Choosing a sailboat that fits your sailing needs is not an easy task, especially if you are new to sailing. With so many types, makes and countless options available, beginners usually don’t know where to start from when they decide to purchase their first sailboats. The first thing you will need to know before looking for a sailboat is what you are planning to do with it. If you are thinking about crossing oceans, then your choice will obviously be different from that of a club sailor. The ‘perfect boat’ is often a rather personal ideal, and discussing these personal preferences is always prone to controversy. Possibly, one of the most important decisions you will have to make is about choosing the right keel type.

What’s the role of a keel?

Before we discuss particular keel types, it is important to understand the purposes of keels, and how they work. Keels serve two main purposes. First, they provide ballast that will prevent the boat from capsizing. As the boat heels over, the weight of the keel will produce a force (or technically speaking, a moment or torque) that will turn the boat back to a more stable position (that is, upright). This is called the righting moment. As a rule of thumb, the heavier and deeper the keel, the stronger the righting moment. The second role of the keel is to prevent the boat from sliding sideways. When you sail for example on a beam-reach point of sail, the wind pushes the boat sideways. However, the keel produces drag that resists that motion. In other words, the keel puts the boat on track.

Choosing the right keel type

There is no such a thing as a perfect keel. Each keel type has its own advantages under certain conditions, and disadvantages under other situations. It is up to you to decide, based on your sailing ambitions, what is most important for you. So let’s have a look at the types of keels available, and their main pros and cons.

Long keel (or full keel)

A full keel is encapsulated as part of the hull and extends from the bow all the way to the stern. These keels are usually found in older boats, typically before the 1970’s. Because of their size and weight, they are the most robust among all types of keels. Running aground with a long keeler is usually safe, while other keel types might be seriously damaged in such an event. The long keel also provides protection to the rudder (and propeller). Rudders usually hinge from the aft end of these keels. This added protection is important not only in the event of running aground but also if the boat hits any floating debris or heavy objects. Long keels also provide more stability when the boat is propped up on the hard.

Full keel sailboat
Full keel sailboat

On the downside, the performance of long keelers is usually poorer than other keel types, especially when it comes to windward sailing. In general, a long keel’s pointing ability (the ability to sail at a small angle relative to the wind’s direction) is lower than that of other types of keel. Overall, the speed of full keel boats is low when compared to modern fin keelers, particularly in light winds. The turning radius is also larger, which makes manoeuvring in tight spaces tricky. The larger radius also results in longer and slower tacking, which is a major disadvantage when it comes to racing. Going astern with a long keeler can be particularly awkward.

However, long keels are very stable in heavy weather conditions and for this reason, they are very popular within the blue-water community. A long keel also provides a much better directional stability than fin keels and is able to maintain a smooth and comfortable course even under harsh weather. This is because the keel offers resistance against the effects of waves and wind gusts trying to turn the boat around.   

Fin keels

A fin keel is a flat, narrow and streamlined plate hanging from the hull. The fin is not part of the hull, but a separate component that is bolted to the bottom of the hull. To compensate for the relatively small ballast, fin keels have a deep draft that increases the arm of the righting force. This type of keel is by far the most common in modern yachts.  

Fin keel sailboat
Fin keel sailboat

The performance advantages of deep fin keels are multiple. They are lighter than full keels, which reduces the overall displacement (weight) of the boat and therefore increases speed. In addition, they are hydrodynamically superior, meaning that drag is small. When sailing windward they provide excellent pointing, and they are also fast at all points of sailing. The narrow keel results in a short turning radius, which allows for short and fast tacking. The short radius also provides exceptional manoeuvrability for berthing and going in and out of marinas. Motoring astern is also relatively easy and precise.

Despite their improved performance, fin keels are in general considered inferior to full keels when it comes to sea-keeping ability. As a result of the lighter design, they usually require early reefing. A narrow fin keel also offers less resistance to rolling. This can result in sudden and strong heeling when a wave or wind gust hits the boat. While their ability to turn fast and easily is an advantage in marinas or racing, it also makes these boats directionally unstable under harsh weather.

An issue of particular concern among cruisers is the exposure of the rudder. Most fin keel boats have a deep spade rudder. Running aground or hitting floating objects can cause serious damages to the rudder. Over the last years there have also been a number of keel failures, many of which have caused fatalities.

An important variation of the common fin keel with a spade rudder is the skeg rudder. The skeg –a sturdy element hanging from the hull and from which the keel hinges– provides a robust protection to the rudder. 

