Counter rotating is what rckrazy meant (as in the P-38 and many other full-size twins). Contra-rotating is a completely different thing.
rckrazy, a pusher prop on one side will work (if you can find one the right size). Since by reversing the motor you'll be turning it exactly as intended its efficiency will not be affected.
I doubt if you'll notice any difference in the way it flies but there's nothing to stop you from trying it for yourself.
At SEFF there were two manufactures showing two inline motor running in opposite directions with a prop on each motor, counter rotating props. One prop was directly behind the other. Don't know if they were custom props or a product that is readily available.
Himax was one of the people, can't remember who the other was. Sorry.
hi thanks for clearing that up for me but im still confused. from his description i assumed he meant this. see first pic in article http://en.wikipedia.org/wiki/Contra-rotating_propellers two props spinning opposite directions on the same shaft. not to props spining different directions on seperate shafts. clear skies and good flying.
We were the other company at SEFF displaying a motor with contra-rotating props...the PJS 3D 550R Double. PJS won the best product for 2005 at a show in Europe for the PJS 3D 550R Double motor. They now have a larger version of it, the 3D 1500 Double.
The props at the show on the 3D 550R double were PJS 8 x 6 Carbon Fiber with the PJS aluminum spinner that is made for this motor. A PJS Supermarine Spiteful was at the show with this setup installed, but did not fly. You can see video of this motor running and the Supermarine Spiteful flying at our website.