What is more aerodynamic: a wider body or bulging fenders/fender flares?

[Big time]

Let's suppose you are designing an streamlined car from scratch.
The car has a wide track and a narrow cabin.

What is more aerodynamic:
A car with bulging fenders or fender flares.
i.e. to cover the width difference between the wide wheel outer edges and the narrow body for example measured at the doors.

Or a car with a wider body. Where its body width (measured at the doors) is as wide as the wheel outer edges?

[drmiller100]

Originally Posted by Big time

Let's suppose you are designing an streamlined car from scratch.
The car has a wide track and a narrow cabin.

It turns out I am indeed designing a streamlined car from scratch.

It has a narrow track.

[BackroadBomber]

^^^ lol

[ChazInMT]

Hmm, lets see what VW did with their state of the art XL1.



I think this is your answer.

[Frank Lee]

VW certainly had opportunity to "coke-bottle" that if they wanted to.

[CigaR007]

Originally Posted by Frank Lee

VW certainly had opportunity to "coke-bottle" that if they wanted to.

Indeed, which is why I prefer the previous version.

[BHarvey]

Originally Posted by CigaR007

Indeed, which is why I prefer the previous version.

That's the one I prefer also. Would love to have it!

[aerohead]

The lowest drag cars have fully enclosed wheels.AEROCIVIC would be a contemporary example.

[3-Wheeler]

Originally Posted by aerohead

The lowest drag cars have fully enclosed wheels.AEROCIVIC would be a contemporary example.

Hi Aerohead,

OK, I am going to ask a nit-picky question here....

So a car with wide spaced wheels and thus covered with an appropriately wide body will, for it's resultant frontal area, have a lower Cd.

So far so good.

However, the counter response to this is....

Make an appropriately sized 1) "cigar-shaped-fuselage" and cover the vehicle occupant, and 2) make proper sized airfoils for the appendages hanging outside the main fuselage, such as wishbone suspension members and wheels/tires.

I would think that this second vehicle, while having a higher Cd overall, would also possess a lower frontal area, and thus come away with an overall lower aero drag component than the "one-piece-body" shape.

Now my "discussion" above makes the assumption that this "body shape" is optimized for a single occupant, who is also the driver of the vehicle. I am not talking about the "new" VW 1L that has side-by-side seating and thus forces a wider body shape to the wind.

The width of the cigar body is, let's see, about 27 inches wide.... I had to measure the one that's in the basement right now....

I simply can not imagine how a car with a track width of let's say 60 inches, and a body that also is wide enough to cover this same width, and has a Cd of let's say 0.10 is going to ultimately have a lower overall drag component than a cigar shaped body with width of 27 inches and all external appendages covered with airfoils, with a Cd of let's say 0.15??

It may be that our responses to the main question above need to be qualified a little better to avoid over-simplifying the answer.

Just my opinion.

Jim.

[jime57]

Well I don't really know the answer, but I'd like to point out a couple of things by way of example:
1. The VW L1 had tandem seating for two, I think, and it used a complete body out over the wheels.
2. The VW XL1 had side by side seating and also had complete body out over the wheels.
3. The Aptera had side by side seating and had separate fender fairings, apparently to cut down on the A part of CdA.

There is clearly a difference of opinion among designers who are or were trying to achieve the "ultimate."

I think 3 wheeler asks some interesting questions. Should be an interesting discussion.