Wings on a Hatchback

[@aidangarcia7421]

One of my friends used to drive a Mazda 323 GTX in high school. We used to joke about how its two "spoilers" generated infinite down force, and would allow it to fly if you managed to flip it. All joking aside, it's so cool to see the actual engineering and CFD behind that design choice. Nice work!

[@Nordlicht05]

Yes cars had it before but for Japanese brands they got away with everything. But I thought there is nothing more stupid than hatchbacks and spoilers. Than Mercedes put one onto the roof of an amg a class. Still stupid 😂

[@H-Shop]

​@@Nordlicht05A spoiler on a hatchback is stupid on road cars only. They have their place on a hatchback and can look pretty at times so long they fit the entire package, something that won't happen on a road car.

[@Nordlicht05]

@@H-Shop yep IAM talking about road cars. I personally don't know hatchback racecars with spoilers. Yes there may be some.

[@H-Shop]

@@Nordlicht05 WRC or rally cars have rather elaborated spoilers they end-up looking works of art. I'll never understand a spoiler on a hatchback, rather reduce drag and make my econobox more efficient than try to track it.

[@seymoarsalvage]

​@H-Shop I like the looks. THATS its purpose. Like a paint color... its for looks.

[@DeadRedRider]

Once again: Place your rear wing to help your floor generate more downforce. Don't use the rear wing for downforce. Use it to help your floor generate even more. In other words, think of the car floor and rear wing as a two element airfoil. Car Floor is the larger first element. Rear Wing is the second element. Use the Second Element Rear Wing to keep flow attached while also adding energy to help evacuate more air from the low pressure side of the Floor to generate more downforce. This might mean you're not placing the wing high up, nearly above the roofline, as expected. The angle to the ground plane might even be negative. Though it's AoA to the airstream will most likely be just slightly positive. All to accelerate the air to help the Floor evacuate more creating lower pressure. Which would create even more downforce than just using the floor and rear wing as seperate devices.

[@narendarsv1773]

Are you saying that by using the wing's downforce, reduce the volume under the car which means the flow will be accelerated and hence increased overall downforce?

[@bjorkay.]

can you create this effect in a e36 coupe for example?

[@DeadRedRider]

@@bjorkay. You could do it on any car. It's really a process of thinking of the car aero bits as a whole package rather than just bits and bobs you stick on. Shape the floor and diffuser more like an airfoil and not "Flat Floor then 12 degree Angled Diffuser". It needs to flow. Smooth. THEN the rear wing can better be used to add energy to the air stream to help evacuate even more air from your fancy floor/diffuser. It'd be even easier on a coupe rather than a hatch, 'cause the rear deck is lower and closer to the diffusers exit.

[@HandicapRacer]

But you still physically need to create downforce with the wing first for it to push down on anything smart guy and this video is showing that a wing and flap setup does almost nothing for downforce 😂

[@FunBitesTV]

Youre still thinking of it in the opposite way @@HandicapRacer . Imagine a wing that actually created a little lift at the rear, creating a "lever" and slightly increasing the rake of the car (a force actually lifting, infact think of it more as twisting/levering) the rear with a little upwards force but with the effect of also pushing down the front a little ) That lever force could then be used to alter the flow of the air around the rest of the car itself, but with the main goal of creating Lower pressure under the car for example, essentially sucking the car to the ground more. This would ofcourse require consideration of the rest of the aero etc of the car. On a basic off the shelf road car hatchback its probably not going to do much. But something with carefully designed aero on the underside, acting as a package with the rear wing. theres gains there for sure.

[@nickt5546]

I’ve owned a Mk2 golf 2 door for over a decade. I love this video. The fact that people (actual engineers) are still talking about and improving the Mk2 GTI makes me happy.

[@I.no.ah.guy57]

I've been wondering for a while now, how a sunroof being all the way open or just popped up, affects the aerodynamics. I was hoping you'd already have a video on it but if anyone would do it, I think you would be the best one for the job. It would be awesome to see you make this happen! Thanks

[@NathanTrukise]

Not about the aerodynamic but I tested the fuel consumption difference between closed and all the way open sunroof. The car consumption is ~1L per 100km higher with the sunroof open. About the same that having the AC on. Last summer I was wondering which of the two was more fuel efficient. Would be really cool to see how it affects the aerodynamic though.

