On 3/18/2015 7:14 PM, Tim wrote:
On Wednesday, March 18, 2015 at 3:55:00 PM UTC-7, Mr. Luddite wrote:
On 3/18/2015 6:51 PM, Mr. Luddite wrote:
On 3/18/2015 6:10 PM, Tim wrote:
Greg's thread made me think about my old Chris-craft Cavalier and how
it was set up. It had solid shaft propulsion. And looking from the
back, it had the rudder just left of the prop. I wonder why it was set
that way instead of being directly behind the propeller instead of
offset the way it was. Also I wonder why only one prop instead of two.
It was a bugger to back out of a slip .

When underway everything was fine and would steer well regardless of
speed or direction.
Any ideas?



Tim, Wayne can probably provide a better answer but I believe what you
are referring to is an "offset rudder". In theory it makes the rudder
more effective by putting it in "clean" water rather than directly in
line with the prop wash. Not uncommon.


BTW, when backing out (or into) the slip, the rudder has virtually no
affect on steering. Slow speed turning relies on the prop wash hitting
the rudder.

Richard, I discovered that when It was demonstrated to me. Yes, at a very slow speed, the boat would back to the left only regardless of how you set the rudder, and that provided to be a royal pain in a few cases.

I hadn't thought of the "clean" water theory, but that does make sense now that you mentioned it. That was the only rudder boat I've ever owned. since then it's been I'O's.



Moving to the left (or right, depending on whether the prop design is LH
or RH rotation) is a result of "prop walk". A RH prop will tend to move
the stern to port in reverse while a LH prop will tend to move the
stern to starboard.

The technique used for backing a single (fixed) screw with rudder boat
is called "Back and Fill". It's a combination of short forward thrusts,
then backing depending on the prop walk to maneuver into the slip. You
also have to take into account wind and current if they are present.
Backing a single screw boat with rudder is a challenging technique to
learn. It's one of the reasons I enjoyed the Grand Banks we had. It was
different and required much more skill than docking a twin engined boat
or even a I/O that has the advantage of vectored thrust, forward or
backward.