The boat began in 2016 with a casual remark by Donald Sussman, then owner of the 90‘ (27m) Gunboat catamaran Sunshine, while discussing the prospect of a new boat with his big cat’s captain, Tommy Gonzalez. Sunshine was well suited for ambitious cruising, but they were talking about engaging in the rapidly changing designs and technologies around recreational foiling sailboats. The bird they were planning would be one of that new avian boat species capable of “flying” in air and water, operating above the waves on hydrofoils and, as Sussman now casually said, “Wouldn’t it be great if we could put a wing on it?”
At the time, the word wing signified something impractical and unworkable for a cruising boat—the unwieldy but fragile rigid wing sails used in such vessels as the America’s Cup racers. These were fully rigid structures with articulating control “flaps” like those on the trailing edge of an aircraft wing, and supporting stays attached at roughly two-thirds of their full height. These wings can increase sailing efficiency by a nominal 20%, and therefore are ideal for extreme, sheltered-water racing. Their biggest drawback is that because they can “weathervane” only into headwinds, they can’t be effectively depowered. At greater wind angles they fetch up against their supporting stays and keep sailing. Because they cannot be lowered and furled, rigid wings must be lifted out with a crane and stored in shelter whenever not in use, making them inapplicable to practical seafaring.
However, when Sussman said “wing,” Gonzalez’s mind flashed back to a sketch he had made long before of a special “wing mast” rig. Such rigs normally incorporate a mast having a long teardrop section with the profile of a feather, and with a fabric sail hoisted on its trailing edge. Compared with the usual spar-type rig, where the mast resembles a pole, the wing mast rig is wonderfully efficient because its relatively wide profile smooths the airflow transition between mast and sail. Instead of being a flow-disturbing obstruction like a conventional mast, the wing mast becomes a powerful part of the airfoil. Nevertheless, the usual wing-masted rig, like the fully rigid, solid wing, also conflicts with its rigging. Neither type can weathervane all around to spill winds from all directions. They are like an engine that’s always running—sometimes idling in neutral but at other times in gear and throttled up with nobody on board.
Gonzalez’s wing mast rig idea was for something substantially different and very practical. He knew that somehow it must be made to weathervane into winds from any direction. He discussed the problem with his friend Randy Smyth, and the result was the notion of a wing mast whose cable rigging leads all the way to the very top. There it would attach to a swiveling cap that would not rotate but instead allow the wing mast to rotate beneath it a full 360° without hanging up on its supporting stays. These men knew that the masthead-only standing rigging would create an unprecedented span in the wing, unsupported from cap to step. However, they also knew of the amazing physical properties of unidirectional carbon-fiber laminates (especially in compression, which is essential in spars). They assumed that such a spar, if given generous cross-sectional area, could be successfully engineered with adequate support built into its structure.
To more than double working sail area for efficient performance, a special fabric mainsail would be set on the trailing edge of the spar. When set, this sail would not permit full rotation of the wing, but it could be reefed (needing only one reefpoint); and when downed completely, the soft sail would be totally detached, thereby permitting the wing to freely rotate 360°. They dubbed it the hybrid wing (see Professional BoatBuilder No. 170). It could be depowered and left standing when the boat is unattended or when running in gales at sea. With only three synthetic rigging cables and its superstreamlined shape, this wing would have absolute minimal windage on all points. Gonzalez and Smyth believed in the concept but had no place to apply it until Sussman said, “Wouldn’t it be great if . . .”
Of course, Gonzalez told him about the hybrid wing invention. Seeing it as an opportunity to drive sailing technology, Sussman sold Sunshine and invested in developing the wing and a boat to put it on. Sussman’s patronage convinced Gonzalez to invest his own wherewithal to acquire a first-class boatbuilding facility. He set about recruiting a “mosaic design team” to implement the project (see the sidebar).
Three years later, the upshot of that casual remark is now a firm called Fast Forward Composites (Bristol, Rhode Island), where Gonzalez and his team specialize in advanced products such as sailboat lifting foils, monocoque automobile chassis/bodies, and, after two smaller prototypes and much R&D, boats like Donald Sussman’s fledgling Eagle, the first Eagle Class 53 catamaran.
Eagle was designed by the celebrated naval architect Paul Bieker. He’s a veteran of multiple America’s Cup projects, which explains why this new bird borrows several conceptual ideas from the foiling catamarans of the 2013 and 2017 Cup challenges. Her construction is lightweight prepreg carbon-fiber skins over honeycomb and foam cores, with very specific layup schedules and lots of unidirectional carbon reinforcements, which, according to structural analysis, are arranged to parallel the load paths. All components were vacuum-bagged and post-cured in Fast Forward’s 95‘ (28.9m) telescoping oven. Some parts were autoclaved. These aerospace-derived materials and techniques were implemented by head builder Wolfgang Chamberlain and his team of experienced composite boatwrights.
