Electric Foiling Catamaran from Recycled Parts

Scavenging parts and gear, a boatbuilder in the San Juan Islands creates an electric foiling catamaran for his private milk run.


Gizmo foilingDieter Loibner | Professional BoatBuilder Magazine

Retired boatbuilder Chris Maas, demonstrates Gizmo, his purely experimental electric foiling cat that he designed for his weekly shopping trip to Lopez Island. The boat consists of mostly recycled and repurposed parts and materials.

Following our two-part story about fiberglass disposal—or the lack thereof—for end-of-life boats (Professional BoatBuilder Nos. 189 and190), we are looking in more depth into the practicalities of building something entirely new from gear and material discarded by previous owners. To illustrate the possibilities that a reduce-reuse-recycle approach can bring about, I made the trek to Center Island, Washington, to meet with Chris Maas, 64, who, as he looks back on a successful boatbuilding career, has the freedom to try out intriguing ideas on boats he builds just for fun.

Never one to seek the limelight, Maas is not a household name in the international boatbuilding industry, so let’s start with a short introduction. Hailing from Seattle, Washington, he started messing with boats as a kid, graduating to OK Dinghies, Lasers, and Finns as soon as he was strong enough. He also worked on other people’s boats, repaired them, built rudders and daggerboards, did anything to pay for his racing habit. That’s how it was back in the heyday of the fiberglass revolution that delivered recreational boating to millions of average wage earners. With some talent and the will to work and learn, you could make a living in this industry while also having fun.

Dieter Loibner | Professional BoatBuilder Magazine

In Maas’s island workshop, Gizmo dangles from the rafters between farm equipment and Ariel, an International One-Design sloop awaiting restoration. The foiler’s cockpit sled accommodates the battery box, the steering station, and the passenger/cargo area and extends well forward of the main foil.

The Road to Building an Electric Foiling Cat

Maas always seemed willing to look beyond his nose and the task at hand to sample different boats as he accumulated skills and experience. At some point he helped 1984 Olympic Gold medalist Bill Buchan build fiberglass Starboats and a cold-molded 3/4 tonner that they raced to victory in the Swiftsure International Yacht Race and a second-place finish in the 1978 3/4-Ton Worlds. At age 19, living in a waterfront shack on Vashon Island, he also built a 37-footer (11.28m) to his own design, and through a friend became interested in building open-water rowing shells. It’s the job he ended up doing for more than 20 years with his own outfit, Maas Boat Company (www.maasboats.com), which he started in 1978 in California and sold in 2001. After that, Maas designed and built International Canoes, and won a World Championship in 2011 to go with two runner-up finishes in 2014 and 2017. Semiretired now and living on a small and somewhat remote rock not served by the Washington State Ferry, Maas relies on an outboard-powered aluminum skiff as a utility and commuter vehicle, a simple and rugged craft that does the job but has little to offer in terms of refinement, efficiency, and joy.

Electric Foiling Cat bank turnDieter Loibner | Professional BoatBuilder Magazine

With the main foil painted white for better visibility, Maas banks Gizmo into a starboard turn, showing off the boat’s agility. With all-manual controls, it’s not fly-by-wire but fly-by-seat-of-your-pants.

The project he shared with us is Gizmo, a craft he developed repurposing a well-used Hobie Cat 18 (5.51m), a former rental boat that was advertised for $200 on Center Island’s community bulletin board. Old and beat up as it was, it made a suitable platform for what Maas had in mind: a fully foiling commuter with electric propulsion that he and his wife, Monique, could use for their 5-mile (8-km) round trip to Lopez Island to buy groceries, look after property, or visit Maas’s brother Alex, who retired from making carbon fiber tiller extensions with his company ACME.

“As I’ve gotten older and seen how many resources I used to build my boats through the years, it’s a little bit appalling,” he told me about his evolution from builder to rebuilder. “So philosophically, I’m coming around to the idea that there’s a lot of good equipment out there, either just languishing in somebody’s basement or backyard or going to the dump at some point.” As a former racer and stickler for clean and functional boats, Maas doesn’t skimp on quality or performance, so he scavenges for the good stuff, which takes skill, patience, and a few good friends.

