sailboat rudder keel

• Paddle Board

What Is a Sailboat Rudder? An Overview of Its Function and Design

Sailboats have been used for thousands of years to traverse water. They have undergone many changes and improvements over the years, and one of the essential components of a sailboat is the rudder.

Quick Facts

Understanding the Sailboat Rudder

The rudder is a vital component of a sailboat that plays a crucial role in steering and maneuvering the vessel. The rudder works by changing the direction of the water flow around it, which moves the boat in the opposite direction. Without a rudder, it would be impossible to navigate a sailboat effectively, especially in different water and wind conditions.

Components of a Sailboat Rudder

A sailboat rudder comprises several components, each with a unique function that contributes to the rudder’s overall effectiveness. The stock is the main vertical shaft that connects the rudder blade to the boat’s helm. It is usually made of stainless steel or aluminum alloy and is designed to withstand the forces exerted on the rudder during navigation.

The blade is the flat portion of the rudder that faces the water current and directs the water flow in the opposite direction to steer the boat. The blade is typically made of fiberglass-reinforced plastic or aluminum alloy and is designed to be lightweight and durable. Pintles and gudgeons are the two connections between the rudder and stern that allow for easy installation and removal of the rudder. Pintles are the vertical metal pins that fit into the gudgeons, which are the horizontal metal brackets attached to the boat’s stern.

Different Types of Rudders

There are several types of rudders used in sailboats, each with its advantages and disadvantages. Transom-mounted rudders are the most common type of rudder, and they are mounted on the stern of the boat. Skeg-mounted rudders are attached to a fixed fin called a skeg, which provides additional stability to the rudder.

Keel-mounted rudders are attached to the boat’s keel, which is the central structural element that runs along the bottom of the hull. Spade rudders are free-standing rudders that are not attached to any part of the boat and are commonly used in racing sailboats. The type of rudder used depends on the boat’s size, design, and intended use.

Materials Used in Rudder Construction

Rudders can be made from various materials, each with its advantages and disadvantages. Wooden rudders are the traditional choice and are still used in some sailboats today. However, they are relatively heavy and require regular maintenance to prevent rot and decay.

Aluminum alloy rudders are lightweight and durable, making them an excellent choice for racing sailboats. Stainless steel rudders are also durable but are heavier than aluminum alloy rudders. Fiberglass-reinforced plastic rudders are the most common type of rudder used today, as they are lightweight, durable, and require minimal maintenance.

The sailboat rudder is an essential component that plays a crucial role in steering and maneuvering a sailboat. Understanding the different types of rudders, their components, and the materials used in their construction can help sailors choose the right rudder for their boat and navigate more effectively in different water and wind conditions.

The Function of a Sailboat Rudder

Steering and maneuvering.

The primary function of a sailboat rudder is to steer and maneuver the boat. The rudder’s blade directing the flow of water in a specific direction allows for the steering of the boat as the blade changes direction. Sailors can use the rudder to turn the boat in any direction they choose, allowing them to navigate through narrow channels or around obstacles in the water. It is essential to note that the rudder works in conjunction with the sails to control the boat’s direction and speed.

Balancing the Sailboat

The balance of the sailboat is critical to ensure safe maneuvering, and the rudder plays a crucial role in achieving this. A balanced rudder helps in keeping the boat steady, reducing drag, and preventing unwanted turning. Sailors can adjust the rudder’s angle to keep the boat balanced and on course, especially in rough water conditions. A well-balanced rudder also helps to reduce the risk of capsizing or losing control of the boat .

Rudder Effectiveness in Different Conditions

Rudder effectiveness varies depending on the boat’s size, weight, and water and wind conditions. A larger boat may require a bigger rudder for proper maneuvering, while a smaller boat can work with a smaller rudder. Sailors must also consider the water and wind conditions when choosing the right rudder for their boat. In calm waters, a smaller rudder may be sufficient, but in rough water, a larger rudder may be necessary to maintain control of the boat. Additionally, the rudder’s effectiveness can be affected by the boat’s speed, with higher speeds requiring more significant rudders to maintain control.

It is also important to note that the rudder’s effectiveness can be impacted by external factors such as weeds or debris in the water. These factors can reduce the rudder’s ability to steer the boat and require sailors to make adjustments to maintain control. Additionally, the rudder’s effectiveness can be impacted by the sailor’s skill level, with more experienced sailors able to make more precise adjustments to the rudder to control the boat’s direction and speed.

Design Considerations for Sailboat Rudders

Sailboat rudders are an essential component of a boat’s steering and maneuvering system. A well-designed rudder can make all the difference in a boat’s performance , especially in challenging weather conditions. In this article, we will explore some of the key design considerations for sailboat rudders.

Rudder Size and Shape

The size and shape of a rudder play a crucial role in determining its effectiveness in steering and maneuvering a boat. A larger rudder provides more leverage and maneuverability, allowing the boat to turn more sharply. However, a larger rudder may also produce more drag, which can slow down the boat’s speed.

The shape of the rudder is also important. A well-designed rudder should be streamlined to reduce drag and turbulence. The thickness of the rudder should be carefully considered to ensure that it is strong enough to withstand the forces exerted on it while remaining lightweight.

Rudder Placement and Configuration

The placement of the rudder on the boat can significantly affect its performance. A rudder that is too far forward can cause the boat to become unstable, while a rudder that is too far aft can make it difficult to steer. The location of the rudder must also take into account factors such as the propeller’s placement and the boat’s shape.

The configuration of the rudder can also determine its effectiveness and balance. A single rudder is the most common configuration, but some boats have twin rudders to provide more steering control. The angle of the rudder blade can also be adjusted to optimize its performance.

Hydrodynamic and Aerodynamic Factors

The design of a rudder must take into consideration the hydrodynamic and aerodynamic factors affecting the boat’s performance. Hydrodynamic factors include water flow, pressure, and turbulence, which can significantly affect the rudder’s performance. The shape and placement of the rudder must be carefully designed to minimize these effects.

Aerodynamic factors consider the wind and air resistance’s impact on the boat’s performance. The rudder’s size and shape must be designed to minimize the wind’s effect on the boat while providing sufficient steering control.

The design of a sailboat rudder is a complex process that requires careful consideration of many factors. The size and shape of the rudder, its placement on the boat, and its configuration must be optimized to provide effective steering and maneuverability. By taking into account the hydrodynamic and aerodynamic factors affecting the boat’s performance, a well-designed rudder can significantly improve a sailboat’s overall performance.

Rudder Maintenance and Repair

The rudder is a crucial component of any sailboat, providing steering and control. As such, it’s essential to keep it in good working order through regular maintenance and inspections.

Inspecting Your Rudder

Regular inspection of the rudder is essential to ensure its continued performance and longevity. A thorough inspection includes checking for cracks, wear and tear, and loose components such as hinges, pins, and screws. It’s also important to check the rudder’s alignment and ensure it moves smoothly and without any obstructions.

During your inspection, be sure to check for signs of corrosion, particularly on metal components. Corrosion can weaken the rudder and cause it to fail, so regular cleaning and maintenance are essential to prevent this.

If you notice any issues during your inspection, it’s important to address them promptly. Small cracks or damage can often be repaired, but if the damage is extensive, it may be necessary to replace the rudder entirely.

Common Rudder Issues and Solutions

One common issue with rudders is corrosion, particularly on metal components. Regular cleaning and maintenance help prevent corrosion and ensure the rudder’s longevity. If you do notice signs of corrosion, it’s important to address it promptly to prevent further damage.

Another common issue is damage to the blade or stock. This can be caused by impact with debris or other boats, or simply wear and tear over time. If the damage is minor, it may be possible to repair the rudder. However, if the damage is extensive or compromises the rudder’s structural integrity, it may be necessary to replace it entirely.

Loose components such as hinges, pins, and screws can also cause issues with the rudder. These should be checked regularly and tightened or replaced as needed.

When to Replace or Upgrade Your Rudder

Sailboat rudders can last for many years, but at some point, replacement or upgrade may be necessary. This includes upgrading to a newer design or larger rudder to improve the boat’s performance or replacing a damaged or worn-out rudder that is beyond repair.

If you’re considering upgrading your rudder, it’s important to consult with a professional to ensure that the new rudder is compatible with your boat and will provide the desired performance improvements.

Regular maintenance and inspections are essential to ensure the continued performance and longevity of your sailboat’s rudder. By staying on top of any issues and addressing them promptly, you can ensure that your rudder will continue to provide reliable steering and control for many years to come.

A sailboat’s rudder is a crucial component that helps steer and maneuver the boat safely. The size, shape, placement, and construction materials must all be taken into consideration when designing or replacing a rudder. Regular maintenance and inspection help ensure its continued performance and longevity.

Rudder FAQS

How does a sailboat rudder work.

A sailboat rudder works by changing the direction of the water flow past the boat’s hull, which in turn changes the direction of the boat. The rudder is attached to the stern of the boat and can be turned left or right. When the rudder is turned, it creates a force that pushes the stern in the opposite direction and turns the bow towards the direction the rudder is turned. This is how a rudder steers a boat.

What is a rudder and its purpose?

A rudder is a flat piece, usually made of metal or wood, attached to the stern of a vessel such as a boat or ship. The main purpose of the rudder is to control the direction of the vessel. It does this by deflecting water flow, creating a force that turns the vessel. Without a rudder, steering a vessel would be significantly more challenging.

Can you steer a sailboat without a rudder?

Steering a sailboat without a rudder is challenging but not impossible. Sailors can use the sails and the keel to influence the direction of the boat. By trimming the sails and shifting weight, it’s possible to cause the boat to turn. However, this is a difficult technique that requires a deep understanding of sailing dynamics and is usually considered a last resort if the rudder fails.

What controls the rudder on a sailboat?

The rudder on a sailboat is typically controlled by a steering mechanism, like a tiller or a wheel. The tiller is a lever that is directly connected to the top of the rudder post. Pushing the tiller to one side causes the rudder to turn to the opposite side. On larger boats, a wheel is often used. The wheel is connected to the rudder through a series of cables, pulleys, or hydraulic systems, which turn the rudder as the wheel is turned.

How do you steer a sailboat with a rudder?

To steer a sailboat with a rudder, you use the tiller or wheel. If your sailboat has a tiller, you’ll push it in the opposite direction of where you want to go – pushing the tiller to the right will turn the boat to the left and vice versa. If your sailboat has a wheel, it operates like a car steering wheel – turning it to the right steers the boat to the right and turning it to the left steers the boat to the left.

How do you steer a sailboat against the wind?

Steering a sailboat against the wind, also known as tacking, involves a maneuver where the bow of the boat is turned through the wind. Initially, the sails are let out, and then the boat is steered so that the wind comes from the opposite side. As the boat turns, the sails are rapidly pulled in and filled with wind from the new direction. This maneuver allows the boat to zigzag its way upwind, a technique known as “beating.” It requires skill and understanding of sailing dynamics to execute effectively.

John is an experienced journalist and veteran boater. He heads up the content team at BoatingBeast and aims to share his many years experience of the marine world with our readers.

What to Do If Your Boat Engine Won’t Start? Common Problems & How to Fix Them

How to launch a boat by yourself: complete beginner’s guide, how to surf: complete beginner’s guide to get you started.

Comments are closed.

Type above and press Enter to search. Press Esc to cancel.

Jordan Yacht Brokerage

We Never Underestimate Your Dreams

Sailboat rudder types – full, spade, skeg, outboard.

The four rudder types are: full, spade, skeg, and outboard. This article discusses the advantages and disadvantages of each.

Full The full or full keel rudder lies at the aft end of a full length keel. The keel-rudder streches along the entire length of the bottom of the hull. The full rudder is safe and nearly invulnerable to damage. The leading edge of the keel protects the rudder from flotsam. The full rudder is quintessential of offshore cruisers like Wetsails and Cabo Ricos. Even grounding may not cause damage. The boat will sit comfortable on its side until the tide returns and floats the boat back up.

Spade The spade rudder lies at the aft separate from the keel. A spade rudder is easy to turn because the water rushes both against its fore and aft edges – great for using a tiller. A spade rudder is also fast as the wet area less than a full keel. The boat racing along with less resistance. Spade and partial spades are becoming the most popular rudder type. The Hylas 70 has a partial spade rudder as well as early 54’s.

Skeg A skeg rudder is more modern in performance and safety. It is the most popular and common type of rudder on production boats these days. The rudder is fast and looks like a spade keel. Except, the skeg rudder has a fake keel which extends from the hulls aft and protects the fore edge. Most Hylas yachts have skeg rudders.

Outboard Outboard rudders are seen on smaller boats. They simply hang over the stern of the boat. For example, racing prams use outboard rudders. They are easy to fasion as emergency rudders. You can make one out of a handlerail and cabin door.

Conclusion A rudder is either full, spade, skeg, or outboard. Each type has its benefits. The most important part is make sure she is in good condition and have a spare.

4 Replies to “Sailboat Rudder Types – Full, Spade, Skeg, Outboard”

Ahoy Mateys, it’s Fox Axel the Pirate. I’ve got a swashbuckling yarn to tell ye. Me was drifting along way out at sea. Me had lost me steering while pillaging a friendly ship. The knaves canon knocked me rudder off. Me had nought to to turn to. The authorities would hang me, the villainous lot. But, me was getting desperate out of grub and rum, nothing to sage me drunken pirate ways. I had lost me last vestige of sanity.

Finally, me saw in the distance a giant whaler coming. The big ship sailed straight at me. “Ahoy mateys!” me spake. The freighter came near, too near. Shiver me timbers. The goulish crew must be drunk out of thee minds. Me could not steer away. She rammed straight slicing me ship in twain. Down to Davy Jones’ locker we went. Take care with ye rudders mateys – the Pirate of Monkey Isle.

Ok ye swabs ave a told me to finish me story. Ere dis da rest. As the freighter tore away leaving me to perish in the sea. I climbed on a board of driftwood from me sinkin’ ship. I passed out adrift, alone. When I came to, I found meself shipwrecked on a deserted island. I stumbled around and ran into, who of all? Big Red, me pirate enemy! Aye, I’m shipping as mate with his goulish fleet until I can betray and kill him. Aye, hope Big Red ain’t reading dis here blog. Black Fox the Pirate.

I am ye swab. I am too sharp for some ere fool like ye. I ain’t gots no book learning, but me hast carniving ways from many years below the mast. Iffen ye be trying to betray me, I am a gonna get ye.

Thank you for sharing this article.It’s quite easy to understand the difference.

Leave a Reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

INTRODUCTION TO SAILBOAT DESIGN: A TECHNICAL EXPLORATION

Sailboat design is a complex and fascinating field that blends engineering, hydrodynamics, and aesthetics to create vessels that harness the power of the wind for propulsion. In this highly technical article, we will delve into the key aspects of sailboat design, from methodology to evaluation.

1)     Design Methodology

Designing a sailboat is a meticulous process that begins with defining the vessel’s purpose and performance goals. It involves understanding the intended use, whether it’s racing, cruising, or a combination of both. Sailboat designers must also consider regulatory requirements and safety standards.

Once the design objectives are established, naval architects employ various computational tools and simulations to create a preliminary design. These tools help in predicting the boat’s performance characteristics and optimizing its geometry.

Design methodology also encompasses market research to understand current trends and customer preferences. This information is critical for creating a sailboat that appeals to potential buyers.

2)     Hull Design

The hull is the heart of any sailboat. Its shape determines how the boat interacts with the water. Hull design encompasses the choice of hull form, its dimensions, and the material used. The hull’s shape affects its hydrodynamic performance, stability, and overall handling.

For example, a narrow hull design with a deep V-shape is ideal for speed, while a wider, flatter hull provides stability for cruising. The choice of materials, such as fiberglass or aluminum, impacts the boat’s weight and durability.

The hull design is a balance between achieving efficient hydrodynamics and providing interior space for accommodations. As a designer, finding this equilibrium is a constant challenge.

3)     Keel & Rudder Design

The keel and rudder are critical components of a sailboat’s underwater structure. The keel provides stability by preventing the boat from tipping over, while the rudder controls its direction. Keel design involves selecting the keel type (fin, bulb, or wing) and optimizing its shape for maximum hydrodynamic efficiency.

Rudder’s design focuses on ensuring precise control and maneuverability. Both components must be carefully integrated into the hull’s design to maintain balance and performance.

Keel and rudder design can be particularly challenging because they influence the boat’s behavior in different ways. A well-designed keel adds stability but also increases draft, limiting where the boat can sail. Rudder design must account for both responsiveness and the risk of stalling at high speeds.

