hydrofoil trimaran speed

Discover the Magic of Hydrofoil Sailboats

‍ 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

Daniel Wade

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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Sailing’s Hydrofoiling Revolution

• By Herb McCormick
• January 18, 2023

There’s a revolution underway in the sport of sailing, and it can be summed up in one simple word: foiling.

More specifically, we’re talking about hydrofoils , the winglike appendages mounted beneath the hull of a vessel that, at a certain speed, lift the hull clear of the water. When this happens, the foiling sailboats can reach speeds two or even three times faster than possible in “displacement” mode.

And sailboats are just one element of the foiling revolution: Surfboards, paddleboards and powerboats are also getting in on the act.

An Italian naval architect named Enrico Forlanini is credited with developing the first waterborne hydrofoils, which he affixed to a 60 hp, airscrew-driven craft that topped off at 36.9 knots back in 1906. In the century that followed, a series of would-be inventors took a swing at the concept with varying degrees of success. Foiling sailboats finally ascended into the mainstream during the 2013 America’s Cup, when Oracle Team USA beat Emirates Team New Zealand in a match between foiling 72-foot catamarans (the Cup has been contested in foiling cats ever since).

Surprisingly enough, my first foiling experience happened some three decades ago, aboard something called a Hobie TriFoiler, from the popular manufacturer of Hobie surfboards, beach cats and kayaks. The TriFoiler, basically a 22-foot trimaran with a central pod and a pair of mainsails stepped on the twin outriggers, was invented by a fanatical California engineer named Greg Ketterman. The sail controls were laid out just forward of the tiny airplane-style cockpit; you steered with foot pedals. It was so ridiculously easy that even a gremmie like me had the thing foiling within moments of getting in and reaching off.

But after the initial thrill, it was actually kind of boring. Which, I believe, is why it went out of production soon after. The TriFoiler was, unfortunately, way ahead of its time.

Such was the extent of my personal foiling experience until this past summer, when a new class of foiling monohull skiffs called Persico 69Fs rolled into my home waters for a series of races among youth squads in the class’s inaugural season. I got an invitation to take a spin.

After donning my helmet, wetsuit and life jacket, I was handed the helm with a pair of skilled young sailors on board. At 25 knots, we were towed into Narragansett Bay behind a powerful RIB, foiling all the way. It was terrifying. And a preview of coming attractions.

Once the tow dropped us, the sails went up and we bore off. I skied the tiller extension while scrambling out onto the hiking racks. Which sent us off on a screaming reach. Which flipped the 22-foot-7-inch carbon rocket ship.

Twenty seconds into foiling, and I’d capsized the bloody thing. How embarrassing.

The kids, bless them, were kind and patient. We got the whole shooting match, including ourselves, back upright and tried again. The mainsail trimmer sheeted it home, we started to accelerate, and he said: “Here we go! You’re up. You’re flying!” Indeed, we were.

Hard on the breeze in the 12-knot southwesterly, things unfolded quickly. Spray was flying, and I took more than one solid wave to the kisser. I was mostly too frightened to concentrate on anything but driving, but I did glance at the speedo once: 17.4 knots. (I felt pretty chuffed until later learning a 69F’s top speed is 34 knots. Ugh.)

However, I guess I’d proved the point: With a couple of sailors who know what they’re doing, foiling is for everyone. From now on, just call me Mr. Foiler.

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Foiling: the history of the hydrofoiler

• Matthew Sheahan
• December 9, 2021

Foiling has taken the watersports world by storm in recent years, but the history of the hydrofoiler goes back further than you might think

The biggest revolution to hit watersports in general has been foiling , and it’s easy to view the use of hydrofoils as a relatively recent phenomenon.

In truth, although foiling has really taken off (if you’ll forgive the pun) in recent years in everything from surfing to sailing, paddleboarding , and beyond, the history of the hydrofoil goes back far further than many might assume.

The world of powered foilers kicked things off early but even sail-powered foiling craft are much older than you may realise.

The history of foiling

The early development of hydrofoils started over 100 years ago when Italian Enrico Forlanini achieved 36.9 knots with his 60hp airscrew-driven boat in 1906. Several engineers took notice, among them the Wright Brothers and Alexander Graham Bell, both of whom experimented with foilborne craft.

Within a few years speeds moved briskly into the 50-knot range for power boats, but it wasn’t until 1938 that a sailing boat got up onto foils with Americans Gilruth and Carl who managed to foil at five knots. Here are some key moments:

1869 – First patent for hydrofoil was for a rowing boat, French application made by Emmanuel Denis Fargot.

First hydrofoil boat built by Enrico Forlanini

1906 – First hydrofoil boat designed and built by Enrico Forlanini. It had a ladder-type construction with multiple struts supporting multiple wings. It achieved 36.9 knots.

Alexander Graham Bell’s HD-4

1918 – Alexander Graham Bell and Casey Baldwin launched their HD-4, a five-tonne vessel powered by two liberty aircraft engines of 350hp each and reached 52 knots. The HD-4 Hydrodrome later set a new world record of 61.58 knots.

1938 – First known sailing hydrofoil was produced by Americans R. Gilruth and Bill Carl.

Gordon Baker’s Monitor

1955 – Monitor clocked at 25 knots. She was designed by Gordon Baker and built by the Baker Manufacturing Company of Evansville, Wisconsin. The US Navy shared part of the cost of construction.

In October 1956 she was recorded at 30.4 knots and was later said to have sailed close to 40 knots.

David Kelper’s Williwaw

1970 – The first hydrofoil cruiser. David Keiper’s Williwaw cruised throughout the South Pacific clocking up 20,000 miles.

1974 – Mayfly foiling cat established world record for A Class in Weymouth at 19.38 knots. In 1977 she set the bar higher at 23 knots.

Icarus, a modified foiling Tornado Photo: Claude Breton

1976 – Icarus , a modified foiling Tornado (above), set a new world record in B class at 20.70 knots. By 1985 Grogono and Fowler had raised their speed to 28.14 knots.

Offshore foiler Paul Ricard

1980 – Eric Tabarly beat the schooner Atlantic ’s transatlantic record by more than two days in offshore foiler Paul-Ricard .

1990 – Hobie Trifoiler, a twin-sail trimaran with a mainsail on each outrigger, capable of 30 knots, making it the fastest production sailboat in the world. The prototype, Longshot , was developed by Dan and Greg Ketterman with Russell Long.

1992 – Russell Long broke his own world records for the fourth time in the Trifoiler clocking 43.55 knots.

1994 – Alain Thébault’s L’Hydroptère foiling tri launched.

Techniques Avancées, a foilborne proa

1997 – Techniques Avancées , a French foilborne proa, set a new world speed record in the D class, at 42.12 knots

2005 – Rohan Veal wins the International Moth World Championship sailing a Moth class dinghy with hydrofoils fitted.

L’Hydroptère, former speed record holder. Photo: Christophe Launay

2009 – L’Hydroptère set new outright world speed record over 500m 51.36knots.

SailRocket2 clocked an unprecedented 64.45 knots

2012 – Sailrocket II broke L’Hydroptère ’s record to set new outright world record over 500m of 65.45knots.

2013 – The America’s Cup goes foiling as Oracle Team USA beat Emirates Team New Zealand both sailing foiling 72ft catamarans, the AC72s.

The G4 foiling catamaran

2015 – Gunboat launch the Gunboat G4, a foiling high performance cruising catamaran

IMOCA 60 Banque Populaire VIII, sailed by Armel Le Cléac’h wins the 2016/2017 Vendee Globe on a semi-foiling design

2016 – The Vendée Globe sees semi-foiling IMOCA 60 keelboats on the startline for the first time.

2017 – Emirates Team New Zealand win the America’s Cup in a foiling AC50 catamaran

Emirates Team New Zealand racing in the 2021 America’s Cup in Auckland, New Zealand. Photo: ACE / Studio Borlenghi

2021 – Emirates Team New Zealand defend the 2021 America’s Cup in a brand new foiling monohull, the AC75

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l’Hydroptère DCNS Hydrofoil Sailboat

l'Hydroptère is a hydrofoil-based experimental trimaran designed by Alain Thébault, a French yachtsman who is also the boat's captain. She officially became the world's fastest sailboat in November 2009, by breaking the outright nautical mile record. Approved by World Speed Record Council (WSRC), she recorded an average speed of 50.17kt over one nautical mile.

Hydrofoil-based trimaran

Construction Started

Maximum average speed, length overall.

l’Hydroptère is a hydrofoil-based experimental trimaran designed by Alain Thébault, a French yachtsman who is also the boat’s captain. She officially became the world’s fastest sailboat in November 2009, by breaking the outright nautical mile record. Approved by World Speed Record Council (WSRC), she recorded an average speed of 50.17kt over one nautical mile.

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The boat’s name ‘l’Hydroptère’ was derived from two Greek words: hydro and pteron, which mean water and wing respectively. In January 2012, DCNS, a French naval defence company and one of Europe’s leading shipbuilders, became the ship’s sponsor and consequently her name was changed to l’Hydroptère DCNS.

