Najiba was unusual for Feadship in the sense that her owners had already decided to work with a particular design by Vitruvius Yachts and a specific hull initially conceived by Philippe Briand before they came to the yard. The slender Vitruvius –style lines and distinctive vertical bow are based on Briand’s rich experience with designing fast sailing yachts.
The overall concept is by Philippe Briand/Vitruvius Yachts. Built at the Feadship Aalsmeer yard, Najiba’s naval architecture & engineering is by Feadship De Voogt and Briand.
Najiba has an aluminum hull and superstructure. She is the second largest Feadship to be built in aluminum to date, saving weight and adding to the potential savings on fuel consumption. Her sea trials confirmed that the Vitruvius design paid dividends. Najiba’s average fuel consumption is as low as 3 gallons (11.4 liters) per nautical mile at her cruising speed of twelve knots, between 20% and 25% less than any equivalent motoryacht of this size. The yacht also has a top speed of 17 knots, outstripping the original goal of 16 knots, while her range came in at over 6000nm, more than a thousand over the specified figure.
“These results mean that – despite the complexity of her development and build – we have outperformed all expectations with Najiba,” comments Roderick de Vries, technical director of the Feadship yard in Aalsmeer. “It was a real ‘wow’ moment for everyone involved to see this level of efficiency achieved during the sea trials. It is one thing to design such an efficient full-displacement motoryacht but another to translate these lines and shapes into a stunning Feadship that is even faster and more fuel-efficient than we projected.
“Working very closely with Vitruvius, hull efficiency was the leitmotif of the project from an engineering perspective. It impacted every decision made about appendages like the bow thruster, propeller shaft, stabilizers and main exhaust. We had to strike exactly the right balance between Philippe’s desire to minimize all sources of resistance and the Feadship values of ensuring total comfort for clients, ease of maintenance for crew and the smartest construction. It was a fascinating challenge at times but we have managed to combine the best of both worlds and Najiba is a true Feadship.”
Phillippe Briand and his team were committed to translating the Vitruvius philosophy into a Feadship and to create the most efficient possible motoryacht design. “We leveraged on our decades of experience with sailing yacht designs to optimize the hull lines, proportions and weight of the boat,” Briand explains.
“There are various parameters involved in the resistance of the hull. For example, for a given overall length, the optimum is to have a plumb line bow with a maximum wet waterline. Another parameter is to try and reduce the wetted area— the area of the hull immersed in water —as this has the greatest impact on cruising speed. We also optimized the pressure on the hull and reduced wave drag by ensuring the smoothest possible distribution of the lines.
“At Vitruvius we are used to designing boats in aluminum, which obviously leads to savings in weight and reduces displacement. As the inertia of the boat is less, so too is the wave resistance when underway and the degree of pitching. These, in turn, lead to further reductions in fuel consumption. Aluminum also brings extra benefits in terms of motion comfort, as was instantly perceptible during Najiba’s sea trials.
“Together with Feadship we believe that this project has been a crucial step on the road to greater superyacht sustainability, a path that we expect more owners to follow in the years ahead. Najiba is a genuinely innovative motoryacht and she illustrates what can be achieved when two expert parties share their knowledge and experience to attain a greater goal.”
Feadship’s Naval Architecture Department
Annemarie Steenbergen, who led the team of naval architects at Feadship De Voogt, thoroughly enjoyed the close working relationship with Briand and Vitruvius. “Najiba has a different hull shape from any previous Feadships, showing curvature in all degrees. The hull shape isn’t straight from the waterline up to the main deck. A cross-section halfway through Najiba’s hull shows she is like a half moon, with a smaller beam on the waterline than at deck level. The bow area is also different. Feadships usually have a horizontal keel with the radius in front, especially with straight bows, before rising vertically. Najiba has a raised keel from approximately one third to the bow, resulting in a reduction in resistance without any compromise on maneuverability.”
Feadship already has its own efficient engineering and naval architecture procedures, and the Najiba project proved that these could also be adapted to different designs from different sources. “We received the lines plan in the Vitruvius program and transformed it into our own,” adds Steenbergen. “The hull design was very much Philippe’s but we ensured it could be built according to Feadship procedures and standards. Height stacking was another challenge as the sleek design sought to push the vertical center of gravity down and save weight. We successfully accommodated the smaller distances between each ceiling and the deck above.”
As a technical director at Feadship, Roderick de Vries is impressed with the potential that the Najiba project opens up. “This was the first yacht we had built with Vitruvius so it involved both lots of discussions and building significant margins and tolerance into the system. Any future builds would inevitably see a reduction in these margins.
“Looking beyond the individual parties involved, this project also illustrates how we might move forward with other efficiencies with respect to electric propulsion. The lighter and more efficient a design is, the easier it will become to fit electric engines. One of the key obstacles to using batteries is their power density, which is lower than diesel fuel. If we can achieve a very efficient hull and power consumption, less battery capacity will be required to achieve a given range or speed. Who knows what the future may hold!”
Najiba: Twin-screw motoryacht,
Hull/superstructure construction: aluminum
LOA: 190ft. 3in. (58m)
Beam: 36ft. 2in. (11.m)
Draft: 8ft. 6in. (2.6 m)
Fuel capacity: 23, 775 gal. (90,000L)
Fresh water capacity: 5,812 gal. (22,000L)
Main Engines: 2x MTU 12V2000M72, 1080 kW @ 2250 rpm
Generators: 2x Zenoro / John Deere 185 ekW (400 V, 50 Hz)
Speed (max/ cruise): 16 / 12 knots
Accommodations: Owner/s: Four persons (two staterooms for two owners or guests in each) Eight persons: (four double staterooms)
Naval Architect: Feadship de Voogt and Philippe Briand
Exterior styling: Vitruvius Yachts ltd
Interior GA development: Claudio Cicconetti Architetto
Interior Design: Liaigre