4)     Sail & Rig Design

Sail and rig design play a pivotal role in harnessing wind power. Sail choice, size, and shape are tailored to the boat’s intended use and performance goals. Modern sail materials like carbon fiber offer lightweight and durable options.

The rig design involves selecting the type of mast (single or multiple), rigging configuration, and mast height. These choices influence the sailboat’s stability, maneuverability, and ability to handle varying wind conditions.

Balancing the sails and rig for optimal performance is a meticulous task. The sail plan should be designed to efficiently convert wind energy into forward motion while allowing for easy adjustments to adapt to changing conditions.

5)     Balance

Balancing a sailboat is crucial for its performance and safety. Achieving the right balance involves a delicate interplay between the hull, keel, rudder, and sail plan. Proper balance ensures the boat remains stable and responds predictably to helm inputs, even in changing wind conditions.

Balance is not a static concept but something that evolves as the boat sails in different wind and sea conditions. Designers must anticipate how changes in load, wind angle, and sail trim will affect the boat’s balance.

Achieving balance is both an art and a science, and it often requires iterative adjustments during the design and testing phases to achieve optimal results.

6)     Propulsion

While sailboats primarily rely on wind propulsion, auxiliary propulsion systems like engines are essential for maneuvering in harbors or during calm conditions. Integrating propulsion systems seamlessly into the boat’s design requires careful consideration of engine placement, fuel storage, and exhaust systems.

The choice of propulsion system, whether it’s a traditional diesel engine or a more eco-friendly electric motor, also impacts the boat’s weight distribution and overall performance.

7)     Scantling

Scantling refers to the selection of structural components and their dimensions to ensure the boat’s strength and integrity. It involves determining the appropriate thickness of the hull, deck, and other structural elements to withstand the stresses encountered at sea.

Scantling is a critical aspect of sailboat design, as it directly relates to safety. A well-designed boat must be able to withstand the forces exerted on it by waves, wind, and other environmental factors.

8)     Stability

Stability is a critical safety factor in sailboat design. Both upright hydrostatics and large-angle stability must be carefully assessed and optimized. This involves evaluating the boat’s center of gravity, ballast, and hull shape.

Achieving the right balance between initial stability, which provides comfort to passengers, and ultimate stability, which ensures safety in adverse conditions, is a delicate task. Designers often use stability curves and computer simulations to fine-tune these characteristics.

9)     Layout

The layout of a sailboat’s interior and deck spaces is a blend of functionality and comfort. Designers must consider the ergonomics of living and working aboard the vessel, including cabin layout, galley design, and storage solutions. The deck layout influences crew movements and sail handling.

Layout design also extends to considerations like ventilation, lighting, and noise control. Sailboats are unique in that they must provide both comfortable living spaces and efficient workspaces for handling sails and navigation.

10)  Design Evaluation

The final phase of sailboat design involves rigorous evaluation and testing. Computational fluid dynamics (CFD) simulations, tank testing, and real-world sea trials help validate the design’s performance predictions. Any necessary adjustments are made to fine-tune the vessel’s behavior on the water.

The evaluation phase is where the theoretical aspects of design meet the practical realities of the sea. It’s a crucial step in ensuring that the sailboat not only meets but exceeds its performance and safety expectations.

Conclusion:

In conclusion, sailboat design is a highly technical field that requires a deep understanding of hydrodynamics, engineering principles, and materials science. Naval architects and yacht designers meticulously navigate through the intricacies of hull design, keel and rudder configuration, sail and rig design, balance, propulsion, scantling, stability, layout, and design evaluation to create vessels that excel in both form and function. The harmonious integration of these elements results in sailboats that are not just seaworthy but also a joy to sail, and this process is a testament to the art and science of sailboat design.

Click here to read about “ HARNESSING THE POWER OF ARTIFICIAL INTELLIGENCE IN BOAT DESIGN “

Follow my Linkedin Newsletter here:  “LinkedIn Newsletter”

0 comments Leave a reply

Save my name, email, and website in this browser for the next time I comment.

Recent Posts

• THE CHALLENGES Of SMALL CRAFT DESIGN COMPARED TO LARGER VESSELS
• UNDERSTANDING ROYALTY AGREEMENTS & DESIGN OWNERSHIP IN BOAT DESIGN
• FREQUENTLY ASKED QUESTIONS TO A BOAT DESIGNER: A COMPILATION
• ADVANTAGES OF HDPE COLLAR OVER REGULAR RIB
• HDPE’S EXCLUSIVE FEATURES DISTINCT FROM TRADITIONAL BOAT MATERIALS

Recent Comments

• Casey Lim on HDPE BOAT PLANS
• BRYN BONGBONG on HDPE BOAT PLANS
• Keith on HDPE BOAT PLANS
• Daniel Desauriers on WHY HDPE BOATS?
• November 2023
• October 2023
• February 2023
• January 2023
• September 2022
• January 2021
• ARTIFICIAL INTELLIGENCE
• boatbuilder
• BOAT CONSTRUCTION TECHNIQUES
• BOAT DESIGN COST
• boatdesign process
• CAREER PATHWAYS
• COMMERCIAL BOATS
• conventional boats
• custom boat
• DESIGN ADMINISTRATION
• DESIGN SPIRAL
• EXTREME CONDITIONS
• Freelance advantage
• freelance boat designer
• FRP Boat without Mold
• HDPE Collar
• INDIA'S MARITIME
• INVENTORY MANAGEMENT
• ISO STANDARDS
• Mass Production
• Monhull vs Catamaran
• Naval Architect
• Naval Architecture
• PLANING HULL
• Project Management
• Proven Hull
• PSYCHOLOGY OF BOAT DESIGN
• QUALITY CONTROL
• RECREATIONAL BOATS
• ROYALTY AGREEMENTS
• SANDWICH VS SINGLE SKIN
• SOLOPRENEUR
• YACHT DESIGN COURSE

What Is a Sailboat Keel and How Does it Work?

Keels are an essential part of any boat's design and determine handling properties, durability, and comfort. To understand why they matter, we must understand how they work first.

On this page:

The basics of sailboat keels explained, the importance of sailboat keels, keel design basics, what is a keel.

The keel is a structural member of a boat which runs length-wise across the hull from front to back. It is the lowest part of any hull and the backbone of a ship or boat. Sailboats use deep-running keel designs which extend out of the hull. They can be made from timber, metal, or fiberglass.

What does a keel look like?

Sailboat keels typically look like a long fin, or flat blade, at the bottom of the hull, which runs down for about 1.5 meters. While most modern sailboats use fin keels, the full keel is integrated into the hull, resulting in a more triangular shape that is shallow at the front and deeper at the back.

Since keel designs differ, the exact shape also differs. Here is a clear diagram showing the differences between different sailboat keel designs:

Where is the keel on a boat located?

The keel is located in the center of the bottom of the boat's hull, combining both hull sides. Sailboat keels extend out from the hull downwards. Depending on the exact keel design, the extended part can run from stem to stern, or just narrowly in the center of the boat's hull.

What does a keel do?

Keels help boats maintain course by countering the current and wind. They also stabilize boats by reducing roll and heel angle. Roll is the tendency of boats with round hulls to roll over. Heeling is the tendency of sailboats to heel due to the force of the wind on the sails.

How does a keel work?

Keels provide sideways resistance to reduce slippage. Sailboat keels usually carry iron or lead ballast in their tip to act as a counterweight to the wind's force on the sails, which reduces heeling. The keel's length acts as a lever, increasing the ballast's effectiveness and improving its stabilizing properties.

In other words, the deeper the keel runs and the heavier its ballast is, the more stable the boat will be.

Slippage simply means falling of course due to the current and wind.

The keel ballast lowers the center of gravity of the boat and counteracts the buoyancy of its displacement hull. As the boat tilts, the center of gravity and center of buoyancy move downwards, reducing the heel angle. This is called righting moment . More righting moment results in less heel angle.

Keels also increase the wetted surface of a boat. Wetted surface is simply the amount of surface underwater. The larger the wetted surface, the more resistance there is. Sailboats are among the boat designs with the largest relative wetted surface. A larger wetted surface increases sideways resistance which reduces slippage to leeward, helping to maintain course.

Do all sailboats need a keel?

All sailboats need a keel. Without it, a sailboat would very easily capsize due to a combination of hull design and wind force on the sails. Sailboats have displacement hulls, which tend to roll easily. Wind force is multiplied through the mast, which acts as a lever, and could capsize the boat if it didn't had a keel.

The displacement hull design is also used on canoes, and if you've ever tried to enter one a bit too quickly, you'll know how quickly they roll over.

However, there are sailboats that use a different hull design, which reduces the need for a keel or enables them to use alternative keel designs.

Do all sailboats have a keel?

Nearly all sailboats have some sort of keel. However, not all sailboats have a typical, deep-running fin keel, since not all need one, and in some cases, a shoal draft is desired.

For example, some sailboat designs use leeboards or removable keels, like daggerboards, which enable a boat to enter much more shallow waters.

What is a boat without a keel called?

Boats without a keel are called sailing dinghies. These small boats (under 20 feet) use a flat-bottomed hull design to stabilize instead of a keel. This makes them useful for entering shallow waters and beaching.

Examples of sailboats without a typical keel

• Barges , which use flat-bottomed hulls to reduce heel
• Sailing dinghies , which have a flat-bottomed hull and no keel
• Sunfish and lasers , which often use removable daggerboards

Two examples of sailboats with alternative keels are Dutch barges and Cornish Crabbers. Dutch barges use leeboards , while the Cornish Crabber uses a swing keel , which can be lifted or lowered according to water depth.

Sailing dinghies, sunfish, and lasers typically use no keel or come with daggerboards, which can be removed. They capsize easily and often, which is why you'll see so many toppled sailboats drifting across the lake at sailing camps.

Can you sail without a keel?

You can sail without a keel, however, you could easily capsize and would experience a lot of roll and heel. To prevent capsizing, you would need a different hull design. Historic sailboats without keels use flat-bottomed hulls to prevent excessive roll and capsizing.

The Dutch barge design actually uses a very flat bottom instead of a full round displacement hull, which makes it a bit faster, stiffer, and counters heel just by the hull design alone. But even these sailboats require some sort of stabilization, which is provided in this case by their leeboards.

Can a sailboat rest on its keel?

Most keel constructions can support the weight of the sailboat, but depending on the design, proper precautions need to be taken. Boats resting on a fin keel or full keel will require additional support. The bilge keel (or twin keel) is specifically designed to rest upright in tidal waters.

Fin keel sailboats can sag over their length over time. Other keel designs spread the weight over a larger surface, like the full keel.

The most common sailboat keel types

There are dozens of keel designs and variants out there. The most common ones are the full keel , fin keel , and centerboard . Each of these designs has different properties. Full keels handle better in rough conditions, while fin keels are easier to maneuver in and out of slips.

Discussing them all here would be beyond the scope of this article, but I've described the most common keel types and their properties in my illustrated guide. If you want to learn more about the different designs, I recommend you read that.

How deep is a keel?

On average, keels are between 1 and 2 meters deep , in order to get through the surface drift layer of the water. Some keel designs run less deep, like full keels, which require less depth due to increased weight and wetted surface, or alternative designs like leeboards, which only touch the water's surface.

The water's surface drift layer is the layer of water directly affected by the wind.

How heavy is a sailboat keel?

Most sailboats carry around 35-40% of their total weight in their keel. With an average cruising sailboat weighing 15.000 pounds, the average keel weighs between 5.000-6.000 pounds . However, the total required weight is not just determined by sailboat weight, but also by sail area and the length of the keel.

Deeper keels provide more leverage, reducing weight need. A larger sail area increases weight requirement.

What material are sailboat keels made of?

Sailboat keels are typically made of reinforced fiberglass layers, steel, or wood, depending on the hull material, boat model, and build year. Keel ballast in the tip is usually made of lead, iron, concrete, or even water.

How are keels attached to boats?

Some keels are integral to the hull's structure, like the full keel or modified full keel. Other keels are bolted onto the hull, like the fin keel, wing keel, or bulb keel. With this design, the top of the keel slides into a vertical keel box inside the hull and is bolted in place using keel bolts.

What is a skeg keel?

A skeg keel is a type of rudder design in which the rudder is integrated into the keel design, for example with full keels or modified full keels, therefore providing protection against damage from collisions and waste.

What is the chord of a keel?

A chord is a term used to describe the length of any edge on a keel, whether it's the leading edge, trailing edge, or top edge connecting to the hull. The top edge is referred to as the 'root end', while the length of this edge is called the 'root chord'.

• Source: David Vacant, published on repository TU Delft

The difference between the rudder and the keel

While the keel and rudder design can overlap, the rudder is generally the most aft part, while the keel sits in front of the rudder. The rudder is used to set a course, while the keel's function is to provide directional stability and prevent roll.

The difference between the keel and the hull

While in some keel designs the hull and keel are integrated, like, for example, full and modified full keels, with other designs, the keel is bolted onto the hull, like the case with fin keels. The hull is the bottom of the boat, while the keel is the fin below the bottom of the boat. The hull provides buoyancy, while the keel provides stability.

Keel replacement cost

Leave a comment, you may also like, sailboat keel types: illustrated guide (bilge, fin, full).

The keel type is one of the most important features of your boat. But the different designs can be confusing, so I've set out to create a very clear guide that will …

Yachting Monthly

• Digital edition

How keel type affects performance

• Chris Beeson
• December 2, 2016

James Jermain looks at the main keel types, their typical performance and the pros and cons of each

A fin keel and spade rudder configuration gives high pointing but can be sensitive on the helm Credit: Graham Snook/YM

James Jermain has tested hundreds of yachts in his 30 years as Yachting Monthly’s chief boat tester

The performance and handling of a yacht depends on many things, but perhaps the most important single feature is the shape of the hull and the profile of the keel. Over the years hulls have become shallower and keels narrower, but for many types of sailing this progression is not necessarily progress. Of the various shapes that have evolved, each has its own advantages in different circumstances. Here is a run-down of how they may fit your sort of sailing.

FIN KEEL WITH SPADE RUDDER

A low wetted surface area and aerofoil shape means speed and agility

The most common modern option, usually combined with light but beamy hulls with high freeboard.

GENERAL AND TO WINDWARD

• Low wetted surface and good aerofoil shape means good speed, high pointing and quick tacking
• Light steering
• Best designs can slice through heavy seas in reasonable comfort
• High volume, light-weight designs can be lively and tiring in heavy weather
• Flat sections can cause slamming
• Less steady on the helm, requiring more work and concentration
• Strong tendency to round-up when hard pressed
• Generally require earlier reefing
• Can be unstable when hove to
• Quick to surf and may even plane
• Can broach easily and suddenly
• Can be directionally unstable and hard to control in heavy conditions

UNDER POWER

• Handling is precise and turns tight and quick
• Some handle almost as well astern as ahead
• Limited lateral area so susceptible to beam winds at low speeds
• An unattended helm can slam over suddenly

FIN KEEL WITH SKEG RUDDER

The skeg running aft protects the rudder and improves tracking under sail and power

Similar to above but with some key differences.

• Skeg provides better support for the rudder
• Tracking under sail or power is improved
• There is less chance of damage
• More wetted surface so potentially slower
• Objects can get stuck between rudder and skeg
• Limited balancing can make helm heavier

The mass of a long keel is often more seakindly and will carry way well.

The traditional option, usually found on pre-1970s designs.

• Good tracking
• Slow, soft, comfortable motion
• Drive powerfully through short seas but can be wet
• Carry way through tacks
• Resist rounding-up
• Heave-to well
• High wetted surface area and a poor aerofoil shape, so speed reduced, tacking slow, leeway increased and pointing ability reduced
• Long ends can cause hobby-horsing
• An unbalanced hull or rig can cause heavy helm
• Track well and very resistant to broaching
• Very stable in heavy conditions
• Reluctant to surf (a mixed blessing)
• Carry way well
• Track straight
• Heavy construction can reduce vibration and noise
• Large turning circle ahead
• Unpredictable and hard to control astern

LIFTING OR SWING KEEL

A lifting keel enables beaching, but beware of stones jamming the plate

The ultimate shallow-draught option.