In August 2012, the sailboat arrived in San Francisco Bay to participate in America’s Cup World Series race.

History of l’Hydroptère

The conceptualisation of l’Hydroptère dates back to 1975 when late Éric Tabarly (July 1931 – June 1998), a famous French yachtsman and an officer in the French navy, was told about viability of such a project.

In 1983, Alain Thébault took over the project. With Éric Tabarly’s guidance, he was able to build a model of the boat in 1985 and sailed it on the Grand Canal at the Château of Versailles, France. In 1992, Alain was able to get support from DCNS, Aérospatiale, Dassault and the Chantiers de l’Atlantique shipyard. They all decided to become a part of the project.

Construction of the boat commenced in 1993, with DCNS manufacturing the hull. It was completed in 1994 and in her maiden flight, l’Hydroptère was able to achieve a speed of 28kt.

The ship was taken out of action in 1998 after one of her hydrofoils was torn away. The incident occurred when she was trying to break the speed record for 24 hours. She returned to the water two years later after being fitted with a new hydrofoil. She was also armed with a 3D flight simulator.

Design of the experimental trimaran

The l’Hydroptère DCNS project was made possible by combining aeronautical and marine techniques. The three-hulled trimaran can fly five meters above the surface of water. In flight mode, the boat’s contact area with water is reduced to 2.5m 2 .

The boat’s take off is attained by her hydrofoils, which are fitted underneath each of the outrigger hulls. These are angled at 45° in water and give an upward thrust as soon as the boat reaches 10kt speed. The thrust that makes the ship to rise above the surface of water is produced due the difference in pressure between the upper and lower surfaces of the foil. The lift increases with the increase in speed. The ship can reach a speed of 45kt from 20kt in ten seconds.

The ship’s hydrofoils or wings are made of titanium coated carbon fibre to make them stand against powerful stresses. The boat’s optimised shape, which was attained by applying aerodynamic principles, ensures that she gets maximum efficiency from her sails and at the same time keeps the wind-resistance to a minimum.

l’Hydroptère DCNS specifications and speed

Related project, .adastra superyacht, zhuhai, china.

Adastra is a trimaran-type superyacht built by McConaghy Boats for Hong Kong-based shipping baron Anto Marden. The 42.5m (140ft) superyacht has been designed by UK-based John Shuttleworth Yacht Designs.

The overall length of the boat is 22.48m. The beam is 24m and draft (while in water) is 3.5m. The ship’s draft is reduced to 2m while flying. The length of outrigger hulls is 6.7m, while the length of each hydrofoil is 5.7m. The boat’s weight is 7.5t.

The mast is 28m tall. Gennaker area and mainsail area of the sails are respectively 315m 2 and 185m 2 in size.

The trimaran requires about 12kt of stabilised speed to take off. Her speed is approximately two times that of wind; in other words the boat cruises at 30kt with 15kt of established speed. Maximum speed of the boat is 56kt and maximum average speed on one nautical mile is 50.17kt.

Contractors and suppliers involved in the hydrofoil trimaran project

Van Peteghem Lauriot-Prévost (VPLP), a French naval architectural company, and HDS were the main architects of l’Hydroptère DCNS.

The central hull of the boat was manufactured by DCNS Lorient, while floats and crossbeams were built by shipyards Decision and Airbus Nantes respectively. Foils and rudder were built by B & B and Airbus Nantes, and mast by Lorimat. Strain absorbers were provided by Legrand & Revigny.

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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.

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Hydrofoil Applications

The tendency to view hydrofoils only as a means to lift the hull or hulls clear of the sea is conditioned by the fact that hydrofoils have been applied mainly to engine-powered craft which are subject to a less complex set of forces than sailing craft. In Fig. 6-1, to obtain a quantitative feeling for the problem, we have plotted the vertical lift-to-drag ratio (weight-to-resistance) of a typical multihull craft as a function of VJ^/L using Eq. (1-8). Also shown is a curve labelled hydrofoils, which is characteristic of a set of deeply immersed hydrofoils together with the necessary struts. From this figure we see that the buoyancy/resistance figure for a good hull is greater than the lift/drag value of hydrofoils up to a value of VB/y/L * 2.5. The attainment of such high speeds requires that the boat be able to counter a large heeling moment and still keep the sail as near vertical as possible. It is in this regard that the primary application of hydrofoils to sailing craft arises. Although foil stabilization was used in the outrigger craft of Madagascar and Dar es Salaam, Edmond Bruce was the first to formulate the physics correctly.

In Fig. 6-2 we show a multihull craft equipped with a canted hydrofoil to leeward. In the (a) part of this figure the craft is at rest and the only forces in effect are the weight W which is opposed by the buoyancy B operating along the same vertical line. In the (b) part of the figure, the boat is in motion at a constant speed and a state of dynamic equilibrium exists. The basis for leaving the buoyancy in the same vertical line as the weight in this case is the assumption that we will be successful in eliminating the heeling moment. Were this assumption not justified, then the centre of buoyancy would move to leeward as the boat heels.

In order to enjoy a state of equilibrium, an extended body must experience no net forces in the vertical or horizontal directions. Also, the moment of the forces (torque) about any point must vanish. For the present purpose we can neglect the forces normal to the page, that is, the driving force and the drag. The vanishing of the forces implies

Fig. 6-1. A comparison of the lift/drag characteristics of fine hulls and hydrofoils.

Multiplying Eq. (6-1) by sin 9 and Eq. (6-2) by cos 0 (where 0 is the dihedral angle of the foil) and adding, we find

By virtue of Eq. (6-2), we see that the vertical component of the hydrofoil force is f cos 0 - Fy ctn 0.

Dihedral angle

Fig. 6-2. A Bruce foil-equipped sailing craft in static and dynamic equilibrium.

Using Eq. (6-3), we can now express the buoyancy as

Thus our hydrofoil sailing craft in dynamic equilibrium can be reduced to the force diagram shown in Fig. 6-3. By taking moments about any point on this figure and setting them equal to zero, we are led to the following key relation:

Since Fy is never zero except in the trivial static case, the quantity in parentheses must vanish in order to ensure the vanishing of the heeling torque. Thus y = h tan 0. (6-7)

Having found the dimensional relationship that causes the heeling torque to vanish, we must now ask ourselves the following question. How large can Fy be (or, equivalently, how much sail can be carried in a given wind) in order that Eq. (6-6) still be satisfied? The answer to this question is contained in Eq. (6-5). This equation describes the decrease of B, the buoyancy, as Fy increases, thus increasing the vertical component of the foil force. As F approaches a value W tan 0, the 62 buoyancy approaches zero as the nulls lift out. At the point of liftoff, y

Fig. 6-3. Equivalent force diagram for sub-lift-off speeds.

Fig. 6-4. Equivalent force diagram at lift-off.

Fig. 6-5. A Bruce foil craft with windward stabilization.

high speed the force diagram tends to that shown in Fig. 6-4. The force components sailing Fy ctn 6 of the righting couple have reached a maximum value W; the corresponding righting moment is therefore

and any further increase in Fy over the value W tan 9 will lead to capsize. If we were to replace the foil unit by a light nonsubmersible hull, the same value of maximum righting moment obtains. The virtue of the leeward canted foil arrangement, known as a Bruce foil, is that 1) no heeling at all is experienced up to the point of liftoff, thus keeping the driving effort of the sails at a maximum, and 2) the heeling force Fh has been converted into vertical lift thereby reducing the drag of the hulls.

It is also possible to cancel the heeling torque by using a canted foil to windward that depresses rather than lifts the boat as shown in Fig. 6-5. One may also derive Eq. (6-6) for this case. There are two outstanding disadvantages to this arrangement, however. First, the hulls are being depressed and so the hull drag is a rapidly increasing function of Fy. Second, and even more important, the windward foil arrangement is unstable. If a leeward foil pops out of the water owing to wave action, then the heeling torque acts to quickly reimmerse the foil. If a windward foil comes unstuck, the heeling torque is then uncountered by a windward depression and the craft will probably capsize very quickly. For this reason, a leeward Bruce foil or foils having a dihedral angle 9 such that y = h tan 0, is the best choice for vertical lift and lateral roll stabilization. In choosing the dihedral angle 0, we find that angles in the range 40-45 degs are probably best. If the angle is very much greater than 45 degs, then the beam necessary to satisfy Eq. (6-7) becomes excessive. If 9 is too small, the foil area or leeway angle must be large in order to generate a horizontal force component equal to Fy.

Now let us see what type of hydrofoils are suitable for use on sailing craft. Hydrofoils can be separated into two classes depending on whether the blades are wholly immersed by struts or whether the foils themselves pierce the surface. In order for the boat to have vertical stability, the hydrofoils must somehow manage to "see" the air-water interface and thus be able to respond to a vertical displacement perturbation in such a way as to rapidly restore the original flight altitude. Fully immersed foils can only do this by operating very near the surface where lift is a sensitive function of depth, or by having a surface sensor that transmits orders to the hydrodoil for required changes in angle of attack. The first method, employed extensively by the Russians in their large powered river craft, is useless in any sort of sea. The second method has been explored by Hook and others. At the present stage of development, this feedback method is, in the author's estimation, too heavy and complicated to be appealing.

