Steven Shelikoff wrote:



That theory sounds compelling at explaining a difference in the
efficiency of the blade during it's downward vs. upward travel (if
there's no overhang. This part of your explanation would create an
upward force. It would also create a listing torque force since the
upward force of your theory above is applied off the center of the prop.
But since the column of water is the same in both the sideways
directions, where does the sideways force come from to create prop walk?

Steve

The part of his explanation which is not being stressed enough, is that
you must follow the blade through it's complete revolution.
The blade starts pushing down/back (pitch of the blade) but as it
rotates it begins to push to the side/back (RH prop going ahead),
pulling/pushing the stern to stbd.
Again, the blade is more efficient during the lower portion of this arc
(solid water) than it is in the upper portion (water being lifted into
air) which causes the propwalk.
The next time you get to look at a ship in ballast or riding light, with
it's prop just beneath the surface, watch the "wash" from the prop at
the surface. You'll see it being "thrown" up/back and to the side/back.
As for the "overhang" of the hull,issue, look again at the pitch of the
blade. When the blade is pushing up/back, it's not straight up, it's G
BACK/up, then look at the wash astern of your boat .... you'll see it
breaking the surface astern of you.

otn