Surveying Fiberglass Power Boats
by David Pascoe
Hull and Its Structures
5. Hull and Its Structures 89
Essentials of Composites 90
Laying Process 90
Solid Laminates 90
Molding Hulls 91
Laying in Cores 93
Structural Properties of Laminates 94
Solid Laminates 95
Cored Laminates 96
Basic Structural Principles 99
Shape Affects Strength 99
Design Elements 100
Internal Structural Materials 108
Examples of Structural Design Defects 110
Stringer Design Error 111
Bulkhead Failure 111
Common Structural Failures 113
Stress Cracking in Superstructures 114
Hull Stress Cracking 116
Structural Weakness 117
Bottom Strakes 118
Primary Symptoms 125
Cored Hulls 127
Foam Cores 128
Bulkhead Installation with Foam Cores 133
Water Ingress 133
Other Core Types 136
Putty or Spray Cores 136
Why Design Faults Occur 139
An Embarrassing Example 141
Marketing and Price Pressures 141
Excerpt: Chapter 5
This chapter was written from the standpoint of both pre purchase surveys and conducting failure analysis, this because one function inevitably grows out of the other; we find a defect and we are asked, or want to know, what the cause is.
As I pointed out in the Introduction, boat design and materials has changed radically in recent years.
The reader should be cognizant of the fact that it takes time to discover whether new materials, design and methodology prove successful.
The efficacy of the most recent introductions therefore is unknown and cannot be covered herein.
In treating the subject of basic construction and how to conduct a survey, I have broken it down into two sections in three chapters - The Hull and Its Structures, Surveying the Hull, and Using Moisture Meters.
Each of these deals with a separate but interdependent subject which be considered as a whole. Because a hull is a more or less unified structure, all aspects are inter-related.
This presented me with the problem of how to deal with each without resulting in substantial repetition of the discussion.
Ultimately, it turned out that some overlap and repetition was unavoidable since I wanted to organize each chapter so that each would stand on its own.
In order to survey a hull, a surveyor needs to have a basic understanding of the engineering principles involved.
This does not mean that the surveyor himself must be an engineer, for many of the people who design and build boats are not themselves engineers or naval architects.
This chapter will review basic composite boat building and structural principles in considerable detail in order to provide the prospective surveyor with a solid foundation that will assist him in recognizing some of the many structural faults that he will be faced with.
The reader is also reminded that this book attempts to cover a wide range of boats both small and large, old and new, with a wide range of materials, design and techniques. Thus does the surveyor's knowledge have to cover the range of many decades. This, of course, is not easy but will shed light on why I go to such detail in a book on surveying.
Normally, it's not the surveyor's job analyze the structural engineering of vessel upon which he is performing a pre purchase survey. After all, it is a survey that we are doing, not an engineering analysis.
However, as was discussed in Chapter One, it is the surveyor's responsibility to be able to recognize the symptoms of structural faults when they appear.
(Additional spaces are added for easy screen reading.)
- 2nd Edition
by David H. Pascoe
Publisher: D. H. Pascoe & Co., Inc.
David Pascoe - Biography
David Pascoe is a second generation marine surveyor in his family who began his surveying career at age 16 as an apprentice in 1965 as the era of wooden boats was drawing to a close.
Certified by the National Association of Marine Surveyors in 1972, he has conducted over 5,000 pre purchase surveys in addition to having conducted hundreds of boating accident investigations, including fires, sinkings, hull failures and machinery failure analysis.
Over forty years of knowledge and experience are brought to bear in following books. David Pascoe is the author of:
- "Mid Size Power Boats" (2003)
- "Buyers’ Guide to Outboard Boats" (2002)
- "Surveying Fiberglass Power Boats" (2001, 2nd Edition - 2005)
- "Marine Investigations" (2004).
In addition to readers in the United States, boaters and boat industry professionals worldwide from over 70 countries have purchased David Pascoe's books, since introduction of his first book in 2001.
In 2012, David Pascoe has retired from marine surveying business at age 65.