The outlook for surface-piercing hydrofoils is much better. To a first approximation, the lift exerted by a hydrofoil at a given speed varies linearly with its depth of immersion and with the angle of attack of the water llow onto the foil a. In Fig. 6-6a we see a hydrofoil 64 experiencing a llow with angle of attack a. If a downward displacement

occurs, the hydrofoil experiences an additional component of fluid velocity from below. This is interpreted as an increase in the angle of attack as shown in Fig. 6-6b. If the displacement is upward, the effect is a reduction of a and the foil tends to loose lift in opposition to the perturbation (Fig. 6-6c.) The effect is entirely analogous to that described in Chapter 5 for yawing sails and keels. Thus we see that the hydrofoil resists vertical displacements with a force proportional both to the displacement and the rate of displacement. This tendency to resist changes in the vertical direction is powerfully augmented in the case of surface-piercing foils by the automatic variation of the foil area; that is, if a perturbation depresses the foil below its equilibrium water-line, the action of the increased area tends to restore the equilibrium while the change of apparent angle of attack tends to damp the motion and prevent overshoot.

Vee foil Ladder foil

Fig. 6-7. Monoplanar and multiplanar surface-piercing hydrofoils.

Surface-piercing hydrofoils may be mono- or multi-planar as shown in Fig. 6-7. For smooth-water sailing the monoplanar foil works quite well, however for offshore sailing the ladder foil should be preferred. The large reserve of unimmersed foil in the ladder arrangement can exert high lift as the foil enters a wave. The monoplanar foil is generally used in powered vessels designed to operate foil-borne only over a narrow range of speeds. In sailing, our source of power and 65

consequent speed varies over a wide range. In a multiplanar ladder, the foil section can be varied from a high lift, low section near the static waterline to a section more appropriate to high speeds at the bottom of the ladder.

Now let us examine the effect of wave action upon hydrofoils. In Fig. 6-8 we have indicated the motions of individual elements of water

Fig. 6-8. Water particle motion under wave action.

as a wave passes through from left to right. These orbits are circular with a diameter equal to the wave height at the surface and tend to a shuffling back and forth at greater depth. Now consider a hydrofoil-borne craft sailing to weather, that is, moving against the wave motion. Since the water on the front of the wave is rising, the foil sees this as an increase in angle of attack and the lift is increased. The hydrofoil therefore tends to climb the wave rather than hold a constant altitude. On the back side of the wave, the water is falling. This is seen as a decrease in angle of attack, lift decreases, and the boat tends to contour the back side of the wave as well In a following sea, the situation is more serious. If a foil-borne craft moves to leeward fast enough to overtake the waves, then it will tend to plow into the back side as the apparent angle of attack of the foil decreases. It is for just this situation that the ladder foil arrangement realizes its maximum advantage.

66 Tig. 6-9. An antiventilation fcncc.

The pressure on the curved surface of a hydrofoil is lower than that hydrofoil on the flat side. In surface-piercing operation, a portion of the curved applica-surface of the hydrofoil near the air-water surface may experience a tions pressure below atmospheric. This leads to the formation of a cavity and the entry of air from the surface, thus resulting in a loss of lift. This phenomenon is known as ventilation. It is controlled by the use of fences as shown in Fig. 6-9. It is also helpful if the foil or strut can be angled forward in order that the surface water encountering the member is given a velocity up the strut. This technique was used by Keiper on the trans-Pacific foil trimaran Williwaw with considerable success.

At higher speeds for a given chord length, the pressure at some point on the hydrofoil finally falls below the vapour pressure of the surrounding water. Bubbles then form as local boiling commences. These bubbles move aft along the foil surface and as the pressure rises, the bubbles collapse. The impulsive pressures on the foil surface as these cavitation bubbles collapse are several thousand pounds per square inch and pitting of the foil surface usually results. The speed at which cavitation begins lies in the 40 knots plus range for most hydrofoils and so does not concern us other than for a large sailing speed record machine. Such an ultimate sailing craft might well be equipped with a ladder foil arrangement having a supercavitating foil as its bottom rung. Such a section is shown in Fig. 6-10.

We would now like to address ourselves to the question of the configuration into which the hydrofoils should be arranged on a sailing boat. It is immediately evident that the hydrofoil array must have considerable extent in both the transverse and longitudinal directions, hence the buoyancy for sub-foiling conditions must be provided by an arrangement of multiple hulls, that is, a catamaran , trimaran, or proa.

The hydrofoil configuration will be symmetrical about the longitudinal centreline when applied to a symmetrical hull layout such as the catamaran or trimaran. The two simplest configurations in such a case are the aeroplane and canard. These two configurations are shown in Figs. 6-11 and 6-12. The aeroplane configuration features the Bruce foils in a forward location, carrying most of the weight, and the steerable stern foil serves as a pitch stabilizer. The canard configuration has its lightly loaded pitch stabilizer in the bow and the Bruce foils near the stern. The question of which hull arrangement is best with which foil arrangement may have to be decided by the question of accommodation or crew placement, however, for offshore work a trimaran-cunurd is likely to be best. 67

As we have previously noted, a hydrofoil unit is analogous to a damped spring by virtue of the dependence of its lift on the depth of immersion and rate of immersion. The stiffness of the spring is proportional to the rate of change of lift with depth of immersion (small chord = stiff foil) and the damping rate is proportional to the rate of change of lift with angle of attack since vertical velocity of the unit results in a proportional change in angle of attack. A foil of large chord operated at a low angle of attack has such a high damping rate. If the bow and stern foils have identical characteristics or if the stern foil is stiffer, a pitching perturbation can induce a porpoising type of instability. In conditions where one is running into a following 68 sea, a highly damped stern foil and a stiff bow foil provide excellent

pitch control. In practical terms, this calls for a lightly loaded bow foil operated at a high angle of attack and a stern foil carrying about £5 percent of the weight operated at the angle of attack corresponding to maximum In a hull-borne craft, these characteristics are obtained by using a fine bow with generous flare above the waterline and a broad, flat run off at the stern. Thus the canard configuration should be expected to be far superior to the aeroplane configuration in pitch control. In lateral roll control there is not much to choose between the two. If the two main foils are both canted lifters (the leeward Bruce foil configuration) then the angle of leeway will tend to increase the angle of attack of the lee foil and decrease the angle of attack of the weather foil. In order to operate on either tack in satisfaction of Eq. (6-7), the beam would have to be approximately twice the height of the centre of effort which is unlikely. Thus a laterally symmetrical hydrofoil craft will experience some heeling to leeward which also serves to nullify the lift of the windward foil by lifting it partially or wholly out of the water.

Now let us examine the laterally asymmetric proa foil configuration. This arrangement has a decided advantage in heeling control since, using a sail plan of modest overall aspect ratio such as the pyramid rig, the condition for heeling cancelation can be met. In order to gain pitch control, it is necessary to split the Bruce foil into two units located at either end of a long, slim leeward hull as shown in Fig. 6-13. The bow unit can then be operated at a slightly higher angle of attack than the stern unit in order to provide the necessary longitudinal distribution of stiffness and damping.

At this point I would like to address the question of extending the righting moment of an ideal Bruce foil proa beyond the value given by Eq. (6-8). It is obvious that this can only be done by adding weight to the windward hull or by using a windward hydrofoil unit that exerts a downward force. Both of these suggestions have advantages and disadvantages.

high speed Harry Stover has suggested that a water scoop might be used to sailing increase the weight of the windward hull as boat speed and heeling moment increase. The main problems with this suggestion would seem to be the large drag induced by such a scoop and the inability to regain buoyancy in the windward hull on short notice. The windward depressing foil also must pay the penalty of increased drag owing to the fact that the Bruce foils have not only to lift the weight of the boat, but also the windward foil force K. For this case, assuming the foil units to operate at a lift/drag ratio of 10, it can be shown that the effective horizontal lift/drag ratio in terms of which the drag angle 3h is defined is

Continue reading here: Dihedral Lift Foil

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Readers' Questions

What ut a hydrofoil hiat?

A hydrofoil boat is a type of boat that uses foils mounted under the hull to lift them above the water surface, reducing drag and allowing for higher speeds and greater fuel efficiency.

Can hydrofoil sail against rough seas?

Yes, hydrofoils can sail against rough seas. Hydrofoils are designed to efficiently move through the waves and can be used in various sea states. However, the waves need to be below a certain size so that the hydrofoil can efficiently move through them.

How do yachting foils work?

