From: "George Slaterpryce" <gslaterp@hotmail.com>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Hard ballast tanks.
Date: Fri, 8 Dec 2006 09:44:29 -0500
If that's what you want you need to have 1atm ballast tanks that are
totatally sealed off from the outside environment and make sure you are
neutrally bouyant at the surface. (Depending on your mission depth, you may
have to take into account the compressability of water and your hull and be
slightly positively bouyant and power yourself down). which means that you
lose the ability to use ballast to control your position in the water
column and must power yourself up or down. You'd of course have a drop
weight for emergencies and possibly a compressed air emergency blow system,
but This all seems something that is rather complex for a submersible
that's operating range is probably going to be limited a very great deal
without surface support. (You can only run your motors so long on battery
power, and diesel bunkerage on a submersible the size that's generally
associated with a PSub would be... negligable)
Doug Jackson has the closest thing to an independant submersible/submarine
I think I've seen so far... you can see his stuff at www.submarineboat.com
(Note, I stole his moveable keel weight idea to stabalize Archimedes'
manipulator). So if you're thinking about building something that can get
itself to the dive site, then his idea might be something to look at.
Autonomy is a laudible goal, depending on your project size and what your
doing with it you either have to go very large or very small (AUV/ROVs) to
do it because your power requirements either need to be met via having the
bunkerage (Large) or they have to be designed to draw as little as possible
off of a limited power supply, a mere "trickle" compared to the needs of a
manned craft.
Thrusters of course are one of the largest drains on power.. (the are THE
largest drain in my rov projects) on a submersible powered by Minkotas
something far far larger than the small DC motors I use, you're looking at
major power requirements, that you could possibly offset with a Diesel
engine/generator, but that's not as efficient as having a straight through
diesel to screw arrangement, which means you're going to need to have some
sort of transmission setup that can be switched to have the mechanical
power of your diesel engine either power the main drive shaft, the
generator, or both.
This is not to discourage you, just to illustrate some design
considerations and give you something to think about.
George H. Slaterpryce III
www.bridgessoftware.com
www.captovis.com
----- Original Message ----- From: "kory mosteller"
<hardcoremosteller@hotmail.com>
To: <personal_submersibles@psubs.org>
Sent: Thursday, December 07, 2006 12:39 PM
Subject: RE: [PSUBS-MAILIST] Hard ballast tanks.
Good points Gene. I think the goal i've been striving for is to make my
sub as autonomous as possible. It's more of a personal achievement kind
of thing for me than a truely practical one. AS a kid, i never said to
myself "i want to be a SUBMERSIBLE captain"... it was always SUBMARINE. In
a full size diesel electric, all you would ever need would be food and
fuel. Leaving the diesel part out, (but retaining the electric compressor
and batt chargers) all you would need is electricty and food. for me,
that means that ANY large vessel can be a support craft as all i would
require would be somewhere to plug in an extension cord. Adding and
subtracting lead, you may find yourself asking "excuse me, do you have any
lead i can borrow?" Kind of an extreme silly example i know, but i think
you get the picture.
-kory
From: HUNTR2@aol.com
Reply-To: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Hard ballast tanks.
Date: Thu, 7 Dec 2006 03:16:41 EST
Hi Kori,
Welcome to the group. I, also live in the "land of fruits and nuts!"
I think you have it understood pretty well. I also want to have the
option
of increasing buoyancy to neutral with a shot of air to purge the hard
trim
ballast tank a little if I take on additional weight. Additional weight
could
be from accidentally letting too much water in the trim ballast or
picking
something up with the manipulator arm. If you don't have an air purge
capable
hard trim tank, then the only option is to put some air in the MBT.
Once
you do that, neutral buoyancy becomes a challenge if you want to descend
or
ascend very much without surfacing.
Yes, to have larger hard trim ballast tanks is doable, just more
structure
and plumbing required. They can be inside or outside the hull. If they
are
inside, they have to handle internal pressure safely. If outside the
hull,
they better be able to withstand the external crush pressure or have
automatic
pressure compensating air available. If a large one crushed at depth,
the
results could be scary and perhaps tragic.
It's interesting to note that those with actual pilot experience aren't
saying that large TB tanks are important. Leaving lead at home means you
have a
smaller internal sub to start with and having large trim ballast tanks to
use
when taking passengers just makes the sub larger (greater displacement)
to
handle the extra load. The space in the tanks is not functional for
living
or using for anything but buoyancy, weather you are using them or not.
In
effect, what you have done is limit usable internal space in single
person mode
in exchange for not carrying lead. If you're pulling a 5000 lb
submersible,
another 180 lbs of lead isn't too big of a deal. (Less than 1% of the
total weight).
Gene
Central Ca.
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