Lightyear MX5 NA/NB Fastback

[Magpie]

I'll take a carbon hardtop/doors for 60kg savings please. Great to chat today and I'm seriously thinking on what you said.

[lightyear]

Thanks so much for loan of vented bonnet. Other changes may have contributed but no overheating. None. Zilch. Nada. Not a sausage. General engine bay temps lower after a session. Just need decent driver now.

I can also supply the driver...

[lightyear]

I'll take a carbon hardtop/doors for 60kg savings please. Great to chat today and I'm seriously thinking on what you said.

I am a big fan of less weight...

[davekmoore]

Thanks so much for loan of vented bonnet. Other changes may have contributed but no overheating. None. Zilch. Nada. Not a sausage. General engine bay temps lower after a session. Just need decent driver now.

I can also supply the driver...

True. But point me to local driver training instead, why don't ya?

[Dan]

I've been looking at getting an APR wing for my car and happened to find this when I was looking for information. Thought this might be interesting to people wondering about what the fuss about a fastback is.

Obviously with the examples they gave that Porsche has a different body, a better designed nose and a wing but it's interesting how much they are talking up the advantage of a fastback and some cool information about wing height and AOA on fastback vs 'sedan' designs.

Here's the link http://aprperformance.com/racing-produc ... ble-wings/ (it's in the "CFD DATA & ANALYSIS FOR THE GTC-300 ADJUSTABLE WING" drop down)

CONNECTING THE DATA TO REAL-WORLD APPLICATION
What we want to do now is to try to apply a bit of the CFD data and analysis to the real-world application of using this airfoil on a vehicle. First, we will first need to change a few things around. The first thing to change is the environment, because the mounted airfoil (both the center and outer sections) will never truly see any free-stream air flow. Even though the outer sections of the airfoil may be positioned beyond the vehicle's roof and body, and even though the air flow may be "cleaner" or be more parallel to the ground plane, the air around the sides of the vehicle is still affected such that it can no longer be considered to be free-stream air. Secondly, since we can no longer define angle with respect to the relative motion of free-stream air flow, it is helpful to introduce and use an additional term called "pitch." Previously, we had defined the AOA as the difference in angle between the center cross-section of the reference plane (a.k.a. "center reference line") and the vector that represents the relative motion of the undisturbed free-stream air flow. We will define pitch as the difference in angle between the center cross-section of the reference plane (a.k.a. "reference line") and a non-sloped ground plane that is parallel to the vehicle's direction of travel. A ruler that is placed on top of the center section of the GTC-series airfoil would be the real-life equivalent of the reference line. Additionally, to simplify the angle references and avoid confusion with AOA numbers, we will use only absolute values (i.e. positive numbers), in conjunction with either upward pitch (front higher than the rear) or downward pitch (front lower than the rear).

When the airfoil is mounted on the sedan-bodied vehicle, the center section actually be at an AOA that is greater than 0 degrees. This is because the air flow to the center section will have a tendency to follow the rear slope of the roof/glass/trunk area downward (see image below). This downward air flow will vary in smoothness (whether it's more laminar or more turbulent, more attached or more detached) depending on the shape of the vehicle (notice the air flow differences in the two vehicles shown below).


(Image from 3rd party source)


(Image from 3rd party source)

Knowing exactly what angles the air flows downward behind the roof and around the vehicle body is information that would be "nice-to-know," but in practice, we don't really need to know all the details. What we need to know is that the vehicle body has enormous effect on the air flow that reaches the airfoil. We should also know that the center section of the airfoil sees an effective AOA value greater than 0 degrees when the airfoil pitch is set to 0 degrees, and that the outer sections of the airfoil see outer-section-only AOA values around 15 +/- some value based on how the body affects the air flow. We already know from the CFD data that the outer sections of the airfoil begin to stall when the center AOA is around 10 to 12 degrees, with even greater stall at 12-13 degrees. Therefore, we can determine that the downward pitch of the airfoil should never need to be set beyond 12 to 13 degrees. In vehicles with steeper rear roof/glass/trunk slope, the airfoil pitch may never need to be set beyond 10-12 degrees. Remember, the inner or outer sections of the airfoil will begin to stall at effective AOA values of 25 to 27 degrees, with even greater stall at 27 to 28 degrees.

