By Barbara H. Kempe
In order to efficiently fabricate large, multi-component yachts using the strongest and lightest material possible, Intermarine Savannah has developed and refined a process of applying composite materials that is designed to save time, money, and to be environmentally friendly.
Intermarine's method is a vacuum infusion process (VIP) in which vacuum is used as the main force to pull resin through dry fiber reinforcements. The reinforcements are loaded into a mold. A manifold system is then added to allow air to escape and resin to enter. The mold is sealed with a plastic bag, and vacuum is applied to evacuate air and pull resin into the fiber.
The specialized technique developed at Intermarine enables resin to flow through and around without requiring a disposable flow medium. A unique, grooved core is produced in-house, allowing the resin to flow through the glass instead of under it. This makes the production of high-quality, large sandwich composite parts needed for bulkheads and decks for megayachts possible.
Four 123-ft. raised pilothouse motoryachts are currently under construction at Intermarine using only this method, said marketing manager Sherrie Drummond.
According to Intermarine Savannah's composite research director, Belle Gall, the process is "an ongoing evolution." The Intermarine team of engineers, technicians, researchers and production staff began working with several previously developed concepts and infusion materials in 1998 and has been applying their findings to meet specific needs since. The current process used at Intermarine, she said, was developed through approximately one year
of intensive testing.
The VIP process is now used where open molding and vacuum bonding processes were used in the past. It produces lighter, stronger and better-bonded laminates than open molded parts, Gall said, adding the labor cost of vacuum infusion is also less than with previously used methods. "Vacuum infusion offers many of the advantages of RTM molding without the expense or limits of specialized molds," Gall said, adding that the process can also be used with most molds for open molding. Vacuum infusion also offers environmental advantages, said Gall. Since resin remains trapped under a plastic bag while the part is curing, the amount of volatile organic compounds (VOCs) released is significantly reduced. Additionally, because infusion is less messy than other techniques, the amount of cleaning solvents used daily is also lessened, reducing the amount of VOCs even further.
As a result of employing the new technique, production staff members are now working in a "cleaner, friendlier environment" with less exposure to styrene. Their work requires more attention to detail, but less physical labor. New equipment required by the process includes a vacuum system and a specialized saw used to groove the core material. To train employees in using this equipment and the new production process, Intermarine uses a combination of classroom and hands-on instruction. Those working with infusion are educated on how and why the process works and then log hands-on experience using the process. Training
is an ongoing process, said Gall, because "vacuum infusion is not a process that can be learned overnight."
According to Gall, Intermarine feels the new process will bring about significant improvements within the yachtbuilding industry. "Intermarine Savannah is interested in keeping this technology open. The composite industry is vast, from automotive, to marine, to civil engineering, but composites are a small percentage of these markets. We would like to part of the composite revolution. When the technology is open, more people can benefit, and in turn, contribute," said Gall.
To that end, Intermarine Savannah representatives presented a technical paper at the Composite Fabricators Association (CFA) conference in September 2000 in Las Vegas. The paper describes how Intermarine's process was utilized for the fabrication, in one infusion, of a 1,632-sq.-ft. sandwich core deck with integrated 400-sq,-ft. longitudinal and transverse stiffeners. The presentation also included a brief history of hand-laid parts and the vacuum infusion process, detailed technical descriptions of infusion materials and properties, and an in-depth look at how the process was refined at Intermarine. The paper maintains that the infusion method can be applied to almost any size or shape composite part, including large bulkheads with double layers of core or combination single-skin and core panels and longitudinal girders more than 100 ft. long.
The paper concludes by stating that continuing research and development is needed to tailor the VIP process to the current needs of the industry. "If we can keep this new technology open and available to all, we will see a much greater and more rapid development in the industry - something that will benefit everyone."
Gall said the response to the presentation has been positive. "Most people are quite happy that someone is offering a look at infusing large parts," she said.
Intermarine will present another paper, depicting the infusion of a 123-ft. motoryacht hull at the upcoming CFA conference in Tampa, said Gall.