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Re: [PSUBS-MAILIST] K250 to K400 modification
Hi Carsten,
Firstly it looks like it could be a Germany - Netherlands final.
NewZealand could be the only unbeaten team in the world cup!
Re the buoyancy issue-- You would have to go down heavy &
use your thrusters as you could always add air to become more
buoyant, but if you emptied 10 x 90 cubic ft tanks to equalize your
hull this would make you about 100 lb lighter by the time you
expelled the air coming to the surface.
( a scuba tank is about 10lb lighter when empty ).
By the way what shall a K250 do in 400ft on a stricken sub?
Maybe offer moral support. Assess the situation.
Or take a grapnel down & hook it on the sub.
Or locate it for some tech divers.
Alan
----- Original Message -----
From: <MerlinSub@t-online.de>
To: <personal_submersibles@psubs.org>
Sent: Sunday, July 04, 2010 11:23 PM
Subject: Re: [PSUBS-MAILIST] K250 to K400 modification
Hi Alan - In General you can go that way.
A sub designed for 150 ft max dive deepth can double there operation depth
with that way.
The only real problem is if the boat is in this condition and you pop up
(surface fast).
There are two possible failtures:
- Overpressure vale to small and hatch and windows pop out.
- Over pressure vale has the right huge size and crew gets heavy
decrompression tickness, blown ears etc..
- In case of a fire or anything else in the sub - you can not surface in
short time and probably get problems in it.
We discuss this way some years ago but never go this way.
Its a way only for crew with real expierence with there sub and also real
scuba divers with expierence with decompression dives.
If you double the cabin pressure just with air this means you double the
amount of o2 atoms per volume.
The fire risk increase.. If you increase the pressure with helium this will
work. The problem starts than when you lower later the pressure - you have
to feed o2 back.
By the way what shall a K250 do in 400ft on a stricken sub?
vbr Carsten
"Alan James" <alanjames@xtra.co.nz> schrieb:
Hi Jon,
The emergency I was thinking of was along the lines of
a stricken sub entangled at 400ft & the nearest help was
a sub capable of 250ft depth.
Alan
----- Original Message -----
From: Jon Wallace
To: personal_submersibles@psubs.org
Sent: Sunday, July 04, 2010 5:41 PM
Subject: Re: [PSUBS-MAILIST] K250 to K400 modification
Sorry Alan, I missed the "emergency situation" part. So yes, in an
emergency where you are
sinking in water beyond your normal operating depth you could certainly
counter some amount of
outside pressure by increasing the pressure within. That may delay
(possibly prevent depending
upon depth) hull failure but of course has the potential for some other
nasty biological side
effects and I'm guessing in such an emergency you're probably going to be
at the increased ambient
depth well beyond no-decompression limits. We had a similar discussion a
few years ago about
standardizing on a specific valve so that divers could feed air into the
cabin of disabled sub that
did not have life support capability, until that sub could be raised. I
believe the discussion
started with "schrader" valves (tire valves) which were determined to be
too small to be useful.
Many of the same issues were raised at that time ie...decompression upon
surfacing, additional
pressure in the cabin affecting instruments, etc.
Jon
On 7/4/2010 12:29 AM, Alan James wrote:
Thanks Hugh & Jon for the vote of confidance.
I did qualify this with " In an emergency situation". I think I have
been misunderstood.
You take your sub down to its 250ft limit with several extra dive
tanks on board.
At this point the outside of your hull is experiencing round 125psi.
For every 33ft further you go down you add 14.7psi. The hull would
always be experiencing
125psi from the outside as the pressure you're adding would be
countering the additional
pressure from additional depth.
So no pressure as such from the inside would be pushing your view
ports out.
The reason I said to increase the O2 flow into the hull is the
"bellows add" system based on
sensing a drop in pressure wouldn't work. In that system the O2 flow
is set below the users
normal O2 consumption & then topped up from the bellows add system
because if the O2
was set too high there would be a continual pressure build up & 02 %
increase.
You could safely bump up the O2 a tad as it would be safer to have too
much O2 than not
enough. This, as Jon said wouldn't matter much because your time would
be constrained by
decompression tables, & there would be enough air in the hull to
breath from.
So in a life or death emergency you could take several air tanks into
your hull & a set of
dive timetables, open the tanks by hand at the 250ft mark & go to
400ft.
Alan
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