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Old 06-02-2011, 10:35 PM   #1 (permalink)
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cap on car

My car is a convertible, so some mods are a bit harder, or altogether impossible, to do than on a normal car. But I had an idea, if I were to use a screen that goes from the top of the rear windows to the trunk to make a sort of cap, does anyone think it would be very effective? I remember reading in another post using screen as a grill block but someone said it would only work if the the screen was at an angle. I'm making a picture of my idea now.



In the morning sometimes there's leaves on my roof and as I start to drive they get stuck right on my rear window, the vortex there is clearly visible and must create quite a bit of drag, and it would be awesome to reduce it!

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Old 06-02-2011, 10:40 PM   #2 (permalink)
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Something like this, not very good with Internet drawing tools haha
there would be supports and stuff of course
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Old 06-03-2011, 03:56 PM   #3 (permalink)
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screen

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Originally Posted by capnbass91 View Post
My car is a convertible, so some mods are a bit harder, or altogether impossible, to do than on a normal car. But I had an idea, if I were to use a screen that goes from the top of the rear windows to the trunk to make a sort of cap, does anyone think it would be very effective? I remember reading in another post using screen as a grill block but someone said it would only work if the the screen was at an angle. I'm making a picture of my idea now.



In the morning sometimes there's leaves on my roof and as I start to drive they get stuck right on my rear window, the vortex there is clearly visible and must create quite a bit of drag, and it would be awesome to reduce it!
My library is certainly incomplete and if there had ever been a dedicated research project to investigate such a thing,it could have easily slipped my net.So,scientifically,I can't give a hard answer.
Here are some things that enter my mind:
* air cannot support loads,so a porous surface as the screen may be 'invisible' to the air and will still be affected by any variations in flow velocity or pressure variations 'contained within the screened area.
* if separation is imminent,the presence of the screen may offer no 'surface' for which the flow to re-attach.
* if the surface had more substance( like the laser-drilled panels on some recent experimental research aircraft),and if suction were applied inside it,you'd have a chance for remarkable drag reduction.The snag so far has been the amount of power to drive the air mover.
* for practical home streamlining projects we may be forced to use 'solid' surfaces with which to enhance airflow.
* A doped fabric covering was used on the US' first amateur streamlined dry lakes land speed record car to good effect.
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Old 06-03-2011, 05:07 PM   #4 (permalink)
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Mercedes made a front windshield "wing"/deflector to relocate the flow above the drivers and thus the turbulant section.
Still aero but with the top open!
It's called aircap.
It has a cd of 0.28 !!



Mercedes-Benz AirCap calms convertible winds - Automobile Magazine Blog

Last edited by beer; 06-03-2011 at 05:14 PM..
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Old 06-03-2011, 05:20 PM   #5 (permalink)
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0.28 my foot.

OP, not sure what you are describing.
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Old 06-03-2011, 05:36 PM   #6 (permalink)
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roof up?

Quote:
Originally Posted by beer View Post
Mercedes made a front windshield "wing"/deflector to relocate the flow above the drivers and thus the turbulant section.
Still aero but with the top open!
It's called aircap.
It has a cd of 0.28 !!



Mercedes-Benz AirCap calms convertible winds - Automobile Magazine Blog
beer,do you think the Cd as recorded with the top up on the M-B?
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Old 06-03-2011, 06:51 PM   #7 (permalink)
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Top on! Duh
But still this the aerocap reduces the wake, compared with other cabrios.
But ofcours it main use is the keep the passengers out of the wind
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Old 06-03-2011, 07:01 PM   #8 (permalink)
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passengers

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Top on! Duh
But still this the aerocap reduces the wake, compared with other cabrios.
But ofcours it main use is the keep the passengers out of the wind
I think that's it.I drove the Autobahn in 1997.Doing 124 mph in a rented Mitsubishi Galant was passed by big 6-series Bimmers and Benz coupes and sedans.
Can't imagine what an open car would be like at those speeds.I don't even like 80 mph on a motorcycle.
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Old 06-03-2011, 08:08 PM   #9 (permalink)
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I don't think it's worth it. What you're describing is basically just what the soft top is.
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Old 06-03-2011, 09:43 PM   #10 (permalink)
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Looks to me like you need to use Tiny Pic for your photo hosting needs.

You wanna do something like this eh?


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