The original idea, he said, was to equip a dory with an electric outboard that runs on a solar-charged battery. But a ride on an outboard-powered and foil-assisted 24’ (7.3m) catamaran built and designed by Brandon Davis of Turn Point Design for Nigel Oswald in Friday Harbor, Washington (see “From Niche to Market,” PBB No. 173, page 36), pointed him toward a multihull platform. It also helped that at some point Maas designed and built International Moth dinghies, so he wasn’t new to the game of foiling, and that he is on good terms with America’s Cup–proven designer Paul Bieker, who’d moved to the Anacortes, Washington, neighborhood a couple of years ago.

Foil Design, Construction, and Control

“I did have a basic design in mind before I started talking to Paul,” Maas remembered. “He came around in one of his little high-performance powerboats…and we started talking about foiling. I was telling him my ideas, and he said, ‘Oh, that sounds like fun. I’ll help you with some of the design work.’” Aside from foiling America’s Cup sailing catamarans and International foiling Moths, Bieker has been working with local public-transport authorities on fast-ferries and is involved in the design of a fully foiling passenger ferry (see “A Foiling Ferry for Puget Sound,” PBB No. 191, page 12).

Roll control, all-important for a stable foiling performance, can be achieved by several means in fully immersed foils. One method is flexing and twisting foils with foot-pedal-controlled ailerons, which Maas used on the Hobie. Bieker then worked up an asymmetrical section shape from a Moth foil he had developed, and the layup schedule. It had to work well at the modest speeds (under 20 knots) at which the boat was going to be run.

Foil profileDieter Loibner | Professional BoatBuilder Magazine

The asymmetrical section shape of the main foil is close to a NACA 63-214 profile. Maas built the foil with a solid Douglas-fir core, covered with 15 layers of 200-g/m2 (5.9-oz/sq-yd) standard-modulus unidirectional carbon fiber and one of ±45° plain-weave carbon cloth.

The shape of the main foil is close to a NACA 63-214 profile and was modified from Bieker’s original dimensions by Maas to give the flaps on the trailing edge at the wingtips more authority in roll control. The foil now measures 244cm (96”) span, 20cm (7.9”) chord, 28mm (1.1”) thickness. The flaps are 25% of the chord and 40cm (15.75”) long. The vertical struts are Eppler E836 hydrofoils with a maximum thickness of 25mm (0.98”) at 42.8% chord. All foils used on Gizmo were molded in female MDF molds, but for the main foil, Maas used a simple solid-fir core he covered with 15 layers of standard-modulus 200-gm2 (5.9-oz/sq-yd) unidirectional carbon fiber and one layer of ±45° plain-weave cloth carbon on the outside—all surplus from Boeing.

Built in two halves that he machined flat on his 3-axis CNC router (a converted surplus CNC fabric cutter from Boeing), they then were bonded to each other in the molds with ProSet LAM 125/226 epoxy, initially cured at room temperature and post-cured at 140˚F (60˚C) for eight hours after being removed from the mold. For the aft foil, Maas repurposed a Moth main foil with an MH 32 airfoil’s profile, a piece of gear he’d kept in his shop after selling a Moth he’d built for himself to participate in a World Championship in Hawaii. That foil is made from solid unidirectional intermediate-modulus carbon with a layer of ±45° in the outer skin and has a flap that takes up 30% of the chord length.

Lower Unit with Moth FoilDieter Loibner | Professional BoatBuilder Magazine

Only slightly resembling its earlier gasoline-burning incarnation, the modified outboard shows the PMAC electric motor, the 18.1″ (46cm) shaft extension, and the wand-controlled Moth foil that carries the smaller portion of the load while foiling.

Both the main foil and the outboard foil are controlled by surface-sensing wands connected to pushrods made from his brother’s surplus carbon fiber tiller extensions. The wands are built from old carbon fiber windsurfer battens with attached pieces of PVC sewer pipe as paddles to keep the end of the wands at the water surface. Gizmo’s ride height is determined by the relative angle of the wand to the water surface, just as on International Moth dinghies. However, while the forward wands perform as a single unit to adjust the main foil, the trailing wand of the outboard foil moves only the flap of the repurposed Moth foil. Initially, Maas had to crawl forward onto the bow to adjust the takeoff angle of the main foil depending on payload, but he later modified controls so he could make these adjustments from the cockpit.

Foil control mechanismDieter Loibner | Professional BoatBuilder Magazine

The line-controlled paddle wand mechanism automatically adjusts the foil’s angle of attack.

