In conventional construction, fiberglass is laid into a mold and resin is brushed on. Workers then use rollers to spread out the resin and force the liquid into the fiberglass mat. The hull is left to cure in the mold, often with more resin than it needs — excess weight.
The three best-known processes for saving weight during lamination are resin infusion, resin impregnation and pre-impregnation. All save weight by preventing excess resin. They all also use vacuum pressure in the process to force the fiberglass, core and resin together for a stronger bond.
The best-known form of resin infusion is Seemann Composites Resin Infusion Molding Process (SCRIMP), and many manufacturers licensed it before Seemann’s patent expired. Other builders use their own variation of the process. The key is to ensure that the proper amount of resin is distributed through the system at the start. Specify too much and you’ll end up with a part that’s just as heavy as one rolled by hand.
In wet impregnation, the fiberglass fabric is fed through rollers that squeeze the epoxy resin into the material. The wetted fiberglass is then laid into the mold. Once all the layers are in place, vacuum pressure ensures that they bond well while removing excess resin. The mold is put in a large oven and heated for a specific time to ensure that the resin “kicks,” or fully cures.
Another method is pre-impregnation. Because epoxy resins cure at room temperature, the rolls of resin-soaked fiberglass must be kept in a cooler and applied in a chilled facility. They are rolled into the hull and bonded with vacuum pressure, then cooked to cure the resin.
Doug Zurn of Zurn Yacht Designs in Marblehead, Massachusetts, who designed the MJM series of motoryachts, said that impregnation supplies the best balance of affordability and precision. Added Lindsay, whose Boston Boat Works builds the MJM series, “We’ve found over the years that we can achieve the same resin concentrations with the wet preg as the pre-preg for a fraction of the cost.”
Beyond the hull and deck, builders can take a great deal of weight out of a boat on the interior and in the engine room. Peters estimates that only 50 percent of the overall weight is determined by how you build the boat. The rest is in what you install in it. Zurn doesn’t use carbon much in hulls, but in superstructures and masts. “We don’t mind a little mass in the hulls because you’re dealing with wave impacts, and that dampens sounds,” he explained.
In a combined initiative to make boats lighter and greener, many yards are now using veneer panels cored with honeycomb aluminum or plastic or even paper. They look like the real thing, are environmentally friendly and will last forever. The same can be done with stone, said Greg Marshall, president of Greg Marshall Design in Vancouver, British Columbia, who uses honeycomb-backed marble in his designs to generate huge weight savings. Additionally, honeycomb-cored panels have excellent sound-deadening qualities and are all the same width, which facilitates installation.
