Studies on the utilisation of dominant 20-year-old plantation-grown trees of Eucalyptus nitens.  R. J. McKimm, G. Waugh and R. L. Northway.  December 1985.  33 pp. (unpubl.)

SUMMARY

This report describes a study of the utilisation of 20-year-old plantation-grown dominant Eucalyptus nitens Maiden (shining gum) trees, for the production of structural and appearance products. Log characteristics were examined and measurements made of peripheral longitudinal strain, basic density and mechanical strength characteristics of sawn timber from these trees. Four drying techniques (predrying and conventional kiln drying, air drying and conventional kiln drying, air drying and high temperature kiln drying, and progressive kiln drying; all techniques being followed with a reconditioning treatment) were applied to 25 mm and 50 mm thick back- and quarter-sawn products. Measurements for twist, spring, bow, width and thickness were made on the 50 mm boards before and after seasoning, and all boards were machined and graded to Australian Standard (AS) 2082.

The logs contained a high proportion of sapwood and the basic density of the wood was lower than that reported for heartwood of mature E. nitens, though the moduli of rupture and elasticity, and crushing strength were comparable.

The method of sawing only influenced the amount of bow in freshly sawn products. In dried products bow was reduced but twist significantly increased when the wood was quarter-sawn. Spring also increased in drying irrespective of the method of sawing.

Drying method had little effect on distortion, though progressive kiln drying induced more twist than any other treatment. Shrinkage, both radial and tangential, was also independent of the drying method and resembled that in heartwood of mature E. nitens.

Twist, spring and bow in the freshly sawn timber and in dried timber after reconditioning, were within the permissible limits prescribed in the Australian Standards.

Knots were the most common cause for the downgrading of sawn structural and appearance products. Rejection rates were 37% for structural products and in excess of 50% for appearance grade products.

Also published:

McKimm, R.J. (1985)  Characteristics of the wood of young fast-grown trees of Eucalyptus nitens Maiden with special reference to provenance variation. 1. Variations in growth, strain and density associated with provenance.  Aust. For. Res. 15:207-18.

McKimm, R.J. (1985)  Characteristics of the wood of young fast-grown trees of Eucalyptus nitens Maiden with special reference to provenance variation. II. Strength, dimensional stability and preservation characteristics.  Aust. For. Res. 15:219-34.

McKimm, R.J. and Ilic, Y. (1987)  Characteristics of the wood of young fast-grown trees of Eucalyptus nitens Maiden with special reference to provenance variation. III. Anatomical and physical characteristics.  Aust. For. Res. 17:19-28.