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🌊 Unleash Your Boat’s Potential: 7 Secrets to How Hydrofoils Work [2024]

• July 2, 2024
• Hydrofoil Basics

Want to turn your boat into a speed demon? You’ve heard of hydrofoils, those underwater wings that promise increased speed, fuel efficiency, and a smoother ride. But how do they actually work? It’s not just about magic, it’s about physics, design, and the innovative engineering that’s transforming the boating world. In this comprehensive guide, we’ll unveil the secrets behind hydrofoils and how they can revolutionize your boating experience. This is more than just a technical explanation, it’s a journey into the future of boating, where smoother waters and faster speeds are just a hydrofoil away.

Quick Answer

Hydrofoils lift your boat’s hull out of the water, reducing drag and enhancing performance. Think of them like underwater wings that generate lift, similar to an airplane. This revolutionizes your boating experience in these ways:

• 🚀 Increased speed and acceleration: By reducing drag, you can cruise at higher speeds and accelerate quicker.
• ⛽ Improved fuel efficiency: Less drag means you use less fuel to go farther.
• 🛥️ Smoother ride: Hydrofoils minimize the impact of choppy waves, providing a more comfortable experience.

Ready to upgrade your boat? Check out popular hydrofoil brands:

• SE Sport: | Amazon | Walmart | SE Sport Official Website
• Davis Instruments: | Amazon | Walmart | Davis Instruments Official Website

Get ready to transform your boating experience. Read on to discover the secrets of hydrofoils!

Table of Contents

• Quick Tips and Facts
• The History of Hydrofoils and Boats
• How Do Hydrofoils Work on Boats?
• What Are The Benefits of Using Boat Hydrofoils?

What are the types of boat hydrofoils?

• How Should I Choose a Hydrofoil?
• How to Install a Hydrofoil on Your Boat
• Hydrofoils: The Future of Boats?

Recommended Links

• Reference Links

Quick Tips and Facts 🏄‍♀️💨

• Hydrofoils are like underwater wings that lift your boat’s hull out of the water, reducing drag and increasing efficiency.
• They can be added to most boats with outboard motors or sterndrives, including pontoon boats! (Yes, you read that right! Check out this article about VARA® Hydrofoil Kits: The Ultimate Guide to Transforming Your Pontoon or Tritoon Boat 🚤 2024 )
• Benefits include: increased speed 🚀, improved fuel economy ⛽, smoother ride 🛥️, and reduced bow rise for better visibility 👀.
• Choosing the right hydrofoil depends on your boat type, size, and engine. Research carefully or consult with an expert.
• Installation is usually straightforward but requires mechanical skills. If in doubt, get help from a professional.

Ready to fly across the water? Let’s dive deeper! 👇

The History of Hydrofoils and Boats 🕰️

The concept of hydrofoils has been around for centuries, but the first practical hydrofoil boat was built in the early 1900s by Italian inventor Enrico Forlanini. Early hydrofoils faced challenges with stability and control ( source ), but advancements in materials and design have overcome these hurdles, leading to their popularity in recreational and commercial boating today.

The Rise of Hydrofoils in Recreational Boating

The introduction of hydrofoils to the recreational boating market revolutionized watersports. Suddenly, boaters could achieve higher speeds and experience smoother rides, all while using less fuel. This led to the development of hydrofoil-specific boats for racing and leisure, like the iconic Thunderbird Formula 500 .

Modern Hydrofoil Technology

Today, hydrofoils have evolved to be even more efficient and user-friendly. Brands like SE Sport and Davis Instruments offer a variety of hydrofoils designed for different boat types and sizes. These modern hydrofoils utilize advanced materials and hydrodynamic designs to maximize lift and minimize drag.

From humble beginnings to high-tech marvels , hydrofoils have come a long way. And we’re excited to see what the future holds for this innovative technology.

How Do Hydrofoils Work on Boats? 🤔

Picture this: you’re holding a flat piece of cardboard outside a moving car window. As the air rushes over and under the cardboard, it creates lift, trying to push the cardboard upwards. That’s the basic principle behind hydrofoils, but instead of air, they use water.

