Shrinkage-related degrade and its association with some physical properties in Eucalyptus regnans F. Muell |
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Authors: | J Ilic |
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Institution: | (1) CSIRO, Forestry and Forest Products, Private Bag 10, Clayton South MDC, Vic. 3169, Australia, AU |
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Abstract: | Summary Assessments of internal checking and the physical properties of 124 trees of Eucalyptus regnans F. Muell. have shown that for material dried under relatively mild predryer conditions (30 °C, 65% RH) internal checking
was highly positively correlated with each of collapse, moisture content and normal shrinkage, and weakly negatively correlated
with total external shrinkage. Collapse alone explained 47% of the variation in internal checking. Incidence of internal checking
in sample boards could be estimated with moderate success by each of the following properties measured on board ends: collapse,
the number of internal checks and initial moisture content. Material with high mean basic density above 530 kg/m3 was associated with low levels of internal checking and collapse. However, the maximum naturally occurring density of E. regnans was not high enough to obviate collapse and internal checking. It was observed that growth rings in 100 × 50 mm backsawn
boards in which the earlywood air-dry density was below 450 kg/m3 showed internal checking. The size and number of internal checks increased with a decrease in earlywood density. It was shown
that drying E. regnans below temperatures of 24–30 °C does not eliminate collapse, thus raising doubt about the validity of a temperature threshold
concept in that range.
Received 17 September 1997 |
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