Quote:
Originally Posted by mpg_numbers_guy
I know there have been myriads of threads related to kammbacks and boattails for hatchbacks, but how about sedans? Could a partial boattail or kammback be implemented on a sedan as well, and would it have the same FE benefit? I'm considering doing a kammback on my Civic sedan and was wondering about the following templates (color code interpretations below the images):
The white indicates the kammback and the black indicates a possible partial boattail.
The blue and green indicate the pieces for the kammback, and the purple and red indicate the pieces for the lower part of the partial boattail.
Any thoughts on this? Location, possible FE gains, durability (coroplast w/ zipties, tape, and clamps)?
I know it would be better if the sides extended to the outside, but this would require taping to the exterior paint, and I'd rather not risk the car's paint job. I might have to relocate the license plate as well so it remains visible.
Any tips/suggestions welcome! Or if it's just a bad idea just let me know!  |
The Kamm-back car is based upon a 1/2-streamline body of revolution.These bodies cannot produce separated flow due to their perfect sectional density.Drag coefficient is simply a function of body elongation.
The notchback car is a mutilation of the ideal form and technically,is 'challenged',as far as drag goes,and will not (cannot) react to boat-tailing as will a K-form.
It is true,that up to a point,the notchback can have little penalty as far as drag goes,compared to the same car with a K-form greenhouse,but after that,you'd need the K-form to get the drag lower.
It may have been MetroMPG who modified a Honda similar to your's with a K-form addition,only to see no real drag reduction after all his effort.
You might want to select a Cd target,then inspect vehicles(especially Honda's) which already meet that target,and see if your car might benefit from some of their features.
Research by Audi,on their Audi-100 III demonstrated 'saturation' points for specific mods,whereas some part would respond positively to a certain alteration,after which,no additional shape change could produce additional benefit.This is exactly what 'optimization' is all about.
There are production Honda's of Cd 0.27,and Honda concepts of Cd 0.20.Honda solar racers as low as Cd 0.10.