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Discover the Thrill of Hydrofoil Catamarans: 10 Must-Know Facts for 2024! 🚤

• October 17, 2024
• Hydrofoil Basics

Have you ever dreamed of gliding effortlessly above the water, feeling the wind rush past you as you harness the power of the elements? Welcome to the exhilarating world of hydrofoil catamarans ! These innovative vessels are revolutionizing sailing, allowing you to experience speeds and stability like never before. Imagine soaring across the waves, your hull lifted by cutting-edge foils, leaving traditional sailing boats in your wake.

In this comprehensive guide, we’ll dive into everything you need to know about hydrofoil catamarans, from the best models for beginners to expert tips for mastering the art of foiling. Did you know that some hydrofoil catamarans can reach speeds of up to 40 knots ? That’s faster than many sports cars! Buckle up as we explore the fascinating features, benefits, and techniques that make hydrofoil sailing one of the most thrilling water sports today.

Key Takeaways

• Hydrofoil catamarans use wing-like foils to lift the hull out of the water, reducing drag and increasing speed.
• Models like the iFLY15 and UFO are perfect for beginners, offering user-friendly designs and excellent performance.
• Foiling can be mastered with practice, and it’s suitable for sailors of all ages.
• Regular maintenance is crucial to keep your hydrofoil catamaran in top condition.
• Hydrofoil catamarans can achieve impressive speeds, often exceeding 30 knots in optimal conditions.

Ready to take the plunge? 👉 Shop Hydrofoil Catamarans like the iFLY15 here or explore the UFO here and start your adventure today! 🌊✨

Table of Contents

Quick tips and facts about hydrofoil catamarans.

• The Evolution of Hydrofoil Catamarans: A Historical Perspective
• What Makes Hydrofoil Catamarans Unique?
• Top 10 Hydrofoil Catamarans You Need to Know

How to Choose the Right Hydrofoil Catamaran for You

Setting up your hydrofoil catamaran: a step-by-step guide, mastering the art of foiling: tips and techniques, hydrofoil catamarans for all ages: fun for everyone, managing your hydrofoil catamaran: maintenance and care, foiling at all points of sail: unlocking performance, frequently asked questions about hydrofoil catamarans, sign up for exclusive deals on hydrofoil gear.

• Recommended Links for Hydrofoil Enthusiasts
• FAQ: Your Hydrofoil Catamaran Questions Answered
• Reference Links for Further Reading

Hydrofoil catamarans are a type of sailboat that uses wing-like foils to lift the hull out of the water, reducing drag and increasing speed. Here are some quick tips and facts about hydrofoil catamarans:

• What is a hydrofoil catamaran? A hydrofoil catamaran is a type of sailboat that uses wing-like foils to lift the hull out of the water, reducing drag and increasing speed. 1
• How do hydrofoil catamarans work? Hydrofoil catamarans use the principle of hydrofoiling, where the wing-like foils create lift and reduce drag, allowing the boat to reach high speeds. 2
• What are the benefits of hydrofoil catamarans? Hydrofoil catamarans offer several benefits, including increased speed, reduced drag, and improved stability. 3
• What are some popular types of hydrofoil catamarans? Some popular types of hydrofoil catamarans include the GC32, iFLY15, and UFO. 4
• How fast can hydrofoil catamarans go? Hydrofoil catamarans can reach speeds of up to 40 knots (74 km/h) or more, depending on the design and conditions. 5

Top 5 Hydrofoil Catamarans for Beginners

If you’re new to hydrofoil catamarans, here are five models that are perfect for beginners:

When choosing a hydrofoil catamaran, consider the following factors:

• Size: Consider the length and beam of the boat, as well as the weight and draft.
• Design: Look for a design that suits your needs, such as a beginner-friendly model or a high-performance model.
• Materials: Consider the materials used in the construction of the boat, such as carbon fiber or aluminum.
• Price: Hydrofoil catamarans can range in price from a few thousand dollars to tens of thousands of dollars.

Setting up your hydrofoil catamaran can be a bit tricky, but with these steps, you’ll be sailing in no time:

• Assemble the boat: Follow the manufacturer’s instructions to assemble the boat.
• Attach the foils: Attach the foils to the hull of the boat, making sure they are securely fastened.
• Adjust the rake: Adjust the rake of the foils to optimize performance.
• Tune the sail: Tune the sail to optimize performance and stability.
• Launch the boat: Launch the boat and start sailing!

