Most aerodynamic cargo box?

[winkosmosis]

Originally Posted by Frank Lee

If I was to stick to Basjoos' parameters and have one for the roof, I'd try to find out just how small the vertical height could be while still being functional, and spread the width out to the drip rails (or door gaps) on each side, and put a generous amount of tumblehome on the sides. I think the front would be the least influential of all the surfaces of the box but nonetheless either have it extend the curve and slope of the windshield, or heck make it square but have generous radii on the side and top edges. Let the back of the box follow the template down to a point.

The front end would be more important than if it was a free flying object, because of the higher speed airflow coming off the windshield and hood

[Frank Lee]

That doesn't change the radius equation does it?

[ChazInMT]

Originally Posted by winkosmosis

They're not mounted backward. The big end is flat, not aerodynamic in any way. Air would hit that surface and spill out to the sides, effectively making a much bigger frontal area.

Ya know, for someone who's been around a while you still aren't getting it. Believe what you want about the front end needing to be not flat, fact is, the air creates its own aero shape in the front. In the back of a shape, the air gets really stupid and needs much help. Intuition tells us the air gets "spilled out", fact is, it does not. Granted, an aero front end does help some, but not as much as the back. I'd say it's a 20/80 split at best, 20% front and 80% back as far as how much you can improve the aerodynamics of something by improving its shape.

We aren't saying the carriers would be optimal by reversing them, only better, because that nice aero taper on the "Front" would bring the air back together much more efficiently, if reversed, than the big wide flat back it has now.

I made a simple drawing to illustrate what I mean.

[winkosmosis]

Originally Posted by ChazInMT

Ya know, for someone who's been around a while you still aren't getting it. Believe what you want about the front end needing to be not flat, fact is, the air creates its own aero shape in the front. In the back of a shape, the air gets really stupid and needs much help. Intuition tells us the air gets "spilled out", fact is, it does not. Granted, an aero front end does help some, but not as much as the back. I'd say it's a 20/80 split at best, 20% front and 80% back as far as how much you can improve the aerodynamics of something by improving its shape.

We aren't saying the carriers would be optimal by reversing them, only better, because that nice aero taper on the "Front" would bring the air back together much more efficiently, if reversed, than the big wide flat back it has now.
I made a simple drawing to illustrate what I mean.

Did you not look at the picture? The edges aren't even radiused. The back end is flat, with sharp edges, and an angle that would trap air like a parachute.

If your "what air is really doing" diagram was true, then there would be no benefit to radiusing corners. And a slant-back Hummer would have the Cd of a Prius. Nasa's aero truck with the big radius panels and trailer fairing wouldn't be any more aerodynamic than a regular truck.





Apply some common sense instead of just parroting things you read without understanding.

[winkosmosis]

What's more, if you turn one of those backwards, the sharp downward curve would probably experience turbulent flow separation

[ChazInMT]

Yeah, OK. You go focus on the front end of things then, see how that works for you. I say the car carriers will work better going the other way as do most people in here. I guess we have all just drank up too much of the Koolaid.

I would go into more detail as to where it seems you are confused about things, but the tone of your posts is not conducive to me wanting to help you out. Figure it out on your own.

[winkosmosis]

Originally Posted by ChazInMT

Yeah, OK. You go focus on the front end of things then, see how that works for you. I say the car carriers will work better going the other way as do most people in here. I guess we have all just drank up too much of the Koolaid.

I would go into more detail as to where it seems you are confused about things, but the tone of your posts is not conducive to me wanting to help you out. Figure it out on your own.

You're still not applying common sense, just parroting tropes. "Front end doesn't matter, front end doesn't matter, squawwwk!!!"


Your diagrams are WRONG. Period. You really think you're smarter than NASA and that a Hummer is aerodynamic even with its sharp corners, because air is magic and forms the most aerodynamic shape, allowing nice smooth transition to the sides of the body?

Maybe you should call up all the truck manufacturers and tell them that they don't need air deflectors because "what the air is doing" is forming the exact same aero shape through the force of magic! Oh and don't forget to say "Front end doesn't matter, front end doesn't matter, squaaawwk SQUAAWWKKKK!"

[PaleMelanesian]

Originally Posted by euromodder

If you need to streamline a brick, add a fairing on the rear ...
Counter-intuitive, but that's how it is.

There you go :

Airflow is going from left to right, BTW

.

[PaleMelanesian]

Originally Posted by aerohead

"Wind-tunnel studies have shown repeatedly that the trailing surfaces of the greenhouse are far and away the most crucial details of a low-drag car design.The ideal is always the same:the perfect teardrop shape....."
Don Sherman, "Going with the Wind",CAR and DRIVER,August,1984

http://me.dyu.edu.tw/lecture/Vehicle_%20Design(2).pdf - Page 27

Component - Drag coefficient
Forebody - 0.05
Afterbody - 0.14
Underbody - 0.06
Skin friction - 0.025

[aerohead]

Is Flow-Illustrator sophisticated enough to handle a 'stacked' image of one form over,but not touching the form below.
Perhaps we could actually investigate what the centerline flow would look like for these car top carriers.
Empty ski racks pushed a VW Scirocco Cd from 0.43,to Cd 0.55.Perhaps the 'backwards' racks of today are an improvement.
We could check?