Wings/Spoilers: You're probably doing it wrong.

"It's a "Porch-uh"" (ikazuchi) 12/01/2014 at 16:40 • Filed to: Aero

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I like reading Quora because some really smart people can be answering the questions. Case in point: somebody asks about "spoilers" and how much force they produce, and Ryan Carlyle, a subsea hydraulics engineer, sets the record straight. The following is reposted with his permission and will hopefully educate more of you about how automotive aerodynamics work.

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To be blunt, most people putting body kits on consumer automobiles are scientifically-illiterate and have no idea what they're doing. The typical internet "collective wisdom" is shockingly stupid about this. While answering this question, I had serious trouble finding illustrations on Google image search that weren't wrong.

THIS IS WRONG:

Here's the crux of the issue: there is a HUGE difference between a "spoiler" and an "airfoil" or wing. They have different shapes and do different things.

An automotive airfoil is shaped like an upside-down airplane wing — it deflects airflow upward to generate down-force on the rear of the vehicle. This does NOT particularly improve aerodynamics. In fact, an aggressive airfoil adds a substantial amount of drag, in exchange for more traction at high speeds. You see these on Formula 1 racecars, where unbanked racetracks make grip on corners critical to success:

Lots of airfoils working together in the rear wing:

Typical F1 down-force distribution:

Let me repeat it so it's clear: airfoils add drag, reducing your top speed and top-end acceleration. But at high speeds, they push the car down and add traction so you can turn faster. This is a trade-off.

Redbull gives you WINGS, not spoilers:

AIRFOILS ARE NOT SPOILERS AND SPOILERS ARE NOT AIRFOILS. Ok? Don't confuse the two, or you will look dumb on the internet.

So what the heck is a spoiler? It's an obstruction to localized airflow that improves the overall airflow around a vehicle. Basically you're adding a barrier to a region of undesirable air behavior so the air will flow somewhere else.

The worst airflow a car sees is at its rear edge, where the shape of the vehicle pulls air downward (causing dangerous lift) and generates turbulent, low-pressure air pockets behind the vehicle (contributing to drag). Spoilers change that airflow.

When you look at NASCAR spoilers, you don't see a wing or a graceful ramp, you see a frickin' air-blocking wall at the tail of the car:

This air-blocking flap creates a relatively stagnant pocket of air (shown in green) between the rear window and spoiler:

This is where people's intuitive grasp of aerodynamics is wrong. Most folks think airflow exactly follows the surface contour. Even many auto-designers used to think that, until computational fluid dynamics and rigorous smoke-trace wind tunnel testing improved our understanding of airstream behavior. This is why so many older vehicles had idiotically-ineffective spoilers or wings. Like this dumb beauty:

The !!!error: Indecipherable SUB-paragraph formatting!!! —because cars that look like rocket ships are awesome.

But in reality, fast-moving air doesn't like to enter blind pockets. Why should high-speed air follow an elaborate contour when it doesn't have to? The main airstream over a vehicle will flow around the obstruction without entering the blind pocket. Meaning the bulk of the airflow doesn't hit the spoiler so much as avoid it. Path of least resistance.

By preventing airflow from entering a region with an unfavorable body shape, the flow streams around the entire vehicle can be improved. Laminar airflow will avoid the obstruction, modifying the effective body shape, so a properly-designed spoiler can improve the drag coefficient of the vehicle even though it looks like a wall. That reduces drag and improves efficiency.

Naturally, this only works well if you do it right . As in, perform some CFD analysis and then prove up the design in a wind tunnel. Internet companies selling ridiculous body kits to "ricers" generally aren't doing a lot of that stuff.

Just to make it extra clear what I'm saying here: spoilers that stick up above the roof of the car are blisteringly stupid. They make the car's slipstream significantly larger and add a ton of drag. Don't be the guy with the idiotically-large spoiler. No good comes from that.

Here's more CFD, comparing a NASCAR spoiler (top) to a NASCAR wing (bottom). These were both designed by competent people. Blue is turbulence. You can see how the red laminar airstream avoids the spoiler, but hugs the wing:

Wings are designed to interact with a lot of air. Whereas spoilers are all about redirecting airflow away from the region where the spoiler sits. The bulk airflow isn't even supposed to hit them.