To re-iterate what was mentioned above, and to emphasize a few points:

1. At a center section pitch of 0 degrees, the effective AOAs of both the center and outer sections is greater than 0 degrees. --> The airfoil is already creating downforce at 0 degrees pitch.

2. At a center section upward pitch of greater than 0 degrees, the effective AOAs of both the center and outer sections will still be greater than 0 degrees up to a certain point. --> The airfoil is still creating downforce at "positive" pitch values.

3. A roof that slopes down to the trunk area gradually will allow the air to flow more smoothly (i.e. stay attached longer, be more laminar, less turbulent, etc.) than a roof that slopes down abruptly to the trunk area. --> Be very aware of how significant is the effect that the vehicle body shape has on the air flow to the airfoil when trying to determine airfoil placement and airfoil pitch.

AIRFOIL SETUP
Setting the Airfoil Height:As a general guideline, vehicles with steeper-sloped rear roof/glass/trunk areas are better suited to use higher airfoil mounting heights (just below the roof line). Vehicles with gradually-sloped rear sections (i.e. fastbacks) can work well with lower airfoil mounting heights. There is no strict rule for this, since every vehicle application is different. The GTC-300 airfoil comes with pedestals of a recommended height for each intended vehicle application. Additional height can be achieved by using optional risers.

Setting the Angle: It is helpful to know how the vehicle handles prior to installation of the airfoil. For the initial testing with the airfoil installed, we recommend setting the airfoil pitch to 0 degrees using an angle indicator tool. Test the vehicle's front vs. rear cornering balance at speeds above 45-55mph (on a familiar track surface). If the vehicle tends to understeer (feel "tight") too much at medium-high speeds, then dial in a bit of upward pitch. If the vehicle tends to oversteer (feel "loose") at medium-high speeds, then dial in a bit of downward pitch. Try to make very small adjustments as needed between each road test, and try to focus on adjusting one thing at a time (i.e. don't change the airfoil pitch, tires pressures, and shock settings all at once).

[lightyear]

I noticed straight away that the wing works better with a fastback. On the red car the wing was mounted very low, it worked so well I had to drop the angle to negative 7-10* to be able to steer. Where as in a hardtop, you would need to mount it above the roofline to be as efficient. Guys that have a wing with a roll cage, and no roof are definitely not getting the most from there wing.

[lightyear]

More process on the boot frame.


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[guss_bruss]

If you keep it so that the boot is still usable and it is weather proof you definitely have another buyer here! Are the plans for the boot mold to have a lip on it like the Autokonexion one does? if not are you keeping it the factory shape so an aftermarket lip (for example Carbon miata's huge lip) can be added as well?

Really love the time and effort you have put into this

[lightyear]

The boot will be as usable as the stock one. Just a little taller. There will be no boot lip. The rear edge will be OEM shape. That gives you the option to put any lip on to suit your taste, or leave it as is. I will be offering boot lips too. I want to make a cam style boot lip for the track users.
I am also looking at making the third brake light an LED strip in the back window. Instead of in the boot.

[mxred5]

Great job looks brilliant. you must have put in a hell of a lot of work, I will be watching with interest.

[track_addict]

Very excited to see the end result. Maybe one day I'll grab one.

One question. What are the issues regarding ADR's and the hardtop? Are there any rules that need adhering to or not? I actually wouldn't really care if I was to buy one, just a thought I had.

[guss_bruss]

I am also looking at making the third brake light an LED strip in the back window. Instead of in the boot.

This is a great idea and it is something I have thought of as well, something in the style of the Tesla Model S' 3rd brake light. but the only issue with this is for people who are going to be running wings you'd have to make sure the wing doesn't block the brake light from any angle, (for example a lifted 4x4 is going to see a different angle or height of your car from a corolla when behind you), maybe keep the stock brake light position in the mold so people have the option of running the OEM 3rd brake light, and then for the people who want to run your LED brake light they can cover it up with a boot lip if they want?

[lightyear]

The boot frame is all prepped, flanges made, and tooling gel coat on. Will have this done by tonight, then I can do the outside.


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[lightyear]

The boot section mould is done for the NB models.

Next is to mould the main roof section. Should have that done by Wednesday I hope.







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[Corey]

Awesome! Keep it up.