• A fully retracting keel offers shallowest draught
• A well-designed lifting keel can be very efficient and fast
• Grounding on anything other than soft mud or sand can damage an unprotected hull
• Stub keels offer better protection but are less efficient and prevent level drying out, except in soft mud
• Stones and dried mud can jam the lifting plate
• Internal keel boxes reduce accommodation space
• Directional stability is poor
• Early surfing and planing
• Control can easily be lost in strong winds
• Good performance and handling with keel down
• Directional control increasingly poor as the keel is raised

TWIN OR BILGE KEEL

A bilge-keeler will dry out upright on a flat bottom

A popular shoal-draught option in Britain, less so abroad.

• Shallower draught
• Dry out upright on a flat bottom
• Good protection when grounding
• Good designs are better to windward than long keels, almost as good as fins
• Pointing and speed to windward is reduced, considerably so in older designs
• When well heeled, waves can slap under the windward keel
• Can topple over if one keel finds a hole or soft ground

Modified water flow over the wing keel foot can give the motion of a longer, heavier boat

Once popular, now largely replaced with various types of bulb.

• Reduced draught
• Low CoG means good righting moment
• Modified water flow over keel foot means greater efficiency and gives the motion of a longer, heavier boat
• More likely to pick up lobster pots, etc
• Risky drying out
• Weed and barnacle growth under wings difficult to remove

Enjoyed reading this?

A subscription to Yachting Monthly magazine costs around 40% less than the cover price .

Print and digital editions are available through Magazines Direct – where you can also find the latest deals .

YM is packed with information to help you get the most from your time on the water.

• Take your seamanship to the next level with tips, advice and skills from our experts
• Impartial in-depth reviews of the latest yachts and equipment
• Cruising guides to help you reach those dream destinations

Follow us on Facebook , Twitter and Instagram.

All About the Sailboat Rudder

By Matt Claiborne

What Is a Boat Rudder?

The rudder is the underwater part of the boat that helps it turn and change direction. It’s mounted on the rear of the boat.

Rudder vs Keel

A rudder is there to steer direction and a keel provides stability and enable sailing windward.

How Does the Rudder Work?

Originally a steering oar and now a mounted panel, the rudder is an essential underwater control surface on boats that, by deflecting water flow, allows turning the bow by moving the stern.

Learn About Other Boat Parts

Do sailboats come with motors, prow of a boat.

New Rudders

Replacement Sailboat Rudders and Centerboards

Four Types of Rudders On Sailboats

The four rudder types are: full rudder, spade rudder, skeg rudder, and outboard rudder. We will discuss the advantages and disadvantages of each.

Full Rudder

The full or full keel rudder is at the aft end of a full length keel. The keel-rudder runs along the entire length of the bottom of the boat’s hull. This full length rudder is safe and more resistant to damage. The leading edge of the keel protects the rudder from debris. The full rudder is a trademark of offshore cruisers like Cabo Ricos and Wetsails. Damage may be avoided even when grounding. The boat will rest safely on its side until the tide returns and lifts the boat off the shoal.

Spade Rudder

The spade rudder rests below the transom separate from the keel. A spade rudder turns easily because the water rushes both against its fore and aft edges – good when using a tiller. There’s less wet area so the spade rudder is fast. The spade, along with partial spade rudders are becoming popular in many sailboat designs.

Skeg Rudder

Compared to other styles, the skeg rudder is modern in safety and performance and popular on current production boats. The skeg rudder is similar to a spade keel and is fast. The skeg rudder’s fore edge is protected by a “faux keel” that extends from aft of the hull. Hylas yachts are known for their skeg rudders.

Outboard Rudder

Outboard rudders are used on smaller boats. They are attached to the transom of the boat, hanging off the stern. Racing prams employ outboard rudders. They are also easy to jerry rig as emergency rudders. Any long piece of metal and flat piece of wood, as in a cabin door, can work.

Each type of rudder has its advantages and disadvantages. Most importantly, inspect your rudder regularly and carry a spare.

Foss Foam products can create a replacement rudder for your sailboat. Contact us for more information.

The Types of Sailboat Rudders

• Snowboarding
• Scuba Diving & Snorkeling

Full Keel Rudder

On a sailboat , as the rudder is moved to one side by means of the tiller or steering wheel, the force of the water striking one edge of the rudder turns the stern in the other direction to turn the boat. Different types of rudders have different advantages and disadvantages. The type of rudder is often related to the boat’s type of keel.

Rudder on Full-Keel Sailboat

As shown in this photo, the rudder of a full-keel boat is usually hinged to the aft edge of the keel, making a continuous surface. The engine’s propeller is usually positioned in an aperture between the keel and rudder.

Advantages of Full Keel Rudder

The primary benefit of this rudder configuration is the strength and protection provided to the rudder. It is hinged at top and bottom, well distributing the forces on the rudder. Rope (such as lobster pot warps) or debris in the water cannot snag on the rudder.

Disadvantage of Full Keel Rudder

Because the sideways force of the water on the rudder is entirely behind the rudder’s pivoting point at its leading edge, putting all the force on one side of the rudder, it takes more energy to move the rudder. This is one reason why larger boats seldom have tillers—because it can require much force to “push” the rudder out against the water streaming past the keel.

Spade Rudder

Most fin keel boats have a spade rudder, which extends straight down from the aft hull section. The rudder post comes down through the hull into the rudder itself, allowing the entire rudder to rotate to either side, pivoting around the post.

Advantages of Spade Rudder

The spade rudder is self-standing and does not require a full keel or skeg for its mounting. The rudder post inside the rudder can be moved aft from the leading edge (see next page on Balanced Rudder) so that the force of the water is not all on one side when the rudder is turned. This requires less energy to steer than with a keel- or skeg-mounted rudder.

Disadvantage of Spade Rudder

A spade rudder is more vulnerable to debris or objects in the water, which may strike the rudder and exert a force on the rudder post, the only structure supporting the whole rudder. Even the force of water when the boat “falls” off a wave can exert damaging stress on a spade rudder. If the rudder post is bent, the rudder may jam and become useless.

Balanced Spade Rudder

Note the clear air space at the top of the leading edge of this balanced spade rudder. The rudder post is several inches back from the front of the rudder. When the rudder is turned, the leading edge rotates to one side of the boat while the trailing edge rotates to the other side. While the turning action on the boat is the same, the forces on the helm are more nearly balanced, making it very easy to steer.

Skeg-Mounted Rudder

Some fin keel sailboats have a skeg-mounted rudder like the one shown. The skeg offers the same advantages as a keel mounted rudder: the rudder is protected from objects in the water and has more structural strength than a rudder mounted only on the rudder post.

It also has the same disadvantage: because it is not “balanced” as a spade rudder may be, with water forces distributed on both sides, it requires more force to turn the rudder.

Outboard Rudder

An outboard rudder is mounted outside the hull on the boat’s stern, such as shown in this photo, rather than below the hull using a rudder post or hinges to the keel or skeg. Most outboard rudders are turned with a tiller rather than a steering wheel since there is no rudder post to which to gear a wheel.

Advantages of Outboard Rudder

An outboard rudder does not require a hole through the hull for a rudder post and thus is less likely to cause trouble if damaged. The rudder can often be removed or serviced while the boat is still in the water. Hinges at the top and bottom of the rudder section may provide more strength than a single rudder post.

Disadvantages of Outboard Rudder

Like a spade rudder, an outboard rudder is vulnerable to being struck by or caught in objects or rope in the water. Unlike a spade rudder it cannot be balanced in the water flow, so the force of water is always on one side of the pivot point, requiring more energy for turning the rudder.

A rudder is often related to keel shape . 

• Choosing a Centerboard or Fixed Keel Sailboat
• Learn How to Sail a Small Sailboat – 1. The Parts of the Boat
• Control Your Tiller Without a Tiller-Tamer
• 6 Types of Boat Engines
• Choosing an Inboard or Outboard Engine
• How to Tow a Dinghy Behind a Sailboat
• The Sunfish: A Perfect Lake or Urban Sailboat
• Do It Yourself Boat Trailer Tongue Extension
• How to Anchor a Sailboat
• Simple Reefing System for Sailors
• How Brake Calipers Work
• How to Rig a Preventer Line
• The What, Why, and How of Wheel Balancing
• RC Airplane Parts and Controls
• How to Keep an Installer from Damaging Your Wheels
• Interesting Facts About Navy Submarines

• New Sailboats
• Sailboats 21-30ft
• Sailboats 31-35ft
• Sailboats 36-40ft
• Sailboats Over 40ft
• Sailboats Under 21feet
• used_sailboats
• Apps and Computer Programs
• Communications
• Fishfinders
• Handheld Electronics
• Plotters MFDS Rradar
• Wind, Speed & Depth Instruments
• Anchoring Mooring
• Running Rigging
• Sails Canvas
• Standing Rigging
• Diesel Engines
• Off Grid Energy
• Cleaning Waxing
• DIY Projects
• Repair, Tools & Materials
• Spare Parts
• Tools & Gadgets
• Cabin Comfort
• Ventilation
• Footwear Apparel
• Foul Weather Gear
• Mailport & PS Advisor
• Inside Practical Sailor Blog
• Activate My Web Access
• Reset Password
• Customer Service

• Free Newsletter

Maine Cat 41 Used Boat Review

CS 30 Used Boat Review

Hinckley 49 Used Boat Review

Island Packet 31 Used Boat Review

Best Crimpers and Strippers for Fixing Marine Electrical Connectors

Thinking Through a Solar Power Installation

How Does the Gulf Stream Influence our Weather?

Can You Run a Marine Air-Conditioner on Battery Power?

Master the Sailing Basics: Never Stop Learning the Little Things

How to Mount Your Camera on Deck: Record Your Adventures with…

Un-Stepping the Mast for America’s Great Loop

Headsails and Spinnakers: How to Explain Their Functions to a Beginner

Sinking? Check Your Stuffing Box

The Rain Catcher’s Guide

How to Change Your Engine Mounts

Keeping Water Clean and Fresh

Vinyl Boat Lettering DIY Application and Repair

Those Extras you Don’t Need But Love to Have

Three-Model BBQ Test

Alcohol Stoves— Swan Song or Rebirth?

Womens Foul-Weather Gear

Preparing Yourself for Solo Sailing

How to Select Crew for a Passage or Delivery

Preparing A Boat to Sail Solo

Chafe Protection for Dock Lines

Waxing and Polishing Your Boat

Reducing Engine Room Noise

Tricks and Tips to Forming Do-it-yourself Rigging Terminals

Marine Toilet Maintenance Tips

• Sailboat Reviews

A Look at Sailboat Design: Fin Keels vs. Full Keels

Details like keel design count when considering cruising sailboats..

Photos by Ralph Naranjo

When a keel tears away from a sailboats hull, it makes the loss of a rig or rudder seem like a minor inconvenience. History shows that its an uncommon occurrence, but because we now annually hear of such incidents, weve decided to take a closer look at keels and see what keeps the ballast where it belongs.

The International Sailing Federation (ISAF) Offshore Special Regulations devotes pages to helping sailors prevent and respond to a crew overboard incident. There is nothing about how to handle the loss of a keel or ballast bulb. Some might say this is because such occurrences are so infrequent, while others note that, if youre still upright once the ballast breaks off theres not much you can do other than blow the sheets, douse the sails as quickly as possible and attempt to stop any leaks.

When solo sailor Mike Plants Open 60 Coyote lost her lead bulb in 1992, Mike was lost at sea. Other adventure-sailors have survived near instantaneous capsize precipitated by keel loss. In 2003, round-the-world racer Tim Kent and his crew capsized when Everest Horizontal lost its ballast on the way back from Bermuda. US Sailing Safety at Sea Committee Chairman Chuck Hawley was aboard the racing sloop Charlie, on the way back from Hawaii, when a loud groaning sound led to a deep heel as the lead peeled away from the keel bolts and ballast headed straight to the bottom. This encounter at least had a happy ending thanks to the crews quick actions to douse sail. Apparently the keel had been cast with too little antimony (an additive that causes lead to become a harder alloy). The point here is that keeping the keel attached is as important as keeping the crew safely on board. And for the offshore monohull sailor, preventing a keel loss, like preventing crew overboard, requires some informed forethought.

A ballast keel on a sailboat is a classic example of potential energy poised in a balancing act. The buoyancy of the hull itself offsets the effect of thousands of pounds of lead or iron. At rest, gravitys attraction for the dense material strains against the buoyancy of the hull, and the adjacent garboard region is continuously in tension. Few sailors spend much time contemplating how keel bolts corrode and what cycle-loading does to the resin matrix comprising the garboard region just above the ballast. What is apparent, is that the attachment material, whether it be wood, metal or fiber reinforced plastic (FRP), must be able to support a mass of metal weighing as much as a small truck-and do so day in and day out for decades.

Underway, every tack causes the rig and sailplan to try to lever this ballast package free from the hull. And when the helmsman starts daydreaming about lobster for dinner and wanders off course onto a granite ledge Down East, the keel designed to handle sailing loads takes it on the chin. Its easy to see why experienced designers and builders lose sleep over their decisions about keel shape, structure, and what kind of safety factor should be built into the structure.

Its surprising to discover that with better materials and computer-aided design, we still hear about incidents such as the Rambler capsize in the 2011 Fastnet Race (PS, May 2012). Just as significant is a spate of smaller race boat keel-ectomies that have caused ISAF to send out a cautionary note to sailors around the world, and introduce new structural standards for race boats. Keeping the ballast attached to the boat involves an awareness of a chain-like set of failure points. And one of the most difficult decisions each designer must make is how to marry foil efficiency with a structural safety margin that covers the boats intended usage and the unintended use of the keel as a depth sounding device.

For decades, engineers and naval architects have had to contend with some racing sailors Icarus-like quest-a trend that prioritizes shedding weight and making the keel foil a long, thin appendage with a high-aspect ratio. Though not quite a flight toward the sun with wings made of wax and feathers, some race-boat scan’tlings walk a fine line between lightweight and structural failure. The challenge lies in attaching a lead bulb on a high-tensile steel foil to a lightweight, high-modulus, FRP hull. Interconnecting the dense metallic ballast to the lower-density foam/fiberglass hull structure is a true engineering puzzle. Part of the challenge lies in the dissipation of point loads (confined to a relatively small area) and how to handle the resulting stress risers. A stress riser is the point at which theres an abrupt change in a materials flexibility, such as where a stiff, fin keel meets the more elastic hull bottom. In FRP composites like those found in a balsa-cored hull, stress risers are a likely place for delamination to occur. Over time, these can result in the failure of the FRP composite.

The see-saw effect of the keel counteracting a vessels righting moment is a mathematically predictable energy transfer. Even the effect of groundings such as those that turn hull speed into a dead stop can be quantified. But its the cumulative effect of fatigue (localized structural damage caused by cyclical loading) and corrosion that are harder to pin down.

The term allision refers to hitting a fixed object such as a granite ledge or coral reef. Naval architects analyze the energy transfer and evaluate the stress and strain characteristics that occur. The recognition that the keel-to-hull connection must endure even more punishment than is doled out in heavy-weather sailing episodes is at the heart of how structural specs are devised.

Designers also must consider the jack-hammer-like pounding of a keel on a reef in surf, and realize that there are limits to the abuse a keel and hull can endure. With this in mind, its reasonable to assume that sailboat keels should be built to handle sailing induced loads for decades. It is the extra safety factor built into the boat that defines what happens when the sandbar is a rock pile.

What is harder to anticipate are the unusual encounters that can inflict serious damage to the keel connection. Take, for example, what happens when a sailboats deep fin keel is wedged in a rocky cleft and a good Samaritan with a big powerboat attempts to pivot the sailboat using a line attached to the bow. The distance from the keels vertical centerline to the stem may be 20 feet or more, and with a couple of thousand pounds of bollard pull, the 20-foot lever arm creates a rotary force that can spike to 40,000 foot-pounds or more. This level of torque goes well beyond what most designers and builders model as sailing loads, and its likely to seriously damage the boat.

In plain low-tech talk, extreme fin keels provide a valuable performance edge, but they come with their own set of downsides that every owner needs to be aware of. In essence, the more radical the keel shape, the better the crew must navigate.

A couple of decades ago, PS Technical Editor Ralph Naranjo ran a boatyard and had a client who liked to cut the corners during Block Island Race Week. His first spinnaker reach into a granite boulder stopped the boat and shoved the companionway ladder upward six inches. This underscored how an allision that causes the keel to stop abruptly transfers a shock wave through the entire hull. The resulting compression cracked several transverse members in the New York 40 and damaged the core in the canoe body near the garboard.