More CFD, showing the stagnant pocket (dark blue) in front of a spoiler (rear car) vs a wing (front car):

Of course, CFD is only moderately reliable. (Fluid dynamics are hard.) The proof is in the pudding. Here's a wind tunnel smoke trace over a well-designed spoiler on a Porsche:

You can see how the airflow is cleanly redirected from a downward direction (which generates undesirable lift) to a horizontal direction (no lift). Very little airflow goes under the spoiler. It doesn't need to be shaped like a wing or deflect a lot of air. It just creates a little bit of a stagnant air pocket to deflect the main bulk of airflow.

Now compare to a typical sedan tail end:

See how the airflow expands and flows downwards as it exits the rear of the vehicle? This is producing lift as well as some extra drag. (The smoke expands as it slows down.) The faster the car goes, the more the rear end will try to lift off the ground. A good spoiler (or wing) reduces that up-lift.

To summarize:

Both wings and spoilers reduce up-lift at the tail of the vehicle, but use different mechanisms.

Wings are airfoils designed to directly deflect air upwards and thus push the rear of the vehicle down. They generally add quite a bit of drag.

Spoilers are barricades to undesirable flows, and thus are able to reshape airflow streams around the vehicle. This can help keep the rear of the vehicle down and decrease drag by changing the effective vehicle shape.

You need computational fluid dynamics and/or wind tunnel testing to quantify spoiler/wing performance.

Neither have any positive impact whatsoever on straight-line low-speed acceleration. Both are primarily intended to improve stability and cornering at high speeds.

Got it? Good. I'm tired of the internet being so consistently wrong about this.

All images via Google Image Search.

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Reposted by permission from !!!error: Indecipherable SUB-paragraph formatting!!! .
Original post can be !!!error: Indecipherable SUB-paragraph formatting!!! .

thebigbossyboss > It's a "Porch-uh" 12/01/2014 at 16:46

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Thanks for this. I just want a wing for my car (nascar style) because it looks cool tbh.

Slow down for what?

Saoul-Virage > It's a "Porch-uh" 12/01/2014 at 16:49

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Wait a minute.... so this is not the right way to do it ?!

Brian and Roman, F*** you !

505Turbeaux > It's a "Porch-uh" 12/01/2014 at 16:50

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even though not written by you, super awesome write up and solid link back, so I am sharing to oppositeblog anyways. Thanks

Arch Duke Maxyenko, Shit Talk Extraordinaire > It's a "Porch-uh" 12/01/2014 at 16:52

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But these were 100% functional on the NASCAR racers.

RamblinRover Luxury-Yacht > It's a "Porch-uh" 12/01/2014 at 16:52

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Only one quibble I have, and that's that the Superbird's spoiler was anything but "idiotically ineffective". It was placed that high, increasing effective cross-section (but picking up a lot of available air) on purpose and with some rudimentary computer modeling. It's horrible from a drag basis, but *no fucks were given* expressly because they wanted downforce over everything (and enough room to open the trunk). In case you are inclined to wonder why that Mopar platform might need a lot of downforce, to the point that they'd sacrifice good aero overall for it, look up what they had to do to get the General Lees on DoH to fly straight over jumps.

Also, the extra drag is far enough back that it makes for a very yaw-resistant car at high speeds, a drag center well behind the effective center of thrust and center of mass. This is exactly the reason some of the early Mercedes aero cars had tail fins... before it was cool.

We wouldn't design the spoiler that way today, but there were solid reasons for it at the time, not even ones grounded in misunderstanding.

MarquetteLa > It's a "Porch-uh" 12/01/2014 at 16:55

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"The rear wing was mounted on tall vertical struts that put it into less disturbed air thus increasing the efficiency of the downdraft that it placed upon the car's rear axle. For nearly 30 years the mathematic formula used to determine the exact height of the enormous wing was thought to be a highly guarded Chrysler secret. However, in the 1990s a retired Chrysler project engineer admitted publicly that the height was determined in much simpler fashion: it was designed to provide clearance for the trunklid to open freely." http://en.wikipedia.org/wiki/Plymouth_…

CRider > RamblinRover Luxury-Yacht 12/01/2014 at 16:58

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accidental reply

CRider > It's a "Porch-uh" 12/01/2014 at 17:00

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Anybody that wants to insult the Superbird's awesome wing can fuck right off.

