cruising yacht bulb keel

Sailboat Keel Types Compared: Pros and Cons of 13 Types

There are various keel designs, each with specific advantages and disadvantages. For instance, full keels provide better stability and tracking, making them a popular choice for long-distance cruisers. On the other hand, fin keels enable sharper turns and quicker reactions, which appeal to racers and those seeking a more nimble experience. Choosing the right keel type for your sailboat depends on your sailing preferences, cruising goals, and intended destinations.

A sailboat's keel plays a significant role in its overall stability, performance, and comfort. It helps you maintain balance, steer your boat, and improve your boat's sailing efficiency. Sailboat keel types impact not only the performance and handling of your sailboat but also its suitability for different sailing conditions.

Let's compare 13 different keel types, and discuss their strengths and weaknesses, as well as their practical applications.

• The keel types that are known for their comfort and seaworthiness are full keel, bilge keel, wing keel, Scheel keel, and fixed keel.
• The best keel types for speed are canting keel, bulb keel, and wing keel.
• For improved maneuverability and agility , the best keel types are swing keel, centerboard keel, and daggerboard keel.
• The keel types that provide the most stability are bulb keel, fixed keel, and fin keel.

On this page:

Pros and cons of 13 types of keel, canting keel, centreboard, daggerboard, lifting keel, scheel keel.

If you're curious what these keel types look like, here's our illustrated guide on sailboat keels .

Full-length keel : Full-length keels run the entire length of the boat. They offer excellent stability and are popular among offshore cruisers who require a solid, rugged sailboat. Full keeled boats are better suited for heavy weather, but they may be slower due to their weight and drag.

Fin keel : Fin keels are thinner and generally used for racing, as they provide a good balance between speed and stability. Their reduced drag means faster speeds but might be less stable compared to full-length keels in heavy seas.

Bulb keel : A bulb keel features a heavy, rounded weight at the bottom of the fin keel. This extra weight lowers the boat's center of gravity and provides additional stability without significantly increasing drag.

Canting keel : A canting keel is a high-performance feature that can pivot from side to side, allowing the boat to maintain optimal stability while heeling over on its side to maximize speed in racing scenarios.

Centerboard : This keel type features a retractable board that can be lowered for sailing upwind and raised in shallow waters. Centerboards are often found on smaller boats and dinghies.

Swing keel : Swing keels operate on a hinge, swinging up and down to adjust the boat's draft. They balance the benefits of a larger keel with the convenience of a shallow draft for docking and beaching.

Wing keel : Wing keels are similar to bulb keels but with two small wings on either side of the bulb. These wings increase the effective surface area, offering better stability and shallower draft capabilities, ideal for coastal cruising.

Bilge keel : Bilge keels are found on boats with two smaller keels on either side of the hull rather than a single central keel. This design is most commonly used in tidal waters and on small fishing boats, allowing the boat to sit upright when grounded during low tide.

Daggerboard : Similar to a centerboard, a daggerboard is a non-weighted, removable board that slides vertically through a slot in the hull. This type is also commonly seen on dinghies and smaller sailboats.

Fixed keel : Fixed keel provides good stability and is less prone to damage than other keel types. However, it can limit the boat's ability to sail in shallow waters and may make it more difficult to trailer the boat.

Lifting keel : A lifting keel can be raised or lowered, providing both the benefits of a deep keel for improved stability and performance and a shallow draft for easier access to shallow waters and docking.

T-keel : T-keels provide improved stability and upwind performance, which can be desirable for sailors. However, their larger draft and vulnerability to grounding should be considered when deciding if this keel type is the right choice for your sailing adventures.

Scheel keel : This offers unique benefits, and it could be an excellent choice for your sailboat if you prioritize stability, shallow draft, and efficient upwind sailing. However, you should consider the potential drawbacks, such as decreased speed and increased maintenance, before making a final decision.

Pros of full keel

A full keel has several advantages that make it an appealing option for many sailors. First and foremost, it offers exceptional stability , which is particularly important when you're out at sea for extended periods. With a full keel, your sailboat can better resist the forces acting on the sails, ensuring a smoother and safer journey.

Another significant benefit is the durability of a full keel. Because of the large surface area and the way it's constructed, full keels tend to be very strong and resilient, making them perfect for long-distance cruising. Additionally, this type of keel provides excellent tracking , helping your sailboat stay on course in various conditions.

Lastly, full keel sailboats are less likely to be damaged when grounding , as the keel's large surface area allows for better weight distribution. This characteristic can be especially useful when navigating shallow waters or exploring uncharted territories.

Cons of full keel

Despite the many advantages of a full keel, it also has some drawbacks. One of the most noticeable disadvantages is its effect on sailboat performance. Full keels tend to be less maneuverable than other keel types, which can be a drawback in tight situations or when you need to make quick adjustments during sailing.

Another downside is the increased wetted surface area, which leads to higher drag and slower speeds when compared to other keel types, such as fin keels. This reduced efficiency can be a concern, especially for those who prioritize performance and speed on their sailing journeys.

Additionally, full keel sailboats may be more challenging to maneuver in tight spaces , such as crowded marinas, due to their reduced maneuverability and larger turning radius. This can make docking and mooring more complex, particularly for inexperienced sailors.

Pros of fin keel

Fin keels hold several advantages for sailors. First, they offer improved performance. A fin keel's streamlined shape cuts through the water more efficiently, allowing sailboats to reach higher speeds with less drag. Moreover, fin keels generally provide better upwind performance than other keel types.

Their maneuverability is another significant benefit. Fin keels allow sailboats to turn more quickly and easily, making them nimble in tight spaces and responsive to the helm. Additionally, they typically have a reduced draft, meaning they can navigate shallow waters more effectively than boats with deeper keels.

Lastly, fin keels are popular for their ease of maintenance . Since they're typically bolted onto the hull, routine inspections and potential repairs are relatively straightforward and accessible.

Cons of fin keel

Despite the benefits, there are a few drawbacks to consider when it comes to fin keels. First, they tend to have less stability than full or bilge keels. Their slender design and reduced weight can make them more prone to sudden heeling, which some sailors may find uncomfortable or disconcerting.

Another potential issue is structural vulnerability . If a fin keel strikes a submerged obstacle, such as a rock or shipping container, it may suffer damage or even become dislodged, which could pose a significant risk to the integrity of the boat. This stands in contrast to more robust full keels, which can better absorb the impact of groundings or collisions.

Lastly, fin keels are sometimes considered less comfortable for cruising sailors. Due to their design, boats with fin keels can experience more motion (both side-to-side and up and down) in rough seas, potentially leading to discomfort or seasickness for the crew.

A bulb keel is a type of sailboat keel that features a streamlined fin with a bulb-shaped weight at the bottom. This design aims to improve the boat's performance, especially in racing conditions. In this section, we will explore the pros and cons of bulb keels.

Pros of bulb keel

Stability : The main advantage of a bulb keel is its ability to provide excellent stability. The bulb's weight is concentrated at its lowest point, which lowers the center of gravity of your sailboat. This design helps keep the boat upright and stable when sailing, especially in strong winds.

