Standing Rigging of a Yacht.
Internal forces of the shrouds in a rigging system of a yacht are important to simulate in order to establish the strength under severe circumstances. Presented in the picture to the right the load in the shrouds are visualized. Also indicated the windforces on the mast from a sail, the horizontal red arrows. The shrouds on port carry a higher internal force than on the straboard side. If the forces on the mast become too high a danger can occur of buckling. This is highly undesirable, and these simulations can be done as well. Note, the picture on the right shows only shrouds, the mast is hidden for visual purposes.
In the next section the mast can be seen, and this is a nice example of multiphysics simulation with COMSOL.
Rigging system, mast with two spreaders
Forces on masts should be designed in order to withstand the forces of the wind even under severe conditions. The system is designed according the RCD – Directive 2013/53/EU (Recreational Craft Directive (RCD – Directive 2013/53/EU)) . The arrows in the figure represent the forces from the main sail, and should be understood in this picture as an illustration. Of course all sails attached to the rigging system induce forces, for example the jib, main sail etc. At the right a color scale is visible and the top scale applies to the colors of the mast. The bottom scale applies to the colors of the steel cables.
The mast is built using shell elements, with quadratic Lagrange polynomials. The cables use wire elements with Linear Langrange polynomials, with an additional condition to stay straight when the cables might hang loose under certain conditions (compression).
All these settings add to a robust and reliable output of the stresses and displacements in the rigging system. Note that the standing rigging system has predefined initial stresses. As a common starting point the initial stress in the shrouds is about 15% of the breaking force.
Buckling analysis is also a very important part of the simulation of a rigging system for yachts. Which can be performed with different initial ci=onditions on the rigging system and under different angle of heeling.