There are more-elegant solutions for sure, but on an experimental boat that small and simple, electronic ride control is not a viable option, adding too much weight, complexity, and expense. Besides, as a competitive sailor, Maas loves hands-on operation, so he made sure all mechanical controls and electronic instruments are within easy reach of the driver’s seat in the cockpit, which looks like an amalgam of a powerboat’s and a sailing dinghy’s setup. Sitting in a forward position, about halfway between the bow and the forward crossbeam, the pilot must keep Gizmo properly trimmed and “in flight.” True to Maas’s pedigree as a racing sailor, he made sure the lines, sheaves, and cleats are properly sized for the job and lined up to minimize friction, which is essential for smooth and precise operation.

Sparse as it might look, nothing is missing. To port there’s the GPS readout, the hoisting line for the main foil, and the cleats for the ride-height adjustment lines that lead to a threaded spool that changes the articulation setting of the sensing wand and, by extension, the main foil’s angle of attack (AOA). The ailerons are operated by lines connected to the foot pedals under the steering wheel. On the starboard side there’s the forward-reverse toggle, tachometer, power kill switch, throttle, a battery-charge display, the battery management system with a screen displaying the state of charge and temperature of each battery cell, and two cleats for the lines that deploy (pull down) the main foil. Maas wanted to keep Gizmo on a float for quick launching and to avoid the need for toxic bottom paint. To achieve that, the main foil had to be retractable. Bieker came up with a solution to drastically reduce draft and mitigate potential damage from an accidental log strike. However, it’s under patent review, so images and a discussion of details will have to wait.

Gizmo CockpitDieter Loibner | Professional BoatBuilder Magazine

The cockpit arrangement is simple but sufficient, with few instruments, a power kill switch with spiral cable to the pilot’s wrist, and cam cleats for foil control.

The sled’s structure serves as a kind of “fuselage,” with the battery compartment all the way forward, followed by the cockpit, a tandem seat for one passenger, and the cargo area. “It’s just ¼” ACX fir plywood from the lumberyard with a couple of coats of WEST System 105 epoxy,” Maas explained. “That’s super basic. It’s not the most elegant material, but it’s sort of a local product, and it’s cheap and reasonably strong and light enough for my purposes.”

A Drowned Gas Outboard and Chevy Bolt Batteries

He could have bought an off-the-shelf electric outboard, but Maas wanted to stay true to his recycling mantra and got his hands on a 15-hp (11.25-kW) Tohatsu gasoline outboard that by misfortune ended up at the bottom of Fisherman’s Bay on Lopez Island. It’s one of those loopy Lopez tales that starts with a silly mistake and ends with an exchange that makes seller and buyer happy. “A friend of mine knows the owner [of that motor],” Maas said. “I had told him that I was looking for a motor and within a couple of weeks, this guy dropped his motor in the water. It was clearly meant to be. It’s a pretty good fit. My ideal motor would have probably been a 20-hp [15-kW] with a hydraulic tilt-and-trim mechanism as a way to control the foil angle, but that did not materialize. So, I had to take what I could find.”

Battery Box and CockpitDieter Loibner | Professional BoatBuilder Magazine

The battery box is located forward of the steering console and the PVC piping that protects the electric cables

After going by the board, this two-cylinder Tohatsu was salvaged, but never properly flushed, so the innards corroded, turning it into a hunk of scrap metal. But Maas didn’t care, because he was going to replace the combustion engine with a 10-kW permanent-magnet AC (PMAC) motor before extending the shaft by 18.1” (46cm) and attaching a 9.25” x 11”  (23.49cm x 27.94cm) prop to suit his purpose.

Chevy BatteriesDieter Loibner | Professional BoatBuilder Magazine

The surplus Chevy Bolt lithium-ion batteries were sourced at
www.batteryhookup .com

Maas explains how he turned a rusted gasoline outboard into a working electric specimen, not exactly a common exercise: “I began by removing the powerhead and cutting the bottom section off to use as a base for the motor mount plate. That plate is 1/2”-thick [13mm] aluminum with a vertical bracket welded on to serve as the mount for the controller and controller heat sink. The spline coupler from the gas engine crankshaft was cut off and machined to weld into a Lovejoy coupler that fits the electric motor shaft. This way I can use the existing gas engine driveshaft with its probably proprietary splined end. That shaft was cut and extended 18” [0.46m]. The now longer shaft is supported by a midshaft Cutless bearing, which, because it is above the water when foiling, is lubricated by a small stream of water through a tube connected to the old cooling-water pickup [the old water pump was removed].

