Investigation of wood properties that influence the final moisture content of air-dried sugi (Cryptomeria japonica) using principal component regression analysis
Sugi (Cryptomeria japonica D. Don) lumber is known to have a large variability in final moisture content (MCf) and is difficult to dry. This study investigated the variability in MCf of sugi in relation to wood properties. The wood property variables included initial moisture content (MCi), basic density (BD), annual ring orientation (ARO), annual ring width (ARW), heartwood ratio (HR) and CIE L* color (L*). Sugi samples were cut from flat-sawn lumbers and air-dried; a principal component regression (PCR) model for predicting MCf was developed with the wood property variables. The wood properties that contributed to the prediction of MCf were evaluated by PCR analysis. Significant positive regression coefficients of the PCR model were observed in the MCi, BD, ARO and HR, whereas negative ones in the L*. There were no significant regression coefficients in the ARW. These results suggest that the MCi, BD, ARO and HR had a positive influence, the L* had a negative influence, and the ARW had little influence on the MCf of air-dried sugi wood. This finding is in line with the general view on the drying characteristics in relation to these wood properties.
Effect of radial origin on final moisture content and gradient, casehardening, cracking and deformations of dried Siberian larch (Larix sibirica) timber
Siberian larch (Larix sibirica Ledeb.) timber is a good raw material, particularly for the carpentry industry. However, in the radial direction varying wood properties, like density, may have an effect on the drying quality of sawn larch timber. Thus, final moisture content (MC), MC gradient, casehardening, cracking and deformations were studied according to radial origins, taking into account the orientation of annual rings. The effect of radial origin on MC properties was mainly caused by the differences in the basic density between different radial locations. Differing ring orientation between planks of different radial origin most probably affected the MC gradient. As casehardening and deformations had clear trends in radial direction, differences in them may be largely caused by MC differences. Thus including larch timber of similar density and ring orientation in the same drying lot would help achieve larch timber of uniform drying quality.ZusammenfassungSibirische Lärche (Larix sibirica Ledeb.) ist ein sehr guter Rohstoff insbesondere für den Holzbau. Allerdings können die in radialer Richtung variierenden Holzeigenschaften, wie zum Beispiel die Dichte, einen Einfluss auf die Trocknungsqualität von Lärchenschnittholz haben. Deshalb wurden der Einfluss der Lage im Stammquerschnitt und der Jahrringverlauf auf die Endfeuchte (MC), den Feuchtegradienten, die Verschalung, die Rissbildung und die Verformungen untersucht. Der Einfluss der Lage auf die Feuchteeigenschaften ist hauptsächlich auf Unterschiede in der Rohdichte in radialer Richtung zurückzuführen. Unterschiedlicher Jahrringverlauf im Schnittholz hatte höchstwahrscheinlich einen Einfluss auf den Feuchtegradienten. Da sich bei der Verschalung und den Verformungen ein klarer Trend in radialer Richtung zeigte, dürften die Unterschiede zu einem großen Teil auf die Holzfeuchteunterschiede zurückzuführen sein. Daraus folgt, dass Lärchenschnittholz mit einheitlicher Trocknungsqualität erzeugt werden könnte, wenn das Holz einer Trocknungscharge ähnliche Rohdichte und ähnlichen Jahrringverlauf aufweisen würde.
Variation in Permeability and Treatability in Shortleaf Pine and Yellow Poplar
Superficial gas permeability determinations were made for longitudinal, radial, and tangential flow on samples removed from different heights, radii, and distances along the radii in a young and a mature shortleaf pine ( Pinus echinata Mill.) and in a yellow poplar ( Liriodendron tulipifera L.). Permeability was measured at a mean pressure of 2.2 atmospheres and the wood was maintained at about 18% moisture content. Some of the samples were then pressure-treated with creosote under controlled conditions to estimate treatability. Specific gravity and latewood per cent were also determined. In the young pine, position in the tree showed no effect on permeability, whereas in the mature pine a slight increase with height and a sharp increase with distance from the pith were detected. In yellow poplar, an increase of permeability with distance outwards along the radius was detected, but no consistent height change. Treatability, particularly retention, was moderately correlated with permeability, particularly in shortleaf pine. In yellow poplar, inclusion of permeability values for all three structural directions was necessary to obtain correlation. All relationships were improved by transforming the permeability logarithmically. Specific gravity and latewood relationships with permeability were conflicting. Use of a mean pressure higher than atmospheric appeared to be advantageous in permeability determinations.