The examination of construction materials' impact on stability and strength during concept design phase of yachts

Because of its strength, the gained knowledge in the welding technologies and the availability parameters, steel as a material was used to be the most popular ship building material for many years. Due to the improvements in metallurgy technology, the studies are canalized to find alternative material types for production. As a natural result of it's low density, Aluminium has a weight and easy forming advantages which collected the attention of industry on itself. After a short while, it has been started to be used in shipbuilding sector after the adaptation researches completed. Except for the usage of Aluminium as a single material of the construction, due to several purposes, a growing demand has been occured in order to use Aluminium together with steel. This has forced the technology to find out new solutions. Aluminium is being mostly chosen as a construction material for the superstructures. Thus, the financial disadvantage of it can be minimized and the strength, seakeeping and stability can be accordingly optimized. Despite the class societies have started to update their scantling rules for the use of aluminium as a construction material, this number is still quite limited. Because of being a relatively new material compared with steel, it is still not possible to find the detailed rules for yachts except for LR and BV. In this research it is aimed to guide the designer during the proposal and concept design phase by decreasing the number of iteration in design spiral. During the study stability and strength models are developed. A strong prediction is made for the stability characteristics which can be described my means of hull's main parameters. In the strength section of the research a guidance is aimed to be shown by using the basic strength principles in order to optimize the superstructure dimensions and choosing the right material combination for the hull and the superstructure. Among the stability section road map is explained step by step for the evaluation of the stability in a practical way by using the studies of Prohaska as a foundation. In the strength section, Bleich's approach is observed which is based on Navier's theory and the required simplifications and developments are brought in order to use it for motor yachts. For proving the reliability of the method the finite element models of several superstructures are made and the results are compared with each other. Besides this, opinion of experts are interviewed and weighted estimation method is used in order to optimize the sequence of priorities and to decrease the number of iterations during the concept design phase. During the research several adaptations and developments are made, by developing practical approaches the naval architect will able to calculate the main values in order to make clear predictions about preliminary stability and strength. After evaluating these results the engineer will decide whether an optimization should be made for material or main dimensions. The designer will able to reach the values which will be required for preliminary design stage and for price estimation after the minimized iteration process.