On Dec 8, 5:21 pm, "kirk.stant" wrote:

We start with the minimum sink speed (specifically, the
point on the polar we want to thermal at), add speed for ballast, then
add speed for bank angle, then come up with an adjusted airspeed that
approximates our ideal AOA for the selected gross weight and bank
angle.

Using AOA directly (once one has chosen where on the polar one wants
to thermal at) eliminates the need to make all those guesses. The
wing does it all, automatically.

I realized a bit late that what I really meant to say is that when
using airspeed, we find the performance point on the polar we want (L/
D max, min sink, stall, whatever), then move the polar for ballast and
bank angle, and use the resulting adjusted airspeed. This is made
necessary when using the common sink rate vs airspeed polars for all
the desired conditions of ballast and bank angle. Using AOA directly
(which would require the polar in sink rate vs AOA and L/D vs AOA)
eliminates the need to move the polar (and refigure the resulting
airspeed), as the AOA for a specific flight condition is not affected
by ballast or bank angle.

Has anyone seen glider polars with sinkrate plotted against angle of
attack? That would be interesting. I've seen plots for aircraft of
Cl vs AOA, and L/D vs AOA, neither of which is very useful in this
discussion.

I should have listened up more in aero classes, long time ago...

Kirk