The FRP repairs had to be tapered and all delamination problems resolved. The moderate-aspect-ratio lead fin keel absorbed a good deal of the blunt trauma. Judging from the cannonball-size dent on the leading edge of the lead keel, it was clear that the impact was significant. The dent offered grim proof of the advantage of having soft lead instead of steel as keel ballast. New floor frames were added, the broken transverse members were replaced, and the boat was off and sailing.

The next season, the boat had another Block Island encounter, and only because the Petersen-designed New York 40 was a pretty ruggedly built boat was a second repair even considered. This time, an equally violent keel-to-hull trauma came from an on-the-wind encounter with a different rock. The extent of the delamination was greater than it had been in the first go round, and more extensive core removal and repair was required. The keel was dropped in order to check the bolts and the garboard. With the bilge fully opened for the FRP repair work, the repair crew made a pattern of the canoe body dead rise and fore and aft contour. As the glass work was being completed, they fabricated a stainless-steel grid that would spread keel loads fore and aft as well as athwartship. The new grid reinforced the keel attachment and returned the sloop to the race course.

Afterward, Naranjo and the owner discussed the details of the repair, including the possibility of hidden, widespread damage from the two groundings. These included the dynamic loads imposed upon the chainplates and rigging, the likelihood of hidden resin-cracking, and potential for more delamination and core shear linked to the torque induced by the accident. In short, any serious allision causes overt and hard-to-detect damage far from the actual impact zone, and these can lead to more problems down the road. When buying a used boat, look for a good pedigree, but also look for signs of previous blunt-force trauma. A good surveyor will be skilled in such structural forensics, and he or she will do more than comment on the gelcoat shine.

In the early days of wooden ships and iron men, a lack of dense metal ballast put less point-loading in the garboard region of the hull. Bilges free of cargo were filled with rocks or tighter-fitting granite blocks cut for more compact stacking. The principal of ballasting a vessel was to lower her center of gravity (CG) and create both an increase in the righting arm and a greater righting moment to offset the heeling moment created by the rig and sail plan. The keel also helped lessen leeway and would evolve into an appendage that added lift.

Movable ballast had a few downsides, not the least of which was its propensity to move in the wrong direction at the very worst moment. Even small boat sailors have found out what can happen to unsecured pigs of lead ballast when the boat heels far enough over for gravity to overcome friction. Whether stones, lead, movable water ballast, or a can’ting keel are used to augment the boats righting moment, a sailor must anticipate the worst-case scenario. This is when the weight ends up on the leeward side of the boat and a bad situation can turn into a real catastrophe. Fixing or locking ballast in place, controlling the volume of water put in ballast tanks, and limiting the can’ting keels range are sensible compromises.

Internal ballast, the ballast inside a keel envelope thats contiguous with the hull, is still seen in many new boats. Island Packet is an example of a builder has stuck with this traditional approach of securing ballast without using keel bolts. Its a sensible design for shoal-draft cruisers, and the upsides are numerous. These high-volume, long-range cruisers arent encumbered by the demands prioritized by light displacement, performance-oriented sailors. Instead, Island Packets combine a rugged laminate and a long-footed, shallow-draft keel. This may not place the lead or iron ballast as deep as the tip of a fin keel, but it does keep the all-important CG low enough to deliver a powerful righting moment along with shoal draft.

In order to deliver the high angle of vanishing stability (AVS) also known as limit of positive stability (LPS), designer Bob Johnson puts what amounts to an internal bulb in the very lowest point in the boat. This long slug of iron or lead (depending on the model) is then covered by Portland cement, locking it in the Island Packets monocoque structure. The result is a contiguous FRP structure spreading keel loads efficiently over a considerable amount of hull skin. Keel bolts and the infamous garboard seam are completely eliminated. This approach to sailboat keel design dates back to the Rhodes Bounty II and other prototypes in the production world of sailboats. Now over 50 years old, many of these boats continue to have a tenacious grasp on the lead or iron that they hold.

Encapsulated iron ballast is much less desirable than encapsulated lead, and its sad to see builders skimp on this. Iron, or even worse steel, has been used in many Far Eastern encapsulated keels. It works as long as water and the resulting oxidation havent caused expansion and cracking of the seal. Lead is also denser than ferrous metal, and therefore, the same amount of ballast will have a smaller volume and create less drag.

Encapsulated ballast starts to be less appealing as keels become more fin-like and high-aspect ratio. The reason for this is that the geometry of the support changes, focusing more load on less area of the hull. As hull shapes evolved into canoe underbodies with hard turns in the bilge, and fin-like keels became thinner, deeper, and with shorter chord measurements (thickness), the concept of encapsulated keel became impractical. The Cal 40, Ericson 39, Pearson 365, and a long list of similar genre boats signified the end of an era when performance racer/cruisers would be built with encapsulated ballast.

External Ballast

Performance-oriented sailors and race-boat designers quickly latched on to hull shapes marked by deep-draft, foil-shaped, high-aspect ratio fin keels. From the late 60s to whats currently glowing on CAD screens in designer offices around the world, keels have grown deeper and shorter in chord length, and bulb or anvil-like tips have grown more and more common.

The design development was sound, lift was enhanced, and deeper-not longer-became the answer to getting to windward faster. The challenge was not only in designing an efficient shape, it lay in creating an attachment means that minimized foil flex and twist, retained the low drag coefficient, and still had the ability to withstand an occasional, albeit modest, grounding.

During this same period, marine surveyors and boatyard techs began to see moderate groundings result in major structural problems. The classic example was the allision that produced a moderate dent in the lead at the leading edge of the keel tip. In many cases, further inspection revealed cracks radiating outward from a knot meter or depth sounder mistakenly placed just ahead of the keel. An even closer look often revealed grid damage or a cracked bulkhead just aft of the last keel bolt. Like the New York 40 mentioned earlier, this was a result of a shock wave radiating through the hull structure. As we learned in Mrs. McCrearys science class, Bodies in motion tend to stay in motion, unless acted on by an equal and opposite force. Fin keel sailboats encountering abrupt energy transfers,tend to endure more damage than their long-keel counterparts.

A forensic look at the Achilles heel of external ballast highlights a few pitfalls. First the good news: Lead absorbs impact well, consuming much of the imparted energy through deformation. However, the translation of the remaining energy from the metal keel foil and keelbolts into an FRP hull is where we often find stress risers, and point loading linked to material and hull shape changes. The near right-angle interface between a modern sailboats canoe body and its deep fin keel is a classic load-path hotspot. In the old days, fiberglass techs spoke of oil-canning or the dimpling of a large section of the garboard as tacks were swapped.

Today Naval Architects use Finite Element Analysis (FEA) to better engineer hull structure. Colorized graphics pinpoint load concentration, glowing bright red in the region where the keel joins the hull, the epicenter of the oil-canning. A common solution to coping with this high-load focal point, is to eliminate core in the region and to gradually increase the unit schedule (layers of FRP), or to add an internal FRP grid. Maximum thickness of a keel stub is located where the keelbolts penetrate the stub. In this region, the solid glass thickness is often equal to the dimension of the keel bolt diameter or even greater.

Laminate thickness at the keel bolts is only part of the equation. Just as important is how the transition to the general hull laminate transpires. A bullet-proof keel stub that immediately transitions into a core hull comprising two units of laminate on each side of the panel creates whats equivalent to a tear-on-the-dotted-line weakness. Transitions that involve sharp angles and marked differences in panel strength require a well-reinforced taper that spreads loads gradually rather than abruptly.

Occasionally, we see massive metal frameworks used in the bilge as support for keel bolts; these structures need to be carefully engineered to not create the same hard spot fracture points. When carefully tapered in order to gradually introduce more flex, the problem is abated, as it was in the repair of the New York 40 mentioned earlier. The stainless-steel grid built to support the keel loads incorporated a gradual decrease in stiffness to the framework. The keel was carefully mated to the underside of this grid to ensure full contact (See Keel Bolt Repair Options, online). As a result, the crew relieved the hard spots at the end points and made the transition to the more flexible FRP hull less dramatic.

For cruisers, the take-away lesson is that extra reinforcement, a long garboard keel-to-hull interface, and internal transverse and longitudinal reinforcement really do pay off. Keep in mind that the extra weight this entails is all below the center of gravity and contributes to the secondary righting moment as well as keeping the water out.

This is a big departure from the way many modern production boats are built. They carry a skimpy ballast ratio of 30 percent or less, have less structure to support the keel and are not designed to handle unintended cruising consequences. There are exceptions, and its worth looking at the keel design and structure of the Navy 44 Mark II and the USCG Leadership 44 (see PS, August 2012). These boats utilize external ballast and are examples of rugged keel attachment. They have a relatively long keel-to-stub garboard junction, the laminate scan’tling meets American Bureau of Shipping recommendations, and both utilize an overabundance of 316 stainless-steel keel bolts and an FRP grid to keep the keel where it belongs.

There are many reasons why were seeing more keel problems today. On one hand, light, fast, race-boat design pushes the envelope, and thats probably OK. But when mainstream racer/cruisers start to suffer from lead loss, too much of one good thing (high-aspect ratio) and too little of another good thing (reinforcement) can begin creeping into design and construction.

RELATED ARTICLES MORE FROM AUTHOR

Leave a reply cancel reply.

Log in to leave a comment

Latest Videos

How To Test a Boat Engine

Hunter Legend 35.5 – Behind the Curtain

Whipping Line On Your Sailboat

Hallberg Rassy 42 – Behind the Curtain

• Privacy Policy
• Do Not Sell My Personal Information
• Online Account Activation
• Privacy Manager

Practical Boat Owner

• Digital edition

Keel types and how they affect performance

• Peter Poland
• June 19, 2023

Peter Poland looks at the history of keel design and how the different types affect performance

The Twister is a well-proven example of a generation of production yachts with ‘cutaway’ full keels and keel-hung rudders. Credit: Graham Snook/Yachting Monthly

Having been a boatbuilder for around 30 years until the very early ‘noughties’, I’ve already witnessed – and even taken part in – a lot of changes in the world of yacht design and building.

Yacht design originally evolved as traditional workboats developed into leisure craft.

In his History of Yachting , Douglas Phillips-Birt writes that the Dutch, who gave the name ‘yacht’ to the world, were probably the first to use commercial craft for pleasure in the 16th century.

They created the first yacht harbour in Amsterdam in the 17th century.

When the schooner America visited the UK in 1851 and raced around the Isle of Wight, this led to the America’s Cup and the resulting merry-go-round of race-yacht design that continues to this day.

The Jeanneau Sun Odyssey 35 offers three different fin keel configurations with different draughts plus a lifting keel version with a centreplate housed in a shallow winged keel stub. Credit: David Harding

The creation of what is now the Royal Yachting Association ( RYA ) in 1875 led to the introduction of handicap rules, establishing the sport in Britain.

These rating rules – and their numerous successors down the ages – have helped determine the evolution of yacht design and keel shapes.

Many early yachts were closely based on workboats, commercial cargo carriers or even privateers and naval vessels.

Initially, the ballast was carried in a long keel and the bilges .

New racing rules of the day taught designers to seek and tweak performance-enhancing features.

Maybe racing did not always improve the breed, but it certainly kept it moving ahead.

Artwork inspired by Ted Brewer’s illustration of keel types (excluding centreplate or lifting keels)

The late, great designer David Thomas believed that fishing boats, pilot cutters and oyster smacks had a large influence on the sport of sailing.

Each type of workboat was built to fulfil a specific purpose. And many had to be sailed short-handed while carrying heavy cargoes.

So they needed to combine form and function, sail well and be able to cope with heavy weather.

Proof of the versatility of working boat designs was provided by Peter Pye and his wife, Anne.

They bought a 30ft Polperro gaff-rigged fishing boat (built by Ferris of Looe in 1896) for £25 in the 1930s.

Having converted her to a sea-going cutter, and renamed her Moonraker of Fowey , they sailed the world for 20 years.

It proves how the simplest working boat design can cross oceans and fulfil dreams.

Racing influence on keel types and design

Most early yacht designs were schooners, but during the latter half of the 19th century the gaff cutter rig started to dominate the scene.

Many notable yachts were built at that time and the most important racing design was probably the yawl Jullanar (1875).

Designed and built by the agricultural engineer EH Bentall, she had, in his own words, “the longest waterline, the smallest frictional surface, and the shortest keel”.

She proved to be extremely fast and in her first season won every race she entered. Jullanar became the forerunner of such famous designs as GL Watson’s Thistle (1887), Britannia (1893), and Valkyrie II and Valkyrie III , both of which challenged for the America’s Cup during the 1890s.

Compare the She 36’s graceful overhangs with the vertical stems and sterns of most modern cruiser/racers

In the USA, Nat Herreshoff experimented with hull forms for racing yachts and produced the ground-breaking Gloriana in 1890.

She was a small boat for the times, with a waterline length of 46ft. Her hull form was very different to anything yet seen in the USA.

With long overhangs at bow and stern, her forefoot was so cut away that the entry at the bow produced a near-straight line from the stem to the keel.

It was a revolutionary design, and nothing at the time could touch her on the racecourse.

Many French models, such as this Beneteau, have opted for substantial pivoting keels. Credit: Peter Poland

Herreshoff wrote: “Above the waterline everything on Gloriana was pared down in size and weight… and every ounce of this saving in weight was put into the outside lead.”

Early English rating rules produced the ‘plank-on-edge’ yacht, where the beam became narrower and the draught got deeper.

New rating rules were then adopted to discourage this extreme type and eventually the Universal Rule was introduced in the USA and the International Rule – which produced the International Metre Classes – took over in Europe.

Yet again, racing rules proved to be a major influence on design development.

By the start of the 20th century the big, long-keeled racing yachts like the J Class attracted a lot of public attention, but after World War II everything changed. Yachts built to the Universal Rule fell from favour.

The age of the racing dinghy arrived and the ocean racer became the performance yacht of the future.

To new extremes

A 300-mile race from New York to Marblehead saw the start of offshore racing and the first Bermuda race was run in 1906.

The British were slower to compete offshore, but in 1925 seven yachts took up the challenge to race round the Fastnet Rock, starting from the Isle of Wight and finishing at Plymouth.

EG Martin’s French gaff-rigged pilot cutter Jolie Brise won the race and the Ocean Racing Club was formed.

In 1931 this became the Royal Ocean Racing Club (RORC), which remains the governing body of offshore racing in Britain.

The ‘cutaway’ modified full keel was famously used by Olin Stevens on his mighty Dorade. Credit: Christopher Ison/Alamy

The early competitors in RORC races were long-keeled cruising boats, many of them gaff rigged and designed for comfort and speed.

But everything changed in 1931 when the young American Olin Stephens designed and then sailed his family’s 52ft yawl Dorade across the Atlantic to compete in that year’s Fastnet race.

She won with ease. Then she did it again in 1933, having first won the Transatlantic ‘feeder’ race.

At 52ft LOA, with sharp ends and 10ft 3in beam, some said Dorade looked like an overgrown yawl rigged 6-metre. But her triple-spreader main mast was revolutionary. As were her cutaway forefoot, lightweight construction, deep ballast and 7ft 7in draught.

Dorade took the long keel format to new extremes.

In the USA, the Cruising Club of America (CCA), founded in 1922, played much the same role as the RORC did in Britain.

It introduced its own rating rule which influenced the evolution of yacht design in the USA.

The Elan 333. Both the deep (1.9m) and shallow (1.5m) draught models feature an elegantly faired bulb keel and spade rudder. Credit: Peter Poland

Beam was treated more leniently under the CCA rule, so wider American designs later offered more space for accommodation and a bit more inherent form stability than RORC-rule inspired yachts.

Many famous designers of long-keel racing yachts at this time developed their skills at the yachtbuilding firms they ran, such as William Fife II (1821–1902), his son William III (1857–1944), Charles E Nicholson (1868–1954) of Camper & Nicholsons and Nat Herreshoff of Bristol, Rhode Island.

Around the same time several British yacht designers made their names, including George L Watson (1851–1904) who set up one of the earliest Design Offices and Alfred Mylne (1872–1951), who designed several successful International Metre Class yachts.

Norwegian designers Colin Archer (1832–1921) and Johan Anker (1871–1940) also joined the party.