It's a "Porch-uh" > RamblinRover Luxury-Yacht 12/01/2014 at 17:00

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But where's the downforce on this wing? The horizontal section is basically flat and it "looks" like it provides more lift than anything.

I'm not in any way an expert in this, so I'm genuinely asking and not trying to start crap.

Arch Duke Maxyenko, Shit Talk Extraordinaire > It's a "Porch-uh" 12/01/2014 at 17:04

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They're quite wing shaped

RamblinRover Luxury-Yacht > It's a "Porch-uh" 12/01/2014 at 17:14

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It is, indeed, almost flat. It's just enough not-flat that it is capable of providing downforce at high speed. It's away from the car in a high volume of air - that means that if you accept the drag sacrifices in getting it away from the car, it's just a simple airfoil in almost flat-running air providing exactly as much downforce as it's tuned to. It's an aerodynamic dodge, pun intended - if you can't control the air near the car very well, put the airfoil somewhere away from the car. The less far you are from level, the more air it takes to produce downforce - but the foil itself stays effective at higher and higher speeds - it doesn't hit a Reynolds number that suddenly spills over into nothing but unmanaged drag. Nowadays, the design drag would be part of it, but they're taking a simpler approach and making a foil that would still be in smooth flow at 300+ mph.

I don't actually know the precise effective attack angle. The closing airflow behind the car means that the effective attack angle *will* be different from the nominal attack angle because the flow lines are still affected that high above the car - but trading off the turbulence and drag on the stanchions, you have a foil that is *not* in a low-pressure area like a lot of cosmetic wings, and is actually out in main airflow where it can work. It's crude, but effective - taking *proven* aircraft engineering and stapling just enough of an aircraft onto the Mopar to have an effect. They *were* pretty rigorously wind-tunnel tested - just because the main body of the car had flaws that meant making a silk purse out of a sow's ear doesn't mean they didn't have good results *given that*.

A modern car would stand to lose far more than it would gain with these shenanigans. The Charger/Roadrunner platform... not so much. It's not managing airflow holistically, like anything the author talks about, it's just adding a Finger of God of air to push the back down.

As Du Volant > It's a "Porch-uh" 12/01/2014 at 17:16

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Awesome article.

The way it was always explained to me was that a wing works like an upside down airplane wing, using the airflow to push down on the car the same way it pushes up on an airplane, and that a spoiler "spoils" the lift-inducing airflow around the back of the car.

Planes have spoilers too, they're used on landing to disrupt the airflow across the wing and reduce lift. They're the pieces sticking up in this photo:

Rainbow > It's a "Porch-uh" 12/01/2014 at 17:20

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And this is also why people are stupid to drive around like this:

Trucks are designed and tested with the tailgate UP. If it performed better down, don't you think they would have sold it that way?

Vintage1982Benz > It's a "Porch-uh" 12/01/2014 at 17:21

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Rainbow > As Du Volant 12/01/2014 at 17:22

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I always thought those were air brakes.

evil2win > It's a "Porch-uh" 12/01/2014 at 17:27

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Thanks for clearing all that up. Now here's a wind tunnel test of a Superbird and I have to say that wing doesn't look like it's doing much other than look cool as hell.

It's a "Porch-uh" > Rainbow 12/01/2014 at 18:10

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There was a Mythbusters that hit on this. After the tests there was a great visualization with a model in a water tank. You could see the "bubble" that was made with the gate up and the difference it made with it down. Basically the air drops down off the cab towards the back of the bed then swirls forward and up and out. With the gate down it comes off the cab and hits the bed instead of moving cleanly out.

Arch Duke Maxyenko, Shit Talk Extraordinaire > evil2win 12/01/2014 at 18:13

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That's not a Superbird, that's a later gen car made to look like a "what if? car"

orillion > Rainbow 12/01/2014 at 22:24

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There is some slowing due to air resistance, sure. But the primary function is to kill lift so more weight is on the wheels so the regular brakes are more effective.

