Trans RINA, Vol 153, Part B2, Intl J Small Craft Tech, 2011 Jul-Dec


integrated rig-sail analysis system exists. This paper presents a fully integrated, versatile and cost effective sail-rig design system. The emphasis is placed on providing a practical application of rig design, which will allow further improvements over current design methods.


Section 2 describes the method implemented to calculate mast bend, forestay sag and rig element tension under defined tuning and aeroelastic sail


loads. Section 3


illustrates the sail aeroelastic analysis. Section 4 describes the rig structural analysis. Section 5 presents how the method can be applied to optimise a TP52 rig, performing both dock tuning and sailing analysis.


2. SAIL-RIG ANALYSIS


The sail-rig analysis method consists of five phases, as shown in Table 1. In phase 1, the designer creates an initial geometry of the rig by defining mast, spreaders, boom, bowsprit and stays. For each rig element it is possible to set position, sections and material properties. In phase 2, the designer generates the sail shapes and assigns the material properties. In phase 3, the wind loads acting on the sails in specific sailing and trimming conditions are calculated. In phase 4, the sail structural analysis evaluates the flying sail shape and stress distribution. In case the calculated flying sail shapes differ from the designed sail shapes, it is necessary to carry out the aeroelastic analysis that estimates the flying sailplan shape in equilibrium with the wind and the trim loads acting


on the sails (the aeroelastic analysis


considers only the sailplan). At this point, the sail loads can be transferred on the rig. Finally, in phase 5, the rig structural analysis allows calculating stay loads and sag, the tensions on the verticals and diagonals, the spars deformed shape and compression load under the specified tuning loads and the calculated sail loads.


3. SAIL AEROELASTIC ANALYSIS METHOD


The implemented sail static aeroelastic analysis code [2] automatically performs the following actions:


 Generate a panel model, by placing nodal points and control points on the designed sail shape.


 Perform the aerodynamic analysis in defined sailing and trim conditions to calculate the wind loads.


 Apply the wind loads on the current sails FEM.  Calculate the deformed sail shape and stress distribution with the structural analysis.


 Perform the aeroelastic analysis by repeating the previous actions, considering the deformed sail shape, until convergence.


Convergence is achieved when the flying sail shape evaluated with the aeroelastic analysis is in static equilibrium with the


particular sailing and trimming conditions set by the designer. It


also provides


known external loads in the the wind loads and their


Table 1: Sail-rig analysis method.


Phase 1 RIG DESIGN Geometry definition of


 Mast  Spars  Collar  Forestay, backstay and stays  Bowsprit


For each element it is possible to set


geometry properties


Phase 2 SAIL DESIGN Geometry definition of


 Mainsail  Genoa  Spinnaker and asymmetric  Gaff


For each sail it is possible to design the fibre layout and set material properties


Phase 3 SAIL ERODYNAMIC ANALYSIS


Set


 Sailing conditions: AWA and AWS (or righting moment) for each heel angle


 Sheeting angles


The resulting pressure force will be used to calculate the flying sail shape


Phase 4 SAIL STUCTURAL ANALYSIS


Set


 Trim loads (e.g. halyard loads)


 Constraints


The resulting sail structural loads will be transferred on the rig


Phase 5 RIG STRUCTURAL ANALYSIS


For specified tuning loads and calculated sail loads the following are calculated


 Forestay and removable stays load and sag


 Vertical and diagonal shroud tension on both sides


 Mast bend and compression  Collar forces


B-118 ©2011: The Royal Institution of Naval Architects and material


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