CatalinaWOW
50cc
Depends on what is shaking. If it is bouncing on the gear it will get better in flight. Also RPMs change so you may be moving off a resonance. The biggest reason it gets "better" in flight is that it gets farther away, where we can't see or hear it as well. Sound falls off as the square of distance, so just moving from one arms length to two cuts a few dB off the noise.
The idea for a database of good combinations doesn't seem as good on further thought. First there are the reports from people with the same engine on three airframes. There could be a bunch of reasons for that in addition to the wear in of a piston ring. There are a multitude of potential resonances. Just for starters there is the first bending mode of the body both vertical and horizontal. Then the first body torsional mode. Bending modes for wings, tails and rudder. A mode for the fuselage bouncing on the gear on the ground. Another for the gear bouncing like a tuning fork in the air. Not to mention higher order modes and coupling between these modes. Each of these will vary due to variations in stiffness and weight between airframes. Damping ( inverse of the tendency to peak at resonance) will vary with wood quality, joint quality, and probably most important, variations in covering tension.
Has anyone noticed differences between really hot or really cold days. Or between really humid and really dry days?
The idea for a database of good combinations doesn't seem as good on further thought. First there are the reports from people with the same engine on three airframes. There could be a bunch of reasons for that in addition to the wear in of a piston ring. There are a multitude of potential resonances. Just for starters there is the first bending mode of the body both vertical and horizontal. Then the first body torsional mode. Bending modes for wings, tails and rudder. A mode for the fuselage bouncing on the gear on the ground. Another for the gear bouncing like a tuning fork in the air. Not to mention higher order modes and coupling between these modes. Each of these will vary due to variations in stiffness and weight between airframes. Damping ( inverse of the tendency to peak at resonance) will vary with wood quality, joint quality, and probably most important, variations in covering tension.
Has anyone noticed differences between really hot or really cold days. Or between really humid and really dry days?
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