A hybrid powered catamaran trawler

The Island Pilot DSe (diesel solar electric) 12M Hybrid is a comfortable, moderate speed, cruising power catamaran. This vessel is equipped with a unique hybrid power system that provides a number of advantages when underway and makes it possible to live “on the hook,” enjoying all the boat’s many comforts and conveniences, for days, weeks, or longer without consuming any hydrocarbon fuel.

The power system is comprised of two 75-hp Steyr hybrid-power diesel engines, a 28-panel, 6-kW photovoltaic array (PV), two 48-volt battery banks, two 3.5-kW DC/AC inverters and two shore power operated battery chargers. The IP DSe earns the right to be called a hybrid powered boat from its ability to power the props directly from the diesel engines or using the 7-kW brushless DC motors/5-kW permanent magnet alternators that are built into each engine’s transmission (marine gear). Electrical energy for the motors can be obtained from the PV array, the battery banks or a combination of both sources. Although the boat’s propulsion system fully qualifies as a hybrid, it does not have the ability to recover energy from its motion like a hybrid car, as there is no brake pedal!

The advertising banner for the DSe that was displayed at the October 2008 Fort Lauderdale Boat Show proclaimed, “The First Six Knots Are Free,” a particularly attractive claim with today’s still expensive fuel prices. The claim is supported by the boat’s ability to cruise at up to 6 knots under ideal conditions in smooth water, using only the electrical energy supplied from the PV (solar cell) panels that cover the top of the boat’s deckhouse and pilothouse. The boat can also run for about two hours using electrical energy stored in the boat’s twin, 48-volt battery banks.

The method used to generate electrical power for the DSe is quite different from the conventional, synchronous alternator genset system used on most boats. The permanent magnet alternators that are part of the Steyr engines deliver wild (varying) frequency, varying voltage and AC current. The energy from the alternators is managed by a power-conditioning module that supplies power to charge the 48-volt battery banks. The power-conditioning module also provides the electrical energy used to operate the alternators as brushless DC motors when they are driving the propellers. The boat’s AC power needs are supplied from two 3.5-kW, DC/AC inverters.

When operating in the electrical prop drive mode the permanent magnet alternators function as brushless DC motors. The speed of the motor is determined by the frequency of the AC power supplied by the electronic power control module. The direct current required to power the motor control module can be obtained from the PV system, a battery bank, or from the other engine via its alternator and battery bank.

To sort things out: each prop can be powered from its diesel engine while at the same time each engine’s alternator is delivering energy to its battery bank. Both props can be electrically powered using energy from the PV array, or from their respective battery banks. One prop can be diesel powered while the other prop is powered electrically using energy from its battery bank, or with electrical energy from the operating engine’s alternator/battery bank.

We saw a demonstration of the worth of this cross-feed power source capability when running the boat from the Coral Reef Yacht Club in Coral Gables, Fla., to Port Everglades where the boat was to be displayed at the Fort Lauderdale Yacht Club. As we proceeded north, just offshore in the Atlantic, the port engine began to lose speed due to a clogged primary fuel fiter. Reuben Trane, president of Island Pilot, was at the helm and in a few seconds he shut down the port engine and switched its propeller to electric power drive mode. The starboard engine’s alternator provided electrical power to the port prop while the engine continued to drive its propeller. The cross-feed power option also creates an opportunity to reduce fuel consumption and engine wear/maintenance when cruising at the moderate speeds many of us prefer.

The boat’s propulsion system is managed through a Tecnautic steer-by-wire, power-by-wire helm control. Everything is transparent, movement of the power levers has the identical effect regardless of whether a prop is being turned directly by an engine, or electric motor. The Tecnautic system integrates the boat’s autopilot controls.

Powering the props electrically improves handling of the DSe by providing very high torque at even the lowest possible prop speed (a characteristic of almost all electrical motors). There is immediate response to movements of the power levers. When used in planning hull sport boats the same Steyr diesel-electric engines can operate in an electric-boost mode in which power from the electric motors is used to increase the torque available from the diesel engine, reducing the time required for the boat to get on-plane.

The boat’s accommodations are on three levels, the uppermost, the bridge (we think more accurately called a pilothouse — it’s heated and airconditioned), the deckhouse and within the twin hulls. The pilothouse provides 360° visibility from the twin helm chairs. Seating for guests is provided at a slightly lower height, providing excellent visibility without interfering with the sightline of those at the helm. The seating extends around the sides and aft bulkhead of the pilothouse, with reconfigurable tables to hold the refreshments. Ports and doors provide access to the side decks. The helm station has a Garmin chartplotter at the center, plus a pair of unobtrusive engine monitor panels. Unlike some helm designs, there is no attempt to overwhelm the helmsman with a vast array of rarely used and generally uninformative gauges. The Tecnautic power-by-wire, steer-by-wire and autopilot control is immediately at hand. Based on our experience with the Tecnautic pilot on our boat, steer-by-wire will be the preferred operating method.

The large deckhouse provides the primary accommodation. It is entered via a companionway from the port side of the pilothouse. The galley is aft on the starboard side with the dining and seating area occupying the full width of the deckhouse. The master stateroom, with a centered queen size bed is all the way forward and arranged so that, if you wish, you can lie in bed with your head on the pillows watching the passing scene. The forward master stateroom can be isolated from the remainder of the accommodation with a sliding partition set into the bulkhead.

The guest stateroom is all the way aft, providing excellent and highly valued separation when two couples are on a cruise. The two heads, dressing rooms, storage space, washer/dryer and engine enclosures are in the two hulls, at a level below the deckhouse. The facilities for the master stateroom are in the starboard hull. Those for the guest stateroom and the passage to that space from the main saloon are in the port hull. Being able to get away from others without leaving a boat is a valuable commodity. Overall, we think this to be a very workable arrangement.

The forward deck ahead of the deckhouse provides adequate room for a few deck chairs and a table to hold your wine glass. The catamaran design provides a fine platform when at anchor, resisting the annoying rolling that too often occurs when you are anchored in a quiet cove and someone passes and throws a wake.

The company’s website, www.dsehybid.com contains a great deal of information and videos of the boat’s interior.

The DSe is different; different from most power catamarans and surely different from a monohull trawler such as the Island Pilot 435. With its ability to operate for extended periods of time without consuming fuel and its excellent ability to ignore the wakes of passing boats, it provides an intriguing way to spend long periods afloat.

Florida-based contributing editor Chuck Husick is a sailor, pilot and bicycle fan.

By Ocean Navigator