Continues below…

Boat hull design: how it impacts performance

Peter Poland explains how boat hull design has evolved over the years and how it affects boat handling and accommodation

Sail boat rigs: the pros and cons of each popular design

Peter Poland looks at the history of popular rig designs and how the different types affect boat performance

Improve performance by understanding boat design

Øyvind Bordal explains how form stability, LOA, LWL, speed tables and polar diagrams can help you choose the right boat…

Coming of age: the 1970s yacht designs that have stood the test of time

Sailing in the 1970s was characterised by innovation, enthusiasm, mass participation and home boatbuilding. Rupert Holmes reports

In 1873 Archer designed the first long keel Norwegian yacht, but his real interest was work boats – pilot boats, fishing craft, and sailing lifeboats – some of which were later converted into cruising yachts.

Erling Tambs’s Teddy was a classic Colin Archer long keel canoe-stern design in which he wandered the globe with his young wife and family.

He proved the seaworthiness of Archer’s yachts, as well as their speed, by winning the 1932 Trans-Tasman yacht race.

Fellow Norwegian Johan Anker – a one-time pupil of Nat Herreshoff – became equally famous, thanks to his Dragon-class design that still races today.

As a new generation of designers arrived on the scene in the 1930s, hull tank testing became more sophisticated.

Long keel designs became as much a science as an art.

The leader of this new wave of designers, Olin J Stephens, had been a junior assistant to Starling Burgess who designed race-winning J Class yachts, including the iconic Ranger .

Tank testing was then in its infancy but the USA was ahead of the game and Stephens stored away everything that he learned. He enjoyed a head start over his contemporaries.

Keel types: Fin keels

Between the 1930s and the 1980s more fin keel designs began to arrive on the scene and his firm Sparkman & Stephens produced many of the world’s top ocean racers.

He also designed America’s Cup 12-Metres that defended the cup up to 1983 until Ben Lexcen’s winged keel shook the sailing world.

Many S&S fin keel and skeg production boats – such as the Swan 36 (1967), 37, 40, 43, 48, 53 and 65, She 31 (1969) and 36 and S&S 34 (1968) – still win yacht races and are much sought after as classics.

The S&S 34 has several circumnavigations to its name. Stephens, of course, had his rivals.

Among these was the Englishman Jack Laurent Giles, whose light displacement race-winner Myth of Malham had one of the shortest ‘long keels’ of all time.

(L-R) A Sigma 38 designed by David Thomas and Gulvain (1949) by Jack Giles as a development of his Fastnet-winning Myth of Malham have very different keel types. Credit: Peter Poland

The Dutchman EG Van de Stadt designed the Pioneer 9 (1959) which was one of the first GRP fin keel and spade rudder racers.

Towards the end of his career, Olin Stephens also came up against Dick Carter, Doug Peterson, German Frers and the Kiwis Ron Holland and Bruce Farr.

The development of new shaped keels went hand in hand with this rapid evolution in yacht design.

The full keel, as still found on motor-sailers such as the Fisher range, gave way to the ‘cutaway’ modified full keel as famously used by Olin Stephens on his mighty Dorade , designed back in the late 1920s.

She still wins ‘classic’ yacht races in the USA. American designer Ted Brewer wrote in ‘ GoodOldBoat ’ that Dorade’s offshore racing successes proved that the full keel is not essential for seaworthiness.

The Nicholson 32’s modified ‘cutaway’ long keel results in excellent performance and handling. Credit: Genevieve Leaper

As a result of its improved performance and handling, the modified ‘cutaway’ long keel caught on quickly and became the standard for around 35 years.

This keel type is found on numerous popular designs such as the Nicholson 32 , 26 and 36, Twister 28 and many Nordic Folkboat derivations.

The modified full keel format had a cutaway profile, giving good handling and directional stability while having less wetted surface than the full keel designs.

These yachts can perform well in all conditions and have a comfortable motion.

Even though they are generally of heavier displacement than fin keelers, they are not much slower in light airs , despite their added wetted surface area.

Their main drawback is a wide turning circle ahead and reluctance to steer astern when under motor.

Keel types: Increased stability

The modified full keel was subsequently cut away more and more for bluewater and inshore racers in an attempt to reduce wetted area until, finally, some designers took it to extremes.

As a result, much-reduced directional stability produced craft that were difficult to steer in breezy conditions, broaching regularly.

Whereupon the fin keel and skeg-hung rudder took over, reinstating increased directional stability, improving windward ability, reducing drag and restoring – when under power – control astern and on slow turns.

This fin and skeg format was later followed by the NACA sectioned fin keel with a separate spade rudder .

Soon, many performance cruisers followed this race-boat trend.

The Hanse 430 has a spade rudder and bulbed keel (draught 2.16m or 1.79m shoal draught. Credit: Peter Poland

Many builders now also offer shoal draught fin keel options and shallower twin rudders.

Some, such as Hanse, incorporate L- or even T-shaped bulbs on some Hanses and Dehlers at the base of finely shaped cast iron fins.

A new international competition had encouraged the initial development of modern fin keel yacht designs.

The revamped One Ton Cup was launched in 1965 for yachts on fixed handicap ratings (typically around 37ft long).

This spawned later fixed-rating championships for Quarter Tonners (around 24ft), Half Tonners (around 30 ft), Three-Quarter Tonners (around 33ft), and finally Mini-Tonners (around 21ft).

All these yachts were eventually handicapped under the International Offshore Rule (IOR) that replaced the old RORC and CCA rules.

The revamped One Ton Cup helped encourage the developed of modern fin keel designs. Credit: Getty

Countless production fin keel cruisers designed and built in the 1970’s to 1990’s boom years were loosely based on successful IOR racers that shone in the ‘Ton Cup’ classes.

The IOR handicap system’s major drawback was its Centre of Gravity Factor (CGF) that discouraged stiff yachts.

Once the international IRC rule replaced the IOR, more thought was given to increasing stability by putting extra weight in a bulb at the base of the keel.

GRP production boats followed suit. The keel foil’s chord needed to be wide enough to give good lateral resistance (to stop leeway), yet not be so wide as to add unnecessary drag.

Exaggeratedly thin foils are not suited to cruising yachts because they can be tricky upwind.

Tracking is not their forte and they can stall out. A bonus was an easier ride downwind thanks to wider sterns.

Keel Types: Lead or iron?

And then there is lead. Almost every production cruiser has a cast iron keel for one simple reason; it is much cheaper than lead. But it’s not as good.

Not only does it rust; it is ‘bigger’ for the same given weight. A cubic metre of iron weighs around 7,000kg, while the same cubic metre of lead weighs around 11,300kg.

An iron keel displaces far more water (so has more drag) than the same lead weight. We had always put iron keels under our Hunters – as did our competitors.

But when we came to build the Van de Stadt HB31 cruiser-racer, designer Cees van Tongeren said “No. We use lead.” “Why?” I asked. Cees replied: “If we use iron, the keel displaces more, so the boat sails worse.”

Rustler 36 long keel’s cutaway forefoot delivers responsiveness and manoeuvrability – a reason the design is so popular in the Golden Globe Race. Credit: Beniot Stichelbaut/GGR/PPL

Which explains why top-flight race boats have lead keels – or at the very least composite keels with a lead bulb or base bolted to an iron upper foil, thus lowering the centre of gravity (CG).

Some modern production cruiser-racers offer high-performance lead or lead/iron composite keels – but at a price.

Many Danish X-Yacht and Elan race-boat models, for example, have a lead bulb on the base of an iron NACA section fin.

Rob Humphreys, current designer of the popular Elan and Oyster ranges, said: “The T-keel is good if you have sufficient draught available. If not, the fin element has too short a span to do its job. This is because the T-bulb doesn’t contribute as usefully to side force as a ‘filleted L-bulb.’

“I developed and tested this shape (a blended-in projection off the back of the main fin) for the maxi race boat Rothmans in 1988/9, and have since used it on the Oysters and Elan Impressions. The ‘filleted’ keel we tested for Rothmans had slightly more drag dead downwind (more wetted area) but was significantly better when any side-force occurred; and side-force goes hand-in-hand with heel angle – which is most of the time! When the model spec allows for reasonable draught, the keel option with the lowest centre of gravity will invariably be a T-keel, with a longer bulb giving the greatest scope for a slender ballast package. An L-keel is a compromise and doesn’t suffer from the risk of snagging lines, mooring warps, and nets. [many modern production cruisers have 100% cast iron L- or T-shaped keels]. A lead bulb is preferable to a cast iron keel in terms of volume and density, but it costs more. However, a lead T-keel in a production environment will almost certainly use a cast iron or SG Iron fin, which may rust.”

The Mystery 35, designed by Stephen Jones and built by Cornish Crabbers, has a lead fin keel. Photo: Michael Austen/Alamy

Rustler Yachts also uses lead instead of iron for their keels.

The Rustler 36 long keel (designed by Holman and Pye and winner of the 2018 Golden Globe Race) has a cutaway forefoot to improve responsiveness and manoeuvrability.

The long keel creates more drag but, as with the Rustler 24, the cutaway forefoot makes the 36 more nimble than a full long keel boat, which are more difficult to manoeuvre in reverse under power.

The rest of Rustler’s offshore range – the Rustler 37, 42, 44 and 57 – designed by Stephen Jones – have lead fin keels.

As does his Mystery 35 built by Cornish Crabbers.

These offer an excellent combination of directional stability, performance and lateral stability. The yachts track well, are comfortable in choppy seas, and have good manoeuvrability, all without the flightiness of shorter chord fin keels found on many production family cruisers.

A digital future

Influential designer David Thomas said: “When I started designing, I integrated sharp leading edges to the keel; until someone told me a radius was better. Then we were all taught that an elliptical shape was better still. With the advent of computers, designers could better visualise the end-product; and clever ‘faring programs’ speeded this up.”

So where next? A combination of lighter and stronger materials, rapidly developing computer programs, a desire for maximum interior volume and low costs has led us to today’s production yacht.

Twin rudders improve the handling of broad-sterned yachts when heeled.

The IRC rating rule permits low CG keels, wider beam and near-vertical bows and sterns.

And designers now have an array of new computer tools at their disposal. But maybe there’s still that element of black magic?

As David Thomas so succinctly said: “You can design a yacht 95% right, but the last 5% can be down to luck.”

Keel types : the pros and cons

Full length keel

The Fisher 31 and many motor-sailers have long keels. Credit: Peter Poland

Pros: Directional stability. Heavy displacement leading to comfort at sea.

Cons: Poor windward performance. Large wetted surface leads to drag. When under power at low speeds, the turning circle is wide unless fitted with thrusters. The same applies to manoeuvring astern.

Cutaway modified long keel form with keel-hung rudder

Pros: Reduced wetted surface area leading to increased boat speed. Better windward performance and handling than full length keel. Rudder on the aft end of the keel improves self-steering ability on some designs.

Cons: Under engine, this keel form has a large turning circle ahead and poor control astern. Since the rudder is not ‘balanced’, the helm on some designs can feel quite heavy.

Fin keel with skeg-hung rudder

The skeg gives protection to the rudder. Credit: Graham Snook/Yachting Monthly

Pros: The further reduction in wetted surface area leads to more boat speed. Directional stability and close-windedness are also improved. If full depth, the skeg can protect the rudder against collision damage.

Cons: When combined with a narrow stern, this keel format can induce rolling when sailing dead downwind in heavy winds.

Fin keel with separate spade rudder

Fin keel with spade: Low wetted surface and aerofoil shapes enhance performance. Credit: Graham Snook/Yachting Monthly

Pros: The fin and spade rudder mix reduces wetted surface and gives a more sensitive helm – especially if the blade has ‘balance’ incorporated in its leading edge. Handling under power in astern is precise and the turning circle is small.

Cons: The rudder is fully exposed to collisions. There are no fittings connecting the rudder to a keel or skeg, so the rudder stock and bearings need to be very robust.

Shallow stub keel with internal centreplate.

Pros: When lowered, the plate gives good windward performance. The plate can act as an echo sounder in protected shallow water. There is normally no internal centreplate box to disrupt accommodation. With the plate raised, off-wind performance is good.

Cons: The plate lifting wire needs regular inspection and occasional replacement. Windward performance with the plate raised is poor.

Lifting or swing keel

Boats with lifting keels tend to surf earlier downwind. Credit: Graham Snook/Yachting Monthly

Pros: Shallowest draught so more cruising options; can also be moored on cheaper moorings. Surfs early downwind. Small wetted surface so can be fast.

Cons: Reduced living space due to internal keel box. With a raised keel, poor directional control. Susceptible to hull damage if grounding on hard material.

Twin or bilge keel

Bilge- or twin-keelers can take the ground on the level. Credit: Graham Snook/Yachting Monthly

Pros: Can take the ground in a level position. Modern twin-keel designs with around 15º splay, around 2º toe-in and bulbed bases perform well upwind. Good directional stability due to the fins. Modern twin keels with bulbed bases lower the centre of gravity.

Cons: Older designs do not point upwind well. Slapping sound under windward keel when at a steep angle of heel on older designs. Antifouling between the keels can be tricky. Can be more expensive than fin keels.

Wing keel: A low centre of gravity gives a good righting moment. Credit: Graham Snook/Yachting Monthly

Pros: Low centre of gravity means good righting moment. Shallow draught. Sharper windward performance.

Cons: Larger surface area means it is more likely to pick up fishing gear, like lobster pots. Difficult to move once it is grounded. And difficult to scrub keel base when dried out alongside a wall.

Enjoyed reading Keel types and how they affect performance?

A subscription to Practical Boat Owner magazine costs around 40% less than the cover price .

Print and digital editions are available through Magazines Direct – where you can also find the latest deals .

PBO is packed with information to help you get the most from boat ownership – whether sail or power.

• Take your DIY skills to the next level with trusted advice on boat maintenance and repairs
• Impartial in-depth gear reviews
• Practical cruising tips for making the most of your time afloat

Follow us on Facebook , Instagram and Twitter

• Types of Sailboats
• Parts of a Sailboat
• Cruising Boats
• Small Sailboats
• Design Basics
• Sailboats under 30'
• Sailboats 30'-35
• Sailboats 35'-40'
• Sailboats 40'-45'
• Sailboats 45'-50'
• Sailboats 50'-55'
• Sailboats over 55'
• Masts & Spars
• Knots, Bends & Hitches
• The 12v Energy Equation
• Electronics & Instrumentation
• Build Your Own Boat
• Buying a Used Boat
• Choosing Accessories
• Living on a Boat
• Cruising Offshore
• Sailing in the Caribbean
• Anchoring Skills
• Sailing Authors & Their Writings
• Mary's Journal
• Nautical Terms
• Cruising Sailboats for Sale
• List your Boat for Sale Here!
• Used Sailing Equipment for Sale
• Sell Your Unwanted Gear
• Sailing eBooks: Download them here!
• Your Sailboats
• Your Sailing Stories
• Your Fishing Stories
• Advertising
• What's New?
• Chartering a Sailboat
• Sailboat Rudder

Making a Sailboat Rudder for s/y Alacazam

It's not enough just for a sailboat rudder to steer the boat effectively, it should also contribute to the keel's job of providing lift to windward, and for it to do this it must be designed as a hydrodynamic foil.

Of course a rudder doesn't have to provide lift, but it's a wasted opportunity if it doesn't.

As with an aircraft's wing, to develop lift the sailboat rudder must have water flowing over its leading edge at an angle of attack.

Fortunately for us sailors, the pressure of air on the windward side of the sails, pushes the boat bodily off course slightly and it's this leeway that provide the angle of attack - or angle of incidence- that enables our keels and rudders to provide lift.

But What Type of Sailboat Rudder would be Best for Alacazam ?

First, we considered twin transom-mounted rudders. The usual argument for twin rudders is:

• as the boat heels, the leeward rudder is more deeply immersed and provides better control, and
• the boat, resting on the keel and two rudders can dry-out upright.

But in the end we decided against the twin rudder arrangement because:~

• with Alacazam's deep draught (7 feet, or 2.2m) the twin rudders wouldn't be deep enough to achieve the drying-out upright benefit, and
• the mechanical complexity of tiller steered twin rudder system went against one of our key design principles - keep it simple, and
• with no propwash flowing over the rudders, manoeuvring under power in tight situations would be a little too interesting for my tastes.

So the conventional single rudder approach it was to be. But what type of sailboat rudder?

A Transom-Hung Rudder

We liked the simplicity of this arrangement, but it didn't suit Alacazam's hull design at the stern. We wanted a sugar-scoop design with a bathing platform to allow easy access from the dinghy which ruled out a transom hung rudder. Similarly, it meant that mounting the servo-pendulum self-steering gear would be unnecessarily complicated.

Spade Rudder

The spade rudder is the most efficient of all sailboat rudders, which is why you're unlikely to see any other design on racing yachts.

