If you ask me, I think it's ****ing pathetic that it took a mainstream auto maker 80 years to beat this drag coefficient in a production car. The Honda Insight had a .25. We could have done aerodynamic cars in the 1970s fuel crisis, kept the snarling V8s in them, and gotten well in excess of 30 mpg for our auto fleet.
But every time consumers demand fuel economy, the auto industry instead sees it fit to punish them with crappy econoboxes that possess anemic powerplants, refusing to address aerodynamics in any meaningful way. Then they blame Ralph Nader and the Japanese automakers, while asking for big nanny government to give them another welfare handout.
Extremely impressive. Unfortunately my post just got eaten.
With the exception of the wheels and axles, extremely streamlined. If the body was lowered slightly so that the axles were inside the car, I bet it would beat the rumpler significantly.
I did some calculations about the drag. Knowing that the power in this vehicle is the same as a model T, and power consumed by drag is proportional to velocity cubed, that means that CdA is going to be around 26% of what it was in the model T. (45/70)^3 = 3.76 And probably less, considering that rolling resistance will be increasing with the square of velocity as well.
Just to remind you what an ugly brick of a car the model T was, here is a picture:
Not surprising he was able to do that with half the A and half the Cd. I don't think engineers back then fully realized the drag that wheels generate by virtue of dragging air with them as they rotate. I suspect that on the homebuilt car above, wheel and axle drag would be easily half the total drag on the car (assuming no crosswinds of course.)
I've been discussing some of these issues here, at a homebuilt airplane forum. Looks like we are going to have to do this ourselves. For some reason people are willing to make compromises when it comes to air transport that they will not do to minimize fuel economy.
With induced drag being taken care of by LRR tyres, it seems ridiculous that we can't have highly aerodynamic personal transport that completely minimizes our running expenses.
In a lot of ways I wish we could return to an era similar to the 1930s and before. In many different areas, the only things that have improved in a design is the marketing. Why build something better if we can saturate the TV with our programming until people believe that it's better, without doing anything differently? And now the auto companies have legislated their competition out of the market, with various front groups clamoring for our safety but in actual fact only serving to increase barriers to entry.