Performance : Bulb keels contribute to a sailboat's overall performance by reducing drag. The streamlined shape of the fin and the placement of the bulbous weight make it easier for your boat to glide through the water, increasing your overall speed and agility when sailing.

Upwind sailing : A bulb keel allows your sailboat to sail more effectively upwind. By reducing leeway and maintaining a consistent course, your boat can navigate better through a variety of wind conditions.

Cons of bulb keel

Maintenance : One potential downside of a bulb keel is the increased maintenance required. The bulbs can be more prone to collecting marine growth, which may necessitate regular cleaning and antifouling treatments to maintain peak performance.

Depth : Bulb keels, due to their design, have a deeper draft than other keel types. This means that your sailboat might struggle in shallow waters or require extra diligence while sailing in areas with submerged obstacles or coral reefs.

Pros of canting keel

Canting keels are a popular choice among performance-oriented sailors due to their remarkable benefits in several areas. They offer increased stability and enhanced performance , especially when sailing upwind. This type of keel allows the boat to maintain a more upright position when healing, reducing drag and improving your overall speed and efficiency on the water.

Moreover, canting keels are adjustable , which allows you to alter the keel angle depending on the wind conditions and desired performance. This flexibility can make a significant difference in how your boat performs on the water. Another advantage of canting keels is their improved handling characteristics , which make them easier to maneuver in various conditions.

Cons of canting keel

Despite the many advantages, there are also some notable drawbacks to using a canting keel. One significant downside is their complexity and cost . These keels often require sophisticated engineering and systems, which can drive up the overall price of your boat and may require more maintenance and repairs over time.

Another potential issue with canting keels is their increased vulnerability to grounding . Since the keel can extend deeper beneath the boat, there is a higher risk of hitting obstacles or running aground, especially in shallow waters or unknown territories.

Lastly, canting keels can contribute to changes in the boat's handling characteristics , particularly when sailing downwind. While their adjustability may enhance upwind performance, it may also lead to instability and increased difficulty controlling your boat in heavy downwind conditions.

Pros of the centerboard

A centerboard is a movable keel that can be retracted or lowered to provide stability and balance to your sailboat. Here are some benefits you can enjoy with a centerboard:

• Shallow draft : With a centerboard, you can easily navigate shallow waters and get closer to shore. This is particularly useful for exploring coves, anchorages, and beaching your boat.
• Adjustable performance : By adjusting the position of the centerboard, you can fine-tune your sailboat's performance based on the current sailing conditions.
• Easier transport and storage : Retractable centerboards make it simple to trailer your sailboat and store it in tight spaces without worrying about a fixed keel's height or depth.
• Grounding protection : In case of accidental grounding, a centerboard can help minimize potential damage by absorbing the impact instead of transferring it to your boat's hull.

If you're torn between centerboard, swing, and fixed keels , here's our in-depth article on their pros and cons.

Cons of the centerboard

Despite the advantages, centerboards also come with some drawbacks that you should consider:

• Less stability : When compared to fixed keels, centerboards offer less stability, especially for larger sailboats. This may lead to reduced performance in rough waters or strong winds.
• Maintenance : Centerboards require regular maintenance to ensure they remain functional and efficient. This may include cleaning, lubricating, and inspecting the related components.
• Complexity : The moving parts and additional mechanisms in a centerboard system can be more complex than a fixed keel, potentially increasing the likelihood of mechanical issues.
• Reduced interior space : Depending on your sailboat's design, the presence of a centerboard trunk may limit the available interior space, impacting your comfort and storage options.

The swing keel is a type of sailboat keel that essentially pivots on a hinge or bolt, allowing the keel to swing up or down as needed. This feature grants a sailboat with a swing keel the ability to adjust its performance and stability depending on the sailing conditions or water depth. Let's discuss the pros and cons of swing keels in detail.

Pros of swing keel

Versatility : The swing keel's ability to pivot grants your sailboat the capability to navigate shallow waters and safely beach your boat without getting stuck. This is advantageous for exploring coastal areas and coves.

Adjustability : Swing keels provide the opportunity for better control over your boat's performance. By adjusting the keel angle, you can find the right balance of stability and speed tailored to your sailing experience and conditions.

Trailerable : A sailboat with a swing keel can be easily trailered and transported, as the keel can be retracted, reducing the boat's weight, draft, and overall dimensions.

Ease of maintenance : Swing keels are often easier to maintain and repair, as they can be retracted for inspection or servicing without having to haul out the entire boat.

Cons of swing keel

Reduced performance : A trade-off with the swing keel's versatility is that it generally doesn't offer the same level of performance as a fixed keel sailboat, especially when it comes to upwind ability or pointing.

Additional complexity : The presence of a pivot point and moving parts can make swing keels more prone to wear or damage. This can lead to additional maintenance requirements or repairs if not properly cared for.

Increased weight : Given the swing keel's construction, materials, and additional hardware, it can add extra weight to your boat compared to other keel types. This may affect your boat's overall performance.

Potential leaks : Like any keel with moveable parts, a swing keel can introduce the risk of water ingress if the seals or hull are not properly maintained.

Pros of wing keel

The wing keel is an innovative design that has gained popularity among sailors due to its unique features and benefits. One of the main advantages of this keel type is its shallow draft . The horizontal wing allows the keel to have a larger surface area without going as deep as a fin keel of the same size, making it ideal for sailboats navigating shallow waters.

Another benefit of the wing keel is its relatively good upwind performance . While not as efficient as a fin keel, it still performs well in many sailing conditions, offering a great balance between maneuverability and stability.

The ease of grounding and recovery is another plus for the wing keel. Since it has a relatively shallow draft, you are less likely to hit the seabed when navigating shallow waters. Furthermore, if the boat does become grounded, the wing keel design makes it easier to refloat.

Cons of wing keel

However, the wing keel is not without its drawbacks. The most notable disadvantage of this design is its reduced pointing ability compared to fin keels. The wing keel may struggle to sail as close to the wind as a similarly-sized sailboat with a fin keel, which can be a disadvantage when racing or sailing in tight spaces.

A wing keel sailboat may also be prone to increased leeway due to the lower depth and surface area of the keel. This can make the boat more difficult to control in strong winds or challenging sea conditions.

Another issue to consider is the maintenance and cleaning of the wing keel. Due to the horizontal wings, it may be harder to access and clean the keel properly, leading to increased fouling or potential damage.

Bilge keels are an interesting combination of two smaller keels mounted on either side of the hull, which provide stability and added performance benefits in certain conditions. In this section, we will explore the pros and cons of bilge keels on sailboats.

Pros of bilge keel

• Shallow draft : Bilge keels allow you to access shallow water areas, expanding your cruising options. The dual keel design keeps your boat stable in shallow waters, making it ideal for exploring remote destinations, such as tidal estuaries or hidden coves.
• Low maintenance : Compared to other keel types like fin keels or lifting keels, bilge keels require less maintenance. They are sturdy and simpler to maintain due to their fixed position.
• Self-righting : With bilge keels, your sailboat has a natural ability to self-right after a capsize. Their wide footprint provides additional support and stability, reducing the chances of a full capsize.
• Beaching ability : Bilge keel boats can safely dry out on the beach or tidal flats without tipping, making it easier for you to conduct maintenance or give the hull a thorough clean.

