CompositesWorld
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47 CompositesWorld.com the motor bolt locations: "Tose engines can move, and start to loosen bolts over time. Tis solution keeps water out and further limits any movement." Tese extra materials notwithstanding, the single-skin transom design weighed 227 kg less than a conven- tional cored sandwich solution, says Bergstrom. For the hull laminate and transom, the team selected three plies of bidirectional knit glass fabric, supplied by Composites One (Arlington Heights, IL, US), and CoREZYN vinyl ester resin from Interplastic Corp. (St. Paul, MN, US). With the gel coat, also from Interplastic, and an epoxy barrier coat, the total laminate thickness would be ~12.5 mm. Te Prisma MEGAFORM preform beams range in height from 50 mm to 1.2m, and up to 5m long, with plies of unidirectional glass fabric applied to the tops of the larger beams that support the sole. Several aramid plies are lami- nated along the Prisma keel beam, for abrasion resistance. Cascading benefts Te hull and transom are hand layed at HydraSports Custom's Vonore, TN, US, facility, and cured at room temperature (above 21°C) for 6-8 hours, depending on tempera- ture and humidity. Bergstrom says resin infusion might be employed in the future. Assembled boats are then shipped to the Islamorada, FL, US, facility for testing. A "factory boat," one of the frst vessels built, is taken out every week on long runs for durability testing. "On one trip," he says, "we were moving fast and came over the top of a big wave, and dropped. Te accelerometers we had installed in the Single-skin, Uncored Hull Technology boat showed a total impact of about 15G. Tere was no gel coat cracking or any damage at all. Te design is really robust." And it's capable of speeds in excess of 100 kph. Beyond the weight savings a single skin afords by eliminating core (about 1,360 kg), Bergstrom points to another beneft. Each Sueños 53 can be customized to the customer's specifc wishes, which sometimes means changes to the cabin, seating layout, fsh lockers or additional appliances. "Te stringer grid's small panel sizes allows us to quickly make any change we need to accom- modate customer tweaks, without any tooling changes or major 'surgery' to the hull," he explains, noting, "I can just reposition the frames as needed. Tis design has allowed HydraSports Custom to elevate itself above commodity boatbuilding." Leva unveiled the boat at the 2015 Miami International Boat Show, explaining to the crowd that "sueños" is the Spanish word for dream. By show's end, the craft had won an Innovation Award for best center console walk-around fshing boat. Later it was declared Top Product for 2015 by Boating Industry Magazine. Te company is currently producing one Sueños 53 per month, and Bergstrom says there is a lengthy customer waiting list. "It is really wonderful to see how the advances we are achieving for the Navy beneft the recreational boating industry," adds Lewit, noting that the Sueños is one of the frst commercial deployments of the Navy SBIR work. "Back in 2004, when we frst envisioned the single-skinned hull and transom approach," he quips, "people thought we were insane!" Read this article online | short.compositesworld.com/Suenos Read about the rigid hulled inflatable boat project that paved the way in 2011 for the work on the Sueños 53 online in "Re-inventing the RHIB: Shock Mitigation" | short.compositesworld.com/ClIfo5Tk Bulked up for bigger engines The Sueños 53's hull and frame technology is designed for high speeds, reportedly up to 100 kph, for fast trips to fshing grounds. The single trans- verse engine-bearing frame that spans the transom (above) was increased slightly in size from the FEA-determined design, together with a more robust laminate schedule, to handle the extra horsepower with a greater factor of safety, without signifcantly impacting weight. The change was made for greater security when the four outboards were bolted through the transom. Source (top) | Structural Composites / (left) | HydraSports Custom Sara Black is CW's technical editor and has served on the CW staf for 17 years. sara@compositesworld.com