- Wed Jan 29, 2014 4:37 am
#344391
The previous post suggested that the glider is affected by the prevailing wind when it is flying in a gradient. A pilot may feel changes in that gradient.
If there is no gradient in the local air mass, the glider/pilot will not feel any change of "wind" direction, or of "wind" strength, on the glider, when it is climbing or dropping, or turning in or out of "wind"
A pilot could be justified in thinking about the prevailing wind direction, when flying in a gradient.
In the Reichman example there is a climb in to wind and a drop with a tailwind.
Looking at a pilot slope soaring, trying to get hooked into a small well defined thermal that is passing through. If using his vario, the hanglider pilot ends up perfectly centered in the thermal, there is no gradient, so there is no "feel" from the "prevailing wind".
If he has no vario, he has to rely on feel. He can decide not to fly perfectly centered, but to deliberately fly slightly off center so that there is enough feel to allow him to judge where he is in relation to the thermal core.
On entering directly the glider will pitch up, entering to one side the pilot counters the rising wing, and turns into the thermal, or quickly turns around if there is room, and hopefully enters more directly.
Entering with speed in hand, the pilot climbs away from the hill but turns back as speed is scrubbed off, and before he drops out the far side. If he judges that there is room to complete a 360, he turns back to the hill in a tailwind ready to turn a 180 as soon as he feels a slight drop, or he decides that that is close enough.
The high banked turn is made no closer to the hill than he would normally fly. He is aiming to circuit in the gradient to position himself by "feel", not fly through all the gradient to try dynamic soaring. (Like Renner......Did he fly through all the gradient to stay circuiting over one place on the ground?)
The turn obviously should be made quickly, to avoid dropping out the back of the thermal, or flying into the hill if the pilot has misjudged it.
The pilot anticipating and trying to forestall the drop before the sharp turn, flies back then rolls the glider up and bangs it flat as he turns back into wind. it is one sharp movement .The glider wants to be completely flat before it impacts the gradient going back in, and is pitched up as it flies away from the hill. The control bar has to be pulled in and forcefully restrained while the glider is climbing. It can be eased out only as the pull (against the pilot's efforts) on it, diminishes.
Turning (say) to the right (I always turned the same way....one less decision) when climbing into wind scrubbing off speed, pitched up, with the glider "flat" the glider will tend to yaw into the gradient, into increasing "wind". Towards the end of the climb as the glider slows, the pilot may have to put more effort into resisting the inner wing rising. That will lessen as the pilot reaches the core (or what he thinks is the core).
At the top of the climb the pilot is flying just above minimum sink speed, but with a bit of speed in hand. he then turns back to the hill and repeats the maneuver.
After a circuit roughly mapping out the thermal he can close the pattern up, make it smaller, but each section should have roughly the feel each time round.
Flying out from the hill turning, if the glider does not lift a wing, or lifts with less force he could assume he has moved sideways, too far through the core, so he continues quickly round to the steep banked turn back into "wind". He is aiming to keep a regular, similar lift of the wing each time round. If he is circling to the right, clockwise viewed from above, it will always be the right wing that lifts.
If he has not flown too far back, there will be no pause before the glider impacts the gradient and climbs, after he has rolled it flat. If he flies too far forward the glider drops out of the thermal. Side to side positioning relies on the consistent regular resisting of the inner wing lifting.
It may help if the glider is trimmed slightly tail down in normal flight, so that the bar is always slightly pulled in. but not enough that it stalls. (on the point of wallowing)
The cross bar is better at chest height in normal flight. The modern position is to have it almost under the chin, which does not really help if you have to throw the glider about.
Older gliders had keel pockets instead of a Y shaped bridle in the lower rear rigging. The sail moving over easily in the climb, with a keel pocket, might make things easier.
The ideal to try it, is probably a larger sized single surface glider.
Having the hang point on the keel instead of the mast may also be an advantage. More effort means more feel, more sensitive feedback.