What Is Sailboat Keel? And How Does It Work?

No matter whether you are a beginner or already experienced sailor, it is imperative for you to know what sailboat keel is and how it works. 

To answer the question “What Is Sailboat Keel? and How Does It Work?” I have written this blog post with a hope to help you with the answer.  

So, What Is Sailboat Keel? On a boat, the keel is a wing or fin that extends downwards from the bottom of the hull. It comes in different types and shapes such as long keel, fin keel, centerboard, and bilge keels.  

What does the keel do on a sailboat? The keel on a sailboat serves as a mechanism to resist sideways drift or leeway. Additionally, keels hold the ballast that keeps the boat right-side-up and provide stability to it. Keels also minimize the risk of the boat’s capsizing. 

Read on below as I go over everything you need to know about the keel: its types and functions etc.

What Exactly A Keel Does On A Sailboat? 

Keel designs have been improved over the years as improved materials have been invented with great strength and sturdiness. Older vessels used long keels that were an integral part of the structure of the hull. Recently we have seen that more boats are now designed with many variations of fin keels. 

However, there are other keel types that are still being used such as full-length keel, modified full keel, fin shape keel, wing or bulb keel, bilge keel, centerboard or daggerboard keel which we will discuss all in details later in this post. 

Regardless of its type, a vessel’s keel has three main purposes, 

1. To resist leeway:

The keel protects the sailboat from the sideways force of the wind. In fact, sailboat keels utilize the forward motion of the boat to create lift that nullifies the leeward force of the wind and transforms the original sideways motion of the wind in the sails into forward motion.

Without a keel or centerboard, the leeway force of the wind would simply push the boat sideways away from the wind. A keel allows the vessel to go forward.

2. To Keep the sailboat stable:

Additionally, keels hold the ballast or added weight that keeps the boat right-side-up. The more upright your sailboat is the faster you are going to travel and the more comfortable your sailing experience will be. The ballasts are generally placed at the bottom of the keel.  Due to this weight force of the ballast, the risk of the boat’s capsizing is also diminished.

3. To reduces heeling angle:

A sailboat with well-designed keel experience a few forces such as gravity, buoyancy, leeways, heeling and righting force to name a few. 

Gravity pulls the boat down and buoyancy force keeps it afloat. The heeling force pushes the vessel to sideways and the righting force from the keels keeps the boat upright. And thereby reduce the heeling. It is absolutely normal for a sailboat to heel to some degree. When this happens the righting force generated by keel counteracts this force and keeps the boat upright. 

Many experienced sailors can control this heeling angle by using the boat’s sails to balance these forces out. 

4. To generate lift: 

The forward motion of a vessel is utilized by keel to generate lift in order to cancel out the leeway force. The lift helps the boats to sail towards the wind.

Sailboat Keel Types

The keel come in many different types, shape and sizes these days such as full-length keel, modified full keel, fin shape keel, wing or bulb keel, bilge keel, centerboard or daggerboard keel, etc. Each falls into a specific category and has its own design and shape as well as pros and cons.

Does The Keel Type Affect The Boat’s Speed Or Balance? 

The answer to the question above is “Yes”, the boat’s speed and balance are directly affected by the shape, type, and size of the keel itself. For instance, full-length keel or long keel sail very comfortably, however, they are very slow. 

To give you a more detailed answer on the question above, we need to discuss each keel type in more detail to get an idea of how each type effect the sailboat’s speed, balance, and comfort.

Fixed Keels:

Full-length keel: Usually this type of keel found in tradition sailboats. The full-length keel extends the entire length of the hull and has the largest amount of wetted area and it is also the heaviest of all other keels out there. 


  • Because the full-length keel is extremely heavy, it provides the most stability and comfort while sailing.
  • Super effective in preventing leeways force created by the wind
  • No need for the sailors to set on one side to prevent capsizing


  • Because of its large wetted surface, it has considerably more drag than others and slower. 
  • These type of keels are difficult to maneuver due to weight and design, especially in close quarters.
  • The boats with this type of keel can not surf very shallow waters 

Modified full keel: Like the full-length keel, this model extends almost over the entire length of the boat with the only difference that there is a notch cut out from the front part of the hull. This notch reduces the amount of wetted area and thereby it enhances the overall performance of the boat. The rudder is often attached to the aft end of the hull. 


  • Because this type of keel is extremely heavy
  • It provides more stability and comfortable sailing experience.
  • Vessels with modified full keel experience low heel and low slippage due to the weight of the keel. 


  • Because of its large wetted surface, it has considerably more drag than others and slower. 

Fin shape keel: Due to its fin-shape design it is called fin shape keel. These type of keels are most common on recreational and racing sailboats. A fin keel is separate from the rudder and generally has deeper length… 


  • High in performance and relatively narrower and smaller in size.
  • The fin keels have less wetted area and therefore less drag that provides higher speed. 
  • Fin shape keel has lead ballast which is bolted to the flattish bottom of the hull which makes it very stable.
  • Comfortable steering


  • Lightweight designs difficult to maneuver in heavy weather
  • More inclined to round-up when hard-pressed
  • Require early reefing
  • Slightly unstable than full-length keels
  • In downwind may broach quickly 

Bilge Keel: Sailboats with bilge keel are entirely different than other keel types since it has two keels instead of only one. Bilge keels are typically used in areas with great tidal changes such as England. So, the sailboat can safely dry out during low tides and stand securely upright on the sand or mud on its two keels. 


  • Great protection when grounding
  • Great for areas with great tidal changes
  • Almost as good as Fin keels
  • Best to have in shallow waters/beaches etc


  • Slower in general
  • Reduced windward speed specifically 
  • Can roll over if one keel sinks in soft ground or hole

Bulb Keel: This keel is once of the variations of the fin shape keels. Bulb keel has its ballast bulb at the lower part of the keel which gives it a great force to counteract the leeway. The maximum upright position is achieved when bulb keels are long, thin keels or daggerboards. They are not used for the vessels which are intended to surf shallow waters, but they are mostly found on vessels which are designed for offshore boats.  


  • Slower in general than fin keels
  • Great for use in shallow waters
  • Great righting capability


  • When aground hard to get it off the ground.
  • Significantly slower than a Fin Keelboat

Moveable Keels: 

Centerboard & Daggerboard: Most sailboats under 15 feet are equipped with a centerboard or daggerboard. They are moveable keels which retract out of a slot in the hull and it functions exactly as a keel to keep the vessel secure from sideways forces.

This difference between Centerboard and Daggerboard is how they retract. Centerboard folds like a pocket knife while daggerboard moves straight up and down.  


  • Both designs can be lifted up so boats can surf shallow waters


  • Provide less ballast when we compare it to fixed keels
  • Not as effective as fixed keels in counteracting leeway force
  • It is a moving part subject to wear and tear and requires maintenance

What Are Sailboats’ Keels Made Of?

Sailboats’ keels are generally made of the material that the vessel itself is made of, typically they are made of wood, aluminum or fiberglass.

Typically, boat’s ballast that is held at the lower part of the keel is made of lead.  


I am the owner of sailoradvice. I live in Birmingham, UK and love to sail with my wife and three boys throughout the year.

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