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OTHER: Aerodynamics - Blade Profile - VR-9

Overview:

Centers, forces, moments, vectors, etc. related to the VR9 airfoil.

For information related to the specific blade for the Unicopter see: UniCopter ~ Rotor - Blade - VR-modified

Drawing:

Characteristics: The 3 values below that are in light grey are currently wrong

Thickness	t/c	= 0.06
Leading Edge Circle	r/c	= 0.0113
Center at	x/c	= 0.01055
Center at	y/c	= 0.004

Airfoil with Different Angles of Attack:

Airfoil integral coefficients: Cl (lift), Cd (drag) and Cm (aerodynamic moment in respect to 1/4 of the chord). It's important to note that Cd is theoretically null in a 2-D non-viscous subsonic flow; hence this number is a measure of the numeric errors in the code and in the choice of the points.

The Cm is considered positive when pulling up.

The following calculations are from the freeware program NVFoil.

ά		[alpha] The angle of attack is the angle between the airfoil chord and the velocity vector.
c_l		Coefficient of lift; two-dimensional
c_d		Coefficient of drag; two-dimensional
c_m0		Coefficient of moment; two-dimensional. (pitching-moment coefficient) @ 25% of chord
x_cp		Location on X-axis of center of pressure as a percentage of chord from leading edge.
Airfoil & Tab	ά		c_l	c_d	c_l^3/2/c_d	c_m0	x_cp
VR-9	0		0.026	-0.002		-0.005	44
	1		0.148	-0.002		-0.006	29
	2		0.270	0.000		-0.007	28
	4		0.514	0.010		-0.009	28
	6		0.755	0.027		-0.010	27
	8		0.993	0.051		-0.011	27
	10		1.227	0.082		-0.012	27
	12		1.455	0.119		-0.011	27

General comments related to the VR-9 airfoil:

The VR-9's center of lift is quite far aft at 0º angle of attack but quickly comes forward as the angle is increased. I would guess that this aft center of lift is not of much concern because the lift at this angle is very small therefore the moment will be very small

Last Revised: Sunday, February 11, 2009