Speaking of which, when do we get to go play off the Frisians? Vance
-----Original Message-----
From: MerlinSub@t-online.de
To: personal_submersibles@psubs.org
Sent: Sat, 26 May 2007 4:43 pm
Subject: Re: [PSUBS-MAILIST] Diver lockout VBT
Hi Vance, allright :-)
I prefer for a small psub say for 2-3 people with a diver exit hatch that
the
ub is at anchor or on legs. I decide for my boat that anchor will be
better
ecause legs catch a lot of drag and if the tide switch - the boat is
maybe in
he wrong direction - and get the currents from the side for example. I
think a
ood (!) anchor system will be better in currents. The boat swings in the
right
irection like a airship on a mast.
But you are absolut right:
he system is better if the anchor is heavier and the hard tank bigger. So
a
sub designed for look out mission at anchor should have two drop
weights - one
n the bow (the anchor and chain) and the other in the stern area to
release.
ay 20 % of this psubs weight is ballast weight - that means in Kraka 7
tons
ize that 1,4 ts ballast or a 700 kg (abt.1500 pound) for the maximum
anchor
ize. If this boat has filled his anchor-compensating-tank (in general the
orward hard tank) with 350 KG additional water it needs 350 Kg force in
one or
he other direction - a lot for a tiny small 7ts boat.
Ps.: Euronauts anchor and the chain is designed to be drop in emergency
also.
best regards Carsten
vbra676539@aol.com> schrieb:
Carsten,
Yes, of course it works. Most diving bells and ARMS bells operate this
way.
hey have a clump weight on a wire/winch arangement, which can be set on
the
ottom. Then a winch can run the bell up or down from underneath for fine
djustment. The bell is strongly positive above the clump, so that divers
and
quipment leaving the bell do not affect its position. Or, they ballast
heavy
nd hang on their tether at a predetermined depth. Your drawing is a
version of
he former, except bells don't use VBT systems. In addition, the clump
weight on
ells runs about ten to twenty per cent of displacement (ie., approaching
a ton)
hich would be quite a load for a free swimming, psub style submersible.
The comment about X-boats is invalidated by history. Modern lockout
boats were
to 20+ tons all up, depending on the vehicle. Deep Diver, the originator
of
odern lockout diving (with proper credos to Simon Lake) weighed 8.25 tons
riginally and Taurus, the largest, weighs 24 tons. The X-craft weighed
27-tons,
nd were a testament to their designers, builders and operators. When you
get
hat heavy, the vessel is substantially less prone to abrupt vertical
transients
ue to what must be considered minor trim changes compared to overall
isplacement. Plus, the X-craft flooded the dive chamber, transferring
trim
ater to do so and keeping the whole thing internal, an important
consideration
or their mission profile. There was no much of a safe haven there for the
ivers, who drowned with alarming regularity both in training and on the
job, or
urfaced and had their heads shot off. The real issue was stealth, and
they went
o great lengths to achieve it.
Luckily, we don't have the Tirpitz to worry about anymore. And, our
references these days is for a dry chamber. The Brits couldn't use that
because
o do so would require the release of large volumes of air while venting
to
tmospheric pressure. Stealthy mid-water submersibles would raise the Navy
and
epublican ire in this country, too, as they are likely to take a dim view
of
nyone sneaking under their battleships.
Vance
-----Original Message-----
From: MerlinSub@t-online.de
To: personal_submersibles@psubs.org
Sent: Sat, 26 May 2007 11:59 am
Subject: Re: [PSUBS-MAILIST] Diver lockout VBT
I made a drawing to explain my words..
www.euronaut.org/content/upload/notes/AnchorandExit001.jpg
Note - I study the x-craft
X-craft have many troubles - mostly electric.
ut the diver exit in mid water works.
:-) best regards Carsten
MerlinSub@t-online.de> schrieb:
I forgot something. The trunk is below the hatch. I can close the hatch
with
ry chamber any time. Dosen't matter how the waterlevel in the trunk is.
Anchor underwater is simple - just make the boats forward hard tank
heavy
ith
he weight of the anchor. Euronauts anchor is a simple lead bell with 488
ound.
> Boat is than still neutral but anchor is than with 488 pounds in the
mud..
Realy havy currents are may a problem.
best regards Carsten
<MerlinSub@t-online.de> schrieb:
> Gentlemens..
>
> The diver exit on Euronaut is on the bottom of the diver chamber.
> And has a exit trunk below it.
>
> If a diver has ready to dive a density of say 1 - there is no
compensating
ystem required except this trunk.
>
> Say volume of the diver is 1 something and remaining air volume of
the
hamber is 10 something. Air pressure is equal to outside pressure and
hatch is
> pen.
>
> If the Diver leave the chamber the free air volume in the chamber
increase
o 11 - right ? - But that means that the air or gas pressure goes down -
and
he water from outside climb a little into the trunk until the chamber
volume
ithout the diver is back to 10 - right ?
>
> The water which climbs into the short trunk has also a density of 1 -
ecause the diver is neutral in the water - so boat is allways
compensate.
>
> Euronaut trunk is such high that three divers can leave the chamber
before
ater climb into the chamber..
>
> Keep it simple.. :-)
>
> The chain is only there to compensate small differences in water
density
nd
emperature and other small items to compensate - not to compensate a
diver
xit
>
> The boat is on anchor during diver exit about one divers high over
the
eabottom - The anchor is 400 pounds heavy.. and the hardtank on top of
the
nchor system is flooded to this 400 pound to make the anchor 400 pound
heavy.
>
> best regards Carsten
>
>
> "irox" <irox@ix.netcom.com> schrieb:
> >
> > 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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