New Zealand Journal of Forestry (1974) 19(2): 246–263
©New Zealand Institute of Forestry
Utilization of New Zealand-grown eucalypts for sawn timber and veneer
J.A. Kininmonth , D.H. Revell and D.H. Williams
Thirteen shipments each comprising between 1 and 16 trees of 25 to 60-year-old Eucalyptus regnans, E. obliqua, E. fastigata, E. delegatensis, E. saligna, E. botryoides, E. muellerana, or E. pilularis were sawn. Part or all of the sawn output was dried and, after seasoning, physical properties and degrade assessed. Information was obtained on the machining properties of the wood and some observations made on end use.
Sawn and grade recovery of three shipments was studied. E. fastigata from a 36-year-old stand gave a sawn recovery of only 41% in a circular mill and demonstrated that, as log size increases, the percentage of clear or dressing grade boards increases and the problems from relief of growth stresses decrease. Twenty-eight-year-old E. saligna yielded 44% and 56-year-old E. delegatensis 55%) in a band mill. End splitting of logs was worst in the E. saligna and was a major source of loss, particularly when logs were flat sawn. In both E. saligna and E. delegatensis there was a marked decline in grade recovery above the butt log.
Kiln drying from green was unsatisfactory but all eight species dried rapidly when air dried in commercial or small-scale stacks down to 30% m.c. and finished in a kiln. Drying was much faster than for similar groups of hardwoods such as red and hard beech (Nothofagus fusca and N.
Surface and internal checking caused by collapse was a significant cause of degrade in E. delegatensis, and was not eliminated by reconditioning in these tests. Other species, more particularly the ash group, also collapsed during drying but recovered well after reconditioning and very rarely developed checks. Other forms of checking that develop if drying conditions are too severe were minimized by close stacking and were never a serious cause of degrade. None of the timbers warped seriously and the worst spring and bow encountered was the result of relief of growth stresses during sawing rather than seasoning.
Shrinkage values were similar to Australian figures. Average density of the dry timber was lower than for old-growth Australian material but similar to re-growth. The ash group had average density of 520 to 660 kg/m3 and so might be more acceptable for furniture and related products than the other species, which averaged about 700 kg/m3. In the latter species, however, short rotations and fast growth could possibly reduce the density.
End use studies indicate that these species are capable of producing material suitable for furniture, turnery, and other long-length uses such as mouldings and flooring. Sliced veneer of excellent quality has been marketed.