Re: [PSUBS-MAILIST] Diver lockout VBT

[irox <irox@ix.netcom.com>]

I don't think 170-200lbs object leaving the sub would be
negligible, the sub would float off with out it.  Carsten
suggested a neat way of dealing with that, having a heavy
chain resting on the sea floor attached to the sub, when I
diver gets out, the sub gets lighter and lifts a link or two
off the sea bed.  Search the archives for Carsten's original
email about this system.

Cheers,
 Ian.

-----Original Message-----
>From: Rob Bryan <Sundiver2000@earthlink.net>
>Sent: May 25, 2007 12:46 PM
>To: personal_submersibles@psubs.org, underseacolonies@yahoogroups.com
>Subject: [PSUBS-MAILIST] Diver lockout VBT
>
>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>.
>
>
>
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