Electrified Tohatsu OutboardDieter Loibner | Professional BoatBuilder Magazine

Aircooled Motenergy 10-kW permanent magnet motor with heat sink.

An extension housing was made for the shaft by molding a carbon/foam part using a NACA 0012 section. The outboard cover needed to be widened a bit to fit the new motor (a 10-kW Motenergy ME1012 PMAC) and a Sevcon Gen4 controller. It also had to accommodate the bilge blower pressed into service as a cooling fan, a speed controller for the fan, because it turned out that the motor doesn’t need that much cooling and a slower-turning fan is much quieter, and a 72VDC-to-12VDC converter for running lower-voltage components.

The outboard is mounted to a pivoting aluminum bracket held down by a line to a cam cleat on a base that can pivot and release in the event of a log strike.

Keeping the recycling theme going, Maas also found two 12-kWh Li-ion batteries destined for service in a Chevy Bolt electric car but ended up as rejects because some mounting holes in the battery were drilled wrong. He got them really cheap online, serialized them, and fit them in a watertight compartment all the way forward on the sled, where they were out of the way and help trim the boat.

The Electric Foiling Cat’s Sea Trials

Maas and others like him don’t think in problems but in solutions. They are capable of tackling any job and come up with results that make mere mortals blush with envy. “If I can imagine it, I can make it,” as master fabricator Ed Louchard once said. What master craftsmen like Maas and Louchard might lack in formal technical training, they more than make up by learning on the job, developing intimate knowledge about materials and tolerances, and honing their ability to improvise before empirically testing the stuff they made to see if it holds up. In building Gizmo, Maas didn’t produce lavish computer renderings or run computational fluid dynamics programs. He relied on hand-drawn sketches on the workbench. Backed up by decades of experience and asking the right questions, he took incremental steps to develop his solutions, tried them, tweaked them, and then tried again. While not on par with computer simulations and analysis used in modern manufacturing, it’s that sort of old-fashioned engineering that helped him build the boat he envisioned.

Draft Sketch of CanopyDieter Loibner | Professional BoatBuilder Magazine

As the consummate empiricist, Maas roughs out ideas in sketches before they take shape in his workshop. Shown here is the concept for the canopy.

“It depends on what you call sea trials,” he quipped in response to the question about how exactly he built Gizmo as close to the bleeding edge as possible without digital modeling. “In-water testing began with a 15-hp gas outboard bolted to the Hobie and some plastic drums filled with water strapped to the deck to see how much power it would take to [achieve] foiling takeoff speed. After that, I built a main foil to Paul’s design, [fastened] a Moth main foil to the defunct Tohatsu outboard, and had a friend tow me around with his powerboat while we took speed and drag measurements [as I] tried to figure out how to control roll and ride height. Basically, it was a long series of major changes and adjustments that eventually started to taper off as I ran out of changes that needed to be made, and things actually started to function in the proper way.”

During my second visit in September 2020, Maas demoed Gizmo right off his dock and put on a display of suave foiling action, including crisp takeoffs, silky-smooth landings, and precise banked turns. As if running on rails, this old Hobie never looked better, and the skipper was ostensibly enjoying the occasion. He was kind enough to accommodate my request for a ride, which added about 190 lbs (86 kg) to the payload.

Sea TrialsDieter Loibner | Professional BoatBuilder Magazine

Taking Gizmo for a spin during the sea trials, Maas tested different ideas and setups before finishing the cockpit and enclosing it with a canopy.

As we throttled up the first time, Gizmo took off on a steep trajectory immediately leading to a decidedly unsmooth landing. Unperturbed, Maas clambered out onto the port bow to add some tension to the bungee that keeps the main foil, which controls lift, from over-rotating and stalling on takeoff (as mentioned earlier, these adjustments are now made from the cockpit). At slow speeds, the center of lift is forward of the pivot point, which makes the foil rotate to a higher AOA. With increasing speed, the center of lift moves aft, which keeps Gizmo in balance. With more weight on board, the bungee gets overpowered on takeoff, so the foil rotates too much, thus causing the stall. After these tweaks, the takeoff was flawless, and the boat quickly settled into level trim, running steady, stable, and quiet, emission-free circles on Reads Bay.

