Estimating air-drying times of small-diameter ponderosa pine and Douglas-fir

One potential use for small-diameter ponderosa pine and Douglas-fir timber is in log form. Many potential uses of logs require some degree of drying. Even though these small diameters may be considered small in the forestry context, their size when compared to typical lumber thickness dimensions is large. These logs, however, may require uneconomically long kiln-drying time. Air-drying is a logical alternative to kiln-drying, but the variables involved make estimating air-drying times difficult. In this study, experimental air-drying time data for 4- to 8-inch- (102- to 203-mm-) diameter ponderosa pine and Douglas-fir debarked logs stacked for air-drying at four different times of the year were developed. These data were used to develop multiple linear and nonlinear regression models that relate daily moisture content (MC) loss to MC at the start of the day, average daily temperature and relative humidity, and log diameter. The model provides a way to calculate estimated air-drying times for logs stacked at any time of the year where historic weather data are available.

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