Looking at https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html it doesn't look like it's true that it'

Looking at https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html it doesn't look like it's true that it's air being deflected that causes lift. There was a recent submission on HN explaining the theories of lift in sails: https://news.ycombinator.com/item?id=13829625 https://news.ycombinator.com/item?id=13829625. AFAIU air is not dense enough to make this deflection account for the magnitude of lift forces actually observed.