small foil sailboats

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Boat of the Year 2020 F101: Best Foiler

• By Dave Reed
• Updated: December 10, 2019

At A Glance

Price As Sailed: $24,750

Design Purpose: Learn to foil, advance skills

Crew List: One or two

Rob Andrews and his ­business partner Alan Hillman have been teaching foiling for a few years now, and one thing they’ve learned is we get better by sailing, not by swimming. Thus was the genesis of the F101, a craft with which they could teach the fundamentals of foiling—without the crash and burn. But it’s not just a learn-to-foil boat, either. It’s a platform with which new and experienced converts alike can take their ­foiling skill set to a higher level.

The key to mastering the F101, Andrews explains, is grasping righting moment. With the trimaran platform, you get plenty of it, as well as a stable boat that’s more forgiving than any other small foiler. “The trimaran configuration gives you righting moment direct from the foil in the middle hull,” he says, “and gives a measure of safety. It’s hard to capsize the boat.”

The judges learn as much when it comes time to sail the F101. In 15 knots and more, and a steep Chesapeake chop, Powlison is first to give it a go. He settles into the boat, gets his bearings, perches skittishly on the weather hull, sheets on the mainsail (no need to use the boat’s gennaker above 12 knots) and off he goes like a bat out of hell, popping up on the foils without even trying.

“The trick is getting used to the sensation of heeling to windward,” he says. “It takes a bit of trust. Once foiling, it’s quiet and fast, and I felt like I had to be really active on the mainsheet to keep it on the foils.”

That’s true of any foiler, but the beauty of the F101, the judges agree, is when you do lose it, it’s no big deal. The boat drops off its foils, the bows auger in and you get a face full of water; but just reset, bear away and try again.

“The hull shape picks up the buoyancy gently,” Stewart says, “which makes it depress smoothly and prevents it from pitchpoling. When I dumped it a few times I thought I was going in, but not a chance. You quickly realize there’s plenty of floatation there to save you. In flat water, with one day of training you’d get up to speed quickly.”

When teaching people to foil, Hillman starts with “skimming,” a ride height barely above the surface. As the sailor becomes more accustomed to how the boat behaves, there’s a simple line adjustment at the foil head: Dial it up one setting and increase your ride height.

As you’re sailing, the foil wand hanging behind the trailing edge effectively feels where the boat is riding relative to the water and actuates the main flap. In light winds, it gives you more lift, and the boat pops up on the foil. Get too high, and the wand drops down even ­further, forcing negative lift on the flap, which brings you back down to your desired height and prevents the foils from breaking the surface.

In terms of construction, the judges praise its carbon-and-epoxy build quality and the all-up weight of 180 pounds, which makes it easy to get to and from the water. With the F101 sitting on its dolly in the boat park, going sailing is as simple as pulling back the covers, hoisting the main and launching from a dock, beach or boat ramp with minimal fuss.

“What I like about it is that it’s one of those boats that you buy and don’t need to add anything to it,” Allen says. “There’s ­nothing to change out or upgrade.”

For simplicity, the boat is set up with adjustments that let you ratchet up the experience as you climb the learning curve. On the rudder foil, for example, there is a clear numbering system so that as you twist the tiller extension, you change the rudder rake. The baseline setting is zero, and it’s the same for the main foil. The only thing left is to balance the forces with the mainsheet.

“When I first got up on the foils, I was thinking to myself, ‘This is too easy; I should be working harder,’ ” Powlison says. “As they said, this boat solves a lot of the problems associated with other foiling dinghies. It’s a great high-performance boat that represents the next step in making foiling accessible to the public.”

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• Best Foiler
• Best Dinghy
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12 foiling boats for sailors of all levels

• April 15, 2022
• No Comments

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There’s no denying that the phenomenon of the moment, when it comes to having fun, is foiling boats (as Checco Bruni told us himself in this article). In the wake of the latest editions of the America’s Cup, flying boats, especially in the dinghy segment, have become increasingly widespread. On one or two hulls, with one or more foils, more or less easy to fly, single or crewed.

We have selected for you 12 flying boats with which to enter the world of foils or with which to try and perfect your skills. We also tell you how much they cost and the “difficulty of flight” (XXX: difficult; XX: medium; X: easy). The only common denominator is that they are great fun!

Birdyfish – 4,7 m – For foiling beginners

Flying difficulty:   X

The ideal boat for learning to sail foils, even for beginners. Very few trim adjustments for foils allow you to enjoy all the excitement and joy of flying. The crew will only have to deal with sail trimming. The appendages with a soft-angled L guarantee take-off from 10 knots of wind. The shape of the bow works well even in waves. Price: 16,980 euros.

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Flo1 – 4.25 m

Flying difficulty:  X

An interesting single to approach and perfect in the world of small foilers before moving on to more sophisticated craft. Produced by the Dutch company Aeronamics, it has a soft, almost C-shaped foil. There is no adjustment of the rake of the appendages but only its extension in the water, which makes the “trim” of these appendages easy and intuitive after just a few trips. Top speeds are around 20 knots. Price: 15,495 euros.

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NACRA F20 – 6,20 m – Like America’s Cup cats

Flying difficulty:  XXX

The Nacra yard, which specializes in open catamarans and produces the Nacra 17 Olympic class, has fitted its F 20 model with a “Flight Control System” to make it fly. The Nacra 20 FCS was designed by Pete Melvin and Gino Morelli, the authors of the 2013 America’s Cup rulebook, and its foils are reminiscent of those on the AC72 in San Francisco. A very physical boat and not for everyone. Price: 34,000 euro.

Foiling Dinghy – 3,86 m – Small and versatile

It weighs 30 kilos and can be foiled as early as seven knots of wind. The Foiling Dinghy is equipped with an inverted T rudder and a pair of curved foils that act as both lifting and straightening foils, with an automatic management system. The foils have a few simple adjustments depending on what you want to achieve (more flying or more straightening). Price: 15,500 euros including taxes.

Moth – 3,35 m – The foiling cult dinghy

The progenitor of the flying dinghies is still one of the most complete single foilers on the market today. Suitable mainly for advanced sailors who already have experience on foils, it has appendages that offer multiple setting options and the possibility of being changed according to wind strength. The international class is one of the most active and always organizes very crowded races. Cult product. Price: from 20,000 euros.

Peacoq 14 – 4.70 m – Like a flying Fireball

Flying difficulty:  XX

With a hull that is vaguely reminiscent of the old Fireballs with a “cut” bow, the Peacoq 14, an evolution of the Club version, is a dinghy that can be a compromise for both novice and experienced foil sailors. In fact, the dinghies can be operated in automatic trim, or more experienced sailors can adjust their angle for maximum performance. Price: quote on request.

Persico 69F – 6,9 m – The trendy boat

This concept boat is the brainchild of the Italian racing elite (Giorgio Benussi, Dede de Luca, “l’oriundo” Maciel Cicchetti) and was designed by Argentineans Wilson and Marquinez. Flying the 69F is not too difficult, although it does require a good physique and strength in the arms, especially for the mainsail trimmer and the foil adjuster. The racing circuit has now been launched with an attractive programme. Price: rented by the season.

Skeeta – 3,35 m – Easy for anyone

Ease first. The idea behind Skeeta is the same as that of many other small foilers: to make this type of wing easy and open to everyone. Skeeta is a single glider that flies on two self-regulating appendages, not particularly technical to fly but still very high performance, with the particular shape of the hull that distinguishes all Quant models. Price: 15,345 euros.

Stunt S9 – 4,16 m – The Italian Foiling cat

This is an all-Italian One Design catamaran that can be sailed as a single with just a mainsail or even a jib depending on the weather conditions. Like other catamarans, to improve stability in flight, it moves on four submerged appendages. Physically it requires a certain amount of athleticism, also because there is a trapeze, but with a little training it can be suitable for a wide audience. Price: 16,600 euros.

Ufo – 3,00 m – Flying with two hulls

This small catamaran is equipped with a sensor that self-adjusts the inclination of the single central foil, coupled to the T of the rudder. It can take off even in light winds thanks to the lightness of its construction. The cat is quite easy to sail, suitable even for sailors who do not have much experience with foils.

The official european dealer for Foiling UFO is  Sea-Change . Price:  8.980 euros + VAT

Waszp – 3,35 m – For the whole family

Very similar to the Moth, but with one big difference: the Waszp is a monotype, it is not made of carbon and the appendages being monotyped cannot be changed. For this reason it is less expensive than the Moth, even if it does perform somewhat less well. It is considered by many to be an ideal “family” boat because it is fun for both young and old. The foil adjustment system is managed by a sensor, but it is possible to set the appendages and modify some adjustments. Price: 12,200 euros.

Whisper – 5,40 m – Full performance

As light as the highest performing Cats, it features a one-piece, non-removable platform that provides great structural rigidity. Equipped with the four classic self-adjusting appendages, it is able to set sail in light breezes with a certain ease. It is a double, with trapeze, mainsail, jib and gennaker, fast even in light winds. Physically demanding. Price: 26,900 euros.

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11 Best Small Sailboat Brands: How to Choose Your Next Daysailer or Pocket Cruiser

12th oct 2023 by samantha wilson.

Sailing is a relaxing, invigorating pastime that allows you to harness wind and waves in a unique and historic way without requiring a 50-foot yacht to enjoy what’s special about the experience. In fact, small sailboats allow a delightful back-to-basics experience that often gets lost on larger, systems-heavy sailboats.

On a small sailboat you can connect with the sea, feeling the boat move beneath you. The boat is typically easy to rig, simple to sail, and can even be sailed solo. Small sailboats give you the freedom to trailer your or car-top your boat and go anywhere, and they’re perfect for learning the nuances of sailing. There are many excellent brands and models of small sailboat, each with their own appeal, and here we narrow down some of our favorite in the daysailer and pocket cruiser categories under 30 feet. 

Difference Between a Daysailer and a Pocket Cruiser

While there are many different types of sailboat on the market and there is no single definition of either a daysailer or a pocket cruiser, they are used in a particular way, as the names imply. The term daysailer covers a huge array of sailboats, smaller and sometimes larger, and is generally defined as any day boat used for local sailing, with a simple rig, and easy to get underway. A pocket cruiser typically offers a cabin and head, and adequate accommodations for an overnight stay and sometimes longer cruises. Having said that, there is a large overlap between the two in many instances, so the lines may become blurred. 

What Size is a Small Sailboat?

Small is a relative term of course, but in general—and for the purposes of this article—a small sailboat is one that could be sailed by a small crew, often with one or two people aboard. It will have a simple rig and be trailerable, and it might be either a daysailer or pocket-cruiser style vessel as above. Within those categories, there are many models and styles, but when it comes to length we consider a sailboat as small when it’s under 30 feet in overall length. 

The Best Sailboats Under 30 Feet

Pocket cruiser: Beneteau First 27.  The Beneteau First 27 is a modern example of a pocket cruiser, earning Cruising World ’s Boat of the Year award in the Pocket Cruiser category in 2022. With space for up to six people accommodated in a separated bow-cabin and open saloon, it offers families the chance to go farther, explore more, and cruise in comfort. There is a galley with freshwater and a head, adding to the interior home comforts. The sailboat itself is modern, fast, and stable, designed by Sam Manuard, and has been designed to be incredibly safe and almost unsinkable thanks to its three watertight chambers. The handling is also refreshingly intuitive, with a well-designed cockpit, simple deck controls, and double winches allowing it to be sailed solo, by two people, or a small crew. 

