Humidity Dependence

[j...@oxaero.com]

Four partial polars taken a year ago exhibited a curious performance notch at 49 or 51 KIAS, depending on glider weight, and very large amplitude variations with airspeed changes of just 1 or 2 kts.  Going back to archival weather soundings for regional relative humidity readings aloft has revealed a strong falling off of the upper-wing-surface leading-edge tape effect when the RH exceeds about 70%.   No such dependency has been found for the lower-wing-surface only application.  The notch feature and the HR dependence are important clues in forming a theory for the rear-facing step effect.  You can read a brief article about this at http://www.deturbulator.org/Progress-LET-Humidity.asp .

Jim Hendrix