View Single Post
  #77   Report Post  
JAXAshby
 
Posts: n/a
Default Thrust vectoring

nope. *pull* does NOT affect the rudder, only *push* does.

careful. you *must* be moving through the water for a

rudder to be effective
when trying to back up.


Not quite true. When 'trying to back up' (attempting
rearward motion) you will often use bursts of ahead over the
rudder to alter the pointing of a boat, whether you're
static or actually moving astern.

Very large diameter props, well sheltered from prop walk,
with a large rudder close to the prop (as on single prop
tugs and some fishing vessels), will, in astern, cause
rudder to alter the direction from which water is ingested
into
the prop. If the water is ingested from one direction,
and exits in another, that deflection causes a change in
lateral momentum - creating a force which in turn causes a
yaw. Of course, single screw tugs are not so common now, and
this thread was about twin screw vessels. But this used to
be a useful manoeuvring trick.

Note that the effect is in the same direction as the burst
of ahead; ie, full left rudder yaws the vessel to the left
in either fwd or reverse (no 'suction' effect). And note
that I was talking about props sheltered from prop walk -
either through their depth, the use of shields or a lateral
offset.

JimB