catamaran on foil

Yachting World

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

• Matthew Sheahan
• August 6, 2019

Is this the future of sailing? The Eagle Class 53 is a wingmasted cruising catamaran designed to fly on T-foils

Not everything that flies is destined to scorch around an America’s Cup course. The future for sailing hydrofoils is surely about more than just racing. At least, that was the view of one owner who, having witnessed the America’s Cup foiling catamarans, saw a big opportunity.

“I’ve worked as a skipper for yacht owner Donald Sussman for 16 years,” says Tommy Gonzalez. “When he saw the foiling Cup boats he knew that this was what he wanted to have a go at. He is not interested in racing himself, he wanted to go cruising, but cruising on foils. He saw what had been created and believed that this had practical potential. Put simply he said: ‘I want one and I want to be the first.’”

As well as being a professional skipper, Gonzalez is the president of Fast Forward Composites, a Rhode Island-based composite building facility where the Eagle Class 53 was constructed. Understandably, the road to creating such an ambitious cruiser was never going to be straightforward. So the plan was structured around several key elements and stages, starting with an efficient and easily managed wingmast.

The hybrid solid wing and soft sail configuration means the rotating rig can be reefed. The entire solid wing can be rotated through 360° ensuring the rig can always be fully depowered – important for docking and close quarters manoeuvring

Of those two criteria, efficiency is easy to satisfy – wingmasts are by definition more efficient. It is the practicalities of handling them that usually causes problems. Reducing sail in breezy conditions and leaving the wing up at the dock are two of the biggest issues.

The solution on the Eagle Class 53 was to create a composite wingmast where 50% of the area is a solid D-section and the trailing 50% a soft sail that can be raised, lowered and reefed. Interestingly, it is a similar concept to that of the next generation of 75ft foiling monohull Cup boats, currently under development. “The rig is a little lighter than a conventional mast and sail set up, and significantly easier to handle,” explains Gonzalez.

“Because the sail can be raised or lowered we can reef the main, or even just sail with the solid section. The mainsheet loads are around 40% less than a conventional rig and because the sail can turn 360° we can let the wingmast fully rotate, which makes life simple when you’re docking. You just let it feather.

“In addition, because we have a part soft sail, which we have developed with North Sails, we can create twist which allows us to de-power the top of the sail, so we have plenty of control over this wing and the advantages that go with it.”

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The next stage was to work towards foiling. To do this the team decided to create a cat that had C-section daggerboards that would help reduce displacement at speed but not lift the boat entirely. Getting used to controlling the power and feeling the behaviour of the boat through various wind ranges and sea states would provide a solid understanding of the boat’s characteristics.

“Once we have got used to the way the boat handles, the next stage will be to fit T-foil rudders which will take us onto the next level,” continues Gonzalez. “With these we will be able to get used to the software system, the instrument displays and the feel and the control of that part of the programme without taking the boat to full flight.

“That will allow us to get her up on her toes like a ballerina and keep her there so we understand what she feels like before she flies. “After that, in the spring next year, we’ll remove the C-foils, put on the T-foil daggerboards with their elevators, and move on to full foiling.”

The wingmast has a solid D-section and trailing soft sail

The proposed T-foil daggerboards will be angled out which makes the overall platform slightly wider, which in turn makes for more stable and efficient foils. And while improving the efficiency of the lifting surfaces, the outward bend in the daggerboards will also help to generate more righting moment, and hence achieve greater stability.

The control system itself will be a form of fly-by-wire system that will allow autonomous flight to ensure that the boat sails within safe operating limits. “If you have some of the gods of sailing aboard you will be able to override the controls to some degree, but under normal circumstances the control system will automatically de-power and lower the boat back into the water when the speed gets to 35 knots,” he explains.

So far the project has gone well. After the boat was launched earlier this year she cruised in the Caribbean during the regatta season before heading north back to Bristol, Rhode Island. “We’ve been very pleased with how well the boat sails and how easy she is to handle,” said Gonzalez.

“When we’re on delivery trips we have just three aboard. Aside from myself, the other two crew are not highly qualified professional sailors and yet we are looking at boat speeds of around 15-18 knots upwind and then 22 knots off the wind.

