81 its constructor and main integrator, with Sequana Développement coming onboard soon after for key consultation and managing commercial operations of the boat,” says Jonathan Klein Schiphorst, co-founder of Roboat. That autonomous vessel has now been built and is poised to transport Parisians, Olympics athletes and tourists alike starting in the summer. The boat, nicknamed ‘Tony’ as of writing, is a 9 m long, 3.9 m beam, 1.7 m draft, 3.1 m air-draft monohull. It displaces 9.5 t, provides seating for 35 passengers and moves through the water at 12 kph. Movement comes from a fully electric and hence zero-emissions powertrain. Perhaps most unusually, the ferry’s structure and body have been manufactured predominantly from recycled plastic through the use of large-form additive printing. Project history Using the small Roboat autonomous water taxi as a design basis, HSG broadly took responsibility for the mechanical manufacturing and assembly of the boat, including integration of most of the components, with Roboat providing critical input on the sensor- and software-related aspects key to the boat’s autonomy and control. “Our normal process for designing a vessel is something we call a ‘design spiral’. We take into account the requirements for hydrodynamics and structural stability, and lay out steps for specifying and fine-tuning those into a circle, such that we go around the circle, and sometimes we go around again multiple times to really minimise resistance, instability, weight and other key points,” says Tim van den Heuvel, research & development manager at Holland Shipyards Group. “Some key aspects, like the propulsion configuration, for instance, took key inspiration from what the Roboat team already had on its small water taxi, which is very unconventional for medium and larger vessels in that the fixed thrusters are positioned mid-ship on the port and starboard sides, with additional bow and stern thrusters. “It’s more like a multirotor drone than any normal operational boat, but the end result is that the ferry’s reaction time and control response can be faster than regular boats using this propulsion setup.” The electrified aspect of the powertrain was not new to HSG, as the Dutch shipyard had previously built several dozen fully electric ferries. Once the structural and electric parts were installed, Roboat was able to integrate its autonomy-related computers and sensors with the electrical subsystems. Production of the boat began in September 2022, to meet the deadline for submitting the design in the following month. The verdict, in Roboat and HSG’s favour, came in December, followed by official signing of the tender in May 2023 (although HSG began designing and prototyping very quickly, in the week after the verdict). “By May, we had already discussed the idea of 3D printing the vessel quite a bit internally,” van den Heuvel notes. “In the beginning, we had thought to build it conventionally from steel or aluminium, but, given the potential for labour cost and time savings, we thought additive manufacturing could be really interesting. It was a totally new technology and use-case for us, as a shipyard, but that just meant it presented huge learning opportunities, which could be used in the future.” Printing process HSG’s usual design spiral was performed with some additional constraints specific to additive manufacturing, such as the dynamics of printing machines, the forms that the edges of printed parts can take, and the inability to use certain types of extensional forms. “We started looking for largecomponent additive-printing companies, and luckily, in our backyard in Roboat’s 3DFEA USV | UVD Uncrewed Systems Technology | April/May 2024 The ferry is based on Roboat’s water-taxi architecture and built largely by Holland Shipyards Group (Image courtesy of Roboat)
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