Sorry, I got my information wrong when I stated that a three bladed
prop advanced 15 inches during each revolution at 200 mph.

I now have the article in front of me and the exact quote is as
follows: "At 200 mph and 2,800 rpm, the blades on my three-plade prop
follow three distinct helical paths through the air, and each blade is
25" ahead of the previous blade at the same point of rotation."

I repeat that I am not a prop engineer nor do I have any formal
training in aerodynamics but it appears to me that by advancing 25"
during it's revolution, the affect of one blade might have upon the
next one would seem to be pretty inconsequential.

Corky Scott

For what it's worth, at 150 kts and 2500 RPM means the airplane advances about
6 feet per prop rev. A two bladed prop means each balde is in air 3 feet ahead
of the prior blade.