“We have also been through a squall of 35 knots where we were sailing with just the D-section of the wing mast which was easy to control by feathering the wing. When we get to the foiling stage we anticipate that we will be able to fly in around 10 knots true.”

The Eagle Class 53’s roots lie firmly with the foiling America’s Cup catamarans. Even in displacement mode she’s an exhilarating ride. The goal is to achieve fully foiling performance

It is still early days for a project that Gonzalez describes as being “crawling before walking, before running and ultimately sprinting”, once the hydrofoils are fitted.

Yet during the development process it has become clear that there are others who are interested in the 53-footer, whether it foils or not. So, while the next big goal is to work towards building a 75-80ft long distance cruiser, currently called the 8X, interest in the Eagle Class 53 has been sufficient for the company to tool up for a limited production run.

“We have created carbon tooling for the 53 and are looking to build around seven of them,” said Gonzalez. “For the 8X, we are hoping to build three with the first being available during the winter of 2021-22.”

Gonzalez is a realist when it comes to the future. “As we all know, foiling has been around for a long time in military and public transportation, so we need to set an example to insurance companies and the likes that we are foiling safely and encourage others to follow. But the time has come. This is part of the evolution of our sport.”

Specification

LOA: 16.50m (54ft 2in) LWL: 16.08m (52ft 9in) Beam: 8.50m (27ft 11in) Draught: 0.41m-3.05m (1ft 4in-10ft 0in) Displacement (light ship): 6,000kg (13,228lb) Displacement (max load): 7,540kg (16,623lb)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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The efficiency of a foiling powercat.

By Dieter Loibner , Mar 13, 2020

Matanzas Watercraft’s founder, Jan Brandt, in his office with a rendering on the wall and the prototype of the Matanzas 29 foiling powercat peeking through the shop door.

Motivated by his own boating experience and America’s Cup foiling technology, a startup builder launches the Matanzas 29, a new breed of powercat for fishing and cruising.

Wherever Jan Brandt goes, a constant companion since his childhood days in Hamburg, Germany, is his passion for watersports. Competitive swimming, surfing, waterskiing, fishing, scuba diving, sailing, you name it, he’s done it—and still does. No surprise, then, that Brandt is also deeply involved with boats, not just using them but also designing and building them. His latest project is a 29 ‘ (8.8m) foil-assisted planing cruising power catamaran designed for twin outboards from 60 hp to 90 hp. Last fall, construction was far advanced as Brandt prepped for finishing, outfitting, and getting the boat ready for sea trials off St. Augustine, Florida, where he set up shop as Matanzas Watercraft LLC.

Inspired by the Sliver 29, a catamaran designed for fishing and weekending, built by SuperCat in South Africa , Brandt defined specifications that suited his own use patterns and his home port in St. Augustine. “I am looking to build a day-use cat for fishing offshore waters but also capable enough to make the run to Bimini and Abacos on a calm summer morning,” his design brief reads. Also on the list: sufficient load capacity for three to four people for day use and provisions for a couple to cruise for a few days; a range of 200 nm on one tank; and a cruising speed of 20 to 25 knots. Brandt: “I need to deal with a 2–3 ‘ [0.6m–0.9m] chop and Atlantic Ocean swells. While an open cockpit with center console and hardtop is totally sufficient, a head and dry storage for gear with maybe just enough space for a bunk for two would be awesome.” Since crab or lobster pot buoys are not much of a concern in Florida, Brandt explored the idea of foil assist to reduce power requirements and improve seakeeping. However, he was adamant about the ability to safely beach the cat and limit overall beam to 9.1 ‘ (3m) to keep the trailering permits manageable.

The Matanzas 29 plywood/carbon prototype has wave-piercing bows with a positive rake and peaked decks that shed water quickly. The bows’ fine entry flattens out toward the stern to encourage planing, even when operating without foils.

