Victory without resistance

It's no news that the supermaxi scene is becoming increasingly competitive. Owners who have their yachts optimised for regattas want to win. To this end, the large sailing formats are analysed in detail during the design phase. Engineers and hydrodynamics specialists use towing tank tests and complex speed prediction programmes to check all parameters that influence speed and filter out the combinations with the greatest speed potential. A great deal of performance can be gained by reducing hull resistance in particular. The fewer appendages (rudder blades, keel fin, keel bomb, propeller shaft, propeller) a yacht has, the faster it sails. What began with the introduction of folding propellers, which fold backwards in a hydrodynamically favourable manner under sail, is now being taken to the extreme with completely retractable drive trains.

For the owner of the 46-metre Germán Frers design "Unfurled", who is very experienced in racing and sailing, the Vitters shipyard developed a propulsion system together with the Dutch thruster experts from Hydrosta consisting of two thrusters that can be hydraulically retracted into the hull and can each be turned outwards by 90 degrees when extended. In this way, they replace a conventional stern thruster during harbour manoeuvres. Two Scania diesels with 368 kilowatts each transmit their power via ZF500 gearboxes to the two towing propellers with a diameter of 1050 millimetres and guarantee "Unfurled" a top speed of 14 knots under engine power. The cruising speed is an efficient twelve knots.

According to the Hydrosta engineers, the thrusters swing out of the hull at the push of a button up to a speed of ten knots and back again if required. If "Unfurled" sails faster, the propellers remain extended. A flap closes the opening from which the drive units are lowered flush with the hull. The fact that the 255-tonne "Unfurled" can sail fast was proven at her regatta debut during the St. Barth Bucket. There, the Frers design with Oliver Stirling interior celebrated a brilliant racing debut and won the "Les Gazelles des Mers" class as well as the overall classification.

It is hard to say how much influence the submerged drive system has on this performance. In any case, the owner is happy with his new yacht and the regatta success. After all, that and the fun on the way to victory are what counts ...