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Old 02-06-2023, 11:40 AM   #35 (permalink)
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'louver drag'

Originally Posted by Cd View Post
Piwoslaw : Appreciate that.
Even if I do get this thing fully road legal, I don't drive much at all so wouldn't be able to do any testing.

Aerohead :
There would be a huge amount of drag where the louvers are.
The underside would also most likely not be smooth enough for good attacment all the way to the rear.
I planned a diffuser and a venturi tunnel, but it's a pain working under the car - especially since I live in an apartment and don't have a garage.

I planned to add window screen over the louvers. This would help the drag, but I'm not sure how much.

Overall, I would expect a cD similar to your truck, but much higher because of the louvers.

When the 5th generation Civic came out, Honda qioted a .32 cD for the Civic coupe, and a .31 cD for the hatchback .
However, Honda quoted a .36 cD for the coupe in 1996, when talking about how the Civic cD compared to the Insight.
The shape was identical to the 1992 - 1995 model though, with only the addition of a different headlight design.
So I'm guessing my cars stock cD to be at closer to .36 to start.
I spent a few hours noodling the Honda.
With zero elongation, but 'optimizing' details, I came up with Cd 0.2177.
I allowed for the louvers, using Texas Tech University's GM Aero Shell vs Cab-Wing- half tonneau as a 'discounting' metric ( there was only a 5.94% drag penalty between to two! ).
Concentrating on the aft-body, and respecting 'ichtyoid' ENTRANCE / RUN proportions, it seems like a 77-inch tail extension would place the car in the drag 'bucket.'
I keep coming up below Cd 0.14 potential.
It would require sweating all the details, something some members might enjoy, just for the challenge.
Your rendering evokes really high performance. It's really inspiring.
Photobucket album:
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