Photo credit: Beneteau

Daysailer: Alerion 28.  You’ll certainly turn heads cruising along in an Alerion 28, a daysailer whose forerunner by the same name was designed by Nathanael Herreshoff in 1912 and then updated with a modern underbody for fiberglass production by Carl Schumacher in the late 1980s. This pretty daysailer manages to combine a traditional silhouette and classic feel, with very modern engineering creating an excellent package. Over 470 of these sailboats were built and sold in the past 30 years, making it one of the most popular modern daysailers on the water. With a small cabin and saloon, complete with miniature galley area, it offers respite from the sun or wind and the option for a night aboard. The cockpit offers a beautiful sailing experience, with plenty of space for the whole family. 

Photo credit: Alerion Yachts

The Best Sailboats Under 25 Feet

Pocket cruiser: Cornish Crabber 24.  British manufacturer Cornish Crabber has been producing beautiful, traditional style small sailboats for decades, ensuring they honor their heritage both in the construction style and appearance of their boats. The Cornish Crabber 24 is the most iconic of their range and dates back to the 1980s. It offers a simple yet surprisingly spacious interior layout with cabin, galley, and head, and a good sized cockpit, as well as seating for up to six people. It’s the perfect family sailboat, with clever use of storage as well as just under 5000 pounds of displacement providing stability and easy tacking. Aesthetically the 24 is simply beautiful, with a traditional silhouette (combined with modern engineering), finished in hardwood trims. 

Photo credit: Cornish Crabber

Daysailer: Catalina 22 Capri.  Catalina sailboats need little introduction, and are one of the world’s best-known, most-respected brands building small sailboats. The Catalina 22 Capri (also available in a sport model) is a great example of what Catalina does so well. While we’ve classified it as a daysailer, it could easily cross into the pocket cruiser category, as it offers excellent sailing performance in almost all conditions as well as having a small cabin, galley, and head. Loved for its safety, stability, ease of handling and simple maintenance, it makes for a good first family boat for getting out onto the bay or lake. 

Photo credit: Catalina

The Best Sailboats Under 20 Feet

Pocket cruiser: CapeCutter 19.  This is another model that combines the beauty of the traditional silhouettes with modern-day advancements. The design originates from the classic gaff cutter work boats, but today offers excellent performance—in fact it’s one of the fastest small gaffers in the world. The interior is cleverly spacious, with four berths, two of which convert into a saloon, as well as a simple galley area. With quick rigging, it can be sailed solo, but is also able to accommodate small groups, making it a capable and hugely versatile pocket cruiser. 

Photo credit: Cape Cutter 19

Daysailer: Swallow Yachts’ BayRaider 20.  Classic looks with modern performance are combined in Swallow Yachts’ beautiful BayRaider 20. This is one of the most capable and safest daysailers we’ve seen, but also incredibly versatile thanks to the choices of ballast. Keep the ballast tank empty and it’s light and fast. Fill the tank up and you’ve got a stable and safe boat perfect for beginners and families. While it’s got an eye-catching traditional style, the engineering is modern, with a strong carbon mast and construction. While this is a true daysailer, you can use the optional spray hood and camping accessories to create an overnight adventure. 

Photo credit: Swallow Yachts

The Best Sailboats Under 15 Feet

Pocket Cruiser: NorseBoat 12.5.  Can we truly call the NorseBoat 12.5 a pocket cruiser? Yes we can! The sheer versatility of this excellent little sailboat has convinced us. These beautiful hand-crafted sailboats offer exceptional performance and are described by the manufacturer as ‘the Swiss Army Knives of sailboats’. The traditionally styled 12.5 can be sailed, rowed, and motored. It can be trailered, easily beached, and even used as a camp cruiser, allowing for overnight adventures. There is no end to the fun that can be had with this easy-to-sail and easy-to-handle boat, which makes it a dream to learn in. With positive flotation, lots of clever storage, and a full-size double berth for camp cruising, it really is the perfect mini pocket cruiser. 

Photo credit: NorseBoats

Daysailer: Original Beetle Cat Boat 12: All across the bays of the US east coast cat boats have long been part of the ocean landscape. Able to access shallow rocky coves yet also withstand the strong coastal winds, these traditional New England fishing boats have an iconic shape and gaff-rigged mainsails. Beetle Cat have been producing elegant wooden cat boats for over 100 years – in fact they’ve made and sold over 4,000 boats to date. Their 12 foot Cat Boat 12 is one of their finest models, offering lovely daysailing opportunities. It has a wide beam and centerboard that lifts up, allowing it to access shallow waters, as well as a forward mast and single sail gaff rig in keeping with the traditional cat boats. To sail one of these is to be part of the heritage of New England and Cape Cod, and to honor the ancient art of hand-made boat building. 

Beetle Cat official website

Photo credit: Beetle Cat

The Best Small Sailboats for Beginners

When it comes to learning to sail, it’s important to have a boat that is easy to handle. There’s no quicker way to put yourself or your family off sailing than to start off with a boat that is either too big or too complicated. When choosing your first boat we recommend the following characteristics:

• Small: The benefits of starting off with a small boat are many, as we’ve seen above. They’re easier to control as well as to moor, and they react more quickly to steering and sails. They can be trailered and launched easily, and the loads generated are much lower than on bigger, heavier boats.
• Easy to sail: You want a boat that is stable and forgiving of mistakes, doesn’t capsize easily, and isn’t too overpowered in a stronger breeze. Keep things simple and learn as you go.
• Simple sail configuration: Choosing a boat that can be rigged by one person in a few minutes, and easily sailed solo, makes it easier to take along inexperienced crews. With regards to the rig, all you need are a halyard to hoist the mainsail and a sheet to control the mainsail.
• Tiller steering: We recommend boats with tiller steering over wheel steering when starting out. The tiller allows you to get a real feel for the boat and how the rudder works as it moves through the water. 

For more information on choosing the best beginner sailboat check out our full guide. There are many popular brands of beginner boats including Sunfish, Laser, and Hunter Marlow. Some of our favorites include;

Hobie 16: The classic Hobie catamaran has been a well-loved beginner sailboat for years, and the Hobie 16 started life back in 1969. Since then they’ve made and sold over a staggering 100,000 of the 16s. It has twin fiberglass and foam hulls, a large trampoline, and a pull-up rudder so it can be sailed straight onto the beach. The basic package comes with an easy to handle main and jib with plenty of extras available too such as a spinnaker and trailer. The Hobie 16 promises a great learning experience and lots of fun in a very nifty and inexpensive package. 

Photo credit: Hobie

Paine 14: You’ll immediately fall in love with sailing when you step into a beautiful Paine 14. Made from seamless epoxy cold-molded wood, the P-14 is simply beautiful and offers the classic sailing experience with the design and innovation of a more modern hull and rig. Two people will be able to enjoy getting out on the water together and learning the ropes. The Paine 14 has a lead ballast keel that accounts for nearly half her weight, giving her the feel of a much larger boat, but is still trailerable and easy to manage offering the best of both worlds. 

Photo credit: Chuck Paine

High-Performance Small Sailboats

Small sailboats generally become high performers if they are light, have a lot of sail area, or they have more than one hull. More recently, some of have been designed with foiling surfaces, as well. For the purposes of this article, we’d like to close by pointing out one model that is super fast and has versatile pocket-cruising capabilities.

Corsair 880 trimaran : The Corsair 880 trimaran is the grandchild of the company’s F27, a model that launched the popularity of trailerable leisure trimarans about 40 years ago. The 880 has taken the model to new heights and exemplifies the incredible space benefits you can achieve in a 29-foot sailboat. We’re talking an aft cabin, room to sleep 5 people, an enclosed head, and standing headroom in the galley and main saloon. It brings many of the opportunities that a much larger yacht plus the ability to cruise in extremely shallow water. Whether you want to cruise to the Bahamas or enjoy a high-adrenaline race, the Corsair 880 offers incredible performance and unlimited adventures in a truly pocket size. 

Photo credit: Corsair

Written By: Samantha Wilson

Samantha Wilson has spent her entire life on and around boats, from tiny sailing dinghies all the way up to superyachts. She writes for many boating and yachting publications, top charter agencies, and some of the largest travel businesses in the industry, combining her knowledge and passion of boating, travel and writing to create topical, useful and engaging content.

More from: Samantha Wilson

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TF10 Foiling Trimaran

Ultra-modern, morrelli & melvin design, craftsmanship, wij bouwen uw nieuwe foiling boot, the tf10 trimaran: the foiling flying machine.

After the foiling revolution, the TF10 foiling trimaran is now the evolution of foiling sailing. With the TF10 foiling trimaran, sailing and foiling can be reached by any sailor. The TF10 is an 11 m long one-design foiling trimaran, designed by the famous yacht designers Morrelli & Melvin . The TF10 is built and sold by DNA Performance Sailing.

The TF10 is suitable for a crew of 4-5 persons and can handle a wide range of sailing conditions. The construction consists of pre-preg carbon fibers with a Nomex honeycomb core. This provides a lightweight, yet safe and robust construction. The foiling TF10 trimaran is the perfect foiling boat for both pleasure trips and sailing fast in races.

The transport of the TF10 is also revolutionary: when folded, it is easy to transport. We supply the TF10 with a specially designed road trailer, launching by boat ramp or crane are both possible.

Foils create sailing comfort

Thanks to the sophisticated design, every sailor feels comfortable on the TF10 foiling trimaran. Regardless of age, gender or muscle strength. And regardless of the speed, which can quickly reach up to 30 knots! Safety and comfort were the two main focuses of the design. This is reflected in a number of elements:

• The bow is designed to cut through the waves. This results in less hits on waves, which greatly increases sailing comfort.
• The carbon benches with back support provide a comfortable seat for crew and helmsman.
• The wishbone boom (half windsurfer boom) provides the decksweeper mainsail layout to perform at its best. An additional advantage is that in a manoeuvre the sail is now the lowest point and not the carbon boom.
• A ‘Semi-ridged’ carbon fibre trampoline cloth has been specially designed to make the boat’s construction torsional stiff. It makes it easier to walk on and block’s splashing water from the foils.
• The TF10’s foils and T-rudders minimize pitch and roll movements. The rake angle of all four foils is adjusted with electric actuators. This system improves comfort and safety during sailing and foiling.

TF10 hydrofoils

The TF10 foiling trimaran flies with a 4-point foil setup:

• The T-rudders with horizontal elevators generate lift and/or downforce.
• The so called Z-type daggerboard foils provide the necessary lift to be able to foil.
• The advantage of the 4-point-foil setup is that the crew does not have to pick up the daggerboards during manoeuvres. This significantly reduces the crew’s actions.
• In addition, we have electric actuators that change the position of the foils and rudders with a single push on the button.
• The design of the Z-foils has already been very successfully applied to other foiling multihulls, such as the A-cats and the Olympic Nacra 17.

Specifications

Length incl. bowsprit: 10.94 m Length waterline: 9.97 m Beam: 6.8 m Beam incl. benches: 7.65 m Beam (folded on trailer): 2.5 m Minimum draft: 0.4 m Maximum draft: 2.55 m Height center hull: 1.78 m Mast length: 16.1 m Displacement leightship: 1400 kg Displacement max. load: 1900 kg Outboard engine: 6pk, retractable Mainsail: North Sails 3Di 45 m2 Jib: North Sails 3Di 28 m2 Gennaker: (on furler) 71 m2 LED Navigation lights

Fast and pure one-design racing Easy shipping Created by owners for owners

See and feel the future of sailing. The TF10 foiling trimaran is here!

This special foiling trimaran was designed at the end of 2015. The idea was to make a foiling multihull that anybody can sail and foil with. A foiling boat equipped with the same technology as the boats at the America’s Cup.

The TF10 and its sailing class is the result of initiatives by a group of five sailing friends on the East Coast of America (Newport, RI). They have joined forces and created the TF10 sailing class.

The members of the TF10 Class Association have lot’s of experience in various one-design racing series. The goal is to create a racing series that is as exciting, honest and fun as the boat itself.

