Quote:
Originally Posted by Phase
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?
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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.