New: ShipGen for hull form generation in PC
Published in Fairplay Magazine

ShipGen , a PC based powerful tool for the automatic generation of hull form has been launched recently by Defcar Eng. (, a technical office specialised in CAD/CAM development for shipdesign and shipbuilding.

Many shipyards are using the CAD/CAM solutions of Defcar Eng. for its design and production processes. From ship project to numerical control cutting, the Defcar systems cover all aspects of the shipbuilding industry. However, there was a demand from the clients of a software for make easily and quickly their accomplishment of tenders, which included a critical phase that is the hullform design. ShipGen is the result of that demand.

ShipGen is intended for shipdesigners. The software generates the whole surfaces of the ship, in accordance  with the requirements previously defined, i.e., dimensions, geometry and hydrostatics characteristics. The program incorporates a small naval architecture calculations integrated module and has a dynamic connection with the Excel spreadsheet to which transmits in every modification of the lines the hydrostatic data of the new vessel. This feature allows the designer to write in Excel the code of his own models of project optimisation and feed them dynamically using the data received from ShipGen, thus closing up the iterative designing process.

Bulb transformations. Note the smoothness of the surface transition to the fore body.

ShipGen uses a handful of basic ships perfectly faired and identified by their Bezier´s surfaces to generate the lines. Starting from this base, ShipGen makes up to 14 transformations from a lengthening to a modification of the trim and the raise of floor. The power of the system allows to obtain lines far different from the initial ones. As an extreme case, it can obtain the forms of a cargoship starting from a sterntrawler, although for this case it is recommended to use the lines of cargoships included in the system. The lines generated by ShipGen are always faired provided the transformation is not extreme.

The most complex transformation the system can do is the change of the position of the LCB by keeping constant the ship´s displacement, the main dimensions, the main section and, in general, the ship geometry except the fore and aft bodies. In this modification, the designer tells the program to adjust the lines to shift forward or aft the LCB a given magnitude, without any change except the fore and aft bodies. Depending on the magnitude of such modification, ShipGen can need up to one minute in finding the new lines. Another possibility of the system of similar complexity is to change the displacement by keeping the position of the LCB.
Once the lines have been obtained, ShipGen can transfer them to other systems by means of DXF files or IGES format, in addition to the proper DEFCAR system. In case of IGES files the system transfers the generated lines as NURBS surfaces. This allows those users with systems which receive this types of files (like Tribon, AutoShip, MaxSurf...) to continue the process of design or production of the ship.

The newness of ShipGen is that the user controls the shape of the hull by numbers: he enters the desired geometrical characteristics or hydrostatics coefficients and ShipGen iterates to find the hull form which fits the requirements.

Cintranaval-Defcar S.L.
Lauroeta Etorbidea, 4 48180 Loiu, Bizkaia (Spain)
Tlf: +34 902158081
Fax: +34 944638552