Trans RINA, Vol 152, Part B2, Intl J Small Craft Tech, 2010 Jul-Dec


PRELIMINARY DESIGN OF CRUISING SAILING YACHTS AS A DECISION SUPPORT PROBLEM


P K Pal and K Klaka, Curtin University of Technology, Australia (DOI No: 10.3940/rina.ijsct.2010.b2.105)


SUMMARY The primary objective of a racing yacht is to win the race, so the design process is dominated by performance without considering the cost of construction. In contrast, the design process for a cruising yacht is dominated by consideration of the cost, internal space, aspect of aesthetics, etc. Traditional design procedures such as a parametric study are usually employed to determine a technically feasible sailing yacht design. This method takes considerable time and cost so it is better to find an optimal solution quickly using a mathematical optimisation technique at a lower cost.


This paper describes the development of a mathematical model for determining the principal design parameters of a cruising sailing yacht at the preliminary design stage. The conflicting demands require a compromise solution that is obtained by formulating the problem as a compromise decision support problem and applying the decision support problem technique. The model is tested for a set of owner’s requirements and sensitivity analyses are also carried out.


NOMENCLATURE BWL


CBC CE


CLR DISPTL


sailing yachts e.g. [1], and other vessels e.g. [2] generate main dimensions


of Waterline beam (m)


Calculated block coefficient Centre of effort above deck (m)


Centre of lat. resistance below deck (m) Displacement (tonnes)


HEELMV Heel angle at VMGMAX (degrees) LWL


Length on waterline (m)


MASSTL Total mass (kg) ROHBL


ROHLD Density of lead (kg m-3) RTOTMV Total resistance at VMGMAX (kN) SLM TC


Density of ballast material (kg m-3)


Factor to limit the mast height Canoe body draught (m)


TMAX Maximum draught (m) TRES


Restriction of draught (m)


TRMSTL Target total mass (kg) TRHLAN Target heel angle (degrees) TRTOTR Target resistance (kN) TRVMG Target VMGMAX (kn) TRYTCS Target cost of yacht (Euros) VOLBL VOLK VOLR VMG


Volume of ballast (m3) Volume of keel (m3) Volume of rudder (m3) Velocity made good (kn)


VMGMAX Maximum velocity made good (kn) VOLCB Volume of canoe body (m3) YATCST Cost of yacht (Euros)


1. INTRODUCTION


Sailing yacht designers generally use the traditional iterative method through the steps of the “design spiral” to find only one technically feasible design. Sometimes the parametric study method is also used to determine an optimal solution that normally takes considerable time and thus the cost of design becomes high. Artificial neural networks have been applied to the problem for


the vessel for to given


performance targets. They provide a quick estimation of preliminary design characteristics, the quality of the information depending on the strength of the training data set used. They must be trained for each combination of inputs separately. Artana and Ishida [3] take a similar approach for the preliminary design of a tanker for minimum economic cost of transport, though they use a spreadsheet for analysis rather than an executable code. Most of the yacht applications have focused on aero- and hydro-dynamic characteristics of the yachts, as distinct from interior


design and cost. Van Oossanen [4]


developed a “Concept Exploration Model” for the design of cruising yachts. This model is limited by a fixed hull and rig configurations and a material of construction. No mathematical optimisation is used.


Genetic algorithms have also been used to good effect as they can deal with nonlinear holistic design problems and discrete variables, though they demand high computing power [5]. Gradient search methods, on the other hand can be very fast but require discrete variables to be converted to


continuous approximations [6]. The


approach described in this paper is to develop a model using a mathematical optimisation method.


The considerations for the design of cruising yachts are quite different from that of racing


yachts. The


performance under sail dominates the design of a racing yacht and the cost factor does not influence the process. However, for the design of a cruising yacht, the cost, internal space and aesthetics influence the design process and the performance under sail plays secondary role. The vessel becomes fuller to provide more internal space but to attain larger VMG for a particular wind speed, the vessel must be finer. These are conflicting demands. Therefore, the design problem may be formulated as a compromise decision support problem and the solution


©2010: The Royal Institution of Naval Architects B-75


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