Yachting foils are designed to lift the hull of a yacht out of the water when sailing at high speed, reducing drag and increasing performance. Foils are mounted on the stern and bow of the boat, with the main foil mounted on the centerline and two smaller foils mounted on the sides. These foils create a pocket of low pressure under the hull, which lifts the boat out of the water, much like an airplane in flight. The leading edge of the foils act like wings, cutting through the water and creating lift, while the trailing edge helps to guide the flow of water along the underside of the boat, thereby reducing drag and increasing speed.

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The Race to Break the Speed Record

• By Kimball Livingston
• Updated: October 26, 2021

If Alex Caizergues succeeds at breaking the speed sailing world record in 2022, it will be his third time around using a kite, but otherwise completely different from his first two records. Those marks—50.57 knots in 2008 and 54.10 in 2010—were set when foiling boards were continually upping the 500-meter mark, sometimes more than once a year. Caizergues’ 2010 run added 3 knots to what the famed trimaran L’Hydroptere had shown us only a year before. But all those efforts ran into cavitation trouble at about 52 knots, that point when flow over the foils boils into vapor—the point at which control vanishes. For his early records, Caizergues used a hydrofoil to lift him above the water. Now, with his Syroco team based in Marseille, France, he intends to use a hydrofoil to hold him down.

We’ll come back to that.

Nine years after Paul Larsen’s record run at 65.45 knots in Sailrocket , the French Syroco team has rivals in Switzerland following what they believe is a more conservative path. The École Polytechnique Fédérale de Lausanne is a public research facility where the speed quest caught fire with student engineers and professors, including some who helped develop L’Hydroptere back in the day. SP80 is the team name, taken from the goal of achieving 80 knots, a goal shared with Syroco. They have a kissing-cousin relationship, competition aside.

SP80 envisions hitting 80 knots with a kite pulling a surface-skimming trimaran. A subsurface superventilating foil counters the lift of the kite, and a mechanical interface aligns the forces. Syroco’s purified vision aims to put a kite in the air connected by wires to a pod also in the air carrying two “pilots.” That pod will have a single, tiny-as-possible connection to a supercavitating subsurface foil holding it down. The concept strips the speed problem to its barest fundamentals, exponentially raising the complexity of execution.

Neither concept would pass as a boat in Blue Blazerville. Both owe their origins to Bernard Smith’s book, The 40-Knot Sailboat , published in 1963 . Smith proposed a balance of opposing forces to avoid the ultimate instability that eventually and inevitably develops as power is added, and any ordinary craft will capsize. Sailrocket showed the way and validated the theory—using a canted wing, countered by a superventilating foil in the water. On November 24, 2012, with sponsorship money down to nickels and the weather window closing, Larsen clocked his 65.45-knot run at Walvis Bay, Namibia. These days, Larsen says he appreciates the respect shown by the principals of SP80 and Syroco when they call themselves “children of Sailrocket .” But when we keep this Australian-born Briton talking, we get to the part where he’s saying how the machine was packed away in a container in Namibia after just a few days of finally showing its potential, and there’s still gas in the tank and…

There’s nothing shaking right now, but don’t dismiss the current record holder, 49 years after the catamaran Crossbow set the first official 500-meter record at 26.30 knots. For bonus points, do you know how 500 meters became a standard record distance?

The simple answer: In 1972, when Crossbow was first contending at Weymouth, UK, that length fit the venue. If someone manages 80 knots in 2022, they will cover 500 meters in 12.15 seconds, a football field every 2.5 seconds.

Later, while we’re ­talking records, we’ll update the renovation of L’Hydroptere . First, let’s get up to speed on the essential terms. Supercavitation refers to a regime in which a small, highly loaded, wedge-shaped (­triangular profile) foil builds a stable vapor pocket that bypasses the limits of ­cavitation. Superventilation refers to the principle employed by Sailrocket , with a foil that encouraged ambient air pressure to travel down the entire length and span of the foil.

The SP80 team puts it this way: “A triangular profile allows air from the atmosphere to dive into the extrados side caught by the depression, forming a stable air bubble that will prevent ­cavitation inception.”

Got it? Hey, they’re engineers.

Caizergues is aiming for more than a speed record with his Syroco concept. He knows from experience that when you succeed, you’re done and, “It’s an empty feeling.” This time, he’s ambitiously building a scientific and technical company around Syroco with the aim of reducing carbon emissions in the transportation and energy sectors. Co-founder Olivier Taillard, a Mini-Transat veteran, relates: “We founded the company in 2019 and built a team of 20. That includes three Ph.D.s in physics. To date, we have created 12 innovations, with three in the market. One is a software tool now in use to maximize ­efficiency in shipping routes.”

Other developments are aimed at keeping that critical hydrofoil just barely under the surface of the water, doing its supercavitating thing. Under the rules of the World Sailing Speed Record Council, only ­mechanical systems are allowed. It can’t be computerized or fly-by-wire. To a pointed question about systems, Caizergues responds with a laugh and a cagey hint: “Because of the wire, we’ll have air coming down from the surface, so it’s going to be about managing ventilation along with employing the principles of supercavitation. Not a lot of work has been done in this area, so we’re leading the way.” Prototype testing began in summer 2021, with plans to go for the record in 2022. Alongside more sober developments aimed directly at the marketplace, the team calls this one “the moonshot.”

When these people talk to each other, they toss around stuff like “turbulent viscosity formula in the Standard K-Epsilon model.” It’s not “let it out till it luffs, then pull it in.” SP80 co-founder Mayeul van den Broek observes: “Like Sailrocket , both of the current record efforts are based on the concept of aligning opposed forces, but then you prioritize either efficiency, power or stability. Syroco chose ­efficiency as a top priority. We chose stability, which is why we are producing such a different realization of the same concept.”

The SP80 principals witnessed L’Hydroptere ’s stunning record run in 2009 and never quite got over it. Then, during a university competition to design the most efficient radio-controlled boat, they developed a hankering to try a superventilating foil on a kiteboard. When Benoit Gaudiot easily hit 41 knots, van den Broek says: “We saw that the rider was the weak link, and if we wanted to go faster, we would need a rigid link between the kite and the foil. Then, well, we might as well go for the record. We will use inflatable kites, even though a wing might be more efficient, because new-­generation kites will serve at 80 knots. We can be versatile, launching kites from 20 to 50 square meters for different conditions.”

Their superventilating foils, Gaudiot says, “will have water flowing on one side and air on the other. Sailrocket used similar superventilating foils. That is less efficient than a supercavitating foil generating vapor, but it’s a lot more stable. A superventilating foil at low speed will develop more drag than a conventional foil. At high speed, it has no limits.”

SP80′s link between airfoil and hydrofoil depends upon a module that is, “mechanical but automatic,” according to van den Broek. “It will be close to the controls of a conventional kite.” Gaudiot adds, “Having one line carry all the power allows you to know exactly where that power will be coming from, and you can advance it into the window ahead for best ­performance, like any kite.”

In theory, there is no ­heeling and no capsizing because the power of the kite is countered by the force of the foil. As with Syroco, 2022 is the target record date.

Last year, we wrote in these pages about an ambitious plan to rehab the 60-foot ­foiling trimaran L’Hydroptere and put the old girl to work as a point-to-point record hunter. Gabriel Terrasse and Chris Welsh partnered to buy the legendary campaigner, once left derelict in Hawaii. They patched it up and had it sailed to San Francisco, where it was taken apart with an intent to rebuild it better than ever. Work was well along when Welsh—who would have carried on with or without sponsorship—died suddenly, and all bets were off, save for Terrasse’s persistence.

“We’re looking for ­sponsors,” Terrasse says, “and we have engineers studying how to add ground effect to L’Hydroptere 2.0 along with new foils, a longer and lighter main hull, a wingsail, global aerodynamic optimization and much more. It was hard to lose Chris. We shared the dream. But L’Hydroptere has great potential to serve science and catalyze innovation.”

L’Hydroptere ’s 51.36-knot run in 2009 represented a last shot at setting speed records on water through pure muscle. Paul Larsen’s nine-year quest to solve the problem at a technical level culminated in that 65.45-knot run in 2012. Today the beast is still in a dark container in Namibia where Larsen packed it away. And yes, considering that Sailrocket had only a handful of runs in what turned out to be record-setting mode—fat foils, not thin foils, and according to the team’s VPP, 65 knots was a worst-case outcome; everything was structured to go 80 knots—it’s tempting to imagine putting Sailrocket 2 back on the track. What would change is the safety regime. It’s not hard to find videos online of early-­version Sailrocket 1 going aerial.

“In any future scenario, I’d want a roll cage and oxygen,” Larsen says, “and maybe I’m at a point where I’d be happy to see someone else sitting there.”

“Tell Paul he’s getting soft,” was the joking comeback from Richard Jenkins when I mentioned that to him. Jenkins holds the land-speed sailing record at 126.2 knots, which took him “only” 10 years of trying as his various iterations developed. As far as we know, no one is challenging that record today. Jenkins’ story speaks to the difficulty of these endeavors in any medium. He says: “I’m often asked if I would try to break the record again. If I had unlimited funding and built a new vehicle, based on my ­cumulative ­knowledge, it might take me five years or more, and then we’d probably see an increment of 1 or 2 percent. It takes being in the right place at the right time, with certified observers, which is hard to put together. You then have to be technically perfect, at the right moment, with virtually no testing because wind might come suddenly. It takes a great deal of time and experience—and then you shoot from the hip. I have better things to do.”

