I've been looking to put a variable pitch prop on an airplane i'm building. This wouldn't be used for 3D flying, but to just change the pitch a little bit in the air to acheive highest thrust on the ground (static thrust) while getting the best thrust in the air. I'm looking to put it on a .61 os engine. I've looked all over for vpp and all I can find is for foamies or giant scale planes. I was thinking of using some kind of flybarlesshelicopter head with just the collective pitch or a larger helicopter tail rotor unit. Does anyone have any idea of how I need to do this? I need to keep the rotor rpm and motor rpm the same. Or is all this effort not worth the extra weight?

Variable pitch props were briefly available about 30-40 years ago for Pattern aircraft with .60 sized engines. You just missed them.

A helicopter head won't work. It isn't designed for the RPM you'll turn with a prop. I suppose it would be possible to engineer something up and build it yourself, but for what gains? The point of collective on a heli is to give fine control on thrust, not to improve the bottom and top end speed. Changing pitch in the air wouldn't accomplish that much since your diameter stays the same, certainly not as big a change as just changing props for different flight characteristics.

Did you check out VArio Props? http://www.electricprops.com/varioprop.htm