Four sets of performance data with leading edge tapes only
j...@oxaero.com
All,
Ok, here are four sets of sink-rate measurements on my glider with the only (effective) mod being the leading edge tape (www.deturbulator.org/LET-Yourself.asp).
Observations:
1. The red data were take two weekends ago. The was a fairly wide range of values between the beginning and end of the two speed runs that produced the performance peaks. The plotted values are averages in each case. Also, the all-up weight was 32 pounds less for the red flight compared to the others. As you can see, that change had a marked effect on the performance notch, moving it right by 2 KIAS and possibly reducing the depth of the notch. By my estimate, in the 50 KIAS speed range, each knot corresponds to a 0.2 degree change in AOA, so the shifted notch corresponds to a -0.4 change in AOA.
2. There is remarkable agreement between the 1/15/2011 (red) and 4/2/2010 (blue) curves. The agreement at 60 and 65 KIAS indicates that the severe performance loss at 60 KIAS is real, not bad data as I had hoped. Except for the notch shift and irregularity (error, I think) in the 1/15/2011 data, these are essentially the same curves.
3. The overall pattern repeats consistently, indicating, to me at least, that the phenomenon is real. Under the right conditions, very large performance enhancements can be achieved at glider Reynolds numbers in smooth air over limited speed ranges. Therefore, this needs to be taken seriously by the aeronautics community.
4. The large deviations in the amplitude swings on different days is not clear to me. I need to look back at temperatures, humidity levels and altitudes for clues.
Jim Hendrix
417 N. 11th Street
Oxford, MS 38655
662-234-0492
j...@deturbulator.org
www.deturbulator.org
