A shell expansion drawing may be created from any workshop design. The drawing shows the girth positions of all parts (plate edges, stringers, frames and decks) from a specified datum position (usually, but not always, the baseline).

 View a video showing how to create a Shell Expansion drawing in Workshop.

Before generating the shell expansion drawing, the model must be set up correctly.  The shell expansion drawing is generated by calculating the girth distance around the surface of the vessel from the baseline to the part.  Hence it is important that all “superfluous” surfaces be either set to “internal use” or made invisible so they are not included in the girth calculations.  Surfaces normally switched off during the shell expansion calculations include the superstructure surfaces, tank boundaries, railings etc.  Surfaces that are normally on include the hull surfaces, any chine surfaces and the main decks.  Normally the trimming is also turned on prior to a shell expansion so that the trimmed sections of the surface are not included in the girth calculations.

Once the model is set up correctly the shell expansion drawing can be generated by choosing Calc Shell Expansion from the Plate menu.

To change the datum about which the contours are expanded go to Display | Structure and specify the datum in the bottom right of the Structure Visibility dialog that appears. If the datum is a waterline or a buttock line then you will need to enter a value. For example if you wish to expand the shell about a buttock line 1.0 m from the centreline, you will need to select ButtockLine and enter the 1.0 m value in the Value field.

Go to Shell Expansion View on page 78 for information on how to display Shell Expansion drawings.