The absence of a skeg means that all of its area is used to apply a turning force to the hull, minimizing wetted area and associated drag.

The area ahead of the stock helps to balance the rudder, making life easier for the helmsman.

But it's not the most robust design, being entirely dependent on the strength of rudder stock to resist impact damage.

Theoretically it's just a matter of engineering, but high performance spade rudders just aren't thick enough to incorporate a rudder stock of sufficient diameter for ultimate security.

Skeg-Hung Rudder

Other than those rudders hung on the following edge of long keels, the skeg hung rudder - supported top and bottom on a full length skeg - is the most robust design.

Without a portion forward of the stock, there's no balancing force to take the load of the helmsman's arms - so loads can be quite heavy in some designs.

Nevertheless, it's a very popular design for offshore cruising boats.

Semi-Balanced Rudder

This design of sailboat rudder is something of a compromise between the spade rudder and the full skeg rudder.

Supported at its mid-point by a half-depth skeg, it benefits by the area forward of the stock, below the skeg.

This applies a balancing force as the rudder is turned making the steering lighter than it would otherwise be. And it was this design we chose for Alacazam's rudder.

Making Alacazam's Rudder

A typical productions boat's rudder is likely to have been fabricated as shown here, with two GRP mouldings 'clamshelled' around a foam core.

Not the most reliable arrangement you might think - and you'd be right.

We wanted something a little more robust for Alacazam's rudder.

But first, the rudder stock.

We fabricated this from a 2" (50mm) diameter stainless steel solid bar and welded on flat stainless tangs that would be embedded within the rudder.

The Admiralty Bronze casting will eventually connect the rudder to the skeg.

With the rudder stock fabricated, we began the construction of the rudder core.

It was made up from half inch (12mm) marine ply sheets, cut to shape and incorporating cut-outs for the tangs, screwed and glued together.

The rudder and skeg was built up as a single unit at this stage.

The rudder design software generated coordinates for various stations along the rudder, and we used these to cut templates so that we could get the shape right.

Shaping the rudder profile was done by hand, initially with a plane to remove the excess, then with a file and diminishingly coarse grades of sandpaper.

Once the rudder profile matched the appropriate template we removed the section that would form the skeg.

Next, the rudder was fitted to the stock with any gaps between the tangs and the ply taken up with high-strength epoxy 'gloop'.

Finally both the rudder and the skeg were sheathed in several layers of epoxy-glass rovings before being filled and faired with epoxy fairing compound.

Fitting the Sailboat Rudder

The skeg was letter-boxed through a slot cut in the hull, securely braced internally and bonded to it with fillets of high-strength epoxy and epoxy glass rovings.

Inside the hull we had constructed a GRP tube to contain the stock, and the skeg was also bonded to the lower end of that.

The rudder was then securely fitted to the stock via the bronze bearing, and located at the top of the rudder by a stainless steel bearing.

That's it, we now have a very robust and efficient rudder securely attached to Alacazam's hull.

Recent Articles

A Hunter Passage 42 for Sale

Jul 16, 24 01:41 PM

The Wauquiez Centurion 40 Sailboat

Jul 15, 24 04:50 AM

The Elan 431 Sailboat

Jul 13, 24 03:03 AM

Here's where to:

• Find  Used Sailboats for Sale...
• Find Used Sailing Gear for Sale...
• List your Sailboat for Sale...
• List your Used Sailing Gear...

Building Alacazam...

But why go to the bother of building your own boat?

Copyright © 2024  Dick McClary  Sailboat-Cruising.com

Better Sailing

Full Keel Vs Fin Keel On Sailboats

There are many types of keels, but the main two categories are Full and Fin Keels. Traditionally, cruising boats had a full keel, and that made them very stable in the water. This design prevailed for decades until the industry began to realize the emergence of a new type of consumer, the weekend vacationer, or sailor. For this new client, those high benefits were not a priority because rarely, if never to say, would he move away from the coast.

What is the Keel For?

Sailboats have keels to reduce the amount of slippage to leeward (the opposite side of the boat the wind is coming from). In essence, the keel of a sailboat has the function of compensating the action of the wind on the sails, preventing dejection, converting that force into thrust, and making the ship stay on course. As a general rule, the heavier and deeper a keel is, the more stable a boat is. 

Full Keel or Fin Keel?

Each keel shape has advantages and disadvantages, you will never have the “perfect” keel for your boat. But, the best keel for you and your boat completely depends on the style of sailing that you are planning on doing. 

Full Keel Sailboats

Although full keels are by far the least efficient design, they offer incredible strength and versatility. If we want to explore new waters in which we could run aground, or travel offshore, a complete keel will keep our backs better than any other. One thing is certain though, a full keel will never fall off your boat as a fin keel can.

Full Keel Advantages: 

• Handles better in tough weather
• Better directional stability
• Maneuver well in downwind conditions
• Better for offshore sailing and ocean passes
• Their movements are softer to be more in tune with the movement of the sea itself.
• Since the full keel runs through the entire hull, the forces exercised on it are transferred to a very large area, so it is often said that they are more robust.
• Thanks to their shape, they respond better to an impact against the bottom than a boat with fin keel, which could be seriously damaged.
• The rudder and propeller are more protected against a possible collision.
• If you stranded with a complete keel sailboat, the forces will be well distributed, the damage will be (in theory) minimal and your biggest concern (although not small) will be to see how to get the boat out of there.
• More stable when sitting still at anchor

Full Keel  Disadvantages : 

• Slower compared to a fin keel boat
• Handles poorly in winward conditions
• Usually more cramped than fin keeled boats.
• The turning radius is larger, which makes maneuvering in tight spaces difficult, and turning them with a weak wind can be difficult.
• You have to help more with the engine, which translates into increased wear and an increase in fuel consumption.

Fin Keel Sailboats

The fin keel is, by far, the most common type in modern sailboats. A fin keel is a flat, narrow and hydrodynamic piece located under the hull. Unlike the running keel, it is not an integral part of it but is screwed to it. To compensate for the relatively small ballast it provides, the fin keel is usually deeper.

Fin Keel  Advantages:

• They are faster than full keel boats
• They maneuver better
• Better for daysailing
• Less resistance to rudder rotation
• Short turning radius
• They usually fit better with tight schedules, such as weekend cruises.

Fin Keel  Disadvantages : 

• Less robustness and have to be repaired sooner.
• They offer less lateral resistance, which can lead to a strong and sudden heel when a wave or gust of wind hits the boat.
• They do not keep their course as well as a full keel boat and demand more effort and attention at the helm.
• The rudder is more exposed and is more vulnerable to shock and material fatigue. In this sense, an important variation of the rudder is the rudder with skeg. The skeg is a sturdy element that offers support and protection to the rudder.
• If we are stranded with a sailboat with a fin keel, we can find cracks or fissures at the junction of the keel with the hull.

Full Keel Vs Fin Keel – Summary

It is said that fin keels are made to outrun a storm and full keels ara made to weather a storm. So, a full keel sailboat will be slower but more stable during bad weather where a fin keel will be faster but more unstable. A fin keel boat will not have a problem sailing during a storm and you will make it out just fine but you will not be as comfortable or “safe” as in a full keel boat.

Your choice also has to do with the length of the boat you will buy. A very small boat will benefit from a full keel and heavy displacement in terms of seaworthiness and safety. However, a small boat with these characteristics will be a slow one. If speed and time are not your concerns then maybe a full keel is a better match for you.

Like so many things in sailing, there are many tradeoffs in this particular choice, and only you can decide what’s best for you.

So, as you can understand, there not a clear winner in this competition. The answer to this question really does depend on what is the purpose of the boat’s design and your individual needs. Will you be using your boat to cruise, make passages, offshore cruising, offshore racing, coastal racing, etc? You first need to answer these questions and get a boat the checks most items on your “wish list”.

Peter is the editor of Better Sailing. He has sailed for countless hours and has maintained his own boats and sailboats for years. After years of trial and error, he decided to start this website to share the knowledge.

Related Posts

Sailing with Friends: Tie Knots, Navigate the Seas and Create Unforgettable Memories

Atlantic vs Pacific: Which is More Dangerous for Sailing?

The Ultimate Guide to Choosing the Best Fishing Line for Trolling

Lagoon Catamaran Review: Are Lagoon Catamarans Good?

• Buyer's Guide
• Destinations
• Maintenance
• Sailing Info

Hit enter to search or ESC to close.

Visit our Popular Forums

• Monohull Sailboats
• Multihull Sailboats
• Powered Boats
• General Sailing
• Antares Yachts
• Fountaine Pajot
• Lagoon Catamarans

Cruising Business

• Boat Classifieds
• General Classifieds
• Crew Positions
• Commercial Posts
• Vendor Spotlight

Life Aboard a Boat

• Provisioning: Food & Drink
• Families, Kids, & Pets Afloat
• Recreation, Entertainment, & Fun
• Boat Ownership & Making a Living
• Liveaboard's Forum

Seamanship, Navigation & Boat Handling

• Seamanship & Boat Handling
• Training, Licensing, & Certification
• Health, Safety, & Related Gear
• Rules of the Road, Regulations, & Red Tape

Engineering & Systems

• Const. / Maint. / Refit
• Product / Service Reviews
• Electronics: Comms / AV
• Electrical: Batts / Gen / Solar
• Lithium Power Systems
• Engines & Propulsion
• Propellers & Drive Systems
• Plumbing / Fixtures
• Deck Hdw: Rigging / Sails
• Aux. Equipment & Dinghy
• Anchoring & Mooring

Photo Categories

• Member Galleries
• Life Onboard
• Sailing in the Wind
• Power Boats
• Cruising Destinations
• Maint. & Boat Building
• Marine Life
• Scuba Diving & Divers
• General Photos

Recent Photos

Listing Categories

• African Cats
• view more »
• Crew Wanted
• Crew Available
• Enhance Your Account
• Meet the Mods
• Meet the Advisors
• Signup for The Daily Cruiser Email

