Yacht Design General Principles

FOREWORD
When this book was first published, we received many comments and suggestions from interested readers, and we have tried to incorporate these valuable recommendations as much as possible in the second edition. The most significant change in the second edition is the addition of more information regarding motorboats. Although the book primarily focuses on sailing yachts, many motorboat enthusiasts found it interesting and requested more information on this area. We have tried to achieve this in the new edition. This edition includes a completely new section on high-speed hydrodynamics specifically for motorboats, and the sizing section has been expanded to consider both types of yachts. Since a large part of the other sections is also applicable to motorboats, we are confident that motorboat designers and owners will find this book beneficial.
Another important change is the updating of information regarding international standards. ISO/TC188, Working Group 22, presented its work for the seaworthiness of sailing boats between 6m and 24m. Unlike what was presented in the first edition of the book, the new approach is described here with the permission of the chairman, Andrew Blyth. ISO/TC Working Group 18, dealing with sizing, could not reach a final decision, but with the permission of the chairman, Mr. Fritz Hartz, the main ideas have been included in the updated section on sizing. Previously, this section was entirely dedicated to ABS rules.
Minor changes and corrections have been made throughout the book, and for clarity, the original section on boat structure has been divided into two: one dealing with loads and the other with materials.
We would like to express our gratitude to all readers who took the time to point out desired improvements. Special thanks (in alphabetical order) to H Barkla, B Beck, P K Coles, G Dyne, F Eldridge, G Heyman, H Liljenberg, N Newland, P Schwarzel, and C Voghera.
Lars Larsson & Rolf E Eliasson Gothenburg 1999
Translator's Foreword
The rapidly increasing demand for pleasure boats worldwide is making the yacht building industry a significant sector. The Turkish yacht building industry has entered a development trend and is progressing towards becoming a brand. Errors arising from hull form, layout, and materials in yacht production lead to negative outcomes in crucial boat parameters such as overall performance, stability, and strength. For yacht designers and manufacturers to produce according to international standards and to gain a significant share in the global market, a good understanding of the fundamental principles of yacht design is essential. This book, translated into Turkish, is one of the most important yacht design books. It will serve as an important resource for sailing and motor yacht designers, manufacturers, and students in the shipbuilding and marine departments of our universities.
I would like to thank all my colleagues and students who contributed to the preparation of this book.
Assoc. Prof. Dr. Tamer Yılmaz
Istanbul
2006

CONTENTS
Introduction
Design Method Design spiral
Computer-aided design (CAD)
Preliminary Considerations Selection of hull type Intended use Main dimensions Cost
Checklist of important considerations Checklist for YD-40
Hull Geometry Definitions
Lines drawing Tools Work plan
Computer-aided yacht design
Hydrostatics and Stability Calculation of areas
Wetted surface Displacement Center of buoyancy Waterline area
Transverse and longitudinal stability at small angles
Transverse stability at large angles of heel
Static stability curve Rolling
Effect of waves on the righting moment
Stability statistics
Seaworthiness assessment
Hull Design
Forces and moments acting on a sailing yacht
Resistance components
Viscous resistance, basic concepts
Frictional resistance
Viscous pressure resistance
Roughness
Wave resistance, basic concepts
Effect of hull shape on wave resistance
Heel resistance
Added resistance in waves
Other nautical aspects
Hull statistics
Keel and Rudder Design
Flow around a foil
Definition of keel form
Classical foil theory Tip shape
Advanced form design
Evaluation of some form concepts
Section definition
Three useful NACA sections
Effect of shape on section characteristics
Some practical results regarding section shapes
Effect of deviation from theoretical section shape
Advanced section design
Keel and rudder area statistics
YD-40
Sail and Rig Design
Flow around the sail Form plan
Sail camber Mast interaction
Methods to reduce mast-induced distortions
Streamlining
A practical model for sail and rig aerodynamics
Sail statistics
Balance
Effect of heel Good balance
Center of effort of underwater hull Center of effort of sails
Lid
Rudder balance
Propeller and Engine
Resistance in calm and rough weather
Propeller characteristics
Design of an optimum propeller
Performance of a non-optimal propeller
Blade area control
Propeller resistance
High-Speed Hydrodynamics Planing
Chine lift
Forces on a planing boat
Spray rails, stepped bottoms, and stern flaps
Dynamic stability
Alternative propulsion systems
An example
Rig Construction
Definitions and scope of the standard
Forces on the shrouds
Forces on the stays
Comparison of wire and rod
Transverse mast stiffness
Longitudinal mast stiffness
Fractional masthead
Boom
Spreaders
Holes in the mast
YD-40 rigging
Hull Structure
Concepts in structural mechanics General loads
Local hydrostatic loads Local hydrodynamic loads Transverse load distribution Local deformations Forces from the keel Grounding forces Rudder forces Summary of loads
Materials Glass reinforcement Wet lay-up Fatigue
Exotic laminates Sandwich
Typical sandwich buckling Sandwich bending Sandwich in practice Final considerations
Calculation of Abstraction Structure of ISO Standard Hull definitions .
Base laminate
Design loads for the bottom
Design loads for the topsides
Design loads for decks and bulkheads
Design loads for interior parts
Longitudinal impact distribution factor
Area reduction factor
Panel calculation
Stiffener calculation
Rudder stock
Chainplate and keel bolts Sandwich construction
Sizing of YD-40
Arrangement
General space requirements Accommodation Deck layout
Overrun Assessment Dimensionless parameters
Velocity Prediction Program (VPP)
Towing tank test
Computational Fluid Dynamics (CFD)
Main dimensions of YD-40
Weight calculation
STIX calculation