Quote:
Originally Posted by ChazInMT
If you add only 1 foot or less to it, the chances of you getting it right are pretty darn slim, at best you could equal the Cd, but it's a 80% chance you'd make it worse.
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I'm curious how you came up with those conclusions?
I would have said it's not too difficult to extend the roof/sides of the hatch above the tail lights - continuing the existing plan & profile taper would be the conservative design approach.
The result will be a smaller base area where flow detaches and likely a lower Cd.
I'd agree there's probably a very small (~1-2% at 55 mph would be my guess) improvement in fuel economy with a short extension. The builder would have to decide how much effort is justified for a small gain.