Wayne.B wrote:
On Sun, 6 Jun 2004 08:49:02 -0400, "Charles T. Low"
wrote:

The main effect is from the spiral prop wash. In reverse, where asymmetric
thrust is virtually always more pronounced, the top half of the prop wash
vortex strikes the hull, and pushes it sideways. The effect will vary
depending on the underwater hull shape, the angle of the prop shaft, design
of prop ...

So, a right hand propeller in reverse turns counter-clockwise. The top half
of the spiralling prop wash is moving to port, and pushes on the hull,
yawing the stern to port. The bottom half othe spiral is mostly in clear
water, pushing on nothing.


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Charles, I think you've got it, thanks.

This is one of those explanations which I feel may have an effect on
propwalk amount, but is not the "root" cause of propwalk.
Reason ... you get propwalk ahead and astern. When going ahead, the wash
does not push against the hull.

otn