Here’s a breakdown:

• Lift: A hydrofoil’s curved shape, similar to an airplane wing, generates lift as water flows over and under it. The faster the water moves across the foil, the more lift is produced.
• Reduced Drag: As the hydrofoil lifts the boat’s hull out of the water, the surface area in contact with the water decreases dramatically. This minimizes drag, allowing the boat to glide effortlessly through the water.
• Improved Efficiency: With less drag, the engine doesn’t have to work as hard to propel the boat, resulting in improved fuel efficiency, higher speeds, and a smoother ride.

What Are The Benefits of Using Boat Hydrofoils? 🤩

We’ve touched on some benefits already, but here’s a closer look at how hydrofoils can enhance your boating experience:

• 🚀 Increased Speed and Acceleration: Hydrofoils can provide a noticeable boost in speed, especially at higher RPMs. Get ready to leave other boats in your wake!
• ⛽ Improved Fuel Efficiency: Less drag means less fuel consumption. Enjoy longer trips and save money at the pump!
• 🛥️ Smoother Ride: By lifting the hull above the waves, hydrofoils minimize the impact from choppy water, making for a more comfortable ride.
• 🤸 Enhanced Stability: Hydrofoils can reduce or eliminate porpoising – that annoying bouncing motion that some boats experience at certain speeds.
• 👀 Better Visibility: With the bow lifted higher, you get a clearer view of the water ahead, improving safety.

Not all hydrofoils are created equal. Here are the most common types you’ll encounter:

• Fixed Hydrofoils: These are permanently mounted to the cavitation plate of your outboard or sterndrive. They’re generally more affordable and easier to install.
• Adjustable Hydrofoils: As the name suggests, these allow you to fine-tune the angle of attack for optimal performance based on your load and water conditions.
• Surface-piercing Hydrofoils: Primarily used on high-performance boats and racing craft, these hydrofoils are designed to have only a portion of their surface submerged, reducing drag even further at high speeds.

How Should I Choose a Hydrofoil? 🤔

With so many hydrofoils on the market, selecting the right one can feel overwhelming. But don’t worry, we’re here to help!

Here’s what you should consider:

• Boat Type and Size: Hydrofoils are designed for specific boat types like bass boats, pontoon boats, or ski boats. Boat size and weight also play a crucial role, so choose a hydrofoil that’s compatible with your vessel’s specifications.
• Engine Power: A higher horsepower engine might require a larger hydrofoil to handle the increased lift and forces.
• Intended Use: Consider how you primarily use your boat – cruising, watersports, or fishing? Different hydrofoil designs prioritize specific performance aspects.

Still unsure? Check out our Hydrofoil Equipment Reviews for in-depth analyses of popular models. Our team of experts rigorously tests and provides unbiased recommendations.

How to Install a Hydrofoil on Your Boat 🔧

For the mechanically inclined, installing a hydrofoil is a fairly straightforward process. However, it does require some basic tools and knowledge.

Here’s a simplified overview:

• Consult Your Owner’s Manual: This is crucial to determine the correct positioning of the hydrofoil on your specific outboard or sterndrive.
• Gather Tools and Materials: You’ll need wrenches, a socket set, a torque wrench, marine-grade grease, and potentially a drill.
• Position the Hydrofoil: Align the hydrofoil with the cavitation plate using the markings provided by the manufacturer.
• Secure with Bolts: Insert the bolts through the pre-drilled holes (or drill holes if necessary) and tighten them gradually, alternating sides.
• Apply Marine Grease: Coat all metal-to-metal contact points with marine grease to prevent corrosion.
• Torque to Specifications: Ensure all bolts are tightened to the correct torque specifications outlined in your owner’s manual.

⚠️ Remember, if you’re not comfortable with these steps, always consult with a qualified marine mechanic for assistance.

For a visual guide and more detailed instructions, head over to our Hydrofoil Basics section. You’ll find step-by-step tutorials, videos, and helpful tips to make the installation process a breeze.

Hydrofoils: The Future of Boats? 🚀

Hydrofoil technology is constantly evolving. New designs, materials, and applications are emerging all the time, pushing the boundaries of what’s possible on the water. Will hydrofoils become the standard for all boats in the future? Only time will tell. But one thing’s for sure – hydrofoils offer an exciting glimpse into the future of boating!

Want to stay ahead of the curve? Explore our Advanced Hydrofoiling Techniques and learn about the latest trends and innovations in the world of hydrofoils. We cover everything from cutting-edge designs to performance optimization techniques. Plus, our Hydrofoil Safety Tips section will help you enjoy this exhilarating technology responsibly.