Morrelli & Melvin designed a trimaran to combine the specific characteristics of a trimaran with foiling. The trimaran’s center hull offers important advantages here: its buoyancy and pitch stability eliminate the risk of ‘nose diving’ or ‘pitch poling’. In the design briefing, wind range and sea state (short sea shipping) were important. The design of the TF10 is based on this.

For all information, competitions and the latest news, please visit the TF10 Class website: www.TF10class.com

It is possible to make a trial run with the TF10. We do this on the IJsselmeer, just a few kilometres from DNA’s shipyard. Here the sailing and foiling conditions are perfect: There is always wind and you can fully enjoy the beautiful surroundings. The IJsselmeer lies between the cities of Lelystad, Almere and Enkhuizen. The new island area “Markerwadden” can also be seen and possibly visited here. Mail us at [email protected]

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Home » Blog » Sail » Hydrofoil boats for the rest of us

Hydrofoil boats for the rest of us

By Author Fiona McGlynn

Posted on Last updated: August 18, 2023

Glide Free Foils Laser on foils. Photo credit: sailboats.co.uk ,

Watching foiling boats fly around the America’s Cup race course, is enough to quicken any sailor’s pulse. But unless you’ve got a spare few million kicking around, most hydrofoil boats are still very much out of the average boater’s budget . There are however a few ways to experience the magic of foiling without racing towards bankruptcy.

HOW DOES HYDROFOILING WORK?

Much in the same way that air flows over and under aircraft wings to create lift, water flowing around a hydrofoil lifts a boat’s hull out of the water . Once the greater part of the boat’s surface area is out of the water, friction is greatly reduced and the boat can “fly” at faster speeds .

How fast? The 2021 America’s Cup AC75s are expected to reach top speeds of 40 to 50 knots!

Like sails, foils are not a matter of “set it and forget it”, instead the foil-attitude must be adjusted to keep the boat in flight . On the 2017 America’s Cup boats these adjustments were made by the skipper/helmsman but powered (via a hydraulic system) by crew grinding winches (or in New Zealand’s case, pedal bikes ).

Because we don’t all have Jimmy Spithill ‘s magic touch, developing highly sophisticated flight control systems is key to bringing foiling into mainstream boating. Candela, a new 25-foot production e-foiling powerboat (and 2019 Best of Boats award winner) offers such a solution with foils that change position 100 times per second! Still, at ~$240,000 it’s well beyond most boating budgets. 

Fortunately, smaller foilers (dinghies and boards) don’t require high tech flight control systems and are far less expensive . Here are a few options for (more) affordable foiling:

HYDROFOIL DINGHIES

Laser foiling kits.

Clip a foil onto your Laser and fly over the surface of the water. Two Australian based companies, Foilsz and Glide Free Foils , offer Laser foiling kits. The Glide Free kit doesn’t require any permanent fixtures, so you can easily remove it (for those days when you’re in a displacement mode mood). They say that speeds of 18-25 knots are possible with their kit, which sells for just under $4,530 AUD (~$3,00 USD). 

UFO foiling multihull

For a few bucks more you can buy a foiling catamaran. The UFO was launched in 2017 and can fly at 15-20 knots. With a price tag of $7,000, it may be the most economical multihull foiler on the market.

Take a foiling course

Some clubs and community sailing programs are adding foilers to their fleets. For example Nantucket Community Sailing offers a 3-hour semi-private class for $100 per person . Or if you’re looking for a more exotic locale, the Provela Foiling Centre in Spain offers a range of foiling classes from beginner to advanced. Their two-day “Try Fly – Foiling” class costs 200 euros and their fleet includes Foiling Moths, White Formula Whispers, WASPZs, and F101s.

HYDROFOIL KITEBOARDS

It’s not like kiteboards are sluggish to begin with, but hydrofoil boards take the sport to a whole new level, delivering speeds of 40 miles an hour ! By using a foil to lift their boards out of the water, foiling kiteboard enthusiasts get an exceptionally quiet and smooth ride – so much so, that   kiteboard riders in Silicon Valley have been spotted taking calls on their cell phones. Set up costs start at around $1,000. Take a foil boarding course and buy protective gear, this extreme water sport is not for the faint of heart.

HYDROFOIL WINDSURF BOARDS

Foiling is taking off in the windsurfing world with world champions like Robby Naish and Atoine Albeau leading the charge. It has been confirmed that windfoiling will be a class at the 2024 Olympics in Paris . Set up costs start around $2,500. 

With foiling technology trickling down into the mainstream, you can expect to see more and more high speed foiling boats and boards on the water .  Is foiling the future? Let us know what you think in the comments below.

Fiona McGlynn is an award-winning boating writer who created Waterborne as a place to learn about living aboard and traveling the world by sailboat. She has written for boating magazines including BoatUS, SAIL, Cruising World, and Good Old Boat. She’s also a contributing editor at Good Old Boat and BoatUS Magazine. In 2017, Fiona and her husband completed a 3-year, 13,000-mile voyage from Vancouver to Mexico to Australia on their 35-foot sailboat.

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High-Performance Foils

Shaping better centerboards and rudders

From Issue   July 2020

W hile it’s generally accepted that the right sails and sail trim will determine how close you can sail to the apparent wind, a sailboat’s progress to windward also depends on the lift and drag generated by the centerboard and rudder. How much difference does proper foil shape make over a simple rounded leading edge and tapered trailing edge, anyway?  Foils operating in fluids, whether air or water, are a well-studied topic. C.A. Marchaj, in his book, Sailing Theory and Practice , discusses the theory and gives the results of actual tests of differences in foil planform (side view), cross-section shape, size, and aspect ratio (AR – length to width). Lacking other constraints, an ideal centerboard, daggerboard, or rudder blade should have a reasonably high AR (greater than 2) planform with a streamlined cross-section that has a parabolic leading edge and a thickness of somewhere near 10 percent of the chord width (the distance from leading edge to trailing edge). A thickness of 8 percent produces less drag but stalls sooner; 12 percent has a higher stall angle but produces more drag.

Exactly where the point of maximum thickness should be located is a matter of some debate. Marchaj suggests it should be at 50 percent of the chord width, halfway between the leading edge and trailing edge, but provides no data to back that up. Other sources suggest that the NACA (National Advisory Committee on Aeronautics) symmetric foil sections, originally developed during aircraft research, are actually a good fit for boat foils operating at low speeds in water. A NACA 0010 foil, for example, has a maximum thickness of 10 percent of the width of the foil, located at 30 percent from the leading edge.

Of course, there are many practical reasons why not all keels, centerboards, and rudders have high AR planforms, but the cross section for a foil of any planform should be streamlined. My personal experience of doing it wrong on one boat, and getting it right on another boat, has convinced me that the NACA sections and guidelines above provide good performance.

HORNPIPE, my first sail-and-oar boat, was an 18’ Kurylko Alaska with a standing-lug ketch rig, and sailed well enough to windward in flat water, but lost 10 to 15 degrees of pointing ability as soon as the water got choppy. I knew it wasn’t poor sail trim. Eventually I got looking at the daggerboard and analyzed it. It was only about 2.5 percent of the sail area and its thickness was only about 6 percent of the chord width, neither big enough or thick enough in my view, and in rough water it lost laminar flow and lift. When I designed my 18′ lug-yawl cruiser, FIRE-DRAKE, I gave it a thicker centerboard with a greater fraction of the sail area, about 4 percent. I also gave it a straight quarter chord line (think of the shape of the wing of a Spitfire aircraft) and a moderately high aspect ratio of about 3:1 for the planform area. To get the daggerboard foil shaped accurately and quickly I opted to have it cut on a computer numerical control (CNC) machine. All that was left for me to do was sand, seal and paint, and make an epoxy-lined hole for the pivot pin.

The results have been what I had hoped for. FIRE-DRAKE sails quite well to windward and maintains its performance in rough water. I sailed in the company of a similar boat—with the same length and beam, the same weight, and the same sail plan—along the south half of the Inside Passage, and that boat’s centerboard was shaped by eye. When sailing to windward, FIRE-DRAKE would consistently point higher and walk away in speed. My centerboard even let me continue sailing to windward when my partner gave up and took to the oars.

Although I had the daggerboard shaped with a CNC router, it is possible to shape a high aspect ratio, fully streamlined foil in the home shop. I’ll walk you through my second project, a kick-up rudder blade that I made at home to replace the original one I built for FIRE-DRAKE. I settled on a planform that is one-quarter of an ellipse with an elliptical leading edge and a straight trailing edge. (The shape would move the center of lateral resistance of the boat aft a few inches, and is intended to lighten the weather helm I’d experienced with the original rubber blade.) I drew the new blade with an aspect ratio of 2.5:1, with a length of 30″ (762 mm) and a maximum chord width of 12″ (305 mm), which would increase the lift and reduce the tip vortex drag.

To draw the planform shape of the quarter ellipse you can use an online graphing tool such as Desmos for a full ellipse. If you center the ellipse at zero, you can drag the two axes out until you get the aspect ratio you want. Since the graph has a grid in the background, you can then print out a screen capture of a quarter of the resulting ellipse and scale up the printed image to the actual dimensions required. If you are comfortable with computers, you can download and run Freeship (available for Windows only) which has a “keel and rudder wizard” that accurately generates several different planforms.

The new rudder blade for FIRE-DRAKE has a quarter-ellipse planform. The plywood’s glue lines show the contours that help with shaping the foil.

Obtaining the cross-section profile of a chord of a given width is best left to a computer. For any of the NACA foils, like the 0010 foil I mentioned above, Competition Composites Inc . (CCI) has a very simple and handy calculator . You need enter only the chord width and the maximum thickness and it will generate a table of X-Y coordinates that you can copy and print out. They’ll be your offsets for drawing a pattern for the foil cross-section. If you intend to sheathe your foil with ’glass and epoxy, for example, you can also enter the skin thickness and it will calculate the coordinates for the plywood core.

Now, here’s the tricky bit. If you have a rectangular foil planform, you only have one chord width and therefore one section profile for the entire length of the foil. However, if you have any other planform (e.g., half-ellipse, quarter-ellipse, trapezoidal, straight-chord-quarter-line, etc.), the thickness, which will be one-tenth of the chord width, changes along the length of the foil because the chord width changes.

I used the CCI calculator to generate profile coordinates for three different points along the length of the rudder blade: at the root, at about two-thirds of the way along and at about 90 percent of the way to the end. I chose those points because the chord width for my quarter ellipse planform doesn’t change much for the first half of its length, but it changes more quickly toward the tip. The idea is to shape the foil to these profiles at these points and then taper the foil evenly between them. You can lay out your foil plan directly on to the ply or you can use something thin, like doorskin, to make and fine-tune a template, which is what I did.

I made a blank for my rudder by gluing layers of marine ply with epoxy to the required 1″ thickness. I have found that the plywood, in spite of its cross-grain plies, has sufficient strength for the size of small-boat foils that I have built (though the cross-grain would weaken a long thin foil). Plywood does not warp and has the added advantage over solid wood in that the plies create a kind of contour map that give you graphic visual feedback as to the evenness of your surface once you start shaping the foil. You can make a foil with solid wood or even foam plus a ’glass-and-epoxy skin, but without the plywood laminates as guides, you would have to make more section profile templates to ensure a smooth and accurate shape.

Clamping a 4′ level to the flat part of the rudder blade provides a reference line to gauge how much wood to remove to achieve the foil’s taper.

