What Keeps a Sailboat from Tipping Over?

ByCoral Dawn Drake May 8, 2021

Have you ever watched a sailboat out on the water in the full wind and wondered, “How on Earth does it keep from falling over?” It’s a fair question.

Sails put a lot of pressure on a boat, which would easily tip it over if there were no counter pressure. Thankfully, sailboat makers have taken this problem into account.

What Keeps a Sailboat from Tipping Over?

What keeps a sailboat from tipping over? Counter pressure provided by a keel, daggerboard, or centerboard acts as a ballast and keeps a sailboat from tipping over. In the absence of ballast, the sailor uses their body weight to counteract the wind’s pressure and keep the boat from tipping over.

There are a number of different designs in keels to keep your boat from tipping over. The design of your boat is also an important element in avoiding capsized. Here’s what you need to know about what kind of keels there are and how they might help you to have a capsize-free sailing experience.

What Keeps a Sailboat from Tipping Over?

Sails exert a lot of pressure on a sailboat to go sideways rather than straight. Without adequate counterpressure, that pressure can push a sailboat right over.

For this reason, the vast majority of sailboats and all ocean-worthy sailboats have something underwater to counteract the pressure of the sails and keep the boat moving forward and not tipping over.

What is the Fin on The Bottom of a Sailboat Called?

If you’ve ever seen a sailboat out of the water or dove underneath one, you may have been surprised to see a very significant fin-like structure on the bottom of the boat.

This fin-like structure is called the keel, and it is what keeps a sailboat from falling over. The keel acts as an underwater ballast that resists going up, and therefore prevents the boat from going down.

How Long is a Sailboat Keel?

Sailboat keels vary in length depending on the size of the boat. The bigger the boat, the bigger the sails, and the bigger the keel needed to counteract their pressure.

Racing boats that carry large sails for the size of the boat often have correspondingly large keels. In general, keels vary from between 20 feet to as large as 200 feet on very large yachts.

What If A Boat Doesn’t Have A Keel?

If a boat doesn’t have a keel, it will depend on an above-surface weight to counteract the pressure on the sails. Very small sailing craft like dinghies may not have any kinds of keel.

Lack of keel allows them to be durable and sail in very shallow waters, but it also makes them prone to tipping over under full sail. To counteract the pressure on the sail, sailors use their body weight. They do this by leaning over the side or climbing out on long poles.

What Type of Keel is Best?

If you are shopping for a sailboat, you will quickly find that there are a number of different types of keel available.

The type of keel that will work best for you depends on your needs in a boat, where you want to sail, and what kind of conditions you want to sail under.

Here are a few keels that may be available to you and what you should consider about each of them:

Full keel	Fin keel	Drop keel	Swing keel	Bilge keel
Attached to hull down the center	Bolted to hull	Rests in narrow trough and goes up and down	Rests in a big trough and moves on a pin at angles	Attached to hull on both sides
Slowest	Fastest	Faster	Faster	Slower
Low maneuverability	Great maneuverability	Great maneuverability	Great maneuverability	Low maneuverability
Draws a lot of water	Draws a lot of water	Can draw very little water	Can draw very little water	Draws medium water
Sturdy if you run aground	Likely to be damaged if you run aground	Pops up and isn’t damaged much if you run aground	Swings up and hits hull if you run aground, potentially damaging hull and keel	Sturdy if you run aground
Cannot be removed	Cannot be removed	Can be removed	Can be lifted, not removed	Cannot be removed

Full Keel (or Long Keel)

A full keel sailboat, also known as a long keel sailboat, has the keel built into the hull. The keel extends from the bow all the way down to the stern. The keel gently slopes down from the bow and is even along the bottom of the boat to the stern.

Full Keel Pros

Stable. A full Keel has the stability to hold up to the roughest weather conditions and waves without turning over.
Sturdy. A full Keel draws a fair amount of water, but if you do happen to hit the ground, it is unlikely to do damage to this keel, which is integrated into the hull.
Affordable. Many older boats have full keels and come at a very affordable rate.

Full Keel Cons

Slow. Full keels are heavy, which slows the boat down overall, and they don’t offer much maneuverability if you are trying to maintain speed at an upwind reach.
Draw a lot of water. Full keels are generally quite long and will cause your boat to draw a fair amount of water even for a smaller boat.
Reduced maneuverability. Regardless of what speed you’re going or what angle you are to the wind, you may experience less maneuverability with full keels.

Full keels are heavy and big enough to counteract significant pressure on the sails, even in heavy wind. They were the standard before the 1960s and 70s, when technology advanced to create more delicate keels that could accomplish similar functions.

The problem with full keels is that they make it difficult for the boat to sail upwind and may reduce speed overall. Because they are so long, they also dramatically affect how much your boat will draw. Even a relatively small boat may not be able to approach many coastal waters if it has a long keel.

Who Full Keels are Best for:

Values stability in rough conditions
Isn’t worried about optimal speed
Sails and docks in deeper waters
Wants an older sailboat or is willing to do some shopping to find a full keel in a modern sailboat.

Fin Keel

Fin keels are very common, especially for boats who want good performance under ocean conditions. These streamlined fins are bolted to the bottom of the hull. They generally have a fairly deep draft to offer the correct counterpressure to the sails.

Fin Keel Pros

Maneuverable. Thin keels are slender and let you turn much faster than heavier options.
Light. Fin keels are much lighter than full keels, which means that your boat will have less drag and go faster overall.
Affordable. Fin Keels are very common and present on most modern midsized sailboats.

Fin Keel Cons

Less stable. Because fin keels are lighter, they are also less able to resist heavy ocean conditions or sailing under full sail in heavy winds.
More delicate. If you hit something at speed with a fin keel, there is a decent chance that your keel will be damaged.
Draw a lot of water. Fin keels are very long, and they can’t be adjusted, so your boat will draw a fair amount with this kind of keel.

Fin keels are much lighter than full keels, which means that boats equipped with them go faster. They are slender, so they reduce drag and enable faster turning and maneuverability. Unfortunately, they are not as able to handle very heavy seas, as the lighter design requires more handling to prevent the boat from rolling.

Who Fin Keels are Best for

Wants a fast, light boat that can handle full sails
Values maneuverability over stability
Sails and docks in deeper waters

Drop Keel (or Lift Keel or Daggerboard)

As you might expect, the drop, or lift, keel can be lifted and dropped into place. These are otherwise known as daggerboards.

Drop Keel Pros

Fexibility. Drop keels allow you to sail in shallow or deep water with equal effectiveness.
Durability. Drop keels can pop up into their frame if you hit something, which means that they can hold up to the bumps of shallow-water-sailing much better than other options.
Maneuverability. Drop keels are slender and adjustable, so they offer great maneuverability.

Drop Keel Cons

Less stable. Drop keels are very light and will not provide as much ballast in heavy seas. One exception might be in a multihull boat, where a skilled sailor can lift and drop daggerboards to react to the ocean.
More expensive. Drop keels require significantly more hardware and work, as well as moving pieces, which means that they cost more.

The advantage of drop keels, or daggerboards, is that they can be dropped into place when you need them and lifted up when you don’t. Many models also allow you to adjust the board halfway so you can still have some ballast in shallow waters.

Daggerboards can usually be completely removed if desired. The downside of drop keels is that they are generally less heavy and robust in the open water and rough conditions.

Who Drop Keels are Best for

Values flexibility over stability
Often sails in shallow water but also needs to navigate ocean sailing
May occasionally run aground

Swing Keel (or Centerboard)

Centerboards allow more flexibility than daggerboards or any other kind of keel because they rotate on a rod. Centerboards cannot be removed entirely, but they can be raised or held in various positions between up and down.

Swing Keel Pros

Maneuverability. Swing keels can be adjusted at several different angles in their spacious slot, which can allow you to adapt to conditions with great maneuverability.
Flexibility. Swink keels can go up to allow you to draw almost nothing or go down to give you great handling in deeper water.

Swing Keel Cons

Potential for damage. Swing keels will not naturally pop back up into their space like a drop keel, so if you run aground, there may be a higher potential that the centerboard will damage the hull.
Cost. Centerboards are often quite a lot more expensive than other options, thanks to the large gap that must be created for them and the delicate machinery around the rod. You’ll pay more for a boat equipped with one.

You can position a centerboard almost any way you want, allowing much more flexibility in how you maneuver your boat. You may adjust the centerboard differently when you want to sail upwind in rough conditions or when you are frequently tacking.

