The problem of acquiring procedural knowledge for hull form design and construction of a knowledge base for hull form selection is addressed in this paper. An object oriented methodology involving creating classes, state diagrams and data flows for parametric hull form design was undertaken. An interactive graphical tool for the production of hull designs from a parent design was developed based on knowledge acquired from domain experts and the technical literature. Hull variation was accomplished by changing common design parameters including CB, CP, LCB and parallel middle body. Dependent and indendent variation of design parameters was allowed and the tool produced variants of the parent hull rapidly with a high degree of flexibility. The resulting forms then serve as input to a selection tool for constructing the knowledge base. The tool was based on rating grids and involved the elicitation of decision elements, traits and ratings from users to build a set of rules for selection. Sample selection sessions illustrate the applicability of the system.