> > Please support our sponsors and let them know you heard about their products on Cruisers Forums. 01-09-2015, 18:35   Boat: S&S Loki Yawl 38' designs, attached to the , skeg hung and free standing spade. Based on the I have done so far, along with my own personal experiences, here is what I have so far. Attached (to aft end of the keel) : Works similar to the flaps on an aircraft by altering the camber of the rudder/keel assembly. The advantages I see: Best rudder protection. Unlikely to catch lines, pots etc. The rudder shaft angle can be set up with the bottom of the rudder forward and the tope aft which reduces effectiveness while upright, but makes the rudder more effective when the is heeled and the rudder is highly loaded and more control is needed. The rudder shaft angle of the other two types are rudders seem to be either vertical or raked aft at the bottom, which looks nice but does reduce the rudder effectiveness when heeled. This kind of a rudder can be operated at large angles if needed (with a drag penalty) so little chance of losing control so long as you are strong enough to turn it. Disadvantages are pretty well known, cannot be easily balanced so has high torque loads as compared to a spade, lower efficiency and the largest turning radius of the three rudder types. Skeg hung rudder: Again, the moveable rudder and the skeg act together as in the hung rudder providing variable camber. Advantages: Improved manuverability as compared to a keel hung rudder if properly designed. If a full skeg is used, the rudder cannot be balanced but retains much of the protection that the keel hung rudder has so long as the skeg is substantial. From the I have done so far , these types of rudders stall between 24-27 degrees however it appears that while the drag increases significantly when stall is reached, the rudder apparently remains effective so control is maintained despite reaching stall according to the data I have seen. If anyone feels that this is incorrect please let me know since I don't have much personal experience with the skeg mounted rudder design and I have been looking at a with this type. Disadvantages: This type of rudder is apparently roughly 30-40 percent less efficient than the spade, hence the rudder/spade combination results in more overall wetted surface to generate the same turning moment as a spade rudder. Spade rudder: This is the full flying foil. It is the most efficient of the three rudder types and provides the best manuverability both going forward and reverse. This control is further improved since it is relatively easy to position the prop wash close enough that it is quite effective. The spade is structurally the most challenging to build but the seems to be getting better with time. This free standing design is the least protected and tends to catch lines, pots etc. It is sometimes possible to catch something between the top LE of the rudder and the which can potentially lock and disable the rudder. It appears that depending on the foil used and the thickness ratio that the stall angle is between 14-17 degrees for these rudders which is about 10 degrees less than the skeg mounted rudder. Stalling this rudder type per the data I have seen and also from my personal experience can result in a loss of control, it seems that there is no free lunch in boat design! Any input appreciated! James 01-09-2015, 19:55   Boat: Alloy Peterson 40 simmilar to yours. If it was me I'd go a strong, well engineered spade rudder. And maybe keep some of the old rudder as a trim tab. Trying to add a skeg to an old wooden boat is asking for problems. What is it you are trying to achieve? More speed, control, or maneuverability? Or all three? Another approach would be to add an auxiliary rudder suystem like a or scanner . This mod looks very well done Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app 01-09-2015, 20:10   Boat: 1962 Columbia 29 MK 1 #37 , a spade rudder is a must. But since I have seen a big spade rudder snapped clean off of a big boat I now look at all spade rudders with suspicion. I like my keel hung rudder. The matter of balance is important though so windward is not forcing you to yank on the tiller and effectively put on the brakes. Skeg hung is probably the best design for cruising. 01-09-2015, 20:45   Boat: CSY 44 Tall rig Sold! , skeg hung rudders are my favorite choice if they are build it for the task,,, i can live with the lack of maneuverability v spade rudder, after all its a small to pay ... 01-09-2015, 20:54   Boat: S&S Loki Yawl 38' so the purpose of opening this discussion was to get some opinions on rudder design. Thanks for the link. James or scanner . This mod looks very well done Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app 01-09-2015, 21:13   Boat: S&S Loki Yawl 38' but it looked like a construction issue rather than design lots of foam and almost no glass. While I do feel that the keel hung rudder has the potential to be the most protected and reliable, I think that the engineering is available to make any of these rudders reliable structurally. There seems to be quite a bit of information online regarding spade rudders ,but I am not finding a lot of data on the skeg hung despite there being quite a few designs that use that type. The idea of having a very manuverable (spade rudder) boat is certainly tempting to me but having reliable steerage under all conditions is probably higher up on my list. Most of my sailing has been with keel hung rudders and I have never experienced a loss of control despite some pretty bad conditions. It would be great to hear others experiences, especially under heavy conditions with the spade and the skeg hung rudders. Thanks, James is not forcing you to yank on the tiller and effectively put on the brakes. Skeg hung is probably the best design for cruising. 01-09-2015, 21:26   Boat: Belliure Endurance 35 which is great when you're in a seaway and the stern is lifting over crests, as it lets the rudder maintain bite in the . 2: In a grounding, the rudder moves up off the ground as it is lifted from below and turns, letting the keel take the punishment. 02-09-2015, 05:22   Boat: Alloy Peterson 40 with all three types. My boat has what is basically a spade rudder with a vestigal skeg/bustle. I think the biggest advantage of the spade is the excellent control while reversing, and the tight turning circle. None of the other types come close, This makes a huge difference to manoeuvring in a tight marina. Another benefit is simplicity, no underwater fittings like pintles to give problems, but of course it lacks the brute strength of a very well built skeg or keel hung rudder. But from an engineering perspective a spade is very simple, and its hard to properly and build a skeg to transfer the load properly into the (rather it's not hard, but often not done properly). A fair few boats and glass boats have had issues at the skeg root. Attached rudders tend to be more vulnerable in a grounding, due to the fact that the rudder is often the full of the keel. The balance of a spade also gives a light helm as long as the bearings don't bind at speed due to the rudder flexing. A hybrid rudder (semi balanced), half skeg/ half spade works well but is more complex overall. Another Pro for the spade is the ability to sacrificial bottom section, and front to absorb impact without totalling the rudder. The Dashews seem to engineer them well. If I was going to pick my ultimate rudder it would be some sort of super strong transom hung spade rudder (with crush zones) in a lifting cassette like some of the open 60's and catamarans are going for. I'd carry a small spare, and have the stern with a watertight bulkhead forward of the rudder so it can't flood the boat even if it gets ripped off. Something like a centreline version of these. centreline rudder. Also you get no prop wash unless you have twin engines or 3 rudders. The linkages also get complex. But really its hard to separate the rudder question from the rest of the design. Two of my favorite boats are a Atkins Eric (basically a wetsail 32) and a Young 88 (Lightweight, fin keel, spade rudder, hull). Both poles apart, and both very good boats in very different ways. 02-09-2015, 05:57   Boat: Island Packet 38 02-09-2015, 06:53   with all three types. My boat has what is basically a spade rudder with a vestigal skeg/bustle. I think the biggest advantage of the spade is the excellent control while reversing, and the tight turning circle. None of the other types come close, This makes a huge difference to manoeuvring in a tight marina. Another benefit is simplicity, no underwater fittings like pintles to give problems, but of course it lacks the brute strength of a very well built skeg or keel hung rudder. . 02-09-2015, 07:16   Boat: S&S Loki Yawl 38' effectiveness? I am thinking that the upper portion might not stall until a higher AOA than the lower portion? There might also be some sealing benefits to the arrangement at the top of your rudder as well. Rudder ventilation (especially on transom hung rudders) seems to be an issue that comes up quite a bit. I have also seen some keel mounted rudders that were designed to be almost the same as the bottom of the keel but most are not. Often times keel hung rudders have a mid point bearing so that even if the heel bearing is torn off the rudder retains enough support to remain useable. I have seen a few boats that ground on the rocks or to the point of dropping the internal ballast that still had a serviceable rudder. The construction of a strong skeg seems to be complicated by having an aperture cutout. Also the portion of the rudder aft of the aperture would not benefit from being skeg mounted. James I could be happy with a well engineered and designed boat with any of these rudder types. And iv'e owned and sailed offshore with all three types. My current boat has what is basically a spade rudder with a vestigal skeg/bustle. I think the biggest advantage of the spade is the excellent control while reversing, and the tight turning circle. None of the other types come close, This makes a huge difference to manoeuvring in a tight marina. Another benefit is simplicity, no underwater fittings like pintles to give problems, but of course it lacks the brute strength of a very well built skeg or keel hung rudder. But from an engineering perspective a spade is very simple, and its hard to properly engineer and build a skeg to transfer the load properly into the hull (rather it's not hard, but often not done properly). A fair few boats and glass boats have had issues at the skeg root. Attached rudders tend to be more vulnerable in a grounding, due to the fact that the rudder is often the full depth of the keel. The balance of a spade also gives a light helm as long as the bearings don't bind at speed due to the rudder flexing. A hybrid rudder (semi balanced), half skeg/ half spade works well but is more complex overall. Another Pro for the spade is the ability to engineer sacrificial bottom section, and front to absorb impact without totalling the rudder. The Dashews seem to engineer them well. If I was going to pick my ultimate rudder it would be some sort of super strong transom hung spade rudder (with crush zones) in a lifting cassette like some of the open 60's and catamarans are going for. I'd carry a small spare, and have the stern with a watertight bulkhead forward of the rudder so it can't flood the boat even if it gets ripped off. Something like a centreline version of these. centreline rudder. Also you get no prop wash unless you have twin engines or 3 rudders. The linkages also get complex. But really its hard to separate the rudder question from the rest of the design. Two of my favorite boats are a Atkins Eric (basically a wetsail 32) and a Young 88 (Lightweight, fin keel, spade rudder, hull). Both poles apart, and both very good boats in very different ways.[/QUOTE] 02-09-2015, 07:44   Boat: Taswell 49 Cutter 02-09-2015, 08:10   Boat: Holman & Pye Red Admiral 36 rudder blade was made in 2 and basically "glued" to the rudder shaft tabs, and the blade would come "unglued". These were generic problems made when the boat was originally designed. Plus with the rudder stock within the blade design you can't inspect the stock or tabs or the joint to see how everything is survival over the years. Since we are going to be going to very out of the way locations, we had a new solid rudder made - much like on boats and boats. It is made out of 1/4" plate SS - no foil section. It does have re-inforcing ribs that foil sections could be added to at a later date, but we have found that it works fine as is. The SS rudder shape has the same exterior outline as the fiberglass one. We extended the solid 1-3/4" rudder stock to the full length of the rudder blade and changed the design of the lower rudder bearing into a bolt on 2-piece bearing. Since the overall rudder assembly is extremely long, we installed a shaft coupling right above the rudder arm so the rudder can be removed in 2-pieces - the blade from below and the upper shaft from above. Since we have a , I was able to use the rudder plate as out ground plate and the performance has greatly improved. Since the rudder is 2-piece, we were able to weld a tiller fitting directly onto the upper rudder bearing and rudder shaft. The new rudder steers very easy and controls the boat better than the old fiberglass one. Plus it is extremely easy to on/remove/maintain the new rudder. Since everything on the new rudder is solid 316 SS, it wasn't , but compared to other rudders was not to outrageous - and it will never break. Design, material and fabrication came to about $10,000. 02-09-2015, 08:26   Boat: Holman & Pye Red Admiral 36         02-09-2015, 09:23   Boat: Taswell 49 Cutter , , Thread Tools Rate This Thread : Posting Rules post new threads post replies post attachments edit your posts is are code is are are are Similar Threads Thread Thread Starter Forum Replies Last Post Dave6330 Monohull Sailboats 16 28-07-2013 03:17 mudness90 Construction, Maintenance & Refit 2 24-11-2011 07:06 GordMay Construction, Maintenance & Refit 1 16-08-2005 14:04 - - - - - - - Privacy Guaranteed - your email is never shared with anyone, opt out any time. RetireFearless Rudder Types for Sailboats A rudder is a one-of-a-kind technological achievement for sailboats. There are a handful of rudder types for sailboats to allow sailors to steer. March 16, 2023 This article may contain affiliate links where we earn a commission from qualifying purchases. Today’s sailboats use various rudders that serve unique purposes in steering or performance. You are probably wondering which rudder type you have on your boat and which one is best. There are four types of rudders, which are skeg, spade, outboard, and full. Depending on the size of the boat and the hull will determine which rudder it will need. In addition, each rudder type will have a slight variation that will meet certain expectations of performance on the boat. Sailors need to rely on a rudder in order to steer their boat efficiently. Each boat will not have the same rudder, as different styles of sailing require different rudders. According to experienced sailors, each rudder has its pros and cons. However, the best rudder needs to match your expectations in sailing. Table of Contents ‍ Rudder Types With the four rudder types mentioned, each one will have its pros and cons. As you begin your travels on bluewater or are interested in learning more, then it would not hurt to check out what each rudder is designed to do. Full Keel Rudder If you were to picture a sailboat with a rudder, it would likely be a full keel rudder. The most common rudder type is the full since a lot of sailboats use a full keel. The reason a full keel is the most common keel on a sailboat is that it is the best one to provide stability. In that case, you need a rudder that can accommodate that type of boat. On a full keel sailboat , the rudder looks like it is part of the keel itself. It is actually attached on a hinge, giving it the appearance that it is fully connected to the keel. Advantages of a Full Keel Rudder A full keel rudder is quite strong and actually helps tremendously with the protection of the boat. During a strong storm or harsh waves, it can be easier to navigate with this type of rudder. In addition, debris is significantly less likely to snag on anything like other rudders. Disadvantages of a Full Keel Rudder While a full keel rudder might be the best one to handle in strong storms, it is still the most difficult rudder to handle. Since the flow of the water is providing pressure on the full keel, it makes it harder to move the rudder. You would need to put a lot of effort into steering, especially in harsher conditions. Skeg Rudders Skeg rudders might give a full keel rudder a run for its money due to its durability. These are often referred to as skeg mounted rudders. These are similar to full keel rudders, but can also be used on fin keel boats . This alone gives it a slight edge over full keel rudders, but each boat design will differ. Advantages of a Skeg Rudder With similarities to a full keel rudder, you are going to have the stability as well in a skeg rudder. The added bonus is that it works in either a full keel boat and a fin keel. Disadvantages of a Skeg Rudder Just like a full keel rudder, all of the pressure of the water hits on one side or the other. This means it will be hard to turn in rough conditions. Spade Rudders These rudder types are best fit for a fin keel boat rather than a full keel or to the types of boats. It enters straight down into the water and can rotate left or right using a post that extends within the hull. Advantages of a Spade Rudder The best advantage of a spade rudder is that it can be part of the fin keel. You can turn this rudder much easier than a full keel rudder or skeg rudder. The water is not forced one side or the other, allowing a better flow and easier turn. Disadvantages of a Spade Rudder If you sail upon a lot of debris in the water, you are likely going to damage the rudder. These are more delicate than skeg or full keel rudders, as they are more exposed. Debris can get caught in between and potentially wrapped within the space rudder. In addition, rough water can be a nightmare. Tough conditions can cause enough pressure to bend or potentially break the rudder. Outboard Rudder Outboard rudders are not attached to the boat’s hull and are mounted outside at the back . Typically, these are not connected to a steering wheel and are connected by a tiller. A tiller is a steering lever that can take some getting used to if you have solely used steering wheels. On smaller boats, sailors actually like a tiller over a wheel. Advantages of an Outboard Rudder If an outboard rudder becomes damaged, it will not typically affect the rest of the boat. This is because there is not a rudder post through the hull. In the event that you damage it while at sea, you have the opportunity to fix it. Since it is on hinges and not attached to the hull, it might be able to be fixed. This also means the rudder might be stronger than other rudder types. Disadvantages of an Outboard Rudder Since the outboard rudder is at the back of the boat, it is vulnerable in some situations. If floating debris or something like a rope is in the water, it can tangle up in the rudder or damage it. The location of the rudder also makes it harder to turn than a spade rudder. In tough conditions, this might be difficult to turn. Purpose of a Rudder A rudder is one of many important components of a boat to operate as efficiently as possible. Some boats are built for speed and others for comfort, so a rudder also has to fit that category. Water pressure will dictate how the rudder moves in the water. Whichever direction you turn the rudder, then water pressure will push against it and allow you to turn. While a sailboat is turning, it is pivoting around a middle point of the boat. The stern and bow move at the same time, while the middle point of the boat remains in place. Knowing how to properly operate a rudder to steer can make a huge difference in avoiding a crash. Variations of Rudders While some rudders are fairly cut and dry for their intended use, other rudders have slight variations to the design. This allows a little bit of flexibility on some boats, which is great because not all boats are designed the same. Balanced Rudder A balanced rudder is a form of a spade rudder with a slight difference in free space at the top. The leading edge allows rotation from one side of the boat while the trailing edge goes opposite. The post is also a few inches back from the front of the rudder, which is slightly different from a regular spade rudder. Even though the turning action is roughly the same in comparison to a spade rudder, the force on the helm has more balance and makes it easier to steer. You will usually see this type of rudder in performance boats or yachts. Furthermore, they are always paired with a fin keel to provide the best performance overall. The only drawbacks to a balanced rudder is that it is susceptible to debris if you were to run anything over in the water. You have to rely on the structural integrity and hope that it is strong enough to take a blow. If it were to fail, it does not revert back to the center and might make it difficult to navigate the boat. Unbalanced Rudders Unbalanced rudders have the support from a full length skeg and are attached to the furthermost point of their span. It is unbalanced because the entire rudder is aft of its axis or the centerline where the rudder stock is located. When you begin turning this rudder type, you get all of the force on one side. Whoever is steering the boat will notice this feeling compared to other rudder types, especially when using a tiller. As you can gather, these rudder types are not commonly used today. You might find one used in history books or replicas of older boats. If this were commonly in use today and were to fail at sea, the rudder remains in place and not go back to the centerline. This caused serious issues in the past and arguably why it is not very popular anymore. Semi-balanced Rudders If you can picture what a balanced and unbalanced rudder would look like, then a semi-balanced rudder is something in between. The name suggests that it is partially balanced and unbalanced at times. The top part of the rudder is unbalanced, while the lower part is balanced. With the top part being this way, it helps by providing structural support to the rudder by aiding in vertical displacement. During this process, the balanced section will endure less torque pressure during swings. It will then return back to the centerline if the steering equipment fails, which is a critical aspect that balanced and unbalanced rudders did not originally have. Semi-balanced rudders are also different from other types since they vary in size and shape. You will often hear sailors talk about the depth of the horn, which is the connection between the rudder and the boat. A shallow horn rudder has a horn that extends less than half of the chord length from its top. In a deep horn rudder, the horn extends more than 50 percent of its chord length from the top. Semi-balanced rudders have had some unique innovations over the years. They appear to be the best of both worlds between balanced and unbalanced. Twin Rudders Twin rudders have been used since 1980 among racing boats. Over the last decade or so, they have increased in popularity among cruising sailboats. Twin rudders have a history of being difficult to operate in tight spaces if you do not have experience with them. This is true, especially since it navigates a little differently than one rudder. When using a boat that has a twin rudder, the prop wash moves by both rudders and you cannot have the same maneuverability as with one rudder. One tactic you could do is to increase your boat speed to increase water flowing between the rudders. In doing so, it could cause some concern in tight spaces if you are unable to land exactly where you want. One positive to twin rudders is that it performs well in reverse. You do not have as much prop walk as other