Hi Matt,
You are correct that one of the biggest reason for the "final" Bionic car having a Cd 0.19 is the larger rear/lack of major taper; but it is not the only thing. The wheel openings, the engine cooling, the higher stagnant point, and probably a less complete belly pan also contributed to the increase.
The current frontal area of the CarBŒN is a bit under 25 sq. ft. and the current trailing face is under 10 sq. ft.
My goals are many: I want CarBŒN to be an open source project, and I have shared the model and drawings with at least 5 people so far. This is important -- I do not want the process of designing an uber-efficient car to be locked up, and if I am not able to ever build it, and/or I fail to "commercialize" it, I don't want the effort already invested to go to waste. If others want to build/produce it, then great! As long as they contribute back what they have learned/fixed/designed, then that is the biggest thing I hope to accomplish.
I want to be in the same ballpark as where we anticipate the Edison2 VLCe will be: they are estimating their weight with a ~15kWh pack to be ~1,200-1,300 pounds. I think that they could be even lower than that, since their 4 seat VLC is just over 700 pounds with the ~100 pound Yamaha engine. Trade that 100 pounds for the electric motor and gearbox, and then add the battery pack, and they could be as low as 1,000 pounds with a small 12-16kWh pack.
I hope to (eventually) have a big battery pack in CarBŒN -- in the same league as the Illuminati Seven, with it's 52kWh pack (which is the same as the Tesla, as well). I'm hoping to find out from them how much their pack weighs and how big it is. I have also asked FVT for the dimensions and weight of their EiG batteries; which are prismatic, and as such have a much better chance of fitting in the floor of the CarBŒN as I've shown in the latest drawing.
As far as the frontal area goes, that is a complicated question. As you may have noticed, the frontal area of the CarBŒN (and the Mercedes B/B car) are roughly square-ish. This provides a larger volume, and therefore a more usable interior volume, for the same frontal area.
Stated another way, if I lower the roof and widen the car, and end up with the same ~25 sq ft frontal area, then interior of the car would be far smaller, and much less useful, and there is probably no way to get 5 people seated in there; let alone as comfortably as I think the current CarBŒN design does.
If I am going to build the CarBŒN myself, without any/much sponsorship then it has to be fairly low cost. I know that the Illuminati Seven cost ~$120,000 to build, and I think that about $15,000 of that was for the battery pack. I certainly hope it will be much lower cost, because I certainly cannot afford $120K. Sweat equity is where it's at!
I do need to rewrite/update my blog entry on the CarBŒN, but please refer to it for additional details, about why I am planning on the articulated wheel skirts, the rear entry hatch/doors, the surrounding safety structure, the slim and light and cool mesh seats, the video mirrors, the position of the battery pack and drive motor(s), the air ventilation intake and exhaust, the structural and insulation considerations... the list of design considerations is very long:
Neil Blanchard Designs: CarB?N Concept EV: An Open Source Project
I need to establish a place to start building the chassis -- my 1 car garage is full of *stuff* and it needs repairs and upgrades. My neighbor who is a cabinet and furniture maker has a quite large bandsaw -- that is not currently working.
I either need to help him fix it, ot buy my own (used) bandsaw. I think it is inevitable that I will cut the male ribs to form the outside shell, and these will also have the female interior cabin walls at the same time. The first CarBŒN will have those plywood ribs largely left in place in the finished car; I don't really think I can take on making "production" molds first...