I think I have sailed on that same lake, Lake Constance, with Andi Lutz on his F18HT, from the Swiss side. They race late in the afternoons on weeknights. When I first arrived there was NO WIND on the lake, yet there were many cats rigging up at about 5pm. I'm thinking to myself, "What are they wasting their time for? We can't sail in this, it's DEAD out there!"

When I asked Andi about the lack of wind, he said, "Just wait, it will come." And sure enough about 6pm, it slowly starts to blow, very light at first, but steadily increasing to about 8-10 as it got later. We had a great time racing!

Andi said in the summer, the heated air is rising up the side of the snow capped mountains during mid day, but as soon as the sun gets low, the air right over the snow cools and sinks quickly, and it comes rushing down the mountains and across the lake, creating the good wind after 6pm!

They have a name for it of course, but I can't remember it. I guess the mast in that video is high enough up to grab the wind before it sinks all the way to the surface, leaving a nice, clean, glass-like look to the lake as they scoot around at 14 knots!