Hydropel Aids Hatteras Infusion

30 April 2007

The boatbuilder Hatteras Yachts has expanded its resin infusion operations to motoryacht hulls up to 72 feet (21.9 metres) in length.

The company’s progression into resin infusion is getting help from technical support and Hydropel resin technology from AOC.

“Compared to hand-laid fiberglass, the resin infusion process gives us more consistent part quality,” said Chris Walker, Manager of Structural and Composite Engineering for Hatteras Yachts. “Improved part-to-part consistency ensures a more precise fit of 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.

“All these factors translate into a winning combination of better performance and fuel efficiency for the customer,” Walker continued. “And because resin infusion is a closed moulded process, emissions in the workplace and into the environment are almost completely eliminated.”

Hatteras Yachts is a licensee of SCRIMP (Seeman Composites Resin Infusion Molding Process) technology from TPI Technology. Hatteras’s initial experience with the process started with bulkheads, athwartships, soles (decks), and other parts. Before transferring its resin infusion experience to hulls, the largest infused part was a 265-square-foot (24.6-square-metre) deck.

A newly designed 60-foot (18.3-metre) sportfishing convertible was selected for the first resin-infused Hatteras hull. A large-flanged female mould was built specifically for the infusion technique. In addition to being larger than previously infused parts, the hull is much more complex because it incorporates various design features that achieve a unique combination of speed, comfort and a dry ride.

For the hull structure, a Hydropel high performance vinyl ester resin met two primary sets of specifications – one for processing in the shop, the other for performance on the water.

Hull infusion at Hatteras begins with the application of clear gel coat and a vinyl ester skin coat into the female mould. Next, fibreglass roll goods cut to precise patterns are 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. When the entire part has been infused, the resin cures to create a highly densified and repeatable composite structure. The SCRIMP cloth and polymer film are removed after the parts cures. Optimum viscosity & low exotherm

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

Walker added: “Our dedicated team was able to do all this with the help of our primary AOC contacts – Berk Pleasants and Bob Reese. They took a real hands-on approach to helping us. They followed every step during development and were here for our initial hull infusions to make sure our requirements were met.”

After establishing resin infusion experience with the 60-foot hull, engineers and the work crew were ready to infuse the hull of a 72-foot motoryacht. The constant thickness and dimensions provided by infusion ensure a precise fit with resin-infused structural components. After the infused hull shell is prepared for secondary bonding, the primary PVC foam cored longitudinal stringers are infused into the hull, shown in the image.

“Since its inception almost 50 years ago, Hatteras Yachts has been uncompromising in its pledge to build boats of the highest integrity and quality,” said AOC Business Manager Emilio Oramas. “AOC is proud to contribute technology and support that help the people of Hatteras exceed their already superior standards.”

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