A Cleaner, Faster Infusion Shop


Aaron Porter | Professional BoatBuilder Magazine

The hull and deck parts of a 10.5′ (3.2m) UFO sailing foiler at Fulcrum Speedworks are shrouded by custom-made reusable silicone vacuum bags during infusion of the dry laminates with vinylester resin. Made from discarded prototype masts, gantries support the web of feed and vacuum lines to infuse the complex shapes; they also serve as an overhead hoist to lift the heavy bags off the finished parts after the resin has cured.

Dinghy builder Fulcrum Speedworks reduces consumables by as much as 90% by switching to infusion under reusable silicone bags.

It’s not news to boatbuilders and owners that plastic waste in the oceans has reached critical levels. According to the nonprofit Ocean Conservancy, about 8 million metric tons of plastic trash end up there every year. It’s only within the past five years that steady reporting on the vast accumulations of garbage in remote ocean gyres and the prevalence of plastic waste in pelagic seabirds, oceanic fish, and marine mammals has led to significant changes in public behavior and policy ashore. While coastal cleanup efforts and local waste-disposal reforms are now common, it’s clear to many that reducing plastic waste at its many sources is an essential next step.

Like many self-aware coastal municipalities in New England, the town of Bristol, Rhode Island, adopted a local ordinance banning single-use plastic bags in April, 2018. It’s no surprise. Bristol owes a lot to the ocean. Shipbuilding became a mainstay of the local economy starting in the 1600s, and since the Herreshoff Manufacturing Company opened in the 1870s, the town has arguably been the creative center of innovative yacht design and building in North America. Cutting-edge shops like Goetz Composites, FastForward Composites (see Professional BoatBuilder No. 181), and the New York Yacht Club’s American Magic team are building fast and innovative custom sailboats in Bristol today. In addition, production builders, subcontractors, and specialized marine components shops in the area are still thriving, but like most composites manufacturing endeavors, they all produce a significant volume of nonorganic waste in jagged trimmed laminates, solid cured resin, infusion transport medium, peel ply, and sheets of plastic vacuum-bag material.

Dave ClarkAaron Porter | Professional BoatBuilder Magazine

Dave Clark heads the production team and directs the tightly choreographed infusion.

It was the dumpster loads of spent consumables leaving his Bristol shop every month that got the attention of Dave Clark at Fulcrum Speedworks, where a crew of six builds an average of three finished 10.5 (3.2m) UFO sailing foilers per week (see “The People’s Foiler,” PBB No. 166). For each boat, he said, “we’re talking about  $240 worth of process material and mountains and mountains of garbage.” That waste of money and material was part of what drove him to successfully impose his own personal vacuum-bag ban in the summer of 2019.

“I can’t harp on the garbage enough,” he said. “Basically 90% of our dumpster load was disposable laminate. I was sick of buying vacuum bags. I was sick of buy­ing sticky tape, flow media, and peel ply; sick of spraying really expensive copolymerizing spray glue into my laminate in order to get flow media to stick.”

But there was more spurring his waste-reduction efforts than the expense side of his production spreadsheet. As a boatbuilder, “you’re providing something that is, while durable, ultimately ephemeral, so there’s a moral consequence to that. I insist on looking at it,” he said. “It was like ‘The Picture of Dorian Gray’—for every UFO that goes to a customer, a similarly sized and priced garbage-shadow of a UFO goes straight into the dumpster.” That shadow is the environmental cost Clark and his team have dramatically reduced, primarily by switching their infusion production process to include reusable silicone vacuum bags. Sounds simple; it’s not.

Infusion at 253 Franklin St.

I visited the shop in Bristol last July to see the new system in action about a month after they had made the transition to silicone.

Infusion is one of the more dramatic processes in modern boatbuilding; more like a theatrical or musical performance than a science experiment where only a couple of variables can change. Any shoot is a high-stakes investment in labor and materials—a choreographed and somewhat vulnerable process that depends on the coordination of multiple variables as catalyzed resin is pulled by a vacuum pump into a stack of dry laminates in a complex mold. Plastic vacuum bags can leak; the resin flow can fail to wet all the laminate; resin can start to gel before the shoot is complete; profile elements can suffer from bridging under the flow medium; etc. The inherent risks of the process make it engaging to watch.

Infusions at Fulcrum take place in the morning, so the two molds—hull and deck—were fully loaded with gelcoat and laminate stack the day before and were ready to go when I arrived.