He did some preliminary design work himself, but when the project got serious he consulted with Bieker Boats of Anacortes, Washington. Principal Paul Bieker served as the lead designer of the Oracle America ’s Cup sailing team and was instrumental in developing the outrageously fast 72 ‘ (22m) foiling catamarans that ushered in a foiling revolution following the 2013 Cup on San Francisco Bay. Bieker now applies variations of the foiling concept to pleasure craft, most recently with an innovative 53 ‘ (16m) sailing catamaran intended for racing and weekend cruising (see “ Fledging the Eagle ,” Professional BoatBuilder No. 182) and now with Brandt’s foiling powercat.

The basic idea behind foiling is maximizing efficiency while curbing the need for big engines, a notion that has yet to find footing with production boatbuilders. Brandt: “I’m not interested in boats over 25 ‘ [7.6 m] running 250- or 300-hp twin motors. I’ve been doodling around for a year on the idea, spent more time on the hullform, and when I decided to pull the trigger on building one, that’s when I contacted Paul to help me finalize the design, incorporate some of the design criteria and requirements, and make it work from an engineering perspective. He helped crystallize the hull shape and get the details fleshed out.”

Foiling Tech Trickle-Down

A former racing sailor who campaigned a Mini 650, Brandt met Bieker in 2010 while cruising the waters of Puget Sound. He ran his own environmental consulting firm in Seattle and also took up boatbuilding. First came stitch-and-glue kayaks, but soon he graduated to the PT Skiff, an 18′ (5.5m) kit boat by Port Townsend Watercraft designed by Bieker and Russell Brown. With Brown’s encouragement Brandt designed and built the cedar-strip carbon composite Syhoya , a handsome 21 ‘ (6.4m) weekend cruiser powered by a 60-hp Evinrude E-Tec outboard for cruising Puget Sound and beyond.

Previously, Brandt designed and built Syhoya, a 21’ (6.4m) weekender with a 60-hp outboard for cruising the  coastal waters of the Pacific Northwest.

In Brandt’s painstakingly clean and organized workshop a 10-minute drive from his house in St. Augustine Beach, Bieker’s plans laid out on the workbench and the prototype of the Matanzas 29 under construction showed how personal predilection, boating experience, and exposure to innovative design ideas informed his choices. For a simple boat that aims to maximize efficiency and minimize power requirements, the design process was complicated. Some salient features, like the combination of planing hulls with wave-piercing bows and the foil arrangement most commonly associated with fast sailing cats, seem a bit counterintuitive at first, but Brandt explained the underlying thinking.

He wanted to minimize the fatigue of the acceleration/deceleration forces when running the steep chop of St. Augustine Inlet during an outgoing tide, “letting the bows do the work,” rather than endure slamming, Brandt explained. “That’s when we combined the wave-piercing hulls with the foil assist in order to get away from larger engines while still being able to carry the displacement we need, all the things we added that were part of my criteria—the fish boxes and the scuba gear. All that weighs quite a bit, [but we wanted] to manage that with reasonably small motors. That’s how we got to wave-piercing bows and the foils.” Load-carrying capacity, especially at speed, is another reason he decided against displacement hulls.

Passengers can ride on the main deck, under the hardtop, or on the “rumble seat” forward.

Why plywood/composite instead of carbon-reinforced plastic construction, which would have further minimized weight? Brandt reasoned it was less complex and costly for a prototype that has to establish proof of concept and test the nascent market for foiling powerboats. Tooling up for a production run is his goal. The thin plywood—okoume 6mm/1⁄4 “ for the topsides, 9mm/0.35 “ for the bottom—is sheathed in E-glass, a laminate schedule of 200-g (5.9-oz) and 300-g (8.95-oz) layers inside and out. Turn Point Design in Port Town­s­end cut the kit, based on design files it received from Bieker Boats. “That worked perfectly. We have had zero issues with the wood fit,” Brandt recalled. “Every puzzle joint fit the first time.” For the foam-core portions of the boat, he used 20mm (0.79 “ ) Divinycell H80 sandwiched between multiple layers of regular-modulus carbon woven roving of 5.9 oz 0°/90°, and 2×2 twill weave of the same weight, which conforms well to complex 3D shapes. For taping and to reinforce high-load areas, Brandt applied 400 g/m2 (11.8 oz/sq yd) of 45° double biaxial carbon and 9 oz/sq yd (305 g/m2) unidirectionals.

