"d&tm" wrote in message
...
The 4 degrees comes from my theory books ( trevor Thom) and I understand
it
is pretty much the same for all light aircraft. which is why the wing is
usually set at this angle when the aircraft is level ( the riggers angle I
believe they call it)

The angle is called "angle of incidence", and while not just one factor
controls the choice of angle of incidence, most often the primary factor is
the desire to keep the cabin relatively level during cruise. Cruise speed
usually results in an angle of attack well below the "best glide" angle of
attack (and an airspeed well above Vbg).

I don't know off the top of my head what a typical best-glide angle of
attack is, but it's above a normal cruise angle of attack, and if 4 degrees
is a typical angle of incidence (and thus a typical cruise angle of attack),
the a typical best-glide angle of attack would be greater than 4 degrees.

Pete