Gary Yogurt > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 15:40

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I liked these way more after I found out they are aluminum. I also keep forgetting who I need to ask to be un-greyed. I can send you my CV, complete with various video game hi-scores.

The Rusty Hub > Rainbow 12/03/2014 at 15:42

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They can do that, too.

Mini_Fanatic > RamblinRover Luxury-Yacht 12/03/2014 at 15:43

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I thought it was mostly, in effect, a pair of rudders to keep the back-end from stepping out?

The Stig's graphic designer cousin > It's a "Porch-uh" 12/03/2014 at 15:43

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dat downforce.

Maxaxle > It's a "Porch-uh" 12/03/2014 at 15:44

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That poor Supra...

tromoly > It's a "Porch-uh" 12/03/2014 at 15:44

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Isn't the big reason for running a spoiler the high pressure area created on the decklid, effectively creating downforce?

drdude > It's a "Porch-uh" 12/03/2014 at 15:44

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actually... this just confirms I am doing it right.

BritBenzene > It's a "Porch-uh" 12/03/2014 at 15:45

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As someone who occasionally helps design high precision airflow booths, you had me at "laminar." Fluid dynamics is hard and this post is a good into to why there is a TV tray on the back of a this car or that car.

Oppo! > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 15:46

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"it deflects airflow upward to generate down-force"

No. I creates an area of low pressure below the wing pulling the wing downward and pressing the car into the ground as a result. This would make as much sense as saying airplane wings work by riding on top of the air like water skis. Not the case.

'70dime > RamblinRover Luxury-Yacht 12/03/2014 at 15:46

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I thought the wing was that high purely so the trunk could open all the way...

For Sweden > Rainbow 12/03/2014 at 15:46

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Nope.

Spoilers up > less lift > more weight on tires > better braking.

Maxaxle > It's a "Porch-uh" 12/03/2014 at 15:47

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Also, different front end.

Toyotathong! > RamblinRover Luxury-Yacht 12/03/2014 at 15:47

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Rudimentary computer modeling back then was done on this:

HammerheadFistpunch > It's a "Porch-uh" 12/03/2014 at 15:48

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" An automotive airfoil is shaped like an upside-down airplane wing — it deflects airflow upward to generate down-force on the rear of the vehicle."

I'm not digging on your explanation of wings. The downforce doesn't come from vectored air, it comes from differential pressure. I.e. faster moving air exerts less pressure than slower moving air and the difference in pressure generates a force in the direction of the lower pressure.

melikecars > It's a "Porch-uh" 12/03/2014 at 15:49

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So, did this do anything functional?

It's a "Porch-uh" > melikecars 12/03/2014 at 15:50

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Looking awesome = functional in my book.

Wild Weasel > RamblinRover Luxury-Yacht 12/03/2014 at 15:50

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I thought the reason they were so high had nothing at all to do with aerodynamics and everything to do with simply allowing the trunk to open.

Mini_Fanatic > It's a "Porch-uh" 12/03/2014 at 15:50

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Something I've never understood:

People who think driving their truck with the tailgate open "improves fuel economy". Even before the internet. How in Joe Pesci's name did anyone think that was a good idea?

ljksetrightmemorialtrophydash > It's a "Porch-uh" 12/03/2014 at 15:51

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On the subject of doing it wrong, the notation "+/-" (or "±") does not mean "approximately."

The graphic above proclaims that F1 wings provide from 50% of the car's aerodynamic downforce down to no downforce whatsoever - or even an equal amount of aerodynamic lift.

RamblinRover Luxury-Yacht > Wild Weasel 12/03/2014 at 15:52

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They knew they were putting it high, but the *exact* restriction on how high was based on the trunk, yes. If putting a big spoiler right on the lid would have gotten them what they wanted, they'd have done that.

CobraJoe > Oppo! 12/03/2014 at 15:52

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Doesn't an angled surface that "deflects air upward" create an area of low pressure underneath, similar to the explanation of the way that an airfoil works? Granted, an airfoil would be much more efficient and likely will cause less drag, but aren't they effectively doing the same thing?