Foiling can be a bit tricky, but with these tips and techniques, you’ll be foiling like a pro in no time:

• Start slow: Start with slow speeds and gradually increase as you gain confidence.
• Keep the boat level: Keep the boat level and stable to maintain optimal performance.
• Practice, practice, practice: Practice foiling regularly to improve your skills.

Hydrofoil catamarans are not just for experienced sailors; they can be enjoyed by people of all ages and skill levels. Here are some ways to make hydrofoil catamarans fun for everyone:

• Take a lesson: Take a lesson from a certified instructor to learn the basics of foiling.
• Start with a beginner-friendly model: Start with a beginner-friendly model, such as the iFLY15 or UFO.
• Practice with a friend: Practice with a friend or family member to make it more fun and social.
• Join a sailing club: Join a sailing club or community to meet other sailors and learn new skills.

To keep your hydrofoil catamaran in top condition, follow these maintenance and care tips:

• Regularly inspect the boat: Regularly inspect the boat for damage or wear and tear.
• Clean the boat: Clean the boat regularly to prevent corrosion and damage.
• Store the boat properly: Store the boat properly to prevent damage and wear and tear.
• Follow the manufacturer’s instructions: Follow the manufacturer’s instructions for maintenance and care.

Foiling at all points of sail can be a bit tricky, but with these tips and techniques, you’ll be able to unlock optimal performance:

• Practice foiling upwind: Practice foiling upwind to develop your skills and confidence.

Here are some frequently asked questions about hydrofoil catamarans:

• What is a hydrofoil catamaran? A hydrofoil catamaran is a type of sailboat that uses wing-like foils to lift the hull out of the water, reducing drag and increasing speed.
• How do hydrofoil catamarans work? Hydrofoil catamarans use the principle of hydrofoiling, where the wing-like foils create lift and reduce drag, allowing the boat to reach high speeds.
• What are the benefits of hydrofoil catamarans? Hydrofoil catamarans offer several benefits, including increased speed, reduced drag, and improved stability.

Sign up for our newsletter to receive exclusive deals on hydrofoil gear and stay up-to-date on the latest news and trends in the world of hydrofoil catamarans.

👉 CHECK PRICE on:

• iFLY15: Amazon | iFLY15 Official Website
• UFO: Amazon | UFO Official Website
• GC32: Amazon | GC32 Official Website

In summary, hydrofoil catamarans are an exhilarating way to experience sailing, combining speed, stability, and the thrill of flying above the water. Models like the iFLY15 and UFO stand out for their user-friendly designs and performance capabilities.

• Speed and Performance: Hydrofoil catamarans can reach impressive speeds, often exceeding 30 knots, making them a thrilling choice for adrenaline seekers.
• Stability: The dual-hull design provides excellent stability, especially in choppy waters.
• Accessibility: Many models are designed for beginners, allowing new sailors to experience foiling with relative ease.
• Cost: Hydrofoil catamarans can be a significant investment, with prices varying widely.
• Learning Curve: While many models are beginner-friendly, mastering the art of foiling still requires practice and patience.
• Maintenance: Regular upkeep is necessary to keep these high-performance machines in top condition.

Overall, we confidently recommend hydrofoil catamarans for anyone looking to elevate their sailing experience. Whether you’re a seasoned sailor or just starting, there’s a model out there that can meet your needs and provide endless fun on the water. 🌊✨

Recommended Links

👉 Shop Hydrofoil Catamarans:

Books on Hydrofoiling:

• The Complete Guide to Hydrofoiling
• Hydrofoil Sailing: The Future of Water Sports

How fast do hydrofoil catamarans go?

Hydrofoil catamarans can reach speeds of up to 40 knots (74 km/h) or more, depending on the design and conditions. For instance, the GC32 has been known to achieve speeds exceeding 30 knots in optimal conditions, showcasing the incredible performance potential of these vessels.

Read more about “Hydrofoil Race Boats: 7 Reasons Why They’re the Future of Water Sports 🚀”

Why did the Navy stop using hydrofoils?

