Since fiberglass began replacing wood as a boatbuilding material in the 1950s, fiberglass boats today are still laminated in molds with fabric and two-part resins that are cured and made rigid with a thermosetting chemical process. The basic materials of chopped strand mat, cloth, and woven roving remain in use and the most common resin is still polyester. But 70 years of improvements have altered the final product—the boat—in significant ways. Here are the materials, processes and machines that have advanced our industry.
The first fiberglass/polyester boat was built in 1942 by Ray Greene of Toledo, Ohio, using Owens Corning fabrics and American Cyanamid resin. These two companies figured prominently in the development of materials for the boatbuilding industry.
Hand layup in open female molds was, and still is, the simplest way to laminate a boat. It is not an automated process and the results vary depending on attention to detail. But because boatbuilders needed heat to cure early polyester resins, for many years laminating in open molds was not possible.
A major breakthrough came in the late 1940s when California chemist John Wills added 0.5 percent of 6 percent strength cobalt naphthenate (CN) to the uncatalyzed resin. “At room temperature, by adding 1 to 1-1/2% MEKP, we produced gel and full cure within about an hour,” Wills said. American Cyanamid adopted Wills’ system and introduced the first room-temperature curing resin, Laminac 4116, in 1947.
Another invention from the late ‘40s was Dr. Irving Muscat’s Marco Method. Fabrics were laid over the top of a male metal mold and then a matching metal mold was placed over it. Resin was suctioned into the fabric from a surrounding trough, and heat applied to the molds to cure the fiberglass. The Marco Method was the first type of resin infusion.
The Blistering ‘70s
Osmotic blistering, which first became a serious problem in the 1970s and ‘80s, can be influenced by environmental conditions, such as water temperature and how long a hull has been immersed. All plastics are water permeable to some extent. The chemical process begins when outside water molecules meet water-soluble materials (WSM) inside a laminate, such as the binders used to hold fibers together. To combat this pox, manufacturing changes to binders, couplers, and thickening agents helped reduce blistering. Perhaps more helpful has been using vinylester resin for at least the skin coats of a hull laminate, and applying an epoxy barrier coat over the entire cured hull before launch. After the resin and reinforcement manufacturers addressed the issue, blistering became much less of a problem.
The Core of the Matter
During the late 1970s and ’80s there was a movement away from single-skin to cored hulls. There are several claims to the first cored hull, one of which is the 39’9” C&C-designed Red Jacket sailboat that won the Southern Ocean Racing Conference (SORC) in 1968. End-grain balsa sandwiched between an inner and outer skin of solid fiberglass made the hull lighter and stiffer, as well as providing some insulation that helps prevent condensation inside. Naval architect Rob Mazza, who designed for C&C Yachts and later worked for core manufacturer Alcan Baltek, said, “The focus on Red Jacket was weight savings with no loss of stiffness or strength. Her race wins validated that decision.”
In the ‘80s, coupled with the introduction of core materials came advances in fiberglass fabrics or “reinforcements” as they are called in the industry. For a time, Kevlar was employed in some boats in specific areas, mainly for collision resistance, but carbon-fiber prices have recently come down enough to build the entire structures of expensive race boats, and carbon fiber is used in strategic locations on moderately priced yachts.
The ‘90s: Introducing precision tooling
Because most boats are still laminated inside female molds, creation of the male plug, from which the female mold is taken, was for centuries built from wood frames and planks. But it’s nearly impossible to match the accuracy of a shape developed by computer and brought to life by a five-axis router milling a huge block of foam. Despite the higher costs, boat builders have become clients of tooling shops like Janicki Industries in Sedro Woolley, Wash., and Marine Concepts in Cape Coral, Fla., which specialize in creating precise tooling with robotics.
Open versus Closed
While open-mold laminating is still common, superior results can be achieved with closed-molding techniques, from covering the wetted-out reinforcements with a bag and drawing a vacuum to consolidate the laminate stack, to vacuum infusion in which resin is drawn into the laminate stack via a network of narrow tubes.
Everett Pearson, a pioneer in fiberglass boatbuilding, in the 1970s bought the proprietary technology called SCRIMP, used it at Pearson Yachts and TPI, and licensed it to others.
Resin Transfer Molding uses matched molds, and another process called VEC places thin molds inside water-filled pressure vessels. The goal of these methods is not only to remove voids and thoroughly encapsulate all fibers with resin, but also to accurately control the glass-to-resin ratio for strength and economy; 65:35 is an approximate standard, which is not achievable with hand layup.
Dr. Christopher Skinner of Owens Corning, however, said its product development team has recently increased glass content for open molding to over 30 percent with its OptiSpray Roving family. And according to another Owens Corning engineer, the ratio can go up to “40 percent and above with Advantex continuous-based fibers.”
Robotic processes will continue to improve the quality and consistency of hulls, decks and other boat parts, such as the laying down of fibers according to computer-generated load paths. There has also been some experimental work with “membrane” film hull materials. Skinner says: “We also expect to see the development of alternative processes for the production of parts such as PUR/LFI (polyurethane/long fiber injection); robotic systems; and the potential introduction of advanced technologies such as additive manufacturing in the manufacturing process.”
3D printing is advancing quickly. Already, small parts such as Hinckley Yachts’ Dasher dashboard, and a helm console for the Sacs Strider 700 RIB, are made with this rapidly developing process. The world’s first 3D-printed boat, the Livrea Mini 650 yacht, based on thermoplastic polymers reinforced with carbon fiber, should be launched this year. In the near term, 3D printing may be most useful for plug making, because it is an additive technology, whereby particles of a material are deposited into a shape, rather than milling, in which material is subtracted from a shape larger than the end form.
In the coming years there will be increased focus on environmentally friendly products such as bio-based resins and plastics made from renewable-sourced materials rather than oil. There is a growing desire in the boatbuilding industry to keep pace with the manufacturing world with emissions, recyclability, and end-of-life product planning.
This article originally appeared in the October 2019 issue.