The next step is to taper the thickness of the laminated foil blank along its full length. Knowing the required thickness at your chosen points, you can draw a pattern for the curve of the taper and half the thickness of the blade stock and measure how much wood you have to remove at each point. I clamped my 4′ aluminum I-beam level to the flat part of the rudder blade above the shaped part, and used a ruler to measure the depth I had to cut to. To remove the wood for this part of the project, I used my #4 Stanley plane. While I have a power hand planer, I didn’t trust myself with it to not take too much off too quickly.

The female half-section template for a given chord for a foil gets its shape from the X-Y coordinates generated by a foil calculator.

I made three female half-section profile templates, one for each of the three points noted above, by plotting out the generated X-Y coordinates on pieces of doorskin and carefully cutting them out. One thing to note is that the CCI calculator generates a profile that has a trailing edge of zero thickness. Obviously, this is not practical to build in wood, and a knife edge is not that critical anyway. I adjusted the trailing edges so that the finished edge would end up about 1/3″ (4mm) thick.

Applying the template to the foil in the works shows the high and low spots as the shaping continues.

Next, I used the profile templates to shape the foil at my three chosen points. I shaped the plywood with a Shinto rasp , regular rasps, and coarse sandpaper. It’s a process of taking some wood off, placing the template, and repeating until you get the section of wood shaped to the templates. Once that is done, I could go to work taking down the wood between the sections, using the ply layers as a guide. I used my block plane, Shinto rasp, and sandpaper for this task. I eyeballed a smooth transition around the tip from the leading edge to the trailing edge.

I sealed the surface of the shaped foil with a couple of coats of epoxy to provide a smooth, hard surface to accept a finish coat of marine epoxy enamel.

Alex Zimmerman is a semi-retired mechanical technologist and former executive. His first boat was an abandoned Chestnut canoe that he fixed up as a teenager and paddled on the waterways of eastern Manitoba and northwestern Ontario. He started his professional career as a maritime engineer in the Canadian Navy, and that triggered his interest in sailing. He didn’t get back into boatbuilding until he moved back to Vancouver Island in the ’90s, where he built a number of sea kayaks that he used to explore the coast. He built his first sail-and-oar boat in the early 2000s and completed his most recent one in 2016. He says he can stop building boats anytime. He is the author of the recently published book, Becoming Coastal .

For further reading on the pros and cons of the variables in foil design, Competition Composites (CCI) has a good discussion . For those of you who want to go into the math, Paul Zander has a good presentation from nearly 20 years ago, and also, for those inclined that way, an updated discussion with a lot more math.

You can share your tips and tricks of the trade with other Small Boats Magazine readers by sending us an email .

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Comments (17)

Is there someone who can craft a good rudder for my boat? I have not the time or the skills to do such. Have a 15′ Delaware Ducker. Love the boat but the rudder is (I think) a disaster. Hardly brings the boat around and doesn’t help much to windward. Flat plywood barn door out of 3/8″ ply with no shape other than outline that barely gets 2″ – 3″ into the water. If it could be a kick-up so much the better. I do a lot of shallow, sand-bottom sailing. Thank you for any help.

I know about the ducker and a foil shaped rudder will help a lot. Some of the modern ones built in glass and cold molded have been fitted with modern dinghy rudders and foil shaped daggerboards. They tack more like a dinghy than like my traditional one where I have to sail it around like a larger boat.

Most any small boat builder in your area should be able to build you a rudder. Lines for a kick up would be a nuisance. I don’t bother with them on a larger boat, just use a pivot bolt with tension. Means I have to shove it down.

You might want to look at the system that Mike Storer has developed for his goat island skiff, a straight foil, easier to shape.

Alex has done a great idea showing us how to work these out using hand tools. We used to do it in my dinghy sailing days by drawing a 30 % line. Make a bunch of parabola templates and hack away. For really long narrow boards before the days of carbon we used to use 5/4 stair tread fir.

Interesting article. When I built my Oughtred JII Yawl eighteen years ago, I did some research on appropriate foil profiles for the centerboard and rudder. It’s a long time ago now, so I don’t remember the exact profiles I chose, but I do believe I picked NACA 0010 for the CB. I picked another profile for the rudder, one that had a steeper stall angle, on the theory that with typical weather helm the rudder meets the flow at a steeper angle than the CB. I really don’t know how valid my theory is. I have no experimental evidence to back it up. Any thoughts?

Andrew, that seems to make sense although I haven’t seen any research to back that up.

Hi Andrew, I remember seeing your beautiful JII; but did not ask about the foils! I wonder how NACA 0010 compares with my approximate foil shape, inspired mainly by guesswork. Are these profiles available? By the way, I do not like plywood foils; CBs break. Friends near here lost their fine old rebuilt Wayfarer; were in danger themselves, when they capsized and the plywood board broke. Too near a rugged lee shore. A class racing boat, by a particular builder – all their plywood centerboards broke.

Iain, I don’t know what your standard foil shape looks like, but a NACA 0010 has a maximum thickness of 10% of the chord distance, occurring at 30% of the distance back from the leading edge. Marchaj believes that the maximum thickness should occur at about 50% of the distance back from the leading edge. Other designers agree, I think. If I understand him correctly, John Welsford uses a foil section that is closer to 50% distance, but I am not sure what thickness of foils he favors or what the exact foil shape is. You can see the shape, and all the requisite numbers for extracting an X-Y plot to reproduce them, for a whole bunch of different foil types, on the Airfoil Tools site. As for plywood foils, I understand your concern. Half the plies are oriented in the wrong direction and don’t provide much in the way of resisting sideways bending moments. However, it has been my experience that this is not a major concern if the foil is thick enough and not too long. The centerboard foil on my latest boat, for example, is ply, but is nearly 2″ (50 mm) at maximum thickness. It’s got over 1,000 nautical miles in four years under the keel by now, including a couple of practice capsizes, with no issues so far.

I don’t know what a standard Wayfarer foil looks like. Is it long and thin?

Very interesting article. I am just in the process of building a Lillistone Flint and have no experience building or knowledge of foil design and performance. I calculated the various ratios and percentages. The AR as per the plans is 2.43, so that looks good. The thickness however is only 4% of chord width. Area of the dagger board is 3.5% of sail area, so probably OK there too. Lillistone does state in the plans that the board can be made thicker if preferred so I think I may do that as 4% is a pretty big departure from the 8 – 10% of the chord width suggested. Any comments? The Flint was featured in this mag a few issues ago.

David, both my experience and authorities who design for a living and/or who have tested these things would suggest that 4% is rather too thin for good lift. I suspect that you might find it works reasonably well in dead flat water but you would lose lift and pointing ability as the water gets more turbulent. If it was me, and I hadn’t yet built the foil and its case, I’d go for one that was at least 10% and maybe even 12%. The additional thickness would also be more robust should you need to stand on it to flip the boat over if you capsize.

Thanks so much for taking the time to reply, Alex. I have decided to use some salvaged King William (King Billy here in Tasmania) pine that was salvaged. I thicknessed it to clean it up a bit and reckon I will eventually get 20 – 22 mm out of it. I plan to laminate 10 pieces into a 304mm board. Hopefully I will get a good result.

Hi David, It highly depends where you sail and how you sail. I have one older (1975) 420er dinghy for fun and local competitions with foiled board and rudder. But then I have 21″ German Jollenkreuzer veteran from 1952 which has both from 1/4″ steel plate, and it works fine. I sail that for pleasure on lakes. It would definitely be more performant (and point better) with both foiled, but I’m surprised how well it performs in its nearly ’70s (comparing to modern GRP boats with foiled boards).

For your job, I would probably stick to the plans. The rudder in this case is more important and can be somehow easily modified (foil). The centerboard I would keep the same, not only to conform the centerboard box (which would need to be sized), but also the overall design. Finally the most important here is what is your building and designing experience, because the worst thing is when something is incorrectly designed and then improperly built (the simple rounded plywood then may work better).

Anyway, I’m also thankful for this article. It reminds me my childhood when I built airplane models and used exactly the same methods used here to create the wings (in much smaller scale).

Thanks for your thoughts. I am going for a thicker foil and risk it (see reply to Alex above). I am well aware of risks in departing from designer’s work but I don’t think I will go far wrong.

Do SUP fins follow the rules for centerboards?

I’m not a SUP guy myself, but my understanding is that the fins are there to assist in tracking. That is, they don’t need to provide lift the way a sailboat keel/CB going to windward does. The thing you would be aiming for in the case of SUP fins is having sufficient lateral area to provide that tracking ability, and then having it streamlined to reduce drag. I would imagine that thinner would be better, although you’d still want a streamlined foil section, as that would produce less drag than a flat plate. The leading edge of a flat plate tends to separate the flow from the sides of the plate, even if that edge is rounded, and separation produces turbulence and drag.

For twenty years, beginning in the early 1970’s, I raced a Lido 14. The boat was pre-owned, and had its original solid wood foils which were in pretty bad shape, and I decided to build new foils. After reading Marchaj’s book, and the Lido 14 Class Rules, I designed a new centerboard and rudder. The NACA-0009 section most closely fit the required class measurements, and I used that profile. I did alter the leading edge of the rudder, making it more rounded, to allow for the fact that the rudder angle of attack is variable, and is more likely to stall.

In fleet racing, and sailing close hauled, the results were astounding, with the boat seeming to sail slightly sideways, relative to other boats. I also began to pay particular attention to the condition of the foil surfaces, as Marchaj writes that the drag on underwater foils is many times greater than the drag on the hull surface. One time we were sailing in an area of submerged trees, and my centerboard lightly brushed a tree branch. I then noticed that the centerboard ‘hummed’ on port tack. Later, when I examined to board, there was a barely visible scratch.

I very much enjoyed the article on high-performance foils in the July 2020 issue of the Small Boat Magazine .

For twenty years, beginning in the early 1970’s, I raced a Lido 14. The boat was pre-owned, and had its original solid wood foils which were in pretty bad shape, and I decided to build new foils. After reading Marchaj’s book, and the Lido 14 Class Rules, I designed a new centerboard, and rudder. The NACA-0009 section most closely fit the required class measurements, and I used that profile. I did alter the leading edge of the rudder, making it more rounded, to allow for the fact that the rudder angle of attack is variable, and is more likely to stall.

In fleet racing, and sailing close hauled, the results were astounding, with the boat seeming to sail slightly sideways to windward, relative to other boats. The boat didn’t seem to point higher, when close hauled, it just didn’t make as much lee way. More benefit on the port tack, a little less on starboard. I did set the centerboard jibe angle to the maximum allowed by class rules. In all honesty, I was probably the only one in the fleet that had read Marchaj. It still took me five years to win the fleet championship. I also began to pay particular attention to the condition of the foil surfaces, as Marchaj writes that the drag on underwater foils is many times greater than the drag on the hull surface. One time we were sailing in an area of submerged trees, and my centerboard lightly brushed a tree branch. I then noticed that the centerboard ‘hummed’ on port tack. Later, when I examined to board, there was a barely visible scratch.

I am a new subscriber to Small Boat Magazine , and look forward to each issue. Keep up the good work.

Was just about to make the centerboard for my Oughted Caledonia Yawl. So I was happy to see this article. But was then disappointed when I calculated my centerboard area to be only 1.9 percent of my total sail area. I briefly thought gee I will make it a little bigger…but then realized the centerboard trunk is already complete and limits that. I don’t plan on racing, so it is what it is.

Mark, I’d be really interested in your results once you launch the boat and do some trials. Theory is one thing, but nothing beats data from real-world results.

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Discover the Magic of Hydrofoil Sailboats

Last Updated by

Daniel Wade

December 11, 2023

‍ Key Takeaways

• Hydrofoil sailboats blend speed, stability, and innovation for a fun sailing experience.
• Their design lifts the hull above water, reducing drag and enabling high-speed travel.
• Advanced control mechanisms maintain stability in varying wind conditions.
• Sails and hulls are meticulously engineered for optimal aerodynamics and lift.
• Ongoing innovations in foil technology continue to propel hydrofoils to new heights.

