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Old 10th January 2008 | 19:33
  #20 (permalink)  
Dave_Jackson
 
Joined: Apr 2003
Posts: 1,635
Likes: 1
From: Vancouver, BC, Canada
Mart, you say
So basically your model of combined blade element and momentum method predicts an FM of 0.7.
It's not MY model. It is the 21 steps directly from pages 69 to 72 in Prouty's book, as previously mentioned. You may wish to read throught the 21 steps.

This depends on the Cl vs AOA and Cd vs AOA graphs used (not shown).
I selected the 8-H-12 profile, as shown on the forms.

The general wisdom is that Cl/Cd for a flat aerofoil is lower than for a fat aerofoil.
? The Cornu airfoil is cambered.


slowrotor,
Thanks for the thought of using X-plane.

Blade Element Theory is a standard method; perhaps with some users tweaking it a little. One concern might be that it was developed for larger helicopters and it may not scale down well to the very small helicopters.

Dave
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