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Hi Bob,
Thanks for the info on L2 drag.
Always heard that windmilling props make a lot more drag than stopped props.
I like to use Hoerner's approach in his Fluid Dynamic Drag book... wetted area, with numbers from a variety of complete airplanes.
He gives a Cd total wetted area of .004 for P-51, .005 for the Bonanza, and .009 for the Cessna 170.
For a Cd wingarea, he gives .017 for the P-51, .016 for the Bonanza, and .029 for the C-170.
I suspect the Cd wet for the L235/320 should be somewhere between .004 and .005... and was looking for some confirmation.
Terrence
L235/320 N211AL
----- Original Message ----- From: "bob mackey" <n103md@yahoo.com>
To: <lml@lancaironline.net>
Sent: Monday, October 01, 2007 05:43 PM
Subject: [LML] Drag coefficient
I can't separate drag coefficient and area, because I haven't measured
the area, but we don't really need to. The equivalent (total) drag area
is:
C*A = Drag / ((rho*v^2)/2) = 0.343 m^2 = 3.7 ft^2
Which is quite a bit greater than the ~1.6 that Paul Lipps sees in cruise.
I'll take that to mean that the prop/engine drag is about 2.1 ft^2
equivalent drag area, assuming his airframe and mine are otherwise similar.
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