CompositesWorld

JAN 2016

CompositesWorld

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JANUARY 2016 46 CompositesWorld FOCUS ON DESIGN Tey come in several sizes — essentially of-the- shelf, tabbed, fexible preformed elements that can be tailored to length and location for the project (see photo at right). Smaller, 50 mm by 100 mm frames go down on the hull laminate frst, followed by larger stringers, some as tall as 1.2m, on top of the frame network, with cutouts on their bottom edges to enable a tight ft over the low frames. Te larger stringers support the fat sole of the Sueños 53. Designing for less fex To eliminate the possibility of gel coat cracks caused by hull fex, Reichard's FEA pinpointed high-defection areas, and the team adjusted the low-frame grid to make the hull panel size smaller in those areas by reducing the distance between the frame members. "Te hull defects, but with our adjustments to the preform grid, and some laminate padups for greater strength in a few areas, we were able to get defection values well below the maximum elongation of the gel coat, so it won't crack," adds Bergstrom. Te framing plan was "the largest and most complex Prisma hull kit we've ever done," says Lewit. "We're calling the larger hull preform element kits MEGAFORM." Going with solid laminate in the transom, however, was a big step, admits Bergstrom. Reichard recommended a single trans- verse frame across the transom width, supported by three tall Prisma preform beams connected to the hull frame layout (see drawing, p. 45). Says Reichard, "Te engines would be bolted through the transom laminate, with top bolts above the frame and bottom bolts below the frame." Te outboard engine thrust forces, then, would be transferred into the frame. "A traditional cored sandwich design strong enough to handle these outboards would have been too thick." Although the FEA showed the single skin/frame design was adequate to handle the four outboards, Bergstrom wanted a greater safety factor to ensure zero problems with the transom. He enlarged the dimensions of the single transverse frame and increased its laminate schedule. He also specifed a polyvinyl chloride (PVC)-based, non-compressible liquid to be poured around the transom frame, the connecting stringer beams and The basic frame component An example of a Compsys Prisma composite frame, available in a range of lengths and sizes to meet the design parameters. The attached tabs allow the frame to be laminated to the single-skin hull. Source | Structural Composites Kitted, fitted and ready for resin infusion The MEGAFORM hull preform kit is dry ftted into the hull, prior to wet lamination over the smaller frames. Source | Structural Composites

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