- 8 June 2007 -
Yacht maker expands resin infusion operations

HATTERAS YACHTS, based in New Bern, North Carolina, USA, has expanded its resin infusion operations to motor yacht hulls up to 21.9 m (72 ft) in length.

“Compared to hand-laid fibreglass, the resin infusion process gives us more consistent part quality,” explains Chris Walker, manager of structural and composite engineering for Hatteras Yachts. “Improved part-to-part consistency ensures a more precise fit to bulkheads, stringers and other structural components. And the higher glass-to-resin ratios associated with resin infusion increases component strength while lowering overall part weight.”

Hatteras Yachts is a licensee of Seemann Composite Resin Infusion Moulding Process (SCRIMP®) technology from TPI Technology. The boat builder’s initial experience with the process started with bulkheads and decks, amongst other parts. Before the hull the largest part produced using the infusion process was a 24.6 m² (265 ft²) deck. An 18.3 m (60 ft) sport fishing convertible was selected for the first resin-infused Hatteras hull and a large-flanged female mould was built specifically for the infusion technique. The bottom of every Hatteras Yacht hull is a glass reinforced composite. Polyvinyl chloride (PVC) foam cores are incorporated in the hull sides and superstructure to provide high stiffness at a lower weight.

Hull infusion begins with the application of a clear gel-coat and a vinyl ester skin coat into the female mould. Fibreglass roll goods cut to precise patterns are then laid down, along with PVC foam coring in select sidewall areas. The reinforcement and core are covered with the SCRIMP resin-flow medium. A layer of polymer film is applied over the dry fibre-core build-up and sealed over the large flanges on the edge of the mould. During resin infusion, 29 inches vacuum of mercury (1 bar) is pulled to draw resin through the fibreglass reinforcement and create the desired fibre-reinforced composite shape between the mould surface and film. After gaining experience infusing the 18.3 m (60 ft) hull, engineers and the work crew were ready to infuse the 21.9 m (72 ft) hull. The constant thickness and dimensions provided by infusion ensure a precise fit with resin-infused structural components. Once the infused hull shell is prepared for secondary bonding, the primary PVC foam cored longitudinal stringers are infused into the hull.

According to Walker, resin supplier AOC helped his team by following every step during development and being on-hand for the initial hull infusions to ensure Hatteras’ requirements were met. AOC claims that the Hydropel® vinyl ester resin met two primary sets of specifications for the hull structure – one for processing in the shop, the other for performance on the water.

“It took a significant amount of developmental work to identify and qualify our infusion resin,” says Walker. “We needed optimum viscosity and open times for filling the 60-ft hull in one shot. We also needed to keep the exotherm low for cosmetics while retaining our required structural properties when the part cured.”

AOC; www.aoc-resins.com
Hatteras Yachts; www.hatterasyachts.com

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