Yacht Design School - Lesson 2b

Preliminary Design – Ratios, Coefficients, Feasibility & Midsection Development


Revised 05/27/2020 – Copyright 2020


Books To Be Read With This Lesson

Understanding Boat Design by Ted Brewer

Preliminary Design of Boats and Ships by Cyrus Hamlin

Minimum Tools for This Lesson if Using Computer Assisted Design

            Rhinoceros® (commonly known as Rhino) Version 4.0 or later


What You Will Receive With This Lesson

See drawings from Lesson Two A


What You Will Learn In This Lesson

Choosing the Speed to Length Ratio

Hull Speed

Choosing Prismatic Coefficient

Choosing the Displacement to Length Ratio

Midsection Development Principles

Plaining Saile and Power Boats

Defining the Midsection – By the Visual Method

Defining the Midsection – Using Prismatic Coefficient and Displacement to Length Ratio

Relating the Midsection and Lines Development

First Trial on Scantlings

First Trial on Ballast

First Trial on Sail Area and Engine Horsepower

Laws of Mechanical Similitude

Useful Proportional Ratios

Appendix A: References and Discussion Points for Prismatic Coefficient

Appendix B: Concept Design Spreadsheet Templates