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www.sname.org/sname/mt underwater vehicles. Maximizing endurance of these types of craft is always a goal and most prototypes to date use composites to create lightweight, hydrodynamic hull forms. e SOLAS Convention and the United States Coast Guard require that ship structure be non-combustible, but Scandinavian shipyards, the United States Navy, and the IMO High-Speed Craft Code have shown through full-scale testing that equivalent levels of re safety can be achieved with composite construction that uses structural re pro- tection. Composite superstructures not only reduce overall ship weight but also improve stability. e National Academy of Sciences recently released a report titled Application of Lightweighting Technology to Military Vehicles, Vessels, and Aircraft.? One of the conclu- sions in the chapter dealing with maritime platforms was that the U.S. needs to take adv antage of its ability to build lightweight, high-speed ferries in order to further the devel- opment and reduce the cost of littoral combat ships. Devices that extract kinetic energy from the ocean, such as wave buoys and tidal turbines, are ideally suited for com- posite construction. e ability to create complex structures that wont corrode in an ocean environment expands the design palette for this emerging eld. Wind turbine blades now measure up to 75 m long and there is talk of 100-m blades for oshore wind platforms. e ability of these composite structures to resist fatigue loading in a maritime environment will pave the way for devices placed in the ocean. Reducing maintenance and manufacturing costs Studies have shown that the annual cost of corrosion to the Department of Defense is more than $20 billion, or 20% of available maintenance budgets. With that in mind, the United States Navy has qualied many composite compo- nents for shipboard use that may not be sexy but do indeed keep the eet in a better state of readiness with less demand from the ships force. Applications include pumps, deck drains, gratings, ladders, ventilation ducts and screens, and stanchions. e navy intends to man its new littoral combat ships with a crew of 40. You will not see sailors on watch chip- ping rust and doing paint touch up, which is common on larger navy ships. Structure and outt needs to be adapted to this environment?both non-corroding and lighter, so one person can do maintenance where it used to take two. Commercial ship owners are also beginning to consider total cost of ownership, which can often oset higher acqui- sition costs associated with composite construction. Many of the exciting applications of marine compos- ites examined here are one-offs, or prototypes, where design considerations were not always cost driven. e true value of composites is realized on the factory oor when numerous copies of the same structure are produced from molds. Computer-aided manufacturing is used in com- posites fabrication in everything from multi-axis routers to create molds, to robots for nishing operations. Large composite structures can be built on-site, thus eliminat- ing factory infrastructure and transportation costs. MT Eric Greene founded Eric Greene Associates, Inc. in 1987 to focus on marine composites. Despite having sank in 2010 following a collision with another vessel, Earthrace holds the record for a powerboat to circumnavigate the globe at just under 61 days, running on 100% biofuel. Built in Auckland, New Zealand, by Calibre Boats, the hull was made from sandwich composites using 40 mm of PVC foam core sandwiched between three layers of carbon inside and out, with a layer of Kevlar for impact resistance on the outside. Photo by Eric Greene. ?s5 ±s ±9x x? Ï ±x ? å IE9 ????, åµEs? Ú åx 9 å Ú Adastra ,,?x?s ±? å Eµ , ?µ å ? ÏE9x?s? Ï?E9 x ?x å Ú ?E Ïs å ±? å 99E´ ±?´ å Ø ´ ås¼ ,Eµ s åxx? ±9 Ï å ?,, üEs5xc April 2013