Hydrofoils are more than just a cool boating gadget – they’re a game-changer in terms of speed, efficiency, and stability. By lifting your boat’s hull out of the water, they reduce drag and improve performance in ways that were previously unimaginable.

But just like any marine technology, hydrofoils have their pros and cons.

✅ Positives: They offer increased speed, improved fuel economy, a smoother ride, and better visibility for enhanced safety.

❌ Negatives: Installation can be a challenge for some boat owners, and choosing the right hydrofoil for your boat requires careful research and considerations.

It’s impossible to definitively say that hydrofoils are ‘good’ or ‘bad’ for every boat. The answer really depends on your individual needs and priorities.

If you’re looking to enhance your boating experience with faster speeds, smoother rides, and improved fuel efficiency, then hydrofoils are definitely worth considering! Just make sure you do your homework, choose the right model for your vessel, and install it correctly.

And if you’re ever feeling unsure about the whole hydrofoil thing, don’t hesitate to reach out to our team at Hydrofoiling™! We’re happy to answer any questions you have and help you make an informed decision.

👉 Shop Hydrofoil Brands:

Learn More about Hydrofoils:

• Book: Hydrofoils: A History and Guide to High-Speed Watercraft by Joseph N. Newman

Are hydrofoils good or bad for boats?

The answer isn’t black and white..

Hydrofoils can offer significant benefits: increasing speed, improving fuel efficiency, and providing a smoother ride. However, they also require careful consideration of factors like boat type, size, and intended use.

It’s essential to weigh these factors and decide if the benefits outweigh potential drawbacks. Our team at Hydrofoiling™ is always here to help you evaluate the pros and cons and make an informed decision.

Read more about “🚀 Hydrofoil Boats for Sale: Dive into the Future of Boating …”

Why are hydrofoils not used anymore?

That’s a misconception.

Hydrofoils are still very much in use! While they may not be as ubiquitous as other boating technology, they’ve experienced a resurgence in recent years due to advancements in design and materials.

Hydrofoils are now more efficient, user-friendly, and affordable than ever before. Their use is expanding rapidly, particularly in recreational and commercial boating.

Read more about “What is a Hydrofoil? The Ultimate Guide to Flying Over Water … 🏄‍♀️”

At what speed do hydrofoils work?

There isn’t a single speed where hydrofoils magically activate..

Hydrofoils start generating lift as soon as your boat is moving through the water. However, the amount of lift increases with speed, making it more noticeable at higher speeds.

The exact speed at which a hydrofoil provides optimal lift depends on factors like boat type, size, and hydrofoil design.

Read more about “The 5 Largest Hydrofoil Boats Ever Built: A Journey Through Maritime Giants … 🌊”

Will a hydrofoil make my boat faster?

Potentially yes, but it’s not magic.

Hydrofoils can increase your boat’s speed by reducing drag. How much faster you go depends on various factors like your boat’s hull design, engine power, and the type of hydrofoil installed.

However, it’s important to understand that hydrofoils are not a guaranteed performance boost for every boat. A proper assessment of your boat’s needs and the right hydrofoil can make a big difference.

Read more about “Hydrofoil Race Boat: Taking Speed to New Heights! … 🚀”

Review Team

The Popular Brands Review Team is a collective of seasoned professionals boasting an extensive and varied portfolio in the field of product evaluation. Composed of experts with specialties across a myriad of industries, the team’s collective experience spans across numerous decades, allowing them a unique depth and breadth of understanding when it comes to reviewing different brands and products.

Leaders in their respective fields, the team's expertise ranges from technology and electronics to fashion, luxury goods, outdoor and sports equipment, and even food and beverages. Their years of dedication and acute understanding of their sectors have given them an uncanny ability to discern the most subtle nuances of product design, functionality, and overall quality.

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MAIN FUNCTIONAL REQUIREMENT:   Lift the boat’s hull outside the water.

DESIGN PARAMETER:   Hydrofoil (It is a foil or wing under water used to lift the boat’s hull until it is totally outside the water.)

