In the present paper, a comprehensive analysis of the environmental and operational improvements associated with the incorporation of a stern tube-less design in conventional ship configurations is presented. The study is based on a 3,800 TEU container vessel. The proposed innovative design incorporates the elimination of the stern tube, the design of a shorter intermediate shaft, the introduction of a water-lubricated aft-most bearing and the option to eliminate the forward stern tube bearing. We have employed several numerical calculations to assess the feasibility of the proposed conversion and addressed the potential difficulties and associated risks in accordance with Class rules. The detailed powertrain analysis encompasses shaft alignment calculations, determination of bearing reaction forces, evaluation of bearing performance using the Reynolds equation under various conditions, and vibration analysis of the propulsion shaft, to assess compliance with fatigue requirements due to torsional vibrations. Moreover, the study includes an energy efficiency comparison between the conventional and the proposed design, in terms of total friction losses in the bearings of the propulsion train. Overall, the findings highlight the potential benefits of this novel design, including improved propulsion efficiency, reduced maintenance costs, and increased operational reliability. The work provides valuable insights for ship designers and engineers considering a stern tube-less design conversion.

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