The entire wet deck, measuring 18 ‘ x 10 ‘ (5.49m x 3.05m), was vacuum-bagged with the foam core and three layers of carbon fiber on each side, laid up in various directions. That’s a large piece to build in a compact workspace, so he tackled it first and then stored it against the wall to make room for hull construction. Florida’s warm, humid climate imposes its own demands on working with resins, which ideally are catalyzed and processed in an ambient temperature around 65°F (17°C). Brandt planned to get the big parts done during the cooler time of year, turning on the air-conditioning if necessary and starting at 3 a.m. Doing “the large areas of the hull, we had three layers of glass on the bottom, so running that over 30′ [9.14m] in one shot, even just hand layup, gets challenging, because the initial pot cures before you have the last layer on.” That’s a herculean task for one, but he had help from his wife, Tonya, and then hired some neighborhood kids to do some sanding.

This angle shows the square sterns, the cutouts for the fuel hoses and steering lines, the carbon-reinforced main deck, and the storage boxes.

In addition to all this new construction, Brandt still found opportunities to include some repurposed parts from his Mini 650, which he had raced from Newport to Bermuda and in West Coast regattas. In his stash of spare kit was an extra boom—a 3.7m (11.15 ‘ ) raw carbon tube from CST Composites that always traveled with the boat. It became the beam that holds the anchor roller and forms the front terminus of the foredeck, Brandt noted, adding that he cut and fit sections of carbon spinnaker poles to support the cat’s hardtop.

Outboards with Mustache Foils

As originally conceived, the boat was to be powered by twin 60-hp Suzuki DF 60A three-cylinder outboards. However, working with technicians at Suzuki Marine of North America , which rents shop space from him next door, Brandt opted for the four-cylinder DF 90A, which he considered a better fit for the prototype’s offshore work and for testing the custom mustache foils. Granted, the DF 90A packs 50% more power and a third more weight than a DF 60A, but it’s still modest compared to twin 300s often seen on boats of similar size.

Custom-designed carbon mustache foils on the cavitation plate will boost stern lift as their attitude is adjusted by the tilt and trim mechanisms of the outboards.

“I don’t need 55 knots; 25 is awesome. That’s fast cruising,” he declared. “Every now and then…it’s nice to be in the 30s to run home, but that’s plenty.” If it sounds extreme, Bieker wanted even less. “I think he was initially uncomfortable with the speeds I wanted, until we had a discussion about what the market expects,” Brandt laughed. “The mentality is ‘I gotta be able to go 30, gotta be able to outrun a thunderstorm. I’ve got 40 or 50 miles to the Gulf Stream, and I want to get there in reasonable time.’ Paul’s sweet spot is 15, 16 knots, because you can do that with a lot less power. To go from 16 to 22 knots is a big jump, but 16 knots is not where the market is; it’s not where the utility of the boat is. So I had to push the area of power where he was less comfortable and the threshold of where he did not want to be associated with. That was a big compromise. I credit him for coming my way.”

Outward-facing J-foils forward carry most of the displacement when deployed. Their angle of attack is manually adjustable by ±2° with a sliding bolt, and hinge pins allow the foils to fold up when not in use.

The production of the mustache foils (named after their shape) was outsourced to Chris Maas on Center Island, Washington, a former builder of custom rowing shells and International Sailing Canoes. He said he was using his 3-axis CNC router to machine molds from MDF board and construct the foils in wet layup with Pro-Set epoxy. These foils will be mounted to the cavitation plate, so any adjustment in the angle of attack comes from the outboards’ tilt and trim mechanisms. The main appendages amidships are outward-facing J-foils (similar to those on the 31 ‘ /9.45m Foiler by Enata Marine; see PBB No. 173, pages 39–40). A hinge pin at their heads allows them to fold up when not in use, while the angle of attack is adjusted manually when the boat is stopped, by slacking two bolts and sliding the hinge mechanism fore and aft for a range of ±2°.

“We lofted all the layers carefully,” Bieker said of the foil construction that was performed by Simon Miles, a carbon fiber fabricator in Port Townsend. “We came to 167 layers,” Bieker continued. “Typically we get to within 1mm of the target shape. The structural spar is solid, and toward the trailing edge there’s some hi-temp PVC foam core.” It will be done in five to six cooks at 250°F/121°C (see the sidebar below).