“Globally, the laminate is 10-oz glass, 2mm Soric, 10-oz glass, and that’s it,” Clark said. “In the beams, we increase thickness of core with a 1mm layer of core mat and reinforcements of carbon fiber, 300-g unidirectional carbon. In the deck there’s a double layer of glass where you sit.” An added complexity for the infusion is a thick mast pocket of 55-oz/sq-yd (1,851-g/m2) triaxial.

But that was all shrouded under the blue-hued silicone bag and a profusion of vacuum tubes descending from a gantry-mounted manifold suspended above each mold. I noted the absence of the ubiquitous tacky tape that pervades a conventional plastic-bag infusion. In its place, an army of customized Vise-Grips fix the bag’s perimeter in an airtight seal to the generously proportioned mold flanges. By Clark’s count, including those that control feed lines, the process requires “about $1,000 in Vise-Grips.” But they don’t end up in the trash after every shoot. Similarly, there’s no disposable spiral tube visible under the bag, only 13 longitudinal channels that appear as milky white stripes with vacuum tubes emerging from them.

The bags and feed lines had been drop-tested beforehand, and to start the timeline for the entire shoot Fulcrum’s resident mixologist, Tony Diogo, catalyzed 23 lbs (10.4 kg) of custom-promoted resin in each of two 5-gal pails. Epovia RF-1001 is a vinylester that perfectly bonds to gelcoat, and according to Clark, it was a formulation driven by infusion of the C&C 30 One Design at Pearson Composites. “It’s mechanically virtually identical to WEST 105/205,” Clark said. But unlike the epoxy, it starts to gel in 30 minutes, so time is of the essence.

Aaron Porter | Professional BoatBuilder Magazine

Experienced composites technicians Mario Neves (r) and Tony Diogo coordinate opening and closing the feed lines (with Vise-Grips) that supplycatalyzed resin to the parts.

Diogo and composites technician Mario Neves submerged the feed lines into the first 5-gal pail in the narrow passage between the two molds, oriented transom to transom. Clark clicked the stopwatch on his phone and called for line one. Diogo and Neves sprung open the Vise-Grips on the appropriate feed lines and adjusted vacuum valves on the two parts. The silicone channels running down the center of both molds filled with dark resin that bled steadily into the surrounding laminate. All three men circled the parts, monitoring the flow and resin fronts.

“These runners are crushed down to the floor. The resin flow into it has to relieve it and allow it to fill up. As it fills, you’ll see it start to flow sideways,” Clark observed. “The next thing you have to do is shut it down and drag the bag back down.” That’s accomplished by shutting off the feed line and delaying opening the next in sequence until the first silicone runner is collapsed by pressure from the advancing resin front.

The sequence continued with all three men constantly in motion, talking, updating the condition of the infusion in both parts simultaneously. Clark gave a running commentary of details: Line 3 is challenging, as it has to fill the beam structure, and line 5 “always gets a resin-rich area on the inside chine.” Then line 6 has to drive the resin up the side of the hull. “It’s climbing right up. It’s going like a gunshot,” he announced, warning that things were moving faster than anticipated.

Meantime, as soon as he was sure no more resin would be required from it, Diogo had slit each clamped feed line, allowing excess resin to drain back into the bucket to be used. Infusion was complete in about 21 minutes, and the vacuum was set to hold for the next couple of hours as the resin cured.

Aaron Porter | Professional BoatBuilder Magazine

About 23 lbs (10.4 kg) of vinylester is drawn from 5-gal pails during each simultaneous infusion of a deck and hull part.

“People ask, ‘Do you really need that many feed lines? Can’t you just have a center feed and wait?’ Well no, because our resin system is going to go off in no time, and you’d overbulk at the center,” Clark said. It would also require that full layer of flow medium that he has eliminated from the build. He explained that by limiting flow to what can pass through the Soric core, the multiple feed lines must act like paint brushes. “You dip the brush into the bucket and paint the next area, dip, paint the next area, dip . . .” It also provides infinitely more versatility to precisely deliver more resin or vacuum to a specific area if something is not going right.

The first 253 UFOs were conventionally infused using yards of peel ply, black shade cloth flow media, rope around the perimeter for the suction manifold, spiral tube, eight rolls of tacky tape, and a full plastic vacuum bag. Aside from all that waste, an additional 12 lbs (5.4 kg) of resin that saturated the material was thrown away with each build.

Clark said while building those first boats, the team had made some small advances or “chip shots” to improve efficiency and clean up the process, a number of them with silicone. He showed me how he’d made reusable silicone masking jackets on the foil molds when spraying gelcoat. “Saves about three rolls of tape a week, but more importantly the time putting it down,” he said.

Aaron Porter | Professional BoatBuilder Magazine

Tooling for structural stiffener plates that connect the beam to the outside of each hull.

He’d also created some innovative silicone tooling to efficiently produce fiberglass stiffener plates, bonded with Plexus inside the hull in way of the beam. “We were wasting a ton of time cleaning the [conventional] mold and getting it rewaxed. So we made a fiberglass backer on a silicone mold with silicone compressing plates that go inside, and the whole thing just squishes,” he said. Cleaning the silicone mold is as simple as banging it on the bench and blowing out any detritus from the last part. It has been used 200 times without failure.

Clark is proud that Fulcrum hasn’t used disposable spiral tube in its infusions since hull #40. Instead, the crew has been developing and refining the collapsible silicone runners that are built into the new bags. They started as square-sectioned, three-sided silicone channels that were inserted under the vacuum bag as a replacement for spiral tube. Clark said as the design developed, it became clear that the collapsible channels could pull right down flush with the infused surface, saving resin and reducing the need for post-cure grinding. When integrated into the full silicone bags, it also helped reduce the need for peel ply over much of the part surface. “The standard of compaction underneath the runner is the same as for anywhere else under the bag,” Clark said. “Our campaign now is to get rid of as much peel ply as possible.” In the shoot I watched, it was only in a few areas where there would be secondary bonding, where the feed entered, and in places where bag release would be difficult.

Interruptions and Refinements

Fulcrum’s sophisticated technical advancements have been significantly driven by the young company’s fluid circumstances and business challenges.

Despite being blessed with an intriguing design, a clear vision, and the significant industry wisdom of Dave’s father, Steve Clark, who ran dinghy builder Vanguard from 1985 to 2007, the company still launched into a nightmare.

Fulcrum started building boats as a client at USWatercraft (see “On Hallowed Ground,” PBB No. 147) in April, 2017, just about the time that company financially collapsed. By August, Clark had taken over payroll and supplying materials for the UFO builds and was working with the USWatercraft receiver to keep a roof over the project in increasingly tenuous circumstances. The good part of that experience, he said, was securing his core crew of experienced composite boatbuilders from those being laid off from USWatercraft. The bad part was not having control of a secure shop and reliable material supply as the crew worked to make the refinements to production he knew would be necessary for the UFO model to become a viable business.

Aaron Porter | Professional BoatBuilder Magazine

Clark and Diogo clean up the freshly cured deck part after pulling the silicone bag. The dark stick shapes are wands of cured resin that remained in runners that did not fully collapse after their feed line was shut off.

“The collapse of USWatercraft did a number on us because we were in a really nascent state,” Clark said. “ The second we went independent we were fundamentally better off.” Through a combination of good fortune and good family he was able to lease the 5,000-sq-ft (464.5m2) shop Fulcrum is in today when his cousins’ company, Moore Brothers, then combining with Jeff Kent’s Composite Solutions Inc., secured the larger Franklin St. facility that houses it. The shop had been the composites training program facility for IYRS (International Yacht Restoration School), which the school was consolidating to its campus in Newport. So, after building 40 boats at USWatercraft, the Fulcrum team walked into its own space already optimized for composites production.

In practical terms, this was when the company became a company. The facility is not huge given the volume of work and materials it houses, but Clark takes pride in the efficiencies the team has harnessed to make it work as a production shop.

“A lot of the stuff we need to stock is pretty small,” Clark said. For instance, they get the aluminum foil struts 150 at a time from Vitex Extrusions in New Hampshire and store them on shelves on the mezzanine. Similarly, they get 50 boats’ worth of carbon/glass boom sprits at a time. The masts are off-the-shelf 40%-carbon 15 (4.6m) windsurfer poles sourced from a manufacturer in China that mass-produces them and has been a reliable supplier.

Also up on the mezzanine is a minimalist rigging bench with a fixed hot cutter for rope and a handful of turning hooks set for specific line lengths that allow the operator to double the rope back toward the source, sometimes making multiple turns, to make the cut, thereby requiring only a short bench to measure and cut long lines.

Beyond Infusion: Specializing and streamlining

Back on the shop floor, Clark demonstrated how the jigs for fitting mast and boom include kitted hardware and attached hand and power tools to accomplish each task, and it all stores entirely out of the way when not in use. Also, a CNC-cut plywood jig for fitting hardware to the hull includes containers of the necessary hardware, power drills and drivers fitted with each necessary bit, and allows the boat to roll up 90° to a stable secondary position to fit components on the underside.

Aaron Porter | Professional BoatBuilder Magazine

Mobility of jigs allows for flexible and efficient use of the shop’s limited floor space.

Other specialized jigs on the shop floor are for installing internal foam and bonding the hull and deck parts. In addition, there’s space for the minimal finishing required, mostly fixing any gelcoat flaws after demolding, applying gelcoat to the exposed edge of the simple hull-to-deck joint, and buffing reworked areas. All this is simplified by the fact that white is the only color on a UFO.

In explaining the unique racks that store multiple finished boats standing upright on their bows, Clark recalled how an accumulation of 16 hulls awaiting shipment to the United Kingdom drove him to create a custom CNC-cut solution. Not only do the hulls take up less space in upright storage, they can also be accessed individually without disturbing boats stacked on top. “Our boats don’t look like any other boat, so why would our inventory management look like anybody else’s?”

Aaron Porter | Professional BoatBuilder Magazine

Custom CNC-cut racks efficiently and accessibly store the finished hulls with their sterns in the air and bows down.

Management of composite materials is minimal: a couple of racks and an adjacent cutting table at the back of the shop for laminate materials, and the barrel of resin that’s in current use. Clark credited supplier Composites One, which has a warehouse in Bristol, for Fulcrum’s ability to reliably have just-in-time delivery of composite materials, the single most expensive element of the boats. “We get a barrel of resin every two weeks, a roll of glass every week, and a roll of core every week and a half.” While the resin is used by only one other builder that he knows of, Clark said Composites One knows he will be buying it regularly, so they can talk to the manufacturer in Texas to assure that the supply is steady without requiring Fulcrum to buy 10 barrels at a go and store them in nonexistent shop space.

One element that seems out of scale on the shop floor is a 5,500-lb (2,495-kg) 2001-vintage Motion Master 3-axis CNC machine in its own dust-controlled booth. The bulletproof old machine was state of the art when it was manufactured, but is affordable and still superreliable now.  “I acquired the CNC machine kicking and screaming,” Clark said. “But we couldn’t get anyone else to do work for us because there are too many jobs for the sector right now. I had to become a machinist in order to supply the shop with tooling.” The machine’s weight and powerful 9-hp spindle mean that it can easily cut synthetics or aluminum.

Aaron Porter | Professional BoatBuilder Magazine

The large and venerable 2001-vintage Motion Master CNC machine gives the shop capacity to fix many production problems on-site. Here, it is cutting rig components.

While the CNC might not always be in motion, Clark said its value is in its capacity to reliably meet demand and help solve problems in-house, as well as do some contract work for other builders. “If you have everything maxed out all the time making stuff you don’t necessarily need, you are actually trapped,” he explained.

Like an attentive physician, Clark monitors the vitals of his small company. He recalled that for the first couple of years it was push-feeding, with each area producing at maximum capacity and pushing components down the line. “That means the outputs get out of whack with each other,” he said. “We were good at building hulls but not booms and masts; the foil press was hugely efficient.”

Aaron Porter | Professional BoatBuilder Magazine

Michael Cassata places the laminates in the two-part foil mold that will be cured in a press.

But with limited space to store inventory, the mismatch was leading to a logistics problem. He switched the production model to a pull feed, where actual demand for a part or component would trigger its production. In the transition period last spring, he realized they had enough hull and deck parts stockpiled to shut down the infusion line for about two months without breaking stride. “I had an opportunity we’d made by accident,” he said, an opportunity to take more than a chip shot at cleaning up UFO infusion. It was time to try some changes he’d been planning for two years.

The Silicone Transition

Reusable silicone bags for infusion have been at least a theoretical solution for upward of two decades, but their success has been largely confined to small parts. “It has been in demo mode for 20 years,” Clark said. He recalled that his father had successfully used silicone bags on the Vanguard 15 (4.6m) production starting around 2000. And Pearson built tin-cured silicone bags for infusion of its larger Alerion in the 1990s, when the technology was in its infancy. While Clark wasn’t there, Diogo was.

“Tony has been to this party before, and it didn’t go well,” Clark said. “In a production environment, those tools did not last, and the guys operating the tools got blamed.” Diogo’s skepticism about silicone was a good foil to Clark’s enthusiasm as they planned the changes at Fulcrum last summer. “They’re expensive and they rip,” Diogo warned Clark.  “I know. I ripped them.”

