But the addition of carbon fiber isn’t the only material change Scout has made. The company’s latest introduction is a switch from polyester and vinyl ester hulls to epoxy resin. “It all started because we have a lot of our customers who want dark colored hulls,” Potts recalls.
Producing a black hull can be a challenge because imperfections show up more easily. As Corbett Leach, Composites One technical support manager, explains, “Fabrication with polyester resins often requires the addition of print blockers and barrier plies to prevent surface distortions and imperfections. In addition, completed hulls typically need time-consuming secondary rework and refinishing.”
But Scout’s goal was to produce a dark Class A finish that could weather “gracefully,” as Potts puts it, requiring only minimal maintenance against the long-term effects of sun and saltwater. After years of testing different formulations and curing packages, the company determined that there was no substitute for a post-cured epoxy resin system.
As Potts point out, getting improved weathering from this resin system turned out to be icing on the cake. “We already knew that the physicals of epoxy are significantly better than polyester and even better than vinyl ester. So, we not only got the Class A finish to age more gracefully, but we also got much better physicals,” Potts says.
According to Huntsman Advanced Materials, which supplied the resin for this project, epoxy resin is 20 to 30 percent stronger than polyester and vinyl ester materials, with a higher elongation, tensile strength and modulus/stiffness properties. By making the switch to epoxy, Scout decreased the number of laminate layers while maintaining the strength and performance it achieved with other boats.
Scout Boats’ in-house designers worked closely with Composites One in fine-tuning this system. The build team began assembling the hull with a polyester gel coat backed by a vinyl ester barrier coat and hand-laid vinyl ester skin coat. Next, they sanded the skin coat, then put down multiple plies of a pre-cut dry carbon hybrid quad knit fabric. The rigid foam core was sandwiched between fiberglass laminate layers. A tackifier adhesive secured the plies in place.
Huntsman notes that the high-performance resin system used on this project was specially formulated for use on large parts. Its water-like viscosity makes for a more controlled resin flow throughout the laminate, ensuring each area of the hull is evenly coated. After infusion, the epoxy cured at room temperature and then post-cured under a tarp with a heat blanket that helped ensure a constant temperature.