I completed a 96" 16.5lb plane powered with a 35cc running a Vess 20A at the end of April and have flown it now for two months. It performs fairly well and yields large loops and will climb vertical as high as I normally go for a hammerhead or spin. Well, yesterday it performed better than ever... yielding nearly unlimited vertical climbs and this very shortly after takeoff carrying the full fuel load (16 oz).

The most notable difference was a lower humidity yesterday, though the temperature was about ten degrees fh warmer.

Is it typical to get better performance with lower humidity? Is the variation seen yesterday an indication that the engine was not tuned optimally for the more humid conditions or is poorer performance in humid conditions normal?