Symmetry considerations also dictate that a single rudder must lie along the axis, even on a sail-driven vessel. One point that's worth making --- whether about boats or aircraft --- is that turning the rudder alone has almost no useful effect on changing the direction in which the craft is moving. All the rudder does is change the direction in which the craft is pointing, which is not the same thing at all. As John Aspinall pointed out, changing direction of travel involves the application of a (relatively large) force, supplied on water either by a propeller or the action of the wind on appropriately re-positioned sails; in the air by lift on the wings as the plane banks into the turn. WFL On 6/25/13, Henry Baker <hbaker1@pipeline.com> wrote:
But these rear rudders were ubiquitous even on sailing ships:
https://en.wikipedia.org/wiki/Rudder
Here's something I just learned from Wikipedia:
"Rudder post and mast placement defines the difference between a ketch and a yawl, as these two-masted vessels are similar. Yawls are defined as having the mizzen mast abaft (i.e. "aft of") the rudder post; ketches are defined as having the mizzen mast forward of the rudder post."
At 04:13 PM 6/24/2013, Fred lunnon wrote:
On a small motor vessel driven by a single screw propeller, a considerable amount of steering force is generated by the action of the propeller stream on the rudder, which therefore has to be in line with and adjacent to the propeller.
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