Beating the Breeze

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On warm summer evenings at most yacht clubs, you’ll often find small groups of sailors furtively clustered around tables arguing the practical physics of various wind-powered boats.

What’s the optimal sail shape, sheet angle, and ‘wetted surface’
for a given race boat and rig under particular weather conditions?

Long after the sun sets and an impressive collection of empty drink glasses has accumulated on the table, a number of predictable “Holy Grail Sailing Questions” usually come up. Here’s a common one:

Can you really tune that boat’s rig and foils
to sail faster than Real Wind? 🙂

If you dig back far enough in the history of SLSailing here, you’ll find long discussions and more than a few in-world sailing skills classroom talks by M1sha Dallin, Hans Zinnemann, Owen Oyen and others on sailing physics. They made a much-appreciated attempt to help digital sailors understand basic principles, and how they might be realistically translated into a digital sailing emulation online.

The jump from a RL breeze-driven dinghy to a set of equations in a vehicle force algorithm is, well… not too straight forward. 🙂

I’m bringing this issue up just to highlight a year-old, nicely written blog post by Terrance Tao on the RL physics of “Sailing into the wind, or faster than the wind.” For a pretty inscrutable topic with a numbers-laden discussion, it’s impressive that TT’s post prompted 41 thoughtful comments. 🙂

If you are interested in RL sail physics or simulation algorithms, you might go visit terrytao‘s blog.

On the other hand… if I ever post another link here about a dry mathematics discussion blog… you have my permission to come over and just shoot me. 🙂

2 responses to “Beating the Breeze

  1. I won’t shoot 😉 Interesting stuff, got my head spinning until I had a coffee. Then I thought… that dude needs a touch of realism, cause he is trippin… I hope someone invites him for a real sailboat trip. Unlimited speed in a sailboat. Yeah, right, – and I have a spaceship parked in central Copenhagen. U have all seen it. It is disguised as the Little Mermaid. Ok, so sometimes theory is different from real life. Maybe the Moth is closing in on theory, I dunno 🙂

  2. Thats a nice seperation of force components to explain whats going on with a boat (or glider, or as a commenter mentioned a solar sail).
    It makes some pretty big assumptions so you can see how an iceboat or a catamaran would operate closer to that ideal than a displacement hull (Assuming you can get lift from the enclosing medium – water in our case- but not drag is sorta difficult to apply real-world)

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