Marlow Explorer 86 CMYBy Capt. Grant Rafter
In David Marlow's hands are two coffee stirrers buttressed at either end with the lids from our large Styrofoam cups. "You see," he explains as he leans his elbows on the granite countertop in the galley of the Marlow 86, "these lids represent the Kevlar skins..." As the owner and founder of Marlow Yachts begins his explanation, I sip on my coffee and pay careful attention, knowing that he and his company had just attained one of the grails of boatbuilding: full-stack resin infusion.
Resin infusion is the process of laying up fiberglass by using a partial vacuum to suck resin into the porous matrix of a preformed structure. (The main differences between it and resin-transfer molding are the use of a vacuum and much higher pressures on the laminate.) The process has undergone many iterations and acronym changes since its inception nearly 25 years ago, but arguably, the most advanced version to date is the Resin Transfer Molding Vacuum Infusion Process (RTM VIP). It requires a large bag, a vacuum; resin, mat, and coring; and a preformed mold of the structure to be built.
Recent advancements in RTM VIP—such as dramatically decreasing the pressure of the partial vacuum—have allowed resin to better penetrate the matting materials, working deep into the "sprues" (tiny cavities) of both the matting and, when present, the core. This ensures that the proper amount of resin fuses to the preformed structure (an issue that can inhibit RTMs that don't enlist an extremely low-pressure vacuum).
The benefits of RTM VIP over other types of RTM and classic roll-and-mop layups are well documented: It's quicker, forms products that are both lighter and stronger, and produces less waste. When you remove the bag, the part is basically finished—almost no need for grinding, sanding, or painting.
Until now RTM VIP worked much better on smaller parts, like hatches and bulkheads, where bagging is more manageable. Some bigger hulls had been formed from this process, but only in stages. Builders of large yachts had to form the outside skin, then add the core, then add another skin. But Marlow Yachts has changed that.
It patented a process called Resin Infusion Vacuum Assisted Transfer (RIVAT), which is basically a souped-up version of RTM VIP (the details are proprietary). David Marlow states his is the first company to reach the goal of "full-stack" infusion of an entire hull of more than 80 feet; that is, infusion where the outer skin, core, and inner skin are all laid up in one mold at the same time. For Marlow Yachts that means that the resin has to fully penetrate the seven to nine layers of engineered laminates and two layers of Kevlar that comprise the outside skin, two 11⁄4-inch-thick Corecell foam layers sandwiched in the center, then another seven to nine layers of laminate and two more layers of Kevlar that form the inside skin. Marlow Yachts manufactures the 86 in three main parts: the hull, superstructure, and bridge deck. The superstructure and the bridge deck are also laid up using RIVAT; the core formed from E-glass, S-glass, and selected carbon fiber is filled in afterwards.
Full-stack infusion increases laminate strength in two ways: It yields a structure that is one solid piece without seams or holes to weaken the laminate, and because it is completely enclosed, it eliminates the chance of contamination from airborne particles, like shop dust and chemical sprays, that can weaken the layup.
Marlow Yachts also attempts to build a stronger product by being picky about its construction materials, from the matting to the resin. It opts for stitched (i.e., latticed, knitted) matting instead of woven. Although woven may seem stronger in theory, when uneven pressure is applied to its threads, they may spread into the crimps between the weave; layered rovings, on the other hand, stay put. This keeps the hull from developing weak points.
Since full-stack infusion creates such a burly product, the 86 requires no bulkheads for structural support (the two watertight ones are there to meet Bureau Veritas safety standards). And although this freed the designers to play with the layout, they still opted for a rather traditional configuration.
One fixture found in every crew cabin and guest stateroom—others include beveled English mirrors, gold faucets, and LCD TVs—are 12"x8" dead ports, and there's something about them that relates to full-stack infusion. They're recessed into the hull, and their mounting flanges are attached to a lip that's fashioned in the mold instead of embedded in aluminum or plastic frames that were inserted flush with the hull side. Every window is attached this way. The method requires less build time—the windows need only be secured with sealant—and produces a stronger mounting that doesn't have to accommodate the hull's curves.