‍ Based on their innovation and nature, the world of hydrofoil sailboats are magical, to say the least. But what exactly makes them so exceptional?

The magic of hydrofoil sailboats lies in their extraordinary speed. They can achieve remarkable speeds that were once thought impossible for sailboats. Their unrivaled stability and cutting-edge technology redefine sailing, offering a thrilling blend of innovation and performance.

Over the years, I've dedicated myself to mastering the intricacies of the yachting world, not just as an observer but as an active participant in the hydrofoil sailing community. My knowledge extends beyond the surface, encompassing the technical aspects of hydrofoil design and the thrill of high-speed sailing. As such, I’ll provide a comprehensive and engaging exploration of what sets hydrofoil sailboats apart, making them truly magical on the waters.

Table of contents

‍ Discover the Magic of Hydrofoil Sailboats

Hydrofoils saw their early development as a concept for enhancing speed and efficiency on the water. From Alexander Graham Bell's experiments to the application of foils on sailboats in the 1950s, the quest has always been for greater speed.

But it wasn't until Russell Long championed these designs with the CEC foiling catamaran and the development of the Hobie Trifoiler that hydrofoils began to carve a distinct niche in the sailing world.

This sailboat operates on a simple yet ingenious principle: as the speed increases, the foils submerged beneath the boat generate lift. This lift thrusts the boat's hull above the water, dramatically reducing drag.

It’s similar to how air flows around the wing of an airplane, only with water's denser environment offering a different dynamic. This revolutionary foiling system allows boats to glide over waves, offering an incredibly smooth ride.

The variety of hydrofoil sailboats is astounding, from the foiling catamarans that have revolutionized the America's Cup to the twin sail trimaran designs. The fastest production sailboat, the Hobie Trifoiler , showcases what hydrofoils are capable of.

Additionally, boats like the innovative Emirates Team New Zealand vessels continue to push the boundaries of technology in competitive sailing. Whether for recreational purposes or high-speed racing, the range of hydrofoil sailboats caters to different sailing experiences and preferences.

Now, let’s explore the various aspects of hydrofoil sailboats that make them truly magical.

The Thrills of Hydrofoil Sailing

When I first stepped onto a hydrofoil sailboat, I knew that sailing would never be the same for me. Harnessing the power of the wind to achieve remarkable speeds while hovering above the water was nothing short of revolutionary.

It's an adrenaline-infused blend of sailing, flying, and innovation that promises high performance and stability with a significant reduction in wetted areas.

The allure of hydrofoiling is not just about the speed; it's the sensation of flying over the waves, defying the conventions of traditional sailing. With each gust, my hydrofoil sailboat becomes a silent, swift car, slicing through the air rather than merely sailing on the water.

When sailing with hydrofoils, you get to experience the following benefits.

• High Speed: With hydrofoils, I've seen and achieved speeds I never thought possible on water.
• Less Wetted Area: As the hydrofoils lift the hull out of the water, drag is reduced, further contributing to the craft's efficiency and speed.
• Stability: Surprisingly, the flying sensation is accompanied by stability once airborne, making the ride smoother.

The America’s Cup Competitive Foiling

Over the years, I've witnessed first-hand how hydrofoil technology has radically altered the landscape of competitive sailing. The introduction of hydrofoils has not only redefined what we consider possible in the sail area but has also brought a fresh surge of excitement to the racing circuit.

The most illustrious event in sailing, the America's Cup , underwent a transformation with the embrace of hydrofoils. Emirates Team New Zealand, a frontrunner in hydrofoil innovation, redefined the America's Cup racing in 2017.

Alongside them, the US team and Luna Rossa played pivotal roles in reshaping the landscape of America's Cup racing.

With their AC50 class catamarans soaring above the waves at top speeds that defy traditional sailing limits, they clinched the title and shifted the focus of competitive racing toward technological prowess.

The spectacle of these vessels racing is not just about the crew's capabilities but equally a testament to engineering marvels.

Also, the advent of hydrofoils in racing has certainly led to a spike in performance metrics. Here's a concise table highlighting the before and after impact of hydrofoiling in competitive Sailing:

This table illustrates just how much the racing landscape has shifted; it's not only sailing anymore.

It’s similar to piloting a high-speed aircraft, with each crew member playing a crucial role in harnessing the raw power of the strong winds in harmony with state-of-the-art technology. Watch this video for a more detailed explanation of hydrofoil sailboats and their magical power.

Technical Aspects of Hydrofoil Sailboats

In diving into the technical aspects of hydrofoil sailboats, I'll give you an insight into the intricate designs that enable these marvels to glide above the water, as well as the cutting-edge foil technology propelling them.

The design of a hydrofoil sailboat revolves around its capability to elevate the hull above the water, reducing drag and enabling high wind-speed travel. Control mechanisms are central in maintaining stability, especially when the sailboat interacts with varying wind conditions or maneuvers through shallow waters.

The hull's length and overall design are calibrated for balancing aerodynamics with hydrodynamics. In designing sails and hulls for foiling, one must carefully balance the need for power with the propensity for lift.

The sails are tailored not only to harness the wind's energy effectively but also to match the unique mechanics of a vessel in flight. Meticulous engineering ensures that the sail configuration works in harmony with the foils to propel the sailboat forward swiftly.

Additionally, the foil technology, which is pivotal to modern hydrofoils, has undergone significant further development over the years . From the materials used to the manufacturing processes, every element incorporates the latest in technology to yield extreme performance.

Advancements have led to foils that can automatically adjust to sailing conditions and speed, which is instrumental for achieving and maintaining high speeds.

Currently, the future of hydrofoil technology seems bound for even further breakthroughs. Customization and refinement of foils for specific water conditions, such as the challenges posed by shallow water, are ongoing.

Each new iteration builds upon the last, consistently advancing the field and informing the next leap in hydrofoil sailing. This persistent innovation in foil and hull technology is a testament to the potential that lies ahead for hydrofoil sailboats.

Are Hydrofoil Sailboats the Right Options for You?

Hydrofoil sailboats offer a unique and thrilling sailing experience, but whether they are the right option depends on your preferences and goals. These high-performance vessels are known for their exceptional speed and stability, making them ideal for thrill-seekers and competitive sailors.

If you're passionate about cutting-edge technology and want to push the boundaries of traditional sailing, hydrofoil sailboats could be a perfect fit.

However, they may require a learning curve for beginners and are typically more expensive than traditional sailboats.

Consider your skill level, budget, and desire for speed and innovation when deciding if hydrofoil sailboats align with your sailing aspirations.

The Future of Hydrofoil Sailboats and Their Transformative Potential

Over the years, I've been captivated by the evolution of sailing and the recent advancements in hydrofoil technology, which promise a thrilling future for these marine crafts.

The technology supporting hydrofoil sailboats is rapidly advancing, bringing us closer to a world where boats gliding above the water's surface is a common sight.

These boats use 'wings' or foils submerged in water to lift the hull above the surface, reducing drag and allowing for greater speeds. This innovation is not just limited to racing but is expected to influence recreational and transport vessels in the future.

Today, we see hydrofoils in action with hydrofoil kiteboards, which have become popular among thrill-seekers. This is due to their ability to harness wind power and achieve impressive acceleration and agility on the water. This same principle is being applied to larger sailing vessels, where performance and sustainability converge.

The further development of hydrofoil technology involves intensive research into materials and design optimizations that can handle the challenges of varied sea conditions.

Electric and solar-powered hydrofoils are on the horizon, poised to significantly impact our world by offering greener alternatives to traditional boats.

Notably, the trends in hydrofoiling indicate a shift towards more sustainable sailing, utilizing advancements in electric propulsion systems to complement the inherent energy efficiency of hydrofoil designs.

The goal is a fleet of sailboats that are not just faster but more eco-friendly, promising an exciting future where the joy of sailing is in harmony with the health of our oceans.

Related Articles

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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” iFLY – Born to FLY “

Just enjoy foiling, ” high performance sailing “, ” we love speed “, ” join the adventure “.

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.

Crew 1-2 - max.180kg

Flysafe® foil control.

T-Foils Main Foils and Rudders FlySafe automatic dynamic foil control Additional Option: Main Foil Differential >>>

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LATEST DEVELOPMENT OF “DECK SWEEPING” MAINSAIL THE ROLLABLE HERU WING RIG LIGHT WIND FORESAIL «CodeF»

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Looking for the perfect setup for your foiling sailboat.

We can recommend the best iFLY setup and accessories for your boat. Get in touch for the ultimate sailing experience!

Performance

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…

HULL Design

full carbon – lightweight – performance design: Born to foil

High Performance Rig Options

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 >>>

Two Layer Trampoline

AERODYNAMIC INNOVATIVE WING TRAMPOLINE CREATING LIFT.

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SCIENTIFICALLY DEVELOPED high-end foils for early take off, high speed and maximum stability.

flySafe® dynamic foil control system

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 >>>

IFLY MAIN FOIL DIFFERENTIAL TECHNOLOGY

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 >>>

Innovations and more   >>>

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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Yachting World

• Digital Edition

Monofoil: The pocket rocket that can foil in just 8 knots of breeze

• Matthew Sheahan
• October 1, 2019

Built and developed in secret, the 8m Monofoil is a super-fast one-off foiling monohull, originally designed as a lake racer

The spectacle of a flying catamaran, be it an Olympic Nacra 17, a GC32, the recent America’s Cup 50-footers, or anything in between, has become almost normal in today’s racing world, so rapid has the shift to foiling been among multihulls.

But, even 17 years after they first appeared, the sight of a diminutive foiling Moth still turns heads. Foilers don’t have to be big to be impressive, balancing a single hull on a single foil is enough. Like those who can ride a unicycle, there’s something awe-inspiring about watching sailors who have pitch perfect balance fly a twitchy monohull while making it look like the most natural thing in the world.

There have been plenty of attempts to bring monohull foiling to bigger boats and to the masses. Yet no one has yet cracked the code, at least not for production boats.

Little surprise then, that whenever a new monohull foiler comes onto the scene it attracts plenty of attention. One of the latest is the 8m Swiss-built Monofoil. This extraordinary and complex looking boat is essentially a sportsboat with an open cockpit but with outrigger foils, like bicycle stabilisers, that generate righting moment by pushing upwards on the leeward side.

She was designed by Swiss match racing sailor Eric Monnin and built by Damian Weiss, both of whom shared a common goal: to create a fast foiling monohull for the European lakes.

Interestingly, neither had any desire to create a production version, nor tell the world that this was the answer for others. Instead, they simply wanted to find out if they could fly fast enough on one hull to stand a chance of winning some of the big prizes at Europe’s top lake races, including the famous Bol D’Or Mirabaud.

Article continues below…

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Eagle Class 53: The foiling cruiser inspired by the America’s Cup

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Launched in the spring of 2018 after two years of secret development, the initial signs looked good as the 8m sportsboat delivered an impressive opening performance, topping 25 knots on one of her first outings.

After a winter of tweaking and refining, where the team had increased the foils by 20% and reduced her overall weight by 50kg, the Monofoil was back afloat for this season. Shortly after her re-launch at Easter, it was clear that the team had raised the game.

“We can now foil upwind in just 8 knots of breeze,” said Monnin. “And when the breeze builds to 12 knots we are travelling at 16-20 knots at a true wind angle of around 50-60°. When it comes to downwind performance we can happily sit at 22 knots in 12 knots of wind with the gennaker. After that, when the breeze is up to 15-20 we are holding 24-27 knots with just the main and jib,” he continued.

