There are two fundamentally different approaches to modeling a hull with NURBS surfaces:
1. Construct curves that define the hull (edges, sections) and then loft a surface through them. You can download a nice tutorial on how to do that here (
http://www.orca3d.com/download/Surface_from_Curves.pdf). It was written by Scott Davidson at Robert McNeel & Associates, the Rhino developers. In this approach, you design the curves, and the surface results from the curves.
2. Directly manipulate the control points on the surface, and have Orca compute the sections. In this approach, you design the surface, and curves result from the surface. This is our favored approach, as it’s easier to create a fair surface. On the other hand, it’s harder to match existing offsets. You can read a tutorial for this approach in the Orca Help, in the “A Hull Design” section of the Quick Start Tutorials chapter. The tutorial begins by using a Hull Assistant, but it could also be done by beginning with a simple, flat surface, and then moving the control points.
Other resources that you might find helpful: