Heesen Yachts has revealed further technical details of its 80-metre Project Cosmos currently in build with exterior styling by Winch Design and interiors by Sinot Exclusive Yacht Design, and announced completely new projects.
Photo: Heesen YcahtsProject Cosmos began when Mark Cavendish, Heesen’s Director of Sales and Marketing, received a call from the owner’s representative with a brief for a yacht capable of speeds close to 30 knots. “Aware that the yard had already built two large, high-speed, all-aluminium yachts – Galactica Star and Galactica Super Nova – they were looking for something very special indeed,” says Cavendish.
At 80 metres overall, Project Cosmos is 10 metres longer than Galactica Super Nova, Heesen’s largest launch to date, but more importantly at 1,700GT she has around 50 percent more interior volume. Combining her size with such high speeds represented a challenge on numerous fronts, not least ensuring that she will be able to pass under the various bridges en route from the shipyard in Oss to the sea – a tight squeeze at the best of times. 
Photo: Heesen YcahtsThe Heesen team approached Van Oossanen Naval Architects to fine-tune the technical details. To be fast Project Cosmos had to be light, and it was obvious from the start that the yacht would have to be built of aluminium and take advantage of van Oossanen’s Fast Displacement Hull Form. Four MTU 20V 2000 engines, two driving each prop shaft, will deliver a total of 3500 kW each (representing a total of about 19,000 hp) to the twin controllable pitch propellers. At top speed all four engines are engaged, but at moderate cruising speeds the yacht can drop to a more fuel-efficient two-engine mode.
In another first for Heesen, the decision was taken to install Rolls-Royce Promass rudders that further improve propulsive efficiency and manoeuvrability by combining the rudder and propeller into one hydrodynamic unit. The rudder itself has a twisted edge that optimises the flow from the prop so that some of the swirl energy normally lost in the slipstream can be converted into forward thrust, resulting in a 2-6 percent gain in efficiency.
Photo: Heesen YcahtsAs the propulsion package alone weighs around 52 tonnes, excluding the gearboxes, the far trickier challenge was how to achieve the structural strength required without adding too excess weight to the aluminium structure.
“Aluminium is quite flexible and while there are a couple of 80-metre-plus aluminium yachts out there, none of them are required to do 30 knots when the loads at work on the full and superstructure are considerable,” says Perry van Oossanen. “To accurately predict these loads we developed a towing tank model in four separate sections, so we could measure the bending and torsional loads on each section. A boat of this size and speed has never been built before, so we couldn’t rely on what Lloyd’s told us because there are no precedents.” 
Photo: Heesen YcahtsTo increase structural rigidity, Van Oossanen and Heesen has introduced an innovative method of construction, currently being patented, which they call the ‘Backbone’, consisting of three very stiff L-section girders – one in the keel and two where the hull meets the deck – to deal with the bending moments. The hull plates themselves are not structural, but help to absorb the torsional loads.
Mark Cavendish also announced other new projects, including a 57-metre, all-aluminium yacht with a gross tonnage of around 800GT capable of 21 knots designed by Frank Laupman of Omega Architects.
Photo: Heesen Yachts
Photo: Heesen YcahtsBut completely new territory for Heesen is the brand’s first explorer yacht. Also measuring 57 metres overall, she will be built of steel and have a massive volume for her size of 1,400GT. Styled by Winch Designs, the yacht will feature all the ‘off-road’ features expected of an explorer vessel, including long-range, robust construction, helipad capability and storage space for multiple tenders.