s/v Intrepid Demonstrating the advantage of clean power      S/V Intrepid is a unique and truly classic sailing yacht. A modest coastal cruiser launched in 1967 in Bristol RI, s/v Intrepid was the third of 330 Bristol 32 production yachts built and the only one designed by Ted Hood and Dieter Empacher with an experimental custom fin keel. This idea might have been inspired by the 1967 America's Cup race in which Intrepid, the first America's Cup challenger with a fin keel went on to win the Cup twice in a row until she was stopped by Ted Hood on Courageous in 1974. However, the designers at Bristol Yachts must have decided that as a production coastal cruiser, Bristol 32 hull #3 was flawed, since all other Bristol 32s that followed were built with a full keel or full keel with centerboard.    After about 40 years of sailing the east coast of the United States, Bristol 32 hull #3 was discovered on the Internet and shipped halfway around the world to Okinawa, Japan by some completely crazy American guy who fell in love with her classic lines. Here she remains, serving as an ASA sail training vessel and making regular visits to local destinations around Okinawa.		s/v Intrepid has undergone many improvements since arriving in Okinawa, but the most significant upgrade was completed in the summer of 2009. "Project Green Boat" is a project to make a green boat even greener. The project involved replacing the Yanmar 3GM diesel auxiliary engine with an electric motor system produced by Asmo Marine of Denmark.

Before		After
Propelling a boat with an electric motor is not a new idea. In fact, before combustion engines became standard, the earliest power boats were electric powered. One of the first companies to build electric boats, the Electric Launch Company (ELCO) ferried more than a million people around Chicago for the 1893 World's Fair. Around the same time, some of the most notable people in history cruised aboard electric powered yachts, including English nobility and Czar Nicholas II of Russia. Today, the most advanced ships at sea are electric powered, including ocean liners such as the Queen Mary II, and the stealthiest submarines of the world's navies.                Electric propulsion offers many advantages for a small to medium size yacht. Compared to a combustion engine, electric motors offer comparable power but are cleaner, quieter, more efficient and more reliable. Electric motors also produce full torque at low RPM, which enables more precise maneuvering while docking and in tight situations. Electric motors are also lighter. The weight of the system is in the batteries, which can be placed anywhere in the boat to optimize trim and keep the center of gravity low.      At the heart of Project Green Boat, Intrepid's electric auxiliary propulsion system is the Asmo Marine Thoosa 9000. This system uses a 9 Kilowatt LEM-200 motor that runs off a 48 volt battery bank. The system is controlled by an electric motor controller, using a Navitas computer to regulate and monitor the system.		Asmo Marine Thoosa 9000 electric motor       Converting Intrepid to run with an electric motor was a big commitment. Once the engine was removed, Intrepid had to be prepared for a complete refit. All remnants of the previous diesel engine system had to be removed and the boat was thoroughly cleansed of 40 years worth of combustion engine grime and complication. This presented the opportunity to improve the boat in several other ways. Removing the fuel tank allowed for an equal size fresh water tank to be installed in its place, doubling Intrepid's fresh water capacity to 50 gallons. Adding the fresh water tank also allowed the cockpit lockers to be reconfigured to accommodate racks for six extra dive tanks. Making room for the new battery box was also an opportunity to remodel a corner of the cabin and add a navigation table and an electrical system control center.       Converting to electric also simplified and improved the house electrical system. In place of the standard two battery bank system (house and starter) with a relatively light duty 110 amp hour house battery bank, Intrepid now just has one very large house bank with the equivalent of over 800 amp hours of 12 volt power. The electric motor operates on 48 volts, but 12 volt house loads are ran off the same batteries with a 48 volt- 12 volt DC converter.

 

Converting s/v Intrepid to run with an electric motor has involved a fundamental shift in sailing philosophy. This sailing vessel now uses wind power as the primary means of propulsion, with machinery power as an auxiliary method of propulsion... as it was intended. An electric auxiliary motor is ideal for propelling a sailboat in and out of the marina and is capable of propelling the vessel at hull speed for short distances on the open seas. The range under power depends on many factors but is ultimately limited by the ability to charge and store electric power.      s/v Intrepid currently has the largest size batteries that is practical and available economically in Japan (4 x EB160 lead acid / wet cell "cycle service" forklift batteries). Presently, these are charged at the marina from shore power with a 10 amp battery charger. The focus of Phase II of Project Green Boat now is to develop the off-grid charging system, to include solar and wind but most significantly, the hydro generating capability of the Thoosa 9000 system. As designed, the Thoosa 9000 system will generate electric power with the propeller while the vessel is being driven by the wind. This function is currently being tested and more information will be posted to this site soon.		Links                              Project Green Boat design page Aoki Yachts electric boats Asmo Marine Company The Electric Boat Association (UK) Lynch Motor Company Nativitas electric motor controllers Bristol Yachts owners group

Ginowan Marina Okinawa, Japan