Re: Ballast tanks

[SFreihof <SFreihof@aol.com>]

Hi all;

Again, for my two cents...

A ballast tank open to the environment is possible, and easiest if the normal
dive condition is a fully flooded tank.  In the absence of external controls
for a tank open to ambient water pressure, any air inside the tank will
compress with depth ( i.e. pressure), and so you lose bouyancy as you dive.
Conversely, you gain bouyancy as you ascend if there is air in the tank.  This
is not a good idea.

Military subs (at least WWII vintage diesel boats) have ballast tanks which
are valved at top and bottom.  In dangerous situations, they will open the
bottom vents while running on the surface to charge batteries.  This was
called 'Riding the Vents" and allowed quick submergence because the tanks
would flood as soon as the upper vents were opened.

A ballast tank can be open to ambient if you control the water level in the
tank, and simultaneously therefore, the air pressure in the tank.

Is anyone in this group familiar with designs which actually do this?  Has
anybody actually studied the ballast system on the Sport Sub, for example?

I have an idea that the water level and air pressure in an open ballast tank
could be accomplished very easily with a scuba regulator, but the flow rate
may be a limiting factor.

Comments?

Stan







In a message dated 98-03-13 21:53:06 EST, you write:

<<    My second question is "Is it OK to have the hard ballast tanks (for
 nuetral bouyancy) open to the environment or must they be a pressure tank?"
 All the reading I've done indicates that they should be a pressure tank but
 I wonder about having them open to the atmosphere. Has anyone made their
 nuetral bouyancy tanks soft (or open to the atmosphere)?
  >>