GT4 Wing Development pt3

GT4 Wing Development pt3

March 30, 2020

Swan neck mounts vs. Standard mounts

To swan or not to swan, that is the question! A huge design element to a rear wing is the mounting style! Traditionally, wings are mounted from the bottom or even the end plates on the sides. On the 981 and even the 718 GT4, we see a bottom mount where the wing stands simply attach to the wing from below. Straight forward and a very obvious way to mount the wing onto a car. Lately, you may have noticed some wing mounting styles that attach from above the wing such as the 718 GT4 clubsport.

718 GT4 Clubsport Swan Neck

This style mounting has been called a swan neck mount for the way the mounts appear. The theory behind the swan neck is to reduce the interference of the mounts on the air flow under the wing. Near the limit at high angle of attacks or even during cornering, the flow under the wing can be sensitive to disruptions in flow and can separate from wing's surface reducing the wing's efficiency and ability to produce downforce. Swan neck mounts change this disruption by attaching on the top of the wing where it is not crucial to have smooth flow. Let's take a look at some fancy results from a CFD simulation. Here is the standard bottom mount of a new wing we are developing (sneak peak) at 5deg AOA.

Standard Bottom MountStandard Bottom Mount Zoomed

And here is the same wing at 5deg AOA but with a smooth bottom surface and modeled with swan neck mounts.

Swan Neck MountSwan Neck Mount Zoomed

Take a look at both these areas up close! As you can see, the area behind the wing stand is quite messy. The flow starts to detach from the surface of the wing quite easily and you can visualize how much of the surface area of the bottom of the wing is affected. Smooth flow means fully attached air which is important for accelerating the air under the wing. The faster the air under the wing is the lower the pressure, and thus the greater the downforce is generated. 

Onto the numbers. We ran this test on our 1600mm wing (no gurney) @ 80mph and various AOAs with both styles. Here are the results:

Standard Bottom mount: 
117lbs - 5AOA
128lbs - 7AOA
135lbs - 9AOA
135lbs - 11AOA
141lbs - 13AOA
Swan Neck mount: 
135lbs - 5AOA
151lbs - 7AOA
154lbs - 9AOA
151lbs - 11AOA
155lbs - 13AOA

On average we see about an 18lbs increase in downforce! This is about an increase of 12-13% in downforce performance. As for drag, the swan neck saw about 1-2lbs less drag or relatively similar numbers throughout this range. So for 0 increase in drag (actually a slight decrease) you get a decent bump in downforce. We also expect that the wing will perform better with less loss of downforce during turns when the flow is at an angle and is further disturbed by traditional bottom mounts.

These are actual performance numbers of our anticipated 1600mm Swan Neck Carbon fiber wing coming real soon. With over 300lbs of downforce at 120mph, you can bet you'll notice this on track!

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