Hard Chine design with developable surfaces

摘要

In this paper, the design of hard chine lines is parametrically studied. The paper proposes a method to create hard chine lines with the use NURBS curves and developable surfaces. First, the centreline profile, chine and sheer lines are parametrically described and modeled with a NURBS curve. Once these lines are obtained, a developable NURBS surface that rest on the defined curves is created. A review on the mathematical formulation of NURBS curves and surfaces is made. The proposed method defines the lines based on the direct surface design instead defining the sections that is the traditional way. Once the surface is designed, sections can be obtained. An example hull defined with the method is presented. Developable surfaces are especially important in ship design when working with sheet materials like plywood, steel or aluminium. Developable surfaces can be formed from flat sheets without stretching or tearing and with a minimum use of heat treatments, so the forces required to form sheet materials into developable surfaces are much less than for other surfaces and the construction costs are lower. Manufacture can be improved if developable surfaces are considered from the onset of a design.