Re: [PSUBS-MAILIST] Hydrobatic Ballast System

["Captain Nemo" <vulcania@interpac.net>]

----- Original Message -----
From: <SFreihof@aol.com>

"...hydrobatic ballast system....Can you share some of that wisdom?"

(Wisdom?  Or we's dumb?  Sometimes I wonder.)    ;-)

Sure, Stan, there are no secrets.  When the video comes out, you'll be able
to see this; but for now...

The pressure hull for my NAUTILUS MINISUB is a machine-formed steel
teardrop-spindle shaped vessel with an appended  naviform cabin structure
and streamlined canopy.  Around, about, and upon this pressure hull is an
outer hull which replicates the Disney NAUTILUS.  This replica hull also
encorporates four integral ballast tanks (to simplify this discussion, say
they are generally rectangular in shape) which sit upon the outside of the
pressure hull like "saddle tanks".  Each of these tanks is vented and valved
at it's extremities, top and bottom, fore and aft: two top vents and two
bottom valves per tank; sixteen in all.  They all tie in to a central
plumbing system, and are also connected to a source of high pressure air.
Thus, no matter what angle the sub may sit at, by closing all but the
valve(s) at the lowest point and introducing air, I can blow any of the four
tanks clear.

INTERESTING BALLAST TANK STORY TIME:  Back in the early 80's I had a private
shop in Benicia which was concealed inside 8-foot high walls in my backyard;
had a shop; an outdoor work area; and a 6-foot deep pool for testing things
in.  Here, we experimented with improved snorkels, rebreathers, human
powered swimming machines, pump-helmet diving gear, and such.  My friends
used to come over and play with these things in the pool.  It was great fun.

One day I came up with an idea for a submarine I called the DCWS (Dry Cabin
Wet Sub):  basically, a series of chambers interconnected with plumbing, and
longitudinally arrayed on a central keel.  The idea was that a person could
stay dry (but would still be exposed to ambient pressure, so it didn't have
to be made out of heavy pressure-resistant steel) in a central chamber,
while two of four outer chambers were flooded or purged to submerge and
surface.

I made a 5-foot system-test model out of plastic soda bottles duct-taped to
a length of pipe and interconnected with sections of hose.  A barbell weight
slung amidships was the hard ballast.  A line from a small air compresser
was routed to the central "passenger compartment" chamber; and the extreme
ends of the forward and aft ballast tanks were "valved" with short lengths
of hose which hung straight down in the water.  On paper, it looked pretty
good.  And it seemed to work pretty well, too. I'd unplug a vent hose in the
roof of the "passenger compartment"; air would escape through the
interconnected system; water would rise in the outer chambers; and down
she'd go.  Then, I'd pinch off the "roof vent" with a clamp, turn on the air
to the passenger compartment chamber, and up she'd come.  As long as the
thing stayed perfectly level, it was a great success.

(Here comes the important part.)  But when the model pitched from a level
attitude, and one vent was at a greater depth (and greater pressure) than
the other, all that incoming high-pressure air would simply take the path of
least resistance, and go out the highest vent!  No matter how much air I put
in, I could not regain a level attitude, because the air would escape out
the highest vent rather than push the water out the bottom!

What this showed me was that, in order for a longitudinally-arrayed system
of ballast tanks to work, they must be valved so the pilot can open and
close them as needs arise; i.e., valved so he can close that high vent, so
the incoming air will have no escape at that point, and thus bring its
pressure to bear in forcing the water out the lowest vent in the tank.

And that's how the "hydrobatic" ballast system on my NAUTILUS MINISUB works:
no matter what angle it gets into, including 90 degrees up or down, and/or
completely inverted; I can still set the valves to blow the tanks dry, and
regain a level attitude.

AMUSING ANNECDOTE:  One of my "acquaintences" who saw the DCWS model thought
it was such a good idea, he decided to steal it and build one himself.  He
made a lashup out of 55 gallon drums, and carried a SCUBA tank as his air
source.  He put it into the waters of the Carquinez Straits and started to
vent air out the top of his passenger compartment.  Down he went.  When he
opened the valve on the SCUBA tank to resurface, he just kept on sinking;
probably a combination of that vent / valve problem I discovered, and the
fact that a SCUBA tank exhausting through the BC hose wasn't putting out
enough air fast enough to stop the descent.  If he hadn't had the foresight
to run a long steel cable from his "submarine" to the winch of a big 4WD
truck on shore, he probably would have drowned.  The MORAL to the story?  If
stealing half-baked ideas from experimental technologists doesn't kill you,
a lack of knowledge about how ballast systems work just might!

I hope this helps!

VBR,

Pat