GEOMETRY/STRUCTURE:

EXPLANATION OF HOW IT WORKS/ IS USED:

1. At low speeds the hull (body of ship) sits in the water and the hydrofoils are totally submerged in the water.

2. As the boat’s speed increases, the hydrofoils create lift.

3. At a certain speed, the lift produced by the hydrofoils equals the sum of of the boat and cargo weights. Therefore the hull comes out of the water.

4. Instead of having an increase in drag with increasing speed because the hull is lifted out of the water (contrary to what happens in traditional boats due to pressure drag), the hydrofoils provide a more efficient way of cruising. Decreasing the drag contributes to the better use of the power needed for the movement of the boat.

DOMINANT PHYSICS:

How is the lift produced - Fluid Dynamics.

For the purpose of this project two explanations will be presented in a general and basic way. These theories are the application of Bernoulli’s Equation and Euler’s Equation for Streamline Curvature Effect.

Bernoulli’s Equation:  Po = P 1 + � r v 1 � + r gy 1 = P 2 + � r v 2 � + r gy 2

  This equation applies to flows along a stream line which can be modeled as : inviscid, incompressible, steady, irrotational and for which the body forces are conservative. Also the difference on the height of the foil (the distance from the bottom section to the upper one) is small enough so that the difference r gy 2 - r gy 1 is negligible compared to the difference of the rest of the terms. What is left is that the pressure plus one half the density times the velocity squared equals a constant (the stagnation pressure) . As the speed along these streamlines increases ,the pressure drops (this will become important shortly) .   The fluid that moves over the upper surface of the foil moves faster than the fluid on the bottom. This is due in part to visous effects which lead to formation of vertices at the end of the foil . In order to conserve angular momentum caused by the counter-clockwise rotation of the vortices, there has to be an equal but opposite momentum exchange to the vortex at the trailing edge of the foil. This leads to circulation of the fluid around the foil. The vector summation of the velocities results on a higher speed on the top surface and a lower speed on the bottom surface. Applying this to Bernoulli’s it is observed that, as the foil cuts through fluid, the change in velocity produces the pressure drop needed for the lift. As it is presented in the diagram, the resulting or net force (force= (pressure)(area)) is upward.

This explanation can be enriched with the Principle of Conservation of Momentum. (Momentum = (mass)(velocity)) If the velocity of a particle with an initial momentum is increased, then there is a reactant momentum equal in magnitude and opposite in direction to the difference of the momentums. (See diagram). (Mi = Mf + D M) Euler’s Equation: d(p+ r gy)/dn = r v�/R

Here again, the term referring to the height is assumed negligible compared to the other terms in the equation. This equation says that as you go further from the center of the radius of curvature of a streamline, the pressure on the streamlines increases. The upper surface of the foil is closer to the center of curvature of the streamlines , therefore there will be a lower pressure than the ambient pressure above the foil. The difference between the pressure on the top surface and the ambient pressure at the bottom surface will produce a net pressure that will cause the lift.(See diagram.)

Angle of Attack:

As it has been presented, lift comes from the dynamics of the fluid in the area surrounding the foil. But the lift can be optimized by positioning the hydrofoil at an angle (relative to the incoming fluid flow) called the angle of attack (See diagram). The goal is to optimize the lift to drag ratio. This ratio depends on the shape of the foil, which in this case is considered to be a thin foil. With a small angle of attack, the lift increases rapidly while the drag increases at a small rate. After an angle of ~ 10� the lift increases slowly until ~ 15� where it reaches a maximum.  After ~15� stall can set in. When the angle of attack is 3� to 4� the ratio of lift:drag is at it’s maximum. So the foil is more efficient at those angles (3�and 4�) with lift to drag ratios of ~ 20 to 25:1

LIMITING PHYSICS:

At first, people can think that stalling is likely to be a problem in hydrofoils as it is in airfoils, but surprisingly it is not. A steep angle of attack is not needed in the design of the hydrofoil. On the contrary, small angles of attack are used on hydrofoils to optimize the lift to drag ratio as explained before.

What is a primary concern is the design of the foil, the struts/supports, and their positioning. All these features have to be taken in consideration.  So the features are designed to produce a minimum speed that will lift the boat of certain weight and keep it foilborne.

One problem that a hydrofoil craft can experience is the height of the waves being greater than the struts. Also, if the craft is traveling faster than the waves, the foils could break to the surface and outside of the water, resulting in a loss of lift and a negative angle of attack when the foil dives into the next wave, making the craft crash into the sea. Engineers have designed hydrofoils to minimize these limitations and better the ship’s performance.

