The Collaborative International Dictionary of English v.0.48:

Ribband \Rib"band`\, n. [Rib + band.] [Written also riband, and
   ribbon.] (Shipbuilding)
   A long, narrow strip of timber bent and bolted longitudinally
   to the ribs of a vessel, to hold them in position, and give
   rigidity to the framework.
   [1913 Webster]

   Rib-band lines, oblique longitudinal sections of the hull
      of a vessel. --Knight.
      [1913 Webster]