The Navy phased out hydrofoils primarily due to cost and maintenance issues . While hydrofoils offered speed advantages, they required extensive upkeep and were expensive to operate compared to conventional vessels. Additionally, advancements in other naval technologies made traditional ships more efficient and versatile.

Read more about “What Happened to the Hydrofoil? Unveiling 10 Surprising Facts … 🚀”

What is a foil-assisted catamaran?

A foil-assisted catamaran is a type of sailing vessel that utilizes hydrofoils to enhance performance. Unlike fully foiling catamarans, which lift completely out of the water, foil-assisted models may only partially lift, providing a balance between stability and speed. This design allows for easier handling and better performance in various wind conditions.

Read more about “Discover the Thrilling World of Hydrofoil Power Catamarans: 10 Must-Know Facts for 2024! 🚀”

Are hydrofoils worth it?

Absolutely! Hydrofoils can significantly enhance your sailing experience by providing faster speeds, reduced drag , and a unique thrill of flying above the water. While they may require a higher initial investment and some practice to master, the enjoyment and performance benefits often outweigh these challenges. If you’re passionate about sailing and looking for an exciting new challenge, hydrofoils are definitely worth considering!

Read more about “Discover the 10 Best Hydrofoil Passenger Ferries for 2024 🚤”

What are the best conditions for hydrofoiling?

The best conditions for hydrofoiling typically include steady winds of 8 knots or more and relatively calm water. These conditions allow for optimal lift and performance, making it easier to achieve and maintain flight. However, many modern hydrofoil designs, like the UFO , can handle a range of conditions, making them versatile for various sailing environments.

Read more about “Unlocking the Secrets of Hydrofoil Physics: 12 Fascinating Insights for 2024! 🌊”

Can beginners use hydrofoil catamarans?

Yes! Many hydrofoil catamarans are designed with beginners in mind. Models like the iFLY15 and UFO offer user-friendly features that make it easier for new sailors to learn the ropes. With proper instruction and practice, beginners can quickly get the hang of foiling and enjoy the thrill of sailing.

Read more about “Is a Hydrofoil a Catamaran? 10 Must-Know Insights for 2024! 🌊”

Reference Links

• Sailing Hydrofoil – Wikipedia
• Fulcrum Speedworks UFO Hydrofoil Boat
• iFLY15 Hydrofoil Catamaran
• Sailing World on Hydrofoil Catamarans
• Yachting World on Hydrofoil Catamarans

These resources provide further insights into the world of hydrofoil catamarans and their exciting potential! 🌊🚤

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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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iFLY15 – Technical SPECS

Length 4.63 m, 15 ft..

A Foiling Catamaran for 1-2 person(s) does not need to be any longer than this. The ancient rule that says you need length to achieve speed does not apply, as hulls do not touch the water at most times.

Width 2.50 m.

This width provides plenty of righting moment, still being road legal ato be transported in horizontal position without disassembly.

7.5 m mast / 11.2 sqm mainsail

7.5 m mast with 11.2 sqm deck-sweeper mainsail. – 8.5 m mast on iFLY RAZZOR Pro with bigger rig

Draft: 95 cm

Weight: 90 kg.

90 kg ready to sail. A very light boat, providing nonetheless excellent stability for everyday suitability.

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A great number of innovations all over the catamaran and the perfect match of all components allow controlled high-speed foiling experience. iFLY15 is full of innovations, e.g. in hull design, hydrofoils, rudders, automatic flight control system, two-layer wing trampoline, high performance rig…

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LATEST DEVELOPMENT OF “DECK SWEEPING” MAINSAIL WORLD PREMIERE: THE ROLLABLE HERU WING RIG : WORLD PREMIERE: LIGHT WIND FORESAIL «CodeF». ALLOWS UPWIND FOILING (as well as other courses/points) ALREADY IN EXTREMELY LIGHT BREEZE. Know More >>>

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The foils are controlled independently, dynamically and precisely on both sides by the flySafe® foil control system . This enables high performance sailing through stable flight. The unique foil control system of IFLY15 is a 7 years proven system developed by CEC Catamarans.        Know More >>>

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MDT FOIL CONTROL – iFLY rake control The sophisticated main foil differential is an active flight assistance – The Rake is adjustable while sailing. Advanced Rake Control is for the experienced, performance-oriented Catamaran sailors / pro sailors and is a feature on the iFLY RAZZOR Pro.      Know More >>>

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In the hand of the experienced sailor, iFLY15 is a high-performance racing machine. STABILITY IS NOT CONTRADICTORY TO HIGH PERFORMANCE OR SPORTINESS , on the contrary, it is a prerequisite for safe reaching and maintaining constant high speeds. Stable flight allows the sailor to concentrate on the course, on the wind, as well as on opponents and strategy – rather than permanently getting distracted by working on the foiling balance.

