Beating the Breeze

click for larger view

 

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. :-)

About these ads

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)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s