[secant0give]

I like to think I'm a pretty smart fella... but I would have thought that an irregular shape like that at the the trailing edge of the prop would have generated more turbulance not reduced it... just goes to show, how important it is to think outside the square.
Here's one to make you think a little. What about a 4 blade prop with 2 blades at say 10" pitch and 2 blades at 12"pitch. I know they will bleed energy because they will work against each but propellers spinning in the air are only about 70% efficient, so will the 10's help by giving you that initial thrust and then the 12's help with top end as speed increases or do they both cancel each other out and give you 4 inefficient 11" pitch blades?

I don't know how well that prop would go.
Back about 20 years ago I was doing some contract work at comalco
On some big fan forced annealing furnaces. These furnaces had two big fans to blow the Inert atmosphere around and keep the temperature even. One fan rotated clockwise and the other anti clockwise. These were expensive fans as not only were they big but they had to move a lot of Air around and it was hot too at 400 deg
Well to save having two spare fans someone had the bright idea of having a special fan made with two left hand blades and two right hand blades so it would work equally badly in either direction.
I don't know if they ever used it but it was sitting there in the store sure enough I thought they were pulling my leg until they showed me. Brand spanking new. I wonder what the company who made it thaught when they ordered it