On Sat, 17 Jul 2004 00:36:28 +1000, Graeme Cant
wrote:


Thank you, Chris. My 20B had a 3.5 hole drilled when we bought it but I
had no advice on its purpose or use. I was puzzled when I couldn't
relate the Flight Manual descriptions to what my glider had. Eventually
I worked it out.

I would be interested in any advice anyone can give on the use of 3.5.
I tend to use it for nearly all thermalling and only use 4 for landing.
Am I right? Is a 3.5 hole common? Did Schleicher's get it wrong?

It depends what you use 4 for: For thermalling at normal bank angles
(20-30 degrees) 3 is the better setting (the 20 converst excessive
speed into height a lot better in 3 than in 4), but very tight turns
combined with high wing loading (or forward CG) need 4.

Many 20 owners drilled the 3.5 hole, but I have to admit that I tested
this setting and I never felt 3.5 to be an advantage over 3 (I hold
the flap handle at 3.5 before I decided not to drill a hole there). At
3 the nose is significantly higher than in 3.5, but I think the 20's
airfoil loves high AoA's. If the AoA of the 20 is too low (in other
words: Flap setting too positive for current airspeed/g-load
combination), the drag rise is drastic - very easy to feel the
deceleration.

One more thing why I love the 20: The flap handle tells you which
position it wants to be in - it moves itself into the optimum position
(if you help it overcome the friction with your hand).

Bye
Andreas