The carbon bowsprit is 1.2m long and cants so the tack of the gennaker can be set further to windward, allowing the Monofoil to sail deeper

All impressive stuff for an 8m monohull. This is a proper pocket rocket that weighs just 650kg and can be rigged off the road trailer and launched in a couple of hours. Indeed, Monnin explains, her performance was in part limited by the need to keep the maximum beam down to 2.5m to meet European towing regulations.

Single hull foiling

So how does the Monofoil work? Setting the foils to one side to start with, the 8m long sportsboat flies a self-tacking jib upwind and a gennaker off a canting bowsprit downwind. She is designed to be raced by a full crew of four, including the helmsman, with two on trapezes to boost the righting moment.

She has a large square-topped mainsail that makes full use of the available space in a sail plan that sees the boom extend all the way to the transom where a full width traveller allows plenty of mainsheet tension to keep the head of the main stand up. This does mean she has a pair of running backstays rather than a single fixed stay, but double aft swept spreaders provide sufficient fore and aft support for the mast.

The foil deployed, but in the raised position. Normally it wouldn’t be underwater but the boat was heeled at the dock

Being a potent performer, she sails at high apparent wind speeds with the apparent wind ahead of the beam. This makes the full width mainsheet traveller an important feature to allow the mainsail to be dropped down to leeward while still maintaining leech tension, much like a multihull.

Her rudder is mounted on a transom-hung gantry to ensure greater efficiency for the T-foil blade. The rake of the rudder can be adjusted to alter the fore and aft trim of the boat.

While the foils look large and complex, their operation is surprisingly simple and belie the amount of work that has gone into designing a complete system that allows the curved foils to slide through a set of bearings in the hull.

A simple rope-driven worm drive alters the rake of the T-foil rudder, which in turn alters the trim of the boat. The rudder is mounted on a gantry off the transom to minimise cavitation

Much like the Beneteau Figaro 3, the idea is that both boards are lowered when sailing. Yet unlike the Figaro, the windward board is lifted partially to help raise it above the water’s surface and reduce the chances of it becoming immersed where it would create drag.

The clever part is the small amount of movement that is required to lift and lower the boards, especially when compared to the amount of movement required to raise and lower daggerboards on a modern multihull.

Also unlike the Figaro, the Monofoil’s boards are fully retracted in light winds. With very little of the foil in the water there is minimal drag and the boat can be sailed like any other monohull.

A custom bearing lets the daggerboard slide vertically to be raised or lowered. Rake is adjusted by the green line winding a worm drive

In these conditions the skinny and efficient 2.2m deep keel, with its 160kg bulb, is a good combination when the breeze is below 8 knots and allows the Monofoil to perform like any other similarly sized sportsboat.

The dihedral (upwards angle) of the foils is also an interesting feature that provides a degree of automatic heel control. As the boat accelerates and comes upright, so less of the foil is in the water, which reduces vertical lift.

Deceptively simple

At rest this boat does look pretty complex, yet once she’s rigged and underway you realise how simple she is to operate as well as how much effort has gone into designing her that way.

Below decks the full carbon construction is clear to see

This is an ingenious trailer-sailer that will fly in light conditions and be stable on foils right up through the wind range, something the crew demonstrated during this year’s Mirabaud Bol d’Or. As a vicious 50-plus knot storm swept through the fleet, she and her crew were one of the few to survive unscathed and go on to complete the overnight race.

The irony remains that – unlike many others in the Bol d’Or – this is not a boat that was intended to be the prototype for a new range of production foilers, even though she appears to provide answers to plenty of questions.

The bottom line is that the Monofoil seems to work. Irrespective of what speeds she clocks up, what is most impressive is how she performs across such a wide range of wind speeds.

Rectangular cut-outs in the hull allow the foil to be lowered completely on the leeward side. The windward foil is raised slightly in a similar way to pulling up a normal daggerboard

The Monofoil is no one-trick pony and while the concept wasn’t created for production, it could provide an appealing route for those who are realistic about their ability to learn how to balance like a Moth sailor, or ride a unicycle.

Specification

LOA: 8.0m (26ft 3in) Beam: 2.5m (8ft 2in) Displacement (empty): 850kg (1,874lb) Mast height: 12.2m (40ft 0in) Mainsail area: 32m 2 (345ft 2 ) Headsail area: 16m 2 (172ft 2 ) Gennaker area: 50m 2 (538ft 2 )

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Hydrofoils for Sailboats

• By By Steven Callahan
• Updated: July 29, 2020

Hydrofoils have been providing dynamic lift since fish sprouted fins. And people have been employing foils ever since they first put paddle to water, and certainly since adding keels and rudders to boats. But the modern, flying America’s Cup boats, kiteboards, Moth dinghies, shorthanded offshore thoroughbreds—these are all ­playing in a new world in which the terms “hydrofoils” or “lifting foils” describe those oriented to raise a hull or hulls from the water. In these racing realms, if you ain’t got foils, you ain’t got nothin’.

Lifting foils that allow these boats to sometimes home in on three times the wind speed might appear to be of little interest to cruising sailors, but with such common cruising features as self-steering and autopilots, self-tailing winches, rope clutches, fin keels and faster hull shapes all having been passed down from the racing scene, one must ask, “What promise, if any, do hydrofoils hold?”

Lifted or partially lifted boat patents extend back to 1869, but workable watercraft took roots along with early flight. Italian Enrico Forlanini began experimenting with foils in 1898. In 1906, his 1-ton 60 hp foiler reached 42.5 mph. Alexander Graham Bell’s HD-4 Hydrodrome flew on Bras d’ Or Lake at 70 mph in 1919. And several sailing foiler patents began appearing in the 1950s. Notably, JG Baker’s 26-foot monohull, Monitor, flew at 30-plus mph in 1955. Baker experimented with a number of foil configurations, and at least built, if not used, the first wing mast. The first offshore foiler was likely David Keiper’s flying trimaran, Williwaw , in which he crisscrossed the Pacific in the 1960s.

By the 1980s, numerous speed-trial and foil-enhanced offshore-racing multihulls showed huge promise, and have since evolved into behemoth trimarans clocking 30 to 40 knots continuously for long periods, not to mention the monohulls in the Vendée Globe (and soon the Ocean Race) that are capable of speeds exceeding 30 knots. But as boat designer Rodger Martin once reminded me, “If you want a new idea, look in an old book.” He was right. The fully foiling monohulls that will compete in the 2021 America’s Cup will bring things back full circle to the foiling monohull Monitor .

Fluid Dynamics Primer

Any foil—a wing, sail, keel, rudder or lifting foil—redirects the flow of fluid (air included), creating high- and low-pressure areas on opposite sides of the appendage, while developing lift perpendicular to the foil’s surface.

Advancements in foiling science is due in part to the hundreds of foil shapes that were tested, with tabulated results, by the National Advisory Committee for Aeronautics, the forerunner of the National Aeronautics and Space Administration. For the better part of a century now, aircraft and boat designers have been able to choose from a spectrum of refined foil sections that produce predictable amounts of lift and drag for known speeds of fluid and angles of attack, or the angle at which the foil passes through the fluid. Sections of efficient faster foils, as seen on jets or as we flatten our sails to go upwind or reach high speeds, have smaller nose radii and are thinner, with the thickest section of the foils farther aft, up to nearly halfway toward the trailing edge.

The most efficient foil sections at slow speeds are fatter, with the maximum thickness farther forward, and with larger nose radii, than faster foils. The angle to fluid flow or angle of attack also is greater. We see these slower foils on wings of prop planes and sails when off the wind or in light conditions.

Most sailors are familiar with traditional foils on boats, the teardrop sections of keels that produce lift to weather, reducing leeway, and of rudders, allowing them to steer. Even a flat plate can be a foil, but these tend to be inefficient. Such a shape is prone to fluid separation from the surface, meaning they stall easily, and they maintain poor lift-to-drag ratios. Even keels and rudders are somewhat lift-­compromised because they are ­symmetrical and have to work with fluid coming from either side, whereas lifting foils are more like aircraft wings or propellers, with asymmetrical sections honed for performance in a more stable, fluid flow.

The point is, any foil can be employed at various angles to the surface to prevent leeway, produce increased stability, or help lift the boat out of the water. But those not required to work with fluid flowing from opposite sides can then be honed to maximize lift and minimize drag. Asymmetrical foils were used on boats like Bruce King’s bilgeboarders, including Hawkeye , back in the 1970s. And, designers, including Olin Stephens, had previously employed trim tabs behind keels to improve keel performance.

Sails, which are heeled airfoils, not only drive the boat forward, but they also produce downforce, actually increasing the dynamic displacement of the boat. To counter this and keep the boat sailing more upright, multihull designer Dick Newick first employed slanted asymmetrical hydrofoils in the outer hulls of his small charter trimaran, Lark , in 1962. A portion of the lift developed by the hydrofoil resisted leeway, while a portion worked to actually lift the leeward hull, keeping the boat more upright and reducing dynamic displacement and drag.

Anyone who has ridden on even a foil-stabilized boat will know how riding at least lightly on the waves, and especially above them, beats smashing through them. When boats lift off, everything gets a lot smoother, drag falls away, and the boat accelerates.

Cruising on Foils

But why would a cruiser want to whip over the sea? Wouldn’t this demand an inordinate amount of attention by the crew? Would lifting foils even be applicable to a boat that must have substantial displacement to carry crew and stores? Aren’t cruising-boat hydrofoils an oxymoron?

Maybe, but I believe our boats’ hulls are likely to sprout fins much as fish have as we orient foils to more efficiently resist leeway, add stability, aid steering, reduce drag, increase comfort, allow for shallower draft, and enhance wider ­variations in hull shapes.

Boats have gotten increasingly wide through the years to advance form stability, improve performance (primarily off the wind), and boost interior volume. But the downside is that fat boats tend to slam more upwind. What if you could reduce dynamic displacement of the boat and lift that hull even partially from the water? The result would be less slamming, especially upwind.

At the same time, what about narrower boats that are known for being more seakindly, especially when closehauled, but lack form stability to carry adequate sail area for powering upwind, and tend to roll badly downwind? Or shallow-draft vessels that are lovely for cruising, but again, tend to suffer from reduced stability? Foils can give that stability back.

Looking ahead, boat ­designers might choose to reduce ballast, making up for it with a foil. In short, lifting foils can reduce boat drag and motion while increasing power and performance.

Pitching also does no favors for speed or crew comfort. Foils can come into play here as well. Foils parallel to the sea’s surface resist motion up and down, and a lifted boat skating above chop also is less prone to hobby-horsing through waves. Multihulls have always been particularly susceptible to pitching for a number of reasons, but watching videos of multihulls sailing to weather show an obvious huge advantage that foilers have compared with nonfoilers. Offshore multihulls now routinely employ T-foils on the rudders to control the fore and aft angles of the boat (attitude), a feature easily adaptable to any vessel.

OK, so what’s the cost? Obviously, the more things sticking through the hull, ­especially if they are retractable, the more it’s going to impact the interior. There would be added weight, complexity and cost. Foils also create noise, and there’s susceptibility to damage from hitting stuff. And let’s not forget compromises with shapes, purposes and things not yet imagined.

As for damage, it’s possible to fold the foils back into the hull. Think swinging center- boards or actual fish fins. Daggerboardlike foils can at least employ shock-absorbing systems similar to the daggerboard arrangements found in many multihulls. This includes weak links that are outside the hull, so if a foil is struck, it frees the foil to fold back or to come off before being destroyed or damaging the hull. Or, foils might hang from the deck rather than penetrating the hull, allowing them to kick up (and to be retrofitted to existing boats). These configurations also relieve the interior of intrusions, and keep the noise more removed from it. I have no doubt that numerous talented designers will be exploring all kinds of options and compromises in coming years, finding ways to make foils both practical and more than worth the compromises.

