ACADEMIA

While open floor plans, exotic (and sometimes heavy-weight) wood trim panels, polished stainless steel columns and built-in furniture pieces may create luxurious surroundings, Delta's engineers know how critical it is to optimize the yacht's structural elements to deliver the required strength while avoiding any extra weight that would reduce speed. As a result, the company's naval architects turn to graphite composites, layered engineered materials that are stiffer and stronger than metals per unit of weight.

"Composites enable more flexible designs because their physical properties can be tailored to a very high degree. But at the same time, composites can be more complex to model than solid materials such as iron or steel," said Chad Caron, P.E., naval architect for Delta Marine. The depth of technology in software from ANSYS provides complete composite solutions, which otherwise would be quite challenging, since each composite layer can have different material properties. Delta uses ANSYS technology to evaluate global and local stresses on a layer-by-layer basis. Most other structural analysis packages merely average the loads over the stack.

"ANSYS software tells us exactly where the load is going, down to the individual composite layer, so we are able to tailor the design to provide strength and stiffness exactly where it is needed," Caron said. "These capabilities free the designers to put walls and partitions wherever they want while at the same time keeping the weight to a minimum level. As a result, the design delivers the optimal combination of luxury and performance."

In the past, yacht interior design was constrained by structural considerations. For example, pillars needed to be aligned for structural integrity. "These days, a pillar is as likely as not to land in the middle of a beam. When pillars are not aligned, it becomes much more difficult to determine how loads will distribute among the various structural elements. Traditional design methods, such as handbook formulas and rules of thumb, are not adequate to achieve an optimized structural assessment. The load path becomes convoluted with many 90-degree angle turns that require taking the exact geometry and load locations into account. This means that analysis typically needs to be performed on a global basis, which in turn requires very powerful software and hardware," Caron added.

Delta engineers also perform simulation for vibration using ANSYS software, and the results provide information that allows naval architects to adjust the design only in the areas needed to increase strength or reduce vibration. In this way, simulation assists in keeping the structure as light as possible to deliver speed.

"Innovative designs often require innovative engineering solutions. Using Simulation Driven Product Development from ANSYS during the design phase allows companies like Delta to test and adjust the design of these large craft before they are built. This also makes it possible for them to create yachts with award-winning interiors based on aesthetics, not just structural considerations," said Dipankar Choudhury, vice president, product strategy and planning at ANSYS, Inc.