Solid woods and hybrid propulsion. A mixture of classic materials and modern technologies is taking shape in Italy, under construction by Castagnola Yacht in Lavagna. A project whose creators include Renzo Piano and Olav Selvaag, while Nauta Design and Francesco Rogantin were responsible for the design.
Raft 24m, the boat according to nature
Zattera 24m is a project born from some of the most prolific minds in the world of design, architecture and boating. The goal is to create a unit that allows people to experience the sea in total harmony with the surrounding environment, thus quietly and with as little impact as possible, from construction to use at sea. It is no coincidence that the material chosen in this case is wood-“the most ecologically sustainable,” says the shipyard-which in this case takes essential forms for the simplest possible hull. The boat was then designed with a low freeboard and significant beam.
Zattera 24m, Nauta Design reports, was created for cruising, with a glazed deckhouse as the superstructure for maximum contact with the outside environment. In this way, in the roadstead, one can enjoy sea life to the fullest.
24m Raft – The Materials
This motor boat, given its materials and structural simplicity, is relatively lightweight. Zattera 24m is made by the Castagnola shipyard in Lavagna, Genoa, with solid woods glued with silica-filled epoxy and marine plywood. It is definitely not a fast craft, and the displacement hull reaches 12 knots maximum speed and 10.5 knots as cruising speed. CFD studies performed on the water lines enabled optimization of bow shapes and stern outlets to make drag as low as possible. The result is a distinctive hull that required the use of a laminated iroko keel beam and counter keel of varying sizes, which increase in the bow wheel area.
From the pictures you can see the special shape of the bow, which because of the features listed above, will be made of molded wood, with five different layers of wood, arranged with crossed fibers.
All frames are solid ash, the bottom planking and sides are marine plywood, as is the deck (the latter in okoune’, to make it lighter). The internal structural bulkheads are made of wood with rubber and cork to dampen vibration and reduce noise as much as possible.
24m Raft – Propulsion
To try to have as low an impact as possible, the choice fell on a hybrid powertrain, developed by Siemens Energy. Navigation in 100% electric mode with lithium-ion batteries will also be possible with this configuration.
The propulsion system is powered by two 180 kW variable-rpm diesel generators and a 95 kWh battery pack, connected to a 700 Volts DC distribution system, which supplies both propulsion and other on-board utilities.
Propulsion consists of two conventional shaft lines driven by permanent magnet motors of the high-torque type, each with a power rating of 135kw.
The motors are directly connected to the shaft lines without the interposition of marine inverters to increase system efficiency and further reduce the noise of rotating mechanical parts.
The two diesel generators were developed by Mase Generators for Siemens Energy with Volvo Penta D4-300 Engines using variable speed technology with permanent magnet alternators in order to minimize fuel consumption and emissions.
The generators are installed on a double set of vibration dampers to reduce noise impact as much as possible. For the same purpose, work was done on the materials that make up the soundproofing box of the generators themselves. An in-depth study related to the soundproofing of the engine room was carried out. Finally, the development team is working on having a silent submerged exhaust system. On board are photovoltaic panels that will enable an additional cost- and impact-free energy source.
24m Raft – Interior
Below deck, being a cruising vessel, Zattera 24m was developed with an owner’s cabin, two guest cabins forward and a crew area with an engine room aft. The interior design, in keeping with the general philosophy of the boat, is sober and clean.
The salon in the lower deck is directly connected to the deckhouse by a double transverse staircase. Thus, natural light illuminates all the interior rooms from outside through a skylight right above the hall itself.
Renzo Piano and Nauta Design, with their sailing background, envisioned a series of masts and bigos that will be used to embark and disembark the tenders, hoist canopies and the bow and stern tents. The shape, reminiscent of a sail, a passion common to both, serving a practical function.