[@I.no.ah.guy57]

​​@@NathanTrukise oh nice, thanks for letting me know. I really hope @nelsonphillips does a video on it though so we can see all the data. I'm sure it's generally worse than just having the sunroof closed, but I'm more interested in how much, and if/how popping it up instead of opening it all the way affects the flow towards the tail of the car

[@NathanTrukise]

Yes, I would totally like to see that too!@@I.no.ah.guy57

[@epjetta]

As an scca racer who drives mk1VWs I'm very happy to have found your channel.

[@Jacksonjj9739]

Can you do a lorry aero test so i can know how deep I have to tailgate it for me to maximize my fuel efficiency?

[@gen2mediainc.577]

it’s ok you can always brake more quickly than a semi

[@gtjack9]

@@gen2mediainc.577unless it hits a barrier and stops nearly instantly

[@pictsidhe6471]

Zero inches. I suggest plenty of coffee.

[@Biffsteki]

Nice, even though as you state its a robust concept, i think a lot can be done on the flap design aiding in the turbulent flow direction where the flow detaches, i think that is key to optimizing the wing performance.

[@nelsonphillips]

I don't think the turbulent pocket is such a bad influence on performance. The pocket is just sitting there rotating with laminar flow covering it. If the losses in that pocket burst out into the free stream that the wing uses, then that would be a concern. I would agree that there is a large amount of room for optimisation.

[@Biffsteki]

@@nelsonphillips yes i agree about the turbulent pocket, i was more talking about optimizing position and angle of the flap to make the free stream take a more upwards direction also trying to make the flow detatchment as clean as possible, depending on wing position above that, i think you could gain significant downforce without stalling it. Some modern rally and rallycross cars (hatchbacks) have extremely cranked wings and also flaps underneath.

[@someweeb3650]

IMO the purpose of the flap is to more ensure that the vortex behind the car is flowing upwards behind the wing. You can see that the angle of the hatch is in a kind of deadzone- not angled enough to be a fastback, too angled to have clean flow separation. The final design of the flap extends it far enough out that the air coming up is fairly laminar, IMO the way to improve it is to have enough mass flow from the underbody to just push that vortex higher, give it an easier time clearing the vertical section of the hatch.

[@Biffsteki]

@@someweeb3650 well, i dont think that increasing mass airflow underneath the car would do much difference for the roofline vortex, most of the air comes in from the sides of the car. Ofc, like always, you want a nice big diffusor, but most times when you have a diffusor and a flat floor you want to lower the car to increase the effectivness of said floor and increase the dynamic preassure, leading to lower overall airflow. And talking about huge diffusers on a hatchback shape car is also not eazy in practice. The video also looks at wings on hatcbacks within a certain rule set. And i think he did a good job within that. But in other cases you could achieve great DF with i higher placement wing and a good "flap design". And in regards to your answer, there are alot of ways to make the boundary layer after the flap more laminar. You could incorporate big strakes underneath it to improve more laminar flow, you could also look at winglet on the sides of the sloped rear quarter to bring in laminar energized flow along the trailing edge or even corntrolled vortices of the flap creating a stronger boundairy layer making it possible to crank the wing harder.

[@seljd]

the funniest use of wings was on Renault Espace mk3 (1996-2002) and mk4 (2002-2015) and some Peugeot 807 models also had them. Would be interesting to see simulation on those boxy family cars

[@xXThegabeXx]

I believe its just a roof rail joined together in aero position, pretending to be a spoiler

[@Critical_Stinking]

Mate, your vocal fry is on a californian girl's level.

[@standurham2525]

Info is ok, narration sleep-inducing.

[@cebruthius]

Yeah I was imagining myself watching a Samara videotape

[@NoNameAvailable23]

Would you rather he mix in some explosions and naked women to hold your attention? Let the Aussie nerds be Aussie nerds.

