A French catamaran offers a different approach to power and propulsion
The novel part of the Lagoon 440 is its propulsion system—it’s a diesel-electric hybrid. Twin electric motors, one mounted in each hull, power the boat. They turn the props at 900 to 1,100 rpm at cruise, an ideal speed for efficiency in this size range. Energy for the motors comes from a 22-kW diesel genset which charges a massive storage bank equivalent to twelve 8D-size batteries. (The extra weight of the batteries is compensated for by the lack of two heavy diesel engines mounted near the sterns and by the ability to mount the battery weight closer to the center of the boat.) The batteries are wired in series to give 144 volts. It’s similar to the system in a hybrid car, the genset starts automatically when the batteries need recharging. This happens at 50 percent to 80 percent discharge and is adjustable.
It also has the equivalent of regenerative braking or coasting in a hybrid car. In a hybrid car, braking or coasting downhill puts the motor into generator mode, recharging the batteries. In the Lagoon, sailing in a good breeze makes the props turn the drive shaft as they move through the water, cranking the motors and generating electric current from them. That recharges the battery bank.
It works well on open-ocean passages, not so well in light winds. In strong winds so much current is generated that the control system shut off the motors and stopped the props to prevent overcharging the batteries.
Price: $500,404 for the three-cabin, three-head Owner’s version includes standard diesel engines (electric propulsion system optional), sails, and delivery (but not rigging, launching, or taxes) to East Coast USA.
Builder: Lagoon America, Annapolis, MD; www.lagoon-america.com, 410-280-2368
Designer: Marc Van Peteghem & Vincent Prevost
Construction: Hulls and decks are hand laid and then vacuum-bagged to ensure light weight and complete resin infusion. Hulls are solid fiberglass below the waterline. Closed-cell foam core is used above the waterline to minimize weight and provide extra stiffness. The deck is cored with balsa, and areas where deck hardware attaches are reinforced with solid glass. Rig is aluminum.
Pros: Nearly silent under power, better weight distribution, better fuel economy.
Cons: Only one power source (for electricity and propulsion) instead of the redundancy two separate engines provide.
LOA - 44'8"
LWL - 41'10"
Beam - 25'3"
Draft - 4'3"
Displacement - 23,148 lbs (empty)
Sail Area - 1071 sq ft (main and jib)
Fuel/water/waste - 172/237/50 gals
Power - 22kW genset, 2 Solomon Technologies electric motors
Electrical - 12 8D batteries
Displacement-Length ratio - 162
Sail Area-Displacement ratio - 15 (100% foretriangle)
Resource: Lagoon 440, SailMagazine.com
Cost of fuel really isn't of much concern for owners of this boat. I'm don't think you could justify the cost based on fuel savings, but it could increases the (power) range which is a significant consideration.