U-Boat Stability

MarkShot · 01-11-08, 12:45 PM

Until the nuke boats, hull design was primarily for surface performance as opposed to submerged performance.

Subs unlike surface ships even when surfaced have a lot less reserve buoyancy. Thus, taking on some water in rough seas would impact a sub more than a surface ship.

Stability depends on moment arms and location of the CB and CG (center of buoyancy and center of gravity). USN fleet boats had lead weights in the keel to further improve stability and lower the CG. This would also be the reason for the batteries being located low in the design. Things like upgrades to the con like radar or new and heavier deck guns could have a dramatic impact on handling characteristics.

Balast tanks were generally all flooded or all blown to promote stability. Much smaller trim tanks and pumping were used to adjust trim and buoyancy. However, at the point of surfacing and blowing the balast, there was a potential for temporary instability with large amounts of water sloshing in the tanks based on angles. This was in part addressed by having baffles in the balast tanks to restrict the flow of water.

Above comments are the result of reading declassified USN fleet boat docs and not anything related to U-boats.

01-11-08, 12:45 PM	#3
MarkShot Ace of the Deep Join Date: Jul 2002 Posts: 1,134 Downloads: 93 Uploads: 0	Until the nuke boats, hull design was primarily for surface performance as opposed to submerged performance. Subs unlike surface ships even when surfaced have a lot less reserve buoyancy. Thus, taking on some water in rough seas would impact a sub more than a surface ship. Stability depends on moment arms and location of the CB and CG (center of buoyancy and center of gravity). USN fleet boats had lead weights in the keel to further improve stability and lower the CG. This would also be the reason for the batteries being located low in the design. Things like upgrades to the con like radar or new and heavier deck guns could have a dramatic impact on handling characteristics. Balast tanks were generally all flooded or all blown to promote stability. Much smaller trim tanks and pumping were used to adjust trim and buoyancy. However, at the point of surfacing and blowing the balast, there was a potential for temporary instability with large amounts of water sloshing in the tanks based on angles. This was in part addressed by having baffles in the balast tanks to restrict the flow of water. Above comments are the result of reading declassified USN fleet boat docs and not anything related to U-boats. __________________ War games, not wars! --- Only a small few profit from war (that should not stand)!