EARLY TAKE OFF IN WINDS AS LOW AS 2Bft. / 6 KNOTS , by combining the innovative “KickOff” foil control with a trampoline that provides boost and with the latest generation of rig and foils.

BOAT SPEEDS FAR BEYOND DOUBLE WIND SPEED CAN BE ACHIEVED . Enjoy high speed foiling with top speeds far beyond 25 knots – in ideal conditions up to 30 knots.

CONTROLLED FOILING EVEN IN THE UPPER WIND RANGE BEYOND 22KNOTS OF WIND SPEED – supported by the new FlySafe® Automatic Foil System.

FOILING PLEASURE AND PERFORMANCE ALSO IN CHOPPY WATERS

FREEDOM ! FLYING SOLO OR OPTIONAL WITH CREW . You have the choice. No manhunt for crew. But still enjoy the opportunity of taking a friend or family to fly with you. Up to 140kg of crew weight. (To keep the boat and especially the mast light, we specified the iFLY15 components intentionally not for double trapeze.)

NO HOISTING AND LOWERING OF DAGGERBOARDS while sailing. (Only for beaching or in shallow waters.)

FREEDOM TO SWITCH BETWEEN FLYING MODE OR SAILING AS A CONVENTIONAL CATAMARAN (with at least the leeward hull touching the water). Within seconds iFLY15 can be switched to Non-Flight mode, even while sailing. In that mode, iFLY15 will not take off, but the foils will still create lift and give an extra agile sailing behavior, which is on the same time very stable as rudder Foils will avoid pitch poling. Non-Flight mode is providing additional security in extreme high wind speeds. It is also useful for less experienced sailors or in all situations, where taking off is undesirable (e.g. in the harbor or while towing…).

EASY TO LEARN FLYING BY AVERAGE SKILLED AND TRAINED SAILORS

EASY BEACHING AND SLIPPING , as simple as with any conventional beach catamaran by using a standard catamaran beach trolley. Foils remain flat under the keel, with the daggerboard lifted as on a conventional catamaran.

SIMPLE TO DISASSEMBLE PLATFORM . Width of 2.50m is also road legal in most countries for horizontal transport without disassembly.

DAGGERBOARDS CAN BE PLUGGED IN FROM ABOVE and Foils securely anchored from below with one central screw.

FAST SET-UP OF THE iFLY15 FROM ROAD TRAILER TO SAILING . Simple rigging the mast, no genacker boom, no foresail, no spi.

SILENT AND CALM PLANING ABOVE THE WAVES . Flight height of up to 90cm, avoiding even high waves below.

EASY TO FOIL THE JIBE (without landing). Stable maneuvers are made easier by the fact that the four T-Foils always remain in the water.

« INTERNATIONAL FORMULA 15 FOIL » Class Association. The new development class for FOILING, SINGLE HANDED on MULTIHULLS. Multi manufacturer class in the tradition of a Formula18, A-Class or international Moth. Enables large regatta fields and evolution of the boats, following the technical progress (which is especially essential in the case in Foiling). Strict regulations to avoid uncontrolled exaggerated development.

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Facts About Power Cat Foils: Where They Can be Applied

Article by engineer andre moltschaniwsky of lomocean design courtesy of pacific powerboat magazine ..

With the most recent edition of the America’s Cup bringing foils to the limelight, it’s fair to say that most people with even a minimal interest in boats has a pretty good understanding of what ‘foils’ are and what ‘foiling’ is. 

This was illustrated graphically day after (painful) day last September as our screens were filled by the fantastic sight of two 72’ (21.95 m) winged America’s Cup sailing cats blasting around San Francisco Bay on hydro-foils at speeds that a few power boaters can relate to, but probably not too many yachties.

