Quote:
Originally Posted by Sven7
The 20* comment was aimed at your proposed boat tail.
The flow over your rear window is probably not attached. Flow over the roof is, though. In your diagram you show the boat tail beginning at the crux of the roof and rear window, where flow would normally separate. Instead of letting it to that, you guide it onto the boat tail and continue the smooth flow to the end.
The Mitsu has VG's to put more pressure on its wing, creating downforce (as I understand it). Engineers likely spent days in the wind tunnel tuning this and its purpose is not drag reduction. Creating vortexes takes energy and that energy is coming from the car's engine. Forget about VG's!  |
Several forum members have tested VGs; the Mitsubishi engineers published a study on their VG design and was reported on by Autospeed in a 4-part article--the VGs resulted in a .006 reduction in Cd and slight reduction in lift, but it was never made clear if the baseline was with the wing or without. The purpose of the VGs in that case was clear, and their effect in the independent tests of Autospeed and some people here: flow does stay attached over the rear window better with the VGs, but in FE testing they don't seem to make a difference because of the slight drag penalty inherent in their use. What's intriguing about the OP's question, however, is the use of VGs as part of a
comprehensive plan: keeping flow attached over the rear window and trunk to take full advantage of a smaller tail off the end of the car, the theory being that the smaller wake made possible by the smaller, easier-to-live-with tail will more than outweigh any drag created by the VGs while also improving aerodynamics more than the small tail would be able to with the air detaching over the rear window. I think it is certainly worth investigation and testing. But, I'm also no engineer--I just read a lot.
Quote:
Originally Posted by fauxpaws
Sven7: I see your confusion, you are looking at the red lines, which are similar to other tails I have seen. However, my proposal is to only build the blue lines, which begin aft of the trunk. This would obviously be less effective than beginning at the roofline, however it has the advantage of leaving rearward visibility unobstructed.
Now that you see what I am really proposing, what do you say? Is it worth my time, or is this not something that will be effective?
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More advantages than just rearward visibility; a smaller tail means less material and cost, less work to fabricate, and less intricate design (as you don't have to follow so many of the car's existing curves).