Cons of bilge keel

• Reduced performance : While bilge keels offer stability and shallow draft benefits, they can reduce your sailboat's performance in certain conditions. They create more drag, causing your boat to be slower and less agile than boats with fin keels.
• Heeling angle limitations : Due to their wide footprint, bilge keel sailboats experience a larger heeling angle, which could make sailing at high speeds or in strong winds challenging.
• Less upright stability : Bilge keel boats may be less stable when sailing in extreme conditions, as the dual keel design provides less leverage for the boat to lean on compared to a deep fin keel.

Pros of daggerboard

A daggerboard can enhance your sailing experience in several ways. First and foremost, it provides improved maneuverability . With a daggerboard, you can navigate through shallow waters more easily, making it ideal for exploring coastal areas and inland waterways.

Another advantage is the ease of maintenance . Daggerboards are simpler in design compared to other keel types, making them easier to maintain and repair. Additionally, they are easily retractable, allowing you to adjust the draft of your sailboat depending on the depth of the water, avoiding running aground or hitting underwater obstacles.

Daggerboards are also typically lighter in weight compared to other keel types, which contributes to better sailing performance, particularly in light wind conditions. It is also worth noting that their simple design often results in lower production costs for boat manufacturers, resulting in more affordable options for you, the buyer.

Finally, daggerboards are popular on trailer sailers due to their retractable nature, making it more convenient for you to transport your sailboat on a trailer over land when necessary.

Cons of daggerboard

Despite the various advantages, there are a few downsides to consider when it comes to daggerboards. One notable drawback is their limited righting moment . This means that sailboats with a daggerboard are generally less stable and more prone to heeling or even capsizing in rough conditions. If you frequently sail in choppy waters, this could be a significant concern for your safety.

Another downside is the space occupied by the daggerboard case inside the cabin of the boat. This can reduce the available living space, especially on smaller sailboats. In addition, daggerboards can be noisier than other keel types when sailing due to water noise around the daggerboard case.

Lastly, the lack of keel protection in boats with daggerboards makes them more vulnerable to damage by underwater obstacles. While the retractability feature might mitigate this risk somewhat, it is still essential for you to remain cautious when navigating shallow and uncharted waters.

Pros of fixed keel

A fixed keel offers numerous advantages that can make your sailing experience more enjoyable. First, fixed keels provide better stability as they have a lower center of gravity, resulting in a more comfortable ride. This is particularly beneficial when sailing in rough weather or choppy seas.

Moreover, fixed keels offer improved upwind performance compared to other keel types. The deeper draft allows the boat to generate more lift and point higher into the wind, making it faster and more efficient when sailing upwind. Additionally, these keels are low-maintenance since there are fewer moving parts to wear out or require replacement.

Lastly, fixed keel boats tend to have better handling under power . They can make precise turns and handle well in reverse, allowing for easier maneuvering in tight spaces and marinas.

Cons of fixed keel

Despite their advantages, fixed keels also come with some drawbacks. One of the main concerns is their depth , which limits the boat's ability to access shallow waters. This may restrict your sailing options, especially near shorelines or in tidal areas.

Additionally, fixed keel boats can be less maneuverable at slower speeds compared to boats with swing keels or centerboards. This can make tight turns more challenging, especially in crowded harbors or narrow waterways.

Finally, fixed keel boats are generally heavier and harder to trailer , as they require a higher towing capacity and specially designed trailers to accommodate the boat's deeper draft. This added weight can make transportation more difficult and lead to higher fuel costs for road transportation.

Pros of lifting keel

A lifting keel is a type of keel that can be raised or lowered, allowing you to adjust the depth and balance of your sailboat. When properly utilized, a lifting keel can provide a number of benefits to enhance your sailing experience.

• Versatility : A lifting keel allows you to sail in shallow waters as well as access ports and harbors with limited depth. This is especially useful for exploring coastal areas and navigating tidal waters.
• Improved performance : By adjusting the depth of the keel, you can optimize your boat's performance in various sailing conditions. This can result in better speed, stability, and upwind performance.
• Easier transportation : With the ability to raise the keel, transporting your sailboat on a trailer becomes more manageable as it reduces the overall draft and height of your boat.

If you're choosing between swing or lifting keel , here's our more detailed guide on their pros and cons.

Cons of lifting keel

While a lifting keel offers several advantages, it is essential to be aware of some potential drawbacks before choosing this type of keel for your sailboat.

• Maintenance and complexity : Lifting keels typically require more maintenance due to the moving parts involved. Extra care is needed to inspect and maintain the keel's lifting mechanism, which might include a winch, cable, or hydraulic system.
• Added weight : The lifting mechanism adds weight to your boat, which can have negative effects on performance and fuel efficiency.
• Potential weaknesses : The structural integrity of a boat with a lifting keel can be compromised if it is not designed and engineered properly. This could lead to stress points or even failure in extreme situations.

Pros of T-keel

T-keel is a unique design that has its advantages to consider. First, it offers improved stability . With a heavier weight concentrated at the bottom of the keel, your sailboat will resist heeling, maintaining a more upright position in strong winds. This added stability allows for better control and a smoother ride when sailing.

Another pro of the T-keel is its powerful upwind performance . The shape and design of this keel allow for a low center of gravity while minimizing drag. This combination helps your sailboat efficiently point into the wind, allowing for a quicker upwind speed. This increased performance can make a difference when racing or navigating through tight spaces.

Cons of T-keel

However, T-keels are not without their drawbacks. One potential downside is that T-keel boats tend to have a larger draft than other types of keels, meaning they require deeper water for sailing. This can restrict your ability to sail in shallow waters around bays or near shorelines, limiting your access to certain areas.

Another drawback of T-keels is that they can be more prone to grounding due to their design. If you accidentally run aground or hit an underwater object, the T-keel may be more likely to experience damage or become difficult to dislodge. This can lead to costly repairs or complications when trying to free your sailboat.

The Scheel Keel is a unique keel type that was designed by naval architect Henry Scheel in the 1970s. This keel offers a compromise between performance and stability, making it a popular choice for many sailboat owners. In this section, we'll discuss the pros and cons of the Scheel Keel to help you decide if it's the right choice for your sailing needs.

Pros of Scheel keel

Shallow draft : One of the main advantages of the Scheel Keel is its shallow draft. This allows you to navigate in shallower waters, making it easier to access more anchorage spots and enjoy cruising in coastal areas.

Stability : With its wide, flat bottom, the Scheel Keel provides good stability, making your sailboat feel more secure and comfortable in various conditions. This can be especially beneficial for less experienced sailors or those who prefer a more stable ride.

