911slf,
thanks for the link to Seibel's article. I understand why you haven't read it all. It is very long (Safari wants 89pp to print it!) and to my taste somewhat meandering. However, it seems Seibel has seriously tried to experiment and can describe what he found in terms mostly familiar to an aerodynamicist. I have read about a quarter of it so far.
Here his answer to my question, from Part IV, Section "What Makes an Aircraft Turn", second paragraph, first sentence: "In hang gliders, the wingtips provide the same function as would a vertical tail". He is talking about the action of the VS during sideslip.
Originally Posted by 911slf
It does touch upon a point that has confused me in the past. Hang glider pilots are encouraged to let the nose up a bit in turns, which always seemed a bit counter intuitive to me, given we normally fly not much above the stall.
That seems to me straightforward. Your lift vector is tilted by the roll, so there is a lower component of lift in the vertical (earth-negative-z) direction and so you need to increase total lift in order to match weight with this component if you wish to stay level, and you do that by increasing AoA. That's why you need elevator in a level turn in an aircraft, and why (I imagine) you need to "let the nose up" in a hang glider.
Seibel suggests that some instructional books suggest this has something to do with yaw/sideslip, and that they are wrong. I agree with Seibel.
PBL