shupack
Posts: 391
Joined: 9/30/2002
From: Omaha, NE, USA
Status: offline
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[QUOTE]Best RPM with this prop was a consistent 4300 RPM, which should increase a tad when in the air.[/QUOTE]
i'm not sure if i'm reading your posts right, but i think you're misunderstanding the difference between static and dynamic thrust. you can equate blade pitch to how much of a slice of air the prop takes each revolution. in an ideal world a 24-8 will go 8" per revolution, a 24-10 will go 10 inches. (in the real world you have to account for drag, inefficiency in the blades, air density, and some others)
when you have the engine strapped to the bench it's trying to go forward so you're just blowing air like a fan, in the plane it is moving forward, so the prop is pulling through the air, where you get the unloading. with a lower pitch prop you'll get more static thrust, but once in the air and moving there will be less thrust than a same diamter higher pitch prop. ie ducted fans, they have a verry high pitch, and on the ground can barely get rolling because their blades are stalled, but once they're moving and have air coming into the blades, they cook.
another example is a stick shift car. start out in first gear (low pitch) and it's easy, you accelerate from 0 till about 20 easily, and if you floor it it pulls pretty hard, but once you get going the engine unloads because the ground is coming at the tires faster than the gear accomodates (unloads) try second gear (high pitch) it's tricky to get moving because you don't have the low speed torque (blade stall) but once up to about 20 the engine will accelerate the car happily up to 40 untill you're past the speed range for that gear too.
this isn't an exact analogy because with a model engine there is only one speed, the fixed pitch. as the airplane accelerates the blades will unload and rpm will increase for a given throttle setting, unless the airframe is draggy enough (with a bipe i suspect it would be) you could even overspeed your engine with too low a pitch prop. I think otto would give the best advice on which prop to use with your neuport, but i think you'd be happier with a little higher pitched prop, and you can cruise at the same speed with a lower throttle setting and lower rpm=more realistic flight. and IMHO maximising static thrust is only good for hovering and torque rolls, which I would guess you're not going to attempt with a wwI bipe, but I could be wrong 
sorry if that sounded lecture-ish, but i just spent a month with my inlaws, both teachers, they rubbed off a bit
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Aoccdrnig to a Cmabrigde Uinervtisy sudty, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tih
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RCV 120 SP bench run results. - 
