SuperYacht Times visited Heesen shipyard recently. With a tour at Heesen the projects 17470 and 17255 featured the Fast Displacement Hull Form (FDHF).
The innovation was designed by Van Oossanen, and is so called because the hull does not rely on the development of hydrodynamic lift for efficiency, but stays in displacement mode.
This is a hull form that, compared to a hard-chine hull form, is 30% more efficient at cruising speeds and 15% more efficient at high speeds. In comparison to traditional round-bilge hull forms, significant improvements were also obtained both at cruising speeds and at higher speeds. Model tests confirmed these results and also revealed that a hard-chine hull form is only more efficient than the FDHF counterpart at fully planing speeds.
The final project SuperYacht Times had the privilege of viewing was the first yacht of a 42 metre series for Heesen Yachts, featuring the first application of the Hull Vane. Also designed by Van Oossanen Naval Architects.
The Hull Vane consists of a foil positioned below the hull of a ship or yacht in a specific location by means of struts or sponsons. The device changes the pressure distribution on the hull thereby reducing the resistance. The foil also generates a thrust force. Studies for a number of displacement motor yachts have resulted in fuel savings of up to 25% and averaging 20% over the total speed range.
Hull Vane also reduces the motion and acceleration of the yacht in heavy seas due to the damping effect of the foil below the hull. When the bow pitches upwards on a wave the foil produces an opposing upwards force at the stern, and vice versa when the bow pitches downwards into a wave trough.
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