PLOTS/GRAPHS/TABLES:

None Submitted

SOME HYDROFOILS AND THEIR USE:

Hydrofoils have become very popular. They are used in various kind of sea traveling, from military use to watersports. The high speed, smooth cruise and better turns delivered by hydrofoils have been used in military ships. Sailing has also adopted the hydrofoils to gain more speed. They enable new inventions that can satisfy people’s desire to challenge danger , like the sky ski. It is a water ski with a hydrofoil attached which permits people to fly above the water surface. Every day more hydrofoils are used, and in the future, they may be the dominate method of sea traveling.

REFERENCES/MORE INFORMATION:

See also on this site: Airfoil , Sailboats

Alexander, Alan, James Grogono, and Donald Nigg; Hydrofoil Sailing . Juanita Kalerghi: London, 1972.

Bertin, John and Michael Smith; Aerodynamics for Engineers, Third Ediotion . Prentice Hall: New Jersey, 1998.

Hook, Cristopher and A.C. Kermode; Hydrofoils . Pitman Paperbags: London, 1967.

The International Hydrofoil Society’s Web Page: http://www.erols.com/foiler/index.html

It’s a Boat. It’s a Plane. It’s a Hydrofoil Boat: What Is It, How It Works, & Why Buy One! 

Table of Contents

Last Updated on June 5, 2024 by Boatsetter Team

We’ve created this helpful guide to introduce new and experienced boaters to the facts and features of hydrofoil boats. We’ll delve into the practical aspects and explore the advantages and considerations they bring. Whether you’re drawn to the efficiency of the design or the promise of smoother rides, hydrofoil boats might be just the subtle yet impactful change you’re looking for in your boating ventures. Post summary: 

• What are hydrofoil boats & the works 
• Why choose a hydrofoil boat 
• What to consider before buying 

Rent. List. Share—Only at Boatsetter  

What are hydrofoil boats & the works 

A hydrofoil boat is a watercraft equipped with wing-like structures mounted beneath the hull . The hydrofoils generate lift as the boat accelerates, causing the hull to rise above the water’s surface. 

Decreasing the hull’s contact area with the water helps to reduce hydrodynamic drag and wave resistance and increases fuel efficiency. Vessels can achieve higher speeds for longer distances, making hydrofoil boats ideal for applications like ferry services and long-distance travel. 

The concept of the hydrofoil boat emerged in the early twentieth century. Today, this innovation offers a thrilling option for boaters seeking a unique, efficient, and more environmentally friendly boating experience. Pro tip: On Boatsetter , you can browse through 20,000 different makes & models of boats! 

Why choose a hydrofoil boat

Three words: Speed, stability, and maneuverability!

1. Speed  

The lift generated by hydrofoils allows these vessels to glide effortlessly, offering a thrilling experience for adrenaline-seeking boaters. Speed comes with improved fuel efficiency, which makes hydrofoil boats an eco-friendly option as well. 

2. Stability  

Whether you’re facing calm waters or challenging sea conditions, lifting above the water surface minimizes the impact of waves on hydrofoil boats. This provides a smoother ride and enhanced stability, which makes for a more comfortable and enjoyable voyage. 

3. Maneuverability  

Hydrofoil boats excel in maneuverability, offering a dynamic and agile experience on the water. Lifting enables quick and precise movements, making hydrofoil boats a preferred choice for boaters who appreciate responsive navigation.  

What to consider when buying a hydrofoil boat

Complex design = Complex maintenance

The intricate design of hydrofoil boats, including the hydrofoils themselves and control systems, demands careful maintenance and technical expertise . Boaters should be prepared for higher maintenance costs and the need for specialized knowledge to keep the vessel in premium condition. 

Weather sensitivity

While hydrofoil boats perform admirably in various water conditions, they can be sensitive to extreme weather, especially strong winds. The hulls of traditional vessels remain fully submerged in water, which means they face more resistance on the water during strong winds. Hydrofoil boats are lifted out of the water, which means strong winds pose more of a threat to the boat’s stability and control. So, when you set sail in a hydrofoil boat you’ll want to be sure to carefully consider the weather conditions.  

