Wooden-hybrid yacht Zattera in-build


An all-new wooden 24m yacht Zattera is under construction at Castagnola Yacht in Lavagna, Italy. The vessel is the idea of Renzo Piano and Olav Selvaag, with design and construction assistance from Nauta Design, Francesco Rogantin and Siemens Energy.

Zattera’s hull, deck and superstructure has been constructed in marine grade plywood wood that has been treated with silica-infused epoxy resin. The yacht has a wide beam at 7.2m, however the central deck area remains covered by a transparent glass superstructure.

The yacht has a displacement hull that can navigate at up to 12kns with a 10.5kn cruising speed. Computational Fluid Dynamics (CFD) testing enabled designers to get a bow shape with good sternwards flow and reduced resistance.

Siemens Energy has engineered the hybrid propulsion system. Careful attention was dedicated to eliminating vibration and sound pollution, said the designers. Zattera has lithium-ion batteries and can navigate in “silent mode” under electric power only. The propulsion and the craft’s onboard functions run on two180 kW variable RPM diesel generators and a 95 kWh battery pack connected to a 700 Volt continuous distribution system.

Zattera has a traditional shaft drive run via twin 135kw permanent magnet motors that are directly connected to the shafts without the use of inverters to increase the efficiency of the system.

The diesel generators were purpose-developed by Mase Generators for Siemens Energy with Volvo Penta D4-300 motors using variable speed technology with permanent magnet alternators. The generators are also installed on a double anti-vibration pad. Even the underwater exhaust system is undergoing sound testing.

The Castagnola shipyard said solar panels will be mounted on Zattera to create a zero impact and no cost renewable energy source.

The unusual hull shape called for a keel beam and a counter keel in cold-moulded iroko wood that get larger towards the bow. Given the particular shape of the bow all of the wood planking in that area is crafted using five different layers laid cross grain to each other. All frames are in solid ash while hull planks are in marine grade plywood.

The interior layout has the owner’s and two guest cabins at the fore and the galley, crew area and engine room aft. The saloon in the lower deck is directly connected to the coachroof via stairs.

Aboard Zattera the designers have incorporated sailboat features such as masts and derricks that will be used to load and unload the tender and to set up awnings fore and aft. While functional, these elements also recall sailing, something Piano and Selvaag wanted to achieve with the yacht.

At a glance: Zattera

  • Length: 23.96m
  • Beam: 7.2m
  • Draft: 1.2m
  • Top speed: 12kns
  • Cruise speed: 10.5kn
  • Power: Lithium ion batteries and two Volvo Penta D4-300
  • Capacity: 4 guests + 2 owners
  • Interior design: Nauta Design
  • Naval architecture: Names by Francesco Rogantin
  • Hull construction: Castagnola Yacht
  • Hybrid propulsion: Siemens Energy