[@gtjack9]

If you’re like me and have never heard of vocal fry, here’s urban dictionary’s definition; “The artificial, gravelly, voice-lowering way to speak that makes you sound like a ditz. The opposite of upspeak, but having the same negative effect on others.”

[@ricardolarios2518]

I hear it like that on 2x

[@Cammi_Rosalie]

One thing I would like to know is if there is anything I can do or add to my van to stop road-spray or rain and just the general dirt and muck from being sucked up off of the road and attracted to the rear windows like a black hole attracts matter. Maybe some kind of wing or vanes to let clean air blow down over the glass from the roof. I don't care much about drag, since my van is an 8 ft. tall brick as it is. I have an older conversion van with the high roof, and 2 doors on the rear. (Just look up a pic of a '90 Dodge Ram B250 conversion van) I have installed a rear-view camera just behind the glass, and if it's raining, or the roads are wet, the crud just gets sucked up and all over the glass, obscuring any view or hope of seeing rearward via the camera or interior mirror. Anyone who has ever had a "flat-back" vehicle, as in a van, wagon, minivan, bus, RV etc, with no rear wiper/washers will know the struggle.

[@nelsonphillips]

The dirt is pulled up and behind the car from the ground, obviously. I have video that addresses the commercial attempts at solving a similar problem of snow by pulling air from holes in the spoiler. This solution is mixed. I would be inclined to divide the wake into two counter rotating masses with a flap under the rear window. There would likely need to be other pieces of body work to encourage the counter rotation, like a piece pulling air off the roof, but that is where I would start.

[@konholio2]

We have observed in practice that rear wing can and will increase rear wheel grip at high speeds. Also in context of pure downforce, it might not be much, but depending on where you place that wing you can shift the weight of the car and create a stable or predictable behavior in the high speed corners and at the same time very well rotating rear in the low speed corners. In general the closer to 90degrees the hatch is the more you get drag and less lift. And people rarely account the suspension dynamics when speaking about aerodynamics.

[@toonverbruggen7351]

With the configuration at 0:08, a positive aoa (so positive lift in free stream) should result in attached flow. Since the relative aoa that the wing sees is still negative, you make downforce and you could even get a bit of thrust because of the angle of the airflow. Now you are just stalling the wing big time, indicating a too high (or too negative) aoa.

[@nelsonphillips]

if you add thrust with the wing it is countered by the increase on induced drag on the body. The last wing/flap combination is a good example of this.

[@toonverbruggen7351]

@@nelsonphillips I still think it would be quite effective in terms of its dowforce production, test it out and see how it performs?

[@Biffsteki]

@@toonverbruggen7351 I see what you mean, but it would be even better to have flow separation higher by the roof line for raw DF. Efficiency how ever, i cant tell without testing ofc.

[@bertanderny]

Might just be my misunderstanding, but how is this not a benefit to on track performance? Also, will you be looking at wheel well extraction? I've seen two approaches to this - one being to completely divert the wheel wake outwards similar to a bargeboard like on the M4 GT3 and the other being to vent it out like the R8 GT3 which seems to be the more traditional way of doing it.

[@askalotofquestions]

If the wing extends off the sides of the hatch it just produces more drag because there is no roofline to guide the air

[@chikogota]

very good that you kept testing and learing, notice that you found out that it was from old rally cars, also hill climbs (pikes peak, some dakar and so on) but most of them use a different method instead of the flat flap following the roof, very glad you tested that one because thats my theory of putting the wing all the back you are allow and letting the air follow a better shape to decrease drag and lift on the body of the car ( having a so back wing also helps with making more leaver force to the chassis) some ideas that you can test on the rear back of the hatchbacks ( i have some already installed) using a flat flap, with gurney and other with spoiler but on the middle of the car below the wing, i believe that area can be used to get more effiency out of a hatchback form i saw the complete list of the touring aero you made and notice that you made a cut on the rear bumper, i am using one but from around the back axel 90 degrees diffuser ( same theory of a open door on the rear of a pickup) but upside down, racing with it at certain speed i have felt the interior that i made from sheet steel bending so i assume it works and create more pressure to the rear great content and hope that someday we can maybe chat about it, always it is a very good time talking on aero from race cars and dont feel that everyanswer has to be though because it is a business secret that sells thanks for the content and have a great day

[@qwasd0r]

This explains why the rear of my Focus is always the dirtiest the quickest.