The above structural elements are not unusual in today’s advanced yacht building, but Eagle’s overall configuration—her eccentric shapes and sizes—exemplify Bieker’s out-of-the-box approach. Relative to “traditional” multihulls, this 53‘ (16.2m) catamaran looks like a 43-footer (13.1m) with an extra 10‘ (3m) of bow. Plus, the bows look like sterns. Instead of the freeboard getting higher and higher toward the prows, it gets lower and lower. When it finally reaches the knifelike stems, the stem angle is reversed, so the hulls are longer at the water than at the deck. Furthermore, there’s really no deck up there. Instead, the upper forebody is sharply crowned, whereas the forward underbody is almost flat—as if the hulls were upside down. Also, the highest point on the freeboard is way aft, and where the transoms abruptly appear, it looks like the builders got that far and ran out of money.
There’s a protuberance, called the pod, beneath the bridge. Almost hidden, it runs lengthwise down the center of the tunnel between the hulls to form a robust structural girder that suggests a vestigial third hull. It obviously supports the bridge deck, but it’s also the mounting point for a long bowsprit where there is no bow and the attachment point for a dolphinstrikerless bobstay that supports the spar. In addition, when retracted into “up” positions, her hydrofoils and rudders tower over the decks like the legs of a tipped-over table. Seeing these deformities, an ordinary wharf rat like me can be excused for not knowing what to make of such a mutant critter. I would learn.
Another first impression is that Eagle is really wide. It’s a long way from one hull to the other, and that not only buys wide-track stability but also buys real estate. The flat-floor bridge deck area, defined by the hulls on the sides and the crossbeams fore and aft, looks about the size of a squash court. In most modern recreational catamarans, that area is entirely enclosed by a sprawling superstructure, but in the Eagle Class 53, the bridge deck is open all around and covered by a large hardtop panel like a hard bimini. This slightly curved platform is mounted on four streamlined pylons, three aft and one forward, with ample headroom to walk beneath. That single pylon forward is also the structural support for the wing, whose step is on the hardtop. This allows the wing to sweep the platform, which serves as an end plate to keep air from escaping and thereby substantially boosts efficiency. Conveniently, the wing and all its running rigging—halyard and sheeting—are confined to the top of the hardtop, out of the way of people on the bridge deck. Steps on the corner pylons facilitate the crew’s access to the wing and the traveler track molded in to the platform structure. All the traveler controls and sheet lines lead into closed chases inside the hardtop. The working ends emerge down on the bridge at the base of the forward pylon and are tended at a cluster of winches mounted on a thigh-high nacelle.
The boat is steered by either of two wheels located far forward and outboard, on either side of the winch nacelle. The helmsman can steer from either the upwind or the downwind side of the vessel with good visibility all around, upward to the wing, and downward between the long bows. This allows the helmsman to observe directly how high the craft is flying on its foils. The helm positions are also within a step and an arm’s reach of all the running rigging and engine controls. In each hull Eagle has a small auxiliary diesel engine fitted to a sail drive, so she can move in calms and, with such a spread between the props, maneuver in tight quarters. Taken all together, this is a neat, compact, and safe control center, which means that (in moderate conditions at least) one pilot can fly this bird.
Also on the bridge deck is seating for as many as eight guests, plus a small island bar. Companion hatches lead below to seamanlike staterooms, one in each hull, both with double bunks and private heads. There is a large fridge and a nice nav station. The entire bridge deck area, including the hatches leading below, can be sheltered with windowed canvas panels suspended from the hardtop.
Gonzalez calls Eagle “the ultimate weekender,” which reveals his intention to build this boat into a class for racing. Actually, her layout is reminiscent of the 1950s cruising philosophy that “the best racing boat is also the best cruising boat,” meaning it had accommodations that were comfortable under way and enough performance (perhaps 10 knots maximum back then) to get where you were going. With the Eagle Class, if there were two couples, or a family of four, who were just knocking around the Caribbean chain, they’d be comfy for a weekend or a week. And, with a boat capable of family cruising on hydrofoils in the 20-to-30-knot range, they can really cover some distance in a brief cruise.
Compounding the unusual looks of Eagle’s configuration is the fact that she is beautifully built. Chamberlain’s team has finished her inside and out like an upscale automobile. As Smyth says, “There’s not a bump on it!” Still, the real beauty of this craft is perceived mainly when she’s under way.
