Belafonte: An Eco-Friendly Hybrid Day-Tour Power Catamaran

The story of the hybrid day-tour catamaran Belafonte begins with another boat: the 57-foot power catamaran Reef Express. Reef Express runs snorkeling and sightseeing trips out of Key West, Florida, and it led to a collaboration among designer Dave Walworth, builder Joe Kitchell and an owner with a specific eco-tour concept.

The owner operates small passenger boats for day excursions and wanted a purpose-built vessel to run two short trips daily: one to watch inshore dolphins near Key West, and a second to carry passengers to a mooring or anchoring area for snorkeling. He asked Walworth to design the boat and Kitchell to build it to suit this itinerary and to market the trips as eco-tours—so hybrid propulsion became a major consideration.

“Electric power has the torque and quiet operation, but limited range,” Walworth explains. For short, frequent runs that spend extended time drifting or moving slowly while observing wildlife, the trade-offs made sense. The result is Belafonte, a 35-foot, 20-passenger power catamaran being built by Kitchell Composites in California using epoxy resin infusion. It is believed to be the first Coast Guard–inspected near-coastal vessel certified to carry more than six passengers while using electric propulsion.

Belafonte will be driven by Torqeedo Deep Blue 40 electric motors—one in each hull—powered primarily by BMW i3 lithium-ion batteries. A diesel generator is carried for charging and extended range. The combination is designed to provide a cruising speed near 14 knots when needed, while allowing very low-speed, nearly silent operation for wildlife viewing and snorkeling operations.

Bringing large lithium-ion battery banks into a Coast Guard–inspected passenger boat introduced new regulatory and engineering challenges. “There aren’t already written rules for this exact setup,” Kitchell says. Because the regulations were developed for conventional diesel systems, the team had to work with regulators on protective measures such as a stainless-steel enclosure around the batteries and custom control and breaker arrangements to meet inspection requirements.

Despite those hurdles, the fuel- and emissions-saving benefits are compelling. Walworth estimates Belafonte will consume as little as three gallons of diesel per 3½-hour tour under ideal conditions—perhaps up to six gallons on a busy day. For two trips a day, that could mean roughly 12 gallons total, a dramatic reduction compared with conventional propulsion systems used on comparable passenger boats.

The planned operating profile takes advantage of the hybrid setup: use the generator and battery power to reach the dolphin-watching zone, then run almost silently on electric propulsion while following dolphins and slowing to near idle without stalling. Between the dolphin watch and the snorkeling stop, the crew can provide safety briefings while passengers enjoy a quiet trip. While passengers snorkel at the mooring, the generator can recharge the battery pack so the boat returns to port with the batteries largely discharged and ready for an overnight recharge.

Redundancy is built into the system: each battery bank and the generator can independently drive the vessel, so a single component failure won’t strand the boat. A modest array of solar panels on the cabin top—about 2 kilowatts—will supplement charging. On sunny days the solar contribution might provide roughly a third of one battery’s capacity, and at very low speeds could add enough power for extremely slow, quiet maneuvering.

Weight and efficiency were priorities, which is why Kitchell chose epoxy resin infusion for construction. Epoxy infusion produces a strong, lightweight hull by drawing epoxy resin through dry-laid core and reinforcement materials inside a sealed mold under vacuum. The technique reduces material waste, produces consistent laminate quality and lowers labor requirements. Kitchell has refined the method over decades and credits it with delivering substantial fuel savings for previous tourist vessels—allowing running routes that would otherwise be uneconomical for light passenger loads.

“With epoxy infusion we can make a very light, durable hull at an affordable cost,” Kitchell says. He estimates the process can cut weight and related fuel costs significantly versus traditional methods while remaining cost-effective compared with other ultra-lightbuilding techniques.

For both designer and builder, Belafonte represents a learning curve. It’s Kitchell’s first all-electric build and Walworth’s first electric design, though both have experience with multihulls and modern composite construction. Walworth notes parallels with his off-grid home on St. Croix, which relies on solar panels and battery storage: advances in battery technology and system controls are making electric propulsion increasingly viable for the right commercial and recreational uses.

Walworth and Kitchell believe hybrid electric power is a growing opportunity in the powerboat market when matched to appropriate use cases—short, repeat runs with long idle or low-speed segments, such as eco-tours, harbor cruises and other near-coastal operations. As battery energy density improves, generator runtime will decline and electric systems will become even more attractive.

Kitchell welcomes the engineering challenge and the potential for broader adoption. “We’re setting precedent, so it’s taking time,” he says. He also envisions adapting the design and construction methods to other molds and sizes, and believes the approach will help electric propulsion make a major inroad into commercial powerboats when owners and operators find the right fit.

This article originally appeared in the June 2018 issue.