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Old 02-10-2010, 06:23 PM   #30 (permalink)
aerohead
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elaborate

Quote:
Originally Posted by 3-Wheeler View Post
AeroHead,

Now I'm curious...

Would you care to elaborate on what you would do?

Thanks, Jim.
Jim,this was one of my quirky thought experiments and I hope basjoos won't be offended.This is what I did.
From a side shot that basjoos provided I drew in a ground plain under the tires.With a French-curve I extended the apparent hatch line rearward and projected a prolate ellipse forward to capture the nose of the Civic to ground level.
This established a 'template' around the car,as Jaray,Kamm,Lay,and others had done with development vehicles.
Locating the 'top' of the roof camber I was able to establish the position of frontal area at 44% of overall body length,aftbody constituting 56% of body length and L/D= 2.416.Exit angle at zero ground clearance is 35-degrees,and the exit angle at the boat tail 'hatch' is 26-degrees.
If I stretched only the aft-body out to 1.78-D ( D is 2H ) which is the aft-body of the 2.5:1 streamline body,the new point at ground level to define the 'effective' tail would produce Mair's 22-degree angle.
The intersection of this new template with the line of the undercarriage projected straight back,would define a body with Cd 0.12 for a standard Civic.
NOTE: The diffuser portion would not respect SAE's 10-degree break-over angle and this part would have to be 'active',or the tail unit would have to comprise a trailer rather than a full cantilever tail.
I've brought nothing new of my own here.Kamm's full tail produced Cd 0.15.Jaray's,with a front airdam got Cd 0.13.Walter E.Lay produced three cars with Cd 0.12 this way.AeroVironment got Cd 0.089 with wheel fairings on the Sunraycer,Honda Dream-2 got Cd 0.10.
I believe that a convex windshield,careful cooling system ducting,fairing of the tires and the tail mods would push the Cd to,or below 0.10.
Practical?
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