Prop Possition for optimal performance

[FireKracker50]

I have head many differnet people talk about spacing the prop further back on the shaft away from the gearcase for performance gains.

Can anyone explain to me the physics/hydrodynamics to why this helps?

Also what is the proper way to space a prop such as a Pro ET? Is thier special prop spacers?

And last how far back do you wany it spaced for optimal performance?

thanks for any help
Cody

[pyro]

Spacing the prop, even a little, will greatly increase the amount of sideways force acting on the propshaft in a surface application. Gains have been reported, but there are risks. I wouldn't consider doing it with a small shaft. I'm already nervous when I run my SRX, because it's spaced so far back and has so much blade rake...

[FireKracker50]

good point i hadn't thought of that... is there anyone out there that has reported bending a shaft due to spaceing the prop back?