Hatchback Vs. Sedan (why does a sedan have a better Cd?)

[E.Roy]

Looks like you're right on the length

Mazda reports length of 5-door at 175.6 but I couldnt find there length for the sedan. Motor trend has these dims:

LENGTH X WIDTH X HEIGHT 175.6-180.3 x 70.7 x 57.3 in

So it appears the sedan is 180.3" long, a whole 5" longer, which to me makes no sense. Why cut down the interior room on a hatch?

[aerohead]

I suppose you need to decide where you're going with the car.
If you're looking for limited length,choose the sedan.It will have great rear vision.Easy access to the trunk.Easy parking.
If you're thinking about remarkable drag reduction,go with the hatch for long term benefit.It is the better candidate for low drag through elongation.
In the long run,it's better idealized for the sectional density necessary for truly low drag.
There are no truly low drag notchback sedans.There never will be.

[Thenorm]

Originally Posted by aerohead

I suppose you need to decide where you're going with the car.
If you're looking for limited length,choose the sedan.It will have great rear vision.Easy access to the trunk.Easy parking.
If you're thinking about remarkable drag reduction,go with the hatch for long term benefit.It is the better candidate for low drag through elongation.
In the long run,it's better idealized for the sectional density necessary for truly low drag.
There are no truly low drag notchback sedans.There never will be.

do you mind if I summarize this a little clearer.

1. for good Cd with no modification, get the sedan
2. if you plan to add a kammback/boat tail for remarkable drag reduction get the hatch.

[Jasen]

Originally Posted by E.Roy

So it appears the sedan is 180.3" long, a whole 5" longer, which to me makes no sense. Why cut down the interior room on a hatch?

I don't think that's the case, the vehicles are different configurations. The sedan is probably longer to get some more trunk space, and or meet the design criteria.

[Xist]

Originally Posted by Thenorm

do you mind if I summarize this a little clearer.

1. for good Cd with no modification, get the sedan
2. if you plan to add a kammback/boat tail for remarkable drag reduction get the hatch.

As far as I know, only Christofoo and 2000Neon have made sedan kamm-backs, and Christofoo's is an ongoing project.

[kach22i]

Originally Posted by E.Roy

So it appears the sedan is 180.3" long, a whole 5" longer, which to me makes no sense. Why cut down the interior room on a hatch?

Length in this particular case is not an indicator of headroom - look at the pictures.

What I find as an interesting surprise, is that the hatchback has more rear headroom than the sedan.

I don't think this is typical unless comparing a sport coupe to a hatchback.

Should we be calling the version with a trunk a sport sedan?

Marketing, we just cannot escape it.

[aerohead]

Originally Posted by Thenorm

do you mind if I summarize this a little clearer.

1. for good Cd with no modification, get the sedan
2. if you plan to add a kammback/boat tail for remarkable drag reduction get the hatch.

*The sedan has been optimized as a sedan with no thought of modifications.
*The hatch was also not designed with mods in mind,but happens to have the perfect fundamental architecture if one wanted to do the ideal elongation.
*All the really low-drag vehicles which have been constructed were 'fastbacks',which followed the profile of a proper half-streamline body.
*If you continue the roofline and sides of the hatch,you're right on target for low drag.It's exactly like Kamm & Koenig Fachsenfeld's Cd 0.12 Kamm-back in it's embryonic stage.
*The Cd will just be a function of how far back you push the tail.
*K&K cut their tail off at 50% frontal area cross-section and got as low as Cd 0.23 with a 'practical' length in the late 1930s,early 40s.
Then Koenig-Fachsenfeld came up with the inflatable boat tail extension to push the Cd back down towards 0.12,for only open highway travel where length wasn't an issue.

[aerohead]

Originally Posted by kach22i

Length in this particular case is not an indicator of headroom - look at the pictures.

What I find as an interesting surprise, is that the hatchback has more rear headroom than the sedan.

I don't think this is typical unless comparing a sport coupe to a hatchback.

Should we be calling the version with a trunk a sport sedan?

Marketing, we just cannot escape it.

I think Mitsubishi is using 'Sport' with their Lancer which got the relaxed roofline compared to the original notchback roof folks were putting VGs on.
I think its become part of the vernacular now.

[sheepdog 44]

The VW XL1 and the GM EV1 are both "sedans," and have the lowest drag figures of any production car with Sub 0.19cd. The Mercedes CLA sedan (0.23-0.22cd) has a lower drag coefficient than the Prius (0.26-0.25cd) and Insight (0.25cd). Honestly with whats being done by automakers, I'm not all that impressed by the 1st gen Insight aerodynamics. 0.25cd will become the new common standard of an "average" cars drag coefficient. Anything below that number should be the only thing considered aerodynamic.

Sedan vs Hatchback? I think it's due to trunk height. A trunk can be lower to the ground so you can place things in it, and a lower decklid facilitates aerodynamics. A hatchbacks' roof needs to be higher so your not crouching. The spoiler on the Prius is higher than most trunk lids you'll find in a parking lot.

[t vago]

I've been thinking about putting a kammback on the Karen-mobile...