Glenn Anderson wrote: > > You are probably right about the prop, I do have the E.ercoupe prop left > over, it is a much nicer looking prop, maybe if I don't sell it soon I will > put it on and try it > Glenn
Fred Weick was an especially good prop designer. He wrote "the" textbook on propeller design. When Fred chose the propeller for the C-75 for the Coupe, he got excellent performance. I haven't seen that much performance change when upgrading to the C-85, largly I think, because of the less well optomized propeller. Ideally, we would have variable pitch propellers so we could get flat climb props for takeoff and coarse pitched cruise prop for straight and level. I think the prop Fred picked for the C-75 is a pretty flat climb prop. Then he let it spin fast in cruise. Not too much load then because the prop isn't loading it too much. That doesn't optoimize your top speed but it gets safer take-offs from a small engine. Top cruise speed is also limited by the shape of the boat. In boat design, for each hull, there's a maximum speed which the hull can reach with reasonable increase in power. But past that elbow, the liquid flow over the hull piles up and doesn't flow well. Then the hull takes a LOT of power to speed up a moderate amount extra. Airplanes are like that, too. I think the classic Coupe's max easy speed is around 100-108 mph. Yeah, going to an O-200, 100 h.p. engine will let you go faster, but not much faster. The change to the new canopy on the Alons increased the easy max speed, I think. When I have flown formation with the Minnesota Group, I've had to go to near the max speed to keep up with their throttled back Alons. *And* they could out climb me. TANJ! I guess all it takes is money. I envy you your O-200, Glenn. I'd love to be able to take my wife out west to the mountains. My C-85 with a flat pitch prop did pretty well when I flew in the mountains the last time, by myself. How many people here are coming to Jacksonville, Ill., for the National Fly-in? Ed Burkhead
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