The RP90 racing yacht’s anchor arm was made from lightweight composites. (Image courtesy of Peter Schreiber and Reichel/Pugh).
The RP-Baltic 130 Custom racing yacht. A lot of lightweighting went into the design of its hull and deck. (Image courtesy of Carlo Borlenghi and Reichel/Pugh).
When most people imagine sailing on a yacht, the scenarios likely involves bikinis, martinis and perhaps something steamy. To enhance that experience, engineers design superyachts with a focus on creature comforts, finding ways to fit an entire home in a boat.
However, when it comes to racing yachts, what you get is a whole other animal, though no less posh. In these cases, the engineer’s goal shifts from finding a place for the bar fridge to getting every ounce out of an anchor arm without affecting the safety of the ship.
“For a custom superyacht, structures must be hidden behind modern, open, and well-appointed interiors, making these systems significantly complex,” said Adrian Sawyer, composite structures designer at Reichel/Pugh Yacht Design (Reichel/Pugh). “Designing racing yachts requires an inherently different approach in order to marry structural integrity and performance with uncompromised comfort and aesthetic appeal.”
For companies like Reichel/Pugh this is a job for simulation-driven optimization and lightweight materials. Much of this simulation is made possible thanks to Altair’s portfolio of computer-aided engineering (CAE) software.
“For a purpose-built racing yacht, designers have a great deal of freedom to optimize structural arrangements for lightweight efficiency,” added Sawyer. “Beams, bulkheads and rigging foundations can be placed with less regard for headroom and interior comfort, normally resulting in simplified structures.”
Simulation and Lightweighting for Yacht Design
Stress analysis of the RP-Baltic 130 hull and deck. Loads appear to be concentrated around the deck bulwark ledges. (Image courtesy of Reichel/Pugh.)
You have your heavier components made of steel or even lead. Then there are the lightweight materials, such as aluminum, fiberglass and carbon fiber composites.
“Conventional isotropic metallic materials are inherently limited by basic material properties, significantly lower strength and stiffness to weight,” explained Sawyer. “Many metallic structures have strength and stiffness in unnecessary directions, whereas carbon composites can have variable properties in multiple directions.”
The goal, Sawyer explained, is to balance the unique properties, benefits and drawbacks of each material for a given part’s functionality. At the end of the day, if you can reduce the weight of the racing yacht while maintaining safety, you will enhance its performance. Using simulations and lightweight materials, Reichel/Pugh was able to reduce the weight of its RP-Baltic 130 hull/deck and its RP90 anchor arm.
“Nowadays, it’s obvious that carbon fiber is leading the pack for its impressive stiffness and strength to weight ratios and unique manufacturing processes,” said Sawyer. “The ply layup process and the directional properties of carbon fiber enable us to create intricately-complex geometry, orient material efficiently and provide structural thickness only where it is needed for stiffness and strength.”
Unfortunately, engineers can’t just take a part, change up the material to something lighter and hope for the best. They need to optimize the part without incurring safety risks. Even then, who is to say that the part itself has the best shape for the job?
In other words: engineers need data, and to get that they can use finite element analysis (FEA) software to run simulations and optimizations. One of the product suites Reichel/Pugh relies on is the aforementioned portfolio from Altair. Sawyer explained that this decision is due in part to the product line’s ability to optimize parts with isotropic and composite materials.
“We have used [solidThinking] Inspire’s topology optimization to design metallic structures, such as bolted fittings and structural cover plates. This helped us remove unnecessary material in ways that aren’t always intuitive,” explained Sawyer. “We have also used HyperWorks and OptiStruct for global analysis of complex hull structures, and more recently for composite ply-by-ply optimization of individual structural components.”
How to Lightweight a Racing Yacht with Simulation
FEA analysis of the RP90 anchor arm was used to optimize the composite material such as ply thickness and orientation. (Image courtesy of Reichel/Pugh.)
The next step was to review the initial material and perform preliminary engineering analysis. The company then assessed how the anchor arm of the RP90 would react if it were built with carbon composites. The engineers took full advantage of the greater design flexibility that the material offered.
“We created a finished anchor arm that is visually distinct from anything we’ve built previously,” said Sawyer. “The first challenge was to create a surface-meshed model that could accurately represent the final part geometry while having the ability to be altered as the project progressed.”
The models for each of the two yachts were divided up into numerous parts that were surfaced and meshed separately. This gave the design team the ability to change each part without affecting the mesh of the whole design.
“The initial free-size composite ply optimization for the anchor arm was surprisingly easy to set up and understand,” noted Sawyer. “The challenging part of this design was creating something manufacturable and understanding Altair’s computational architecture well enough to adapt it to our specific needs. But when we did, it was extremely powerful. We were easily able to modify geometry, loading scenarios, ply shapes and optimization constraints to stay within our structural and construction requirements.”
The design team used HyperMesh to modify the ply shapes that made up the anchor arm of the RP90. A similar process is carried out for the hull, deck and structures of all Reichel/Pugh designed superyachts.
“We heavily used Hyperworks and Optistruct for carbon composite ply shapes, orientations and thicknesses,” said Sawyer, “but used in-house methods and manufacturing constraints to determine the final through-thickness stacking sequence. These plystacks were then re-analyzed in OptiStruct for final design confirmation.”
Sawyer added, “Using customizable composite materials, coupled with Reichel/Pugh’s optimization methods and Altair’s FEA tools, this anchor arm only has strength and stiffness where it is needed, without wasted material where it is not.”
Unfortunately, there is a catch when optimizing parts for lightweight and strength. Often, the best design is impossible to manufacture. This was also true for Sawyer’s team, who experienced issues with layup, compaction and curing the parts.
To combat this, Sawyer said his team “used free-size optimization to suggest optimized ply shapes and worked closely with the builders to modify the optimized ply shapes for manufacturability.”
Fortunately, manufacturing techniques are continuously getting better, and tools like 3D printers make it easier to build shapes once thought impossible to manufacture. Sawyer noted that these trends are also affecting yacht design. He is confident that as the technology gets better equipped to build these truly optimized designs his team will be ready to create them.
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Altair has sponsored this post. It has provided no editorial input. All opinions, unless otherwise stated, are mine—Shawn Wasserman.