Even without hydrofoiling, those long, low, wave-piercing bows can steer their way right through crests without asking the whole boat to climb over them, bucking and pitching all the way. In rough going, some sailing vessels can resemble a Jeep bounding over boulders, whereas the wave piercers suggest a good horse running on rough ground, its saddle dead steady.
And if the boat is running steady, so is the rig—not inefficiently flailing around in the wind. The air can establish stable flow over both sides of the wing to draw the vessel forward instead of pushing it aside. This yields improved windward ability, deeper reaching, and less stress on the boat (40% less load on the mainsheet), plus a smooth, dry, and quiet ride.
Today’s sailing technology is being driven by innovations above and below the water. The hybrid wing is just one example of the former, and hydrofoils of the latter. While Eagle’s wing is a recent innovation, hydrofoils have appeared on sailing boats since the 1950s and on motorboats much earlier. First regarded by sailors with great suspicion, foils now appear on dinghies, surfboards, sailboards, kiteboards, kiteboats and ’round-the-world racers.
On Eagle, her steady gait and her new aesthetic are highly integrated with her hydrofoils. The full benefits of her hybrid wing and her wave-piercing configuration can be fully realized only when combined with her foils. Fundamentally, her dartlike shape is evolved to get going fast enough to take off, to fly fast on hydrofoils, and then not to slow down too abruptly.
Hydrofoils for sailing have now mutated into alphabet soup. Their configuration, as seen in elevation, is suggested by their alphabetic names. Besides the early ladder foils and dihedral foils, there are now L-foils, J-foils, C-foils, and upside-down “T”-foils. There are even Y- and Z-foils.
Eagle began life sailing on C-foils. With them deployed, she can skim across the water with her upwind hull and its foil flying clear of the water, while keeping her downwind hull levitated but still in contact with the surface to provide some longitudinal stability. In this “semi-foiling” mode, she power-reaches at boat speeds in the high 20s with winds in the mid-teens. When showing off her C-foiling in more wind, she can skip along at boat speeds in the 30s with one hull flying high and the other barely skimming. She has even shown her adolescent spunk by briefly flying both hulls on her Cs, only to be disciplined harshly by her handlers.
Why this restraint? After all, C-foils may look counterintuitive, but they work, and many of today’s racing multihulls fly all hulls on their Cs—but with just the tenuous control afforded by this mode. Indeed, frequent crashes and occasional capsizes can result. Racing sailors accept this risk and train to minimize it, but on the Eagle Class, foiling is not just about racing. Her developers understand that for this technology to take off in the marketplace, it must retain its seductive, magic-carpet-ride quality while becoming user-friendly and safe.
To approach this level of maturity, the boat is going to need T-foils and automated ride control that will allow amateurs to successfully take the helm at 30 knots, and safely depower the boat when conditions become excessive. According to the design brief, such foils should make the Eagle 53 fly flat, stable as a church, with all foils in the water and all hulls out, with crisp control at boat speeds approaching 40 knots.
As of September 2019, Eagle’s T-foils are just beginning to sprout. Gonzalez and his team have been conducting hydrofoil research all along on their 27‘ (8.2m) highly instrumented Stiletto catamaran, which is equipped with articulating T-foils. Data collected will be applied to Eagle’s Ts in the coming year, all with the aim of achieving electronic, fully autonomous ride control. Gonzalez and Chamberlain will speak about foil design and build, and ride control for foilers in technical seminars at this year’s International BoatBuilders’ Exhibition & Conference (IBEX) in Tampa, Florida, the first three days of October. Additional coverage of Eagle’s development will appear in this magazine as the boat matures and the team fully develops her capabilities.
At press time, Eagle, less than a year old, is no longer a fledgling. She has spread her hybrid wing with soaring results, and she has surely learned to skim on her C-foils. Her “takeoff window” opens wide in about 12 knots of wind, just enough to cause whitecaps, and she romps across a tradewind seaway like a flying fish, her downwind hull punching through the crests again and again.
She wintered in the Caribbean, where she showed her stuff to skeptics-turned-admirers, and she playfully embarrassed some other avian watercraft in casual skirmishes. Returning to New England this past summer, she spent some primping time ashore, and she’s been strutting around Newport, Rhode Island waters, where there are flocks of head-turning waterfowl to compare herself to. So far, she seems to have a positive sense of self-worth plus an engaging beauty. For the first time, the black (carbon fiber) “D-spar” portion of her hybrid wing has been painted, and the original transparent Clysar film, which had covered the outrun portion of the wing, has been replaced with durable Oratex fabric (developed for covering bush planes in Alaska). Other plumage also has changed hue, but she’s the same bird gracefully growing up.