Because centerboards will not necessarily move up smoothly into their slot, they may be more likely to damage your boat if you run aground. Centerboards aren’t as heavy as some other keels, so they may not give you as much stability on the water.

Who is the Swing Keel Best for?

Wants Optimal Performance under sail and is willing to sacrifice stability in rough conditions
Often sails in shallow water, but is confident that they will not run aground unexpectedly
Enjoys tinkering with many elements of the boat to improve performance

Bilge Keel

Bilge keels are also known as twin keels. They enable the boat to have a shallower draft with fixed keels. They also help the boat to sit evenly if the water dries out under it.

Bilge Keel Pros

Sturdy and level. Keeps boats level and even when they are on dry ground
Shallow draft. Offer a shallower draft than many other types of keel
Tough. Durable against bumps and scrapes

Bilge Keel Cons

Reduced performance. Don’t offer great performance in open water or under full sails
Fixed depth. Don’t have flexibility in what they draw, which can be frustrating in places with dramatic tidal swings

When the tide goes out, bilge keels keep the boat upright and safe. They’re also quite easy to launch and store on dry dock. What you gain in convenience from a bilge keel, you, unfortunately, sacrifice in performance.

Bilge keels have come a long way since the first models. They are now streamlined to have improved performance while still offering great stability. Still, they are unlikely to function as well as other types of keels in open water.

Who is the Bilge Keel Best for?

Sails somewhere with dramatic tidal surges or often wants to leave their boat at dry dock
Wants shallow draft that can handle some bumps if it begins to go aground
Doesn’t mind a reduction in performance under sail

What Does it Mean to “Lay The Keel”?

Traditionally, the laying of a ship’s keel marked the birth of a ship. It was especially important for Naval vessels, although it also was a popular ceremony in civilian vessels. Typically the ceremony was an informal event put together by the boat builder.

After a gathering and ceremony, the keel was put into place and a silver Memento might be presented. These days, boats are made in parts that are constructed separately and brought together, eliminating the significance of this type of event.

Can a Capsized Sailboat Right Itself?

Some capsized boats can right themselves easily, while others may have a very difficult time being righted. Here are some things to keep in mind about capsizing, righting capsized boats, and what keels have to do with it.

What Keeps a Sailboat from Tipping Over?

Knocking Down a Keelboat

Keel boats rely on a deep, heavy keel to keep them upright even when they are sailing under large sails for the size of the boat. Keel boats heal over a lot when they are sailing correctly. It is perfectly normal for the sail to be at a significant angle to the water under a lot of pressure.

However, sometimes a keelboat will heel over too far, in what is known as a knockdown. At this time, the sails are angled away from the wind and the boat is all the way leaned over towards the ocean.

When this happens, the sail should luff, taking pressure out of them and allowing the keel to right the boat. If the sails are not luffing and they are very closely angled to the water, you should luff them yourself so the keel can right the boat. If the keelboat is allowed to dip sails into water, it may take on water and sink.

Capsizing a Monohull

A monohull sailboat with any sort of keel can be capsized under rough conditions or improper handling under full sail in high winds. Boats with full keels are the least likely to capsize in rough condtions.

Many times, monohulls can be righted if the sails are luffed and lowered. Sometimes, the sails will be stuck up and filled water and must be removed for the boat to write itself.

If the boat fills with water, it may stay down. Monohulls with heavy keels that feel with water often sink, sometimes surprisingly quickly.

Capsizing a Multihull

Multihulls were designed, primarily, for stability. They are often less likely to capsize in rough weather. This is because multihulls generally have both a keel to help balance them against the pressure of the wind and the advantage of a wider surface area that is more difficult to tip over.

Many multihulls also have flexibility between the hulls so the boat can adapt to rough weather conditions continuously. Adjustable daggerboards or centerboards on both sides allows the sailor to adjust the movement of the boat to the oncoming weather.

If a multihull does capsize, the chances are slim that it will get upright again without being hauled to shore. On the upside, multihulls are designed not to sink when they are capsized, even if they fill with water. They typically have air-filled chambers or highly buoyant material to keep them from going down.

Pick the Right Sailboat for You

You won’t enjoy your sail if you’re worried about your boat tipping over, but there’s no reason to make unnecessary compromises in performance. Think honestly about what you’d like to do with your sailboat and choose a keel that works for your needs.