Trying to understand buoyancy -- etc.

[jscharpf]

I'm trying to understand some principles about the sub.

So you have these ballast tanks that you let fill with water until your sub is I guess.. neutral or a little less such that it sinks. This tells me that you have only enough volume of air that would displace enough water such that the weight is about equal to the weight of your sub.

In addition, you're carrying these compressed air tanks.. And when you're down there you "blow" the air from the compressed air tank, into the ballasts.. thus pushing out the water..

So.. I don't understand if you are carrying a compressed air tank, that you had to fill with xx amount of air... why doesn't that compressed air tank keep the boat from sinking? (sorry if I sound silly lol).

You had to take the same amount of air and just squish it into a tank.. but it has a certain number of molecules.. now you release them into the ballast. You're not increasing the number of air molecules just reducing the pressure..

I'm confused lol..

And does an air compressor work if you're underwater with a limited amount of air?




Also..

My wife says that, at depth, the pressure is higher so you would need not as much air pressure in the tanks to start to rise than you would need higher up where the water pressure is lower..She says it's the difference that moves you up..

Jeff