A Physics Professor Bet Me $10,000 I'm Wrong

I doubt this is how sailboats are doing it (if they're doing it) but one way is (I think) to make the airfoil itself cut across the wind while the "boat" goes straight downwind. See these videos: link ▶ this video

Derek from the YouTube channel Veritasium made two interesting videos about this vehicle. link ▶ this video They go into some nice detail about why the physics works out the way it does.

Dead fish swimming upstream .. Reminds me a bit of this: a wind-powered vehicle than can accelerate directly into the wind... ▶ this video

The professor's reasoning is near the start of the video about the bet [1]. Basically they thought the makers of blackbird were fooling themselves (e.g. measuring slower wind at the bottom of the car vs the top of the propeller, or getting pushed above the average wind speed by gusts then selectively reporting). 1: ▶ this video

The original Veritasium video link The video of the bet and the further explanations - ▶ this video -- at 13:28 is an example without aerodynamics.

The small demonstration that made it click for me is from that video: ▶ this video This is exactly what the blackbird does, only with a propeller pushing air in place of the big wheel, and it's a much clearer and simpler demonstration of the same idea, which you can trivially verify.

The most surprising thing here is that someone on Twitter made a bet, lost the bet, and then actually paid said bet. Playing devil's advocate here a little: The whole machine is very counter-intuitive, and I can see how I myself may disbelieve it if not for the irrefutable demonstration(s)[0]. [0] ▶ this video

Original video triggering the bet for context: link Video discussing the bet and going over criticism: ▶ this video Veritasium is a great YouTube channel.