FoamCrusher

I have used the APC 6.3 x 4, 6.5 x 3.7 and the 6.5 x 2.9. To be honest, there is not a great deal of difference in their flying performance. The larger the diameter the slower the prop is going to turn so you get overall reduced speed, but what you lose there you pick up in climbing ability. The difference with these props is mainly in how much current draw you get as you increase the thrust. Watch it if you are using lipos that are close to their maximum current with a 6 x 4; you could cook your pack easily with one of the larger props. Get a Whattmeter to be sure what you are going.

There are people who favor the Graupner CAM props - they make some high speed props at 5.2 x 5.2, 5.5 x 4.3 and 5.5 x 5.5. I tried the 5.5 x 4.3 and was not too impressed - lots of speed but it didn't climb well and stalled if given lots of power at low speeds. Again, it is all in how you like to fly.

I was out today and with the same motor and put on an Aeronaut 7 x 4 since the wind was up around 10 mph. With more torque and less speed, the plane was more controllable but noticeably slower. This was in a Unicorn wing with a 3S1P pack of the new Kokam 20C 2100's, so I didn't care about the current. Those babies will push 40+ amps, but I would never have done that to my Thunder Power 2100's in my Stryker. You adapt to the conditions but always within the limit of your equipment.

As far as using gas props on electrics, just be sure the prop you are using is rated for the RPM your motor shaft is turning. The Mega /4 is turning about 20K which is far more than any gas engine. Definitely do not use wooden props!

FC