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Re: Ballast tanks
The post below is exactly what I was tryin to say in my last post but I
included a way to get around the air compression problem. My ballast
tanks have a vent valve at the highest point and a valve for injecting
air. The air valve is just a ball valve. Fine control is not really
needed since the only time you add air is at or near the surface.
Again, the Kitterege sub has a simular ballast system with open ballast
tanks fore and aft. It does have what he calls a VBT or Variable Ballast
Tank which is closed with the exception of 2 valve openings.
Al
> 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)?
> >>
>
--
Alan D. Secor
e-mail: secor@btv.ibm.com