There are two parts to any sailboat keel, and each part is traditionally made of just one of three materials each. But there are large differences between the materials.
Sailboat keels are typically made of reinforced fiberglass layers, steel, or wood, depending on the hull material, boat model, and build year. Keel ballast usually consists of lead or iron.
Ballast can consist of other materials too. Below I’ll discuss all materials and the arguments for each one.
In this article:
- What Material Are Sailboat Keels Made Of?
- Ballast Materials Compared
- How Much Does a Lead Keel Weigh?
- How Do Sailboat Keels Work?
What Material Are Sailboat Keels Made Of?
Keel outer materials
There are two parts to any sailboat keel: the shell and the ballast. The shell is generally made of the same material as the hull. This can be wood, laminated fiberglass, or steel. In some cases, the keel is made from a different material than the hull, but this is not very often the case. You mostly see this when the keel is a separate part from the hull, for example with fin keels, which can be bolted on.
Most ballast is made out of lead or iron. However, there are more materials that can be used, depending on budget or space availability.
Frequently used ballast materials:
- (cast) iron
- concrete with iron waste
The most popular materials are definitely lead and iron, with lead being the best ballast material.
Why are keels made of lead?
Lead has the highest specific weight of the different sailboat keel materials available, which means it requires the least amount of volume. At 11.3 kg/dm3, it is 56% denser than iron (7.25). This means you’ll need 56% less volume to get the same ballast weight, saving you nearly half the space.
Do all sailboats have lead in the keel?
Not all sailboats use lead in their keels. For example, a lot of cheaper boat designs will use cast iron to reduce cost. Some sailboats carry no ballast in the keel at all. Especially inland-water boats with flatter hulls require less ballast or none at all.
Ballast can also consist of multiple materials, and often times boat builders choose a different material for the integral ballast (the ballast in the hull) and the keel ballast (the ballast in the tip of the keel) to keep costs down. In the popular fin keel design, space is very limited, which is why lead is the go-to material for larger cruisers that require high keel ballast. For daysailers, which require lower keel ballasts, iron can be used, or even cement.
Ballast Materials Compared
|Material||Specific weight in kg/dm3|
|Concrete with iron||4 – 5|
Lead is the densest material, but it also the most expensive. High-end sailboats will use lead as their preferred ballast material, or a combination of lead and iron.
Whenever iron is used in a keel design, it is always cast iron. Cast iron is the second densest material available, and a lot less expensive than lead. Most budget sailboats use cast iron ballast, both in their keel and hull.
Sailboats that require less ballast and have a strict build budget can use concrete instead of metals. Concrete is more than four times less dense than lead, which means it is only a viable option if you don’t need a lot of ballast to begin with. Whenever concrete is used, iron waste is added into the mixture to roughly double the weight without driving up the cost dramatically.
Some sailboats use water as integral ballast (ballast carried in the hull), but it is very rare. Well-known sailboat models that use water ballast are the Hunter series (over 26 feet).
The use of water is a lot more common on ships like cruisers, motor yachts, and container carriers. The advantage of using water is that you can easily increase or decrease the ballast by adding or dumping water, which is readily available wherever you go.
How Much Does a Lead Keel Weigh?
The weight of a lead keel depends on the desired ballast to displacement ratio. The used weight would be the same for any ballast material, be it lead, iron, or cement. The difference is that lead would take the least amount of volume, since it has the highest specific weight of all typical keel materials.
The average weight of a 35-foot sailboat keel is between 5,000 – 6,000 pounds, but the weight varies between 200 – 12,000 pounds based on the sailboat size, use, and keel design.
How Do Sailboat Keels Work?
In short, a sailboat keel’s weight is used to to increase displacement and lower the center of gravity, while its surface is used to increase wetted surface. This helps to stabilize the boat, but also provides directional stability. For a more detailed explanation on how sailboat keels work, I recommend reading this article.
Sailboats may be boats with sails, but they’re not one homogenous category. Sailboat types differentiate by design and use, and even the type of culture that permeates each subgroup. Let’s divide sailboats by hull types, rig types and activities/uses.
Sailboat Hull Types
Sailboats ride on different hulls, which differ in the total number of hulls and their shape. The basic three hull types include:
- Monohulls (one hull)
- Catamarans (two hulls)
- Trimarans (three hulls)
Monohulls have one hull but that doesn’t make them all the same. Traditional monohulls may have full keels (heavy encapsulated ballast that runs along the bottom of the hull), cutaway keels (similar to full but the forefoot is cutaway allowing the boat greater maneuverability in tight quarters) or bolted on fin keels that may have a bulb at the bottom for extra ballast to keep the vessel stable.
Monohulls can also have a swing keel, daggerboard or centerboard that retracts up into an appendage in the hull itself. With the keel or board up, the boat can enter shallow water and can travel faster downwind. With the keel down, the vessel tracks better upwind.
