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Originally Posted by freebeard
The air curtain is a convergent nozzle. The inlet could be any shape, but the outlet is a tall narrow slot. It might be very narrow, a fraction of an inch. Here's a research picture of a Coanda nozzle—the profile may be similar:
You could get a low-tech peek at the performance on a freeway in the rain. I'm always watching other cars front wheelwells there, but I haven't seen one of these BMWs. |
I'm glad I'm not the only one who watches wheelwells in the rain
I had to look up what exactly is the Coanda nozzle and the Coanda effect. From what I can glean, the air coming in would be trapped inside the wheelwell similar to a parachute. Having the narrow slot for the incoming air to escape would allow it to "reattach" smoothly to the body of the car, thereby decreasing drag. Correct?
I will design the Coanda effect to work in conjunction with front skirts.
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If you increase the offset of the front wheels, you're working against yourself when it comes to making the front skirts. Lowering will compensate for the reduced track in cornering.
Magnet hold and then let go completely. Bungee cords will release and then increase tension.
I propose a four-bar arrangement for the front skirt. Nobodies made one yet.
You have to imagine the pivots into place, until I make a better drawing. They could be done in 1/4" steel rod and follow the contour of the wheelwell. The two top bars are connected together so that any tendency to rock front to back is damped. Or it could be clamped in the center and be a torsion springs to hold it closed.
You want the front skirts to be bubbles, so you can turn the wheels a bit without invoking the skirt. But it's there for sharp low-speed turns and parking.
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Increasing offset means that the wheels are tucked closer to the body. +25 mm offset would tuck the tire assembly closer inside, -25 would stick waayyy out! The spare rims have the "tuck" needed, and are thin enough for a 165 width tire.
I wanted to use magnets because they were different. Springs and bungee cords would work better, and they have been proven.
I personally think your 4-bar arrangement with a torsion spring is great! I will figure out someway to implement it onto my car. I wish I had access to your software, I only have Paint. I would like to avoid bubble skirts as much as possible. I will have them if the tire is not as inset as I am planning. Avoiding an increase in frontal area is a concern of mine.
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Your side view looks reasonable. Extending the nose isn't really necessary unless you are going 250 mph and entering tunnels.Keep in mind the 3D view. Here's a VW Beetle in the aeroform:
There are thing that don't show up in side-view.
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Like I said earlier, I would LOVE to have your software. The real world plan is to minimize sharp angles and to make the boattail as close to a semicircle shape as possible while coming to a point, as in your Bug schematic.
Would having a shorter nose with a steeper angle encourage more air up and over the car? That is what I am after. Basjoos said that he added the nose so less air would flow underneath his car. Is he right, or no?