Efficient upwind performance : The Scheel Keel is designed to improve upwind performance without sacrificing stability. This means you can sail more efficiently and at a better angle to the wind, which can be a noticeable advantage in many sailing situations.

Cons of Scheel keel

Potential for decreased speed : Due to its wide, flat bottom, the Scheel Keel can create more drag, which may decrease your overall speed in comparison to other keel types. While the Scheel Keel offers improved upwind performance, it may not be the best choice for you if maximizing speed is your primary concern.

Maintenance : The unique shape of the Scheel Keel can make it more susceptible to damage, particularly if you frequently sail in shallow waters or near shorelines with rocks and other hazards. As a result, you might need to pay closer attention to the maintenance and repair of your keel.

Limited availability : While many sailors appreciate the benefits of the Scheel Keel, it's not as widely available as some other keel designs. This could make it more difficult for you to find a sailboat with a Scheel Keel or to have one retrofitted to your current boat.

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Keel types – full, deep fin, bulb, wing, centerboard, canting.

A keel balances a monohull in the water. The keel is a large flat shape with a aerodynamic leading edge. They come in six general variations: full, fin, bulb, wing, centerboard, and canting.

Full A full keel by definition runs the length of at least 50% of the hull. The forward edge curves vertically while the aft edge often connects to a rudder. The main advantage of a full keel are safe grounding and directional stability.

Safe grounding means a full keel is safer when you lie on hard ground. Whether along the coastline or in travel lift slings, the full keel provides a strong, stable balancing point for the hull. A full keel boat will not tip on its bow or stern. When you ground then, the boat will lay on her side in shoal water and take less damage. In a travel lift, the full keel is easier to sling with the longer keel line. Blocked up on the hard, the full keel provides a line of balance. Be it an unintentional or intentional grounding, a full keel has more stability.

A full keeled boat points well when in the water. It has good directional stability. Put the boat in a compass direction and with a properly designed full keel is likely to stay pointing in that compass direction. The full keel has longer waterline length so controls the flowing water more than shorter keels. The water rushes by for a longer distance and smoother flow. Turbulence is less likely to generate forces to twist the boat. The full keeled boat is less likely than a fin to fall off because this smoother flow. The boat has greater directional stability than a fin.

Fin By a fin, I refer to a simple deep keel that’s length is less than 50% of the hull. The fin is flat and sharp edged, shaped like a shark fin. A fin keel is fast. The fin keel has less wetted surface area than fuller keels and drafts more. The deeper draft makes the boat sail great. In general, the deeper a sailboat drafts, the faster she is. For racing and performance cruising, the fin keel is king. Reading threads in Sailnet, you’ll see Jeff_H as a great proponent. His articulate posts are worth a postmodernist’s read.

Bulb The bulb is a shoal draft fin keel. Basically, you saw off a deep fin keel and attach a torpedo shaped bulb of lead to the keel bottom. This shallower keel is a compromise between the performance of a fin but the realities of cruising in the Bahamas, Cheasapeake Bay, and other shoal water holes. Often makers these days produce shoal and deep versions of their designs. Hylas, Valiant, and Tayana come to mind. If you plan to sail in shoal waters, they recommend a bulb keel but otherwise you will enjoy the deep fin keel. As a side benefit if you do ground on a soft bottom and sink in, the bulb keel is the easiest to free. The bulb does not stick way down into or catch the muck like other designs. The bulb at the bottom plops out easily.

Wing The wing is another shoal alternative to the deep fin. Instead of one bulb at the keel bottom, the wing has two bulbs laterally offset and connected via lead airplane wings. Or the wing is a thick foil of lead without bulbs. The wing has better performance than the bulb because she reduces tip vortex turbulence. The draft can be even less. Because the two bulbs are offset they do not mess with the leading keel edge and generate turbulence like a simple bulb keel. As a drawback, the wing is the most difficult to free if you slide into muck. The wings have a way of gripping down into the bottom. Wing keels are seen on Catalinas and Irwins.

Centerboard Another shoal idea is the centerboard. The centerboard keel has a base keel with a dagger than rotates downward. When the water is deep, you stick the centerboard down. When shoal, you sail centerboard up. You get the performance of a deep keel and the manuverability of the shoal – a perfect idea, right? The drawback is maintenance with the centerboard. As with any moving part, problems arise. The centerboard has to be maintained.

Canting The latest and oddest in performance is the canting keel. A canting keel mounts on a hinge and when the boat heels, racers hydrolically rotate the keel to windward. Rotating the keel away from your heeling direction, generates force which both rights the boat and propels her forward. The downside is the maintenance and complexity associatied with the canting keel. It is the future for racing but not perfected yet. I saw the 65 Windship, Procyon, of the Harken brokers which has a canting keel (and bipod mast to boot). “How do you like the whole canting keel thing?” a fellow broker asked. “It’s great. Oh boy is she fast.” The owner loves the canting keel but of course there are downsides of maintenence and the inherent risk of failure with any complex system. Every sailboat decision is a trade-off.

Conclusion The main types of keels are the full, deep fin, bulb, wing, centerboard, and canting. The full is the oldest and slowest while the canting is the newest and most complex. In general, the bulb, wing, and centerboard are compromises on a deep fin to allow for shoal water cruising.

4 Replies to “Keel Types – Full, Deep Fin, Bulb, Wing, Centerboard, Canting”

1.) Why not make a canting bulb/wing keel? 2.)Alternatively: bilge keels could be added as is apparent in the above picture: canting bulb/wing keel + bilge keels. 3.) Fixed bulb/wing + bilge keel

Somebody could clinch a thesis on hydrodynamics by quantifying the results of these various combinations.

1.) Why not make a canting bulb/wing keel? Canting keels generally are bulb keels. The concept of a canting keel is to get as much of the ballast weight to windward as possible. Typically, below the hull a canting keel consists of a strut and a bulb. The strut is generally made as light as possible, while the bulb is made as heavy as possible. The bulb is typically shaped to minimize drag while getting the ballast as low as possible. Typically this is a flattened torpedo shape.

There is no reason to combine a canting keel with a wing keel. Conceptually, wing keels generally are about increasing lift while minimizing vortex induced drag. Since the canting keel does not act as a foild providing resistance to leeway,adding a wing would do very little, but also wings are very sensitive to having a proper angle of attach and the nature of a canting keel is that the angle of attach would vary widely.

2.)Alternatively: bilge keels could be added as is apparent in the above picture: canting bulb/wing keel + bilge keels. Canting keels are generally combined with dagger boards which are angled outboard and which are raised and lowered on each tack. These dagger boards are the foils which provide the lift resisting leeway. These are generally not part of the ballasting system. If they were fixed in place, the added drag of having two foils, plus the canting keel would offset the advantage of a canting keel except in higher wind conditions.

3.) Fixed bulb/wing + bilge keel Again, the whole driving force with keel design is to maximize resistance to heeling, and maximize lift while minimizing drag within the intended draft of the vessel. Bilge keels generally start out with a lot of drag for the amount of lift and stability that they produce. Their sole advantage has nothing to do with sailing ability, as much as it does with produce a shallow draft boat that stand on its own legs when the tide runs out.