Full of the sound of the Gran Fury, signifying nothing. > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 15:52

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Here's another common misunderstanding. They weren't after the downforce from the wing - if they wanted that, they could have mounted it lower down. What they were really after was the high-speed stability provided by the vertical portions of that assembly, much like the vertical stabilizer on an aircraft; in this case they had two such fins. It was just a clever interpretation of the rules, and a masterful diversion of attention, in order to gain a competitive advantage.

CobraJoe > Wild Weasel 12/03/2014 at 15:53

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Only on the street versions. The track versions actually had a lower wing.

VashVashVash > It's a "Porch-uh" 12/03/2014 at 15:53

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What surprised me most about that mythbusters was just how little of a difference the state of the tailgate made. You aren't saving gas by leaving it open, but you aren't exactly wasting it either.

Trin-Engr > It's a "Porch-uh" 12/03/2014 at 15:54

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That has got to be hilariously dodgy at any kind of speed...

Davos Swinney > Gary Yogurt 12/03/2014 at 15:54

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Funny comments like this generally get you un-greyed depending on what site/sub-blog you're on. Obviously I'm still in the grey in oppo.

loonatic112358 > It's a "Porch-uh" 12/03/2014 at 15:54

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Engineer to win should be required reading before installing any "performance" aftermarket accessories

With-a-G is back to not having anything written after his username > Gary Yogurt 12/03/2014 at 15:55

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Please respond with high scores from Pitfall 2 and Ice Climber.

RamblinRover Luxury-Yacht > '70dime 12/03/2014 at 15:55

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The wing was *that exact height* so that the trunk could open all the way. It was high and tied into the body in the first place for aero reasons, but the trunk opening question was what set it exactly. Neither purely aero nor purely aesthetics and trunk is correct. If what you're doing requires setting it within a given range, pick the point on that range you have a reason for... in this case, it was the trunk.

PartyPooper2012 > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 15:55

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They work even better on late 90s Corollas.

Ad_absurdum_per_aspera > It's a "Porch-uh" 12/03/2014 at 15:56

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Do you have any wind-tunnel pictures or CFD visualizations for pickup trucks? I seem to recall, from when driving around with your tailgate down or replacing it with a cargo-net thingy became popular because it "improved gas mileage" — that somebody showed it actually worsened gas mileage. You were better off with the trapped air bubble in the enclosed bed.

I'm having trouble easily laying hands on the evidence — the Internet was around, but the Web and the various archives were embryonic at best — but I want to say the work was done by NASA (possibly Ames Research Center at Moffett Field). I'll further dismember that it was an offshoot of some pretty economically significant work they did in that timeframe on the aerodynamic detailing of big-rigs.

VashVashVash > HammerheadFistpunch 12/03/2014 at 15:56

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http://iopscience.iop.org/0031-9120/38/6…

Its a pretty long read, but the gist of it is that the conventional fast/slow air explanation of wing function is almost completely wrong.

HammerheadFistpunch > ljksetrightmemorialtrophydash 12/03/2014 at 15:57

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I think in this diagram, the dash is meant to be a tilde "~" representing approximate, not minus.

RamblinRover Luxury-Yacht > Mini_Fanatic 12/03/2014 at 15:58

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It's an added benefit, and that was the reason the Mercedes aero cars of the 30s had fins - pulling the drag center behind the center of thrust. But - look at it this way: if you don't have the ability to accurately model airflow on the trunk lid other than smoke-wanding, and the shape of the car means a fair dead zone of turbulence with little flow, it's the most logical thing in the world to just push the spoiler out and beyond all that, where you can treat it as an isolated surface.

It's a "Porch-uh" > Ad_absurdum_per_aspera 12/03/2014 at 15:58

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See if you can find the Mythbusters episode about pickup tailgates. They have a good visualization of the "bubble."

damnthisburnershitsux > It's a "Porch-uh" 12/03/2014 at 15:59

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that's one way to carry a sheet of plywood home from home depot, they should put some flags on the end though

RamblinRover Luxury-Yacht > CobraJoe 12/03/2014 at 15:59

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...which was still ludicrously high by modern standards.

