Processing and material properties of Tasmanian yellow gum, Eucalyptus johnstonii

Summary

Boards of native forest Tasmanian yellow gum (Eucalyptus johnstonii) were processed using current commercial best practice. Boards were evaluated before and after processing to determine parameters such as board shrinkage, appearance grade and drying degrade. Bending strength and stiffness were determined by standard tests on thirty small clear sections, while Janka hardness was measured at two points on each of ten specimens. Yellow gum boards proved prone to collapse shrinkage and distortion on drying. The results showed that the species produces much denser, stronger and harder timber than the Tasmanian oak group of eucalypts, with seasoned strength rating according to Australian Standards of strength group SD2 (compared with SD4 for the species group) and mean Janka hardness 10.9 kN (compared to 6.1 kN).

Keywords:

• wood properties
• quality
• density
• shrinkage
• collapse (drying)
• checks
• wood defects
• moisture content
• wood strength
• Eucalyptus johnstonii