Steve wrote: > There's a web page that has some info and a calculator about this:
> http://www.sierra.net/skyranch/frame1.htm > It says that increasing the horsepower from 100 to 120 would > only increase the airspeed about 6-7 knots, and that's at full > power in straight flight. I just ran the calculator and got interesting results. I'm running a _very_ flat prop 7146 on my 415-D with 85 hp to get tolerable climb and even that is not so great a climb. This limits my 2400 rpm cruise to a measured 100 mph. However, a normal prop gives (if I remember correctly) about 108 mph that engine. I used the 108 mph as my calculation point thinking that even with a "normal" prop on a 120 hp Franklin, I'll get climb as good as or better than what I have now. The result was 120 mph. Compared to my climb-prop-limited 100 mph, that's a real gain! (All numbers except my 100 mph measured cruise at 2400 rpm are estimated or calculated.) -- Ed Burkhead East Peoria, Ill. N3802H, 415-D
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