RE: Wings and back plates

[Iain Swaine <iain@xxxxxxxxxxxxx>]

At 14:39 06/01/98 -0000, you wrote:
>>> even with unbungeed BCDs, air would escape [thru a puncture] unless
>>>holed at the bottom 
>
>even if holed at the bottom, air could escape - the air in a BCD is
>under constant pressure from the downforce of the weight of your
>equipment plus the ambient pressure of water, which may be fractionally
>more than the equalising pressure of the water whenever you move, roll,
>stress the BCD etc.
>
>>> Besides, you do have an auxiliary buoyancy device (drysuit) if this
>>>does happen.
>
>I wonder just how much lift a drysuit really could provide, especially
>if its partially inflated for comfort when you're neutral? How grippy is
>a latex neck seal when (say) 15lbs of lift from the suit is trying to
>force it off your neck?
>
>Ive oft heard it quoted as the bailout option, but never seen the
>figures - I know mine floats me at ahoulder level without leaking (much)
>when its blown up like a rock, but Id like to hear from someone who's
>had one carry them plus a full bottle (eg. aborted dive, BCD goes down
>on entry from boat) and waterlogged BCD.
>

I've got a Typhoon teabag (sorry, tracer!) drysuit and had occassion to
have to use it as a primary source of inflation last year when the elbow
sheared off the top of my OMS wing at the end of a dive once it was fully
inflated. I dive with twin 10l 232b tanks with an ABS backplate and have
8kg of lead to achieve neutral bouyancy.

In order to keep my head above water I had to put a reasonable amount of
air in the suit once I had closed off the auto dump, and it was more than a
little uncomfortable to say the least round the neck seal. My buddy
commented that I looked like the Michelin man, and certainly felt like it.
I was glad that it was only force 1-2 that day otherwise things could have
gotten interesting. BTW it does have altex seal and this didn't leak.

I was also very glad that the wing didn't give way during the dive (I use
it as the primary source of bouyancy) as it was a fast 30-35m drift dive
between the Kyarra and Caratan out of swanage! I had about 150 bar left in
each cylinder at the end of the dive, so I wasn't full laden.

Iain

Iain Swaine - Technical Analyst	
(W) iain@xxxxxxxxxxxxx	(H) iain@xxxxxxxxxxxxxxxxxx
Cumulus Systems Ltd, 1 High Street, Rickmansworth, Herts., 
WD3 1ET, England. Phone - (01923) 720477, Fax - (01923) 771411