I'm getting 107.95 at 2500 RPM with a 7148. That's with the 5% loss. Certainly seems realistic for the C-85/O-200 STC engine.
--- In [email protected], "Ed Burkhead" <e...@...> wrote: > > > > Bill wrote: > > >>>>>>>>>>>>>>>>>>> > > The 48" pitch refers to the theoretical 48" the prop (and thus plane) moves > thru the air in one revolution. > > So 48" x 2400 rpm=115200 inches per minute x 60= 6912000 inches per hour / > 12 = 576000 feet per hour / 5280= 109.09 miles per hour. > > This is in a perfect world. > > <<<<<<<<<<<<<<<<<<< > > > > Yeah. With Coupes, the percent of drag seems to be around 5%-maybe 4%. > > > > So, take your theoretical 109.09 mph for the 48" prop time .95 and you get > 103.6355 or about the 104 mph most owners actually see. > > > > Now, let's see with a 52" prop and 2350 rpm . . . > > 52" x 2350 = 122,200" > > 122,200" perminute x 60 = 7,332,000 inches per hour > > 7,332,000 inches per hour / 12 = 611,000 feet per hour > > 611,000 fph / 5280 = 115.72 mph > > 115.72 mph * .95 = 109.93 mph more or less > > > > So, I conclude Al is missing about 5 mph. That's either instrumentation or > real. > > > > I wonder if 2350 is Al's chosen power setting. If so, it makes sense that > he'd set it the same in summer and winter - and, thus, get about the same > true airspeed out of it. The engine should have more power available in the > winter than in summer. > > > > Ed >
