Robert Ehrlich wrote:
..../...
Anyway the words "GC hook" are a misnomer, since I know no glider where
this hook is juste below the CG, all have it more or less ahead of the
CG. "Winch hook" or "ground launch hook" would be more appropriate.


I've not measured any full size gliders, but the following procedure
gives the hook position for free flight towline model gliders. I use it
to set up F1A class models:

- locate the CG on the wing's datum line.
- project a line downward from this point and sloping forward at 18
degrees from the vertical.
- the line should pass through the towline attachment point on
the hook.

A tow hook fitted at this point gives a good stable, controllable launch
for a model with its trim fixed to glide at its minimum sinking speed.
Note that this procedure will place the tow hook further forward on
models with a high wing mount than on those with a minimal wing pylon.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |