Skip to main content

Boatbuilders breaking the mold

From thermoformed plastics to closed-molding techniques, boatbuilding is in the midst of a technological renaissance

From thermoformed plastics to closed-molding techniques, boatbuilding is in the midst of a technological renaissance

Editor’s note: This is the first of a two-part series on boatbuilding. This story examines some of the new processes and materials used to build boats up to about 35 feet. Next month’s package will focus on the range of methods and materials used in larger boats and custom boats, as well as high-tech building.

It’s a typical late afternoon at a South Florida boat show. A warm breeze blows through the exhibitor tent as a 40-something man in a T-shirt and shorts listens to a dealer rep extolling the virtues of a 21-foot white-hulled center console. The salesman steps forward to thump the boat’s hull side … with a sledgehammer. He whacks it once, twice, three times as hard as he can. The boat absorbs the blows and doesn’t appear to be damaged.

“That’ll do,” says the satisfied attendee, envisioning an encounter with a log or some other submerged peril.

Welcome to boatbuilding in the 21st century.

In the last few years boatbuilders have made leaps in construction and manufacturing technology. Whether the goal is increased efficiency, environmental protection or simply to build a better boat, companies are exploring closed molding, advanced polymers, and computer-controlled processes. A handful of boatbuilders known for the use of new materials and manufacturing technologies were founded in the last 15 years, while other, established companies have overhauled their processes in the last decade.

Glastron, for example, has built fiberglass boats for more than 50 years, but now builds most of them using a closed-molded and computer-controlled process known as VEC (Virtual Engineered Composites). And bringing the manufacturing process into the computer age has brought a new work force into boatbuilding.

“A lot of people weren’t looking to get out of high school and put on a mask and lay up a boat,” says Glastron general manager Bruce Sargent. “But when you tell them they can use their computer skills to build a boat, it’s a whole new generation of boatbuilders.” Sargent says 88 percent of Little Falls, Minn., company’s boats, which range from 17 to 27 feet, now are built with VEC.

From closed molding to rotational and thermoformed plastic construction, boatbuilding has come a fair distance from the days when fiberglass-over-wood was popular. “I think things have changed a lot in the last 15 years,” says Stephen Dougherty, president of Everglades Boats, of Edgewater, Fla., a technology leader that uses the patented RAMCAP process to build its boats. “We were seeing rotten stringers, transoms and floors, and boats were falling apart.”

He says boatbuilders realized they had to invest in the product and processes to get ahead. Witness the recent evolution of stringer systems. First, builders began installing fiberglass grid systems — rigid and strong but labor-intensive. Then companies began injecting foam into hollow fiberglass stringers. Now, many builders use preformed foam logs and glass over them.

Advanced construction processes obviously don’t end at closed molding or plastics. Some builders are stretch-forming aluminum to create hulls with complex compound curves. That’s not to say that traditional methods can’t produce a good, strong boat.

Grady-White — which has won six straight customer satisfaction awards from J.D. Power and Associates among others — builds boats predominantly with hand-laid, open-mold construction and polyester resins. While it uses some exotic laminates and coring in select places, its recipe for success is based on control and consistency.

“Our whole philosophy is we stick to the tried and true methods and processes,” says Joey Weller, Grady director of sales and marketing. “We believe it’s about process control and reliability — the dependability of your processes and doing it right.”

Although Grady has closed-molded some parts for 15 years, a scientific approach to traditional boatbuilding reigns at the Greenville, N.C., company. “When it’s all said and done, it has to stand the test of time,” says Weller.

Despite what Everglades and others are doing with advanced technologies, Dougherty expects traditional open-molded fiberglass hull construction, with foam-and-fiberglass stringers, to continue for years.

“It’s a fast, simple way to build a boat,” he says. “And I see that sticking. When you look at big boats and Sea Rays, that’s what they’re doing, and that open layup will be around for years.” Traditional boatbuilding will stay until it’s regulated out of existence, or at least out of the country, by environmental laws, he says.

Green boatbuilding technologies may eventually give builders the flexibility — and more importantly the environmental credits — to build other boats using techniques that aren’t as environmentally friendly. But challenges stand in the way of wider adoption.

It takes time

“I think a lot of times, the new technologies take time,” says George Blaisdell, vice president of operations at Triumph Boats in Durham, N.C., which builds rotomolded plastic boats using a process called Roplene. “We look back at fiberglass technology in its infancy, people would say, ‘I’ll buy a fiberglass boat when there are fiberglass trees.’ It took a while, but people came to accept fiberglass over wood.”

