In article , Andy
Durbin writes
Ian Strachan wrote in message
...

A point I made in an earlier contribution to this thread seems to be
being missed but I think is important. That is, where a glider has two
hooks, the rear hook can be placed close to the true C of G position.
With only one hook, the position will normally be somewhat forward of
the C of G position and will be a compromise rather than a true C of G
hook.

In other postings people talk generally about "CG hooks" without making
the above distinction, which could be critical to handling on the
launch. "Belly hook" might be a better term, and many will not be true C
of G positions unless a nose-hook is also fitted.


In a previous posting I stated that the CG hook on my ASW 28, and the
only hook on my ASW 19, are in the same place. They are both just
forward of the main gear and inside the gear doors. I think they
would both be considered to be true CG hooks even though they are
forward of the CG.

When you say that "the hook is forward of CG" you seem to imply a static
measurement.

The static on-the-ground measurement of where the glider GC is with
respect to the belly hook position is not what matters. It is what
happens on a launch (dynamic, not static conditions). What matters is
the angle-of-pull of the cable with respect to the centre of motion and
control effectiveness of the glider in that dynamic launch situation.

If you measure where the CG is statically, that is, on the ground, and
placed a tow hook directly underneath it, I think that you would find
the subsequent launch pretty unstable either on winch or air tow.

--
Ian Strachan
Lasham, UK