NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Rolling Cruise Ship
From: Dave Walden
Date: 2006 Jul 20, 23:54 -0500
Typically, in large ships, the initial hard over starboard rudder
generates not just a starboard yaw angle, but a starboard down roll
angle. (I imagine looking forward from aft of the ship, the side force
generated by the lift of the rudder is obviously aft of the cg, so it
generates the desired yaw moment, but it's also below the cg so it
generates an undesired roll moment.) The yaw moment slowly induces a
yaw angle, this angle generates the forces which result in the turning
of the ship. As the ship goes into the turn, eventually, the roll
moment induced by the cg being above the lateral center of effort
overcomes the turning moment, and the ship recovers from the inital
"inboard" heel, and heels "outboard" (now like you as the passenger in
a car in high speed turn, or the car itself). (As the ship begins to
turn, the effective angle of attack of the flow into the rudder is also
decreasing, aiding the 'recovery'.)
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
From: Dave Walden
Date: 2006 Jul 20, 23:54 -0500
Typically, in large ships, the initial hard over starboard rudder
generates not just a starboard yaw angle, but a starboard down roll
angle. (I imagine looking forward from aft of the ship, the side force
generated by the lift of the rudder is obviously aft of the cg, so it
generates the desired yaw moment, but it's also below the cg so it
generates an undesired roll moment.) The yaw moment slowly induces a
yaw angle, this angle generates the forces which result in the turning
of the ship. As the ship goes into the turn, eventually, the roll
moment induced by the cg being above the lateral center of effort
overcomes the turning moment, and the ship recovers from the inital
"inboard" heel, and heels "outboard" (now like you as the passenger in
a car in high speed turn, or the car itself). (As the ship begins to
turn, the effective angle of attack of the flow into the rudder is also
decreasing, aiding the 'recovery'.)
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---