[@FunBitesTV]

On an all out race car with full aero an ultimate way to benefit could be to create a wing that actually created a little lift at the rear. Creating a "lever" effect slightly increasing the rake of the car (a force actually lifting, infact lets think of it more as twisting/levering) the rear with a little upwards force but with the equal effect of also pushing down the front a little. That lever force could then be used to alter the flow of the air around the rest of the car itself, but the main goal of creating Lower pressure under the car for example, essentially sucking the car to the ground more. More net downforce. This would ofcourse require careful consideration and design of the rest of the aero etc of the car. On a basic off the shelf road car hatchback its probably not going to do much, infact youll end up with more net lift. But something with carefully designed aero on the underside, acting as a package utilising the rear wings rake boost, well, thats wheres the aerodynamic performance gains could be at for sure.

[@metalsage5135]

The only way I can think of to do that would be if the wing had a flap kind of like an elevator on a plane so it’ll have negative lift towards the front of the wing and upward reaction force in the rear. But I’d imagine that’d take tremendous force to make a difference given how little leverage the wing will have on the rest of the car, so it’d need a lot of surface area for the “elevator” which would create a lot of drag.

[@TheDarckstart]

at my work i learned one big thing about wing and flap and flap squarre, a wing without a flap isn't as effectif as a wing with a flap, and flap squarre is as important

[@RM-sz6dw]

Interesting thanks! Can you show us a Holden Commodore wagon? Stock and some thing after market?

[@craig855s]

Great channel, would it not be more beneficial to use devices at the back end of the roof to redirect air into the low pressure zone behind the car to just reduce drag. And maybe use a flat floor with splitter and diffuser to create some negative lift for the car? i'd love to see that visualised

[@askalotofquestions]

Rally cars have wings for an exorbitant amount of reasons

[@TheFiku]

what about the consept of clean seperation edges, I mean this car is kinda boxy so it comes kinda like that from factory, but if you have extended flaps from sides in a negative angle to give smaller wake area and better separation edge does this do anything

[@pacificamindustriesltd.9024]

Do you think the cheesegrater-style rear aero element from the first-gen Suzuki Alto Works, actually works? Brochures made a point over the reduced Cd it apparently did.

[@nelsonphillips]

observing suzuki from that time I would bet it did. I don't really know how........ Might be a good quick test

[@Alkatross]

What wing/flap would be best for a 2020 chrysler pacifica?

[@Pa8]

😂😂😂😂😂

[@arnau_rg2869]

I was interested of becoming an engineer and i'll keep looking at your channel to see if it's interesting to me. Thanks a lot!

[@Superbouncybubble]

I'm an engineer and know many engineers who basically do this kind of stuff as their jobs. If you like this kind of methodical, mathematical/simulation based approach to solving problems then I think you'd make a good engineer :)

[@K03sport]

so Wings West's mid hatch wing for the GTI was correct all this time? I just thought it was part of their tacky, bloated looking body kit to go along with 90s/early 2000s car styling. what about a small lip spoiler on top of the windshield and then a slightly larger moon shield lip spoiler __/ on top of the hatch glass? the idea is to slow the air going over the car, yes; or is it to make the air tumble?

[@vortbrodet]

What about a spoiler, and a roof spoiler, on a sedan? Would a slim roof spoiler reduce drag?

[@pequod1]

Can you explore in more detail the effect of a 'midwing' on hatch aero?

[@nelsonphillips]

you mean like from a escort or sierra?

