Men of Mettle

Of all the skills required to build a superyacht in steel and aluminum, welding is one of the most complex and lease appreciated.

Welders are the unsung heroes of yacht building. Clad in protective helmets, leather gauntlets and heavy suede smocks with sleeves pitted and scarred from white-hot sparks, they look like battle-hardened warriors as they wield welding guns to fuse flat metal plates into three-dimensional hulls and superstructures. Half manufacturing process and half sculpture, welding is what makes modern shipbuilding possible.

Carlos Undijk, foreman at Heesen, has been welding for over 40 years after following his father into the trade at age 17. 

“You need a good eye and a steady hand, but most importantly you need knowledge and concentration,” says Carlos Undijk, the 61-year-old welding foreman at Heesen Yachts responsible for a team of around 15 in-house welders and outside contractors. “You have to understand the behavior of the materials you’re working with, what can go wrong, and be able to focus on the job at hand for hours at a time.”

Heesen uses a process called metal inert gas, or MIG, welding to build its aluminum hulls. An arc of electrical current generates the scorching temperatures required to melt and fuse two pieces of metal. The pieces are connected to a grounded wire, and there’s an electrode of filler metal. When the electrode touches the welding materials, and then moves away, the air between them is ionized. Electrons jump across the gap, producing bright light and intense heat. As the welder draws the arc along the join, both the tip of the electrode and the working materials become molten and fuse together.

In other words, the welder controls a tiny lightning bolt to melt metal.

A gleaming, all-aluminum Heesen yacht is prepared for fitting out in the dry dock.

Heesen Yachts also builds in steel, but the yard is best known for its aluminum construction. However, the same qualities that make aluminum ideal for yacht building—low weight, high strength and corrosion resistance—also present some welding challenges when compared to steel. The melting point of aluminum, for example, is half that of steel. Aluminum also has an oxide layer that is much harder than the metal itself.

“Aluminum has to be thoroughly cleaned before welding to remove the oxide layer, which helps resist corrosion and abrasion but also acts as an insulator that can create problems during welding,” says Undijk, who, as a teenager, followed his father into the trade at the now defunct Chicago Bridge & Iron Company.

“In fact, in Dutch we talk about the three Vs: vet [grease], vuil [dirt] and vocht [moisture],” he says. “But there are so many other variables that can affect quality even before you start welding, from the machine settings and choice of filler wire to the ambient air temperature and humidity.”

Another issue with aluminum is porosity. As the filler material and aluminum base metal become liquid during welding, they absorb hydrogen and hold it in solution. But once the molten materials start to solidify, the gas is trapped in the metal as bubbles, resulting in weaker welds. A shielding mixture of helium/argon gas helps reduce the risk of porosity, but so does avoiding the presence of hydrocarbons in the form of grease and other contaminants. Aluminum oxide that has absorbed moisture by being stored in damp conditions also releases hydrogen when heated during welding (some filler metals are diamond shaved to eliminate any oxides).

A pair of welders at work on Project Cosmos, Heesen’s largest yacht to date.

Shipyard welders face the added challenge of accessibility. Given the design and shape of a hull and its many bulkheads and compartments, they are required to climb into awkward, confined spaces with a welding gun. This is just one reason why the automated welding robots used in the automotive industry have had little impact on custom yacht building.

“Automated welding requires consistent and repeatable procedures,” says Stijn Verleg, shipbuilding production manager at Heesen. “It may work for small series boats or the block assembly of cruise ships, but not for building custom superyachts. We have a tractor robot on rails for welding the straight deck seams, but a person still has to be on site to calibrate and oversee the machine. Given all the variables, manual welding is still the best option for us.”

To streamline the welding process, the aluminum sheets are now milled and data-printed on both sides. 

The job carries risks for human beings. Apart from the danger of electric shock, all forms of welding produce smoke that contains a noxious mixture of metal fumes and gas by-products. Certain gases, such as helium and argon used as shielding gases, also displace oxygen and can pose suffocation risks. For these reasons, good ventilation is vital, and any welder working in an enclosed space such as a fuel or water tank has to be accompanied by a workmate outside.

Recent developments have speeded up the welding process, and, in turn, a yacht’s build schedule. Instead of plasma-cutting aluminum panels, Heesen and other yards now mill them by CNC machine with chamfered edges, reducing the need for grinding in preparation for welding. Information can also be printed on both sides of the plates for faster and more efficient assembly. Including the time taken to prepare materials and equipment, a proficient welder can weld around 10 feet (3 meters) an hour.

Welding requires a good eye, a steady hand, technical expertise and the ability to focus on the job through a darkened visor for hours at a time. 

The classification societies regularly X-ray the welds of new builds to check their quality. In the case of the 262-foot (80-meter) Project Cosmos currently in build at Heesen—its largest yacht to date—the quality checks involve more than 60 inspections and thousands of feet of welds. Only a small percentage of minor flaws is acceptable.

Beyond strength and quality, there is something strangely beautiful about a perfectly executed aluminum seam. A fresh steel weld quickly oxidizes to grimy brown, but aluminum retains its sheen, so the once-molten metal resembles the silvery ripples of an incoming tide as it moves up a narrow channel. This beauty is somehow enhanced by the knowledge that such perfection is so hard to achieve.

“Is welding an art or a science? Maybe it’s a bit of both,” Undijk says. “You need to have a feeling for the materials you’re working with, but perfection is all about experience and technique.” 

This article originally appeared in the Winter 2020 issue of Yachts International.


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