In foiling mode the cat will not be in “full flight” with hulls clear of the water but rather skimming along the surface. As simple and sensibly powered as the boat is, Brandt still wants the capacity to carry a payload of approximately 1,600 lbs (725 kg) for fuel (2 x 35 gal/132.5 l), water (14 gal/53 l) food, paddle, and surfboards, fishing, and scuba gear, a porta-potti, some electronics, and a small refrigerator. To cover his energy needs for starting and house loads, he’ll go with 2 x 75-Ah lead-acid batteries with 650-amp cold-cranking capacity. Two 100-watt solar panels on the hardtop and intermittent charging from the alternators when motoring should keep the lights on and the beer cold.

Deck, stern, and side views reveal the arrangement of the boat with foils deployed and folded up. Note the mustache foils mounted to the cavitation plates of the outboards to increase lift and help trim the boat.

Brandt named his company Matanzas Watercraft after the river that runs past St. Augustine, where he attended high school after emigrating from Germany with his family in the 1980s. Dating back to those days, he knows the surf spots, gnarly riptides, and choppy patches where sea breeze and ebb collide. After dialing in the new boat during sea trials, which include a trip to the Bahamas to test it as a cruising, fishing, and diving platform, he hopes this America ’s Cup–inspired concept will generate the interest that warrants a limited production run. Ideal customers, Brandt reckoned, are sailors who share his passion for water sports, value his high-tech approach to efficiency, and “don’t necessarily need the power that generally is the norm in the market.” It’s a bold bet but one that seems right for the times. “The intent is there, and we have the facilities to do it,” he added.

Dieter Loibner is editor-at-large of Professional BoatBuilder.

Cooking the Foils

While Jan Brandt of Mantanzas Watercraft was putting the finishing touches on his Matanzas 29  powercat in St. Augustine, Florida, the foils were being made at the diagonally opposite corner of the lower 48, in Port Townsend, Washington, roughly 2,500 miles (4,023 km) distant. Working inside his barn workshop that used to house a boatbuilding shop called Seven Seas, carbon fiber technician Simon Miles, 31, stood next to the carbon tool he’d built for the job. He was warming swatches of prepreg with a heat gun to help them stick to the adhesive film he had previously put on top of the cured substrate of the first cook.

Simon Miles heats the prepreg to bond it to an adhesive film he put down onto cured substrate in the foil mold.

Having worked for Oracle’s America ’s Cup team and Mad Fiber, a Seattle company that made high-end carbon racing wheels, Miles is very much at home with high-end carbon work, but this job was new territory, because it required high-temperature tooling, and he was using a new source for the intermediate-modulus prepreg required.

The tooling was built from a plug of machined medium-density fiberboard (MDF). The monolithic carbon mold is infused with Pro-Set High-Temp infusion resin using Sigmatex 660 g/m2 (19.5 oz/sq ft) of 2 x 2 twill, a ply of 200-g/m2 (5.9-oz/sq-ft) woven carbon, and two coats of Pro-Set High-Temp tooling putty against the machine-tool-face end to limit print-through of the heavy woven cloth.

Infusion of the carbon tool.

The centerpiece of the foil project is a 20 ‘ -long (6.1m) shipping container the previous owner converted into a giant oven for constructing high-end carbon fiber parts. “It has Roxul insulation and stainless walls inside,” Miles explained, “and there is a huge heater/blower unit from Electroheat.” For this project, Miles moved the container/oven into his workshop and hooked it up to three-phase power.

To help lower the cost, Miles sourced 108 yd of 190-g/m2 (5.6-oz/sq-ft) unidirectional 250 prepreg from Composite Recycling Technology Center (CRTC) in Port Angeles, Washington. The material was rejected for use in aerospace applications, hence the substantial savings. At CRTC it was stored at 0°F (–17.8°C), which is common for prepreg. Once out of the freezer it must be processed quickly, but the cool ambient temperatures of the Pacific Northwest winter (at or below 50°F/10°C) allowed Miles enough time to complete the work.