One key difference, however, is the high cost of entry into new technologies compared to the early days of fiberglass. “You’ve got to pony up some serious dollars to do what we’re doing,” says Blaisdell. “New technology is expensive until it’s commercialized.” (Triumph, incidentally, is the subject in the aforementioned sledgehammer test and has video of that and other tests at .)

When Triumph first started up, under the name Logic, it searched for employees who were versed in rotomolding and learned such people simply weren’t out there. “Intellectual capital is tough to come by,” says Blaisdell. “We found we had to grow it internally.” The company had to develop the software to control the oven, for example.

“You couldn’t go to the Rotomolding 101 book and see, Oh, this is how it’s fixed.”

Blaisdell compares Triumph’s model to the kayak industry. Fifteen or 20 years ago the industry was predominantly made up of fiberglass kayaks. “Now not only are 90 percent of kayaks rotationally molded, but they’ve grown the industry tremendously,” says Blaisdell. “We think the [boating] industry will change. I think it’s inevitable that there’ll be more doing it.”

Hunter Marine stands out from the kayak and dinghy companies that build thermoformed plastic boats. Alachua, Fla.-based Hunter uses a large thermoformer to build trailerable sailboats to 21 feet out of ABS plastic.

“It’s a little bit more of an investment in the beginning, but for the man-hours you save it’s definitely worth it in the long run,” says Ted Norris, Hunter’s North American product sales manager.

The O’pen Bic sailing dinghy offered by Bic Sport North America of West Wareham, Mass., also has a thermoformed polyethylene hull, but it only measures 9 feet in length (

High volume

While custom shops often use exotic materials and methods to build high-tech boats, innovation takes on a different form when it comes to production boatbuilding, where margins are much tighter. Many of the boats being built with closed-molding techniques or plastics are entry-level because of the high sales volume necessary to offset the cost of the equipment. VEC technology, for instance, requires a large manufacturing facility, in addition to the expensive equipment inside.

Everglades president Dougherty says his company makes up for the high cost of the tooling and foam molds for its fiberglass boats through labor savings. Building plastic boats requires expensive equipment, too, though many say the tooling lasts virtually forever.

“The molds last pretty indefinitely — like our 17-foot mold is going on 11 years here,” says Triumph’s Blaisdell, who says it costs around a half-million dollars, including materials and labor, to build each of its molds.

Here’s a closer look at five techniques being used to build boats 35 feet and under today, including closed molding, rotomolded plastics, thermoformed plastics, and a couple approaches to unsinkable foam sandwich construction.


Glastron and Larson — both part of the Little Falls-based Genmar boatbuilding conglomerate — build fiberglass boats using VEC technology, a closed-molding process designed to reduce production time and pollution, and result in a more consistent finished product.

In VEC, workers spray gelcoat into a female mold then lay down all layers of fiberglass, the stringer system and the transom. A male mold is lowered from above, and the two pieces are locked together in a “vessel” filled with 8,000 gallons of water. At that point, resin is vacuum-injected between the molds. Water pressure compensates for the relatively thin molds, in addition to bearing some of the tremendous heat generated as the resin cures. (Heat has been a bugbear of closed-molded construction.) The whole process is computer controlled, and each computer “cell” runs two vessels.

The first boats to come out of the original Larson plant around the turn of the millennium were a 17-foot Glastron and an 18-foot Larson. “Then we realized it was really going to work, and we needed to build a new facility,” says Glastron general manager Sargent. Larson’s line ranges from 18 feet to 37 feet, and 79 percent of boats between the two companies are built using VEC.

With the new plant in Little Falls, the companies now have four computer cells, so they can build any eight models at one time. Each cell has its own crew and can produce up to eight hulls in an eight-hour shift. Plus a boat comes out of a closed mold nearly 100 percent cured, compared to about 80 percent cured when popped out of an open mold.

To build eight 17-foot Glastrons per day with conventional open molding would require a dozen hull molds, according to Sargent. Instead, the company just runs two shifts of workers at a single vessel dedicated to the 17-footer. Boats are rotated in and out of production, while some popular models stay in at all times. ,


Triumph Boats, another Genmar brand, builds outboard saltwater fishing boats from 12 feet to 23 feet out of rotomolded plastic using the Roplene process. Roplene begins with a proprietary polyethylene compound powder loaded into an all-metal mold. Capable of withstanding temperatures exceeding 500 F, the mold is mounted in a convection oven, where it bakes and forms a single-piece boat, including hull, transom, storage boxes, gunwales and deck cap. The mold then rotates during a controlled cooling process to ensure consistency.

Foam is injected between the hull and deck after the boat is removed from the mold, and it goes through final assembly of decks and equipment. In addition to the foam flotation, the Roplene material itself is buoyant.