Adding a fixed bulb or wing keel to bilge keels would only increase the drag and would add minimal lift due to the interference to the flow caused by the turbulence of the three foils on each other when operating in close proximaty.

Somebody could clinch a thesis on hydrodynamics by quantifying the results of these various combinations. Not Likely

I would strongly disagree with the Conclusion above. While it is true that full keels are the oldest form of a keel, it is a big mistake to think they offer more stability than a bulb keel. In a general sense, a properly designed bulb keel locates its ballasting more efficiently than most full keels. In practice, pound for pound the righting forces are enormous for the average bulb keel as compared to a typical full length keel. I would also somewhat disagree with the generalization that a bulb keel is a compromise on a deep keel to allow for shoal water cruising. Bulb keels optimize righting moment for a given draft which is why bulb keels are the current norm for deep draft race boats as well as shallower draft performance boats.

You also do not address keels with cut away forefoots, and forward placed stern posts that were so common during the CCA era. These offer almost none of the virtues of a full keel or fin keel, with almost all of the liabilities of both.

Respectfully, Jeff

I am about to turn 77. I have sailing experience from age 6 to 18 on a 12 sailing pram with a 17′ mast and 100sq’ of sail that my dad built and have not sailed since. I am looking to find & buy a 28′ to 40′ sloop with all the trimmings from wheel steering to radar and a dingy, all in good working order and at less than $10,000. It is my plan to sail her in the Caribbean until we get used to each other and then up to Nova Scotia & then either east to the Mediterranean or west around Canada to the Pacific where I would love to sail her for the rest of my life. Yes this is a pipe dream but before I had enough to buy this dream I found over 150 online that fit my parameters. Now I have the cash for her & I can limit my choices to the very best deals. I realize there is a sailing and navigation course or 2 to be done before I attempt this and in addition I do have a few questions.

My questions are these – furling foresail — yea or nay furling mainsail — yea or nay best all around type of keel ? Deisel or gas inboard Radar – yea or nay solar &/or wind electric generation

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What are the pros and cons of different keels?

We all sail for different reasons, in different cruising grounds and use our yachts differently, so it makes sense that there is no one-size-fits-all keel design. At Sirius, however, we like to make the perfect yacht for each individual owner. One of the ways we serve our customers is our choice of keels – at least six different options for each model. It’s one of the ways we stand out – or should that be stand up?

We offer three styles of keel: fin, twin and lifting swing keel. All of our keels excel in many ways, but every design does have drawbacks – this is not unique to Sirius, but the keel affects the way you use the boat, so it’s important to choose the right one for you.

These are the keels we currently offer:

Standard Fin (310 DS, 35 DS, 40 DS) Performance Fin (310 DS, 35 DS, 40 DS) Medium Fin (310 DS, 35 DS, 40 DS) Shallow Fin (310 DS) Shallow Twin (310 DS, 35 DS, 40 DS) Performance Twin (35 DS, 40 DS) Lifting Swing Keel (310 DS, 35 DS, 40 DS)

Does the choice of keel compromise ocean capability?

For Sirius yachts, absolutely not. It’s important to realise that choosing one keel style over the other does not affect the yacht’s righting moment or compromise its ocean-going capabilities at all!

Whichever keel you choose, deep or shallow, twin or fin, they all have the same stability. This is achieved by putting more weight in the bulbs of the shallower keels as the shorter lever can be balanced with higher weight. Most of the blue water cruising and circumnavigations in Sirius Yachts have been made with twin-keel or reduced/shallow fin keel yachts.

Does keel choice affect performance?

As our shallow keels are heavier the weight dampens the yachts’ motion at sea, but as a downside, you have more weight to move with sails or engine. Once you’re moving there isn’t a difference but when tacking or gybing, or when not steered well, you will lose a bit in sailing performance. The shallower draught yachts also lose a few degrees to windward compared to their deeper keeled sisters, but they are still good all-round performers. Our customers with racing backgrounds always try to go for a keel as deep and light as their sailing area permits, either with a single or twin keel.

Pros and cons of fin keels

The standard keel on our yachts is a fin keel. Most sailing boats today use a fin keel because it gives a good all-round performance on all points of sail. By keeping the ballast lower it gives the most comfortable motion. The main downsides are that the draught (the depth of water required to stay afloat) is the greatest, and it’s very important to avoid running aground on a falling tide. Fin keel boats cannot dry out without additional support, either from a harbour wall or by fitting a pair of beaching legs. Some fin keel yachts are not built strongly enough to stand on their keels when out of the water, so they can’t dry out alongside a harbour wall and they need to be kept in a special cradle when stored ashore to avoid the risk of the hull deforming under its own weight. By contrast, all Sirius yachts can stand on their keels for any length of time with no problem at all.

We offer four types of fin keel. The standard fin is available on the 310 DS, 35 DS and 40 DS and is fully cast-iron. It offers the best value, good performance, and excellent responsiveness. It is the deepest of our fixed-keel options, so if you want less draught you may want to look at our other fin keels.

We also offer a performance fin keel for all our models. This uses a cast iron fin with a lead bulb at the tip (bottom). The structural strength of cast iron means the fin is the slimmest profile, but lead is denser than iron so the same volume of lead will weigh around 1.4 times more than cast iron, giving more righting moment. The heavier, softer lead down low has less volume in the bulb so achieves a slimmer profile with less drag and therefore better performance.

A lead bulb is also safer if it hits something. Lead can absorb 60% of the energy in flexing and deformation so that only 40% of the force will be transferred to the laminated structure of the keel reinforcement. A lead bulb is very forgiving and easy to reshape and will not start to rust where the coating is damaged. We can use less volume of lead than iron, and achieve better stability than a wholly cast-iron keel. We can also reduce the depth of the keel and retain excellent stability. However, lead is more expensive than cast iron and the bulb must be attached very securely to the iron fin, so this option does cost more.

If you want less draught, we also offer a medium fin. This reduces the draught of the 310 DS and 35 DS by around 40cm/1ft 4in and 55cm/1ft 9in on the 40 DS. Like the performance fin, it uses a cast iron fin with a lead bulb. To retain the keel’s grip in the water it has to have a longer chord (the distance from fore to aft). While this gives the boat better directional stability, it does make her a little less responsive and a little slower to manoeuvre.

On our 310 DS, we offer a shallow fin option – a special version for very shallow cruising grounds. This fin keel offers the least draught of any of our fixed keel options at 1.15m/3ft 9in and draws 10cm/4in less than the twin keel version. The keel has a significantly longer chord (2.24m/7ft 4in compared to 0.7m/2ft 3in of the standard keel) so she has the reassuring directional stability of a long-keeled yacht but with better manoeuvrability.

Pros and cons of twin keels

Our twin keels are the most popular option. About 70-80% of all Sirius Yachts are delivered with them – and on the 40 DS it’s 90%. Some folk still believe there is a big performance penalty with twin keels. In the past this used to be true but it’s no longer the case with modern twin keel designs, from Sirius at least. We have conducted many two-boat comparison tests, often battling for hours, by ourselves, with owners, and for sailing magazines and we have found that there may only be one or two boat lengths of difference at the end of a long windward leg, if at all. At the end of many of these comparison tests, the crews could not point out which of the boats had the twin keel.

