DSK wrote:
.... At full speed, the prop stream does increase rudder
effectiveness but I'd say that it's not "significant."


otnmbrd wrote:

Would disagree. Prop wash is a very important contributor to rudder
effectiveness at all speeds .... put a ship's engine on "stop" ....
trust me, your effectiveness decreases rapidly.


How about when letting the prop freewheel from full speed?

DSK


Tough question and I don't think there's any ONE right answer.
In the case of the Titanic at the time frame between sighting and
collision..... IF they had started to reduce steam to the turbine prior
to reversing the recips, this measured reduction while the other engines
were going full, would/should have created a "disturbance" aft of that
center prop which would/should have reduced the effectiveness of that
single, center rudder.
Now, since I can see another route to your question. If the ship was
steaming along (different scenario) at full speed with no steam to the
turbine (it's just "freewheeling") would this reduce effectiveness of
the rudder? I would have to say yes, as it becomes a rotating drag which
, in my opinion, has to create disturbed water aft of the prop, which
has to disturb the "smooth" flow of water across the rudder.
Without specific test which address the many various conditions and
actions that where or would occur, you have to assume that the above is
speculation on my part based on my own sense of what has happened when
handling one or two ships. G I.E., I don't guarantee I'm
right....these are my observations.

otn