Thursday, June 14, 2012

It's Not a Sail, It's a Wing

As a complete aside, we had a California Sea Lion in the marina yesterday. I didn't think they ever came into the marina. Clearly I was wrong. These are HUGE animals. Males can be up to 350lbs. Females range up to 220lbs. These guys can be aggressive. Sail too close and you'll have several hundred pounds of pissed off sea mammal sharing your boat with you. It won't be a good thing. WA State law requires us to stay at least 100 feet away from them. The sea lions usually hang out on the rocks and the mooring bouys outside of the marina - there's really nothing inside to interest them. The fish are too small. So I can only assume that the single sea lion who ventured down our waterway yesterday was merely sightseeing. And fussing at those of us gaping at him from the dock.

Let's get to sailing. The picture above is of a sailing sloop sailing into the wind - reasonably close hauled to the wind, too. He's on a port tack, flying a jib, so there's probably a good solid wind blowing. The boat's heeled, but not too much, and there's no lough visible in the sails, so this boat is sailing efficiently.

What did I just say? What does it mean and how the heck can I tell?

Sails function a bit like a bird's wing or an airplane wing. If you stick your hand out of the car window, you can make it ride up or down based on the tilt of your palm. Sails are the same - except they're horizontal. The sails force the wind to change direction. Energy is transferred to the sails and the boat is pulled through the water. That's right - pulled. The only time a boat is pushed is when it is sailing downwind. Sailing downwind, the boat cannot exceed the speed of the wind. Tacking, or sailing into the wind, where your sails are actually pulling you, the boat can go faster than the speed of the wind - though, really, there are a number of practical limits on that. Let's just say that five to six knots is very good speed for a 30-35 foot sailboat.

Sailboats require wind. No wind, no go. The smaller and lighter the boat, the less wind it requires. The smaller and lighter the boat, the less wind it can safely handle. Wind comes from a specific direction, which depending on your location, may change through the day. In the Pacific Northwest, our prevailing wind patterns blow from the south (which equals rain) or from the north (which usually means fair weather). If you're writing about sailboats, you'll want to know a bit about usual wind patterns for the region you're writing about. Weather Underground produces a very good marine forecast that gives you wind and wave information for just about anywhere.

For our purposes, assume our wind is from the north at 15 knots (about 17mph). No sailboat on earth will be able to sail directly into that wind. Sails must be at an angle to the wind in order to fill with wind and produce motion. Sort of like when you have your hand out the window of the car and hold it flat. It isn't until you tilt your hand that the wind forces it up or down. In a boat, heading into the wind just makes the sails flap around. It's called "being in irons". We head into the wind on purpose under engine power to raise and lower sails because at that point of sail, there's no tension on the sails.

When sails are set, meaning raised and their halyards (the lines that raise and lower sails are halyards) secured, the person at the helm 'falls off'. No. This does not mean landing in the water. You fall off the wind - this is tilting the sails to catch the wind. Imagine a compass. Put your wind from the north at the 0 point. In order for the wind to fill your sails and get you out of irons (into motion), you'll have to turn away from the 0 point by several degrees. It doesn't matter which way you turn. Here. If you look at the diagram below, you can see that boats have to turn 30 degrees or more off the wind direction in order to go anywhere. Look at how the sails change direction as the boat turns away from the wind. Now look at the photo at the top again. See how his sails are tight into the center of the boat? That's how you know know he's close hauled. You can also call that 'tight into the wind'. If your sailor isn't paying attention and rounds up into the wind a little too much, it's called 'pinching' and unless it's corrected by falling off, you'll end up back in irons.

Now, directions. Port and starboard refer to the left side and right side of the boat if you're facing the bow (front). Port and left both have four letters. That's the easiest way to remember that. Look at the photo at the top again. See how the sails are billowed out to the starboard side? This means the wind is coming from port. A port tack simply means that the wind is coming over your port rail to fill your sails. Please note that currently, Wikipedia has this definition if not wrong then terribly misleading - it says 'sailing to the left'. And while there's argument that this is technically okay, it's dreadfully difficult to keep straight. You'll be MUCH happier (and sound saltier) if you refer to a tack as the direction the wind is coming from. Is the wind coming over your port rail? Port tack. If it's coming over your starboard rail, you're on a starboard tack.

The last two things we haven't mentioned: How do I know the boat at the top is using a jib rather than a genoa as a headsail? By looking at the sails. In that photo, see how his front sail (headsail) is smaller than his main? Jibs are sails cut smaller and with less bag than a genoa and are designed to handle higher wind speeds. Genoas are bigger sails. Here's a photo of a boat sailing with a genoa. For bragging rights: What tack is he sailing?
See how much fuller this sail is? It's much rounder, designed to catch as much wind as possible. You can also tell there's no much wind in this photo because the sea is pretty flat all around this boat. They aren't going five or six knots. They're lucky if they're doing two or three.

Loughing (say luffing) is when your sails start flapping a bit. It needn't be much, but it means that the air traveling over the surface of your sails isn't smooth. It's not a disaster, but it does mean you're sacrificing a bit of efficiency and possibly speed to lost energy. This photo shows well-trimmed sails - notice how smooth the sails look? There's no lough. Granted, the photo is a moment in time and there may have been all kinds of loughing two seconds after the picture.

Heeling - this refers to the sailboat leaning over while under sail. Compare the two photos. The one on top is leaning over pretty far. The boat on the bottom isn't. (It would be easier to tell if we could see this boat head on rather than from the side - but you can also look at freeboard - the amount of hull out of the water). This bottom boat's pretty flat.

What keeps sailboats from falling all the way over? About 2,000lbs of iron or lead underneath. Next post: Keels, heeling, and knockdowns. 

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