I've always wondered if a submarine, 1,000 feet underwater, experiences
"propwalk" .... I'm betting it doesn't G.
At any rate, to save some unnecessary reading, by the numbers on some
points at issue:

1. We are not talking about some highly visible, easily measured,
variations in efficiency. These are very subtle, but sufficient to cause
the condition.

2. Due to it's relative proximity to the surface, I do not feel that a
blade is at maximum efficiency at this angle of rotation. My
sense/guess/feel, is that isn't doesn't reach maximum until about 045*.
Why? Sit on a tug, tied to the stern of a ship and watch "propwash" for
awhile. The wash is pushed to the side, breaking the surface during the
initial part of it's rotation. However ....

3. Ignore the quadrants 000-090, and 180-270 ( My sense - the prop
efficiency is in transition during these portions of rotation. In one
the efficiency is increasing and the other it is decreasing ... 0% net
difference.)the blades are still pushing back, but there is no net
effect (arguably) which we can readily apply to "propwalk". Instead .....

4. Concentrate on the quadrants 090-180 and 270-000. From 090 to 180 the
blade is pushing back against a relatively solid column of water, down
against a relatively solid column of water and increasingly LEFT against
a relatively solid column of water. During this entire quadrant of
rotation, the blade is at maximum efficiency...... BUT, from 270-000 the
blade is pushing back relatively nearer the surface, up toward the
surface, and RIGHT towards and relatively close to the surface, where it
can and does break the surface or at least bulge the surface. So.....

5. My sense from this. The blade, in these two all important quadrants,
is more efficient between 090-180, than it is between 270-000. The
differences if you add in depth of the hub of the prop, may diminish,
but for a boat floating on the water surface, the efficiency will never
be equal...... VBG ..... propwalk.

I disagree that there is no such thing as a "more solid" column of water.
I disagree that a propellor is at maximum efficiency at 000* (on a boat
floating on the surface of the water).
I disagree that by moving the blade a few feet down in the water, you
will totally negate the effects or differences in blade efficiency.

I think we've probably hashed, thrashed, and rehashed this enough in the
NG, Steve. However, feel free to continue via E-mail if you wish.

otn