Simplified analytical method for the evaluation of longitudinal strength of large sailing yachts

Yacht manufactory industries have been faced with two different trends over the last few years: on the one hand, the current economic crisis, which has halted the production of super and mega yachts, and on the other, the increase in the dimensions of both sailing and motor yachts. In the case of sailing yachts, this trend has brought about a consequent increase in rigging proportions. Higher masts and wider sail plans have led to an enormous increase in rigging and sheet loadings. Meanwhile, speed has become an increasingly important focal point in the design process, in order to respond to market requirements; this scenario requires an acceptable compromise between structural requirements due to high rigging loads and structural weight reduction to improve the craft speed and to reduce costs and production times. For these reasons, the global strength of the hull has become a crucial aspect in the design process. Traditionally, only still water and wave bending moment in hogging and sagging conditions have been considered as global loads. For sailing yachts, however, the dock tuning bending load, which has a similar order of magnitude to the global bending moment, must be implemented in primary strength response. In this paper, the authors present a Simplified Analytical Method (S.A.M.) to estimate the longitudinal strength of a large sloop sailing yacht; this approach has been developed studying a 47-meter yacht by FE technique coupled with classic beam theory and has been verified through the analysis of other two sailing vessels of similar length. A user-friendly routine for this aim, called "StrengthCalc", has also been created.