Hi Ralph,

I agree with the above, but this question has a different meaning to me ...

I fly at 9000 feet above sea level ... air density (and oxygen) at this altitude is much less than at sea level (at least 30% less). With this in mind and given the fact that I'm a 3D flyer, I have noticed that larger diameter props improve vertical ascents, but don't produce enough air over the control surfaces for several other maneuvers (I.E. I can hover but I can't do a waterfall nor bring the plane down in a hover attitude ... this is not pilot error as I can easily do these in lower altitudes).

Being a little more specific to my case, a 14X6 @ 9500 rpms provides a little less thrust than what I'd like, so assuming the 14X8 produces more thrust (and more air) in theoretical terms it should be the right choice of prop. Chances are the thrust generated by a 15X6 are greater than a 14X8, but I *think* using a 15X6 at this altitude would be equivalent to using a 15X3.6 at sea level.

Also, going back to the pitch matter, since there is less air density than at sea level, I should be able to get away with a couple of degrees more in pitch without excessively overloading the engine so in theory things should work out smoothly (this holds true with helicopter blades)

Does anyone see any flaws in my pitch/thrust/density assumptions ?