends on what it is that you're after Dally. My posts were based on personal military, instructing PADI (admittedly not the highest echelon of s.a.) and RNLI experience.
My ribbing nowadays is purely leisure and as such I respond in a leisurely manner, but the threads which touch on safety I trust are treated with a little less levity and focus on members' invaluable and broad blend of experience. This is why we're all here. To share, deduce and discover.
What was it you were after Dally?
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Old 22 January 2012, 07:06   #46
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Aye & since when did personal experience count against armchair experts & sceptics
It probably will!! but only if one of them ever experience anything like this....
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Old 22 January 2012, 07:49   #47
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to watch an upside uncontrolled accent is bad, you have to be real quick to stop it, just trying to reach upside down into a hole can start it off.
let see if i can get this right after all these years, what ever air you have in your suit will compress by half by the time you hit 10m, so to get your bouyancy right you add some more air to compensate, every 10m more you go down it halves again and so on.
if you go ballistic at 20m short of putting a hole in your drysuit you will not fin against the air expansion and lift it provides.
if you could drag a five gallon can to 30m it would only be a quarter of its size, like wise on the way up a five gallon can would probably explode as would your lungs and drysuit seals as the air quadruples in volume.
after all these years of diving i still wear ankle weights when sport diving, being feet light and losing my mask was always my pet hate
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Old 22 January 2012, 07:58   #48
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Quote:
Originally Posted by biffer View Post
to watch an upside uncontrolled accent is bad, you have to be real quick to stop it, just trying to reach upside down into a hole can start it off.
let see if i can get this right after all these years, what ever air you have in your suit will compress by half by the time you hit 10m, so to get your bouyancy right you add some more air to compensate, every 10m more you go down it halves again and so on.
if you go ballistic at 20m short of putting a hole in your drysuit you will not fin against the air expansion and lift it provides.
if you could drag a five gallon can to 30m it would only be a quarter of its size, like wise on the way up a five gallon can would probably explode as would your lungs and drysuit seals as the air quadruples in volume.
after all these years of diving i still wear ankle weights when sport diving, being feet light and losing my mask was always my pet hate
As I said earlier, I'm feet light too and wear weights. This whole bobbing about the wrong way up sends shivers down my spine. And that's even when I know about it, am expecting it, am trained to overcome it and have the kit to survive it.
Imagine if it came as a rather ugly, if quick, surprise.
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Old 22 January 2012, 08:48   #49
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In my kayaking days,we were taught to always to vent our dry suits because of the issue of air getting into the legs which could force your head under the surface. My personal thoughts on this, and they are not (scuba diving related) are YES... but more so... if wearing a BA, most of them are 50n and they do lose some buoyancy after a certain amount of time, unlike L J's. Also, as previously stated BA fit tight around the chest so there is more room for air in the legs. Now if you are wearing a LJ I don't think that would be an issue due to an inflated L J keeping your head and shoulders somewhat higher out of the water because of the extra buoyancy especially in the chop, now this is only my opinion. I do believe there was a video out on youtube some years back allegedly proving this theory wrong, but I can't find it, maybe it's been taken off.
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Old 22 January 2012, 11:00   #50
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Quote:
Originally Posted by captnjack View Post
You won't naturally hang head down. The natural position even without any kind of life jacket will be flat, either face down or face up. Just because some gas was pushed out of your torso does not make your chest negative/sink. There's still a good amount of positive bouyancy up there with your lungs and residual gas in the suit. It may take some time to shift flat way naturally or you can just help it along by doing a "situp" which is the the same as this ball curling motion. Its not at all difficult or unnatural.
Captnjack is indeed correct. Your whole body wearing a drysuit (neo or membrane) is positively bouyant, the fact that most of the air is in the feet doesn't mean the rest of the body sinks just means the feet sit higher, you will float horizontal even entering the water head first. If it wasn't the case I wouldn't be here. To test, put on a drysuit and float head up. To keep this attitude you have to splay legs and arms. Put your arms and legs together at your side and you'll go horizontal, usually face down as your knees tend to bend slightly. 30 years of drysuit diving wearing more neo and membrane suits than I care to remember. Anyone experiencing different must have a head full of cement.

Inverting whilst diving can cause a bouyant ascent because of compressed gas expanding at the feet. This is a different scenario as scuba equipment generally makes the body top heavy (or bottom when inverted).

Fire a Delayed SMB from depth, it'll hit the surface vertical,if not under tension it'll lay flay on the surface, by somes reckoning it should stay vertical, it doesn't.
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