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Just curious : I thought that the Previa was already the 'ideal' shape with its egg like front end. How does making the front more pointed help aerodynamics ?
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Actually, aerodynamically it would be better if I drove it backwards
See Dymaxion car.
The factory CD for the '93 is about .35. Good but not great considering the shape. My guesses as to why it's not better are (in ascending order of magnitude and excluding the obvious mirrors, wheel covers etc.):
a) The widshield wipers have no cover. (The aptera has a better CD than my wipers)
b) The front bumper overhang is pretty huge. If you look at new cars the shape is very similar to what I have done, mine's just not as rounded.
c) The curved trailing edge all the way around the back of the vehicle must act like a freakin' parachute. Is there a trim strip the right shape to make a trip edge like the
Volt? (author makes the sign of the cross, mumbles "All hail the Volt")
d) All of the above
e) c and d
There will be a test at the end.
So I'm in full agreement on the rear being the worst offender, it's just that the boat tail is a much larger project.
I think your blunt front ends thread is what got me all hot and bothered about a serious airdam and the correct shape. My take on it is that the overhang of the bumper created a pressure area under it that would be relieved if the air were directed up and around the sides. That pressure would push more air under the van (water streaks confirmed this). Better to go over and/or around. I'm just giving the air an easier choice. I think we have a tendency to think mostly about the roofline but the sides are just as important especially with a tall van.
The dam sort of designed itself I just followed the lines. I will put in plexi light covers to finish it off at some point. I have to do a coastdown test one of these days.
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( Since you never break the sound barrier )
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Ah, yes, but the
taste barrier will never hold me back.