This book was written primarily for students of forestry to whom
a knowledge of the technical properties of wood is essential.
The mechanics involved is reduced to the simplest terms and
without reference to higher mathematics, with which the students
rarely are familiar. The intention throughout has been to avoid
all unnecessarily technical language and descriptions, thereby
making the subject-matter readily available to every one
interested in wood.
Part I is devoted to a discussion of the mechanical properties
of wood—the relation of wood material to stresses and strains.
Much of the subject-matter is merely elementary mechanics of
materials in general, though written with reference to wood in
particular. Numerous tables are included, showing the various
strength values of many of the more important American woods.
Part II deals with the factors affecting the mechanical
properties of wood. This is a subject of interest to all who are
concerned in the rational use of wood, and to the forester it
also, by retrospection, suggests ways and means of regulating
his forest product through control of the conditions of
production. Attempt has been made, in the light of all data at
hand, to answer many moot questions, such as the effect on the
quality of wood of rate of growth, season of cutting, heartwood
and sapwood, locality of growth, weight, water content,
steaming, and defects.
Part III describes methods of timber testing. They are for the
most part those followed by the U.S. Forest Service. In schools
equipped with the necessary machinery the instructions will
serve to direct the tests; in others a study of the text with
reference to the illustrations should give an adequate
conception of the methods employed in this most important line
of research.
The appendix contains a copy of the working plan followed by the
U.S. Forest Service in the extensive investigations covering the
mechanical properties of the woods grown in the United States.
It contains many valuable suggestions for the independent
investigator. In addition four tables of strength values for
structural timbers, both green and air-seasoned, are included.
The relation of the stresses developed in different structural
forms to those developed in the small clear specimens is given.
In the bibliography attempt was made to list all of the
important publications and articles on the mechanical properties
of wood, and timber testing. While admittedly incomplete, it
should prove of assistance to the student who desires a fuller
knowledge of the subject than is presented here.
The writer is indebted to the U.S. Forest Service for nearly all
of his tables and photographs as well as many of the data upon
which the book is based, since only the Government is able to
conduct the extensive investigations essential to a thorough
understanding of the subject. More than eighty thousand tests
have been made at the Madison laboratory alone, and the work is
far from completion.
The writer also acknowledges his indebtedness to Mr. Emanuel
Fritz, M.E., M.F., for many helpful suggestions in the
preparation of Part I; and especially to Mr. Harry Donald
Tiemann, M.E., M.F., engineer in charge of Timber Physics at the
Government Forest Products Laboratory, Madison, Wisconsin, for
careful revision of the entire manuscript.
SAMUEL J. RECORD.
YALE FOREST SCHOOL, July 1, 1914.