If you cruise tidal areas, twin keels will reward you time and time again. Not only do they give you a shallower draught than the typical fin keel, they also give you the ability to dry the yacht out, whether that’s for a motion-free night’s sleep, to explore cruising grounds others cannot reach, or just for cheaper mooring and maintenance costs.

We offer two styles of twin keels; performance and shallow draught. Both options have a cast iron fin with a lead bulb. The performance keels have a deeper draught and a thinner chord so they act and feel a bit livelier when sailing and manoeuvring. The shorter keels have a longer chord, but give you the ability to navigate shallower areas. Like all keel designs, twin keels do have some downsides. They are more expensive than fin keels, and when you’re sailing fast in choppy seas at a steep angle of heel, you can occasionally get a slapping sound when an air pocket is caught and pressed out under the windward fin. Lastly, we’ve yet to meet an owner who enjoys antifouling between the keels. Thankfully it only has to be done once a year and with twin keels you might get away with doing it less frequently. A twin keel yacht can be kept on a drying mooring, where fouling is reduced because the hull spends more time out of the water. And when you’re off cruising it’s easy to give the bottom a quick scrub while the yacht is dried out.

Our yachts will happily sit on their keels on a hard surface, like a drying grid, or for winter storage but on softer surfaces we use the rudder for additional support. The rudders on our twin keel yachts are specially reinforced for this: we use a Delrin sheave to take the weight of the hull and the tip of the rudder has a wide, foil-like foot to spread the weight.

A lifting swing keel

We are one of a few manufacturers to offer a lifting swing keel. There’s a lot of confusion with the term ‘lifting keel’, it seems to encompass all yachts that have centreboards, variable draught, lift-keels or swing keels. To us, a lifting keel boat should have all the ballasted weight of the boat in the keel, and that keel needs to be retracted into the hull.

Technically, a lifting keel is a keel that can be lifted or lowered and gives the boat the ability to dry out when the tide goes out. A lift-keel is a ballasted keel that raises and lowers vertically. A swing keel has a ballasted fin that has a single pivot point and the keel swings up into the boat. There are other variants of design, for example some have a lifting keel to reduce the draught of the vessel but they cannot dry out on it, others have a ballasted keel and ballasted grounding plate. All these examples have a keel that does two things: keep the boat upright and stop her sliding sideways. Our swing keel is designed with a NACA profile to give the most efficient performance.

Centreboard yachts have a centreplate to provide grip in the water and reduce leeway. The plate may carry only 15-20% of the ballast but the rest of the yacht’s ballast is within the hull and/or in the grounding plate. This is called an “integral keel” and is more common as it’s less complicated to build. The lower a yacht’s ballast is located, the better her stability, the more comfortable her motion and the better she stands up to her sail area. The most efficient place for the ballast is as low down on the deepest keel possible – this is why race boats have deep skinny keels with large torpedo-shaped bulbs on the bottom, but they don’t make practical cruising sailboats.

Our keel designs have more weight in the tip (bottom) – using a bulb on the fin and twin keel design and flaring the lower sections on our lifting swing keel yachts. You don’t have this with centreboard and integral keel yachts.

It might be surprising, but a lot of owners come to us thinking that a lifting swing keel is the best option for them. Sometimes it is, but about 98% of customers who approach us because we offer swing keels end up sailing away on a twin-keel Sirius.

The downsides of a lifting keel

A lifting swing keel does give you more cruising options. It will lift should you run into something and, of course, it gives you the shallowest draught. But that difference is only 40-50cm (1ft 4in to 1ft 8in) less draught than our shallow twin keel option. The lifting keel increases the complexity of the build and the final cost of the yacht; it also sometimes limits the internal layout and engine drive options, and you need to have twin rudders too. Twin rudders make the boat less manoeuvrable in a marina – you can opt for a third central rudder which does improve the handling, but again comes at an extra cost.

On the lifting swing keel, 40 and 310 owners are restricted to the use of a shaft drive, which is less efficient and you have to accept a bit more noise and vibration. When drying out, the drive is more vulnerable to damage, whereas it’s totally clear when taking the ground on twin keels. With twin keels, you also do not have to worry about something sticking out of the beach or stones lying around because the hull is high above the ground. With the hull up high, you do not have to dig a hole in the sand and slide down on your stomach to check or change your anodes as you would on a swing keel.

Sailors who are attracted to the idea of a lifting swing keel should carefully consider the pros and cons to compromise the least. When owners understand the repercussions of choosing a lifting keel yacht, many of them feel it restricts their options too much. They could have a lifting keel or they can sail with twin keels, dry out, have better close-quarters handling and save money in the process. Unless you need the shallowest possible draught – 0.75m (2ft 5in) on the 310 DS, 0.9m (2ft 11in) on the 35 DS or 0.95m (3ft 1in) on the 40 DS – a twin keel might well be a better option.

How are the keels attached?

The design of the keel is important but the way they are attached is just as important, if not more so. All of our fixed keels are through-bolted. Every keel has a wide flange at the root (top) of the keel and the flange sits into a reinforced recess in the hull. The flange and the recess work together to spread the loads of the keel/s into the yacht’s hull. The keels are bonded and bolted to the hull. We use up to twelve 20mm and 24mm bolts (per keel) and these go through rolled stainless steel backing plates inside the hull to spread the bolt loads evenly into the fully laminated keel grid which goes all the way up to the chainplates and also carries the mast support.

For our lifting swing keel, we laminate a substantial keel box as part of the hull to accept the keel and the hydraulic mechanism needed to retract the keel into the hull. Unlike most other boatbuilders we don’t use a grounding plate to take the weight of the yacht, our yachts sit on the length of the leading edge of the keel. Integral keels with the majority of the ballast in the grounding plates move the ballast (weight) from low down in the keel to inside the hull. This negatively affects the stability as the more weight you have lower down, the better.

We also don’t like grounding plates because they bring the hull in contact with the ground. By leaving 10-15 cm (4-6in) of the keel out of the hull when it’s retracted, most of the time the hull is kept clear of the beach and anything that could damage it.

The problem with too much form stability

With only 15-12% of their ballast in the centreboard, most lifting-keel yachts cannot rely on keel weight for stability so their hulls need to be designed with extra form stability instead. This means the hull sections have to be much wider and flatter. A flat-bottomed hull is not what you want for a comfortable ocean cruising yacht; it isn’t sea-kindly or easy to steer in waves and gusty winds conditions. We don’t make that compromise at Sirius. With all the ballast in the swinging part of our swing keel design, we can use the same seaworthy, ocean-capable hull shape designed for our yachts with fixed keels.

If you don’t know which keel would be best for your Sirius, contact us to discuss the type of sailing you intend to do, where you want to sail and what your cruising aspirations are.

