Model Forum / Radio Controlled / Air Models / August 2010

You will still need to reverse the direction of rotation of the motor to
get the air to go the other way. Otherwise, it is going to flow the
normal direction with high in-efficiency.

A pusher propeller has the blades pitched the opposite of a normal
propeller. With a normal propeller, it has to rotate counter-clockwise
for air to flow though it properly. To reverse the airflow, you need to
rotate the propeller clockwise. To make it efficient rotating clockwise,
you need to turn the propeller around.

It would seem that way.  However, no matter which way you install the
propeller on the engine, if the engine shaft rotates counter clockwise
the prop will blow the air over the engine.  Take a model propeller,
look at it edge on, then rotate it 180 degrees and you will see the
same angle of attack between the airstream and the propeller blade.
Only when it is reversed, the airfoil shape is very inefficient.

Ron Kelley

If you simply flip the propeller, it _will_ _not_ reverse the direction
of the airflow. It will continue to "propel" the air in the same
direction as before the flip, i.e. over the motor (Just try it, if it is
not obvious to you.) The only thing that will change is that the
intended leading edges of the blades will become trailing edges (and
vice versa), which will essentially destroy the efficiency of the prop.

Without a special pusher prop, the only way to turn a puller setup into
a pusher setup is to reverse the direction of the motor. This will also
turn the leading edges of the prop into trailing edges etc., which is
why you also have to flip the prop to get back to the normal efficiency.