Estimating Air Drying Times of Small-Diameter Ponderosa Pine and Douglas-Fir Logs;Forest Service research paper

摘要

Because dense stands of softwood trees are causing forest health problems in the western United States, new ways to use this material need to be found. One option is to use this material as logs rather than sawing it into lumber. For many applications, logs require some degree of drying. Even though these logs may be considered small diameter, they are large compared with the thickness of typical lumber, and they may require uneconomically long kiln drying times. Air drying is a logical alternative to kiln drying, but the variables involved make estimating air drying times difficult. In this study we developed experimental air drying time data for 4- to 8-in.- (102 to 203-mm-) diameter ponderosa pine and Douglas-fir debarked logs stacked at four different times of the year. These data were used to develop multiple linear and nonlinear regression models that relate daily moisture content loss to moisture content at the start of the day, average daily temperature and relative humidity, and log diameter. The models provide a way to calculate estimated air drying times for logs stacked at any time of the year and at any location where historic weather data is available. It also provides a way estimate the benefit of simple, low-cost dryers in reducing drying time.