27 Power Box (the latter including the DC fast-charging connector). Thermal readings from the motor, inverter, battery modules and ambient water are used by the eVCU to calculate cooling pump speeds. For the drivetrain circuit, water-glycol runs from the pump into the inverter first and then into the motor. The two circuits are completely separated save for an expansion tank. In addition to the two pumps there is a third one, which the team refers to as the seawater pump; it typically sucks water and propels it onto a pair of water-to-water heat exchangers. The water-glycol internal coolant runs inside those, with each heat exchanger carrying one of the two aforementioned cooling channels, so the heat from those runs into the heat exchanger, into the water and hence into the lake/sea. Helmberger adds: “That pump draws water from three apertures in the Z-drive to ensure consistent thermal management, even during high planing. Our hull is a stepped hull, which means a lot of air can pass under the hull when the boat picks up speed. Placing the water aperture elsewhere could mean less cooling and more heat losses at high-power outputs.” While the powertrain is configured to manage a refrigerant cooling circuit, as in the next-generation Porsche Macan, a standard water-glycol system was chosen for efficiency, as well as the availability of parts. In addition to that cooling system, the BMS monitors at cell level for where currents and other parameters can be controlled for thermal stability. Porsche found no modifications were needed for the BMS to transfer from the Macan over to the eFantom. Hull construction The outer hull is unchanged from the 858 to the 850 eFantom, and hence it has the same hydrodynamics, which have been optimised as a compromise between the gentle cruises and short bursts of speed expected from its user requirements. The internal hull, however, was modified to accommodate components such as the battery, which Helmberger notes has a layout completely unlike the 858’s fuel tank, engine, or both combined. “The fuel tank, for instance, is usually situated behind the seating area and below deck, and is built with a vee shape to conform with the hull and keep the CoG as low as possible,” he explains. “So, while Porsche couldn’t use the engine or tank compartments, there was a space under the deck floor, typically used for storage or just left empty, and that’s now used up by the battery. “To also accommodate the battery, we put stringers made out of GRP [glass-reinforced plastic] to precisely house-in the pack. Those kinds of stringers are normally used to mount and damp the engine and fuel tank, and to prevent them affecting the stability of the hull, but we modified the stringer arrangement heavily to integrate the battery. That included making them less high up, smaller and closer together for less empty space, to provide the same hull stability, because we’re going roughly the same speeds as we do with the 858’s highest-power petrol engine.” The rest of the hull is also predominantly GRP (aside from some leathers and woods chosen for aesthetics in the passenger area), with an anti-fouling coating on the outer hull below the waterline, as standard among boat-makers. “To construct the hull, we start with a negative mould made of the same material,” says Helmberger. “The first component into that mould is the anti-fouling coating, and then each layer of GRP is laminated into that by hand. After laying those, the mould and hull are heated and cured to finish, and the piece is finally removed via air pressure from the mould. “Lastly, the shell coating gets sanded down to a precision finish for hydrodynamic shape, symmetry and aesthetics – a very labour-intensive process – and then the hull is styled in marine paint, according to customer requests, with typically 11 layers of paint for the ideal finish.” Firm future In addition to the first commercial deliveries starting this year, the boat was displayed in its first major public event showcase at Boat Dusseldorf in January. Both companies were present and discussed technical aspects of the boat with the industry and market. Porsche declined to comment on the exact or potential number of eFantom units to be produced, but it emphasised that its collaboration with Frauscher thus far has been intended to establish a functioning business model to carry into the future, and it will not be simply a one-off collaboration in the history of e-mobility as it is written. Key specifications and suppliers Frauscher x Porsche 850 Fantom Air (or eFantom) Powerboat Battery-electric Dry weight: 2,800 kg Length x width: 8.67 x 2.49 m Clearance height: 1.35 m Draught: 0.5 m with trim raised, 0.9 m with trim lowered Maximum continuous power: 170 kW Peak power: 400 kW Energy capacity: 100 kWh Maximum speed: 85 kph (46 kts) Cruising speed: 41 kph (22 kts) Maximum range between charges: 45 km at cruising speeds and over 100 km at displacement speeds Endurance between charges: two to three hours, depending on driving profile Driver interface: Raymarine Z-drive: MerCruiser Hull design: Kiska E-Mobility Engineering | March/April 2024 Frauscher x Porsche 850 Fantom Air | Dossier
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