A Forest Sampling Method for Wood Strength

Estimates of average and near-minimum mechanical property values of clear straight-grained wood are essential in the development of engineering properties for structural use. To make safe and efficient use of the timber resource, it is important that these estimates be unbiased and that their reliability is measurable. In this paper five criteria are generated to judge methods for sampling clear straight- grained wood from the forest. Direct random sampling, double sampling, and the “cruciform” method of sampling are compared against these criteria. The cruciform method meets none of five criteria while double sampling satisfies two. In the cruciform and double sampling methods, subjectivity in sample selection permits bias. A detailed discussion is given of the factors involved in planning, and conducting a random experiment for evaluating timber properties. Points discussed are: 1) an objective method for setting sample size 2) a method for attaining randomness in the sample collection, and 3) a discussion of methods for studying mechanical property distributions and for calculating near-minimum percentage points of normal and non-normal distributions.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member