So worst case, that gave you about an 8% improvement. That is pretty damn good. I earlier made the error of assuming the boattail was optimized and had the proper angle. Even still, this is very impressive.
Man, I wish I knew how to do metalwork. I'd gladly make the rear end of my Triumph GT6 tapered like that. Done right, it would enhance the car's aesthetic appeal, instead of detract from it.
It's a dream of mine to have the one of the most vulgar cars on the road, and for it to be ecologically sound relative to almost everything else out there.
If your Civic were an EV, it would do 150 miles range at 60 mph on 1,500 pounds of today's 25 Wh/kg sealed lead acid batteries.
Here are some photos of the current configuration of my car. Mods installed so far, listed from greatest of least effect on improving the coasting ability of my car: boattail, nosepiece, underbody panelling, grill block, front and rear whell well skirt, wheel spoilers, side spoilers, smooth hub caps, gap sealing.
I've had several people ask me if it was an electric car after an ICE-off coast into a parking lot. Others have asked me what all the stuff on the car was for. Only one person has asked me if the stuff on the car was to improve mileage. And I have had plenty of slowdowns and staring on the part of people passing me on the highway. One guy in a van passed, me, slowed way down so that I passed him, then he passed me, then about a mile up the road, he was parked on the side of the road and took pictures as I drove by.
Yes, I know you can't judge aero by looking at it... but unless that pointier nose is somehow directing more air away from a "dirty" undercarriage I don't see how it can be improving aero. Generally, as long as the airflow going around the front end remains attached along the sides the bluntness or pointyness of it doesn't really affect drag in the 0 degree yaw condition. In fact I wonder if the increases in "frontal area" due to the added length of nose and tail when the car is yawed serve to increase Cd in crosswinds?
Interesting points, something to consider is he has a smooth undercarriage on his eg already.
Wow, that boat tail is impressive. How did you build it?
The boattail is made of an aluminum bar (1/4"x1") frame bolted together (drilled and tapped) and covered with clear vinyl on top and coroplast on the bottom. This construction is quick to go together and requires only a few tools (drill, tap, hacksaw, box cutter, screwdriver).