Sailing more upright, ­shallower draft, speed, ­comfort—what’s not to like? Just what is possible? I have a feeling the cruising community is about to find out.

Steven Callahan is a multihull aficionado, boat designer and the author of Adrift , an account of his 76 days spent in a life raft across the Atlantic.

• More: foils , How To , hydrofoils , print june july 2020 , sailboat design
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Four small boat pvc-foil furlers.

The development of reliable headsail furling must rank high on any list of devices that have significantly changed the way boats are sailed in the past two decades. Hanked-on sails, while having certain advantages, are disappearing in favor of roller furling jibs and genoas. Furlers keep the crew off the bow and reduce time spent sail handling. And thanks to improved designs, the sight of a tattered furling genoa flogging itself to death also is disappearing. Jams, once the bane of furlers, are much less frequent.

Practical Sailor has tracked the evolution of headsail furling for many years. In 1988 we undertook a comprehensive evaluation of available models and followed that in the May 15 and June 15, 1995 issues with a follow-up evaluation backed by a reader survey, which showed marked improvement in performance, reliability and customer satisfaction. At that time, 77% of all survey respondents said they would buy the same furler again, led by Cruising Design Inc. (CDI) and Famet (an older system) at 100%, followed by Profurl, Schaefer, Harken and Furlex.

In the November 15, 1997 issue, we again updated the group, highlighting the new Hood SeaFurl 5 and redesigned Furlex.

The Small Boat Market Average boat size in the 1995 reader survey was 32′. The number was drawn down a bit by the 25′ average size of boats equipped with CDI Flexible Furlers. Indeed, CDI has made a living selling furlers to owners of smaller boats, especially so-called “trailer sailers.” And while the other major manufacturers, such as Profurl, Harken, Hood, Furlex and Schaefer, have long offered their standard furlers in small boat sizes, and even some simplified models such as Hood’s Line Drive, none tried seriously to compete with CDI’s PVC luff extrusion.

The advantages of the plastic luff are several. First, unlike rigid aluminum luff extrusions, which are shipped in lengths of about 6′, and must be connected with splices or link plates and fasteners, pliable plastic extrusions are one piece and require no assembly. More and more boat owners are buying furlers from mail-order houses and doing the installation themselves. Secondly, the PVC can take a fair amount of abuse and is not as easily dented as rigid aluminum extrusions, an important consideration for any owner when stepping and unstepping the mast. It is of particular concern to owners of trailerable sailboats who handle the mast a lot. Thirdly, cost is less, making furling more affordable for owners of small boats.

Plastic won’t corrode, of course, but is subject to ultraviolet attack. Nevertheless, the addition of UV inhibitors should give them adequate life spans.

Three years ago, CDI’s dominance seemed about to change when Harken announced its first Heli-Foil, which used a PVC luff extrusion with an inner polypropylene sleeve over a braided stainless steel core. There were problems with it, however, and they took a long time to solve. Undaunted, Harken persisted and the new Heli-Foil is now available.

Not to be outdone, Hood Yacht Systems introduced its economical Sea Flex and Schaefer developed its SnapFurl.

We obtained furler kit packages of each, roughly sized for boats up to 24′ with maximum headstay lengths of about 30′ and maximum turnbuckle pin size of about 3/8″. Exact specifications are given in the table on p. 14.

Considerations All four foils come tightly coiled with warnings not to start cutting the bindings willy-nilly. There is a lot of energy packed in these foils that could cause an injury if handled carelessly. Most tell you to make sure the air temperature is at least 70°F and to uncoil outdoors; if it’s colder than 70°F, warm the foil indoors. CDI urges installers to uncoil within 24 hours of receipt so that the foil doesn’t take too much of a set. Observe directions regarding which end of the coil to start cutting free first as there will be a feeder near one end.

While all are flexible, they should be stored flat in the off season (assuming you’ve unstepped the mast). Allowing them to droop deeply also can cause them to take a set. They can be removed and coiled again, but Harken cautions that repeated tight coiling can reduce the life of the foil.

Because PVC is temperature sensitive, the manufacturers warn against exposing the luff extrusion to high heat—around 130°F-140°F. Such temperatures might be found under a boat cover in hot climates.

Presumably to reduce costs, only one of the four offers a line guide attached to the drum; that’s Schaefer and it’s a $23 option. This makes proper placement of the first lead block critical so that the line doesn’t chafe on the cage as it exits the drum.

The luff tape sewn to the jib or genoa will be #5 for Harken, Hood and Schaefer, #6 for the CDI Flexible Furler 2.

Ease of furling is affected most by the bearing surfaces, but also by the ratio of the foil diameter to the drum diameter; after all, the difference in the two is what gives you a mechanical advantage. The higher the ratio, the more advantage. We measured all four and developed these approximate ratios: Harken 2.5, Schaefer 2.14, Hood 1.65, and CDI 1.45.

Installation for any system will be easiest with the mast down but because you won’t have to completely remove the headstay for shortening the wire it is possible to do with the mast stepped. Nevertheless, you will have to unfasten the forestay from the stem to slide on the luff extrusion and torque tube/furling drum. Take a halyard forward to a strong attachment on deck, such as a toerail, to hold the mast while you work.

All four systems are fairly simple, with few pieces. The average do-it-yourselfer should be able to install his or her own with basic tools. The one critical job is cutting the luff extrusion to the right length. All manuals give explicit instructions—measure twice, or three times, and cut once.

Halyard restrainers may be necessary with any furler (except CDI with its internal halyard) if the angle of the halyard to the upper swivel is less than about 5°. A restrainer is a simple fitting that is screwed to the mast and through which the halyard is led to increase the angle. This is to prevent “halyard wrap,” in which the length of exposed halyard between the mast and the swivel wraps around the headstay as the sail is furled. You don’t want this!

Compared to larger boat furlers, these—especially the CDI and Sea Flex—are simpler and lack such features as integral adjusters.

CDI Flexible Furler 2 Joe Dahman bought CDI in 1984. At that time, Dahman said CDI was building furlers “on the floor” with metal luff extrusions and plastic links, which had a tendency to break. His first idea was to switch the materials. In the course of investigating and testing plastics, he came upon the idea of making the luff a continuous length, thereby omitting the link plates that trouble nearly every furler. If made of the right material, this single-piece luff extrusion would be much less resistant to damage when raising and lowering the spar, and enable CDI to ship the extrusion coiled in a box. He sold his first Flexible Furler in 1987 and since has delivered more than 10,000. He holds a patent on the flexible luff for which Schaefer is licensed by CDI; Harken and Hood are not.

Price is $515 list, and discounts through Defender Industries (800/628-8225) to about $300.

Unlike most furlers, the CDI uses an internal halyard, which eliminates the halyard swivel at the masthead. This places the furler in compression, not tension, and so the bearing is under less load. The halyard runs up inside one of two opposing grooves in the luff extrusion, through the Halyard Top Fitting, then back down to the head of the sail. The luff is not tensioned by this halyard, however, but by a short length of 1/8″ line seized in two to three parts between the tack of the sail and the downhaul shackle on the spool flange.

The standard furler comes with a UHMW polyethylene bushing as the bearing surface, though an optional bearing race is offered for $70 list. But instead of lots of small bearings, the FF2 model has seven 1/2″ Torlon bearings in a small race. Dahman says that a few large bearings work better and are more reliable than lots of small bearings, which have a greater tendency to get hung up on dirt or other debris in the race. The bearing kit is available as a retrofit; you can do the job in about five minutes.

Dahman has refined the system over the years, adding a few parts here and there. In 1990 a thrust bearing was added and in 1994 he replaced the aluminum cup or cage with stainless steel. For 2000, he enlarged the center hole to accept 5/16″ turnbuckles, crimped a ferrule to the halyard to secure the core to the cover where the line has been decored, and uses a larger 1/4″ braided halyard. Because the 42″ x 40″ coil size of the FF2 requires some straightening of the luff, CDI now offers a 6′ large hoop that is slightly less expensive but costs $60 to ship air freight. It does not require straightening.

There is no stainless feeder, like the Schaefer and Harken, just a slot in the foil, same as the Hood Sea Flex.

The manual with photos and drawings is adequate, if a slight bit confusing to follow at a few points.

The 3/16″ furling line is small to handle; we’d upgrade to1/4″.

In answer to criticisms that plastic luffs twist more than an aluminum luff, Dahman counters that aluminum twists more than people realize, principally at the section links, and that some twist is beneficial in spilling air in gusts.

CDI makes eight sizes of the Flexible Furler, from the FF1 to FF8, which is for maximum headstay lengths of 47′, 5/16″ wire and 1/2″ pin size.

CDI offers a lifetime warranty to the original buyer.

Bottom Line: The least expensive of the four, the Flexible Furler is simple and has a good track record with PS readers. It would be our choice among non-ball bearing models.

Schaefer SnapFurl Schaefer Marine has been making headsail furlers longer than just about any other company, dating to the 1970s when it made simple upper and lower bearing swivels for use with wire luff headsails.

Schaefer entered the modern era with its 1000, 2000, 3000 line in the early 1990s. It has since refined those models and more recently added its SnapFurl small-boat furler. It discounts to about $365.

SnapFurl’s single-groove foil is made of round, extruded PVC in two parts that snap together and interlock, which probably helps it resist twisting. The opposing forces of this joint also help the PVC straighten itself; Schaefer’s Fred Cook nevertheless recommends laying the PVC out in the warm sun for a while before assembly. The foil coils in a 34-1/2″ box.

The torque tube and drum are also injection molded plastic, a “long-grain nylon composite with UV inhibitors.” Bearings are Torlon, with two races in both the head swivel and drum. The two-part cage is stainless steel as is the sail feeder. The fasteners are captive so they won’t fall out if you have to disassemble the feeder.

The six-page manual with drawings is adequate.

Cook said that his company’s intent was to design a furler that was price competitive with CDI but retained some of the features of its other furlers, such as Torlon ball bearings and the ability to fit over the existing turnbuckle. It was also advantageous to use the same foil material as their Tuff Luff racing foil. They also wanted to price the SnapFurl lower than the Harken 00 Heli-Foil. About half of all SnapFurls are sold in Europe—France, England and Germany—Cook said.

Bottom Line: Innovative snap-together foil; stainless cage, feeder and aluminum upper swivel, and ball bearings make this a premium system at a low price.

Harken 00 Heli-Foil The Heli-Foil uses a PVC foil but with a polypropylene interior for what it says is an improved bearing surface. The PVC is cored with braided stainless steel for greater torsional rigidity. Of the four examined, Harken’s looks like it will resist twisting the best. Also, Harken’s foil is the only one of the four that has double grooves; this enables you to hoist a new sail before completely dousing and removing the existing sail.

With racers in mind, the two-part drum also may be removed as well as the halyard swivel, though the latter is probably more trouble than most owners will want to endure (you must rig a temporary headstay and disconnect the turnbuckle).

Discount price is about $700.

The drum is made of plastic while the cage, torque tube and halyard swivel are black anodized aluminum. Double races of Torlon bearings are used in each bearing. A torque tube key locks the foil inside the torque tube. A special clevis pin is required for your turnbuckle, available from Harken when you order your furler. It is longer than your existing clevis pin and locks the lower bearing fork to the turnbuckle and stem fitting.

Like Schaefer, Harken manufactures a complete line of accessory hardware.

Harken’s manual is excellent, with clear step-by-step instructions and accompanying photographs—the best of the group.

Bottom Line: The most expensive of the four, the Harken 00 Heli-Foil is also the most sophisticated with its stainless braid-reinforced PVC foil and aluminum parts; it’s also more versatile, should removing the drum for racing be of interest. Ideal for a J/80 or F/24.

