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Source (all 3 photos) | Composite Advantage Engineering Insights The camel's upper and lower boxes, each about 9.1 ft tall by 25 ft wide by 11.5 ft deep (2.8m by 7.6m by 3.5m), are stacked prior to the addition of the wing walls, each 17.8 ft tall by 5.5 ft wide by 11 ft deep (5.4m by 1.7m by 3.4m), visible at left and foreground. With center boxes and wing walls assembled, the ffth box, the front fender — measuring 18-ft tall by 12-ft wide by 3.5-ft deep (5.5m by 3.7m by 1.1m) — will be attached to the shadowed area on the front of the center boxes. elements; the material and section properties of the plate elements were input manually to match the properties of the composite sandwich panels. Berthing, mooring and lifing (gravity) loads were applied to the model, and the resulting forces were used for panel and connection design. Te submarine berthing energy absorbed by the marine fenders was converted to a force using charts and tables provided by marine fender manufacturers. Te contact points from the camel to the mooring structure were modeled using compressiononly lateral supports. Te panel properties were determined through an extensive testing program developed specifcally for the camel design. For each failure mechanism identifed in the structural analysis, the panel properties from the testing program were compared to the results of the analysis to determine the factor of safety against failure. Reeve says the calculated factors of safety were discussed with the owner, engineer and fabricator to ensure there was a consensus regarding their acceptability. Where possible, the safety factors also were compared to industry standards. For safety factors that were determined to be insufcient, changes to the design or fabrication methods were made as required. compositesworld.com Fabricating For Flotation 48 48 Afer the camel's design was fnalized and manufacturing began, Reeve says another challenge presented itself: buoyancy management. Almost all of a camel rests below waterline, but the composite camels are inherently too buoyant for the application. Te goal, then, was to put the camel's center of gravity as far as possible below the waterline to maintain rotational stability — easier said than done. Reeve says calculating the center of buoyancy and center of gravity included the tedious process of determining the relative position and density of each camel component, including panels, fotation foam, marine fenders and connection angles and hardware. Increasing the ballast weight to achieve the required freeboard, for example, would impact the angle of fotation. Te fnal solution had to achieve a balance among all the design criteria. Ultimately, says Reeve, CA determined that ballast must be added to submerge the camel and keep it trim against the submarine. An assembled submarine berth camel is lowered into the water. Tis is done in three ways. First, afer the 70,000-lb/31,751-kg camel is assembled, 35,000 lb/15,876 kg of concrete is poured into the center box. Second, a series of movable steel plates are installed over the ballast; they are adjusted from side to side in the box afer the camel is foated for the frst time to bring the entire structure trim. Tird, holes are drilled in the box sides to allow them to fll with water. "Te water helps keep the structure stabilized," says Reeve. "It doesn't bob or move as much." CA's frst camel was assembled on site at Naval Submarine Base New London (Groton, Conn.) in October 2010 and installed a month later for a fotation test. Since then, the Navy has installed two more camels, and CA is now manufacturing another for Naval Station Norfolk (Norfolk, Va.). "Feedback from Navy facilities engineers and port operations is very favorable," says CA vice president Andy Lof. "Elimination of recurring maintenance is a major operational beneft, and multiple bases are now looking at the composite camels for future use." Reeve says the Navy is installing about two composite camels per year and is looking at other camel-like applications for the material, despite the fact that the CA camels cost 40 to 50 percent more than the old metal and wood versions. He lauds the unusual foresight: "Te Navy basically said, 'I'd much rather pay a little more up front than pay a lot more over a 10-year period.'" And with camels now expected to last 25 years or longer, the savings will live on. Mission accomplished. | CT | editor-in-chief Jef Sloan, CT's editor-in-chief, has been engaged in plastics- and composites-industry journalism for 20 years. jef@compositesworld.com Read this article online | http://short.compositesworld.com/fU1KgKnR