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theycallmeebryan · 07-20-2009, 02:58 PM

Keep in mind, the right chart that shows the .25 t/c being optimal is at a reynolds number of 400,000, much much lower than a car traveling at 55mph.

Orangboy, for your vehicle, you want to experiment with shapes at RE of around 11,200,000, considering your vehicle is 15 feet long stock, and i'd expect atleast 5 feet to be added for a boat tail

RE = 9360 * SPEED(in mph)*DIMENSION(in feet)

Using a program called DesignFoil, i have found that the best shape for a vehicle traveling 60mph has the location of minumum pressure located 70% the length of the cord(from front to back). The shape is NACA 67-025.

However, this shape has a center of pressure that is out in front of the shape 8% of the chord length. What this means is its very susceptible to cross winds, and will get blown around.

When you move the max width forward a bit, the cd increase slightly, but the center of pressure moves backward drastically, meaning its better in crosswind. For example, going from NACA 67-025 to NACA 66-025 (70% to 60%), the COP is moved back to 30% of the length (IE, its now inside of the shape)

07-20-2009, 02:58 PM	#3 (permalink)
theycallmeebryan Master EcoModder Join Date: May 2009 Location: New Jersey Posts: 389 2003 Ninja EX250 - '03 Kawasaki Ninja EX250 90 day: 78.57 mpg (US) Saturn - '99 Saturn SL1 Base 90 day: 47.27 mpg (US) Thanks: 25 Thanked 58 Times in 37 Posts	Keep in mind, the right chart that shows the .25 t/c being optimal is at a reynolds number of 400,000, much much lower than a car traveling at 55mph. Orangboy, for your vehicle, you want to experiment with shapes at RE of around 11,200,000, considering your vehicle is 15 feet long stock, and i'd expect atleast 5 feet to be added for a boat tail RE = 9360 * SPEED(in mph)DIMENSION(in feet) Using a program called DesignFoil, i have found that the best shape for a vehicle traveling 60mph has the location of minumum pressure located 70% the length of the cord(from front to back). The shape is NACA 67-025. However, this shape has a center of pressure that is out in front of the shape 8% of the chord length. What this means is its very susceptible to cross winds, and will get blown around. When you move the max width forward a bit, the cd increase slightly, but the center of pressure moves backward drastically, meaning its better in crosswind. For example, going from NACA 67-025 to NACA 66-025 (70% to 60%), the COP is moved back to 30% of the length (IE, its now inside of the shape) __________________ Doing my part to reduce dependence on OIL Doing my part to reduce congestion And enjoying it! If you have to use your brakes, you are driving too fast!* My 101.5 MPG 2003 Kawasaki Ninja 250 Crude Oil Price Today Last edited by theycallmeebryan; 07-20-2009 at 03:44 PM..