What happens to the wind as it slips and twirls over your sail?

[jssailem]

I saw this Facebook video, and it was one of the simplest discussions of what is happening and how you might trim your sail to improve your boat performance.

83K views · 3.2K reactions | Your textbook got lift wrong. The air on top doesn’t “wait” for the air below. The classic story: air splits at the front of a wing, both halves must meet at the back, so the curved side has to go faster. They don’t meet. Smoke released in one row shows the air on the curved side reaching the back edge first, well ahead of the other half. And on a sail that story can’t even work: it’s a single layer of cloth, both sides are the same length. The curved, downwind side really is faster. Only the reason was wrong. Here’s the part that matters on the water: that fast air is fragile. 1. Sheet in too tight and it peels off the downwind side, just behind the luff 2. The downwind telltale twirls instead of streaming 3. Fix it: ease the sail out or head up, and the flow comes back 4. Upwind telltale lifting instead? The sail is too loose, or you’re too close to the wind Both telltales streaming = a sail that’s actually working. Save this for your next sail and send it to the friend who still trims “by feel”. ⛵ Get your international skipper licence: theory online from anywhere, year-round. Sailing practice in Barcelona, Athens, Mallorca or the Canaries. DM us or tap the link in bio. #sailing #sailssearch #sailingschool #barcelonasailing #yachting | SailsSearch

Your textbook got lift wrong. The air on top doesn’t “wait” for the air below. The classic story: air splits at the front of a wing, both halves must meet at the back, so the curved side has to go...

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[kappykaplan]

Interesting. Tks for sharing your find.