Composites analysis

Case Study

Composite Wingsail Design

  • Linear static analysis of leading section, spar and connecting strip

  • Viewing of stresses in individual laminae

  • Cowin failure criteria showed where design could be improved

Wingsail yacht

Composite wingsail

Designed using aerospace technology, the 13.65m high wingsail is made from layers of glass and carbon fibre surrounding a Nomex-type core. The trailing section or 'wing' is separated from the leading section or 'flap' by an air directing slat. Upper and lower booms connect both of these sections to the tail. The whole assembly is mounted on a large diameter ring bearing allowing a precise and constant angle of attack to the wind to be obtained.

To analyse the new wing design a 3D FE model was created in LUSAS Composite using 8 noded quadrilateral thin shell elements from DXF and additional coordinate data. To match the method of fabrication the model was divided into 3 main parts: a leading section, a spar section and a strip section that bonds the leading and spar sections together. To achieve the specified composite structure, 17 different geometry and composite data sets were created for each of the 3 main parts of the model with each composite dataset containing detailed information about layup sequence, material orientation and relative thickness of the layers. By using LUSAS Composite, lay-ups can be defined independent of the component to be analysed and the lay-up orientation and sequence can be viewed visually, giving a fast and accurate model definition.

Four loadcases, consisting of a UDL acting on the upper 12.8m of the trailing section; inertia forces in the trailing section itself; and upper and lower boom forces applied as concentrated loads 8.2 and 0.75 m from the bottom of the trailing section were used to arrive at a resultant load combination for the analysis. The linear static stress analysis gave excellent results. By using the extensive LUSAS results processing facilities principal stresses in each composite layer could be viewed. Stresses perpendicular to the material orientation were generally low with the exception of the transition area near the base of the wing where, as could be expected, some areas of high stress were found where rapid changes in geometry took place. By applying Cowin failure criteria to the composite structure, areas where the design could be further optimised were highlighted.

"By using LUSAS Composite for this analysis Walker Wingsail Systems were able to go into the prototype build stage with enhanced confidence in a very satisfactory lighter design."


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