And that's just one of the timesavers built into the 86's mold. Perhaps most impressive are the conduits that run throughout the vessel, which carry all wiring, hydraulic hoses, and plumbing lines. And at every junction and sharp turn, there's an access panel—grain-matched if appropriate and secured with latches instead of screws. Open the panel, and you'll see every wire and hose properly labeled and color-coded; the key is displayed on the forward engine-room bulkhead for hoses and on the wheelhouse distribution panel for wiring. This saves time when installing a part or tracking down a problem.
But building these conduits and everything else into the mold of the 86 wasn't easy. "I had a lot of sleepless nights leading up to the infusion," Marlow admitted. It's no wonder: There were no second chances. If something big had gone wrong during the 36-hour infusion process, the entire section would have been useless, and all of the money would have been lost. For Marlow, however, the cost of being able to lay up a boat in seven days versus seven weeks, coupled with all of the other advantages of his RIVAT process, made it worth his while.
Yet success did not translate into a speedy build. Our boat took one year from layup to delivery. Marlow Yachts spends the time it saves on infusion on details such as woodwork. All of the wood onboard is not only teak, but also hewn from a single Burmese log measuring 40 feet long and four feet in diameter. To ensure that the roughly 6400 board-feet contained in it would be sufficient and also meet Marlow's quality standards meant a lot of planning before the saws began to turn, especially since the sole is grain-matched, as are all of the cabinets, paneling, and coamings. Most of the tree ended up in the boat, as even its burls and wild grain were used as decorative end caps. Scraps were enlisted for out-of-the-way and hidden features such as trim on the inside of drawers, but that doesn't mean the quality of the finish was diminished. The teak shower grates have 20 coats of varnish, as do both the grates in the line lockers in the bulwarks on either side of the Portugese bridge and those that stand in for diamond plating in the engine room. Like Marlow says, "Finish it like you're proud of it." When he shows me the varnished trim of an access hatch hidden under the mattress in the VIP berth, I can only shake my head in disbelief.
As we go through the vessel dockside, it becomes clear to me that the 86 is a sound and comfortable vessel. But I know that that would matter only if she performs well. Unfortunately, once we get her off the dock and into the waters of Terra Ceia Bay, the one- to two-foot waves don't allow a test of her seakeeping ability, although performing three to four boat-length loops with the wheel hard over raises some four-footers that slip unnoticed under our bow. The main reason for that radius—still quite good for an 86-footer—appears to be the twin Veolcijet strut keels, another patented Marlow design, that stick down like an A near the stern to add stability and to protect the shafts housed within them. The design imposes no such resistance for dockside maneuvering. With the wheel centered and engines opposed, she spins slowly but within her own length, and adding a little rudder accelerates her at a controlled and predictable rate.
Standing on the flying bridge, I feel exhilarated and completely in control behind the wheel; she is both fast and easy to drive. I feel I could take her anywhere, and with over a 1,300-mile range at 19 mph, I'm pretty sure the new owner will do just that. And wherever he takes her, he'll have the knowledge that she can handle it because she's built tough. She's definitely a boat that fits the passage-making mold.
For more information on Marlow Yachts, including contact information, click here.
When I asked David Marlow about the advisability of placing a pulpit on a 90-foot boat, he explained that inside the pulpit were thin plates of steel, bolted together, and stacked vertically like long business cards in a box.
An even more important part of the design is the chain stowage, which is not in the foc'sle but 14 feet farther aft and nine feet farther down; basically under the VIP's queen berth. This puts the ten-pound-per-foot chain below the yacht's longitudinal metacentric height, so it acts as ballast in a seaway instead of adding to pitching. Another smart move: The "mud-hog" pump that flushes the chain-wash residue overboard can double as another bilge pump.—G.R.
This article originally appeared in the June 2008 issue of Power & Motoryacht magazine.