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Modern Boatbuilding - page 2

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By Alan Harper

A machine mills deck components at Azimut.

“The resin-to-fiber ratio is key,” Spooner adds. “You want to use as much fiber as possible, and we pack in a lot, consolidating the fiber down within the vacuum process before introducing the right amount of resin, delivering maximum strength for minimum weight.” He points out, perhaps surprisingly: “Our process is not quicker, or cheaper—it’s simply better.”

But even before the resin enters the scene, builders are careful to focus on the amount of glass. “We use Gerber numerically controlled [NC] fabric cutters,” says Stephen Heese, president of Chris-Craft in Sarasota, Florida. “NC cutting of glass insures the desired strength of the completed parts: Because they’re cut on a machine, the pieces are of uniform dimensions, and we know that the correct amount of fiberglass was used in each part. When the part is completed and pulled from its mold, it is weighed, and its weight confirms that its glass-to-resin ratio is within spec. If you get the correct amount of glass and resin into the mold, the strength of the finished part is guaranteed.”

The human touch checks the robot’s work.

On Germany’s Baltic coast, meanwhile, the Hanse Group builds six brands, power and sail, ranging in size from 18 to 75 feet. Having recently acquired Sealine, the company has just transferred production from the U.K. to its factory in Greifswald. 

The company builds about 600 boats a year, and takes the concept of mass production very seriously: All interiors are built using modular assembly principles which will be familiar to anyone who has put an Ikea flat-pack bookcase together. The reason for the modular approach is to keep build time down, and the key to it is digital woodworking, in three computer-controlled, automated cutting mills,each costing about $1.25 million. These deal with Hanse’s 70 varieties of plywood and plexiglass, in different thicknesses, types, and finishes. Processing starts with printing and applying a barcode to each soon-to-be component, which identifies what it is and which individual boat it’s destined for. Then the machine gets to work routing out the pieces. It calculates how to get the maximum number of parts out of each sheet, minimizing waste (plywood offcuts help to heat the factory in winter) and just two people are needed to run each mill: one monitoring the computer, and one stacking the finished components onto trolleys. An automated drill reads the barcode before selecting the correct bits and putting holes where they’re needed. The pieces then roll through an edging machine and a varnisher, which applies a finish of precisely the required thickness, which dries almost instantly under ultraviolet light as the item emerges. Then it’s off to the assembly area. 

Digital automation is making inroads into other areas of boat production. Gelcoat—the first layer of resin applied to the inside of a mold, which becomes the outer skin of the finished molding—was once painstakingly applied with brushes, by hand. Spray application came next, and now at Azimut Yachts in Italy they not only spray it on, they get a robot to do it. The spray head is attached to an articulated arm mounted on a bridge crane, which moves along the interior of the hull mold while the arm ensures an even covering in every corner and crevice.

In fact the Avigliana factory has three robots—a second one cuts the fiberglass mat to the exact shapes required for individual moldings, while a third is used for trimming and drilling the completed components. “The advantages are not just in accuracy and repeatability,” says Azimut technical director Alessandro Rossi. “Using robots can also safeguard the health and safety of workers in high-risk areas.” And manufacturing perfection is not just a nice-to-have sales message—it has a practical benefit for the boat’s end-user: “All the pieces that come out of these processes will match with each other exactly, and therefore create perfect assemblies of components. This eliminates a lot of vibration and noise.”

Plywood interior components are sprayed with a lacquer finish at the Hanse plant, where Sealine yachts are now built.

Quality aside, the other main reasons builders like high-tech systems is that they reduce labor costs and material waste. But just as important, they can also be used to help regulate a boat’s weight. In the old days weight-sensitive craft were put together on a wing and a prayer, and almost always came out heavy. And guess what? They still do. Smarter shipyards—the ones that are thriving—have learned to understate quoted design speeds to give themselves a margin of error. But as boats have gotten bigger and power-to-weight ratios have become more critical, electronic scales are often used at the gangplanks to measure the weight of every worker as he goes aboard carrying something to be fitted, and again as he comes off again, empty-handed. A computer keeps a tally of the difference. 

At Sunseeker International in the U.K. they do that, but also, in the construction of its 155 superyacht, the yard uses a matrix of load cells to provide “live build weight” data. “The hull is held in five cradles,” explains Sunseeker naval architect Simon Barlas. “The front three each have four 20-ton cells, and the aft two—under the engine room—each have four 30-ton cells.” Of course “real-time” weight measurements would include every worker’s lunch, toolkit, and transistor radio, so actual weigh-ins are done once a month, on a Friday, with the boat cleaned out and stripped of everything movable. For absolute accuracy, on four occasions during the build, the yacht is also emptied of all temporary handrails, safety equipment, dust sheets, and temporary lighting. 

According to Barlas, the technology enables the designers to keep track of a hull’s longitudinal center of gravity—it’s less useful laterally—and has proved to be well worthwhile during the builds of the two 22-knot superyachts constructed so far. “On the first 155 the data gave us a warning that the plywood we were using was too heavy,” he explains. “So we switched to a lighter stock, and now we’re using that throughout the second yacht.”

Automation eliminates waste as pieces are cut to maximize each sheet of plywood, and each part is coded and designated for where it will be fit.

It’s a funny thing: the quality of boat construction used to be plain to see. It was there in the dovetail joints, the perfect splines and those beautifully grain-matched dowels, and onlookers could tell at a glance whether a builder or an owner was a man of taste. Today, a modern fiberglass yacht assembled to the finest tolerances in a lab-like shipyard might look much the same, from a distance, as one slapped together by a guy with a roller and a bucket of resin. But get a bit closer and you’ll see the difference quite plainly. Certainly, manufacturing processes have changed over the years and no doubt will continue to change, but quality will never go out of style.

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