Steven Shelikoff wrote:


But it is changing. That's the variable we're changing, the angle of
the shaft. I.e., as the shaft angle gets closer and closer to coming
straight out of the boat with no downward angle, the prop walk gets less
and less. Or stated another way, the greater the angle of the shaft the
greater the prop walk. And that's due to the torque of the shaft, which
is applied more and more as a force to rotate the boat as the downward
angle of the shaft is increased. When the shaft is straight back with
no downward angle, the torque force from the shaft causes the boat to
list but doesn't rotate it in the water.



The rotational force from the prop remains the same. But what it does
to the boat depends on the angle of the shaft relative to the boat. If
the shaft is vertical, it will try and rotate the boat in the horizontal
plane, i.e., prop walk. If the shaft is horizontal, it will try and
rotate the boat in the vertical plane, i.e., list. Anywhere in between
vertical and horizontal and some of the force will try and rotate the
boat while some will cause list with the list increasing and the prop
walk decreasing the closer to horizontal you get.

Steve

Using your theory, Steve, the stern would walk the same way whether the
prop was a left hand or right hand wheel... and this is not the case.

I have always been under the impression, on straight inboards, that the
lower half of the propellor, the arc furthest from the boat/hull
surface, is the one that does the most work/thrust (eg. surface piercing
drives, etc.). The prop has better "bite" in the less turbulent water
away from the hull. This has been my experience too...

Correct Craft & Century inboards: RH prop, walks to port in reverse,
favors left turns in forward... (the opposite of your explanation if
taken to the extreme of a 90 degree propshaft angle).

Mastercraft inboard: LH prop, walks to starboard in reverse, favors
right turns in forward. (again, the opposite of your explanation if
taken to the extreme of a 90 degree propshaft angle).

The rotational force of the shaft/prop is transferred primarily to the
attitude of the boat on a single screw craft.

Rob