3738. Aft Perpendicular… An Afterthought?


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Scott Daley, Rob Dvorak, Matt Marburger: 3738. Aft Perpendicular… An Afterthought?. 2022.



How do you define the length of a ship? What is the definition of aft perpendicular? From the Principles of Naval Architecture (PNA), the definition for the location of the aft perpendicular “is at the aft side of the rudder post, centerline of the rudder stock, or at the intersection of the design waterline with the aft end of the vessel.” However, for U.S. submarines, the location of the aft perpendicular has not always followed PNA’s definition. The location for a submarine’s aft perpendicular has been at the end of the thrust device or at an outdated feature. This paper will examine the technical details, design maturity and timeline, and implications of how the aft perpendicular on a submarine is defined.


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