Parametric Design
I have found that the easiest way of producing a preliminary design for yachts is to create a metric of "performance." This metric is based on a parametric analysis of sailboats which incorporates various ratios of performance. By using this metric, an artificial scale from 0 to 10 is created (0 being unrealistically fast, and 10 being a barge). With inputs of a design waterline and a scale, a basic hull form can be created. The spreadsheet can be found here. Please note that it is a work in progress, and there are many bugs. Furthermore, the spreadsheet is stable for waterlines in the range of 20ft to about 100ft. All units are in english standard.