Well, like Mach 1 Pony, above, I am no aerospace, or even aeronautical, engineer. But having built and flown a lot of high speed model airplanes as a kid I did learn a lot about the effect of air flowing over an air foil (wing). So, why is that important? The particular device as shown in the OP photo is not a spoiler, which is meant to disrupt airflow and alter the way said disruption acts on an object - as in applying downforce on the rear or front of a vehicle in the case of automobiles. The air foil is
usually designed to apply up force under the wing by reducing air pressure above the curved surface of an air foil. But, when mounted on the rear of a vehicle the wing is turned upside down so the higher air pressure normally beneath the foil (wing) is used to apply downforce on the rear of the vehicle. But, it does not disrupt the flow of air like a spoiler does, it merely alters the flow of air in a smooth manner while gaining the intended up force (or down force for a car).
The amount of "angle" from 0 degrees (horizontal) from the leading edge to the trailing edge is called the Angle Of Attack (AOA). You can gain additional downforce by pointing the leading edge in a downward position, but that impact can become disruptive and add drag on the wing and the car attached to it. And, with excessive Angle Of Attack in either a positive or negative angle direction will adversely impact the ability of the foil/wing to generate the desired up force (airplane) or down force (car), hence why a plane that has been pointed nose-up too far, hence increasing the wing's Angle Of Attack," will stall due to loss of the wing's up force, leading to the plane falling toward the ground. In order for the wing to gain its desired up (or down) force, the wing needs to have air flowing over it at a minimum speed, with certain Angle Of Attack, and in correct direction. As if that is not enough to consider, a wing with a higher Angle Of Attack will create additional drag on the wing, which slows a car down also, even if through its spoiling action it might, to some degree, increase downforce. The idea is to use a wing at the best location, and best angled and surface area to produce needed down force with a minimum amount of drag, where the drag impeding a vehicle's speed is offset by the improved handling of the vehicle due to the downforce "at speed." It is a balancing game, where one looks for the right mix of impact to get the best result. That is too much for me to consider, especially for a car traveling at street legal speeds - hence minimal tangible impact, so I boil it down to looking to achieve a certain "look," and let the imagination of the observer to run unbridled.
So, to the previous paragraph, I added something about the "correct direction." Yep, the air foil (wing) needs to be pointed in the correct direction relative to the flow of air over it to achieve its optimum degree of up/down force. For any air foil there is a leading edge, which is facing into the flow of air, and the trailing edge, which is pointed toward the rear of the air flowing over it. The general rule of thumb is the thicker edge of the foil faces into the flow of air. So, for these rear wings on the First Generation Mustangs, the way they are supposed to be oriented is "
Thick edge in front." Yep, the front and rear edges of those wings are different thicknesses, as they should be in order to "work." The thicker edge is the leading edge and is supposed to face the front of the car. Now, I know it does not look right when considering the way the left and right wing tips are swept. I admit, visually the orientation of the wing, based on how the tips are swept, is counter-intuitive. But, it is also correct based on the air foil's cross sectional design.
Knowing all that, much less understanding it, will lead to one thing for sure. Even when the rear wing is oriented correctly (assuming you are driving in a forward direction) will certainly lead to about half the folks seeing it telling you it is wrong, based on how the tips are swept and their visual interpretation of what "makes sense." And some of those folks will tell you how the leading edge should be pointed down. One can say in far fewer words than I just did, simply, "
These rear wings are not spoilers, they are upside down air foils. As such the thick edge faces front in order to generate the desired downforce. If it was a spoiler you would be correct." Enough said. Now then, there remains where the pedestals onto which the wing is mounted, ought to be positioned. Amazingly I get folks trying to tell me all kinds of things, even after I had just demonstrated a solid understanding of how an air foil works. So, I simply tell them, "
I mounted it where I felt it looks best, which also happens to be where it works optimally."
Funny thing about how airstreams work, when something looks "aerodynamic" visually, it often indeed turns out to be aerodynamic... Not always, but often that is the case. One notable exception is when looking at the Ford Pinto from the 70s and 1980, they were more aerodynamic in reverse than when facing forward!
Anyway, as for how effective those rear wings are, that depends on the speed of the airstream (speed of the car), and the Angle Of Attack. At 0 degrees Angle Of Attack (flat) the downward force at 80 MPH is only about 50 pounds. In real life that is not going to provide a noticeable improvement in handling performance at street legal speeds. In fact, the drag effect will provide an adverse impact on performance at increasing speeds. Everything is a balance of factors and impacts. For me, it comes down to achieving a certain "look of performance," as opposed to any practical advantages being achieved. I found the following link to have some great information, at least for those folks willing to read through and consider the information presented:
https://www.m3post.com/forums/showthread.php?t=1586800
Okay, time for some videos. In the first link you will see how our properly placed and position rear wing looks in the walk0around video. In the 2nd video I wanted to show how the mounting pedestals are supposed to be mounted. Now that I have posted all this I await to impending and expected criticisms... Bring it on! heh heh...
I do not have the actual dimensions in inches for where the wing mount pedestals are supposed to be located on the rear trunk lid. But, I am certain "someone" in this forum's group has that information. It seems to me those measurements came with our wing when it was ordered (it is not a factory mounted unit on our Mach 1). I added it during the restoration simply for "the look," as it is not adding significant downward force at street/highway legal speeds. I did not install the wing, it was installed as part of a deep restoration, where I also added the rear window louver slats - again for "the look" (although it has reduced the amount of sunlight heat that comes through the rear window by shading the glass. When driving at highway speeds the louver slats are pretty stable. But, at very high air speeds (as with a high volume, high speed blower drier at a touch free car wash), those louver slats begin to do quite a dance in the high wind speeds, and changing relative Angle Of Attack as the position of the wind from the blower changes. The dancing of the louver slats is not bad enough to cause them to depart from the car, but it is interesting to see. I am glad they do reduce sunlight heat coming into the car, despite us having air conditioning, as it does make for a cooler interior in Summer.
Wow, that was fun to write! And it got me to thinking about stuff I have not really needed to consider for quite a while.
