# First International Symposium On Computer Aided Hull-Surface Definition

The First International Symposium on Computer Aided Hull- Surface Definition (SCAHD 77) will be held in Annapolis, Md., on September 26-27, 1977. The symposium will be presented by Technical & Research Panel 0-34 (Computers), and hosted by the Chesapeake Section of The Society of Naval Architects and Marine Engineers.

The proliferation of computers as design aids over the last several years has resulted in extensive software development in the area of hull-surface definition. SCAHD '77 brings together internationally known authors in this field, who will present papers on the most recent work undertaken toward solving the many problems associated with the definition of a hull form using computer aids.

The following papers will be presented during the technical sessions: Paper 1—"Ship Lines Creation by Computer—Objectives, Methods and Results," by H. Nowacki, G. Crentz and F.C. Munchmeyer, University of Berlin, Berlin, West Germany.

SYNOPSIS—A review of stateof- the-art ship lines creation methods in general and B-Spline technique developments in particular. The survey will address the standard series approach, lines distortion from parent lines, free-form design methods and other miscellaneous methods. The summary will lead up to a perspective of current status and promising future avenues in ship lines creation.

Paper 2—"Lines Fairing and/or Lines Design," by H.F. Soding, University of Hanover, Hanover, West Germany.

SYNOPSIS—A description of some special solutions to the lines creation problem.

Paper 3—"Design Experience with Hull Form Definition," by M.P. Lasky, Washington, D.C., and J. Daidola, M. Rosenblatt & Son, New York, N.Y.

SYNOPSIS — This paper discusses design office experience in lines creation and fairing used in the concept and preliminary design stages. The difficulties of integrating such computer aides effectively into the design process are emphasized. Results of a questionnaire survey are reported. Desirable future improvements from the naval architect's point of view are presented.

Paper 4—"Ship Hull Form Generation Using Regular Polynomials," by A. Fuller, U.S. Naval Ship Engineering Center, Washington, D.C.

SYNOPSIS—This paper describes an interactive graphics computer problem which is used to generate early stage design hull forms. Starting with the minimum initial input of length, beam, draft, prismatic and midship section coefficients and a main deck at each profile, a designer can create a body plan at the graphics scope.

Paper 5—"Some Problems in Practical Improvement of Mathematical Fairing," by Yukihido Hattori and Yukio Matida, Nippon Kokan Kabushiki Kaisha, Japan. SYNOPSIS—A description of the mathematical techniques for a lines fairing program developed and used for several years by Nippon Kokan K.K., examples of applications of the fairing process and future supplements.

Paper 6—"B-Spline Techniques for Surface Definition," by F. Theilheimer and J.M. McKee, David Taylor Naval Ship Research and Development Center, Bethesda, Md.

SYNOPSIS—Advances in BSpline techniques for surface definition are described in detail.

Examples are provided to demonstrate the smoothness, local control and computational efficiency of B-Spline functions.

Paper 7—"B-Spline Curves and Surfaces for Ship Hull Definition," by D.F. Rogers, U.S. Naval Academy, Annapolis, Md.

SYNOPSIS—A discussion of BSpline curves and surfaces and their suitability for hull surface definition, with a comparison with several other surface definition methods.

Paper 8—"Surface Representation," by R.E. Barnhill and R.F.

Riesenfeld, University of Utah, Salt Lake City, Utah.

SYNOPSIS—The paper discusses advances in the mathematical definition of basic geometric elements — rectangles, triangles and point data. Examples are the elimination of "twists" for rectangular patches, "triangular Coons' patches" and improvements in Shepard's formula for arbitrarily spaced data. Industry problems and solutions developed over the past several years will be discussed.

Paper 9—"Approximation Theory Techniques for Curve and Surface Description," by G. Nielson, Arizona State University, Tempe, Ariz., and J. Wixon, General Motors, Warren, Mich.

SYNOPSIS — The paper will discuss curve or lines creation followed by surface descriptions which contain the desired characteristics of the designed curves or lines. Techniques for curve fitting and design are reviewed and their attributes are described. The blending function methods due to Gordon are discussed and new techniques based on extension of the blending function which provide a greater degree of flexibility for incorporating networks of curves into surface models are described. Paper 10 — "Geometry and Function Definition for Discrete Analysis and Its Relationship to the Design Data Base," by H.A. Kamel and M.W. McCabe, University of Arizona, Tucson, Ariz.

SYNOPSIS—The paper discusses surface definition algorithms as used for structural analysis. The GIFTS 4 structural analysis system is described, with emphasis on definition of various curves, surface "patches," solid "chunks" and specification of loading.

Paper 11—"The Use of Conformal Mapping Techniques for Hull-Surface Definition," by D. Hoffman and T.E. Zielinski, Webb Institute of Naval Architecture, Glen Cove, Long Island, N.Y. SYNOPSIS — The paper will elaborate on conformal mapping techniques and define the limits of its practical use at the various stages of ship design and production. Mathematical principles of conformal mapping will be illustrated for various cases. Application to ship design will be discussed and recommendations for use of the technique and ideas for future application will be presented. Paper 12—"Interactive Fairing of Ship Lines—A Procedure Developed for the Model Manufacture at the Hamburg Model Basin," by G. Collatz and E. Seiffert, Hamburg Model Basin, Hamburg, West Germany.

SYNOPSIS—A description of lines fairing and model construction from preliminary lines drawings submitted by clients. Details of procedures and hardware are provided, plus the role of the draftsman in fairing and in modifications based on results of model tests.

Paper 13—"New Lines System —Its Concept and Application," by E. Tokumaru, Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard, Japan.

SYNOPSIS—A report on several years' experience in ship design and construction with the New Lines System. The paper will discuss fairing logic and a systematic analysis of total man-andmachine lines works.

Paper 14—"Mathematical Ship Lines: What Do They Mean?" by P. Rawat, Hydronautics, Laurel, Md.

SYNOPSIS — A reformulation of the ship surface definition problem is proposed, based on relevant mathematical theory, experience in developing ship surface definition computer programs and experience in using these programs.

Mathematical techniques for reformulation will be discussed.

The registration fee for the symposium will be $50 after August 15, 1977, and late registrants may also register at the Registration Desk.

Make checks payable to SCAHD '77, and mail to Nathan R. Fuller Jr., SCAHD '77, Box 2435, Falls Church, Va. 22042, USA.