http://www.fleetsubmarine.com/diving.html


To submerge, the crew opens vents at the top of the ballast
tanks. This lets the air out. The bottom of the ballast tank is
open to the sea, so as soon as the air is released water comes in
to take its place, the displacement increases, and the boat slips
below the surface.

Submarines are designed so that, with the main ballast tanks
full, the weight of water they displace will be as close as
possible to exactly equal to the weight of the boat. In practice,
the boat should retain a slight amount of positive buoyancy, so
that it will want to slowly rise to the surface if nothing else
acts to keep it under.









"Dave Doe" wrote in message
. nz...
In article ,
says...

"Dave Doe" wrote in message
. nz...
In article ,
says...

"Dave Doe" wrote in message
. nz...

Can you sink a 'positive buoyancy' boat with water? Can
you
sink it with
lead? You've proven my own point.



What do submarines fill their ballast tanks with?

positive bouyancy boat submarine - EVER.


Bzzzt...Oh, I'm sorry, the correct answer is ''WATER'' .

Thanks for playing.

Water - ROTFL.

No, subs sink cos either they're heavier than water in the
first place,
or they use ballast that is heavier than water such as: Lead,
or for
modern wartime subs I would think they'd use DU (depleted
uranium).

Water! - LOL.

So the correct answer is most assuredly not water. Subs are
made so
that the mass/volume is denser than that of water - and they
sink. They
then have *AIR* in them that provides bouyancy - the cool thing
about
air is it's *compressability*. The "blow the (air) tanks" -
and the
decrease in bouyancy means they sink. To surface, they blow
the water
*out* of the air tanks, filling 'em with the air from the
compressed air
source.

Think of a diver - FFS. They sink because of? Same as a sub -
only as
said, I would think modern war subs use denser material such as
DU -
'cos they can afford it.

So the correct answer is lead or DU.

--
Duncan