When you are learning to sail, understanding the parts of a sailboat can be confusing. We have listed the major parts of a sailboat in the diagram below to help get you started.
The common sailboat comprises eight essential parts: hull, tiller, rudder, mainsail, mast, boom, jib and keel. The hull is the shell of the boat, which contains all the internal components. Its symmetrical shape balances the sailboat and reduces drag, or the backward pull caused by friction, as it moves in the water. Inside of the hull in the stern, or back of the boat, is the tiller, which is attached to the rudder in the water. Think of the tiller as the boat's steering wheel and the rudder as the tire. To maneuver a sailboat to the right, for example, you pull the tiller to the right side of the boat, causing the rudder to alter its direction.
If you think of the tiller as the steering wheel, then the sails and the keel are the engines. The mainsail is the larger sail that captures the bulk of the wind power necessary to propel the sailboat. Its vertical side attaches to the mast, a long upright pole, and its horizontal side secures to the boom, a long pole parallel to the deck. Sailors can rotate the boom 360 degrees horizontally from the mast to allow the mainsail to harness as much wind as possible. When they pivot the boom perpendicular to the wind, the mainsail puffs outward. Conversely, it goes slack when swung parallel to the wind. This freedom of movement allows sailors to catch the wind at whatever angle it blows. The jib is the smaller, fixed triangular sail that adds additional power for the mainsail. The keel, a long, slim plank that juts out from the bottom of the hull, provides an underwater balancing force that keeps the boat from tipping over. In smaller sailboats, a centerboard or daggerboard serves the same purpose as the keel, but can be raised or lowered into the water to allow for shallow water sailing.
Before a boat can move in the water, it first must be able to float. In the next section, we'll discover how something as heavy as a sailboat can stay afloat.
Floating depends on two things: displacement and density. Archimedes' principle, which explains the concept of buoyancy, states that in order for an object to float, it must displace an amount of water equal to its weight. As a sailboat's weight pushes downward and displaces water beneath it, an upward force equal to that weight holds the boat up.
Here's where density comes into play. To displace enough water to remain afloat without becoming submerged, a boat must have an average density less than water. For that reason, the hull of the boat is hollow. Whether the boat is made of concrete or fiberglass, its average density is less than water. Think about it: If you put a basketball and a bowling ball in a swimming pool, the air-filled basketball has an average density much less than that of water, so it will float. The solid bowling ball, however, will sink immediately. This is how anything from a small sailboat to an aircraft carrier can manage to stay on top of the water.
Surface area also helps to keep the boat afloat. More surface area gives an object a better chance to displace enough water to offset its own weight. For instance, a small ball of clay likely will sink before it can displace the amount of water equal to its weight. But if you flatten the ball into a thin pancake, there is more surface area to distribute the weight across and displace the water, so it will float. For more information on precisely how a steel ship can float, read how boats made of steel float on water when a bar of steel sinks.