Skeg rudder
Sailboat with a skeg rudder.

Lifting keels

As the name implies, a lifting keel is a type of keel that you can pull up, usually from the cabin. There are a few variations of lifting keels. Some models split the ballast between a ballast stub keel and the lifting centerboard (for example, Jeanneau), while other models have all of the ballast in the keel itself. A swing type of keel pivots about a shaft, but others (usually called daggerboards) simply slide vertically into a slot. In many lifting keel boats, the keel box forms the support of the cabin table. Other models store the movable part of the keel inside the stub keel, which saves a bit of space in the cabin. Keels are usually lifted by a wire or rope wound up by a winch, or by an electric motor activated by the touch of a button.

The main advantage of lifting keel sailboats is the possibility of exploring shallow waters that would be inaccessible to deep draft sailboats. Think of all those beautiful bays and rivers that you’d love to explore but that are too shallow for your boat’s draft. Lifting keel boats were designed to overcome this barrier. The idea is simple: lift your keel and go for it. Indeed, you can even dry out on a sandy beach, although gravel or rocks may damage the hull. Lifting keel sailboats are also easier to launch and recover from a slipway, as well as to load and transport on a trailer.

One main drawback of lifting keels is the added complexity, which many sailors regard as unnecessary. The keel may lift mud and pebbles that can get stuck in the keel box, potentially causing damage to the system or requiring maintenance. A mechanical failure is particularly concerning when the keel cannot be dropped and you need it. In general, lifting keel boats are more expensive than fixed keel counterparts.

Bilge keels

Bilge keels, also know as twin keels, are relatively shallow keels that are installed on each side of the hull instead of on the centerline. They are very popular in the UK, where many boats are forced to dry out because of the wide tidal range. Under these circumstances, the twin keels provide excellent support, keeping the boat safe and conveniently upright. The shallower draught and built-in support (that is, the keels!) also make them easy to launch, retrieve and transport on a trailer, as well as to store on the hard. Most don’t even need to be propped up and will sit stably on the keels. Examples of bilge keel boats include Westerlys and Hunters.     

The performance of bilge keel boats is usually considered as poor, especially when compared to modern fin keel boats. At least in part, this low-performance reputation comes from the early models that had a poor design. In these models, the keels were simply flat plates with very low hydrodynamic characteristics and were vertical. When these boats heel over, the draught –and therefore resistance to leeway—is considerably reduced. As bilge keels are shallower than fin keels, the righting moment is also weaker, even though the position of the windward keel helps to improve stability in this situation. Since the first generation, bilge keels have evolved and now have more streamlined shapes that are also attached at an angle from the vertical. The latter improvement increases the draught when the boat heels over, considerably improving the performance of windward sailing. 

Bilge keels heeling
Improved bilge keel design. Bilge keels attached to the hull at an angle increase draught when the boat heels over.

While the performance of a bilge keel boat will in general be inferior to that of well-designed modern fin keels, a well designed bilge keeler is an excellent choice for many coastal cruisers.

How and why sailboat keels have evolved?

Once upon a time, boat designers and builders used to make sailboats that could withstand even the harshest weather conditions. In those days, names such as Van de Stadt (1910-1999), Laurent Giles (1901-1969), Francis Herreshoff (1890-1972) and others created sailboats that were not only beautiful but sturdy and reliable at sea. This design paradigm prevailed for many decades, until other designers started to realise the emergence of a group of consumers for whom seaworthiness was not a top priority. In fact, they understood that the vast majority of boat buyers were weekend sailors who would rarely, if ever, sail offshore. This marked the birth of the Cruiser-Racer (or if you like Racer-Cruiser) sailboat. That is, boats that were neither seaworthy cruisers nor the fastest racers. Rather, these boats –which today encompass most of the market of new boats— offered a compromise. Simply put, they offered reduced seaworthiness for more comfort and improved performance. The main changes that were introduced by this change in design philosophy include less ballast to improve speed, wider beams, more comfortable and shiny cabins, and more important, the fin keel. Since then, fin keels have dominated the yacht market.

Fortunately, seaworthiness is not completely dead. There are still boat builders that produce well-built boats for offshore sailing. Also, with more people interested in cruiser-racer yachts, there is a wide range of old, reliable cruisers available at excellent value for money. If you are thinking of becoming a serious cruiser, you are likely to find many blue water sailboat bargains available.

Buying a sailboat: boat keel types

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