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Old 02-24-2009, 09:53 AM   #1 (permalink)
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Teardrop aerodynamics... in reverse!

Cd started a thread about which car's shape is closest to a teardrop shape.
Looking around on the streets I see a lot of teardrop shaped cars, but all of them are driving backwards! The efficient teardrop shape is round in the front and tapered in the back, not the other way around, as seen in this thread and this video.
From what I can see, car would be much more aerodynamic if they were driven in reverse. Here's what I mean:
This is how close a 5-door Citroen C4 is to a teardrop:

And here is the same car going backwards:

Which is closer to a teardrop?

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Old 02-24-2009, 10:39 AM   #2 (permalink)
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You're right, except that the windshield slopes down too fast
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Old 02-24-2009, 10:55 AM   #3 (permalink)
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Quote:
Originally Posted by MazdaMatt View Post
You're right, except that the windshield slopes down too fast
I've noticed that the older the car, the closer the windshield is to vertical, while the hood is horizontal. The new trend is to blend the windshield and hood into one long slope. This helps the airflow move over the windshield instead of smacking into it. I guess the long engine bay it there for safety reasons.
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Old 02-24-2009, 11:45 AM   #4 (permalink)
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whoa, poland, i'm 1/2 polish, & i went over to poland a couple years ago, was awesome, anyways

intresting theory...but i think having the front hood/bumper split the air before it hits the rest of of the car helps...but i could be wrong
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Old 02-24-2009, 12:03 PM   #5 (permalink)
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Quote:
Originally Posted by malibuguy View Post
intresting theory...but i think having the front hood/bumper split the air before it hits the rest of of the car helps...but i could be wrong
Big end first is better (assuming proper taper aft).

See: http://ecomodder.com/forum/showthrea...-end-3708.html
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Old 02-24-2009, 12:54 PM   #6 (permalink)
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I'm going to assert that it's very likely cars continue to have hoods extending in front of the passenger compartment because sitting in the front of the vehicle when you crash into something at speed is probably bad for your health.

Putting the windshield way out in front of the driver is probably good for aero, but much more than that it keeps your head away from the hard, unforgiving glass when you come to an abrupt stop upon impact.

But the windshield can't be at the extreme front of the car... because then you can't access the engine to perform repairs. The engine can't be in the passenger compartment because of fumes from a poorly maintained one and because of noise/vibration (everyone wants a silent cabin). The vehicle can't have a luggage trunk in front because depending what you keep in the trunk, your set of golf clubs cound become skewers if you slam into a brick wall.

So while the shape of cars today may not be ideal from an aero perspective, I think they are as they are because they have to be, to an extent. We'll see better and better compromises/solutions as time goes by, always do
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Old 02-24-2009, 01:10 PM   #7 (permalink)
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Quote:
But the windshield can't be at the extreme front of the car... because then you can't access the engine to perform repairs. The engine can't be in the passenger compartment because of fumes from a poorly maintained one and because of noise/vibration (everyone wants a silent cabin).
^ Wonder if they still build full size vans this way?



This is the best example I can think of. I currently have the Pontiac version, and had one identical to this except different wheels.

Makes me wonder about something. If the teardrop is the best aero shape, would the reverse teardrop be the worst shape? Probably not really, a parachute would be worst, but I wonder how they would compare anyway.

I used to pull my 5x8 enclosed trailer with my 6000 wagon. It was both narrower and lower than the trailer. 3.1 engine. Pulling it was a breeze, literally. I could sail down the highway at 65 easily, could have done 70 if I wanted to.

Now with the van, towing it is a royal pain in the a$$. Same trailer. 3800 engine in the van, the van has a lot more power for its size. The van is only slightly lower and the same width as the trailer. I have a hard time maintaining even 55 on the highway. 65 is out of the question. It feels like a constant hammering wind gust about every second that is slowing me down drastically at anything over 45. I wonder if the aero of the van has anything to do with it, maybe it is trying to reattach the airflow quicker than the 6000 wagon, then the trailer has to break it apart again.
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Old 02-24-2009, 01:32 PM   #8 (permalink)
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Quote:
Originally Posted by wagonman76 View Post
^ Wonder if they still build full size vans this way?



This is the best example I can think of. I currently have the Pontiac version, and had one identical to this except different wheels.
Well, here are a couple 2008 Fullsize vans..

Ford

GM

Chrysler

- and even on your Pontiac minivan example, there's a good 2 feet in front of the windshield, which looks to me like it ends pretty much in-line with the front of the rim of the front tire. I'd guess the steering wheel is about in line with the side mirrors..


These vans... they're long gone.



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Old 02-24-2009, 02:38 PM   #9 (permalink)
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Quote:
Originally Posted by shovel View Post
But the windshield can't be at the extreme front of the car... because then you can't access the engine to perform repairs.
You could make the hood tilt forward.
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Old 02-24-2009, 03:16 PM   #10 (permalink)
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Seeing that last van pic suddenly had me singing the scooby doo song ...in my cubicle...quietly..in my head.
A brick has better aerodynamics

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