Thermal load effects on side plates of superyachts

From the commercial point of view the aesthetics of large luxury yachts has the same importance of their technical performances and reliability. In this perspective the first impact that a new construction can exert on a potential owner takes place through the overall appearance of the hull and superstructures. The hull colour, in particular, is becoming more and more determinant to make a yacht more attractive. After a long, undisturbed supremacy of white and cream colours, now an increasing number of owners are opting for dark colours, like blue, green or black. For a perfect painting output these colours needs a perfectly smooth surface as they have the tendency to emphasize every small defect of the hull surface. This aspect can be further amplified by those shape defects affecting hull sides, such as bump and hollows, coming from welding plates each other and plates to frames. For this reason, in case of steel and aluminium vessels, the surface finishing must be achieved by a long and delicate process of filling and fairing. Notwithstanding very accurate preparation, hull surfaces can undergo undesired alteration because of long expositions to solar radiation. This phenomenon is amplified when the surface is painted with dark colours which have the tendency of absorbing much greater solar heat. As stated by a previous investigation carried out on superyachts painted with dark colours, the surface of hull sides after a long exposition to solar radiation can reach temperatures close to 70–80°. In order to evaluate possible distortions of hull sides caused by thermal loads, an investigation has been carried out on the influence of temperature on the mechanical behaviour of steel plates coated by epoxy filler. The study has been developed by FEM structural analyses on a portion of a superyacht hull in the region of aft sides where the flatness of shell makes more visible possible distortions. Both steel and aluminium material have been considered covered by filler layers of different kind and thickness. A preliminary experimental investigation has been performed on a number of steel and aluminium specimens in order to calibrate the numerical models.