HGFA Skysailor Magazine

24 SKY SAILOR September | October 2018 D uning requires precision low level flying. Turns have to be executed in such a way as to stay in the lift band, which is rather small. An additional factor will be the turbulence. A good soarable wind is often accompanied by a sizeable surf that is capable of producing low level turbulence; nothing too dramatic, but enough to ruffle your tail feathers from time to time. The factors that make some surprisingly small dunes soarable are a combination of wind gradients and ground effect. Not utilising these will have you landing lickety-split on the beach. Using wind gradient to get your turn in and stay in the lift band is a form of what I call ‘assisted dynamic soaring’. The albatross uses this to great effect – flying downwind through the wind gradient then turning into wind to climb up through the wind gradient. We can achieve something similar by building airspeed while travelling along the dune, in fact even right down to the bottom, and then turning and climbing in the wind gradient. As the energy runs out, we are then flying level again within that tiny lift band. This technique also works for getting the initial turn in as you take off. When a wind gradient is present on take off, we climb up in the gradient by pushing out. When we top out we start coming down again. If no turn has been executed, off to the bottom of the dune you go, however, if a turn has been made, now we are pointing down the first beat but tucked into that minuscule lift band. Using ground effect: We all know that the efficiency of a wing is greatly improved by ground effect, so again, we use this in duning to keep soaring. Getting that turn in and then flying with the wing tip very close to the ground gives us this benefit. However, the increased lift generated by the wing that is closer to the ground will try to turn you out of the lift band and needs to be countered with a good deal of roll input. This all takes precise flying control, a good handling glider and plenty of practice. Once you get the hang of it, it is fantastic fun. As long as you are not flying in really strong winds and flying obstruction free dunes, the risks are relatively minimal. Having said that, if the wind is not close to straight on, then ground speeds can be quite high. It is a common misconception that duning is done in strong winds. True to say, a good duning day will be one that is blown out on a big hill, but I like to be flying in about 15 to 18kt of wind. This lets me fly at min sink and best glide speeds. More wind requires more speed and the floaters have a limited performance range, so the extra wind becomes self-defeating and it quickly becomes gale dangling. Tuning for the dunes is all about handling, handling and handling, and let’s not forget some energy retention and performance, but it is at the slow speed end that this matters. Efficient flat turns and confidence in your glider are what count. Most dedicated duners have slacker settings for duning; less sail tension or an extra shackle in the cross- tube tensioner. I have gone for a VG on my Discovery Skyfloater, which lets me run it super slack. In future, perhaps more work can be done to optimise the duning glider. The nature of this aspect of the sport means more experienced pilots are likely to do this kind of flying. The weapons of choice are modern floaters. I already hear grumblings of the latest and greatest Mk 2, 3, 4 et al, while It seems easy enough when you look at the videos, but doing it can be a humbling experience even for the high airtime pilot. by Bil Pain Flying the dunes, the wee ones