General Discussions  
This is the place to discuss general issues related to the U-boat war or the war at sea in WWII. 
Go to: Forum List•Message List•New Topic•Search•Log In•Print View
RE: bunker/zelle? and displacement
Posted by: J.T. McDaniel ()
Date: June 11, 2001 11:17PM

<HTML>Flooding an external ballast tank would cause the boat to go down because, while the boat\'s actual weight remains the same, the displacement, minus the air in the external tanks, is no longer sufficient to keep the boat afloat. An example: take a metal cylinder and note that it floats. Now, attach extra weight in the form of open-bottomed outrigger tanks that have no inherent buoyancy. (They\'re open at the bottom, so it\'s essentially trying to float a flat sheet of metal held vertically.) The open-bottomed tanks add a sufficient mass to the cylinder to make it negatively buoyant, but they hold enough air to counteract their extra weight. Now open vents in the top of the tanks, let the air out, and the cylinder sinks.

Theoretically, if you could arrange things so that the saddle tanks could be jetisoned in an emergency, the rest of the boat should pop to the surface.

So it doesn\'t really require internal tanks. Those would be used mainly for trimming the boat, except for the safety tank, which is always kept full unless the conning tower floods, when it would be pumped out to compensate. (Presuming the boat involved has its attack centre in the tower, which not all do.)

It might also be noted that U-boat command recommended rather strongly against actually flooding to the point of negative buoyancy, since it was potentially dangerous. The recommendation was to trim to a slight positive buoyancy and use the forward motion of the boat working on the planes to maintain depth.

J.T. McDaniel</HTML>

Options: Reply•Quote


Subject Written By Posted
bunker/zelle? and displacement Leif... 06/08/2001 03:34PM
RE: bunker/zelle? and displacement Werner Frank 06/08/2001 05:50PM
RE: bunker/zelle? and displacement kpp 06/09/2001 05:59AM
RE: bunker/zelle? and displacement Leif... 06/11/2001 07:23AM
RE: bunker/zelle? and displacement J.T. McDaniel 06/11/2001 11:17PM


Go to: Forum List•Message List•Search•Log In
Your Name: 
Your Email: 
Subject: 
Spam prevention:
Please, enter the code that you see below in the input field. This is for blocking bots that try to post this form automatically.
 **     **        **  **     **  **    **        ** 
 **     **        **  **     **  ***   **        ** 
 **     **        **  **     **  ****  **        ** 
 *********        **  **     **  ** ** **        ** 
 **     **  **    **  **     **  **  ****  **    ** 
 **     **  **    **  **     **  **   ***  **    ** 
 **     **   ******    *******   **    **   ******