Some complexities: The foils, designed by Bieker Boats, comprise 167 layers of carbon laminate, 144 of them unidirectional 0°, the rest off-axis plies (±45°). In the lower part of the foil, the structure will include foam core (Divinycell H100 foam) and Gurit SE 84 laminates. Miles said he planned to switch to the lower-temperature prepreg so the foam does not “blow up.” At 250°F (121°C) H100 distorts, changing density and dimensions, but SE 84 cures below that threshold at a cooler 176°F (80°C). Miles said he would still precook the Divinycell to reduce the chances of expansion after the foam had been shaped. To finish, he will use woven cloth for wrapping, and SE 84 as well. Lastly, the B-side will be faired and sanded.

Miles estimated total construction time would run eight weeks for a springtime delivery.

Dieter Loibner

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How SailGP’s foiling F50 catamarans sail so much faster than the wind

Arguably the most technologically advanced sailboats on the planet right now, the one-design SailGP F50 foiling catamarans are capable of breathtaking speeds – at times, reaching four times the velocity of the wind that drives them. But how do they do it?

Beating the balloon

Bending the laws of physics

Faster and faster

Beneath The Surface

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Meet the denmark sailgp team, find all the latest news, go beneath the surface of sailgp, sailing terms, go beneath the surface.

How the world’s fastest sail racing boats fly above the water

Tune in to SailGP’s landmark Season 2 opener in Bermuda at the end of the month, and you’d be forgiven for thinking that your eyes are deceiving you.

The Beneath The Surface show

We go Beneath The Surface of SailGP's iconic host cities, set a spotlight on great projects and curious mind and catch all the lastest with the Denmark SailGP Team. Join us as we travel the world and explore how innovation and science is helping solve the world's biggest challenges!

This is how SailGP's NASA-inspired wings make the F50 boats fly

Some may say the foils, which help the boats to fly above the water. Others may claim it’s the platform – that’s the two, catamaran hulls and the trampoline that connects them.

ROCKWOOL Denmark SailGP Team

The official home of the ROCKWOOL Denmark SailGP Team. Meet the team, read all the latest stories and explore a world of exciting content.

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Improved Efficiency with Hydro Glide Foil System™

The Aquila Hydro Glide Foil System™, designed by catamaran and foil specialists Morrelli & Melvin Design & Engineering, is available as an option on the extremely popular Aquila 36 Sport  as well as the Aquila 42 Yacht . It enhances the performance, consumption, and handling of the already spectacular performance of these two power catamarans. For the Aquila 36 Sport, the hydro-glide foil improves miles per gallon by 40% when compared to a competitor's 36' power catamaran and decreases the fuel consumption rate by 37%. 

As reviewed by Boating Magazine: “It’s hard to believe that a piece of metal with no moving parts can be the approximate equivalent of adding 200 horsepower, 100 gallons of fuel, and 100 miles of extra range.” But, that’s what happens when the Aquila Hydro Glide Foil System is attached between the two hulls. 

Improved Boat Efficiency | Aquila Hydro Glide Foil System™

An In-Depth Look at the Hydro Glide Foil

How the Hydro Glide Foil Came to Be

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Hydrofoils: Boats That Fly

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

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

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

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

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

The Science

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

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

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

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

Experience Hydrofoiling For Yourself

Hydrofoil kiteboards.

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

Hydrofoil Waterskis

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

Hydrofoil Windsurfers

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

Hydrofoiling Small Sailboats

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

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

Foiling The Competition

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

The America's Cup Class AC75 Boat Concept Revealed

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

The America's Cup AC75 Boat Concept Revealed

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

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

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

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

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

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Charles Fort

Contributing Editor, BoatUS Magazine

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

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40 Foil-Assisted Catamaran

Typical specifications.

LOA: 40’ BOA: 14’

For detailed specifications, contact us today.

The “Flying Hub II” shown here is a 40-foot custom welded-aluminum passenger vessel designed by Jutson Marine Design and built by Metal Shark for a Florida-based fishing and tour boat operator. This innovative vessel features a highly efficient foil-assisted catamaran hull and has been built to USCG Subchapter T standards.

Hull Design

Deck Layout

40 Foil-Assisted Catamaran Image Gallery