Running his company, Saildrone, for example, with which Jenkins does his own part to care for the planet by fielding autonomous surface vehicles for ocean research. Having built a kite-powered ­trimaran 20 years ago, Jenkins worries the Swiss are “barking up the wrong tree.” But technologies evolve, and 2022 bids to be a fascinating time. Of Syroco’s moonshot, Taillard says: “Half of our brain power is spent making it safe. If a foil breaks, or if it comes out of the water—which isn’t going to ­happen—all safety systems have to work perfectly.”

Caizergues, who will be in Syroco’s control pod with a co-pilot, adds: “One of the goals is to produce a craft that will be safe for me to drive. And to crash. Helmets, oxygen, padding, quick-release mechanisms for sure, and we’re not committed to air bags, but maybe.”

Syroco and SP80 intend to run in the south of France, where the Mistral roars down to the Med. It worked for L’Hydroptere , but these new efforts place ever more extreme demands upon managing the interface between air and water, which at sea level is 784 times the density of air. The world will be watching, and perhaps I speak for many when I say, “Gentlemen: May the alignments of force be with you.”

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FEATURE | The future of hydrofoils

The following is the presentation given at the fiftieth anniversary virtual symposium of the International Hydrofoil Society (IHS) by Professor Karl Gunter Wilhelm Hoppe – naval architect at the Technical University of Berlin, Emeritus Professor at Stellenbosch University in South Africa, and director at Foil Assisted Ship Technologies.

Hydrofoils are hybrids of a planing monohull with a foil system. Hydrofoils were developed over 100 years now with some high-tech applications in the 1960s and 1980s.

The fact that the IHS still exists means there is still strong public interest in hydrofoil development even though they are not anymore in the public news.

However, some of the later hydrofoils are still in operation in certain countries and especially the Russian river hydrofoils.  And yet the talk still goes around that hydrofoils are "drying out" and becoming relics that belong in museums.

Inevitably, a question has arisen after so many years have passed without virtually any new hydrofoils being built: Did we run out of experts to design hydrofoils and build them?

The clear answer is no, as hydrofoil systems have strong applications in sailboats now with extremely high tech applications reaching over 50 knots in much slower winds.

However, these are mainly sport sailboats. Why then did the hydrofoils seem to disappear?

One has to look carefully at the design of hydrofoils to find out what the real reasons of their neglect could be and find out what restraints are involved as well as the associated costs.

The two photos below show examples of hydrofoils.

There are many different foil forms and combinations with monohulls.

There are V-shape foil systems, flat type foils and deeply submerged foils; mostly all foils come in pairs for longitudinal stability. The fundamental design concept behind all hydrofoils is the idea that the foil must carry the full load weight of the craft, driving the hull out of the water and letting the foil carry all the weight with the hull being carried as deadweight, which is only there to supply sufficient buoyancy at rest and low speed.

The request for safe stability complicates the hydrofoils and this led to various ways, either to have fixed foil systems with the V-foils piercing the surface or later developments with full submerged foils and angular automatic foil control which ended up in the Boeing hydrofoils' high-tech wave scanning system as used in aircraft – which increases costs considerably.

Another design request concerns the operation in open sea waves to let the hydrofoil platforming, which means it is not following the wave surface contour but runs on a horizontal plane. This required the foils to be deeply submerged with long struts to transmit the full weight force into the hull, which is not supposed to have any water contact when the hydrofoil is "foilborne."

These foils and struts were of solid high tensile steel and had to have polished surfaces as the foils lose efficiency when the surfaces are rough.  In seawater, especially in warm, tropical areas, foils needed to be kept clean of fouling.

All these restraints led to expensive craft and high maintenance costs.

Propulsion systems are challenging with very long propeller shafts and low OPC data.  To get the hydrofoil rising at start speed, considerable power is required before it becomes foilborne.

In very bad weather only very slow speed can be used with bad efficiency and bad sea-keeping due to the low deadrise of hull. Turbine and air propulsion have low efficiency.

Hydrofoil wings at very high speed have to be extremely slender with low thickness over chord to prevent cavitation.  Such wings are highly stressed and bends and struts are required to carry the ship's weight load.

These struts create additional resistance reducing craft efficiency. They also increase ship weight and costs.

Operational constraints

At speed, hydrofoils run high above the water. This increases their tendency to experience accidents when hitting floating objects. If these objects are solid like floating containers or floating trees, the hydrofoil will come to an abrupt standstill and crash into the sea with full power on.

Several fatalities were recorded in Hong Kong with the Boeing-type Hydrofoil ferries. Even the US Navy hydrofoil patrol boat USS Tucumcari had a serious accident wherein it struck a coral reef and ended up with some crewmembers sustaining serious – but non-life-threatening – injuries.

Hydrofoils require deep harbours and they cannot navigate in smaller harbors. They are not able to approach typical sandy beaches or land on one.

A Thai company had asked us to design a Hysucraft for beach landing as their Russian hydrofoil could not approach the beach to deliver passengers. The project did not materialise as local fishermen opposed the idea.

Hydrofoils, especially those used in defence applications, are easily detected by radar due to their higher profile compared to vessels with conventional hulls.

Hydrofoils also cannot manoeuvre alongside other ships because of protruding foils. Overland transport is complicated and special trailers are needed.

Yet with all these constraints, the classic hydrofoil vessels performed exceptionally well.  In 1960 to 1980, craft efficiency had no high priority and power, fuel consumption and CO2 emissions were not yet taken seriously.

Today, with climate change and CO2 reduction requirements, the pressure is on ship designers to optimise hydrofoil vessel design to ensure operating efficiency and low fuel consumption.

Also, the use of electric drive systems requires low power as batteries are very heavy still and guarantee only short ranges.

At the Stellenbosch University, RSA Marine Engineering courses were offered as early as the 1960s. The South African police and navy had requested assistance in the construction of fast patrol boats in the 10- to 15-metre range that could also operate at high speeds in extreme wind and wave conditions with short but very steep waves.

They had imported boats which did not function well and crews had to be retired already at age 40 because of damage to their kidneys and vertebrae.

We looked at offshore race boats and found that the so-called "tunnel boats" (actually split-deep-V-boats with a tunnel between two asymmetrical demi-hulls) performed best in rough sea conditions.  Because of the high deadrise (24 degrees or more), they needed significantly greater engine power compared to monohull vessels.

I proposed to fit a single foil in the tunnel of such a boat at keel height to carry some of the ship's weight more efficiently at speed. The idea was rejected. However, I tried to prove its usefulness and built a small model for towing tank tests.

Using a simple foil design with a good feel for size and profile (K-profiles) and with my experience on hydrofoil tests in the Berlin towing tank years before and also my experience on propeller design, the model was built and tested.

Expecting a 20 per cent resistance reduction, I was surprised by a 40 per cent resistance reduction. This was certainly a welcome development!

My research project at the university was called the Hysucat (hydrofoil-supported catamaran) Development, and many towing tank tests followed. Also, the theoretical development with software development for the design of Hysucat was started.

So, it was found out that the Hysucat mainfoil was considerably more efficient installed and that the interference effect increased the efficiency of hull and foil, as explained in the image below.

In the Hysucat arrangement the mainfoil is attached to the vertical tunnel walls and the foil has no tip vortex.

The foil induced downwash mass flow of hulls, and the foil is much larger than the downflow behind a free foil. The larger the induced downwash is, the more efficient the foil-hull combination will be.

This influence allowed the Hysucat to be considerably more efficient than originally expected.

Later we changed the name to Hysucraft (hydrofoil-supported craft) as we also developed foils for multihulls and even monohulls.

The fundamental design concept for Hysucraft was changed from "hydrofoils" in that the foils would only carry a partial load of the craft and relegate the stability reserves to the remaining portion of the hull that was in contact with the water surface.

So, there were no stability problems with our Hysucraft compared to "conventional" hydrofoils, wherein stability was a major problem. Hysucraft have none of the above design and operational constraints typical with hydrofoils. Further, the foils are smaller, lighter, and thinner – and therefore cheaper.

However, I want to mention two systems which give Hysucraft increased efficiency. The first are surface propeller systems with high OPC values. These propellers create strong uplift forces at the transom in the order of the thrust forces.

This has the effect as if the ship would be lighter which needs lower power. This uplift has to be incorporated in the trim calculations or it requires a certain LCG shift or foil shift.

The other propulsion system is a Servogear adjustable pitch propeller system which has a considerable higher OPC in the lower speed range as the pitch can be reduced for maximum propeller efficiency. This allows it to overcome the hump resistance at Froude number around 0.8 to 1.2 which is especially high when the Hysucraft is heavily loaded.