Looking at the technology Pearson had used was instructive. The bags had been embossed to imitate flow media, which gave them a coarse profile, multiplying the surface area considerably and requiring peel ply to release. Even then, they tore repeatedly in service, Diogo recalled. Clark set out to make a different bag that would release easily and, by incorporating the runner design he’d been perfecting, eliminate the need for flow medium and most peel ply. Adding to the experience already on the team, he turned to Jeff Reber at Composites One and his friend Rob Brooks, then at North Shore Composites, for advice.

Aaron Porter | Professional BoatBuilder Magazine

During infusion, Clark points to the advancing resin front and a pleat in the bag caused by swelling of the silicone after the bag was built.

The collective wisdom pointed to platinum-cure silicone as the best, most durable material for the bag. And some testing with attachments for hoisting loops revealed that linen fiber was most compatible with the silicone. Clark likens it to the attachment of tendon through flesh; it adds tensile strength and is less likely than other materials to pull out when the gantry is lifting the 160-lb (72.6-kg) bag.

Next, the molds for the hull and deck parts were buffed to 2000 grit and faired in some areas to minimize bridging and to let the bag release well. “I then carved the runner profiles, the air perimeter profiles, and the vacuum perimeter profiles on the CNC machine. Then installed them and had to fair in the interface,” Clark said.

When they were ready to apply the silicone, Reber loaned him the spray gun and gave him a tutorial on its use. Their goal was to make the bags in one shot—no secondary bonds or heat guns involved.

“Awful!” was Clark’s description of his experience spraying silicone. He said the gun laid it down in an almost pebbly layer, which the full crew, plus Steve Clark, was called on to manually work into as even a layer as possible using squeegees and foam brushes. (Clark warns against using the latter, as they absorb a lot of silicone that gets thrown away.) He said the crew worked the surface in waves as the material started to coagulate in about 20 minutes, and then they’d move to a newly sprayed section. Material can be successfully added to the bag surface in an 8-hour window. It’s necessary to eliminate uneven surfaces, as they are stress risers that will make the finished bags more vulnerable to tearing. Clark said the narrow bow sections especially were a chore. The crew had to keep circling with squeegees and more silicone for a full day to get them right. In the end, they applied about $10,000 of silicone to finish the two bags.

Clark explained that in making the silicone bags they included some mesh around the perimeter and in way of the resin channels. He stressed that these are not really tensile reinforcement but rather silicone traps. “You’re actually just creating thickness in that area,” he explained.

Aaron Porter | Professional BoatBuilder Magazine

Visible through the largely unreinforced translucent material, linen fibers effectively reinforce the lifting points for the heavy silicone bag while minimizing the risk of tearing out.

As awkward and inelegant as the silicone bag build seemed to the Fulcrum crew, it was their first time spraying the material, and Clark conceded that it will be far easier next time they do it. (He hopes that won’t be necessary for another 300 boats, or two years at current production rates.) His chief disappointment with the material was revealed after the bags were in service. He noted that the silicone manufacturers were not forthcoming about the tendency for silicone to expand or bloat as it takes on styrene. “Our bag is now stable, but we have a big pleat down the center,” Clark said. As a result, the careful fitting they did to limit bridging in some areas has been for naught.


Aaron Porter | Professional BoatBuilder Magazine

The clean inner surface of the cured deck part clearly shows the carbon laminates in the beam structures and the even compaction across the full laminate expanse.

By the time of my visit, the Fulcrum crew had fully adjusted to using the silicone bags. “They have to be pulled when it’s hot,” said Diogo. According to Clark, that’s “two hours after lamination, and if time is accelerated on account of heat, you pull it off in an hour and a half.”

Leave it on too long, and you risk more bloating and possible tearing. But the upsides to production are substantial. “One guy can make a hull a day with this system,” Clark said, as long as there’s someone else kitting the laminates. He added that if he needed to maximize production, they could turn out six a week with the silicone bags. With the old system, that would have required investing in another full set of tooling and likely a larger space to operate in. Clark said by his calculations he’s bought a 40% increase in production capacity without buying new molds. And that’s before he even thinks about the dumpsters he’s not filling every week.

One of the trade-offs is that the shop-floor jobs are less forgiving, and the skills required of his crew are higher. But he welcomes the change in materials and mindset.

“The fact that the engineering task has got more sophisticated is exactly right,” he said. “We’d rather express skill, use technique, and affirm capacity to do things right, rather than throw cash at materials.”


About the Author: Aaron Porter is the editor of Professional BoatBuilder.