Chalo said:
The angle of attack on their "airfoil" looks to me like it wouldn't create any lift at all.
HUH???? Name one thing about it that doesn't look it's intended to be a flying car? (Take this 'Enough Rope' while I catch my breath.) Why did you say "Airfoil" if you didn't think it was generating lift? Wouldn't you have said "Diffuser?"
For what it's worth, downforce results in drag plus additional rolling resistance, wake turbulence, and other efficiency losses. The most efficient way to go is to generate neither lift nor downforce, and move slowly enough that downforce-enhanced traction is not a safety requirement.
Oh, well, maybe it won't be necessary for you to explain anything, that last part spoke volumes.
Wasting a lot of energy to increase safety because you're moving dangerously fast is stupid. Just slow down and stop being stupid.
I'd say I'm a dilettante in the area of aerodynamics, but then we'd have a big discussion of what 'Dilettante' means, beyond that I know some from racing and from aviation. The fact is I'm often in discussions with instant experts where I don't want to play expert myself but I'm obviously so far out front of someone who speaks so boldly with no knowledge. Dangerously fast in the Aptera is 25mph, that's not counting whether there's any crash safety in the design, which I doubt because the 3 wheel design lets them off the hook for any. The aerodynamic design increases its' function as the car goes faster, at freeway speed all cars have aerodynamics hard at work. The classic example is that you hold your hand out the window on the freeway and you'll see how much lift or downforce can be at work. The body IS generating grip, it's just a question of how much. There would be no DRAFTING at freeway speeds if there wasn't.
When an average-size car travels down the freeway, it uses tremendous amounts of energy to displace air. At 70 miles (110 kilometers) per hour, as much as 65 percent of fuel use goes to overcoming air resistance.
-Lawrence Livermore National Laboratory
https://www.llnl.gov/str/May03/pdfs/05_03.pdf#page=26
A really spot on link would have been short and talked of countering other forces with downforce, but they're never around when I need them.
(And we have to go freeway speeds to get anywhere. If going half that was practical the cheap electric scooters would be a much easier sell.)
Back in the 1970's the racing world had the 'Flying Club.' If your car, for no apparent reason, left the ground and flipped or did other silly things you were a member. Many of the well known names of the time had the experience. A friend of my Father's died that way in testing, as did Bruce McLaren a few years later. The 70's had been a time where the aerodynamics were in fast forward, the wind tunnel had come into use in car design. They thought this was how racecars should and would look.
Computer simulation changed aerodynamic design dramatically. A lot of experts had "Looks to me. . . ." statements in print that came back to haunt them.
Oh, the Cessna 172 Skyhawk is designed to takeoff and climb out at 75 knots, but when you learn to fly in one they teach you how to get it in the air at under 50 knots, just in case you ever need to. Under 50 knots that particular plane cannot stay in the air, you fly over the numbers on approach at 63 knots and you're descending around 700 feet per second for sheer lack of lift. once your wing is less than it's own span from the ground the lift increases due to ground effect so you sort of level off, as you slow under 50 knots it'll settle to the runway. You don't force it down without an emergency, or even in one if you can avoid it. But you can force it into the air at 50 knots if you have to. Isn't Bernoulli interesting. . . .