The primary problem that shafting alignment designers are faced with today, is high sensitivity of the alignment to the hull girder deflections resulting from the changes in the loading condition of the vessel. Accordingly, the accuracy of the alignment procedure will depend on our ability to account for hull deflections in the alignment design.

The shafting alignment optimization approach, that ABS is proposing in this paper, provides a solution to the problem. So far ABS collected a sufficient amount of hull girder deflection data to generate an initial database, and enable alignment designers to estimate hull deflections with high confidence on new designed tankers and bulk carriers.

Establishing the hull deflection database is an essential part in shafting alignment optimization, as we want to ensure the robust alignment design, with sufficient margin of safety to remain satisfactory under extreme hull deflections, thermal change in bearing offsets, as well as to absorb much of the possible unpredicted disturbances.

In this paper we will show how the hull deflections are utilized in the alignment design and optimization. We will indicate the advantages of undertaking this approach and discuss concerns and constraints the designer should be aware of when analyzing the alignment.

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