FEM in Yacht Design
Integrating structural analysis within the design spiral
FEM in Yacht Design
After having delved into the details of Computational Fluid Dynamics (CFD), we now turn our focus to another service offered by our studio: the Finite Element Method (FEM), also known as Finite Element Analysis (FEA).
This powerful method allows us to investigate the structural response of a yacht under various loading conditions, pinpointing the maximum stress thresholds that the yacht’s structure, or its components, can endure.
FEM serves as a critical tool throughout the structural design phase, enabling us to assess and optimize components before they are fabricated. Possible adjustments involve reinforcing some areas, adjusting thicknesses or, in the case of components made of composites, optimizing the layups and changing the direction of the fibers.
As previously done for the CFD, Christoph Braun, senior naval architect at iYacht, took us behind the scenes and explained the methodology adopted by iYacht. The chosen program is Scan & Solve, a Rhino plugin. As a studio offering a comprehensive range of services, seamless integration with the 3D modeling software is essential for streamlining the whole process.
Integration of FEM in the design spiral
How is this method integrated into the design spiral? When is it suitable to perform these calculations?
FEM are run at the end of the structural design phase. Before finalizing the structural layout and design, some components are evaluated and, if necessary, adjusted and optimized.
FEM is also valuable for saving weight and optimizing thicknesses in areas where stress, strain, and loads are not as high, thereby preventing over-dimensioning of components.
Another key application of FEM is to assess the feasibility of a design approach. In such cases, FEM is applied early in the design phase. For instance, when designing a new sailboat we used FEM to determine if our idea of a Bowsprit without a Bobstay was a feasible solution. FEM models are used to predict the boat’s response when subjected to the various forces and stresses encountered under typical sailing conditions.
Through these calculations, designers can evaluate the feasibility of their chosen approach or determine if they need to go back to the drawing board and consider alternatives.
FEM also intersects with CFD (Computational Fluid Dynamics) in various applications. By studying the flow, we can achieve a more accurate analysis of the loads on certain components. These load conditions then serve as inputs for the FEM.
For example, recently at iYacht, an extensive analysis on some asymmetric daggerboards for a performance catamaran benefitted from the combined insights provided by FEM and CFD.
Which components are typically subject to FEM analysis?
In yacht design, FEM is commonly applied to components and key structures that are complex in shape or subjected to significant loads. Typical components analyzed include bowsprits, tender crane davits, and the core structures of sailboats, such as the keel and mast, where loads are particularly high.
For instance, the keel lifting structure of sailboats usually experiences high bending moments, and for analyzing this component, FEM is run on the midship section.
Another complex analysis recently performed by iYacht involved the entire structure of a GRP catamaran. For this project, a global hull torsion analysis was conducted to meet class requirements set by DNV.
Which materials are easier to simulate?
When it comes to material simulation, isotropic materials like aluminum and steel are easier to handle in FEM due to their uniform properties in all directions. Composite materials, being anisotropic, add some complexity to the FEM setup.
The importance of human sensibility and expertise
Human sensibility is crucial in ensuring that FEM tools are used correctly. Instead of blindly trusting the results, it is necessary to understand how to interpret and validate the outputs before using them to iterate the design.
The principle of “garbage in, garbage out” applies, meaning that if there is a setup error, the inaccurate input will lead to incorrect results. To mitigate this, results from FEM are often compared to analytical evaluations. Simplified analytical calculations are performed by iYacht’s engineers and naval architects to judge if the FEM results fall within the expected range, thereby ensuring reliability of the calculation.
Ultimately, the combination of advanced tools and human expertise creates a robust framework for effective solutions. Ensuring that these tools are used correctly and the results are critically assessed will lead to optimal design outcomes.
To discover the whole range of services offered by iYacht, visit the dedicated section of the website: https://i-yacht.de/services-process/