The word "foil" actually has a number of meanings and I was delighted to hear America’s Cup TV commentator and sailing legend Chris Dickson deadpan the expression “foiled by the fickle finger of fate” as race 13 was abandoned when the 40-minute time limit was reached, depriving Emirates Team New Zealand of the America’s Cup by a matter of only a few minutes. I had always heard a slightly modified, but less publishable version of the epithet, but being foiled in a competition that relies so heavily on a different kind of foil to achieve sheer, outright speed does have a certain symmetry to it.

Are Foils Viable?

So we know that foils can be used to make boats “fly” above the water, but in technical terms, what is a “foil?” In nautical design, a foil is what most people would call a “wing” — and is the technical term for a lifting body that generates force on one side due to the flow of a fluid past that body. The fluid can be gas or liquid — air or water — and its density, the speed with which it flows over the foil, the shape of the foil and the angle of attack (the angle at which the fluid flow meets the foil) all dictate how much lifting force it can generate — and how much drag is produced. 

Even a flat plate can be a lifting body although it needs to be at an angle to the air or water flow to generate lift; more complex foils are shaped such that air or water has to flow faster over one side than the other. Although fluid-dynamics experts probably frown at the following explanation, the velocity difference causes a higher pressure on one side of the foil and a significant lower pressure on the other — generating a net lifting force. 

This principle is put to good use in myriad applications from aircraft and propellers, to turbines and rudders. If fluid is flowing and we place a foil in it, useful forces from the energy associated with that flow are generated.

The towering AC72 wing sail is a collection of air-foil elements that generates lift and thus a propelling force as the wind flows over it. The hydro foils are wings that move through the water due to the driving force generated by the wing sail and in turn, generate hydro dynamic lift, picking up the boat mostly out of the water to reduce the drag associated with moving the hulls through the water.

Why Put a Hydrofoil on a Boat? 

Whether we are dragging a displacement or a planing hull through the water, there is a great deal of resistance associated with the combination of skin friction (wetted surface area) and wave-making drag. On displacement monohulls, wave-making drag tends to dominate because the hull is essentially always supported by buoyant forces rather than by dynamic lift, so pretty much the same amount of hull remains in the water throughout the speed range as it does when the boat is stationary. 

Displacement monohulls tend to be slow, limited to how fast they can go as a function of their ‘hull speed’  — usually defined (in knots) by the square root of the waterline length (in feet) multiplied by a constant — usually between 1.3 and 1.5. Thus, a displacement hull with a waterline length of 30’ (9.14 m) can be expected to top out at around 7.5 knots. You can make a displacement hull move faster than hull speed but you will need to generate some dynamic lift to reduce drag caused by wave-making and wetted area, so often a fast sailing yacht hull will be light and will have a flat its aft sections to promote lift.

Reducing Drag

Conventional fast powerboats generally use the planing hull form that most of us are familiar with. This is characterized by flat bottom shell surfaces bounded by down angled and sharp cornered chines — often with flat keel planks and strakes to add lift and control spray.

Designers use varying deadrise angle to reduce slamming, particularly on smaller planing hulls. There are some great photos on the internet of upside down tables (ie a planing surface with zero deadrise angle) with an outboard motor clamped to one end that look to be planing beautifully.

These flat plane hull shapes are intended to promote lifting forces as the speed of the boat increases, although rather than generating lift due to low pressure on an upper surface, it can only create lift by deflecting oncoming water downwards.  For every action there is an equal and opposite reaction, so by deflecting the water flow downwards, a reaction force is generated that pushes the boat upwards.

Removing hull area from the water reduces drag or resistance — and that helps the boat increase its speed. Making boats go fast is about adding power and reducing drag, so getting as much boat out of the “sticky” water as possible is desirable. Of course you still need something in the water to push the boat along and steer it — otherwise you become an airplane — but raceboats running at high speeds often have only a small portion of the hull, plus the drive skeg and/or propeller in the water. When their angle of attack becomes too great, they can turn — briefly — into an airplane.

