If you have not already seen it, you might learn something from this:

http://uras.gliderpilot.net/?op=s2&id=35764&vt=

(You may have to register and log in to read the explanatory text, but I think you can click directly onto the related video without that if you wish – http://www.youtube.com/watch?v=9Kx-b...LQPQ nZBqf_Ih

Chris N