Page 340 - Practical Design Ships and Floating Structures

Practical Design of Ships and Other Floating Structures 315
You-Sheng Wu, Wei-Cheng Cui and Guo-Jun Zhou (Eds)
0 2001 Elsevier Science Ltd. All rights reserved

DEVELOPMENT OF A SOPHISTICATED HULL FORM CAD
SYSTEM 'EZHULL' BASED ON A NON-MANIFOLD MODEL
AND 'X-TOPOLOGY'

Kyu-Yeul Lee', Joong-Hyun Rhim', Sang-Uk Lee', Doo-Yeoun Cho' and Young-Bok Choi'
'Department of Naval Architecture & Ocean Engineering and Research Institute of Marine
System Engineering, Seoul National University, San 56-1, Shinlm-Dong, Kwanak-Gu, Seoul
1 5 1-742, KO=
'EZCRAPH, Co. Ltd., Rm 1201, Union Center, Yoksam-Dong, Kangnam-Ku, Seoul, Korea

ABSTRACT

Hull design evolves from a wireframe model to a surface model through conceptual design,
preliminary design, and production design. Hull form designers initiate designs using wirehe
models with which they are familii, and want to convert a wireframe model to surface model-
whenever it is necessary. Thmfore, hull form design system should support not only cross fairing and
correct points ordering for a wireframe model but also be able to generate the surface from the
wireframe model.
The EzHULL system developed in this research, provides an association based cross fairing and
surface generation, using X-topology and non-manifold data structure. X-topology is the data structure
for a wirehe model that supports the association based cross fairing. The Bssociation based cross
fairing enables effective wireframe modification by automatically updating all hull lines related to a
changed line. The non-manifold data structure stores both topological and geometric data of the
surface model produced fiom the wireframe model. The geometric data of the surface model can be
used to display the 3-D surface hull form to check the surface fairness at the early design stage of hull
form. And, the topological information can be used to solve the points ordering problem that occurs in
the wireframe based design system. An example of a twin skeg hull form showing the effectiveness of
the developed system is included.

KEYWORDS

Hull form CAD system, cross fairing, surface model, non-manifold data structure

1 INTRODUCTION

The hull form design process is a multi-disciplii operation involving cooperation between design
departments. A CAD system in hull form design plays a hdamental role by sharing hull form data
with other design processes [l]. Since the hull form normally evolves from a wirefiame model to a