This paper describes a Bonjeans/Hydrostatics Program for Irregular Shaped Hulls such as catamarans, drill ships, and other exotic shapes. The user defines the hull at each station by a series of straight lines and circular arcs. From this hull definition the- B6njeansProgram computes area and area moments at zero and three degree heel. Tins allows the Hydrostatic Program to perform all calculations involving water plane area independent of half-breadth values.

The flexibility of this program allows hydrostatic properties to be computed for a wide range of forms previously unworkable. To my knowledge, its capability is unique in the industry and can replace repetitive manual calculations with a quick and reliable computerized method.


The incapability to perform Bonjean/Hydrostatics calculations on hull forms with a non-traditional shape such as catamarans, drill rigs, vessels with drill wells or tunnel sterns became apparently the Computer Branch, Maritime Administration, Office of Ship Construction, several years ago. At that time hydrostatic calculations for irregular hull. forms had to be carried out by hand. However, two programs in our Hull Scientific Program Package pointed to the capability of performing hydrostatic calculations on any hull form which could be defined as a series of straight lines and circular arcs.

The Maraud Bo jeans! Hydrostatics Program provided the format for hull form definition and arrangement of Bo jeans data for mass storage. The MarAd Cross Curves of Stability Program provided the routines for computation of station areas and moments at any degree of heel. By relying on station areas and area moments to define water plane properties, the Hydrostatics Program described here can operate independent of half breadth values. This bypasses the difficulty of defining exotic water planes in a point by point manner prior to finding their areas and centers. Development of the program was contracted to CADCOM, Inc. of Annapolis, Maryland who, in addition, developed a subroutine to calculate area and moments for arbitrarily defined shapes. They also provided a method for the treatment of longitudinal discontinuities (breakpoints such as wells, platform supports etc.) to accommodate Simpson's Rule. Final debugging of the program and documentation for public distribution is now complete and can be obtained by writing: Maritime Administration, Computer Branch, ode 724, Washington, D. C. 20235.

This paper treats the input and output of the Bo jeans! Hydrostatics Program with the Appendix devoted to definitions of the hydrostatic values. A semi-submersible drill rig has been used for illustrating the program, and the resultant hydrostatic values are compared with the independent naval architect's computations.

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