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Optimal sail design and rig tune of a J70 are studied using RANS CFD, FEA and a low cost data acquisition system. In one design racing sail design and rig tune are the biggest variables that can be changed from one boat to another and figuring out the correct balance between the two is critical to good performance. One design sails are challenging to model computationally because they deform under sailing loads and are sensitive to rig tune. Using accurate flying shapes in CFD models is key to picking out the slight aerodynamic differences in sail and rig setup. We develop a system to monitor sail flying shapes, trim, rig load and performance data based on cheap hardware components and open-source data processing libraries. The sail shape and rig data are used to drive the geometry used in the aerodynamic RANS CFD simulations. A series of J70 sails and rig setups with known performance characteristics are modeled and tested on the water, and the proposed camera system was able to differentiate between different rig tunes and recreate them in CAD software. CFD force data and post processing information is studied to understand what are the optimal aerodynamic characteristics and how are they effected by sail design and rig tune.
Sailing Yacht Transom Sterns - A Systematic CFD Investigation
The question adressed in this project is whether modern hull lines with wide, box-shaped transoms, that seem
to originate from extreme racing machines, are also beneficial for modern performance cruisers from a hydrodynamic
performance point of view. A new 41 ft (12.3 m) hull was designed as an average of contemporary performance hulls in
the 40 ft segment. The aft part of the hull was stretched stepwise and cut at constant length overall in order to
systematically increase the transom size. Six hull variations with box shaped transoms were created in this way. To
investigate the influence of the transom shape, the six hull variants were redesigned with a more rounded transom. The
resistance was calculated for all twelve hulls in the upright and heeled conditions at Froude numbers 0.35 and 0.60. The
computations were carried out using a Reynolds-Averaged Navier-Stokes (RANS) solver with a Volume of Fluid (VOF)
representation of the free surface. The solver was validated against several hulls in the Delft Systematic Yacht Hull
Series (DSYHS). Very different optima are found for the low and high speed cases. In an upwind-downwind race the
round transoms performed best for the three fastest transom sizes. The fastest hull around the course has an immersed
transom area to midship area ratio of 0.16 and it has a rounded shape. It is 1.9 % faster than a more box like transom.
Overall the round transoms are faster around the race course.
Ocean engineering special issue: Yacht engineering
It is with much pleasure that we write the editorial for this
special issue devoted to Yacht Engineering, arising from the 3rd International Conference on Innovation in High Performance Sailing Yachts (Innov'sail2013), held in Lorient, France.
Numerical Study of a Flexible Sail Plan Submitted to Pitching: Hysteresis Phenomenon and Effect of Rig Adjustments
A numerical investigation of the dynamic fluid structure interaction (FSI) of a yacht sail plan submitted to harmonic pitching is presented to analyse the system's dynamic behaviour simplifications and rigging adjustments on aerodynamic forces.
This paper describes the method used by the Italian Classification Society RINA to develop new Rig Certification Rules. These Rules have been mostly based on failures observation, and their starting point has been a systematic study of dismastings occurred on boats of various types and sizes. Examining many of these events, typical collapse modes have been identified, and specific solutions have been proposed. Within this study a first attempt to a novel rig “dynamic” structural assessment has been developed taking advantage of a new integrated (CFD+FEM/FEA) analytical tool. Theoretical analyses have been compared with experimental data collected during extensive sailing tests on board a 94ft yacht.