APR Wing question about the angle
Joined: Oct 2010
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The iPhone has a level app. It's hidden within the compass app (slide left).
I believe the AOA of that wing is measured relative to the airflow - not the level ground. The OEM hard top creates a -12° airflow across the back of the car. This means, a wing set to 0° relative to the ground (level) has an effective AOA of +12°.
There is tons of discussion on this point in other threads. I'm not trying to start that discussion all over - just making you aware. Please follow those threads for the detailed points ...and counterpoints.
I believe the AOA of that wing is measured relative to the airflow - not the level ground. The OEM hard top creates a -12° airflow across the back of the car. This means, a wing set to 0° relative to the ground (level) has an effective AOA of +12°.
There is tons of discussion on this point in other threads. I'm not trying to start that discussion all over - just making you aware. Please follow those threads for the detailed points ...and counterpoints.
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Joined: Mar 2014
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The iPhone has a level app. It's hidden within the compass app (slide left).
I believe the AOA of that wing is measured relative to the airflow - not the level ground. The OEM hard top creates a -12° airflow across the back of the car. This means, a wing set to 0° relative to the ground (level) has an effective AOA of +12°.
There is tons of discussion on this point in other threads. I'm not trying to start that discussion all over - just making you aware. Please follow those threads for the detailed points ...and counterpoints.
I believe the AOA of that wing is measured relative to the airflow - not the level ground. The OEM hard top creates a -12° airflow across the back of the car. This means, a wing set to 0° relative to the ground (level) has an effective AOA of +12°.
There is tons of discussion on this point in other threads. I'm not trying to start that discussion all over - just making you aware. Please follow those threads for the detailed points ...and counterpoints.
angles and speed thread
feel free to share if you have links
Joined: May 2011
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As mentioned above, you want the same AoA along the length of the wing with respect to local airflow. I never really understood the concept for the OEM hardtop, as the aero is super shitty--flow detaches immediately. It's raked at far too high an angle to keep airflow attached, so it's not like its hitting the center chord at an angle. It's just low velocity turbulent air. Here's a good flow channel study showing that: https://youtu.be/1c_QW1QBgiw?t=1m9s
edit:// point of reference, I run my GT250 in free stream air above the roof, and at 0 degrees AoA, the car pushes hard at high speed.
edit:// point of reference, I run my GT250 in free stream air above the roof, and at 0 degrees AoA, the car pushes hard at high speed.
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From: Fort Walton Beach, FL
https://en.wikipedia.org/wiki/Gurney_flap
The Gurney flap increases the maximum lift coefficient (CL,max), decreases the angle of attack for zero lift (α0), and increases the nosedown pitching moment (CM), which is consistent with an increase in camber of the airfoil.[4] It also typically increases the drag coefficient (Cd),[17] especially at low angles of attack,[18] although for thick airfoils, a reduction in drag has been reported.[19] A net benefit in overall lift to drag ratio is possible if the flap is sized appropriately based on the boundary layer thickness.[20]
The Gurney flap increases lift by altering the Kutta condition at the trailing edge.[4][6] The wake behind the flap is a pair of counter-rotating vortices that are alternately shed in a von Kármán vortex street.[21] In addition to these spanwise vortices shed behind the flap, chordwise vortices shed from in front of the flap become important at high angles of attack.[5]
The increased pressure on the lower surface ahead of the flap means the upper surface suction can be reduced while producing the same lift.[21]
The Gurney flap increases lift by altering the Kutta condition at the trailing edge.[4][6] The wake behind the flap is a pair of counter-rotating vortices that are alternately shed in a von Kármán vortex street.[21] In addition to these spanwise vortices shed behind the flap, chordwise vortices shed from in front of the flap become important at high angles of attack.[5]
The increased pressure on the lower surface ahead of the flap means the upper surface suction can be reduced while producing the same lift.[21]
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APR has data on the Gurney flap on their web sight. Keep in mind all their tests are done in laminar air flowing parallel to the ground, so actual results will vary, but that should give you an idea in terms of magnitude.
I have the Gurney flap and my car pushes with a 4" splitter and hood vents. It is attached with double-sided tape, so I'm sure something will break if I try to remove it. I might try reducing the AOA (it is level now, so about 12° relative to airflow).
I have the Gurney flap and my car pushes with a 4" splitter and hood vents. It is attached with double-sided tape, so I'm sure something will break if I try to remove it. I might try reducing the AOA (it is level now, so about 12° relative to airflow).
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