On Sunday, May 3, 2020 at 8:45:27 PM UTC-7, 2G wrote:
On Sunday, May 3, 2020 at 3:05:50 PM UTC-7, RR wrote:
Slightly related, bicycle and motorcycle dynamics (or any two wheeled vehicle) are quite a complex subject and only recently fully described mathematically (in the last ten years or so). The solutions are too complex to solve so numeric methods are used.

Not only complex but very few people who ride bikes or motorcycles even know how they initiate a turn. Most assume that if you want to turn left, you pull back on the left handlebar, but in fact to turn left (while moving at a reasonable speed) you push on the left handlebar. The dynamics cause the bike to lean left, and the geometry causes the wheel to turn left to compensate. It is one of the reasons it is hard to learn how to ride a bike, the handling changes with speed.

Try it, push lightly with your fingertips, the handlebar will push back after the turn is initiated. Hang glider turning dynamics are related.

Rick

All turns, whether on the ground or in the air, have one immutable thing in common: there must be a lateral force to cause an object with momentum in a straight line trajectory to change that trajectory. A wheel can have its axle turned and the tire generates this force by friction with the ground, as occurs while executing a turn in a car. If some other force is applied to the car to turn it, such as a wind gust, the tire will resist this turning force until the applied force exceeds the grip of the tire. The car will then skid. The same thing is going on with a glider's wing wheel as it is being forced to turn around a curve by the towing vehicle. This lateral force will be the same regardless of the design of the wing wheel, it will just be less apparent with some than with others. This force MUST be transmitted to the wing - there is no other place for it to go.

Tom

Unless you are doing some high speed slalom with your tow bar, the sideways forces on the glider are negligible. This is not what creates the scrubbing and hopping that is being discussed. If you ARE doing high speed slalom with your glider, then the forces contributed by each component depend on the tire traction and slip angles. Since the glider is nearly balanced on the main, it will carry perhaps 95% of the vertical load, the wing wheel carries only slightly more than it's own weight. The main also has a much larger contact patch than the wing wheel, and much stiffer mountings. So it (and the tow bar) would carry nearly all of the lateral force. Which, for normal tow out ops is nearly zero.