INCREASING HULL EFFICIENCY
TO REDUCE OUR FOOTPRINT
The route to sustainable yachting is long and challenging. With the launch of BlueNautech Heesen is committed to taking first steps to reduce the industry’s impact on our planet. One of the most effective ways to improve fuel-efficiency is through hull design and Heesen has turned hull efficiency into a science.
First-time visitors to the Heesen shipyard will surely remember the moment they pass through the doors from the reception area into shed 1. In contrast to the rest of the shipyard this is a traditional building shed, not a dry-dock, which means you are in for a close encounter with the impressive bow and hull of the yacht in build. It’s historic ground for Heesen, with over 40 years of history, and continuous evolution in hull design. Senior naval architect Sjoerd van Herk hasn’t been around for that long, but together with his design team he can draw on the collective knowhow and innovations of the many yachts created here.
But there’s one yacht in particular that speaks to the imagination of everyone at Heesen: Octopussy. She was designed to be the world’s fastest superyacht back in 1988. Against all odds she crushed the speed record at 53.17 knots and put the relatively unknown shipyard from Oss on the map.
“This incredible performance was not only the result of her striking, speedboat-like hull shape, and potent MTU water jet propulsion,” says van Herk, “but also because of her clever lightweight construction, using experimental honeycomb interior panelling to keep the weight and drag to a minimum. This obsession with weight saving and efficiency is still omnipresent at Heesen.”
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Less weight means less displacement
One of the most effective ways to improve hull efficiency is by reducing the weight of a yacht. Less weight means less displacement and drag.
More weight = More surface = More drag
The science of efficiency
Obsession, or science? Let’s start with a simple definition of hull efficiency:
"Hull efficiency basically means that you want to minimise drag, so you need less engine power to propel the yacht,” explains van Herk. "There are two ways to reduce drag: either by optimising the hull design, or by reducing the weight. Less weight means less displacement.”
That’s why Heesen specialises in building in aluminium. Although this lightweight material requires special skills to weld and innovative construction solutions with larger vessels, the performance and efficiency benefits are significant. Heesen’s 80.07-metre Project Cosmos, the world’s largest and fastest all-aluminium superyacht, boasts a patented Backbone construction to build longitudinal strength into the hull. The result: 150 tonnes saved compared to an equivalent steel hull, resulting in an incredible top speed of 29 knots and a considerable increase in fuel-efficiency at cruising speeds.
Although naval architecture has changed significantly thanks to CFD calculations, still every Heesen hull has to pass extensive tank tests to make sure the numbers add up. Watch the video to discover how it’s done.
Sjoerd van Herk
Senior naval architect Heesen Yachts
Balancing efficiency and stability
“Of course, Cosmos is an extreme example, but hull efficiency is at the heart of every Heesen yacht,” van Herk explains. "We always start with the owner’s wish list, which then leads to a first sketch of the General Arrangement. We know that a canoe-shaped yacht with a long hull and a narrow beam is good for efficiency. At the same time we want the yacht to be stable and spacious to accommodate all the client’s wishes. But there’s always a sweet spot, balancing efficiency and stability.”
To reach the required top speed, naval architects are hesitant to simply add installed power.
“Bigger engines cause extra weight, so you end up in a downward spiral with a yacht that’s a little bit faster, but extremely inefficient. The trick is to use as little power as possible, by optimising the hull form.”
A perfect example is 50-metre Project Sapphire. For this new series, Heesen’s in-house team of naval architects created an optimised, low-drag hull with a reduced transom depth, and propeller tunnels to allow for a shallower shaft angle. With these refinements, Sapphire requires 12% less installed power to reach the same speeds.
Highlights in hull efficiency
40 years of constant evolution in hull design have lead to some spectacular innovations at Heesen; these are the highlights.
Octopussy (1984)They all said it couldn’t be done. But when Heesen delivered Octopussy in 1988 topping out at 53.17 knots, she went down in history as the fastest superyacht in the world. Her aluminium construction and experimental interior weight-saving technologies set new standards for lightweight yacht building.
Galactica Star (2013)Heesen’s flagship at the time, 65-metre Galactica Star was the world’s first aluminium yacht with a Fast Displacement Hull Form designed to achieve seeming contradictory objectives: to go further faster but use less fuel in the process.
Project Sapphire (2022)Heesen’s in-house team of naval architects created an optimised, low-drag hull design with a reduced transom depth, which led to efficiency gains of around 12 per cent.
Project Orion (2022)At 50 metres in length and below 500GT with a shallow draft, Project Orion arguably possesses the most efficient hull form in her class. The all-aluminium FDHF is complemented with Heesen’s state-of-the-art hybrid propulsion system, which reduces noise and vibration, and offers a more flexible power management for improved efficiency.
Revolution in naval architecture
These impressive results are only possible thanks to a revolution in naval architecture, enabled by Computational Fluid Dynamics (CFD) testing.
"Naval architecture truly has evolved into a science,” says van Herk. “In the old days you would draw a hull based on experience, which you would then fine-tune by performing tank tests. Nowadays we still use tank tests, but only to verify the computer data that we are already very sure of.”
Over the years, Heesen has pioneered radical new hull designs together with longstanding partner Van Oossanen Naval Architects. In 2005 Van Oossanen were one of the first to employ CFD. Ever since they have been feeding their supercomputer with many different simulations, making CFD testing just as realistic and reliable as tank testing.
The CFD pioneering work of Van Oossanen has led to one of the biggest breakthroughs in naval architecture: the Fast Displacement Hull Form. This revolutionary hull was then further engineered by Heesen to debut on the 65-metre flagship Galactica Star in 2013.
“What’s unique about the FDHF is that it’s efficient throughout the whole speed spectrum,” explains van Herk. “Before that you either had hard-chined, high-speed yachts, or round-bilged, low-speed yachts. Instead, the FDHF is a round-bilged hull, combined with a newly developed bulb, which turned out to be efficient at any speed, reducing fuel consumption by as much as 30 per cent.”
What does the future hold?
The FDHF has improved even further over the years, with the latest version implemented on Project Cosmos. But also in other departments efficiency is gained. More recently, Heesen has been optimising the propeller design with CFD, which helps to improve noise levels on board. Another development is the integrated exhaust design, which also reduces drag.
The emphasis on sustainability has placed even more importance on hull efficiency, and Heesen will continue to push innovation with every new yacht. What will the future of naval architecture for superyachts look like? Van Herk is uncertain, but hazards a guess. “In water sports like wind and kite surfing we see all kinds of hydro foils evolving,” he says. “You can even spot them on speedboats and tenders. I think it’s only a matter of time before we see them on larger vessels. Superyachts with hydrofoils? I don’t know, we still have a lot to learn, and we probably need to rethink everything we know about hull forms. But it’s an exciting idea, and an incentive for the industry to build lighter boats.”
Despite being the world’s largest and fastest all-aluminium yacht, Project Cosmos also boasts impressive efficiency-enhancing solutions. A battery pack of 567 kWh allows her to stay at anchor without any generator running for two hours. The same battery pack provides peak-shaving capability to prevent generators starting up when demand for hotel services is high.
Keep it light
Lightweight interiors are essential to reduce the weight of a yacht, and Heesen has turned furniture construction into an art form. Perforated or honeycomb fittings, floors and wall panels are used to save weight for the fixed furniture throughout the yacht interiors.
AluminiumHoney Comb Structure
MarbleTop Layer Finish