By adulthood, she should be a full-on raptor on the race course, but she won’t be alone. There’s a lot of sailing evolution going on these days, and there are surely other mutant hatchlings jumping from the nest. Some of those birds may be nerdier or techier or zingier or even faster than Eagle, but it is unlikely any will be more practical. Besides her engines and accommodations, Eagle has the hybrid wing, which, thanks to its unique ability to rotate 360°, is the first cable-supported, practical wing/sail rig. It is also proving to be a viable technology for seafaring, and it is patented.
Foiling under sail is developing rampantly, and its future in sporting applications seems assured. But what about the future of sailing hydrofoilers in commercial applications? Well, if anything can be learned from the past 70 frenetic years of modern multihull history, it is that building and operating commercial multihulls has been far less financially risky than building and trying to sell recreational multihulls, power and sail.
If that trend holds, it would seem that hydrofoiling on wind power will likely apply to something more than sport, and be driven not just by its speed potential but more for its efficiency. Because commercial operations imply keeping schedule, even when there is little wind, the future foiling challenge becomes how to effectively incorporate auxiliary power (Read our story on contemporary hydrofoiling powerboats). Are foiling under sail and evolving battery technology so efficient that a boat could generate enough energy from its own speed through the water when the wind is up to keep flying when it isn’t? Could the Eagle Class be just one small step toward that goal? Given climate change and the need to conserve energy, perhaps it’s time for us to seriously consider foiling as a practical technology for commercial marine transportation.
The Eagle Class 53 Project Team
Paul Bieker: One of today’s preeminent yacht designers and a sailor since his youth, he received his naval architecture degree with high honors from the University of California at Berkeley. While working on commercial projects, he designed and built successful racing skiffs in the highly competitive International 14 class. This led to designing high-performance composite yachts for some very experienced clients, and to serving as chief structural designer in five America’s Cup campaigns with Oracle Racing. A self-described “careful engineer,” he has been instrumental in bringing CNC manufacturing methods into the construction of high-performance yachts, including Eagle.
Wolfgang Chamberlain: The boatbuilder learned his trade hands-on while working with prestigious yacht builders including Goetz Custom Boats, Carroll Marine, and Hodgdon Yachts. He has been on the build teams of such significant vessels as the 70‘ (21.3m) Il Mostro and the 100‘ (30.5m) Comanche, and he is also a veteran boatbuilder and/or shore team member in five America’s Cup campaigns including two victories with Oracle Team USA. He and his team of composite wizards at Fast Forward Composites have brought in the Eagle Class 53 right at her desired weight, a rare occurrence in developmental yacht building.
Randy Smyth: A dinghy racer since kindergarten and sailmaker since high school, Smyth has, by my accounting, won more sailing races, in a wider variety of vessels, on a more disparate assortment of race courses than any sailor…ever. His career includes six consecutive wins in the Worrell 1,000, three wins in the Everglades Challenge, two Olympic silver medals, one America’s Cup, and a circumnavigation on the 150‘ (45.7m) catamaran Team Adventure. Now a professional racing sail designer, he is a collaborator in the invention of the hybrid wing, a member in the Sailing Hall of Fame, and test pilot of the Eagle.
Tommy Gonzalez: As the Eagle Class 53 project’s true coordinator and overseer, he has sailed more than 150,000 nm on high-performance multihulls. In 2001 he was Team Adventure’s boat captain (115‘/ 35.05m Multiplast built by James Ollier). He was project manager during the construction of the 90′ (27m) carbon fiber Gunboat catamaran Sunshine, and served as her captain from 2010 to 2018. He is founder and president of Fast Forward Composites (Bristol, Rhode Island), where the Eagle was built. Gonzalez: “I’m not a designer, I’m not a boatbuilder, and I’m not really a businessman. I’m a sailor, but I’ve been able to establish a first-class facility, assemble what I call our mosaic design team, and bring a distinguished clientele to the table.”
Manuel Armenanzas is the Design-For-Manufacturing Manager at Fast Forward Composites. Manuel “Manu” is well respected within the America’s Cup community of designers and builders for his meticulous and innovative approach. One of his specialty is constructing foils and appendages. He has 28 years of professional boatbuilding experience and four Amierca’s Cup campaigns, including two victories with Oracle Racing.
Donald Sussman: Forebear and patriarch to the entire Eagle project, he is a financier, a philanthropist, and a sailing aficionado.
Additional essential participants in the project: Renato Calderas, flight control; and Eric Goffrier, interior/exterior design.
About the Author: Jim Brown built and went to sea in the first modern trimaran (an Arthur Piver design) in 1959. He then designed the Searunner series of cruising trimarans, and developed the Constant Camber construction method. He is an accomplished teacher and author, a member of the Cruising World Hall of Fame, and co-founder of the OUTRIG! Project, www.outrigmedia.com.