For extreme high speeds the propeller pitch is increased to deliver very high OPC values. Servogear systems also come with propeller half tunnels that create a significant uplift force, which in turn reduces apparent ship weight.

Hysucats can also be designed to land on sandy beaches and are easily transported on flatbed trailers.

Please compare now the typical hydrofoils with our Hysucraft in the below image, which shows the first 5.6-metre Hysucraft on the water as a manned half-sized sea model.

You can hardly see the small mainfoil amidships and the twin rearfoils for trim stabilisation near the transom. This little boat performed exceptionally well even in extremely rough seas.

We gained the Shell design award for it, a first for Stellenbosch University at the time.

The BMI-Hysucat was tested for a whole year in the sea around the cape and many experts and vessel crews from the navy and private shipping companies were invited. They checked out the Hysucat's performance even in wave conditions that no deep-V-hull vessel owners would dare to run with speed. This was in the 1980s.

Many Hysucats were designed after this in South Africa first and soon after in Germany, Thailand, Australia, the USA, the UK, New Zealand, Brazil, Chile, Argentina, and Hong Kong among others. Including Hysucraft designs that are not our own, there must be several thousands of them on the water worldwide right now!

Ship evaluation method

During the Hysucraft development a tool was required to enable comparison of the ship's efficiency with those of other craft. We already used a method to compare the quality of a foil wing with a planing craft by use of the aeronautical term lift/drag ratio.

In ship building the inverse is used to compare hull qualities, called the Resistance/Displacement ratio ε with R and D in Newtons it gives a dimensionless ratio.

The ship weight is usually given in t = 1000 kg but as a force has to be in newtons: D [N] = D [t] * g [m/s²] with g being acceleration of earth, 9.81 [m/s²].  In Fig. 19 the Resistance over Displacement Ratio ε is shown and tendency curves of various types of ships indicated, including hydrofoils and Hysucraft which give best efficiency for fast craft.

However, to compare the whole ship's or boat's quality their propulsion power Pb [kW] has to be compared.

Pb is in the horizontal direction, whereas D is in a vertical direction and the basic Power:

Pbasic is D [N] * Vs [m/s] = Pbasic [kw]

A dimensionless ratio is achieved by the ratio of:

Pb / Pbasic = Pb / (D [N] * Vs [m/s]) = EPS which  is the equivalent to R/D ratio but by comparison of Powers.

The EPS turned out to be the inversed of the well known Transport Efficiency.

The Froude Displacement number is FnD = Vs [m/s] /

with ∇ [m³]

We determined the EPS ratios of many different ship and boat types and collected them and plotted them over the dimensionless ship speed, (the Froude Displacement number) in the second chart below, which also shows tendency curves of typical ship types.  This gives a good idea how ships compare and for which speeds they are best suited.

We developed the hydrodynamic performance ratio (HPR) by dividing the Froude number by the EPS value, which is called HPR. The HPR indicates a ship's quality by a single number.  The largest number indicates a most efficient craft. The most efficient ships hardly reach a HPR of 30, which would be the most efficient craft seen.

The best hydrofoils reach about 22, USS Tucumcari about 18.3, some hovercraft about 26.3, SES Corsair about 22.54, the demonstrator craft Thunder Child II with 26.176 at top speed and 24.117 at 45 knots cruising speed, and the Alpha Yacht with 28.765 to name a few examples.

The above evaluation method gives every boat owner a tool to find out how well their ship compares to others.

Hydrofoils' HPR data are somewhat disappointing as these might have been adversely influenced by the low OPC data of the propulsion system and by the often-used V-foils. It might have even impeded worldwide hydrofoil craft development. We thus see hydrofoils still used in certain countries but hardly any new developments in recent years.

More recently a Hysucraft hydrofoil system was designed for the 23-metre trimaran Thunder Child II of Safehaven Marine in Cork, Ireland in collaboration with Frank Kowalski.The foils improved Thunder Child II 's performance by nearly 35 per cent.

The World Speed Record Run for boats of 15 metres length or more was then established on August 9, 2020 on the Cork-Fastnet Rock-Cork route with average speed of 45 knots and 53 knots top speed. We are proud of this considerable result together with Frank Kowalski.

I hope that my contributions to the IHS project are well understood and that it dispells the notion of hydrofoils becoming obsolete. Hydrofoils will continue to be developed, maybe just in minor deviations from the traditional hydrofoil designs as the enormous lift-drag ratio of hulls with foils cannot be ignored in marine technology overall.

Already sailing boats are revolutionised by foil assistance and many smaller boats, especially those with electric propulsion systems, are showing improved performance.

I hope that the IHS will continue their valuable efforts and present the technological development of hydrofoil wings to improve popular understanding.

More great content as part of this month's Hydrofoil Week right here.

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Fastest cruising trimaran of all time

Nov 05, 2020

less than a min

A trimaran is also known as a double-outrigger . This is a multihull boat that contains a main larger hull and two small outrigger hulls on the sides. Their design originated from the Philippines and Eastern Indonesia, where they are to this day used as the main fishing boats.

Nowadays, however, trimarans are designed as sailing yachts for racing and recreational purposes, which is why the fastest cruising trimaran is of great interest to the world. It is a fact that trimarans are faster than monohulls or catamarans. As such, their world record has managed to beat any other catamarans’ or monohull prior record.

The record for the fastest cruising trimaran is held by Thomas Coville . He used a trimaran called Sodebo Ultim to sail across the world on Christmas 2016 . HIs trip lasted for 49 days and 3 hours . Thomas Coville’s record beat his predecessor, Francis Joyon, who sailed across the world in a trimaran on the20th of January 2008 on a trip that lasted 57 days and 13 hours. Before them, it was Ellen MacArthur to hold this record after having sailed across the world in February 2005, in a trimaran for 71 days.

The fastest cruising trimaran to this day is the Maxi trimaran IDEC SPORT . This vessel is both wind or mechanically powered and has completed a voyage around the world in 40 days 23 hours 30 minutes 30 seconds. The Maxi trimaran IDEC SPORT can reach an average speed of 26.85 knots or 30.71 MPH .

In addition, this boat has covered a distance of 26,412 nautical miles, or 48,915 km (30,394 mi). In 2020, the Maxi trimaran IDEC SPORT managed to sail from Hong Kong to London in 32 days.

While the Maxi trimaran IDEC SPORT has been established as the fastest cruising trimaran of all time due to the journeys it has completed, there are however a few other boats that have managed to reach more speed. These boats however have not been able to withstand such speed and have capsized.

That is exactly what happened to Hydroptère . Hydroptère is an experimental hydrofoil trimaran. This vessel managed to reach 56.3 knots or 104.3 km/h (64.8 mph) near Fos-sur-Mer. However, it capsized a few minutes after.

Fastest cruising trimarans to have made history

There are many more trimarans that have made history due to their speed. Firstly, the giant trimaran by BMW Oracle Racing team represented the Golden Gate Yacht Club in 2010. This trimaran won the 33rd America’s Cup on Valentine’s day 2010 by sailing off the coast of Spain. It managed to beat the Alinghi catamaran by a large margin.

In addition, the Weta dinghies have started to make a good name for themselves. These are trimarans used for performance day sailing. They are fast, light, and very flexible. Also, these trimarans have been used for disabled sailing. The reason being that you do not need to move around the cockpit to maintain stability when on a Weta Dinghy.

You can compare trimarans with TheBoatDB and figure out for yourself whether they are a good fit for your marina. Do not forget that trimarans in general will require more space when parked. If you are a speed junkie, however, these vessels will definitely appeal to you.

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WindRider RAVE V Hydrofoil Trimaran

The RAVE V from WindRider International is poised to bring high performance foiling to sailors of all abilities. This innovate craft has lightweight, durable composite construction, retractable “V” foils with sonic tubes at the tips to reduce cavitation, an A-frame rig with carbon fiber spars and dual mainsails, and comfortable face-forward seating with foot pedal steering.

The RAVE V is now in pre-production, and WindRider has created a crowdfunding campaign that provides participants with a test sail, deposit on future purchase, or discounted pre-sale on the first production run.

To learn more, visit fundable.com/windrider .

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The $15 Million Fresnel Hydrofoil Trimaran Yacht Is Powered by the Sun and Wind

The seemingly outlandish design is actually being built…, michael verdon, michael verdon's most recent stories.

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The Fresnel Hydrofoil Trimaran might look like a sci-fi writer’s fantasy, but it will soon become a reality for its new South African owners. The futuristic sailboat is the brainchild of Dr. Margot Krasojević, a London-based architect whose career has focused on creating eco-friendly projects that shift existing paradigms. Recent projects include a Canadian prison with its own hydroelectric dam, a coastal home in South Africa powered by the tides, and a water-purifying bridge in Amsterdam.