General Manager – Torsten Schmidt SIRIUS-WERFT GmbH Ascheberger Straße 68 24306 Plön/Holstein

Fax: 0049 – 4522 – 744 61-29

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What a bilge keel is good at, especially when cruising in large tidal areas. Note short rudder on skeg. Pic - Jon Neeves

Keels: Out of sight and out of mind

It is just a lump of stuff at the bottom of the hull: Cruising Helmsman contributor Jon Neeves discusses how important the keel is.

It may be odd but, potential buyers sitting on a demonstrator yacht at a boat show will look at the rig, the galley, the size of the wheel. But it is seldom that anyone enquires of the keel.

The only question asked of the keel relates to draft. Keels invoke so little interest some yacht brochures do not even show any image of  them at all. We can thank an Australian, Lexcen or Miller, as having brought keels into international public focus with his (and/or Oossanen and Sloof’s) winged keel for Australia II.

So, given Australia II’s winged keel brought so much advantage to the yacht, it is strange keels are, again, yesterday’s hero.

Traditionally keels many decades ago were full keels and built as part of the hull. Full keels, by definition run 50 per cent of the length of the hull, are seldom seen today and very seldom in Australia. But a local and delightful example would be the Noakes’ restored 80-year-old Maluka.

The main advantage of a full keel for a cruising yacht is that the keel imparts very good directional stability. Set a course and a well-designed, full keeled yacht will hold that course. At anchor full keeled yachts tend to be more stable and do not yaw and veer with normal variability in wind direction. Full keels also impart strength, advantageous if you run aground.

The downside is that the full keel imparts greater wetted surface area and this means less speed. A more modern interpretation of the full keel is a long fin keel, which usually would have reduced surface area compared to an old fashioned full keel but still maintaining that directional stability. Both forms tend to have the rudder incorporated as part of the keel, or with a protective skeg ahead of the rudder.

Even long fin keels are not much seen in Australia. An enduring example of a production full keel yacht would be the Fisher 34 or 37/38 built in Mona Vale Sydney some years ago, with a number of well-kept examples sailing today.

Full keel yachts tend to accept heavy weather readily because they were built more solidly: using wood, steel or lots of fibreglass. Fin keels are not new, Herreshoff pioneered the use for inshore racing at the beginning of  the 20th century.

But it appears the advent of the fibreglass production yacht almost signalled the end of the full keel and the popularity, at least amongst boatbuilders, of the fin keel. Fin keels come in a variety of forms and the shape has slowly evolved, primarily as yacht designers have had access to better analytical tools.

One major advantage of the fin keel is the simple fact it can be detached, which makes shipping production yachts round the world much cheaper. This, obviously, is a major contributing factor in the popularity.

Fin keels today come in two basic forms: deep or shallow fin, with or without additional bulbs and wings. Earlier fin keeled yachts were sometimes built with bilge or twin, side by side, keels.

Bilge keels allowed yachts to dry out and remain upright but these tended to be restricted to smaller yachts, though there were larger ones. Increased access to marinas and enclosed marinas in areas with big tides, appears to have reduced the popularity amongst modern yacht builders. Bilge keeled yachts tended to heel more than the single keeled equivalents and tacked through larger angles.

Totally unrelated but multihulls are part of the bilge keeled yacht family with the ability to dry out. Multihulls also have keels to reduce leeway and these are either ‘sacrificial’ mini-keels that will rip off if you ground at speed, or daggerboards. Most cruising catamarans have mini-keels and catamarans with daggerboards that I have cruised with always keep the boards at least part way down to protect propellors and rudders from crab pot lines.

Permanent use of daggerboards appears to negate the use, you might as well have had mini-keels in the first place. Keels are critical to monohulled yachts: they balance the load on the sails so reduce or manage heeling; they reduce leeway, stopping the boat sliding to leeward; and they provide lift counteracting the sideways drive of the sails.

Sadly, monohull keels for cruising yachts are heavy, 25 to 33 percent of overall yacht weight. Plus they restrict the depth to where you can safely travel. Some yacht builders, such as Southerly the better known part of Northshore and Ovni with its alloy yachts, have addressed this shortcoming. The most extreme solution is the lifting keel, the complete keel lifts into a box, manually for smaller keels and hydraulically for larger, usually encased by the saloon table. This is a development that has not proven popular in Australia.

Parker in the UK, who build the International 505 have a 23’ yacht with a lifting keel. When the market was buoyant, they produced larger yachts some with winged lifting keels. Both Elliot and Young, from New Zealand, have had lifting keel designs. Both of these NZ designers also used a lifting keel to allow a yacht to be shipped in a standard shipping container, such as the current Farr 400.

A variant on the lifting keel was a centreboard. The centreboard is effectively a dagger that fits into a base keel and is offered by Jeanneau on some of its Sun Odyssey range. A full lifting keel provides real shoal draft in a monohull, similar to a multihull with mini-keels: 820 millimetre on the 38’ Southerly and 1009mm on its 58’ model; providing the ability to dry out.

These solutions seem neat but a minor problem is maintenance. Moving components, especially underwater, on yachts always generate problems. There have also been problems with fouling of the interior of the box causing the keel to jam.

The longevity of Ovni and Southerly, even in today’s current European economic climate with both brands being expensive, indicates some real success and acceptability. The common solution today to keel design is a shallow or deep fin. Often these are offered as options for the same yacht, sometimes described as a performance or racing keel and the shallower draft version a shallow draft or cruiser keel.

In reality the difference in draft is not great, maybe 300mm to 400mm for an 11m yacht. The difference in performance is marginal, imperceptible to someone cruising but more critical to someone racing. On tests on a 10m yacht the deeper (by 300mm) draft yacht had a 20 degree better tacking angle, less weather helm and heeled about 30 degrees less.

Interestingly, a lifting keel version of the same yacht performed as well as the shallow keeled version, with the bilge keeled version a bit of a dog. Deeper keeled versions of the same cruising yacht will sail better, though you might be pushed to tell the difference. But if your desired cruising area is shallow then a shoal draft keel would obviously be more sensible.

Yachts built specifically for racing have keels that might be considered as extreme, however you want to measure it! Investec Loyal/Maximus has a 20’ keel though the yacht itself is 100’ long. Compare that to the 6’ draft of most larger, around 45’, cruising yachts. Racing yachts also carry protruding torpedo shaped weights at the keel base, ideal for catching crab pot lines or sunfish.

While some racing yachts, when they reach the end of their performance careers, might be considered as the basis for a cruising yacht its keel might be more of a deadweight than intended. Not only state of the art racing yachts are built with protruding bulbs at the base of the keel, many yachts marketed for cruising carry the same sort of handicap. From personal experience a crab pot attached to a short-handed cruising yacht appendage at 2am is not a bundle of laughs.

Hanse’s 545 standard keel with forward protruding bulb, for example, has a whopping 9’ draft, is ostensibly sold as a cruising yacht with an interior to match. The Dufour 36 and Beneteau First range also market similarly keeled yachts, but do tend to brand them as performance or racing yachts.