[@DarkVarda]

@@nelsonphillips there where aftermarket midwings for the golf mk3 as well

[@mjrtensepian1727]

Yeah, I instantly thought of cars like the Saab 900 SPG or the Merkur Xr4ti when he got to the middle/secondary spoilers

[@misfit4816]

@@nelsonphillipsImpreza GF8 had one as well

[@hectorae86]

I'm more interested in keeping the rear hatch clean... Especially the window

[@TheSupercarKiller]

So the VW TCR race car wing that comes on the car from the factory could be considered as useless?

[@badly_dubbed2401]

My Corrado has an active rear spoiler. Comes up at 70mph.

[@stefanjohansson6670]

It would be interesting to see the turbulence on an old Saab V4 95. It has a built in spoiler.

[@mikeb3172]

Just a horizontal extension out to the max distance allowed would stop lift from the rear window...

[@nelsonphillips]

Other videos of mine says that the spoiler on every hatchback sold now reduces drag by 10%. Most of that drag is also producing lift.

[@Nielutz]

What about a 95 civic eg hatch with a "spoon" type spoiler?

[@zweispurmopped]

From model aircraft and glider design, I know the Wortmann FX60-126 airfoil to offer a high Cl and L/D over a wide range of Reynolds numbers. For a laminar flow airfoil, its tolerance for turbulence is remarkably good as well. I know its characteristics from the ASK 21 gliders from first hand experience and can confirm that the last bit of these planes to stop flying are the wing tips which feature the FX60-126. Maybe run a simulation with this? An airfoil that produces a substantial Cl max from low Reynolds numbers as well is the RAF 32, which is not too popular with planes for its Cm₂₅ being pretty hefty. For use on a car, this would be very little of an issue, so it might be a good choice there!

[@messvideos1]

ok, I took a screenshot of the config at 0:30 because I was really curious about how strongly the air is pulled down. The angle of the tailgate to roof transition is dead close to 30 degrees. That is the angle with the most induced drag for a hatchback rear end based on Ahmed body experiments, so it does explain your findings, especially that the model doesn't have any trips at the transition. The effective angle of attack because of the downwash is ~40deg, so yeah, no chance that would stick. At 3:45 it's ~25-30deg so again, separates. The second part of the rules you posted does appear to ban the plate, as it is a spoiler, but I'd be asking for a clarification. I.E the Civic running in improved production now has the integrated tailgate trip & a rear wing. On a separete note, would you be open to sharing a picture with the mesh shown? The model looks pretty smooth, but the vector arrows look pretty sparse and that could have an impact on some results.

[@nelsonphillips]

The air is marginal on separation, the is bucket load of induced drag without the trip. A standard spoiler seen on every hatchback or wagon reduces drag by about 10%. The trailer in the video previously it was about 12%. That rule set is just a way to anchor the video. I have done some work for an improved production competitor and they were responsible for the hatchback rule for spoilers.... A mesh for this car is about 25mil AMR. The vector glyph is 1:100 cells if I remember correctly. You wouldn't be able to see anything if it was for every cell.

[@briancavanagh7048]

Looking at the section with the flap and wing combination is this ignoring the side edges of the hatch? Can air be brought in from the sides to modify the circular airflow over the rear window?

[@Biffsteki]

i think this would be super effective. also runing vortices with airflow from the sides along the flap to aid flow separation to strengthen it could allow you to use more aoa without stalling.

[@idntfkngcare]

What anout civic eg spoon spoiler?

[@АристофанМитяев]

Надо не увеличивать прижимную силу установкой антикрыла и увеличивая аэродинамическое сопротивление, а уменьшать подъемную на задней оси, установкой спойлера и уменьшением аэродинамического спортивления, с целью уменьшения зоны разряжения позади автомобиля. Чтобы понимать о чем я говорю ознакомьтесь с ауди ТТ первого поколения

[@nelsonphillips]

other videos, three in fact, trailer, golf and the suzuki, cover this exact topic.

[@lucasandri5462]

Very interesting video, in currently studying aerodinamics at university and seing it applied is very interesting and helps visualise it. To reduce the overall drag of the car are you allowed to make a diffuser for the underfloor? That should help reduce the base area on the rear and so the overall drag. If I said something wrong please correct me because I'm still learning so I appreciate any advice.

