It has slowly dawned on the soaring community that travel in any direction is possible merely by working surface-boundary-layer wind gradient. Strong wind gradients of all kinds offer this potential. RC soaring has even reached incredible speeds well over 400 mph. Similarly AWE theorists can now look beyond tethered foil pairs working gradients to tetherless single aircraft flying patterns to exploit the same effect. The variations are endless, for example an aircraft looping in place in the surface gradient could transfer supercapacitor charge to the ground by "touch-&-go" contact by trailing electrodes, greatly mitigating conductive tether-drag limitations.

 

The recent debates & clear success in DDWFTTW (2.8x windspeed downwind) has given us a fine lesson in the physics required. We now see a deep commonality of all sailing methods with land, water, & air interfaces seen as tappable differential gradients. It will take some really loopy thinking to work out all the basic points of "sailing in 3D", as Wayne put it, but for now lets review the existing primitive state of understanding, & the topic will surely develop.

 

 

 

A quote from the page-

 

In his 1975 book Streckensegelflug (published in English in 1978 as Cross-Country Soaring by the Soaring Society of America), Helmut Reichmann describes a flight made by Ingo Renner in a Glasflügel H-301 Libelle glider over Tocumwal in Australia on 24 October 1974. On that day there was no wind at the surface, but above an inversion at 300 metres there was a strong wind of about 70 km/h (40 knots). Renner took a tow up to about 350 m from where he dived steeply downwind until he entered the still air; he then pulled a sharp 180-degree turn (with very high g) and climbed steeply back up again. On passing though the inversion he re-encountered the 70 km/h wind, this time as a head-wind. The additional air-speed that this provided enabled him to recover his original height. By repeating this manoeuvre he successfully maintained his height for around 20 minutes without the existence of ascending air, although he was drifting rapidly downwind. In later flights in a Pik 20 sailplane, he refined the technique so that he was able to eliminate the downwind drift and even make headway into the wind.

In the late 1990s, radio-controlled gliding awoke to the idea of dynamic soaring (a "discovery" largely credited to RC soaring luminary Joe Wurts). Radio controlled glider pilots perform dynamic soaring using the leeward side of ground features such as ridges. On ground features whose shape combine with the prevailing wind direction to produce a stagnant or reverse flow on the leeward side, the velocity gradients can be much greater than those used by birds or full scale sailplanes. These higher velocity gradients allow for correspondingly greater energy extraction, although at the cost of high airframe loads imparted at the boundary between the prevailing wind and the stagnant air. Due to the strength and stiffness needed to withstand these high loads, dynamic soaring models are commonly built using composite materials. As of May 2010, the highest reported speed for radio control dynamic soaring was 445mph (716 km/h).^[2]