Keel facts for kids

A keel being laid for the USS United States in 1948.

The keel is a very important part at the bottom of a ship or boat. Think of it as the backbone of a watercraft! It runs along the center from the front (bow) to the back (stern). The keel helps keep the boat stable and balanced in the water. For some sailboats, it also helps the boat move smoothly and prevents it from tipping over. Often, when a new ship is being built, the first step is to lay down the keel. This special event is called a keel laying and marks the official start of the ship's construction.

Where Did the Word "Keel" Come From?

The word "keel" has a long history! It comes from old languages like Old English ("cēol") and Old Norse ("kjóll"). Both of these words meant "ship" or "keel." Some experts even think it might be one of the very first English words ever written down! A writer named Gildas used a similar word in his Latin book way back in the 500s.

The Latin word for keel is "carina." This word is where we get the term "careen." To careen a ship means to tilt it on its side. This was done to clean or repair the bottom of the ship. For example, there's a place in Sydney, Australia, called Careening Cove. Ships were often careened there a long time ago.

Keels Through History

Keels have been used on boats for a very long time! People started using them in ancient times.

• One of the oldest examples is the Kyrenia ship, an ancient Greek merchant ship. It had a keel around 315 BC.
• Another old ship, the Uluburun shipwreck from about 1325 BC, also had a basic keel. It might have been more like a strong central plank.

How Ships Were Built Around Keels

Over the years, shipbuilders have used different ways to build boats around their keels.

• Frame First: In some methods, like carvel-built hulls, the keel was laid down first. Then, the main support beams (frames) were added along the keel.
• Plank First: Other methods, like clinker construction, started with overlapping planks that formed the shape of the hull. Even in these systems, the keel was still the starting point for connecting the front and back of the boat.

This image shows two ways to build a boat hull. The one on the right is a carvel-built hull, where planks fit edge to edge.

Different Types of Keels

Structural Keels: The Ship's Backbone

A structural keel is like the main backbone of a ship. It's the lowest and strongest part of the hull. It runs all the way from the front (bow) to the back (stern) of the ship.

• For many years, laying the keel was the very first step in building a ship.
• Today, very large ships are often built in big sections. These sections are then joined together. So, the building process starts when the first piece of steel is cut.

There are a few common types of structural keels:

• Flat Plate Keel: This is the most common type. It's a flat, strong plate that forms the bottom of many large ships.
• Bar Keel: This type is a thick, solid bar. It's often used on smaller boats like fishing boats or tugboats. Bar keels are very strong and can protect the boat if it accidentally touches the bottom. However, they make the boat sit deeper in the water.

Hydrodynamic Keels: Helping Sailboats Move

Hydrodynamic keels are special keels found on many sailboats. Their main job is to work with the water to help the boat sail better. These keels are strong enough to hold the boat's weight.

A sailing yacht with a fin keel.

Keels for Sailboats

Sailboat keels have three important jobs:

• Stopping Sideways Movement: When the wind pushes on the sails, it can make the boat slide sideways. The keel acts like an underwater wing, using the boat's forward motion to create a force that stops this sideways slide, called leeway.
• Keeping the Boat Upright: The wind also tries to tip the sailboat over (this is called heeling). The keel has weight at the bottom, acting as a counterweight. This weight helps to balance the boat and keep it from tipping too much.
• Resting on the Ground: Some keels, called bilge keels, allow a sailboat to sit upright on mud or sand when the tide goes out.

This diagram shows how a sailing keel helps resist sideways movement in the water.

This diagram illustrates how a keel helps a sailboat stay upright by providing balance.

Some sailboats have keels that can move!

• Movable Keels: These can pivot (like a centreboard or swing keel) or slide up and down (like a daggerboard). This lets sailors adjust the keel's depth depending on the water or wind.
• Canting Keels: These are special keels that can swing from side to side. This helps to shift the weight and keep the boat even more upright, especially in strong winds.

See Also

• Coin ceremony
• Kelson
• False keel
• Daggerboard
• Leeboard
• Bilgeboard
• Keel block
• Under keel clearance