Is this to Extreme?

[Chris D.]

Looks like a kit car, I dig it! just dont go into steep driveways

[Greenblazer]

I am not an aerodynamic expert, but I agree that your tail is too long, and not sharp enough. The flat part in the rear is bad from an aerodynamic standpoint. I would suggest you follow the stock hatch line and curve the bottom up to meet it in a sharper point. Take a look at the Aptera's tail for some inspiration.

Later,

Allan Greenblazer

[JV-Tuga]

I trimmed your nose, rear and back roof (no more tall passengers) to what I believe to be a more reasonable shape that will still give you the benefit while allowing you to park better. I think it is more practical this way, even though you may not be squeezing every last drop of FE out of it.

[PaleMelanesian]

I think that tail ^ is a bit short / steep. You might get flow separation somewhere along the way. I'd go with something in between the two.

[ebacherville]

Yeah its the steepness of the tail that makes it so long.. the design I came up with was discussed by Areohead and Bajoos and I.. the profile i have there matches his profile but is extended to lessen the wake at the flat tail... less flat tail = less for a wake to form

[ebacherville]

Originally Posted by JV-Tuga

I trimmed your nose, rear and back roof (no more tall passengers) to what I believe to be a more reasonable shape that will still give you the benefit while allowing you to park better. I think it is more practical this way, even though you may not be squeezing every last drop of FE out of it.

practicality isn't a major concern, the nose thats already built as shown and on the car has not given me any problems with parking or entering driveways ect.

My main goal is if I'm going to go through the effort to make a tail it might as well be the best I can make... no compromises.

[ttoyoda]

My main goal is if I'm going to go through the effort to make a tail it might as well be the best I can make... no compromises.

In that case copy the tail of the m-111 record car. Put casters under it. They probably had *some* idea what they were doing, and they did not cut corners to save money, they made this car for prestige.
Just be aware the car may tend to turn into crosswinds on the road.

[ebacherville]

Originally Posted by Greenblazer

I am not an aerodynamic expert, but I agree that your tail is too long, and not sharp enough. The flat part in the rear is bad from an aerodynamic standpoint. I would suggest you follow the stock hatch line and curve the bottom up to meet it in a sharper point. Take a look at the Aptera's tail for some inspiration.

Later,

Allan Greenblazer

The stock hatch line is to fast (steep) the air seperates from it.. no sence in making any tail for it then.. I would gain nothing

[ebacherville]

Originally Posted by ttoyoda

My main goal is if I'm going to go through the effort to make a tail it might as well be the best I can make... no compromises.

In that case copy the tail of the m-111 record car. Put casters under it. They probably had *some* idea what they were doing, and they did not cut corners to save money, they made this car for prestige.
Just be aware the car may tend to turn into crosswinds on the road.

yeah.. that may be bad.... I however am not running at 100+ mph like the 111.. no need for a shark fin on the back..

[ttoyoda]

For computational fluid dynamics modeling :
http://www.fluent.com/solutions/automotive/aero.htm
Big money unless you get it free at school. Not the eaisest to learn. Pitfalls for the unskeptical, i.e. you make an error in setting up the model or test conditions (true for any modeling software) you might get wrong answers and not realize it. I used to use it years ago, to model air flow thru heat sinks and air distribution ducts, and it was easy to spend weeks making models, running the simulation, interpreting the results. In the end, the PCB layout guys put components where THEY wanted, and we would make ducts and heatsinks so the product would not catch fire.
If you have no training in modeling with it, it will take you less time and you will have more fun just making the real thing. If you have the software free and someone can show you how to use it, then make models.