Tuesday, March 27, 2012

To Make a Jelly Bean Fly.....

The iMiEV may look smooth, but with a Cd of 0.35,  it ain't exactly streamlined.  That round rear is not optimized for aerodynamic drag, and the slotted wheels aren't necessary when there's such little braking heat to dissipate, due to strong regenerative braking.  So, the DIY community has long cooked up little modifications like salt flat discs, fender skirts, air dams, belly pans, duckbills, rear visors, and even boat tails!  Here's a rendering of what some of those mods might look like on an i.  Here's also a link to a Dutchman who made the best DIY removeable boattail that I've seen. 
This quickie drawing shows what an iMiEV might look like with disc wheel covers, rear fender skirts, and two different options on the rear.  In black, I echoed the rear passenger window profile.  This could be done nicely in black lexan, and be semi-permanently affixed to the hatch.  A sharp rear edge would make better aero, but for the sake of buildability and artistic license, I chose a curve. 

In grey is the outline of a possible Kammback boat tail.  For you sailors, you'll recognize the concept of 'waterlining'.  Stretch out the same or even a bit more mass into a longer, more streamlined shape, and you'll reduce drag.  This one follows the rear body curves as closely as practical without actually touching, and has a sharp rear cutoff as dictated by good old Mr. Kamm

Here's a graphic of one of the few spoilers scientifically designed for drag reduction rather than downforce.  Too bad they're not commercially produced.  Time to start whittling!

And the Texas Mile winner in October 2011 chose a simple duckbill for drag reduction rather than a downforce spoiler.  If a high po Corvette doesn't lift at 245 mph, d'y'all rice boys really think that a wing's gonna help your Civic

So, the easiest among the above winners would be to simply add discs to the rims.  I went a notch up from JC Whitney's offering, but not quit Mooneyes pricing, and got the Taiwanese-made CCi brand, and am very pleased with the heavy gauge metal (yeah, adds a bit of rotating mass but doesn't dent when I push 'em on), excellent finishing, and positive lock on the wheel..  Still don't know how difficult they will be to remove, but I've got the right nylon pry tools. 
I'm thinkin it looks EVen better at night.



Maybe you can work with some sort of roof spoiler that attaches to the rear hatch to lessen your cd.

Air Intake Kits said...

The car is designed superbly. The benefits will surely be seen significantly during driving.