The bulb at the bottom of the fin is the obvious design to enable maximum use of ballast to balance the sail plan: the lower the ballast the less you need carry, which is why racing yachts incorporate such designs. One well-known manifestation of this was the finned keel of Australia II, though technology has moved on. Bulbous bottoms, sometimes tending to fins, have been common on production yachts for a number of years with an enormous breadth of design.

More recently designs have converged. One reason wings lost favour for cruising yachts was their susceptibility to damage when grounding and when grounded, in mud or sand, a large flat bottomed keel was more difficult to free. But Jeanneau nowadays, use the shoal draft wing keel with twin rudders as a way to dry out; so the concept has reputable proponents.

A novel design departure was the tandem keel, two vertical fins with one long interconnecting weight, introduced by Warwick Collins. The idea was to combine shoal draft, ‘full’ keel advantages, a low centre of gravity and produce extra lift, the same as two sails do instead of only one. But the tandem keel has few supporters.

Superficially the tandem keel looks to be a winner, a long shallow keel providing shoal draft and good sea-keeping abilities, but there are obviously technical issues or it would be much more common. Full keels tended to be built hollow and filled with ballast, lead ingots, iron or steel ingots, scrap metal and cemented in place, space left over might be taken up by fuel and water tanks. Modern cruising keels are cast iron or steel with sometimes the inclusion of lead. Lead is 30 percent denser than steel and much more expensive.

Most modern racing yacht keels are built with high tensile steel fins with the ‘torpedo’ weight, sometimes lead but also steel, jointed and bolted, sometimes welded and a flange welded to the top forming a ‘T’ section to allow the keel to be bolted to the hull. Fin keels with a bulb at the bottom are technically the best way to design a keel, as it optimises righting moment or maximises resistance to heeling. Plus, if the fin is thin, minimises drag.

The downside from the cruising yacht point  of view is the thinner the fin the more protrusion of the crab pot catcher, the deeper draft and more sensitive directional ability of the yacht.

The very thin fin keels of the high performance racing yacht carry enormous loads and can be made from high tensile steels of the quality produced by the Australian company Bisalloy, coincidentally the same steels used by Manson and Anchor Right for the super high holding power anchors.

Ignoring canting keels, attachment of keels to hulls is by bolts, or studs, through a keel plate in the yacht. Simplistically, the keel is held vertically, the joint surface is liberally coated with marine sealant (FixTech or Sika Flex) the yacht lowered onto the studs in the keel and nuts tightened onto large washers, commonly pieces of stainless steel plate inside the hull and under the cabin sole.

There are two schools of thought regarding how the nuts should be tightened. Some hang the yacht in slings with the keel hanging, others allow the keel to take the full weight of the yacht. The former seems more logical as that is the normal attitude of the yacht in the water with the keel hanging without support.

Given the simplicity with which keels are attached, they are equally easy to remove, arguably more easily than removing the mast. Removing and rebedding a keel is not unknown.

For those who race the keel/hull joint might be faired with epoxy. Castings tend to be a bit rough and steel corrodes, so racing keels are coated and faired and sometimes additionally filled and faired by the owner. If you do ground on something hard and unforgiving it is important to slip the yacht and reseal any damage to the protective coating on the keel and check keel bolts for weepage.

Looking at modern cruise yacht keels from different production yacht builders: Bavaria, Hanse, Beneteau, Jeanneau etcetera, one thing that stands out is that the similarities are greater than any differences. This might explain why keels receive so little mention, they are too similar to differentiate.

Keels tend to have almost vertical leading edges, a tendency to a bulb at the bottom often flattened on the underside to lower the centre of gravity as much as possible, the bulb does not extend forward but does protrude aft of the trailing edge of the keel again keeping the weight low. Bulbs are ‘conventional’, they might have a flattened bottom but no fancy shapes and no fins.

Leading edges of the fin are elliptical and trailing edges narrow, almost to a sharp edge. This gives an indication of what yacht designers, who all have access to the same hydrodynamic data, think is today’s ideal. The optimum draft for a bluewater cruising yacht is 6’. Anymore and there are going to be many places worldwide that you cannot enter; given production yachts today are built for a world market – around 6’ is the limit.

But what is best for you?

Protruding bulbs can catch crab pots, but so too can a near vertical keel leading edge, so some ‘sweepback’ is advantageous. Too much sweepback, common 30 years ago, has been found to be less efficient but again anyone cruising is unlikely to notice. A long keel, fore and aft, will be much more stable when at anchor, but slower to sail. A deeper keel will be more sea kindly, but loses some of its advantage when you run aground in The Great Sandy Strait!

You need to decide what sort of sailing you do. Designers of modern cruising yachts try to make the compromises for you and usually offer two, or occasionally three, keel designs. The very deep draft racing yacht looks sexy and will undoubtedly be fast, but it is usually designed with the idea of crew on the rail.

If you are cruising the crew will be aft in the cockpit, making the yacht slightly stern heavy, so some of the advantage of the fast keel will be lost. Plus you might have the pot catcher and skittish anchored behaviour to contend with. An obvious question to ask: why the inclusion and the detail of racing yacht keels?

Look at the keel of Azurro, it is not much different to today’s cruising yacht keel. Today’s sweep back angles are not so pronounced and our bulbs are bigger but Azurro keels would not be out of place.

Think of Australia II’s winged keel and consider the Parker swing keel illustrated and even today’s shoal draft keel on the Jeanneau Sun Odyssey 379, these modern keels with wings have their genesis with Lexcen and yesterday’s racing yachts. So if performance racing keel technology eventually trickles down to cruising yachts what might we see in the future?

Future forecasts

Investec Loyal’s keel, the 2011 Sydney/Hobart winner, offers a new insight into keel fabrication. The fin is over 6m long, narrowing from 1.0m at the top to 0.7m at the base with an approximate twelve-ton bulb on the bottom, huge loads on such a fine fin. Unlike most, Loyal’s fin is fabricated: 20mm high tensile steel plates, welded, to form a flat hollow tube but including internal longitudinal fillets to add structural strength. The tube is glassed and faired, this makes it hydrodynamic and protects against corrosion.

At the base of the fin is a plate welded at 900 (i.e. it is flat) and this plate is bolted to the torpedo weight with 1.5 inch bolts. Loyal’s keel cants but if it were fixed it could be joined to the hull with a similar plate and bolt arrangement. This method of manufacture is quick and can be completed by anyone with the correct welding skills and, importantly, it works.

The alternative is casting, forging and/or machining; all of which require skills and equipment beyond most boat builders and much more time.

We are not going to see 6m fins but we are already seeing keels similar to today’s shapes, fabricated rather than cast and, as keels come full circle back to the old full keel, that hollow fin may well become the standby fuel tank. With thanks to Noakes and Dovell for sharing the detail on the keel of Investec Loyal.

Jon and his wife Jo have owned their Lightwave 35, Josepheline, for almost 10 years. They manage to get away most years for a long cruise of 3-5 months and more recently their chosen destination has been Tasmania’s west coat.

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