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www.sname.org/sname/mt April 2013 For most of human history, motive power for commercial trading on the seas was provided by some combination of manual labor and/or sails. The ?rst commercially successful mechanical propulsion systems didnt appear on the scene until the early 19th century (Fultons 1809 river steamer Claremont in America and Henry Bells steamer Comet in 1812 in Scotland). Even with the advent of steam propulsion, sailing ships provided the fastest, most re liable method of crossing the ocean until the opening of the Suez Canal in 1869. Ship speed versus cargo capacity was a frequent debate in sailing ship desi gn, almost always driven by non-technological factors such as macroeconomics, geography, and politics. However, for a brief period in the middle 19th century, technological innovation required a signi?cant improvement in speed under sail. This was the age of the clipper ships. The clipper ship applied two technological inno- vations. One was a ?ner hull form, and the other was a larger sail plan. For centuries, the hull form of commercial sailing ships resembled a cod?sh in plan view on the waterline, with a relativ ely full bow (the cod?sh head) and ?ne run ( the ?shs tail). Clipper ships positioned the maximum section of the hull further aft, allowing a ?ne bow entry. The bow was also stretched out above the load waterline and a counter stern added wate r-plane area and stability when heeled over, enabling greater sail area to be carried compared to conventional ocean-going sailing ships. Some clipper ship designers also argued for ?at bottoms versus sloped bottom s (deadrise). However, this factor didnt prove to be a signi?cant determinant of speed. Extreme clippers? were distinguished from medium clippers? by how ?ne the hull lines were and the cargo carrying cap acity of the ship for a given overall length. Clipper ships generally had a square rig with three or more masts. Square sails were carried on all masts if it was a full- rig ship, and fore-and-aft e most critical issue in the hybrid powerplant is safely dealing with high voltage (DC) on a boat. An obvious ques- tion is Why not lower the voltage?? Providing enough power for a sixty-ton vessel would require wire the size of a re hose at a safe 48-volt level, so we do the second best thing. e 480-volt battery is broken into safe 48 volt packs. Each of these is protected by a vacuum relay and a variety of safety interlocks. Touch anything and theres no more than a safe 48 volts within wrench range. Also, per ABYC proposed high voltage standards, the battery is ungrounded. Typically it sits at +240vdc or so and -240vdc. All other systems are isolated from the high voltage, and the high voltage power is carried only on armored cables with high-tech impedance measure- ment of the cable insulation to determine a ground fault. Another major engineering issue?one occasionally in the headlines because of electric cars and boats catching re?is the issue of battery management. To get the high volt- ages that the motors need, the battery consists of hundreds of individual batteries or cells in series. When these cells are charged together from a high-volta ge source, they need to be very precisely balanced or the cell with the most charge will dramatically increase in voltage and heat up. Even with a total battery thats almost depleted, an out-of-balance cell can immediately increase in voltage and temperature to the point of boiling o a lead-acid battery or melting a lithium cell. e battery management system from Hybrid Propulsion maintains a history of the maximum and minimum voltage of every cell and is the only commercially available BMS system that can balance lithium cells of more than 1,000 amp- hours. is is the system employed on the 112-cell battery in America 2.0 , and it provides more than 100 kilowatt-hours of total power storage. All motor controls, power electronics and throttles have redundant electronics. Low-level control is provided by Programmable Logic Controllers (PLCs), which communi- cate with a custom computer system, provided by Hybrid Propulsion, which enables all functions to be monitored and controlled by a remote web page or iPad. e PLCs also can monitor power usage and automatically shed non-critical loads and turn on the generator when required. In the middle of the project, the decision was made to change from AGM batteries to LiFePO4 lithium batter- ies. Although each battery costs twice as much, the total cost for the power required is lower because the LiFePO4 cells can be used 100%, while lead-acid cannot be safely discharged lower than 50%. is higher capacity, coupled with the ten-times-greater life expectancy of lithium, made the decision easy. To enable an earlier startup of the vessels commercial activities, the vessel was initially put into operation with sin- gle-screw traditional diesel propulsion in September 2011. At this point, the electric hybrid system is in the nal assembly stage. Debugging and commis sioning should be complete before the boat returns from its Key West service to its sum- mer operating waters in New York City. Scarano and Classic Harbor Lines have always found that providing an exceptional experience to their char- ter customers is very good for business. A key piece of this is a fast, nimble, well-performing, and beautiful boat. e high performance features examined here are demanded by the current commercial, regulatory, and environmen- tally aware social climate in which the vessel operates. MT John Scarano is president and co-owner of Scarano Boat Building, Inc. www.sname.org/sname/mt April 2013 SPEED UNDER SAIL: The Clipper Ship Era By Jay Carson