On Sat, 24 Apr 2004 14:04:11 +0200, Andreas Maurer
wrote:

On Fri, 23 Apr 2004 20:14:02 GMT, "Bill Daniels"
wrote:


A perfectly symmetrical glider with a perfectly smooth polar and
frictionless controls SHOULD develop a spiral dive from a hands off turn.

How does this explain the behaviour of non-radio-controlled model
gloiders that return to level flight anytime? They are built perfectly
symmetrical, have a smooth polar and no controls at all...

Free Flight gliders - at least in the F1A class, which I fly - are not
aerodynamically symmetrical: There is always more wash in on the inner
wing in the turn and the rudder is set into the turn, giving a
crossed-controls effect. Without the differential wash-in most designs
will have nasty spiralling tendencies.

The flight regime is somewhat different, too. The model is trimmed at
min. sink (about 8-10 kts) and is flying in a still air circle that
requires 40 - 60 seconds to complete. That's a 30 - 40 m diameter
circle being made by a 2.5 m span model, which is a relatively much
larger circle than we tend to use in our sailplanes and yet is small
enough to fit easily inside a thermal column.


--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :