Developing an active rear wing on a hatchback

[indopleaser]

Been subscribed for a couple years now, one of my favorite newer subscriptions. Wish there were more channels like your

[damoyeet_bs]

Thank you so much! Love the video! Can never find info about wings of hatchbacks so I was pleasantly surprised when I found this.

[nemoismyson]

Excellent video, only thing is I wish you showed the preasure differentials when the wing was in its low downforce +8 configuration. Looking forward to buying the book before I start my next project

[jasonrivers]

I once used a fixed aerofoil, to counteract the inherent tendency of my Charger, to break traction, at around 80, if you booted it. The pedestals I used were 75mm tall, so I'm guessing were well and truly out of the attached flow, as it certainly cured the cars nefarious tendencies. The angle of approach that I used was rather steeper, at 26 degrees, but I can't say I ever experienced any flutter.
Its' tendency to break traction, at speeds below 80, I tamed with a set of trailing arms, and an XF Watts' linkage.
LC Torana rear springs allowed me to remove all but two, of the leaf-springs, as I considered the axle to be adequately braced, mate.
Excellent video, and I like the way you quote sources for parts.
Just realised that I mentioned this in an earlier comment, as I ultimately cut the wing up, and fitted two sections of it under the car, which was only marginally less effective, but was actually quite noticeable, when I tested the car without it.
The leading edge would have been 100mm from the floorpan, and the trailing edge was about the same distance, due to the kick-up, where the stock fuel tank had been.
Just wish that I had known about diffusers, back then.

[blainerawdon]

You are creating an excellent series of videos. Your approach is both rational and methodical. Thank you for your hard work and for sharing. A comment pertaining to the flutter experienced by your wife described at 18:00: This effect may be exacerbated by a couple design decisions that are easily addressed. 1) You are actuating the wing in the center of its span but supporting it at its tips. This provides the potential for wing deflection in the middle to result in a change in incidence angle. 2) You are actuating the wing behind the pivot axis. A downward deflection of the wing center results in an increased leading edge down (LED) incidence and, at speed, increased downforce and downward wing flexure. This feeds back into the actuation to further increase downforce and flexure. When the wing reaches its dynamic limit it may spring back and the cycle may repeat in the opposite direction. The result may be flutter. I can see at least four possible methods to address this behavior. 1) Actuate the wing pitch using a horn projecting ahead of the wing leading edge. This will reverse the process above, resulting in stable behavior: Downward deflection results in upward pitch, quickly cancelling the oscillation as opposed to exacerbating it. 2) Move the actuation point on the wing much closer to the trailing edge and using increased actuator deflection. This will reduce the unfavorable coupling between wing deflection and wing incidence. This may raise the speed at which the wing flutters. 3) Leave the actuator as-is, but install a gooseneck with a mass balance well ahead of the wing leading edge at the span center. This may tend to damp the oscillations by inertia and may raise the flutter speed. 4) Move the actuator to the side and actuate the wing near to one support. This may reduce or eliminate the coupling between wing deflection and wing incidence, increasing flutter speed. My favorite is the first method. Alternatively, Method 4 combined with Method 3 may also produce solid behavior. A parenthetical remark: This behavior may be most pronounced with the wing at low incidence because the variation in lift percentage per degree is much greater at low incidence. I hope these comments are helpful and/or interesting!

[draguroyalty]

Well explained, straight to the point, no maybes, no it might, 👍

[nikolaisarnytsky]

Currently builing a similar system for my Toyota using a dual element setup where the top setup opens and closes using a DC motor rather than a linear actuator but what a useful video, will make sure to watch more.

[weslleynereu]

Amazing information as always! I wish we could see practical track measurements on before and after mods! (Like maybe a circuit timing, a top speed, tires temperature during a corner (maybe to measure increased pushing force of tire on the road), etc)

[ihgcdtl]

Wish I’d known about this when I tracked an old saab 900 that loved lift off oversteer!

[narancs]

I always like to see your clever and inexpensive testing methods. You give lots of great ideas. E.g. the downforce meassuring with the open tailgate and the spring.
How would a simple Gurney-flap on the factory spoiler fair vs the added active wing on this car in your opinion?

[nthku]

Excellent; thanks. I was thinking, attach to speed sensor voltage and calibrate to full wing when speed achieved. Also, full on brake switch.

[Dzer]

GOE Göttingen…remember these from reading Model Aircraft Aerodynamics as opposed to paying attention in physical science class !

[qwerty]

For refference what thickness of aluminium you using for mountings?

[SDKRacingOfficial]

Does the Vehicle Aerodynamics book encompass other titles you've published in the past? As in is there a '"must have" list for track aero modifications and info. getting really stuck in on a build and want to take a more granular approach to the aero than most tend to

[mattdirks]

Any tips for looking for finding/evaluating NACA profile wings? (or is that covered in the book?)
Thanks!

[Daniel-hyxp]

Question. Im thinking about a big wing for my 2 door coupe cuz i love the look. And im wondering does a wing actualy increase drag on a coupe? Lets say its adjustable and i can change at how it sits tilted forward, backwards or perfectly horizontal. Wats the best position for it to not get any drag? Any mods i can add to help the wing reduce drag or anything like that? Like vortex generators or a lip on the top of the rear window

[theshed]

Just bought your book Julian. Looking forward to receiving it. Now, ignoring aesthetics, would moving the wing further backwards have reduced its influence on the drag behind the vehicle? Regards Greg

[stigastondogg]

We need to build you a wind tunnel my friend!!!!

[PatrickAndrewsMacphee]

Interesting, thanks. Generally we want large downforce and low (aero) drag. How do you deal with the extra rolling resistance caused by increased downforce? Is this simply insignificant?

[BrodeyDoverosx]

Check the anniversary edition of the Abarth. It’ll change from a spoiler for wake reduction to a spoiler that disrupts flow (for downforce), increasing drag. I experimented with a cheap spoiler extension and wow. Great downforce at the track, but terrible on fuel mileage.