On Wednesday, March 18, 2015 at 5:16:48 PM UTC-7, Mr. Luddite wrote:
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.



BTW, "prop walk" also occurs when moving forward which is probably the
most important reason for having the rudder slightly offset. The wash
over the prop compensates for the prop walk so with the rudder centered
on a single screw the boat doesn't try to make a slow turn due to prop walk.

Similar I guess to the little, adjustable trim rudder on an IO or outboard.

Speaking of 'trim' this boat had stationary trim tabs on it. They were cushioned by what looked like big shock absorbers.

For an old 27 ft. wooden cabin cruiser, it plowed water really hard till you got it up on plane and then it was really quite agile.
Speaking of getting up on plane it kinda reminded me of a fully loaded PBY trying to take off out of the water.

It seemed like it fought hard to plane out for quite a distance, but really it didn't take that long.

Too bad the plywood hull was starting to delaminate on the thing. I really had a lot of fun on that old tub.