Initial cost investment

The advanced technology, specialized materials, and intricate design that contribute to hydrofoil boats’ uniqueness also add to their price tag. Hydrofoil boats often have a higher initial cost compared to traditional vessels, so you should be sure to weigh the upfront investment against the long-term benefits. Pro tip: Trying to figure out budgeting to buy a boat? Read How to Rent Out Your Boat? (How Much Can You Actually Make?)  

Ready to try hydrofoil boating?

Hydrofoil boats offer an exhilarating experience for boaters seeking speed, efficiency, and stability on the water. Whether you’re looking for a quick thrill or want a more fuel-efficient option for your long-distance trips, we recommend giving hydrofoil boats a chance. 

Boatsetter boat rentals provide the perfect solution for those eager to try hydrofoil boating without committing to ownership. Seize the opportunity to experience the excitement firsthand and ensure your next adventure is not just a boat ride, but a hydrofoil-powered journey.

For more information, click here ! 

About us 

Boatsetter is the go-to app for boat rentals and on-water experiences. Whatever the adventure, we’ve got a boat for that—Set sail , start the party , go yachting , make your trophy catch , and hone your watersports skills! Download the Boatsetter app ( App Store | Google Play ). Make sure to follow @boatsetter on Instagram, and tag us in all your boat day pictures for the chance to be featured.  

Boatsetter empowers people to explore with confidence by showing them a world of possibility on the water. Rent  a boat,  list  your boat, or become a  Boatsetter captain  today.

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Hydrofoils: Boats That Fly

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Hydrofoils make everything from water skis to sailboats to giant ferries faster (much faster). But how the heck do they work?

Oracle Team USA's AC50 "flying" at nearly 50 mph. (Photo: Ricardo Pinto)

Ever wonder why a sleek, powerful recreational boat is not even as fast as a typical economy car? It has to do with friction. An economy car needs a little over 100 horsepower to speed by at 100 mph, but pushing a boat through the water that fast takes several hundred horsepower. The reason is that water is almost 800 times denser than air.

Imagine standing on your dock in a 10-knot wind — it's not hard to do. Now imagine being in a river trying to stand up to a 10-knot current. The water is so much denser that no matter how strong you are, you'd be swept away. A boat hull has to push through all that dense water while a car can slip through the air much easier.

Planing boats are able to go faster than displacement boats because they lift part of their hull out of the water as they race over their bow wave, but there's still a lot of friction from the water on the rest of the hull. If you could get the hull all the way out of the water, you'd eliminate that friction, and the boat could go faster with the same amount of power.

The Science

Most of us have a pretty good understanding of how an airplane flies. As air flows over and under the wings (also called airfoils), it creates lift. Once an airplane is going fast enough, the lift that the wings create allow it to rise above the earth.

If you were to mount a wing or two (called hydrofoils) under a boat, all that dense water can be put to good use by pushing the boat's hull out of the water. Then friction only acts on the small foils, not on the whole hull, which is why a 130-foot hydrofoiling sailboat can "fly" at over 50 knots. Powerboats have added friction from the propulsion system that has to remain in the water, but even then, large hydrofoiling ferries can exceed 45 knots.

Speed is not the only advantage that hydrofoils give boats. Because the hull is out of the water, all the energy from waves that would normally pound against the boat pass harmlessly underneath it, creating an eerily smooth ride. Even so, hydrofoiling is typically best in somewhat protected waters.

Don't look for hydrofoils on your next runabout anytime soon because they're much more difficult to engineer and typically triple the cost of a boat. The good news is that there are other ways to 'foil that are affordable — see "Experience Hydrofoiling For Yourself" at below.

Experience Hydrofoiling For Yourself

Hydrofoil kiteboards.

If you've even seen a kiteboard zooming in a strong breeze, you know they're plenty fast. Add a hydrofoil, and suddenly you add a new dimension. These boards take lots of skill and practice to master, but the ride is said to be much smoother and even faster than a conventional kiteboard. Cost starts at around $1,000.

Hydrofoil Waterskis

These single-ski hydrofoils are really a sit-on-ski, and once you've mastered the technique, the foils will lift you up and you'll be "flying." Unlike conventional skis, these aren't designed for speed, and 18 mph is where they typically "liftoff' and suggested top speed is about 25 mph. It's also important not to ski in shallow water due to the depth of the foils. Cost is typically $1,500 and up.

