Rear wing/spoiler
08-23-2010, 01:19 PM
#22
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Either way of measuring it is fine. The only reason for measuring it is to get a starting point, or return to some setting that worked. Without a lot of smoke or tuft studies, you wouldn't know what the angle of the incoming air is anyway.
The reference AOA line for the data provided by APR is across the upper surface, probably because it is easy to measure. They sell a cheap level and embossed APR bar to bridge across the high points.
The Gurney flap will probably increase the effective AOA about 1 degree, based on what they do to other high-lift airfoils. I measure from the front of the wing to the Gurney bond surface (like the 2.4 degree example above).
The reference AOA line for the data provided by APR is across the upper surface, probably because it is easy to measure. They sell a cheap level and embossed APR bar to bridge across the high points.
The Gurney flap will probably increase the effective AOA about 1 degree, based on what they do to other high-lift airfoils. I measure from the front of the wing to the Gurney bond surface (like the 2.4 degree example above).
Bob
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08-24-2010, 12:18 PM
#23
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That is the way I measure it as well. APR specifies there angles based on a flat bar across the top. it is easy to measure that way. The Gurney flap will increase the amount of angle and down force you can get before you reach a stall condition by having too much angle.
Bob
Bob
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08-24-2010, 12:54 PM
#24
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From Wikipedia:
http://en.wikipedia.org/wiki/Gurney_flap
The Gurney Flap (or wickerbill) is a small flat tab projecting from the trailing edge of a wing. Typically it is set at a right angle to the pressure side surface of the airfoil,[1] and projects 1% to 2% of the wing chord.[2] This trailing edge device can improve the performance of a simple airfoil to nearly the same level as a complex high-performance design.[3]
The device operates by increasing pressure on the pressure side, decreasing pressure on the suction side, and helping the boundary layer flow stay attached all the way to the trailing edge on the suction side of the airfoil.[4] Common applications occur in auto racing, helicopter horizontal stabilizers, and aircraft where high lift is essential, such as banner-towing airplanes.[5]
The device operates by increasing pressure on the pressure side, decreasing pressure on the suction side, and helping the boundary layer flow stay attached all the way to the trailing edge on the suction side of the airfoil.[4] Common applications occur in auto racing, helicopter horizontal stabilizers, and aircraft where high lift is essential, such as banner-towing airplanes.[5]
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08-24-2010, 01:13 PM
#25
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In theory they should increase total down force, the L/D ratio and keep flow attached to the under side of the wing better allowing greater angel of attacks. Very little draw back other than a bit more drag but that can be offset by dialing in less angle of attack while still having more downforce per drag amount.
Bob
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