I read in one of these RC forums that the tractor prop is more efficient than a pusher prop with the same diameter, pitch, prop design, prop material and RPM. Is this true? If it is true, why? If the opposite is true, meaning that pusher are more efficient...then Why also? Thanks for your valuable reply.
larry

I am no engineer but that sounds rather strange to me. Thousands of electric pusher models are flying merrily with tractor props mounted on the back end of their models. Why on earth would the airfoil of a propeller differ from one end of the plane to the other? The molecules of air don't know which end the prop is on.

I am an engineer and it sounds strange to me, too

One advantage of a tractor prop with an air-cooled engine is that it blows air over the engine, which a pusher wouldn't do to the same extent. so engine overheating can be a problem with pushers. That's not a matter of prop efficiency, though.

The original statement might have been describing more than just prop-for-prop.

Every pusher installation is going to put that prop into far dirtier air than tractor installations see. There is going to be something in the way of clear air, by definition. Because, when you get down to it, a pusher is nothing more than a tractor with something in front of it.

My experience with 4 different engines on a Bob Cat 52 indicates that either one size smaller prop or one size larger engine is needed in pusher configuration. The air across the wing is probably very dirty. Several of the engines appeared to come up to speed in stages indicating engine thermodynamics were also different. A different relationship of prop to wing on other types of airplanes would likely give different results.

Bill

Now that makes sense

So, it's the plane configuration and not the prop?? Just wondering, I have never built a pusher, mater of fact, other then the little E powered planes I have never flown one.

Pretty much what's being said here is that a pusher prop mounted behind a plane will encounter more turbulent ("dirty") air than a tractor prop mounted in front of a plane/wing, thus reducing the prop's overall efficiency.