ORIGINAL: Jim Thomerson
I think F1C is down to either 4 or 5 seconds engine run these days. What kind of HP, more or less, does it take to drive that size prop at 8,000 RPM? There was a letter to the editor in Aeromodeller which showed that the downhill changes in engine run in F1C have fairly closely tracked increases in engine power.
I would estimate about one horsepower more or less. If I had a 12.8x11.8 prop on hand, I could stick it on my electric plane and measure the watts with a wattmeter.
An APC 14x10E needs about 950 watts to turn that speed. This is probably some custom carbon fiber folding prop if it's on a competition free flight plane.