[@Barry.ONeill]

So whats the conclusion form your data ? Rear wings work if you use the standard flat spoiler too. Im always looking a wrc and rally 2 cars rear spoilers

[@rich7447]

Barry O'Neill from Limerick?

[@therealracer135]

You should do a video on ute/'pickup truck' aerodynamics

[@Mucdaba]

hello, what program do you use for the flow simulation?

[@424io]

Make the chassis of the car the shape of a functional downforce aerofoil

[@luizhj]

Can you do the same analysis on a wagon?

[@hillppari]

Only thing the rear spoiler did in my hatchback was to get dirt and dust stuck between them and annoying to clean

[@willyjimmy8881]

How much more effective would a wing be vs just a surface mounted spoiler? Or flap as I think you call it. Seems like a wing adds more drag than anything useful.

[@K03sport]

I guess it depends on where you want to tumbled air vortex in relation to the rear of the car. this is where an under floor diffuser helps direct/channels air past the rear bumper to eliminate rear lift and a long roof spoiler pushes the air vortex further away from the glass/hatch. One is not much good w/o the other

[@GeneralKato]

Once I saw the underside of my car and realised how not aerodynamic is seemed. Ever since I would like to make it more aerodynamic.

[@nelsonphillips]

a rough floor on a car is mostly drag. A rough floor can, surprisingly produce decent downforce.

[@GeneralKato]

@@nelsonphillips i never suspected that. Whenever I reach certain speeds about 100mp/h and up) I always notice a bit of lift. Not much and it can vary (i guess it’s wind direction). I always wondered if I could counter that. Thanks for replying.

[@CrAzYDr1veR]

hi, any chances of a episode on drag racing hatchback? :)

[@nelsonphillips]

specifically drag racing, no. Though, these are concept heavy videos, so I can't see why they can't be applied to drag racing.

[@etcot8220]

On the road they are not really useful especially if you follow the speed limit. Drag racing, not useful at all. Rally or race, definitely helpful and useful due to the sheer amount of variables involved in racing. Wind, high speed stability, stability overall, couple with the slaps (floor sidewing) makes a huge impact on reducing drag where you model completely ignored this aspect. That’s where the suspension starts to matter, how stiff or responsive can impact the drag differently. There is soo many things I could go for an evening.

[@nelsonphillips]

you should watch my other videos for all the other variables

[@2smokes]

what program is this ?

[@temporalmadness3756]

Hi, Nelson, could you possibly reccomend a CFD software? i tried following open foam tutorials but could not manage to geit ti running

[@nelsonphillips]

i can only recommend openfoam .... 🤷

[@temporalmadness3756]

@@nelsonphillips I'll give it another try then.. Could you reccomend any tutorials on installing it and running a simulation similar to yours?

[@Mephistopholies]

Good stuff! Would you call the tiny squishy lip on the back of a first gen CRX Si a type of spoiler?

[@nelsonphillips]

yes. those are a nice car

[@Alan_Hans__]

What may be a silly suggestion. What happens if you mount the wings vertically behind the car. Obviously there will be rules not allowing it but just wondering if they can be made to reduce the drag. At a super loose interpretation the vertical wings could be called the end plates.

[@Dragonzdx]

How do you do this simulations of air ?

[@nelsonphillips]

openfoam

[@Dragonzdx]

@@nelsonphillips Thanks

[@Alex-gj9bg]

what’s the software ?

[@ThisIsHowGoodSports]

We own a tucson 2005, will there be a good result if fitted with a wing?

[@ChaufMT]

A sissy little wing on a streetcar has no or not much use. At speeds achieved on streets, it generates not enough to have effect. If so the wings on sportscaster would be smaller .

[@real-NFSS]

I’m sorry but why are you talking so slow dawg

[@DavidTrejo]

High drag coefficient (probably)

[@real-NFSS]

@@DavidTrejo bruh shut up 🤣🤣🤣

[@materialdefender3599]

Because he's not on cocain and is a normal person.

[@ELJ666]

Wing looks too far back why not move it closer or right on top of the roof