History of Foils

If you consider that the first boats were launched by builders thousands of years ago, then the advent of hydro foils on boats is fairly recent. That said, in the years that the Wright brothers and Richard Pearse were experimenting with air foils in their attempts to fly, Italian Enrico Forlanini and Briton John Thorneycroft were both successfully doing the same with hydrofoils.

By late 1919, Alexander Graham Bell (of telephone fame) had set a world water speed record of just under 71 mph in the twin 350-hp powered, foil borne HD4.  So hydro foils have actually been with us for quite some time and seen action in a number of different applications.  Spectacular though the AC72s may have been while flying around San Francisco bay — and, while putting foils on an America’s Cup yacht might be new and radical, plenty of power and sail boats, big and small have used them before.

For example, in the 90s and early 2000s, legendary French sailors Alain Thébault and Eric Tabarly designed, built and sailed the 59’ (18 m) foil borne trimaran, Hydroptere , into the record books, achieving nearly 53 knots under sail in 2008, breaking the speed record over 500 m at the same speed in 2009 and briefly touched 56 knots before crashing. This is one sailboat, however, that might just leave an AC72 in its wake.

At the other end of the scale, the International Moth is a small sailing dinghy that has embraced hydrofoils in recent years, achieving speeds around 30 knots flying on impossibly thin wands and creating interest that has seen hydrofoils fitted to Lasers and Hobie 16s. Given the recent exposure with the America’s Cup, it is entirely possible that we will see some foiling 27’11” (8.5 m) class catamarans breaking records in future Coastal Classic yacht races, providing Cat 3 race safety requirements don’t get in the way.

Foiling in Powerboats

The military were early adopters of hydrofoil technology in powerboats and Canada worked on an experimental smoke laying hydrofoil during World War II. Between the early 1950s and early 1990s, the United States, Soviet and Italian Navies all developed hydrofoils for torpedo-boat, missile-boat and patrol applications, some of which remain in active service today.

Youtube is a treasure trove of footage of these boats and there is a great old documentary online about the U.S. development of Navy hydrofoils. It’s fascinating to watch a large Navy ship climbing out of the water in stately fashion and flying over the waves, before settling off the foils and back into the water in a dignified matter. There is also footage of smaller hydrofoils in heavy seas and although they at times glide serenely over the waves, it gets wet quickly when the hull briefly touches down in the face of an oncoming swell.

Passenger-craft hydrofoil development was also strong during this post-war period with the Soviets being particularly prolific, building large numbers of foil-borne ferries — chiefly for long-distance operation on inland waterways. Aircraft manufacturer Boeing also dabbled with hydrofoils, looking to take its expertise in production manufacturing of aircraft into the passenger ferry market with the Boeing 929 Jetfoil.

Typically, the US and Soviet approaches differed. The Americans favored full submerged foils that required complex control systems while the Soviets used a more robust, simplistic surface-piercing foil system that automatically regulates altitude, pitch and roll without fancy electronics and moveable control surfaces. Even today, fast hydrofoils operate for thousands of miles along inland water ways in the former Soviet territories, sometimes offering the only viable fast passenger transport service.

In the post-war years, Germany was prohibited from building fast boats, so a German engineer named Hanns Von Schertal — who worked on hydrofoil design before and during World War II — set up Swiss company Supramar, which was one of the first passenger ferry hydrofoil designers.

Built by Rodriquez, the Supramar PT20 Manu Wai  foiling ferry was delivered into service between Waiheke Island and Auckland in 1964 where it operated for nearly 10 years. Later, Manu Wai saw intermittent service as a charter vessel between layups — and a misadventure with a mud bank that saw the foils badly damaged — before shipping across the Tasman to Sydney, where she resides today, still in working condition.

Many early monohull hydrofoils remain in service today; ride qualities in rough seas can be superb and fuel efficiency can be excellent, so hydrofoils remain a common sight in places like Hong Kong. However they are technically complex, expensive to build, vulnerable to damage and expensive to maintain. They also have complex systems for propulsion and to retract the foils so the vessel can berth and traverse shallow water.

An associate of mine was involved in the early 1990s with the construction of a foil borne catamaran ferry in Sweden. The boat was delivered to Indonesia, where it operated successfully and efficiently until one of the custom-built water jet intake ducts located in a foil strut was hit by a floating log, putting the ferry out of action for three months while a hellishly expensive replacement part was constructed and shipped from Sweden. In the meantime, the operator went broke because its chief source of revenue was no longer operable.

