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Old 04-03-2023, 10:25 PM   #31 (permalink)
aerohead
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'drag'

Quote:
Originally Posted by AdrianD View Post
Not much work done in the past two years, a newborn kid and building a house from the ground up took away my free time...


But now I have time to attempt a bit of rear aero cleanup...

This is after a 12 mile drive on a muddy road, with speeds under 30mph:


Jeep made a spoiler to help keep the rear hatch clean and people report it's helping:




Am I right thinking that if the hatch is cleaner, the rear wake is reduced, also reducing drag?

The price tag is around $150, so with 0.2L/100km gain (~2% improvement) it would pay for itself in 2-3 years at the current fuel price.
* The wing is forcing air over the roof to blow over the backlight, hopefully keeping some of the road spray from reaching the glass.
* In the past, measurements showed only drag 'increase' with such devices.
* The wing itself adds frontal area.
* And the wing has its own drag.
* To reduce drag, you'd blend a roof extension out as far as you dared, which included side extensions to box in that area, all the while providing a slight cross-sectional reduction along a streamlined path, generating pressure recovery. The only thing aerodynamics is about.
* You might take a look at the 1987 Renault Vesta-II concept, or Mercedes-Benz' Bionic Boxfish concept. The back of these two 'squarebacks' would be the gold-standard for streamlining.

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