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www.sname.org/sname/mt April 2013 70 Durometer o-ring set in groove in keel deadwood structure was used for this purpose. Laminated wood frames are reinforced with bonded G10 berglass plates to satisfy engineering requirements for end xity of the frames. Due to the requirement for a removable deadwood structure and the need for storage under the sole deck, deep aluminum oors were built into the hull structure. Providing end xity to the wood frames via the aluminum oors however presented a small challenge. e oors were designed with side plates to sandwich the ends of the frames and so that through-bolts could make the connection. Analysis of numerous bolt patterns, however, showed that the maximum loads would exceed the woods compressive strength. e problem was solved by bonding intermediate G10 berglass plates to the mating area of the frames in order to harden? the surfaces that mated with the aluminum plates. Using this approach, the moment load is transferred from the frame through the epoxy bond to the G10 plate then through the bolts to the aluminum oor struc- ture. e polar moment of inertia values for all of the odd shapes of both bond areas and bolt patterns were provided by Solidworks software for this stress analysis. Fiberglass/epoxy composite stem structure. e stem structure design enabled the headstay lanyards and bobstay lanyards to be integrated into the same part, which in turn was structurally integrated to the laminated wood hull struc- ture. A 2-in. thick x 8-in. fore and aft epoxy/e-glass laminate is bonded and structurally taped to the stem bulkhead. is part passes thru the deck to carry the headstay and the bob- stay lanyards. Additional reinforcement of the bobstay is by unidirectional e-glass laminated in line with the bobstay and wrapping around the forward edge of the 2-in. berglass plate forward of the bobstay opening and extending aft to cover su cient area of hull planking surface. CNC fabrication of aluminum and composites. Availability of CNC router tooling radically changed the methodology and design process for many parts and assem- blies such as the laminated hardwood beam and frame anges. Replacing the method of lofting and hand tting of loosely t-ting parts, the designers sent model les to CNC to cut precise male and female molds. e resulting laminated parts resulted in tight t ups to similarly cut mating parts in the assemblies. Electric propulsion It was determined that the technology was at hand to pro- vide electric propulsion and bring in energy from the grid to supplement diesel fuel at a cost that could be repaid in an approximately ten-year operating period. e bene ts of this approach include: ? Relatively silent, smooth, and odorless propulsion during the vessels sail charters ? Redundancy of two sail drives located outboard and the independent traditional diesel centerline drivetrain, result- ing in three independent drives of which any one could serve for get home? usage ? Improved dockside handlin g through provision of high torque at low RPM by the port and starboard electric motors ? Ability to pull enough energy from the grid at low demand (evening) recharging schedule to enable docking and undocking operations without diesel engines during typi- cal day sail operations ? Marketing and real bene ts of replacing diesel exhaust with more e cient and cleaner grid energy ? Potential for setting prop RPM to match a preset minimal torque, thus allowing propeller blades to exist in the vessel slipstream without inducing any drag or thrust using neg- ligible energy consumption; this in turn enables the use of xed props, removing the need for low sailing resistance folding or feathering props and their associated expense, maintenance, and dependability issues ( xed props also provide the option of recharging batteries while sailing). Of course, the electric propulsion system turned out to be the most challenging new feature. Su ce it to say that the hours to investigate and engineer the type of motors (axial ux DC), drive mechanism (Volvo Saildrive), battery type (Lithium Iron Phosphate), battery storage locations (almost everywhere), voltage required, and nding help solving the problems associated with charging such a large battery bank far exceeded the most generous estimates. Help came from Hybrid Propulsion Corporation of Portsmouth, New Hampshire. Although electric-powered ships and boats have been around for nearly a century, the combining of modern battery technology and control sys- tems for battery-powered large vessels is new. Before America 2.0, the largest battery-powered sailboat (that we know of) had a maximum power of less than 75 hp. Couple this with the safety requirements of a USCG-inspected vessel and the engineering challenges escalated. America 2.0 s installed EVO axial ? ux DC motor and customized mounting and link plate to commercial SailDrive assembly.