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The Fresnel (named after a prism lens used to concentrate light in lighthouses) uses a 100 percent green propulsion system that is years beyond the diesel/electric hybrid engines used on some yachts. The sailboat uses solar and wind power to charge the onboard banks of batteries. “We’re aiming for the same speed as if the boat runs on fuel,” says Krasojević. In other words, the owners will gain the same performance without any compromises, not to mention zero emissions and no fuel costs.

Krasojević has essentially created a waterborne perpetual-motion machine. Working with U.K. hydrokinetic engineers and veteran yachtsmen, Krasojević designed a sailing yacht for both long-distance cruising and racing. The carbon-fiber sail—modeled on the fixed-wing sails of recent America’s Cup racing yachts—is more like an aircraft wing than a traditional sail, allowing it to perform well in the lightest of breezes.

When there is no wind, three electric motors (one in each hull) run on the boat’s batteries. Fresnel lenses, solar panels, and holographic film intensify sunlight and channel it to the batteries. “Even the interior of the main cabin is covered with holographic film, which acts as a prismatic concentrator that channels light towards the photovoltaic materials,” says Krasojević. Translation: Every available space is used to charge the batteries.

Beyond long-distance cruising, the owners plan to use the yacht for racing. In trimaran mode, the yacht can reach 40 knots. When the owners want even more speed, the vessel lifts up onto hydrofoils. “This will increase the top speed considerably,” says Krasojević.

In cruising mode, the Fresnel yacht converts to a monohull. On battery power alone, it can cruise at 15 knots. The construction of the high-tech Fresnel Hydrofoil Trimaran is scheduled to begin this summer. It will incorporate the latest lightweight composites throughout the hull. The 115-foot yacht, which should cost nearly $15 million to build, is a one-off project for Krasojević.

But the one-of-a-kind sailboat promises to push yacht design forward. “The goal of this yacht is to use renewable energy every way possible without compromising the design,” Krasojević says. ( margot-krasojevic.squarespace.com )

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Hydrofoiling remote controlled sailing trimaran on test + Video

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TF10 hydrofoils

Ultra-modern, lighter = better, craftsmanship, tf10 hydrofoils - design.

The TF10 hydrofoils are daggerboards in a so-called Z-shape.

The rudders are foils with a T-lifting surface.

The TF10 is a 4-point foiling boat. This configuration ensures that you always sail with all four foils down.

This 4-point line-design has its origin in the DNA F1x. DNA was the first to find a solution to get the A-class upon the foils whilst complying with all special boxrule restrictions for that class.

The design of the TF10 foils comes from Morrelli & Melvin .

We build your new foiling boat!

Material & technology.

Base material: All TF10 hydrofoils are made of carbon pre-preg.

Thanks to our unique ‘one-shot’ production process, we manufacture all our continuous fiber foils under vacuum cured in our Autoclave .

The production method specially developed for this purpose creates a hydrofoil that cures in one go, without glue joints and including internal stiffening ribs. The result is a super-strong hydrofoil that is as light as possible.

All foils are finished with high-quality paint finish. Color of your choice.

Our automated pre-preg cutting machine from the brand Zünd prepares the laminates with high precision. A five-axis milling machine with a working range of 5.5 x 2.5 x 2 meters, moulds the required tooling fully automatically. All this is done in-house.

CHARACTERISTICS TF10 HYDROFOILS

Depth: 3.59 m Widest point: 0.40 m Smallest point: 0.10 m Weight: 45 kg Material: carbon pre-preg

The above specifications refer to the daggerboard foils.

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Electric Candela hydrofoil boat sets world record by crossing Baltic Sea

• September 16, 2024
• 13 comments
• 2 minute read
• Joshua S. Hill

An all-electric hydrofoiling boat from Swedish company Candela has set two new world records by travelling between Stockholm and the Finnish autonomous region of Åland, marking the first time an electric boat has crossed the Baltic Sea.

Candela, which has developed a range of electric hydrofoil boats and ships, wanted to demonstrate that “that zero-emission sea travel is not only possible today, but that foiling electric ships and boats are so much cheaper to operate than fossil-fuelled vessels.”

The record-breaking journey was undertaken in the Candela C-8, a €330,000 ($A544,500) leisure craft, equipped with a battery from technology partner Polestar.

The journey covered 150 nautical miles from the port of Frihamn in Stockholm, Sweden, to Mariehamn, the capital and largest town of the Åland Islands, an autonomous region of Finland, with a charging stop in Kapellskär.

While charging along the trip was made mostly with existing charging infrastructure, a 40kW Kempower Movable Charger was needed in Kapellskär.

Leaving from Frihamn at 6am, the Candela C-8 made it to Mariehamn by lunchtime, and returned to Frihamn the same day.

YouTube : https://www.youtube.com/watch?v=6hFoRF_Q0CA

“The disadvantage of electric boats has been their short range, due to traditional boat hulls consuming so much energy,” said Gustav Hasselskog , the company’s CEO and founder.

“With our hydrofoil technology, we combine high speed and range, but you get so many other benefits. Flying over the Åland Sea in total silence and without slamming was absolutely magical.”

A gasoline-powered chase boat of similar size accompanied the Candela C-8 on the journey and had to be refuelled for a cost of €750, or around $A1,230. For comparison, the Candela C-8 consumed 213 kWh of electricity, at a cost of about €40-50 (around $A66-83).

“We actually had range anxiety, but not for the Candela,” said Gustav Hasselskog.

“The irony is that the photographer’s gasoline-powered chase boat had to refuel six times during the trip, while we only charged three times.

“We’re talking about 95% lower operating costs,” concluded Hasselskog. “This is a revolution that makes waterborne transöport competitive with land transport in terms of costs, which we will now demonstrate in public transport in Stockholm.”

Joshua S. Hill is a Melbourne-based journalist who has been writing about climate change, clean technology, and electric vehicles for over 15 years. He has been reporting on electric vehicles and clean technologies for Renew Economy and The Driven since 2012. His preferred mode of transport is his feet.

We are definitely in an age of disruption, as much as the bashers, critics and cynics like to deny it. Amazing, 1/25th the cost of their ICE partner boat! And quieter, cleaner and calmer too boot!

Google informs me a litre of diesel is € 1.668, so that trip would have used ~450 litres of diesel, or 4,500 kWh. That’s shockingly inefficient.

Unless the ICE partner boat was a similar sized hydrofoil design, it’s comparing apples and oranges. Candela’s own website reckons hydrofoils are up to 80% more efficient than conventional hulled boats, which translates to about 50 litres of fuel.

Please stick to the script. We’re not here to point out inconsistencies. We’re here to deride the people who don’t agree with us. Otherwise, what’s the point of social media?

The point of the voyage WAS demonstrating the efficiency of their hydrofoil design. They used the electric motor to drive home the point.

I’m all for cheaper and cleaner water transöport!

I’ve got a well maintained canoe you could be interested in.

Get back to us when it can cross an ocean. Anyone can cross a sea. Proof of concept can be done with rubber bands, icypole sticks and plastic straws.

Why would a 30 ft leisure craft need to cross the Atlantic? There are currently no 30 ft leisure craft, ICE or otherwise, that can cross the Atlantic.

So it’s not intended to be for mass transport, more of a rich wanker mover? Ok, fine. Plenty of them on here.

Hey JTR that chip on your shoulder just keeps getting bigger.

Ok, partial disclosure. I would buy an EV tomorrow if circumstances allowed me to.. I own a second hand 9yo car with 50k km on the clock.

In 2018, Silent Yachts crossed the Atlantic in one of their solar powered yachts (Silent 64). No stops for charging required!

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Hydrofoil trimaran

Discussion in ' Boat Design ' started by sub_0 , Dec 9, 2015 .

sub_0 Junior Member

Greeting and hello to everyone First of all big thanks in advance for everyone who give they opinion and help on this matter . I m trying to design and build hydrofoil trimaran for school project wich would be powered by internal electric motor . I have some basic knowledge of foilers from Ray Vellinga book also i m on the 5 th year of college and representing myself and my team so we have some background in current topic ....We designed some inicial project with basic caracteristic : -lwl=2.35 m -b=1.75(from ama to ama) -d=0.45 (main hull)-big depth in for different disciplines -Foiler configuration : canard -forward foils : surface piercing-2x position wide abeam on amas -main foils - t foil on rudder -NACA: 63-412 on both forward and aft wings Our goal is to register for internacional competition in three disciplines so our boat must be able to do displacement (or semidispalcement ) transfer of 200 kg and two so to say more speed races on the 200 m track ( rectangular track with sharp 90 deg turn on each corner ) -My question are ? -foils configuration goog/bad(t foil carries cca 70 % weight) -does main t foil needs addicional hight sensor in current configuration with forward surface piercer ( i think not cuz forward foil will change AOI of t foil , and currently we are not planing to put any addicional height sensor) -i was unable to find trimarans foilers WITHOUT sails , also i m concerned about turning manuvers of this ship (shown on pic below) , but i also saw very good flat turns manovers in similar configurations. -in order to find balance beetwen weight transport and spped races our first choice is semidiplacement main hull??(what do u think of this) -ama design -do they need to have same depth as main hull to provide inicial stability when boat is on the rest or they can have smaller depth like on pic below? -ama design -how long they can be in compare to main hull and what cross section do u recomend ? -roll menagment by two forward dihedrals ? *** pic below was made for purpose of marketing *** neglect shape of hulls ***forward foils are going to bi relocated on outer side of amas and on cross bar conecting to main hull ***neglect dimensions between forward and aft foil Big thanks in advance.  