Art > It's a "Porch-uh" 12/03/2014 at 16:00

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you are an idiot in so many ways.

nerd_racing > MarquetteLa 12/03/2014 at 16:01

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This is exactly what I heard and it made the most sense to me. If you have ever worked with people in nascar or any other competitive racing, everything is a big secret to try and get an edge. If one team thinks something works and someone finds out, then all of the other teams jump on it to chase an extra tenth of a second.

TheStigsGermanCousin > It's a "Porch-uh" 12/03/2014 at 16:01

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When I saw this I just thought to myself, What the hell is that and why is it legal.

With-a-G is back to not having anything written after his username > Oppo! 12/03/2014 at 16:01

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OK, usually I wouldn't be this pedantic, but you kinda blew it there. First, fluid is 100% incapable of "pulling" anything, only pushing. The high pressure area pushes toward the low pressure area. Second, correcting people for describing airfoils as an action-reaction pair is not really warranted. From a kinetic theory of gases standpoint, that most definitely is the case.

exitstrategy > Rainbow 12/03/2014 at 16:02

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Instead of blasting all as "stupid" for driving around with tailgates down, maybe take a peek inside your own cranium and challenge the merit of your assertion regarding a vehicle that was designed for hauling pig shit.

I swear, with every new article on on JK or OPPO, it feels like I'm reading a YouTube comment section. Take the time to think about your post before you post it.

/end rant/ But you are correct. Tailgate down does increase drag by 1-3 % depending on the size of the truck. It doesn't make people stupid, it makes them un-informed. Maybe you should form an air flow religion and wander the earth smartening up all these stupid people.

Milky > It's a "Porch-uh" 12/03/2014 at 16:02

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Really who doesn't know this? " In fact, an aggressive airfoil adds a substantial amount of drag, in exchange for more traction at high speeds."

It is cool knowing though that air doesn't flow under my spoiler. I always wondered how that worked for active aero cars.

TheStigsGermanCousin > It's a "Porch-uh" 12/03/2014 at 16:02

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But boy is it cool.

Ian Bruce > It's a "Porch-uh" 12/03/2014 at 16:02

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That was way more information than I wanted to see. Why didn't you warn people that there were spoilers ahead?

twotimeuse > It's a "Porch-uh" 12/03/2014 at 16:02

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I've actually read quite a few articles that come across like this—we'll call them "scholarly diatribes." The purpose usually seems to be education with a side of criticism.

This is primarily a discussion of semantics. Spoilers and wings are two different things! Sometimes people confuse the two terms! With that said, there's absolutely nothing wrong with a wing that extends above the roof of a car. Take the following examples, with aero designed by Andrew Brilliant:

The Eclipse is my favorite example, because it also kills the myth that wings are useless on FWD cars.

*Disclaimer: These wings are (very clearly) part of a complete aero package. Putting a huge wing on your car will probably add some amount of downforce, but it may add more drag than it's worth or upset the balance of the chassis.

Vic-in-Norway > It's a "Porch-uh" 12/03/2014 at 16:03

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Ryan Carlyle, a subsea hydraulics engineer

Not to say that he doesn't know his stuff, but the fact that he is a subsea hydraulics engineer doesn't really mean anything. That's like saying "Now here is horticulturalist Tim Simmons to talk to you about rebuilding your Harley Davidson's top end."

Art > Rainbow 12/03/2014 at 16:04

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No. They do this as to gain more traction nothing else.

Ash78, voting early and often > Rainbow 12/03/2014 at 16:04

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Fully opened on the ground, they technically also serve as an airbrake, but they are fundamentally spoilers.

The more outboard ones also supplement the ailerons in banking maneuvers in most modern large jets.

IDriveEveryDay > Oppo! 12/03/2014 at 16:04

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Isn't that down-force? Since what you are describing is negative lift which is a downward force.

Nate4641 > It's a "Porch-uh" 12/03/2014 at 16:05

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When he inevitably gets pulled over, "Bet you didn't even see me behind you did ya?"

damnthisburnershitsux > It's a "Porch-uh" 12/03/2014 at 16:06

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we should have a top 10 least functional spoilers thread

I'll nominate the one on the back of the Lexus RX but any of the SUV ones would work

for a custom one I will nominate this Prius

IDriveEveryDay > It's a "Porch-uh" 12/03/2014 at 16:07

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"But why you have wing on FWD Honda" said every idiot.