boats and can handle better in lower speeds due to increased blade length on both rudders. Another benefit is that it responds better to the wind. In single rudder boats, the wind can push the bow in one direction while the stern goes opposite. For twin rudders, the wind does not have as much of an impact in that regard. Can Rudders Fail While in Use? Just like anything in life that you use, it has a lifespan on it. For a rudder, some can fail while you are using them at sea. Rudders failing at sea is actually a common hazard, so knowing what to do in that situation is very important. Sometimes cheaper boats, like a fiberglass boat, will experience a rudder failure likely before a more expensive boat. The material of the rudder pole has to be a good blend of flexibility and strength. If it is too weak, it will break. If it is too strong, it might damage the hull since it cannot flex properly. The framework inside the rudder should be a heavy-duty metal, because if it breaks, then it will be unusable. This is likely the case in cheaper boats, where costs have been cut in certain areas. Depending on the boat brand, you might see welding jobs that are not executed properly for rudders. In addition, the type of rudder you use at sea can make a big difference. Full keel rudders might be the best option since it is protected from debris and offers the best stability. Depending on your sailing goals, the right rudder type will be different for everyone. What are Rudders and Stocks Made out of? Rudders have historically been crafted out of heavy duty stainless steel or aluminum. You want something that is non-corrosive and can withstand some beating. If you were to look at high performance yachts, these typically have alloy since it is lighter but also strong. Stainless steel can handle swelling and debris, but crevice corrosion could be an issue. Composite is another material that is used in mass production yachts or high performance boats. Some material is arguably better than others, but there is really not a perfect option out there. A proper inspection is needed before doing any long term use at sea. Why a Tiller Could be Better than a Wheel for Rudders If you have sailed a boat with a steering wheel and have never used a tiller, you could be missing out. Regardless if you are new to sailing or a seasoned pro, a tiller is very easy to use. Tillers provide instant feedback when turning a boat, whereas steering wheels take a minute to get results. For newer sailors, a wheel could prove to be frustrating in rough conditions. Depending on the size of your boat, a wheel might be the better option. In larger boats, a tiller does not perform the same. Even though a tiller is harder to turn, it still offers an immediate reaction. This is why you will oftentimes see tillers on racing boats because they provide instant feedback. What Happens if Your Rudder Fails? While safety is a priority in everything you do while sailing, there are some situations you cannot avoid. No matter how much preventative maintenance you do, your rudder might still become damaged or unable to use. If bearings have seized, the rudder can become difficult to move at first but will eventually lock up. Your steering capability will eventually be impossible and quite difficult to stop the boat from rounding into the wind. If it were to fall off completely, then you will have quite a difficult time tracking the boat. The rotation of the boat might even be abrupt or rapid. It is important to stay calm during a situation like this and to check on the crew. Drop your sails and attempt to gain some control. You could even try pointing the bow into the wind and dropping anchor to reduce motion. Once the boat is under control, check for damage and call for assistance. If you cannot phone for assistance, the best thing you can do is to create a makeshift rudder or potentially purchase one before a situation like this happens. For example, brands like Seabrake and Delta Drogue are quality rudders you could use in a pinch to safely make it back to shore. Recent Articles What Size Sailboat Can One Person Handle? How To Tie A Sailboat To A Mooring Ball Ring What Is The Ideal Wind Speed When Sailing? How To Use a Sailboat Winch Things You Need To Liveaboard a Sailboat Types of Sailboat Keels I'm Michael Moris. I've been sailing my whole life, and it has taken me to places I never imagined. From the Caribbean to Europe, from New Zealand to South America - there's nowhere that hasn't felt like home when you're on a boat! Trending Articles How Far Is Havana From Miami By Boat? Yachting Vs Sailing Who Is Sailing Doodles? Subscribe To Our Newsletter Thank you! You're signed up for our free newsletter! Oops! Something went wrong while submitting the form About Our Team We are a publishing team of licensed Nursing Home Administrators, Nurses, Assisted Living Directors, Health Professionals, Gardeners, and individuals with vast experience with senior living and activities. ©2024 Retire Fearless. All rights reserved. We can be reached via email at [email protected] Retirefearless.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. This site also participates in other affiliate programs such as CJ, ClickBank and more, and is compensated for referring traffic and business to these companies. Facebook Pinterest Log in or Sign up You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser . Rudder on long keel Discussion in ' Boat Design ' started by pitbull , Jan 26, 2022 . pitbull Junior Member I've been reading a few old books regarding long keel boats (like channel pilot cutters) and some advocate a vertical rudder post (when viewed from the side) and others a rudder post that rakes forward the deeper it goes. For example, advocating a strongly raked sternpost (45 degrees) the designer of Jolie Brise, Paumelle, is supposed to have said: [when] There's a sea coming up behind you and your bow's dipped and the stern comes up, that's the time you want your rudder to be most effective. Hiscock seems to suggest that the only benefit of a raked rudder is to remove some of the deadwood and reduce wetted surface. Indeed if the rudder is raked too much it gives difficulty steering (30 degrees should be fine). I don't have enough sailing experience to know, how much rake is desirable and why ? Raked to trim underwater area and to move the rudder farther under the boat to mitigate the stern rising to a wave ? Or vertical to keep the turning force farther aft ? What are your thoughts please ?   wet feet Senior Member Nothing to do with rudders,but I would suggest that no boatyard would be particularly pleased to see a boat that posed such a challenge to chock up ashore.A straight portion of the keel would make their lives a bit more straightforward and in consequence,your bills would be a bit smaller. A couple of other things stand out from the images:the mast is a very long way aft and what the old time designers referred to as the master section has a lot of rake in plan view. The normal design spiral begins with the requirements of the boat and it's function and then uses the parameters thus defined to give a starting point for an initial version,which then goes through a number of iterations.What particular duty is the boat intended for?   gonzo Senior Member The application should drive the design. For example, a boat that is hauling nets may benefit from a rudder that is not protruding from the stern.   mc_rash Senior Member @pitbull could you provide us with a section view?   In my eyes the innerst buttock line could be moved little upwards and thus also the keel which would lead to reduced wetted area/resistance. Also compared to old pilot cutters the keel still looks big IMHO.   philSweet Senior Member I think you are probably looking at the wrong end of the machine. If you need a 9 foot long tiller to steer the boat, it's a lot easier to find room for it if the rudder is raked.   What difference does the rake make? It would be the same distance from the stern and take the same amount of deck space.   If the keel is the same length, rake puts the rudder head further aft. That way, a big tiller doesn't intrude as far.   If the boat is longer, a tiller of equal length leaves more deck space. However, that is not a function of the rake, but the deck length.   @wet feet Thanks for the practical suggestion about chocking up ashore. yes the master section rake was my intention - perhaps I overdid it. Per Skene, the traditional boat keel also seem to like to rake down from bow to stern continuously so that the leading edge is constantly entering solid water all along its length. I have no idea where to put the mast yet - I just found I needed to add one or I couldn't picture the shaded isometric projection of the boat on the bottom right of the lines plan properly. @mc_rash Here are the lines - I have not spent time on fairing yet (I don't know what the stern will look like even) and I have not incorporated any of your suggestions yet. I'm also just learning how to get delftship to do my bidding. 10m long, 3m beam, 1.65m draft, 10 tonnes I found some comments on rudders by Skene - he writes: The raking rudder post gives the best shape of lateral plane and neutralizes the lifting component which a rudder with vertical post has when yacht is heeled. ​ I see his point about removing some deadwood, but I'm not sure I can visualize why it makes a difference to the lifting component, maybe it induces less yaw with the same force closer to midships. He seems to like bow hung rudders too ! Raking the rudder post and pivoting the whole thing aft of the transom seems to be the way to go (Although I have grown fond of her short stern overhang - perhaps not very pilot cutter). The prominent forefoot seems to be a cutter feature, better for heaving-to. I don't doubt it, but never having hove-to I don't have a visceral feel for it. Something to do with the boat being harder to yaw perhaps. Maybe it's time for me to book a sailing holiday on one of those old working boats and get a feel for things.   Oh- and you asked what the boat was for. I have long held on to the dream of building a boat and sailing her across an ocean or two. I had imagined there would be two capable crew on the boat (myself and one other). I am not averse to buying plans but it would be pretty cool to be involved in the whole design. I want to do all this within the next 5 years before I get too old. After I have got that out of my system I'd like something in which I can take my kids (and the grandkids if I am luck enough to get any) out for the occasional sail up and down the coast. It would essentially double as a "cabin on the coast" if I can find a suitable mooring. I live about an hour's drive from the Oregon coast. I'd like a boat that can be easily destroyed at the end of its life, or, if I mess up the crossing, won't leave mounds of plastic waste in the ocean. I am not particularly concerned about resale value, although if it turns out to be worth something I'll accept the offer ! I had not seen this as an investment or a luxury yacht. I want something low maintenance - within the limits of what is feasible in that regard. So few frills. I like the traditional look and there's a lot of living space in it for its length. This is not a reconstruction, I'd like to make sensible use of modern cordage, professionally made sails etc. It does not need to have hand-sewn tanbark flax sails and hemp sheets. I understand the arguments about "sailing fast enough to escape danger" but I prefer something that could stand up to a blow if I were offshore in the wrong place at the wrong time and so I have convinced myself that, other than a desire that it is able to go upwind tolerably well, I have no particular need for a fast boat. The whole point is to make the trip, if I just wanted to get to the destination I would fly there. I have had fun sailing dinghies and catamarans, if I feel the need for a white knuckle ride I'll go back to one. I will need to pick up a lot more sailing skills to be able to go offshore, that will be part of the fun I need a boat I can feel confident in, a gentle-ish motion, wide side decks, good stanchions and handholds, strong and waterproof topsides, ideally a less-homicidal boom.   Rumars Senior Member I wouldn't say your model has a deep forefoot, rather a cut away one. A full keel with a deep forefoot is a boat with a straight stem, like for example a fifie. Anyway, rudder rake is a result of a keel hung rudder and a decision of how much of a skeg you wish to retain. Less skeg results in better maneuverability, more skeg in better directional stability. The goal is to find a balance between this two. Unless you really wish to learn how to design a boat from scratch, I see no reason for you to do it. There are many designs for this kind of boat in the size you want. For example Atkin&Co. has Tally Ho Major, Nutmeg, Pam and Jonquil. Plan prices range from 200 to 400$ (altough they appear to not ship momentarily), cutter, yawl ketch, with or without counterstern. This are old plans, for carvel, without support, you will very much be a part of "designing" it, you need to loft, fair, decide on building techniques, structural details, the entire interior plus the deck plan. You just skip the part where you have to learn how to do all the boring math about weight distribution, sail and lateral area balance, structure, etc.   Advertisement: pitbull said: ↑ I found some comments on rudders by Skene - he writes: The raking rudder post gives the best shape of lateral plane and neutralizes the lifting component which a rudder with vertical post has when yacht is heeled. ​ I see his point about removing some deadwood, but I'm not sure I can visualize why it makes a difference to the lifting component, maybe it induces less yaw with the same force closer to midships. He seems to like bow hung rudders too ! Maybe it's time for me to book a sailing holiday on one of those old working boats and get a feel for things. . Click to expand... Rudder vibrations Help Proa Rudders, from Balkan Shipyards Unusual rudder placement What Characteristics Define a Rudder ? Fiberglass Rudder Shoe New Rudder for a West Wight Potter 19 Changing rudder post angle Rudder Design Rudder area question Rudder Placement and Size in Relation to Prop on Submarine No, create an account now. Yes, my password is: Forgot your password? Posted 2024-07-18 17:10 Contact Information: Sailboat for sale. 17 feet long - $650 (East Greenwich) QR Code Link to This Post post id: 7767449304 posted: 2024-07-18 17:10 ♥ best of [ ? ] refresh the page. Sailboat for sale. 17 feet long - boats - by owner - marine sale -... I am selling a 17 foot sailboat. It needs a few minor repairs but can be in the bay or lake and sailing in no time. Includes: mast, boom with mainsail, 2 jib sails, swing keel, and rudder with... 324 IMAGES Sailboat Keel Types: Illustrated Guide (Bilge, Fin, Full) The Types of Sailboat Rudders Keel design: What’s best? Rudder Options For Lifting Keel And Centerboard Offshore Sailboats Bilge keel What Does The Keel Do On A Sailboat And How It Works VIDEO Rudderless Sailing in a Laser, just messing around in boats Как Одна Шведская подводная лодка, ПОБЕДИЛА ВМС США AD 14, rudder, keel underway Rudder Part 1 Sailing Navigation Secrets 2013 Hunter 33e Hull Design and Bottom Video walk around By: Ian Van Tuyl Yacht Broker California COMMENTS PDF Keel and Rudder Design sailboats. These variations include the "elliptical" keel with shortened root chord and exaggerated midchord lengths. The goal of that design was to reduce the hull-to-keel root chord interference drag. As I'll suggest below, though, there's a better way to minimize drag at the junction of the hull and keel root. The surface of the hull provides a Sailboat Keel Types: Illustrated Guide (Bilge, Fin, Full) Example sailboats with a fin keel: Catalina 30; Hunter 34; Bavaria 40; Jeanneau Sun Odyssey 36.2; Fin keel with skeg rudder. Fin keels with a skeg rudder use a small structural part in front of the rudder to protect it. This design is mostly integrated into the hull, making it less vulnerable, and a great compromise between speed and safety. All About the Rudder on a Sailboat Full Keel Rudder Sailboat. The classic, robust offshore sailboat is designed with a full keel that runs from stem to stern. With this sort of underwater profile, it only makes sense that the rudder would be attached to the trailing edge of that enormous keel. On inboard-powered sailboats, the propeller is usually mounted inside an opening ... Sailboat Rudders Sailboat Rudders. The primary purpose of sailboat rudders is of course to give the helmsman the ability to steer the boat, but a well-designed one will also provide hydrodynamic lift to windward, in the same manner as does the keel. These twin high-aspect ratio rudders on an all-out race boat are clearly optimised for their hydrodynamic ... What Is a Sailboat Rudder? An Overview of Its Function and Design Keel-mounted rudders are attached to the boat's keel, which is the central structural element that runs along the bottom of the hull. Spade rudders are free-standing rudders that are not attached to any part of the boat and are commonly used in racing sailboats. The type of rudder used depends on the boat's size, design, and intended use. Sailboat Rudder Types The spade rudder lies at the aft separate from the keel. A spade rudder is easy to turn because the water rushes both against its fore and aft edges - great for using a tiller. A spade rudder is also fast as the wet area less than a full keel. The boat racing along with less resistance. Spade and partial spades are becoming the most popular ... Introduction to Sailboat Design: a Technical Exploration 3) Keel & Rudder Design. The keel and rudder are critical components of a sailboat's underwater structure. The keel provides stability by preventing the boat from tipping over, while the rudder controls its direction. Keel design involves selecting the keel type (fin, bulb, or wing) and optimizing its shape for maximum hydrodynamic efficiency. What Is a Sailboat Keel and How Does it Work? Sailboat keels usually carry iron or lead ballast in their tip to act as a counterweight to the wind's force on the sails, which reduces heeling. The keel's length acts as a lever, increasing the ballast's effectiveness and improving its stabilizing properties. In other words, the deeper the keel runs and the heavier its ballast is, the more ... How keel type affects performance How keel type affects performance. James Jermain has tested hundreds of yachts in his 30 years as Yachting Monthly's chief boat tester. The performance and handling of a yacht depends on many things, but perhaps the most important single feature is the shape of the hull and the profile of the keel. Over the years hulls have become shallower ... All About the Sailboat Rudder Here's a look at various designs of sail rudder, along with the basics of how it works and why it's there. All About the Sailboat Rudder. By Matt Claiborne. Learn more ... Rudder vs Keel. Learn more. A rudder is there to steer direction and a keel provides stability and enable sailing windward. Keel construction and design explained Attaching the rudder to the keel makes it far less prone to damage from flotsam and fishing pot lines, but the helm feels heavier as a result. Long keels also give a boat great directional stability, which makes them ideal for windvane self-steering, which contributes to their enduring popularity with long-range ocean cruising sailors. Four Types of Rudders On Sailboats The four rudder types are: full rudder, spade rudder, skeg rudder, and outboard rudder. We will discuss the advantages and disadvantages of each. Full Rudder. The full or full keel rudder is at the aft end of a full length keel. The keel-rudder runs along the entire length of the bottom of the boat's hull. Building a Faster Rudder If the boat has an efficient keel and the leeway angle is only a few degrees, the rudder can beneficially operate at a 4-6 degree angle. The total angle of attack for the rudder will be less than 10 degrees, drag will be low, and pointing will benefit from the added lift. Navigating Rudder Types: A Comprehensive Guide for Boaters Full Keel Rudders - Full keel boats are typically equipped with full keel rudders that are built into the hull itself. These heavy-duty rudders provide excellent directional control even in rough waters due to their large size and because they are mounted closer to the centerline of the boat. Skeg-Mounted Rudders The Types of Sailboat Rudders The type of rudder is often related to the boat's type of keel. Rudder on Full-Keel Sailboat . As shown in this photo, the rudder of a full-keel boat is usually hinged to the aft edge of the keel, making a continuous surface. The engine's propeller is usually positioned in an aperture between the keel and rudder. A Look at Sailboat Design: Fin Keels vs. Full Keels When a keel tears away from a sailboats hull, it makes the loss of a rig or rudder seem like a minor inconvenience. History shows that its an uncommon occurrence, but because we now annually hear of such incidents, weve decided to take a closer look at keels and see what keeps the ballast where it belongs. Keel types and how they affect performance Pros: Reduced wetted surface area leading to increased boat speed. Better windward performance and handling than full length keel. Rudder on the aft end of the keel improves self-steering ability on some designs. Cons: Under engine, this keel form has a large turning circle ahead and poor control astern. Making a Sailboat Rudder for an Offshore Yacht This design of sailboat rudder is something of a compromise between the spade rudder and the full skeg rudder. Supported at its mid-point by a half-depth skeg, it benefits by the area forward of the stock, below the skeg. This applies a balancing force as the rudder is turned making the steering lighter than it would otherwise be. What Is A Rudder On A SailBoat and How Does It Work Rudder on a Full-keel sailboat. Full-keel boats or modified full keel boats usually have this type of Rudder. These rudders are typically hinged to the aft edge of the keel to make a continuous surface, not to create any drag after the main keel. Engine propeller is usually positioned between the keel and the Rudder. Full Keel Vs Fin Keel On Sailboats The rudder and propeller are more protected against a possible collision. If you stranded with a complete keel sailboat, the forces will be well distributed, the damage will be (in theory) minimal and your biggest concern (although not small) will be to see how to get the boat out of there. ... Fin Keel Sailboats. The fin keel is, by far, the ... Sailboat rudder design Re: Sailboat rudder design. A couple of more benefits of a keel-hung rudder with an angled post is that: 1: It allows for more rudder in the deeper, denser water which is great when you're in a seaway and the stern is lifting over crests, as it lets the rudder maintain bite in the water. Rudder Types for Sailboats Skeg rudders might give a full keel rudder a run for its money due to its durability. These are often referred to as skeg mounted rudders. These are similar to full keel rudders, but can also be used on fin keel boats. This alone gives it a slight edge over full keel rudders, but each boat design will differ. Advantages of a Skeg Rudder Rudder on long keel Rudder on long keel. Discussion in 'Boat Design' started by pitbull, Jan 26, 2022. Tags: long keel; rudderpost; Joined: Nov 2008 Posts: 11 ... Anyway, rudder rake is a result of a keel hung rudder and a decision of how much of a skeg you wish to retain. Less skeg results in better maneuverability, more skeg in better directional stability. The ... Sailboat for sale. 17 feet long I am selling a 17 foot sailboat. It needs a few minor repairs but can be in the bay or lake and sailing in no time. ... 2 jib sails, swing keel, and rudder with extension handle. No leaks. It's ideal for 1 to 3 people. Trailer also for sale for $550.00. post id: 7767449304. posted: 2024-07-18 17:10. ♥ best of . Avoid scams, deal locally ... catamaran gulet powerboat riverboat sailboat trimaran yacht