After putting in some test miles, Maas also added a canopy made of 1/4” ACX fir plywood strengthened with a layer of 180 g/m2 of S-glass/epoxy. The windshield is 1/8” (3mm) tempered glass, and the side windows are 1/8” acrylic, which adds roughly 100 lbs (45 kg) to the vessel’s weight but extends usability deep into the cool and damp season. It might not be the most fashionable accessory ever seen on a boat, but it protects pilot, passenger, pooch, and payload when the Maases go on their weekly shopping expedition to Lopez. The test ride my wife and I took that following summer was memorable for the lack of drama. With her on the green plastic garden chair facing aft, me under the semi-closed canopy behind captain Maas—who worked the controls —pulling the line to adjust the trailing wand, which controls the angle of the outboard’s foil—Gizmo smoothly took off, barely hitting double digits, while gently foiling from Hunter Bay past Cayou and Ram Island to her dock at Center Island.

Air BubblesDieter Loibner | Professional BoatBuilder Magazine

A streak of bubbles emanating from the starboard forward foil might come from air sucked through the hollow Eppler foil of the vertical strut. Maas plans to close that cavity with a foam plug.

Port Townsend boatbuilder Russell Brown, himself a prodigious recycler and reuser of discarded boat parts and kit (see “Outside the Box,” PBB No. 130, page 52), had a similar experience when going for a joyride. “It’s almost free power for 12 knots,” he noted. “The way [Maas] can control it with the foot pedals and the steering wheel is pretty cool. He can make it bank any way he wants to. I love the feeling…inside the canopy when you take off. It’s like taking off in a small plane.”

The Electric Foiling Cat’s Performance

I asked Maas about Gizmo’s limits and his observations of what this craft can and can’t do. “We tested in up to 18 knots of wind speed and approximately 40cm [1.3’] wave height,” he said. “It handled well, though the wands contouring the waves produce a kind of bouncy motion if there’s much chop—like driving over a bumpy road in a vehicle that has really good suspension.”

Gizmo’s lightship displacement came in at 990 lbs (450 kg). Maximum payload is 550 lbs (250 kg), including the pilot. Takeoff speed (light) is 8.5 knots, which draws 9 kW. Cruising speed is 12 knots at 5.8 kW. Without foils, Gizmo manages 8.5 knots at the same power draw, which constitutes a 30% reduction of efficiency. Currently, GPS-recorded top speed (foiling) is 16 knots at 10 kW. And finally, Maas claimed a maximum runtime of two hours at cruising speed before he has to return to the dock and plug in.

To get to higher speeds, he said he’d have to go beyond trying a few off-the-shelf props. “I understand prop design basics but don’t have enough knowledge to design my own,” he said. He likes higher-aspect blades, perhaps pitched for lower rpm, but that would necessitate further surgery to the outboard’s lower unit to fit any large-diameter props.

“Oh, I guess I’m probably a borderline hoarder, and the only reason it hasn’t become a terrible problem is because…it’s really hard to get things over here [to Center Island].” He laughed when asked about the most important skill for building a new boat from old kit. “I’m kind of a scavenger. I actually have to foresee the use for stuff that comes over here,” Maas said at the end. “I’m fairly frugal and pretty tight with my money. And so, you know, I’m always looking for a deal.”

Aft view of CanopyDieter Loibner | Professional BoatBuilder Magazine

Leaving a zig-zag trail of foam, Maas demonstrates Gizmo’s maneuverability on foils. Note the aft-facing green-plastic lawn chair, plain but adequate passenger seating.

And that is precisely what he got. Compared to the Swedish Candela electric foiling runabouts (see “From Niche to Market,” PBB No. 173, page 34) with carbon hulls, giant batteries, and fly-by-wire controls, Gizmo struck me as the nautical equivalent of the Brothers Grimm tale about the Valiant Little Tailor, who has the guile and ingenuity to take on a giant and become king. While the latest 28’ Candela C8 is listed in the U.S. for $350,000, Maas spent a tiny fraction of that, did some sleuthing for cheap parts, and worked an estimated 500 hours in his shop to get a custom electric foiling boat. Maas also emphasized that Gizmo was an experimental project, not an endorsement of his approach to copy without following applicable standards, regulations, and best practices.

However, when all was said and done, he’d used almost exclusively cast-off or surplus parts to produce a tidy craft that serves its purpose while also offering a glimpse at the possibilities that a circular economic model promises: Reimagining design, manufacturing, and product life cycles could go a long way toward reducing waste and making better use of scarce resources. Not to mention cutting carbon emissions when running a boat purely for fun.

Contact: gizmofoiler@nullgmail.com

About the Author: Dieter Loibner is editor-at-large of Professional BoatBuilder.