Rob,
"In dive bell lockouts, the
bell is flooded a little"
....This post brought an interesting question to mind, and had me refer to this picture...
http://www.psubs.org/forsale/kraka/graphics/kraka4-2.jpg
Note that there is very little water in the hatchway, since the whole boat is the chamber , then I suspect he must pressurize the interior to ambient, and let the undogged hatch fall away.
It would be interesting to hear from Peter what his procedure is.
Joe
From: Rob Bryan <Sundiver2000@earthlink.net>
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org, underseacolonies@yahoogroups.com
Subject: [PSUBS-MAILIST] Diver lockout VBT
Date: Fri, 25 May 2007 10:46:47 -0600
>I've no experience with sub lockouts. I would think lockouts while
>hovering would be very difficult and dangerous, so assuming sitting
>on the bottom...
>
>Getting in and out of a vertical hatch with gear on is quite a task,
>whether scuba or line (with a bailout). In dive bell lockouts, the
>bell is flooded a little to make it easier. Wouldn't you do that in
>a sub lock out? So if the lock was 48" in diameter and you only
>flooded it up a foot, that would be 800 lbs. The diver leaving would
>be negligible, no? (this doesn't even include any trunk volume). Is
>this actually a problem?
>Rob B
>
>ShellyDalg@aol.com wrote:
>>Hi. This is in response to the diver weight compensation question.
>>Every dive trip in your sub requires careful measurement of what
>>you bring on-board.
>>If the dive plan calls for a diver to exit the sub while at depth,
>>I would think that it would be better to add buoyancy to cover the
>>divers extra weight while on-board, and then dump that buoyancy (
>>air bubble ) when the diver exits the sub, there-by maintaining
>>neutral buoyancy while the diver is outside.
>>When the diver is back on-board, blow the required amount of air
>>back into the trim tank ( a measured amount of water to compensate
>>for exactly how much the diver weighs ) and again maintaining
>>neutral buoyancy.
>>A sub with a diver lock-out function would need a bigger trim tank
>>than a sub without that capability.
>>Don't forget to calculate how much air the diver displaces with his
>>body, as this will figure into the required additional buoyancy
>>too.
>>You don't need a separate pump system, nor would that be desirable,
>>to let a diver exit and re-enter the sub. The lock-out chamber is
>>controlled by air pressure, and any small amount of water that
>>remained within would be easily compensated for by the additional
>>trim tank volume.
>>You WILL need some means of dumping the air from the lock-out
>>chamber once the water is blown out and the hatch is closed so the
>>diver is once again at one atmosphere. This needs to be monitored
>>closely so a diver has time to dump the excess nitrogen absorbed by
>>his body tissues and blood. A diver lock-out chamber is really much
>>like a de-compression chamber, but is located inside another
>>chamber ( the sub's pressure hull ) so a compressor to drive out
>>the additional air is required.
>>Frank D.
>>
>>
>>
>>------------------------------------------------------------------------
>>See what's free at AOL.com
>><http://www.aol.com?ncid=AOLAOF00020000000503>.
>
>
>
>************************************************************************
>************************************************************************
>************************************************************************
>The personal submersibles mailing list complies with the US Federal
>CAN-SPAM Act of 2003. Your email address appears in our database
>because either you, or someone you know, requested you receive
>messages
>from our organization.
>
>If you want to be removed from this mailing list simply click on the
>link below or send a blank email message to:
> removeme-personal_submersibles@psubs.org
>
>Removal of your email address from this mailing list occurs by an
>automated process and should be complete within five minutes of
>our server receiving your request.
>
>PSUBS.ORG
>PO Box 53
>Weare, NH 03281
>603-529-1100
>************************************************************************
>************************************************************************
>************************************************************************
>
