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Old 08-22-2012, 07:30 PM   #14 (permalink)
aerohead
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"full"

Quote:
Originally Posted by 2000neon View Post
I am really considering a much more dramatic, full kammback for my Neon. Allowing the sides to taper in as much as possible without interfering with opening the trunk. Also, I am considering making a hinge system on the top, to allow me to fold it back and use the trunk. My issue is with building rounded corners on the top-to-side transition.

I know that rounded corners are preferred aerodynamically speaking, ease of construction is another story. To the best of my understanding, this is because with just a straight, creased edge, the airflow "trips" over the edge, causing vortices which will increase drag and severely limit the drag reduction potential, am I correct?

So how drastic of a rounded corner does it need to be? I assume the more rounded the better, but is there a known minimum amount of curve that is required?

Finally, I know people can compare the amount of roundness by talking about the size of it, for example a 3/4" radius. So does that mean that if the curve was a whole circle, it would be 1.5" in diameter? Is that sufficient for avoiding air tripping over the edge? I am just trying to get my head around what kind of curve I need, to figure out the best way to build it.

Thanks for any input, you guys have already helped me out so much in building my Neon to where it is, and I appreciate it. This site is great!
I think that I'm going to need some help with respect to "full".Will it extend to the original length of the car,converting from a notch back to K-form roof,or are you planning to extend it beyond the bumper,combined with boat-tailing to go for really low drag?
If you maintain factory length you could mimic the architecture Chrysler did (as GM has done with today's VOLT),maintaining the same roof section curvature and greenhouse tumblehome,intersecting with an identical crease as on the standard car.
If you go longer,you could gently increase the roof/greenhouse edge radii as you progress back.
The 'Template' curvature is meant to prevent radical pressure variations which lead to the bleeding into the low pressure area,which creates the viscous shearing forces which sets up the nasty attached longitudinal vortices.
Over at the full-boat-tail trailer thread there are some pictorial drag tables.One of them demonstrates the difference edge radii can play with respect to drag coefficient.(It will show a bus of different configurations,with corresponding Cd).
The really low drag cars are circular,or semicircular when viewed from behind (this is excepting solar race cars with their PV arrays).
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