Some solid wood evaluations (including internal checking assessment, shrinkage, collapse and tension tests) were carried out on 15-year-old Eucalyptus nitens (Deane et Maiden) Maiden trees. There were significant differences between the density classes in basic density and moisture content, with the low density class having significantly lower earlywood density than the medium and high density classes. Significant differences were observed between all three classes in average ring density and latewood percentage. The extent of the internal checking observed will present a definite problem to many solid wood products. Collapse occurred readily and could be severe, but steaming effectively restored the collapse. The scanner used gave an accurate and reliable estimate of radial and tangential shrinkage combined. The tension test results were positively correlated with density and moisture content.

Wood properties of Eucalyptus nitens grown in New Zealand.

A New Zealand stand of Eucalyptus nitens (Deane & Maiden) Maiden was pruned up to height 8 m and grown for 15 years at low stocking to 57 cm diameter at breast height. This stand provided 15 trees, preselected for a range of wood density. Lumber and veneer were cut from the 5-m butt logs, veneer was peeled from the second logs from height 7 to 13 m, and each tree was evaluated for production of appearance-grade lumber and rotary-peeled veneer. Butt-log quality was good as pruning had effectively restricted the knotty core, and there was little decay from branches in either butt logs or veneer billets. Longitudinal growth stresses varied widely among trees, resulting in log endsplitting and sawlog flitch movement during sawing (spring), which led to crook in sawn timber, substantially reducing timber conversion in some trees. Collapse and internal checking were prevalent in air-dried lumber, and numbers of checks varied widely among trees. Face-checking was found in boards from all trees after kilndrying and reconditioning, and even those with very few face checks had internal checks. Veneer thickness varied unacceptably, caused probably by incorrect knife- and pressure-bar settings. Veneer splitting also varied among trees, and was worse in butt-log than in second-log veneers. Unsatisfactory pre-heating of billets before peeling may have exacerbated splitting. Knots severely downgraded structural plywood veneer grades, <8% of sheets from the second logs being acceptable compared with 87% of sheets from the pruned butt logs. Stiffness of veneer sheets was successfully measured using a sonic device (Pundit™) to sort veneers for manufacture of laminated veneer lumber.

Processing young plantation-grown eucalyptus nitens for solid-wood products. 1: individual-tree variation in quality and recovery of appearance-grade lumber and veneer

Secado de eucalyptus nitens y globulus y su

Ensayos de secado en madera radial y tangencial de  Eucalyptus  nitens y globulus  fueron realizados en laboratorios de la Universidad del Bio-Bio en el marco del Proyecto FONDEF D98I1018 y posteriormente validados a escala industrial. A escala de laboratorio, la escuadria utilizada fue de 30 mm de espesor, 1.8 m de largo y ancho aleatorio. A escala industrial en tanto, fue de 32 mm de espesor, largos de 2.1 y 2.8 m, con anchos variables. En general, los programas de secado fueron suaves, con temperaturas no superiores a los 50°C, con un bajo potencial de secado e incluyeron tratamientos de vaporizado para recuperar colapso y reducir tensiones de secado. Se evaluaron contenidos de humedad inicial y final, densidad basica, gradientes de humedades, grietas, contracciones, tensiones y alabeos, determinando finalmente su aprovechamiento en pisos, blocks y muebles. Los resultados indican que la madera de  Eucalyptus  nitens  presenta una fuerte evaporacion superficial, generando altos gradientes de humedad, contracciones prematuras a nivel de superficie y tensiones de secado bajo el P.S.F, originando grietas superficiales e internas. Cuando el colapso es severo, debido a la baja resistencia mecanica de la pared celular de la madera, se generan grietas superficiales e internas en la madera. El mejor aprovechamiento se obtuvo para madera radial, donde el  Eucalyptus globulus  registro entre 52 y 81% para blocks, entre 48 y 91% para piso y entre 38 y 89% para muebles. El  Eucalyptus nitens  registro entre 60 y 71% en blocks, entre 59 y 61% para piso y entre 52 y 63% para muebles. La perdida por nudos en  Eucalyptus globulus  fluctuo entre 3 y 22% en madera radial y entre 5 y 24% para madera tangencial. Para  Eucalyptus nitens,  en tanto, fluctuo entre 12 y 19% y entre 15 y 34% para los cortes antes senalados. La perdida por grietas en  Eucalyptus  globulus  vario entre 3 y 10% para madera radial y entre 15 y 21% para tangencial. En el Eucalyptus  nitens  esta fluctuo entre 3 y 13% y entre 5 y 38%. Lo anterior, permite concluir que la madera de corte radial es la mejor opcion para ser utilizada en estas aplicaciones Palabras clave :  Secado;  eucalyptus ; calidad secado; aprovechamiento; evaluacion.

https://dialnet.unirioja.es/descarga/articulo/5335171.pdf

T. Haslett

Papers

Nitens for sawn timber