Aerodynamics for car/software

[SterlingPower]

Hello I am considering making a electric car based around the fiat turbina, or simalar aero shape CD 0.14. space frame chassis etc.

I have struggled to work out reliable aerodnamic properties for the car, and would like some help if possible.

Is trying to achive .14 CD frontal of 23 sq ft, 900 lbs weight inclusive of batteries, + 429 lbs px + 165 luggage (1500 lbs)
and wondered if these values were even remotely sensible. 10 hp is a very low requirement, with 3 people inside. estimated range is around 85 mph.

Sizing the motor and amps is also a bit of an issue, but that really isnt for this forum section I guess

thanks

Sterling Power

 

[IRstuff]

Seems like you're asking for about twice the energy efficiency of a Tesla. That seems a bit bold.

As for your drag target, it seems a bit sporty:

http://en.wikipedia.org/wiki/Automobile_drag_coefficient#Typical_drag_coefficients

TTFN
faq731-376

 

[GregLocock]

0.25 is moderately easy to get

0.20 is possible but requires great attention to detail and careful elimination of all turbulent flows through the interior and cooling system, and care with wheel fairings

0.15 is possible with a one-off if you can maintain laminar flow over the first 40% of the car, which means that it will be an impractical or at best unusual shape. No windscreen wipers, door mirrors, door handles, etc etc.

The Aptera guys had a good shot at this, I think they may have measured 0.15 on a real car.

FWIW we measured 0.07 on our solar car - with a smooth glass fibre shell rather than cells. The slight additional roughness from the cells brought it up to 0.12 or so, from memory. It was laminar to 60%.

You also have to be very careful with setting the pitch of the car so that it generates no lift.




Cheers

Greg Locock


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