daiquiri Engineering and Design

Hi sub_0, As a first thing, I would suggest you to join the two tips of forward foils and to create one single V-foil canard. The wing tips are a source of vortex drag, so if the competition is about the endurance and max. speed for a given power, you better start removing everything that might create more drag than necessary. The weight will be of critical importance too - which means that materials and construction methods have to be carefully planned. The longitudinal position, spacing and angles of attack of both the main wing and the canard have to be determined through calculation of static and dynamic longitudinal stability, the methods for which are well-established in aeronautical engineering. The roll stability will be determined in the same way. Regarding the design of the hull and the amas, it will depend on the mission requirements. How is the "weight transport" competition defined? Does it require foiling or is it done in displacement mode? What constraints are imposed by the rules? Generally, during the boat acceleration from rest, the hull will be very load-efficient at very low speeds, the foil kicking in above a certain speed (the exact values depending on your hulls shape and displacement). So the analysis has to take into account this trade-off. PM me if you need help in this analysis. Cheers  

Thanks on reply Yes we considered joining front foils due to vortex and strenght problems however we decided to secrifice that . Why ? we are planing on developing flexsible design that will alow us more moving parts in order to correct possible mistakes. Front foils are not join to allow traslation both of amas and foils towards or outwards of main hull . The material will be carbon fibres and since boat has to carry MIN of 20 kg at all time we calculated total mass around 42 kg . Weight trasnport will be without foils. For dynamic analysis we are trying to run numeca , strenght analysis will be conduced using femap . For the main hull we are thinking of choosing semideiplacement hull . Is there any sort of papers or low requirements software (done excel sheets etc. ) for preliminary calculation .  

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The Lotus Theory 1 Concept is 3-seat, 986HP electric monster

The all-new ford ranger plug-in hybrid unveiled in hannover, china is first country to sell over a million electric vehicles in a month, new smart #5 electric suv officially unveiled, candela electric hydrofoil sets world record with international voyage.

A group of Swedes have set a world record by driving an all-electric hydrofoiling Candela C-8 between Stockholm and the Finnish autonomous region of Åland, marking the first time an electric boat has crossed the Baltic Sea and made the journey between the two countries. They even returned the same day – at 95% lower costs than a fossil-fuel-powered boat.

The Stockholm-based tech company has developed the world’s first electric hydrofoil boats and ships, vessels that fly above the water with an 80% reduction in energy consumption compared to traditional ships, providing both long range and high speed on battery power.

The record trip was made in the latest version of the leisure boat Candela C-8, equipped with a Polestar battery , starting at 6 a.m. from Stockholm’s Frihamn. After a charging stop in Kapellskär, they reached Mariehamn, the capital and largest town of the Åland Islands, an autonomous region of Finland, at lunchtime, making it the first electric boat to cross the Baltic Sea between Sweden and Finland.

“The aim was to demonstrate that zero-emission sea travel is not only possible today, but that foiling electric ships and boats are so much cheaper to operate than fossil-fueled vessels. The disadvantage of electric boats has been their short range, due to traditional boat hulls consuming so much energy. With our hydrofoil technology, we combine high speed and range, but you get so many other benefits. Flying over the Åland Sea in total silence and without slamming was absolutely magical,” said Gustav Hasselskog, CEO and founder of  Candela .

The trip was made mostly with the existing charging infrastructure, and in partnership with Kempower, a charging solutions provider. In Kapellskär, the Candela charged with a Kempower Movable Charger, a 40-kW wheeled charger connected to the existing power grid at the harbor. In Finland’s Mariehamn, the boat was plugged into the marina’s three-phase outlet. In the evening at 6 p.m., the electric boat pioneers flew back toward Sweden. After a top up in, Kapellskär, the C-8 returned in dense fog to the starting point, Stockholm’s Frihamn, at 11.30 p.m.

Candela’s hydrofoil technology enables massive cost reductions for sea transport, which was proven when the electric costs were summed up. The gasoline-powered chase boat of similar size that accompanied the trip had to refuel for 750€ during the 150 nautical miles – while the Candela C-8 consumed 213 kWh of electricity, at a cost of about 40-50€.

This fall,  Candela P-12 , the company’s new 30-passenger hydrofoil ferry, will begin operating the Ekerö-Stockholm City Hall route, where it is expected to halve travel times thanks to not producing damaging wakes, allowing it permission to travel quickly in the inner city.

Candela has recently announced a deal to electrify the water transport network in Saudi Arabia’s giant NEOM project , as well as ferries sold to cities ranging from Berlin to  New Zealand .

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The Candela C-8 electric hydrofoil crossed the Baltic Sea within 24 hours and returned to its home port in the same time.

The Candela C-8 on a record run.

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The Swedish boatbuilding company Candela has set a world record by becoming the first electric boat to cross the Baltic Sea in 24 hours with its Candela C-8 electric hydrofoil. The electric boat even managed to return within the same day on Thursday.

The record-breaking boat is the latest version of the Candela C-8 electrified hydrofoil boat, which lifts itself out of the water at a certain speed and then glides over the water on underwater hydrofoils, thereby achieving a high level of energy efficiency. Designed as a leisure boat, the electric vessel was unmodified and used a battery from the Swedish electric car manufacturer Polestar .

The record journey began at 6 a.m. in Frihamn near Stockholm in Sweden. The C-8 reached Mariehamn, the capital of the Åland Islands, an autonomous region of Finland, at around midday.

Before that, however, a loading stop had to be made in Kapellskär. A mobile 40 kW charging station from Kempower was used for this. It was connected to the power grid in the port. At the destination, Mariehamn in Finland, the battery was then charged in the town's marina. A three-phase socket was used for this. In the evening at around 6 p.m., the C-8 set off for Sweden again and reached its home port in Frihamn at 11.30 p.m. in dense fog. Before that, the hydrofoil boat made another loading stop in Kapellskär.

No "range anxiety"

By Candela's own admission, she had no "range anxiety". Three loading stops were enough to cover the distance of around 150 nautical miles. The petrol-powered support boat, on the other hand, had to be refueled six times, resulting in significantly higher operating costs. Gasoline was refueled for a total of 750 euros. In contrast, the C-8's electricity costs for 213 kWh amounted to around 40 to 50 euros.

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Das Video zeigt, wie die Candela C-8 von Schweden nach Finnland die Ostsee überquert.

Candela wanted to use the trip to show that the disadvantage of electric boats, their shorter range, can be compensated for by technology. Conventional boat hulls consume significantly more energy. However, the Candela C-8's hydrofoil technology lifts the hull out of the water, creating less resistance and allowing the boat to travel faster.

Candela has already demonstrated the performance of its C-8 electric boat on several occasions. In 2023, for example, the company set a distance record of 420 nautical miles within 24 hours . Previously, the record had been 79 nautical miles within 20 hours.

Elektro-Schnellboot Voltari 260: Von Florida zu den Bahamas mit einer Ladung

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Croatia’s stunning coastline calls on this nine-day adventure through historic towns and dazzling Adriatic islands. Explore Dubrovnik from every angle — on foot, by kayak, and from a cable car ride to the mountain's peak. Hop on hydrofoils and high-speed catamarans to discover the islands of Korčula and Hvar, then sail by private boat to the Pakleni Islands for a day of walking, swimming, and sun-soaked bliss. Wander Split’s old town and hike to the breathtaking Krka Waterfalls. With a perfect blend of action, culture, and mouthwatering food, Croatia will capture your heart and leave you craving more.

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Back on the mainland, the city of Split is the largest along Croatia's coast, where you'll be immersed in its history and beautiful architecture in the old part of the city. An important maritime transport hub in the region, Split occupies a strategic position on a peninsula that juts out into the Adriatic Sea, and has been inhabited for over 2000 years.

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Immerse yourself in Croatia's natural beauty on a hike through a lush forest, following a river until the sight of a breathtaking waterfall comes into view. Enjoy the moment and the sound of the cascading water before re-entering the forest and allowing the sound of the birds to take over. Back in urban civilization, take in more beautiful architecture and historical landmarks in Sibenik on the way back to Trogir.

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• Your Welcome Moment: Welcome Moment - Meet Your CEO and Group
• Your OMG Day: Korčula Biking or Hiking and Winery Visit, Korčula
• Complimentary arrival transfer
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• Welcome dinner
• Kayaking excursion along Dubrovnik's old city walls
• Cable car ride up Mount Srd
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• Guided walking tour of Hvar town
• Full-day excursion by private boat to the Pakleni Islands
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• Orientation walk in Trogir
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