On Sun, 06 Jun 2004 00:28:20 -0400, Wayne.B
wrote:

On 05 Jun 2004 22:44:53 GMT, (Shen44) wrote:

the basic issue (propwalk) is caused by prop rotation and all
other factors may assist or decrease it, but the basic "phenom" occurs when you
rotate the prop.

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Of course, but what is the cause of the asymetric thrust? THAT is the
question. Everyone agrees that a prop with a horizontal shaft still
exhibits prop walk, implying that the bottom the prop is more
efficient at providing thrust than the top. Lots of theories have
been provided but none that seem totally convincing since prop walk
still exists to one degree or another on deep props, that have plenty
of hull clearance.

That's probably because it's a combination of several effects that all
contribute. Anyone who throws any theory out there that contains as
part of it's explanation some way that the thrust on one part of the
prop is different than on another part of the prop is probably correct.
Also, any explanation that contains part of it's explanation some way
tha the thrust from the prop gets translated into a rotational force on
the boat is probably correct.

For instance, no matter how deep the prop, the water on the lower side
is still going to be under ambient higher pressure than the water on the
top. So by moving the prop far away from the hull you may have
minimized the effect of hull turbulence on the top part of the prop.
But you haven't done anything about the pressure difference.

Steve