Now i'm feeling dizzy after watching that

damn that is cool

bingles said...

Lets see who can best describe dynamic soaring then...

Ultra efficient RC gliders or slope soarers using the wind on the back side of the hill.

they fly out the front to get lift and speed, then they go over the back where there isnt much wind ( i dont know the dynamics of it all ) and go faster...

It's all to do with lift to drag. If you can make the wings work harder the 1/20 th of the lift, or thereabouts, which is in the forward direction also increases. Full-sized gliders also go faster with a bit of weight on board, provided you can get them started and the thermals are strong enough to keep them up.

If you can't add weight you can make the wings work harder by flying in tight circles. That glider is doing 375 mph and completing one circuit every 3 seconds. That's 166 metres per second so the circle is 500 metres in circumference. Check my sums it's getting ridiculous. That's a 79 metre radius. Centrifugal acceleration a = v^2/r or 35.5 g s !!
No wonder they use a bit of carbon fibre in the construction.

They then use the velocity discontinuity to pump up to speed. As they move from the part of the tight circle in the high wind to the that of the low wind they get an extra boost from below the wing. More forward lift and away they go. Same effect going from slow air to fast air on the other side of the circle.

No that's wrong, it's a component of gravity that is in the forward direction on a regular glider, not aerodynamic lift so the analogy is incorrect.

The reason the glider is pulling 35 g s is so it can do a U turn without dropping too much speed. Or to stay within site of the pilot maybe.

The ridge provides a 45 mph wind above a pocket of still air. Lets say the glider is coming downwind in the 45 mph airstream with an airspeed of say 300mph.

As it drops into the still air its airspeed will become 345 mph. ( But no change in ground speed speed for an observer on the ridge top )

Now look at the problem from the still air frame of reference. The glider can then do a U turn in the still air and not lose all of that 45 mph boost in airspeed. Ignore gravity we're at 35 g s.

Having done the U turn it can rise into the fast air and pick up another 45 mph of airspeed. Switch frame of reference and have the glider do a U turn in the fast air without losing too much airspeed.

So while it can do the U turn without dropping 45mph it will keep going faster and faster.