On Sunday, November 10, 2013 10:07:19 AM UTC-5, wrote:
An eternally fantasized about possibility... But now, except for a few famous efforts in very strong wind shear (As I recall, Ingo Renner reportedly did it with a 40 mph wind shear or something like that) can we do this in real gliders?



I tried for a bit in condor, but it doesn't look like its wind shear model is accurate enough. (I was trying to dip in to the lee of a ridge like the RC modelers do, but it looks like condor is set up with the same wind and sink behind the ridge, not the wind shadow or rotor).



These nice videos suggest that somebody somewhere has done the quantitative calculation -- including all losses, how much wind shear (mph/ 1000', or kph / 1000 m) does it take to dynamically soar a modern sailplane? Can we do it with current vnes? The duckhawk is designed with much higher vne and g loadings which make dynamic soaring more efficient. How much shear does it need?



John Cochrane

It's been done for a number of situations. For those with an AIAA paper subscription "Optimization of Dynamic Soaring at Ridges" is a nice, concise example by the same folks who made the video.

The cliffnotes version is that for something like a 15m glider, it would take about 6 knots of wind and the peak airspeed would be around 90 knots. This does assume a very sharp shear model though (among other simplifications), to my knowledge no one has actually gone out and made a high resolution map of what the separated region behind a ridge looks like.