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> cool windscreens, how do you make em
usa4cheer
post Feb 16 2006, 06:35 PM
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I am working on my grassroots motorsport challenge car and want to take the windshield out of my car and want to do the mini windscreen. How do you make it???
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skeates
post Feb 17 2006, 01:01 AM
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I hope that I can shine some light on the aerodynamics as far as the CD is concerned between the Flaired wheel wells and the non flaired wheel wells....

(Given that both are painted steel with roughly equivilent surface roughnesses):

The flaired wheels will created a larger surface area perpendicular to the air stream and therefore create a larger wake of turbulence behind the car as the airstreams seperate from the car, thus creating drag. This is evident when one stands directly infront of the car and looks at it head on. If the car in this case were 2-dimensional one would say the the car with the wheel flairs takes up more space than the one without, thus it displaces more air (read: deals with more friction) as a result.

Also the wheel wells add surface area to the sides of the car. As air moves past the car one can assume that the air directly touching the surface of the car is stopped in its tracks and as you move away from the car the speed of the air gradually increases to the overall speed of the car (known as the freestream velocity). This is why the wind is always much faster at about 10 to 15 feet above the ground. Now, keep in mind that this all happens in the course of a few micro-meters on the car. None the less this creates a certain friction which the car must fight against - the fast the car goes the more friction this creates. An example of this would be like trying to run in water. If one moves slowly it is pretty easy, but if one tries to go faster it gets much, much harder.

Now, as far as the flairs go - from an aerodynamic standpoint the stock fenders are more desireable as they end up creating less drag. However, the boost in handling and traction for very high accelerations provided by the extra meat under the wheel wells well outweighs the aerodynamic cost of the flairs - especially if one applies other aerodynamic techniques to the front of the car (which is where most of the drag is coming from anyways).

Hope this wasn't too long (IMG:http://www.914world.com/bbs2/html/emoticons/yellowsleep[1].gif) ,

Peace and Hope,

Steven

(IMG:http://www.914world.com/bbs2/html/emoticons/driving.gif)
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Posts in this topic
usa4cheer   cool windscreens   Feb 16 2006, 06:35 PM
Jeroen   you can just buy it from most vendors of fibreglas...   Feb 16 2006, 06:44 PM
d914   grassroots has a VERY small budget for building ca...   Feb 16 2006, 08:00 PM
alpha434   2006$ HOLY COW!!! If you can...   Feb 16 2006, 08:25 PM
davep   Why remove the windshield? My friends GT can run e...   Feb 16 2006, 08:32 PM
alpha434   Dave is right. To an extent. You are removing the ...   Feb 16 2006, 09:00 PM
SirAndy   ...   Feb 16 2006, 09:14 PM
one914racer   homemade   Feb 16 2006, 09:34 PM
Twystd1   Thomas.. I love that car.... That sucker is CLEA...   Feb 16 2006, 09:42 PM
alpha434   <...   Feb 16 2006, 09:42 PM
r_towle   So, a custom windscreen. Either you make a foam t...   Feb 16 2006, 11:15 PM
Aaron Cox   <...   Feb 16 2006, 11:28 PM
usa4cheer   WOW what a great response, it would have a taken ...   Feb 16 2006, 11:46 PM
alpha434   You get free weblog space with membership. ...   Feb 17 2006, 12:04 AM
alpha434   1969 Porsche 914/6 - Technical specifications This...   Feb 17 2006, 12:27 AM
Aaron Cox   that goes against everything ive heard.... ...   Feb 17 2006, 12:54 AM
alpha434   My numbers were WITH. That's what I've be...   Feb 17 2006, 12:59 AM
alpha434   Adding fender flares and increasing frontal profil...   Feb 17 2006, 01:00 AM
skeates   I hope that I can shine some light on the aerodyna...   Feb 17 2006, 01:01 AM
SirAndy   ...   Feb 17 2006, 01:02 AM
skeates   Andy - you are correct in saying that the frontal ...   Feb 17 2006, 01:15 AM
messix   i think an open cockpit would creat more drag than...   Feb 17 2006, 01:30 AM
redshift   With no back window, the vortex shit is all differ...   Feb 17 2006, 02:25 AM
Mugs914   <...   Feb 17 2006, 02:57 AM
URY914   Sounds like you guys work for NASA or something   Feb 17 2006, 07:45 AM
skeates   Thanks Mike, Yea, I got my CD mixed up with the e...   Feb 17 2006, 10:12 AM
SirAndy   <...   Feb 17 2006, 11:11 AM
airsix   I enjoyed the posts (such as Mike's) with good...   Feb 17 2006, 03:36 PM
marks914   Here is how you make a cut down windshield: The be...   Feb 17 2006, 03:55 PM
WRX914   if anyone would be willing to part with thier cut ...   Feb 17 2006, 04:00 PM
marks914   Has anyone here actually been in an automotive win...   Feb 17 2006, 08:48 PM
URY914   ...   Feb 17 2006, 09:07 PM
SirAndy   ...   Feb 17 2006, 09:21 PM
J P Stein   No, but I've been in a aeronautical wind tunne...   Feb 17 2006, 09:21 PM
marks914   <...   Feb 17 2006, 10:08 PM
airsix   ...   Feb 18 2006, 02:01 AM
usa4cheer   a guy ran a 914 with 2.3 turbo ford motor last yea...   Feb 18 2006, 02:43 PM
J P Stein  

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