Repairing a rotomolded boat entails welding with plastic to fix holes or large gouges. Scratches, though, can be sanded out, since the color goes all the way through the plastic. Roplene material requires a special primer before applying bottom paint or decals.

Triumph recently introduced its largest boat to date, the 235 CC. Boat size is limited by the size of the oven, Blaisdell says. “With the equipment we have today we could do a 25-footer,” he says. In the near future, however, the company plans to fill in its current line, and add a walkaround model — its first cabin boat.

Thermoformed plastic

Hunter Marine uses a vacuum-forming process with ABS plastic sheets to build its trailerable daysailers. The large plastic sheets are loaded into an oven, where gravity and suction force it onto a mold. After cooling, the finished hull is blown off the mold. A fiberglass layer is then laid down, and foam is injected in the space in between. The result is a composite boat with a plastic outer layer, high-density urethane foam that provides structure and impact resistance, and a fiberglass backing.

Hunter consolidated its manufacturing last December when it moved its small-boat plant from East Lyme, Conn., to its headquarters in Alachua. The company’s full line of sailboats ranges from 9to 49 feet, though thermoformed models only cover the range up to 21 feet.

“The technology is not there at this point in time to do anything larger than our 216,” says Hunter sales manager Norris, who says supporting larger plastic sheets in the oven poses a challenge. “Someday down the road there’ll be composite boats that are larger sizes.”

Thermoformed plastic boats are said to be more impact resistant than fiberglass; won’t dent, crack or craze; and are scratch resistant. “You aren’t going to have to repair gelcoat,” says Norris.

Specifications and repair characteristics compare to fiberglass. “It’s very similar, if not a little lighter, than fiberglass,” he says. “The 216 weighs [1,350] pounds, and that includes a 500-pound lead keel. [And] it’s going to stay stiffer longer. Some of the older [JY15s] are just as fast, or faster, than the new boats. They’re just as tough and rigid as they were when they came out of the mold in 1992.”

A thermoformed plastic boat can be repaired with fiberglass, Plexis or simple body filler. Norris says Hunter’s thermoforming process is green, as there are no resin fumes; the only emission is heat.


Everglades Boats uses its patented RAMCAP process to build fiberglass saltwater fishing boats from 18 to 35 feet. It’s also built RAMCAP hardtops for numerous boatbuilders.

In RAMCAP, or rapid molded core assembly process, the hull and deck are laid up over three premolded foam cores in hull, deck and transom shapes. Once the pieces are ready, the entire boat is then vacuum-bagged. The process eliminates “blind foaming” — where foam is injected into a closed cavity — allows more control over the quality of the foam core, and gives excellent adhesion, according to the company.

The process, from laying down the main skins to closing everything in the mold, takes 35 minutes. “In a traditional boatbuilding process, that would probably be three shifts,” says Dougherty. “And when you’re doing that it’s a lot of secondary bonding. Our hull is put together 100 percent with a primary bond. We build truly a one-piece hull.”

The 6-pound-density urethane foam feels like wood, according to Dougherty. “So now our foam flotation doubles as hull stiffeners,” he says. “When our boat comes out of the mold, it’s finished.”

To his knowledge the new Everglades 350cc is the largest closed-molded piece of fiberglass in the world. And, not surprisingly, he believes RAMCAP is the best way to build a boat.

“We have a very rigid, very stiff hull,” says Dougherty. “People say fiberglass has to move, fiberglass has to flex — that that’s how you keep fiberglass alive. But you forget that we have gelcoat over that, and you don’t want it to flex because it will crack.”

Everglades has been approached about licensing RAMCAP, but so far has declined to do so, according to Dougherty.


Long before RAMCAP, Boston Whaler used foam for structure in its Unibond construction process. Liquid foam is injected between the fiberglass hull and deck before the resin sets up, chemically bonding the foam and glass as they cure. The technique has been used to build most Whalers since the company was founded 50 years ago. In terms of the production boatbuilding industry, it remains state of the art.

“In a sense the materials have changed, and the process has changed some, but it’s relatively the same as it was in 1958,” says Miles Gathright, a material and process engineer for Edgewater, Fla.-based Whaler.

Instead of hand-mixing foam, a million-dollar machine now performs that function. And Whaler switched to a more environmentally friendly foam, which is unique to its construction process and one reason the company can’t use closed molding for its hulls.

“We can’t do our hulls with infusion. It’s got to be the way we’ve been doing it, and that’s because of the state of cure of the laminate,” Gathright says, since the foam and resin need to bond.

As with other progressive small-boat building techniques, smaller Unibond Whalers pop out of the mold simply requiring final assembly. “The little boats, they literally come out of the mold, and you’ve just got to put a seat and a steering wheel on them,” says Gathright.