Hydrofoil Windsurfers

Not content to take a surfboard and add a sail, windsurfers developed foils that allow the board to "levitate." The biggest advantage is the smoothness of the ride — a real benefit because these rigs usually sail in very strong winds with plenty of chop. Cost is about $2,500 to get started.

Hydrofoiling Small Sailboats

You don't have to spend millions on a boat like the America's Cup racers if you want to hydrofoil. The Waszp costs about $10,000, though even for dinghy racers, there's a learning curve to get these boats on their foils, with speeds up to 27 mph.

Note that most companies suggest wearing a helmet when using foiling products because of the speeds achievable and the hard, sharp foils these devices have.

Foiling The Competition

America's Cup boats are often what people think of when they hear the word "hydrofoil." Hal Youngren, an aeronautical engineer and one of the designers for the 2013 and 2017 America's Cup racers, says the difference in speed that foils make is impressive. The fastest nonfoiling catamarans in previous races could barely reach 35 knots, while the 2017 foiling cats hit 50 knots. Youngren says that these 50-foot cats are able to lift their hulls completely out of the water using only about three-quarters of a square meter of foil area (about the size of a medium-sized TV). Below about 15 knots, he says, the boats sail much like a nonfoiling boat with hulls in the water, but once over that speed, the boats start to "fly" and their speed dramatically increases.

The America's Cup Class AC75 Boat Concept Revealed

An exciting new era in America's Cup racing was unveiled in November 2017 as the concept for the AC75, the class of boat to be sailed in the 36th America's Cup is released illustrating a bold and modern vision for high performance fully foiling monohull racing yachts.

The America's Cup AC75 Boat Concept Revealed

The Emirates Team New Zealand and Luna Rossa design teams spent the previous four months evaluating a wide range of monohull concepts. Their goals have been to design a class that will be challenging and demanding to sail, rewarding the top level of skill for the crews; this concept could become the future of racing and even cruising monohulls beyond the America's Cup.

The AC75 combines extremely high-performance sailing and great match racing with the safety of a boat that can right itself in the event of a capsize. The groundbreaking concept is achieved through the use of twin canting T-foils, ballasted to provide righting-moment when sailing, and roll stability at low speed.

An underlying principle has been to provide affordable and sustainable technology "trickle down" to other sailing classes and yachts. While recent America's Cup multihulls have benefitted from the power and control of rigid wing sails, there has been no transfer of this technology to the rigs of other sailing classes. In tandem with the innovations of the foiling system, Emirates Team New Zealand and Luna Rossa are investigating a number of possible innovations for the AC75's rig, with the requirement that the rig need not be craned in and out each day. This research work is ongoing as different concepts are evaluated, and details will be released with the AC75 Class Rule before March 31, 2018.

The America's Cup is a match race and creating a class that will provide challenging match racing has been the goal from the start. The AC75 will foil-tack and foil-gybe with only small maneuvering losses, and given the speed and the ease at which the boats can turn the classic pre-starts of the America's Cup are set to make an exciting comeback. Sail handling will also become important, with cross-overs to code zero sails in light wind conditions.

A huge number of ideas have been considered in the quest to define a class that will be extremely exciting to sail and provide great match racing, but the final decision was an easy one: the concept being announced was a clear winner, and both teams are eager to be introducing the AC75 for the 36th America's Cup in 2021. — AmericasCup.com

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Charles Fort

Contributing Editor, BoatUS Magazine

Charles Fort is BoatUS Magazine's West Coast Editor. He often writes local news items for BoatUS Magazine's Waypoints column and contributes to Reports, in-depth tech features in every issue written to help readers avoid accidental damage to their boats. He is a member of the National Association of Marine Surveyors, he's on ABYC tech committees, and has a 100-ton U.S. Coast Guard license. He lives in California.

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Sail GP: how do supercharged racing yachts go so fast? An engineer explains

Head of Engineering, Warsash School of Maritime Science and Engineering, Solent University

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Jonathan Ridley does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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Sailing used to be considered as a rather sedate pastime. But in the past few years, the world of yacht racing has been revolutionised by the arrival of hydrofoil-supported catamarans, known as “foilers”. These vessels, more akin to high-performance aircraft than yachts, combine the laws of aerodynamics and hydrodynamics to create vessels capable of speeds of up to 50 knots, which is far faster than the wind propelling them.

