Why aren't roof boxes put on the other way round?

josip

Most people are familiar with the wedge profile of roof boxes on the roofs of cars. Thin at the front, thick at the back.
But the wedge isn't a very aerodynamic shape because the air doesn't flow nicely off the back.
The teardrop is the most efficient shape which is the shape used by "aero" roof bars.

https://roofracks.co.uk/Thule-Products/Roof-Bar-Products/960-961-962-963-969-Wing-Bar/

So why aren't roof boxes also put on the same way?

xabi

Good question, not sure aerodynamics comes into it when they are designing these things. And anyway, most people with no interest/experience in aerodynamics would think the pointy end should be at the front.

xabi

LIGHTNING wrote: »

Internal volume space would probably be the reason. Also more difficult to construct.

But even putting one on backwards would probably make it more aerodynamic.

challengemaster

I remember this being tested a few years ago - Can't remember where though. But you're right - it was way more fuel efficient to fit roof boxes "backwards"

pippip

I think the example is a bit flawed as that assumes the roofbox would be floating through air with nothing underneath it. Airflow would be considerably different when you factor in a car.

ThisRegard

LIGHTNING wrote: »

In the OP's example they posted a link to an airfoil, its not just a case of turning existing boxes around. You have to make sure the airflow's correctly under and over the box and make sure you are not going to affect the cars handling.

And the problem is that the roofline of cars are all different, so you'd have to build in some sort of levelling system so the box can be adjusted to this. When the roof box is on my car it's like I'm about to launch it into space, on my wifes it would be nice and flat.

josip

Yep, I was thinking that the roofbox and car would be considered as a composite structure but that would assume that each installer/owner fitted it in the recommended position for each car and each car would need to have a recommended position for each major type of roof box for each model.

Which is a big ask considering that the guy who originally fitted the roof box on our car didn't even fit it square to the roof bars but at a noticeable angle.

grogi

Because the curvature of the windshield already does the job of reflecting the frontal wind. The box just follows the shape of it.

I am also not convinced the "aero" roof bars are designed to minimise the drag. More to minimise the noise...

josip

grogi wrote: »

I am also not convinced the "aero" roof bars are designed to minimise the drag. More to minimise the noise...

Is noise not caused by turbulent air (effectively drag) ?

grogi

josip wrote: »

Is noise not caused by turbulent air (effectively drag) ?

You might have much more drag without any noise