Hood Sea Flex Sea Flex’s one-piece PVC foil is flat, like the CDI Flexible Furler, but has only one slot as it does not employ an internal halyard. It is reinforced with a 1 x 19 stainless wire running its length. This is supposed to help keep the foil from twisting but probably won’t be as effective as Harken’s larger diameter reinforcement.

The torque tube and upper swivel bearing are injection molded parts. The upper bearing has two races of Torlon ball bearings. The lower bearing is simply the stainless steel fork (which attaches to the turnbuckle with a clevis pin) turning inside a Teflon-impregnated Delrin insert in molded grooves in the lower end of the torque tube. Obviously this isn’t going to be as friction-free as one with ball bearings. However, it turned fairly easy…until we assembled the cage.

Like Harken, Hood’s lower bearing fork fits over the turnbuckle so that the clevis pin locks both to the stem fitting. On CDI and Schaefer, the pin simply passes through the slot in the turnbuckle body, which could cause it to unthread if sturdy cotter pins are not used to prevent the studs from turning in the body.

The fork has a second set of holes in case one wants to raise the unit with link plates.

The torque tube is cast in two pieces with threaded brass inserts for the six fasteners. The top and bottom of the drum are also black plastic and snap into grooves in the torque tube. They are easily removable for racing. The cage looks just like those on the SeaFurl 5; it is stainless steel. Assembly is quick, intuitive and actually quite clever.

The cage is held stationary by two pins snapped into the fork and also fits into grooves in the top and bottom cage parts. Thus, the plastic top and bottom cage parts revolve around the stainless, creating what we felt was excessive friction—certainly the most of the four furlers examined. When we queried Hood Yacht Systems’ Mike Haber, he admitted it turns roughly at first, but said that as the system wears in during actual use, there will be no problems furling.

Like the CDI, there is no metal feeder, just a slot cut in the foil.

The 8-page manual has drawings and is adequate.

Bottom Line: Hood Yacht System’s aim was to price the Sea Furl close to the CDI FF2, and it has done that—$311 at discount. While cleverly conceived, friction is a concern.

Conclusion Between the two least expensive—Hood and CDI—the latter has a bushing bearing at the bottom, with optional ball bearings. Hood does not. In addition, CDI’s internal halyard reduces friction. While we like Hood’s clever design, the CDI is a bit less money and has a long track record of customer satisfaction. At least until more experience is gained with the Sea Flex, we’d go with CDI. Owners of the Sea Flex are invited to give us their comments.

Schaefer prices out not much above CDI and Hood. It has just about everything Harken does—ball bearings top and bottom, many stainless parts, and what appears to be a good two-part luff extrusion—at a much lower price. It rates a Best Buy, hands down.

The Harken Heli-Foil is top quality and its split drum and excellent double-groove foil makes it the clear choice for performance sailors.

Contacts- CDI, 100 Cummings Center, Suite 106F, Beverly, MA 01915-3056; 978/922-5936; www.sailcdi.com. Harken Yacht Equipment, 1251 E. Wisconsin Ave., Pewaukee, WI 53072; 262/691-3320; www.harken.com. Hood Yacht Systems, 7712 Cheri Ct., Tampa, FL 33634; 813/885-2182; www.pompanette.com. Schaefer Marine, 158 Duchaine Blvd., New Bedford, MA 02745-1293; 508/995-9511; www.schaefermarine.com

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Home » Homebuilt Hydrofoil for Sailboats test sailed – end to hiking out?

Homebuilt Hydrofoil for Sailboats test sailed – end to hiking out?

Launching our Homebuilt Foil stabilised dinghy – this article is to use our experiment as the basis for low cost foiling that anyone can use to build or modify a boat – it sailed nicely in 5 to 10 knots and I didn’t have to do any hiking.

This is not about outright speed (wrong hull type for a start). It is about stability without hiking out. On the other hand if it works on this boat … it will work on anything!

No worthwhile video I am afraid – little wind when the photo boat was available on Sunday. We will get some next weekend with luck.

This is part of a four article set

• Part 1 – Sailing Trials in 5 to 10 knots of the hydrofoil stabilised dinghy.
• Part 2 – Building a Hydrofoil Stabilised dinghy – and proposal for comparison using any hull. Up later today
• Part 3 – Video in more wind – Next weekend if there is wind!
• Part 4 – Three Homebuilt hydrofoiling Projects – democratising foiling! Up Next week

Myth busting Foiling Boats – you don’t need a factory and you don’t need carbon fibre.

Everyone knew this once – because the recent history of making foiling work was achieved with homemade foils using timber and fibreglass.

The great Myth about foiling boats is “that it is high tech and everything has to be carbon”. But all the significant development in the Moth Class was with wooden hydrofoils that were fibreglassed with only small amounts of carbon or stainless steel.

The specification itself is to provide a basis for cheap experimentation and comparisons of performance.

The Foiling Moths advanced so quickly because there was a specification and people messed around with the spec and shared information. Wood and glass make fast modifications to homebuilt hydrofoils easier (and cheaper)

Maybe even racing if anyone has a mind to. But also as the basis of comparison with boats in other areas.

What does it feel like – a homemade foil stabilised boat upwind

We had good luck for the first day of testing – 5 to 10 knots and a well sailed Oz Goose as a pace boat. Started to get a feeling of the speed potential.

This section is about that.

Second day when we had a chase boat with cameras – of course the wind died. Hopefully we will have video next weekend.

The lateral foil to leeward needs to be kept in the water in the lulls. In 5 to 10 knots this meant sitting a little to leeward.

Initially as gusts hit I would follow instinct and make the wrong move. Hiking out brings the foil would to near the surface, would ventilate (suck air from the surface) and then the boat heel and slow.

Well … it is obvious … sit to leeward in the lulls, when the gust comes let the foil do the work – don’t move out to windward.

No Hiking. But with the same sail they were hiking in the accompanying Oz Goose .

So what to do when a boat with a lateral foil heels?

Don’t move your butt! Ease the sail and point a fraction lower to get the boatspeed up. The lateral foil starts to rise because of more lift – fly it up again.

Then I could wind in the sheet again to increase the heeling force. It is a feeling like flying. Boat heels then get speed without increasing the heeling force. Wind drops, move your body a little to leeward. Sheet loads seem higher – greater stability than hiking?

It becomes quite mesmerising watching the foil a foot or two below the water surface.

As the foil produces lift there is a depression in the surface of the water above the foil – which turns into a series of waves that make up the foil wake stretching back. It it like being followed by a small Loch Ness Monster.

It does also show that the homemade hydrofoil is developing lift at low speed.

The photo is at a very low windspeed/boatspeed. These wavelets go quite a way back. On Saturday with more wind and boatspeed I thought the transom was digging in and making a commotion.

But, it was the combination of the hull’s sternwave and the foil’s wake making a noisy quarter wave on the leeward side

So this is the exciting thing – not pure speed but less physical effort

At the moment many foiling systems are more or less being retrofitted to conventional boats.

Many of those boats are very wide – like the IMOCA 60s or some of the supermaxis.

Interestingly it is more moderate beam boats that win most races. They are faster in light winds, faster upwind and can sail deeper angles downwind without losing speed. A bit easier to steer too.

The question is … if we gain stability from a lateral hydrofoil – what is the beam for?

Canoes are light, fast and easy to store and transport. But can be hard to hold upright. PERHAPS this is a good place to start.

Another aspect is that modest length boats for disabled sailors have limited stability (and speed) because the centre of gravity of the crew is so high.

I also think about what will happen when I can’t hike out so hard. That’s why I win Oz Goose races. But I can certainly feel it in my 60 year old bones. The day is not close, but it is coming.

The inspiration of the Quant 28 and 17

Normally a keelboat this size without a canting keel would need 5 to 7 people on the rail.

Same lateral foil but a more beautiful version by Hugh Welbourne for Quant Boats in Switzerland.

The lateral foil is the simplest possible lifting foil.

In terms of stability – see how the crew on the Quant 17 go from full trapezing and hiking to sitting inside the boat when the foils are deployed and to leeward as soon as the boat has any downwind component.

I’m interested in the stability component.

In homebuilt hydrofoil boats Ian Henehan’s modified Oz Goose saw him chuck the hiking wings and start sitting inboard too.

It was like this with a hiking rack before – no longer needed. Simplification and less effort.

Perhaps: an advantage of some rocker for foiling dinghies

We didn’t fit a rudder foil at this stage – even though we built the rudder extension.

The purpose of a rudder foil on all foilers is to hold the main foil at an optimum angle of attack. Usually the rudder foil is adjustable in some way to allow the adjustment of the angle of the main foil.

If the rudder foil is sent lower then the angle of attack of the main foil is increased.

But with the 8ft boat with the extreme rocker it was possible to move back to increase the angle of incidence of the main foil. The base angle is 2 degrees Angle of Attack relative to the static waterline of the boat.

In the gusts of around 10 knots, going upwind, it was possible to move forward or back to reduce or increase lift – speed changes from doing so were instant. So where you sit in/on a rockered boat is a critical tuning factor.

Less rocker might be OK, but some rocker is going to be important. Maybe concentrated in the back end of the boat. I’m not sure if the foil fitted IMOCAs do this with water ballast.

Overview of comparison sailing the hydrofoiled boat against the larger Oz Goose

This is not necessarily a question of speed, though it is nice to get.

Our 8ft boat is absolutely sub optimal as a foil stabilised boat.

• It is short, so potential hull speed is low – 8ft long. This limits foil lift (square of velocity).
• It has a lot of rocker (fore and aft hull curve)
• Crew weight is a very large part compared to the boat volume – it was meant to be a prototype kid’s boat but the curved cockpit was too hard to build. So we repurposed it.

Saturday it was sailing around in company with Job and Jazmine in a Goose who I compete against in that class. They are among the top sailors in the Oz Goose so I know the speeds they hit. And the new boat has an Oz Goose Rig but is only 8ft to the Oz Goose’s 12ft length.

In the lighter patches it was noticeably slower than the Goose, but it was still sailing properly (felt normal/good). It was a faster choice to retract the foil. Pushed out to windward the hydrofoil is above the water to reduce the wetted surface.

With a bit more wind and foil deployed it started to equal the goose upwind. This is not something the shorter boat should be able to do.

The biggest difference – no hiking. While Job and Jazmine were hiking in the Oz Goose I found it best to move to keep the foil in the water in the lulls – which meant I was sitting centrally or to leeward and not hiking in the gusts. It is low effort sailing.

Downwind differences – was the 8ft foiled boat able to stick with the 12ft Oz Goose?

Downwind the Goose should have walked away from the smaller boat. I’ve a lot of experience with the 8ft Oz Racer and a GPS and know the boat tops out at around 4.2knots or just about 5. It can go quite a bit faster (up to 8knots) but it takes a lot of wind and it drops back to the 4 to 5kn range as soon as the gust drops slightly. The Goose, however just loves to accelerate into the 6 7 or 8 knot range and on stronger wind days gets up in the 8 to 12 knot range. And beyond.

So the Goose should get away from the shorter boat.

It did … but not too dramatically. More comparative trials to come.

Now we hope there is more wind next Saturday when we have the photographer and a chase boat.

Foiling Week 2018 Pt 2 – Foiling Sail for the rest of us!

Our recent articles on homemade foiling and

2 thoughts on “homebuilt hydrofoil for sailboats test sailed – end to hiking out”.

We just post an abstract of your pages about foils in our web site. Thanks for your job. Best regards Danilus

Merci Daniel!

Can you provide a link here to the article on your website.

Also we hope to get more wind to show how the foil behaves. We had one day of moderate wind but no photo/video boat. But last three weekends have had very light wind – sub 5kn. A more active video when Poseidon grants our wish.

Best wishes Michael

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