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Old 01-25-2010, 01:26 PM   #11 (permalink)
Aero Deshi
ChazInMT's Avatar
Join Date: Jan 2010
Location: Vero Beach, FL
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MagMetalCivic - '04 Honda Civic Sedan EX
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The question I have with your dark red is that it is scaled to the size of the vehicle. I think that as long as we're talking about largish objects like cars, trucks, boats & motorcycles, the 115 flow separation rule applies. So as long as we keep our top radius line from going past that 115 point, it really doesn't matter the shape. The reason we use this particular template is that it has the best "surface area/ wake generation" ratio. The segment we use is very similar to section 5.

This brings up another point that I think people don't often consider. We spend a lot of time trying to make the tops of our vehicles as aero as possible, and often neglect the sides. The air moving around the sides of our trucks and cars has a large impact as well I say. On my Pickup, the sides are about 22" tall on the passenger cabin, just in front of the bed. The roof width at the top in this area is about 52" so with 2 sides at 22", that's 44" of air surface. So we worry about 55% of the equation and neglect the other 45%. This is why I have designed a taper in the sides of my aerocap when viewed from the top. Doing this results in a fastback design.

More food for thought....It is often said that the best possible Cd we can achieve is .18 based on the .09 holy grail of aero shape in ground effect...The sides of the vehicle are not in ground effect. Hmmmmmmmmmm.

Last edited by ChazInMT; 01-25-2010 at 02:38 PM..
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