Mathematical representations of hull surface shape have largely supplanted graphical fairing and lofting of lines in the shipbuilding and aircraft industries, but have had little application so far to small craft. Past methods of hull design are surveyed to put mathematical design into historical perspective and point up its many advantages. The basic concepts of analytic geometry of surfaces needed for yacht hull design are briefly introduced with references. Several special aspects of the geometry of yacht hulls, arising from considerations of aesthetics, hydrodynamics, and construction methods are discussed and cast into analytic form for inclusion in a hull design scheme. The paper explains in detail a particular representation system called FAIRLINE/1, simple enough to fit into the program and memory limitations of a TI-59 calculator, yet extremely versatile. A program listing and several example hull designs created with this program are presented.