On Dec 6, 2:02*pm, "Wilbur Hubbard"
wrote:
"Charles Momsen" wrote in message

...

What is the primary cause of propeller walk - torque or thrust?

Propeller walk is a term used to describe the results of the bottom of the
propeller operating in a more dense environment than the top of the
propeller. The primary factor is neither of the above. Drag, due to the
propeller's interaction with a denser medium, is increased at the bottom
half of the propeller. A prop turning clockwise as the vessel proceeds
forward as seen from astern will cause the vessel's stern to move to
starboard due to increased drag. Whereas thrust in a vessel is a description
of fore and aft forces, prop walk is a description of transverse forces
caused by drag differential.

I hope this helps clarify what is a muddled discussion point in most cases -
especially where I do not deem to impart my brilliance.

Wilbur Hubbard

Trust is thrust fore and aft port and stbd. Please don't muddy the
waters. To truly walk a whole boat sideways you need twin screws, 3 is
best.

The drag differentail is caused by varying thrust off the blades...
the angle of attack so to speak that thrust is transfered to the
shaft. Its up and port walk for a right hand screw, and down and
starboard for a left handed screw. Due to the weight of water it's
easier to push/slice down than up causing the pressure and thrust
difference off the fluke. It's the path of least resistance.

Joe