Engine foundation re-design due to modification of the shaft line arrangement

Abstract

The project is assigned after the initiative from Baglietto's shipyard to consider the implementation of a thrust bearing block in the shaft line, starting with the study of one of their displacement super- yachts. The main characteristics of this type of ships are represented by the study case used for this project, which corresponds to an existent 46m long yacht. Construction plans, technical information and assistance is provided by the shipyard's technical office The main objective of this work is not to prove the advantages of the incorporation of a thrust block in the propulsion system, but to study the adaptation of the original configuration to the variations proposed in the shaft line arrangement. The modifications are applied on the engine’s foundation structure in combination with the redesign of engine block's mounting and coupling systems proposed by competing providers. Different possible modifications of the structure are tested on a partial model of the ship, in order to study the response of the engine block's supporting structure when subjected to selected loads. Part of the work is dedicated to determine the loads that should be taken into account and how to reproduce the way these are transmitted to the structure by the mounting system. The behavior of each proposed modified structure is analyzed and compared based on their stress and deformation distribution and maximum values. These tests are carried out through computational analysis, using the FEM software Patran-Nastran from MSC, under the supervision of the Nautical Engineering Department of La Spezia. The resulting modified configurations of the engine’s foundation presents sufficiently low stress and deformation values. The advantages and disadvantages of each type of proposed solution is described so that it can be consulted as a reference when considering the incorporation of a thrust block during the pre-design stage of yachts with similar characteristics.