Slide Rule Chic: Edgy can be aerodynamic, too
Click above to view high-res gallery of the Ford Flex
The classic idea of aerodynamics gives rise to mental pictures of vehicles shaped like a smooth suppository. Reality turns out to be different, thankfully. Cars like the Ford Flex may appear weighty and as slippery to the wind as a barn while actually sliding through the atmosphere far more gracefully than one might guess. Aerodynamics studies by all automakers have led to the startling discovery that vehicles like the squared-off Flex actually manage their airflow quite well, thank you, and sanding off the corners hinders, rather than helps.
It's the same over at Toyota where they're calling strategically-placed folds "aerocorners." While it's long been held that a teardrop shape is the most aerodynamic, that's not necessarily the case and a droplet-shaped vehicle isn't terribly practical; just try to put that armoire in your first-gen Honda Insight. The worry that all cars will look the same when aerodynamicists start to take over is unfounded, as discoveries in the wind tunnel show that things aren't always as they appear, and there's plenty of room for uncommon design to still cheat the wind.
Gallery: Review: 2009 Ford Flex
[Source: NYT]
Reader Comments (Page 1 of 2)
Mobius_1 8:38AM (12/26/2008)
I'm actually kinda surprised, but I suppose nothing is really ever quite as it seems. First time I saw the Flex I wondered how un-aerodynamic it would be.
I'm, for once, happy to be proven wrong. 0.355Cd is damn impressive, lower than, just to name a few, the Mustang, Countach, Escape, and Tiguan.
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Derek 10:25AM (12/26/2008)
.355? It is only good "for a box". While I do like the styling on the Flex, that is far from aerodynamic. The very large frontal area will only increase the drag on the vehicle as well.
Now, something like the Mercedes Bionic is impressive. A box shape with a 0.19 Cd. That is similar to the EV1 and beats the Prius by 26%.
http://en.wikipedia.org/wiki/Mercedes-Benz_Bionic
Mobius_1 10:58AM (12/26/2008)
Derek, I don't really think it's that simple. I mean, do you want to be seen in that Merc?
On the other hand, the inspiration is worth taking, ie from fish, since they have to be fluid-dynamic, and air is essentially a fluid.
ugg.tryptophan 3:50PM (12/26/2008)
Derek, the difference between the flex and the benz is that one is a concept and one is production
Derek 9:13PM (12/26/2008)
I wouldn't want to drive either, they're both far too tall for my tastes. If I had to drive one though, it would be the Merc. It would be quieter inside, less affected by crosswinds, have more power available for highway passing and use less fuel.
Anyways, the point is that .355 isn't anything to brag about. A Mini and a Volvo 940 both have a 0.35.
arturo 5:28AM (12/27/2008)
The people I know that Have a Flex are pretty happy with their vehicle. most of them traded their old minivan. Most of them were impress for the attention this car gets on the street. They also seem to be happy with everything this crossover offers. So kids if your mom is trying to buy a minivan, convince them that this flex is one.
TigerMil 8:45AM (12/26/2008)
1. If I wanted a Suburban, I'd buy an Escalade.
2. Flex is still fugly.
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Sea Urchin 9:05AM (12/26/2008)
I have to disagree, in person it looks rather good.
Arumage 9:06AM (12/26/2008)
To each his own. I personally like the Flex, and in most tests, it's beating it EPA numbers while carrying its passengers more comfortably. Although, it doesn't look very good in some of the colors you can get it in. All white doesn't look good at all IMO. Sterling gray with the white roof looks great though.
ActionAlex 8:49PM (12/26/2008)
If you want a suburban, why don't you just buy a suburban. Chevy still makes 'em.
ugg.tryptophan 3:47PM (12/26/2008)
the flex is like the clubman, wierd in studio shots, awesome in person
happy_penguin 10:47PM (12/26/2008)
I wonder how many people who think the Flex is ugly just love the xB, which is truly, hideously ugly.
At least the Flex has style.
nardvark 8:55AM (12/26/2008)
When I read the full story of this a few days ago (NYT maybe?), it implied that a big part of the improvement has to do with pushing air around areas of the car that can't be fixed easily with shaping, such as wheel wells and the undercarriage. So instead of trying to put goofy slats over the rear wheel-wells, or ugly flat wheel covers, you use the front corners of the car to push air out and around the wheels, bypassing the issue all together.
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Derek 10:33AM (12/26/2008)
Pushing the air out and around the wheels helps, but is still not as efficient as just smoothing the flow over the wheels. The OEM's use these other tricks because fender skirts aren't popular currently. Take a look at cars purpose-built for good aerodynamics. Many Lake Bonneville racers, as well as the Prius, Insight, EV1 and Aptera all have covered wheels, to name a few. The later Ford Probe concept cars even had flexible skirts over the front wheels to lower drag.
Richard 9:08AM (12/26/2008)
In fact, one of the most sharply creased cars in the last 20 years was also one of the most aerodynamic...
"In February 1985 the Subaru XT, considered to be the ‘most aerodynamic car in the world' was introduced. "
http://www.conceptcarz.com/vehicle/z2036/Subaru-XT.aspx
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notYou 9:33AM (12/26/2008)
(I am not a physicist, but let me muse...)
I've always wondered why the "teardrop" shape has attained the defacto-status of most aerodynamic when raindrops achieve a terminal velocity of only 5-20mph?
I mean, I understand the reasoning: since water is malleable, it will self-define the most optimum form for it's environment. But since it only falls at 5-20mph, one would have to presume there are ore optimum shapes at other rates of speed (ie the rates at which we judge most modern vehicles -, 30mph+ for medium-long range). And let's not forget the fact that we're conveniently ignoring density and mass (among other things).
To me, the teardrop is a beautiful natural - and probably optimum - result of a specific set of parameters, which may provide insight into other situations, but would hardly provide the blueprint for everything or anything else.
Isn't that obvious, or am I missing something?
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Kumar 9:59AM (12/26/2008)
Not really, just that teardrops/drops of water don't have bumper regulations and other stuff that sets a basic shape. One other aspect of the optimal shape that should be taken into consideration is the optimal shape in traffic or open road. We've all tuned into at least a few minutes of NASCAR and Indycar, enough to know about designing a car to draft very well, versus designing a car to drive by itself very cleanly.
Sure, a giant point on the front of a car would probably make it slice through the air a little better, but then we'd be driving around impaling pedestrians on crosswalks Ming-style all the time Flash. ;)
Derek 10:25AM (12/26/2008)
The terminal velocity of a raindrop is affected by the weight/drag ratio. Water is significantly less dense than steel, so a steel raindrop would fall much faster (ouch!) If you drop molten metal, it forms a teardrop as well.
Look at jets (subsonic designs - different rules apply above the speed of sound) and submarines. Teardrop shapes dominate there also.
Kumar, a pointed nose is not a real advantage until you talk about supersonic speeds. A rounded nose is just as good below the speed of sound. At subsonic speeds, a pointed tail is far more important, but leads to a long car that would be hard to park.
miles 11:20AM (12/26/2008)
One of the primary reasons for the teardrop shape of raindrops is the 'surface tension' of the liquid. Good luck writing that equation into the shape of a car!
Dan 12:15PM (12/26/2008)
Teardrops aren't "teardrop shaped" any more than hearts are "heart shaped", and they're not very aerodynamic.
Fish-shaped on the other hand...