TheStigsGermanCousin > Rainbow 12/03/2014 at 16:07

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They just reduce lift. There is some air braking but it is such a small amount that it doesn't actually matter. The main thing it does is force the plane onto its wheels by reducing lift. Then the Pilot throttles back to reverse thrust and that is what mainly slows the aircraft down.

davidj211 > It's a "Porch-uh" 12/03/2014 at 16:09

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Question Time!

Where do the little spoilers that sometimes come on V6 Accords and Camries and such fit in? Are they actually spoilers, or are they really wings? Or are they nothing in particular? Were they designed by engineers to improve the car's performance, or were they designed by artists to make the car look sporty?

TheStigsGermanCousin > It's a "Porch-uh" 12/03/2014 at 16:10

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Thanks for this article. I actually though that a wing on a car was just another way of saying spoiler. I have learned something today.

toecutter (so grey, I gotta wear shades) > It's a "Porch-uh" 12/03/2014 at 16:10

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I had always thought that a spoiler purposely creates turbulence at the back of the car to avoid becoming, basically, a lifting body and losing grip at speed. Also, what about using a spoiler in conjunction with a splitter on the front of the car?

Lestonian > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 16:11

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These were only this tall to be able to open the trunk

ljksetrightmemorialtrophydash > HammerheadFistpunch 12/03/2014 at 16:12

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"+/~" doesn't make a bit of sense.

Whoever made the diagram wrote "+/-" when he meant "". This is common screwup.

31ModelA > It's a "Porch-uh" 12/03/2014 at 16:13

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Now wait a minute. You can't call folks scientifically illiterate and then say things like "wings work by pushing air up".

The aerofoil shape creates and area of low density on the lower surface of the wing PULLING the wing down.

The flow of air over the lower surface of an aerofoil (which is the TOP of the "wing" on a car, or where you put your In-N-Out burger when you take your GT3 RS for fast food) follows as closely as possible to the "chord line" of the wing - the straight line drawn from the leading edge of the wing to the trailing edge. Since this distance from the leading to the trailing edge on the lower surface is shorter, the air does not have to travel as far or as fast as it does over the upper surface.

Ao, then, the upper surface of the aerofoil takes advantage of Bernoulli's principle by forcing the air to split and travel two paths - one short, one long. The air traveling the longer path from leading to trailing edge - the upper surface - must move faster in order to meet back up on the other side of the aerofoil with the ("slower") air traveling the shorter path. Bernoulli: the increase in flow generates lift.

HammerheadFistpunch > ljksetrightmemorialtrophydash 12/03/2014 at 16:15

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Common? maybe. I figured it out pretty quick so it doesn't really matter to me.

Obfuscatio: philosopher at large > It's a "Porch-uh" 12/03/2014 at 16:16

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It's all about angle of attack. If the air is coming down after passing the roof, a horizontal wing is still providing downforce.

Nick drives Stick (not Stig) > It's a "Porch-uh" 12/03/2014 at 16:16

2

Am I doing it right?

Cebu > It's a "Porch-uh" 12/03/2014 at 16:18

4

I feel like I just got my weekly dose of science. This will actually help me massively because I intend to become an automotive designer...

Now, for your next trick, explain the difference between an airdam and a splitter. My dad and I are constantly arguing about which is on our Volt.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Full of the sound of the Gran Fury, signifying nothing. 12/03/2014 at 16:18

4

No, they were up there so the trunk could open. The trunk lids are functional in NASCAR.

David-inc > HammerheadFistpunch 12/03/2014 at 16:19

2

Pressure difference plays a part, but the angle plays a bigger part. Google "angle of attack".

iaianstg > Maxaxle 12/03/2014 at 16:19

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good eye

HammerheadFistpunch > David-inc 12/03/2014 at 16:20

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Im aware of angle of attack.

absurdum > It's a "Porch-uh" 12/03/2014 at 16:21

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So the small wing/spoiler/overhang (no idea which it is supposed to be) on the top rear of hatchbacks/wagons/SUVs... Are they doing anything? No trunk to necessitate creating a blind pocket... so is it there to influence turbulence off the back of the car? Create downforce? Or just aesthetics?

