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Thanks Bob.

I wrote that at home with out my Von Doenhoff Theory of Wing
Sections so I got it wrong. Here is the correct formula.

C sub D = C sub d + (C sub L)^2 / pi * (aspect ratio)

C sub d is the section drag coef. which we are summing up.

So you have to multiply (CsubL^2/(pi*AR)) times air density
times velocity^2 times blade area I think. I need to work
on this a bit more.

Aspect ratio  is also span squared divided by wing area.
Which is easier to implement.


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Hi Bob,

I added a couple of columns for coef. of lift and coef.
of drag as they vary with Mach number. This is
important as so many prop tips operate near Mach one.
I have not chosen the values yet. I hope it does not bust
the rest of the spread sheet. Here is a couple of scans on
the subject from Theory of Wing Sections.
I was kind of surprised about the temporary drastic rise in
in the lift coef. at a 2 degree and above angles of attacks
with mach number. I think we should start with the 4 degree
angle of attack curve. There is a huge rise in the coef.
of drag starting at only .7 Mach at 4 degrees angle of attack.

We will have to add a calculated column for Mach number.

As far as the induced drag torque is concerned probably using
the Coef. of lift and the overall  aspect ratio
for the last area segment torque might work in the absence
of a full blown 3D CFD.

Paul Lamar ...No rotor no motor.

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