Cappio777,

I would agree that the amount of power wasted is relitively small but I would not agree that the effect on top speed is not something to be concerned about... Lets say we have a prop at 14.3 degrees at 75 percent diam roughly a 10x6 prop now if you add two degrees of down thrust this effectively becomes a 10x5 prop. Lets say that the prop is running at 12000rpm (200rps). The 10x6 prop would reach the zero thrust point at about 129 fps...the 10x5 prop would reach this point at about 114 fps. Assuming a linear dynamic thrust curve and an static thrust of around 4 pounds then at 100 fps the 10x6 prop would still be generating .9 pounds of thrust or 90 fp/s of power....the affective 10x5 prop would be generating about .5 pounds of thrust or about 50 fp/s. At 90fps the 10x6 would be generating 153 fp/s....the 10x5 126 fp/s At 80 fp/s 10x6...156 fp/s....10x5 133 fps. This does not take into account the thrust being used as a dynamic weight or the interferance drag because of down thrust. I'm estimating that the overall lost to top speed would be between 3 to 5 percent...or about 1 to 2 times the amount of down thrust used. This is conservative estimate it might be as high as 10 percent. I not quit sure what the tail loading on both planes would be.

Beating a dead horse is a realitively amusing.....maybe this will help anyone that is confused

[link]http://142.26.194.131/aerodynamics1/Stability/Page12.html[/link]

Steve