Design considerations for lightweight high-speed ships using planked construction

In recent years there has been increasing use of extruded aluminium planks in the construction of high-speed ships, particularly in regions of relatively simple ((i.e. flat)) geometry such as deck structures, where the use of extrusions can significantly reduce production costs. There is also interest in extending this concept to FRP ships through the use of pultruded planks. Significant additional gains could be made if the curved ship hull surface could be constructed from a planking system. The current study investigates some of the challenges associated with the design of high-speed shiphull forms for planked construction. A description is given of an algorithm used to position planks on a three-dimensional surface, such as a ship’s hull. Subsequently, the curvatures and twist of the planks can be calculated. This information, together with knowledge of the properties of the plank, can be used to assess the “plankability” of the hull, with respect to stresses induced in the plank. The procedure is demonstrated by applying the algorithm to a high-speed form based upon the NPL series. This indicates the problems associated with the complex geometry of present high-speed hull-forms with respect to planking. Suggestions are made to eliminate or reduce the associated problems; two simplified hull-form concepts were generated, based upon a modified NPL parent form. The “plankability” of these forms are compared with the parent hull-form, and the performance implications of simplifying the hull-form are investigated. Calm-water resistance tests were carried out and results compared against the parent hull-form. It is concluded that calm-water resistance is not significantly affected even by quite extreme simplification of the form