Thread: Boat tail easy
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Old 01-23-2023, 11:43 AM   #28 (permalink)
aerohead
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'difference'

Quote:
Originally Posted by Phase View Post
What’s the impact difference between tapering just the roofline versus tapering the sides too as a full boat tail? I noticed all the eco modders taper all directions for their boat tails. Makes sense. But what about if I just extended the roofline and didn’t do too much to the sides? Think Mercedes EQXX or the light year zero. The sides of the rear only have a super small taper that isn’t very noticible, the main thing is their rooflines going down and extending

How much CD drop would I see just be extending down my roofline while only lengthening out the sides like those cars?
1) Ph.D. Elliott G. Reid, of Stanford University, studied this very subject.
According to his research, you'd suffer a 16% drag penalty by not providing the plan-taper.
2) Lightyear and EQXX are both boat-tailed in plan-view. From rear axle centerline back.
The tail on the EQXX constitutes 28.5% of the car's total length, and ends with a departure angle of 13-degrees to body centerline.
15.5-degree departure angle up on top.
The diffuser looks like 8-degrees. I can't really tell.
The rear transom is 337mm narrower than the car's maximum width.
You'll discern it in the overhead photograph provided by Mercedes.
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