Small monohulls like sailing dinghies, may also have shallow planing hulls that can surf off a wave. Finally, monohulls can also foil on appendages (usually made of carbon fiber) with the actual hull out of the water when a minimum speed is reached.
Catamarans (often nicknamed “cats”) have two hulls with a deck or trampoline in between. Large cats (35 feet and over) have become popular in charter use because they offer more interior and deck space and an easier motion to induce less seasickness. Small catamarans usually have just a trampoline in between the hulls and make fun daysailers.
Because catamarans don’t have deep and heavy keels, they tend to sail faster off the wind. Foiling catamarans were made popular by the America’s Cup races and are proliferating into general cruising use.
Trimarans have three hulls: a main hull and two amas (side hulls used for stability). On some trimarans, the arms that hold the amas can fold inward, making the trimaran narrower and in some cases trailerable. Large cruising trimaranas are gaining popularity because they are stable and fast sailers.
Sailboat Rig Types
Sailboat rigging includes:
- the mast(s);
- and the shrouds or stays that hold up the mast.
A sailboat with one mast is usually a sloop with one mainsail and one headsail.
A cutter rig usually has one mast but two or more headsails. This rig “cuts” the foretriangle between the head (forward) stay and the main mast. Multiple headsails allow for flexible sail combinations in variable wind conditions.
Ketches and yawls have a secondary mast behind the main one. The ketch configuration places that mizzenmast behind the mainmast but ahead of the rudderpost while the yawl places it behind the post. The second mast is shorter than the main mast. Both of these designs (split rigs) provide more sail area that isn’t reliant solely on the height of the mainmast and therefore can be easier to manage when sailing shorthanded.
Schooners also have multiple masts—two or more. However, the foremost mast is shorter than the main mast. Tall ship rigging is in its own category and can get quite complex.
Sailboat Types by Primary Use
You can do many of the same things on all sailboats, but some types are more specialized.
Sailing dinghies: Small boats usually sailed by one or two people, sailing dinghies are often used to teach new sailors. That said, experts on high tech sailing dinghies compete in athletic racing up to Olympic level.
Day cruisers: Although any sailboat can be cruised for a day, day cruisers are often boats shorter than 30 feet that are designed to be sailed for an afternoon. They’re usually more Spartan in their outfitting and may or may not have a cabin with amenities.
Sailing cruisers: These sailboats can be monohulls or multihulls and are designed to cruise for weekends or longer. They usually have a berth (bed), a head (toilet) and a galley (kitchen). They can be sloop, cutter, ketch, yawl or schooner-rigged and vary in length (from 25-85 feet). Larger sailboats tend to fall into the crewed superyacht category.
Racing sailboats: Most offshore racers are larger boats crewed by multiple individuals while smaller racers can be single or double-handed. Racing boats are usually built lighter, have fin keels and laminate performance sails.
Racer/cruisers: These designs try to straddle the two above. They’re usually more lightly built cruisers with full amenities so they can be weekended. Some people will argue that these boats are a compromise for owners who want to primarily cruise but also race.
Bluewater cruising sailboats: These boats are designed to cross oceans or sail “blue waters.” They’re typically heavier in build with a stout rig and are fully equipped for extended offshore use.
Motorsailers: This term has fallen out of favor since it’s often pejorative. These sailboats may rely on the engine to sail in light wind conditions, especially due to their excessive weight.
Antique/classic sailboats: These are usually older restored vessels. They may be built of wood and have classic yawl rigs. These sailboats are often showcased in special events.
Sailboats occupy multiple segments and experienced sailors learn the finer points of design and use. Then, they never see two sailboats the same way again.
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The keel is a fixed appendage on the bottom of the hull that provides the sideways resistance needed to counter the force of the wind on the sails. The keel also carries ballast, usually iron or lead, the weight of which counteracts the force of the wind that causes a sailboat to heel, or lean over. On a modern boat, the keel is shaped in the form of an airfoil wing to generate lift, which helps it sail closer to the wind.
A keelboat is generally larger than 20 feet and can be as large as a megayacht at 200 feet. A boat smaller than 20 feet without a keel is referred to as a dinghy. A dinghy has neither a keel nor a ballast. To resist sideways movement it has a centerboard or a daggerboard that can be lowered or raised as needed.
Will This Sailboat Capsize?
Unlike a dinghy, a keelboat won’t capsize. In a strong wind, it may heel a long way over, but the ballast in its keel is designed to keep it from capsizing. In a dinghy, to resist heeling you would use live ballast – the crew sitting out on the edge of the boat to counter the effect of the wind.
Smaller keelboats are often used in sailing instruction as these boats are small and responsive enough to provide the new sailor with the feel and feedback important when learning, but big and stable enough to carry an instructor and students in comfort.