# Yacht Design School
- Lesson 2b

**
Preliminary Design
– Ratios, Coefficients, Feasibility & Midsection Development**

*
Revised 03/30/2015
– Copyright 2015*

## 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

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