The Development of the Assist Foil

For reasons such as this, aging hydrofoil fleets have yielded in the last few decades to simpler, less costly catamarans. And that in turn has led to development of a more subtle, less visible, but nonetheless effective the assist foil.

Developed by Professor Gunter Hoppe and his team at Stellenbosch University, South Africa in the 1970s, the “Hysucat” or Hydro Foil Supported Catamaran employs an assist foil that is intended to partially foil support the boat.  Rather than lifting all of the hulls clear of the water — necessitating expensive drivelines — Hoppe’s foil spans between the two catamaran hull forms and is located close to or above the keel line of the two demi-hulls, thus reducing vulnerability to grounding or impact with floating objects. This system tends to use a main foil located at or just forward of the longitudinal center of gravity and is often locked at a fixed angle.  

On more complicated installations, the angle of attack can be adjusted to vary the lift and drag offered by the foil. A much smaller trim foil (or foils) is then located near the stern of the catamaran and again, this/these can be set up at a fixed angle or can be adjustable to vary the trim angle of the boat and the angle of attack of a fixed main foil. 

Generally this system is designed to carry approximately half the displacement of the vessel at maximum speed. The driveline remains immersed, so conventional propulsion can be used, keeping cost down and generally significant improvements in fuel burn can be achieved for a given service speed by fitting a foil to a fast catamaran — a worthwhile saving for a ferry operator. Because the dynamic lift from the foil raises the catamaran higher in the water than it might normally operate, slamming on the tunnel roof can be reduced, offering notable improvements in ride quality.

This Hysucat system was patented by Stellenbosch University — although not globally — and the patent has since expired, so assist foils have been adopted around the world on catamarans.

How Relevant is all This to Recreational Powerboats?

The key benefits of partial or complete foil support are sea kindliness and fuel efficiency so both are of interest to owners of 32’10” to 78’9” (10 m to 24 m) motor boat. Generally this is why we have either specified or retro-fitted assist foils on a number of catamarans we have been involved with in the past.

Retro-fitting foils is a great way to gain an understanding of the benefits that can be gained because fuel burn data gained during sea trials pre and post fitting of the foil clearly demonstrates the effect.  Our experience has shown that assist foils can offer significant improvements — up to 18% reduction in fuel burn at cruise in some instances and increases in speed from 30 knots without foils to 38 knots. For the relatively modest cost involved, there probably aren’t any other comparable mechanisms that can achieve such a gain, although you do need to be doing reasonably big mileage before the fuel savings justify the investment.

There is some potential to fit assist foils to planing monohull pleasureboats and even to fully foil support them, just as has been achieved with ferries and military craft. There is some great footage of a 24’ (7.32 m) Bayliner owned by ex-Boeing engineer Harry Larsen, who designed and installed the foils — and importantly, the systems required to keep the boat at constant attitude and to control roll, yaw and pitch. Larsen’s original system used a simple mechanical system involving a ski that skims the surface of the water and is connected to the forward foil pitch controller to maintain ride height. This system is commonly used on the foiling Moths mentioned earlier. The later system uses electronic control systems and hydraulics to alter foil pitch.

Why Hasn’t the World Embraced Hydrofoils?

Plenty of people are interested in Larsen’s flying Bayliner — there are nearly 1 million views on Youtube — but he has never had enough inquiry about the foil system to make production viable for retrofit and as he wryly notes on his website no-one ever asked him if would sell the boat.

Maybe pleasure boaters are just too conservative, or maybe the risks and downsides outweigh the positives. America’s Cup 2023 is bound to have renewed interest in foils and foiling, so a boom in foiling sail boats could well be on the cards.

The number of foil assisted catamarans on the market — at least the faster ones — is on the rise, probably because they are simple, robust, reliable and offer significant benefits for reasonable cost.  And that is the key, particularly when most of the world’s power pleasureboating happens in mono-hulls. If fully foiling monohulls aren’t practical or desirable, perhaps the next big thing in pleasure boating will be the assist foil for monohull powerboats? 

Article courtesy of Pacific Powerboat Magazine.