BTW for those who talked about F1 engines turning at 20K - yeah, engines turning that fast are "fun" - I mentioned the Fox MKIII .36 Combat special - I have one - they detuned them after that, as the MkIII was a BIT too close to the hairy edge of coming apart - used to throw con rods! Anyway, as I said 1.25 HP in just over a 1/3rd of a cu in - of course this was at OVER 30k RPM in full out trim - I mostly ran them with a slightly larger prop to detune them - I was ONLY getting about 1hp and turning JUST over 25k rpm. Only ran them full out in matches. What was fun was these engines had NO throttle, and are normally asperated, but had external high pressure fuel feed. To start them, you'd fuel up, clamp off the fuel line, prime the engine, hook up the battery, and flip the prop. If you knew what you were doing, it'd start in the first or second flip. Now came the fun - you had to unclamp the fuel line JUST right - see, if there was too much prime left, your engine would run rich for the entire flight, unclamp too LATE and you ran out of fuel and the engine stopped. Now you'd adjust the card (hand within 3/8" of that prop that is now turning, oh, 25k rpm), but you'd leave it a TAD rich - why? Because when you let go of the airplane, the ram air intake would force a BIT more air in, so it would lean out a bit, plus it "unloaded" the prop, so the RPMs would come up another 5k or so
Mind you - no muffler, so it was "plupp, plupp (you flipping the prop), rrrrrrRRRRRRRRRRSHREEEEEEEEEEK (adjust, launch) SHREEEEEE_E_E_EK. Now in a match, the OTHER team is doing the same thing, at the same time. You both got in the air and the pilots would attempt to cut a crepe paper streamer from the back of the other airplane - more than a FEW mid airs. You were limited to .36 displacement, and like in racing, More HP = More likely to win. LOTS of effort went into eeaking out a bit more, but still being able to start it (you start the engine during the match - and there were time rules). A GOOD ground crew was IMPORTANT (2 crew, 1 pilot) Normal match fuel was 40% Nitromethane (maybe a tad more or less) 40-45% alchohol, and the rest castor oil or synthetic oil (castor is better) - aka dragster fuel with some oil added. "practice" fuel was ONLY 25% Nitro
As you can tell, these airplanes were a "tad" different than the little .049 U/C aircraft a lot of kids played with