The Efficiency of a Foiling Powercat

Matanzas Watercraft workshop and officeDieter Loibner | Professional BoatBuilder Magazine

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.

Plywood carbon constructionDieter Loibner | Professional BoatBuilder Magazine

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.

Syhoya, an elegant weekender Ian Zelo

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.

passenger accommodation on deckCourtesy Bieker Boats

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.

deck construction with carbon fiberDieter Loibner | Professional BoatBuilder Magazine

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.

moustache foil on cavitation plateCourtesy Bieker Boats

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.”

adjustable J foilCourtesy Bieker Boats

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.

foil setupCourtesy Bieker Boatser

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.

Sidebar

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.

prepreg carbonDieter Loibner | Professional BoatBuilder Magazine

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.

Dieter Loibner | Professional BoatBuilder Magazine

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.

Carbon laminateCourtesy Bieker Boats

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