Kylemaro > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/03/2014 at 16:23

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define functional, they were hardly for show on the road cars, pretty sure on both roadrunners and charges the spoilers were essentially part of the frame (welded to the frame anyway)

4play > It's a "Porch-uh" 12/03/2014 at 16:23

3

On the actual NASCAR race vehicles, the wing had an airfoil shape and did provide downforce (not much at all, but some). The main benefit of this wing design was lateral stability at high speeds provided by the two huge wing supports, which basically act like vertical stabilizers on an aircraft.

Arch Duke Maxyenko, Shit Talk Extraordinaire > Kylemaro 12/03/2014 at 16:25

24

functional

fNG(k)SH()n()l/

adjective

of or having a special activity, purpose, or task; relating to the way in which something works or operates.

Ente Süßsauer > Gary Yogurt 12/03/2014 at 16:27

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If you figure out how to become ungreyed, let me know.

72Riv > It's a "Porch-uh" 12/03/2014 at 16:27

1

1. That wing didn't do much... maybe helped stabilize the car's back end at speed (the vertical elements were probably more effective than the horizontal element... way more surface area)

2. It was set so high so you could open the trunk. The cars (back then) had to be stock. The trunk needed to work on the cars they sold at dealerships. So the wing had to be set high enough to open the trunk.

Ente Süßsauer > VashVashVash 12/03/2014 at 16:30

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TL;DR?

Full of the sound of the Gran Fury, signifying nothing. > It's a "Porch-uh" 12/03/2014 at 16:31

1

On my lowered VW Vanagon I actually mounted a spoiler on the front, and it was amazing how much more stable the vehicle was after that part was installed. I probably even gained a few MPH on the top end, bringing it from 86 to almost 90 MPH. The spoiler had a short life, sadly. I loaned the car to my mom so that she could take a group of girls to an outing a few hundred miles away. I warned her about the lack of clearance and that she needed to be careful on driveways, but I guess the warnings fell on deaf ears. She made it all of about a mile from the house before tearing it off at the entrance to the bank. I can't remember if this was before or after she left my OM-2S camera and tripod in the park...

sounbwoy > It's a "Porch-uh" 12/03/2014 at 16:34

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Question. Remember the black plastic strips that manufacturers used to install underneath the front of cars ( GM did this a lot ) which supposedly contributed to increased fuel economy? Was anything ever done to see if those were effective or not? I used to see them and always wonder "Why?

David-inc > HammerheadFistpunch 12/03/2014 at 16:35

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Okay well that's what he was talking about without getting into a discussion of differential pressures which usually means people zzzzzzzzzzzzz............

But you look at the F1 wings and it's more apparent, they have a huge amount of angle of attack, though cleverly step them so that they maintain laminar flow on the underside of them as well.

Datsun73 > It's a "Porch-uh" 12/03/2014 at 16:36

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Wings are for racecars and airplanes.

The only street cars that look good with a wing/spoiler are the ones that ecorporated it into the overall design. (Example: Ferrari F40 and Honda NSX)

Any other wing/spoiler is just an OEM or aftermarket "add-on" that does nothing beneficial for the aesthetics of a vehicle. This is not up for debate. Facts are not subjective.

HammerheadFistpunch > David-inc 12/03/2014 at 16:37

1

Sorry, didn't mean to come off as a dick. I totally dig aero but frankly (and this isn't directed at you) if you are going to start an article mocking the simplistic and wrong perceptions about aero and then gloss over something as critical as pressure differential....it rubs me wrong.

TheTick247 > It's a "Porch-uh" 12/03/2014 at 16:38

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So how does this apply to a boxier shape? Putting aside the question of "why bother?", what would be most effective for something like squarish SUV? To keep it simple, take something like a Volvo wagon (240/270/940/etc) where the roof ends and the back begins in what is essentially a 90-degree angle. To reduce drag/improve laminar air-flow, would you want a spoiler that extends flat from the roof-line to keep the air following that line further? Would you want a wing or similar that directs air down below the roof-line extended to reduce the size of the pocket of air immediately behind the vehicle that creates drag? I've seen various spoilers/wings on wagons and SUV's and wondered which design was the most effective or if they they were anything more than aesthetic.