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Originally Posted by MetroMPG
Good explanation, thanks.
I also basically guessed at side angle. I arbitrarily chose 10 degrees, and then eyeballed it by holding up a cardboard triangle with a 10 degree angle while laying out the strings.
One interesting result of my imprecise construction techniques that resulted in the boat tail being skewed somewhat to the passenger side: I've effectively tuft tested two different side angles. I haven't measured them yet, but will this week and will report back.
FYI, I measured the bottom angle: it's 4 degrees from the undertray to about a quarter of the way along the length of the boat tail, where it transitions to 7 degrees. And we saw from the tufts that it had attached flow to the end.
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I seems like the underside has got to be compromised so it doesn't get scrubbed off at the first driveway.
At the GM exhibit in Epcot Center,their Citation concept car had an articulated active rear valence/diffuser panel which lowered for highway travel.I've envisioned something like this with a simple cable-pull and latch.
Looking at your numbers,if you were starting around Cd 0.30 before the tail,then the 15% mpg improvement would have you in Cd 0.21 territory
Basjoos-style movable front skirts would knock 9%( based on original Cd ) off.Full rear skirts maybe a few ticks more.
You're so close to sub-0.2 I can smell it! Thanks for doing all that,the meticulous records,video,ad infinitum............. "And the trophy goes to......"