An F50 catamaran preparing for the Sail GP series recently even broke this barrier, reaching an incredible speed of 50.22 knots (57.8mph) purely powered by the wind. This was achieved in a wind of just 19.3 knots (22.2mph). F50s are 15-metre-long, 8.8-metre-wide hydrofoil catamarans propelled by rigid sails and capable of such astounding speeds that Sail GP has been called the “ Formula One of sailing ”. How are these yachts able to go so fast? The answer lies in some simple fluid dynamics.

As a vessel’s hull moves through the water, there are two primary physical mechanisms that create drag and slow the vessel down. To build a faster boat you have to find ways to overcome the drag force.

The first mechanism is friction. As the water flows past the hull, a microscopic layer of water is effectively attached to the hull and is pulled along with the yacht. A second layer of water then attaches to the first layer, and the sliding or shearing between them creates friction.

On the outside of this is a third layer, which slides over the inner layers creating more friction, and so on. Together, these layers are known as the boundary layer – and it’s the shearing of the boundary layer’s molecules against each other that creates frictional drag.

A yacht also makes waves as it pushes the water around and under the hull from the bow (front) to the stern (back) of the boat. The waves form two distinctive patterns around the yacht (one at each end), known as Kelvin Wave patterns.

These waves, which move at the same speed as the yacht, are very energetic. This creates drag on the boat known as the wave-making drag, which is responsible for around 90% of the total drag. As the yacht accelerates to faster speeds (close to the “hull speed”, explained later), these waves get higher and longer.

These two effects combine to produce a phenomenon known as “ hull speed ”, which is the fastest the boat can travel – and in conventional single-hull yachts it is very slow. A single-hull yacht of the same size as the F50 has a hull speed of around 12 mph.

However, it’s possible to reduce both the frictional and wave-making drag and overcome this hull-speed limit by building a yacht with hydrofoils . Hydrofoils are small, underwater wings. These act in the same way as an aircraft wing, creating a lift force which acts against gravity, lifting our yacht upwards so that the hull is clear of the water.

While an aircraft’s wings are very large, the high density of water compared to air means that we only need very small hydrofoils to produce a lot of the important lift force. A hydrofoil just the size of three A3 sheets of paper, when moving at just 10 mph, can produce enough lift to pick up a large person.

This significantly reduces the surface area and the volume of the boat that is underwater, which cuts the frictional drag and the wave-making drag, respectively. The combined effect is a reduction in the overall drag to a fraction of its original amount, so that the yacht is capable of sailing much faster than it could without hydrofoils.

The other innovation that helps boost the speed of racing yachts is the use of rigid sails . The power available from traditional sails to drive the boat forward is relatively small, limited by the fact that the sail’s forces have to act in equilibrium with a range of other forces, and that fabric sails do not make an ideal shape for creating power. Rigid sails, which are very similar in design to an aircraft wing, form a much more efficient shape than traditional sails, effectively giving the yacht a larger engine and more power.

As the yacht accelerates from the driving force of these sails, it experiences what is known as “ apparent wind ”. Imagine a completely calm day, with no wind. As you walk, you experience a breeze in your face at the same speed that you are walking. If there was a wind blowing too, you would feel a mixture of the real (or “true” wind) and the breeze you have generated.

The two together form the apparent wind, which can be faster than the true wind. If there is enough true wind combined with this apparent wind, then significant force and power can be generated from the sail to propel the yacht, so it can easily sail faster than the wind speed itself.

The combined effect of reducing the drag and increasing the driving power results in a yacht that is far faster than those of even a few years ago. But all of this would not be possible without one further advance: materials. In order to be able to “fly”, the yacht must have a low mass, and the hydrofoil itself must be very strong. To achieve the required mass, strength and rigidity using traditional boat-building materials such as wood or aluminium would be very difficult.

This is where modern advanced composite materials such as carbon fibre come in. Production techniques optimising weight, rigidity and strength allow the production of structures that are strong and light enough to produce incredible yachts like the F50.

The engineers who design these high-performance boats (known as naval architects ) are always looking to use new materials and science to get an optimum design. In theory, the F50 should be able to go even faster.

• Engineering
• Aerodynamics

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